RRFW Riverwire – Glen Canyon Dam Update November 7, 2012
Current Status
Releases from Glen Canyon Dam are currently averaging approximately 8,020 cubic feet per second (cfs) with fluctuations for hydropower generation between approximately 7,000 cfs (nighttime) and 9,000 cfs (daytime). The reservoir elevation is 3619.2 feet and declining.
On November 18-23, 2012, the Department of Interior will conduct the first High Flow Experiment under a multi-year High Flow Protocol announced earlier this year by Secretary Salazar. Under this Protocol, high flow releases are linked to sediment input and other resource conditions below Glen Canyon Dam.
Beginning on the evening of November 18th, releases from Glen Canyon Dam will begin ramping up to full power plant capacity (approximately 27,300 cfs). At midday on November 19th, bypass tubes at Glen Canyon Dam will be opened and releases will continue to increase up to full power plant and bypass capacity (approximately 42,300 cfs) by the evening of November 19th. Releases will be maintained at peak release for 24 hours and then begin ramping back down. Releases will return to normal operations in the evening of November 23rd. The entire experiment, including ramping is expected to last 5 days, with 24 hours at peak release.
November releases from Glen Canyon Dam prior to and after the High Flow Experiment are expected to fluctuate between 7,000cfs and 9,000cfs. The elevation of Lake Powell is expected to decrease approximately 2 ½ feet during the 5 day experiment. To view the most current reservoir elevation, content, inflow and release, click on: http://www.usbr.gov/uc/water/rsvrs/ops/crsp_40_gc.html
The unregulated inflow volume to Lake Powell in October was 189 thousand acre-feet (kaf) (37% of average). The release volume from Glen Canyon Dam in October was 498 kaf. The end of October elevation and storage of Lake Powell were 3619.5 feet (80.5 feet from full pool) and 13.71 million acre feet (maf) (56.4% of full capacity). The reservoir elevation is now declining.
The water year unregulated inflow volume for 2012 was 4.91maf (45.3% of average), placing the 2012 as the third lowest on record since the closure of Glen Canyon Dam in 1963. In terms of reservoir elevation and storage, Lake Powell reached its peak for water year 2012 on June 3rd at 3636.9 ft (63.1 feet from full pool) and 15.64 maf (64.3% of capacity), respectively.
Releases for Water Year 2012 totaled 9.466 maf. Pursuant to the 2007 Interim Guidelines, Lake Powell operated under the Equalization Tier in 2012, releasing 9.463 maf, which is 8.233 maf plus 1.233 maf (the Equalization release volume from 2011 that could not be achieved by September 30, 2011). Throughout water year 2012, Reclamation adjusted operations of Glen Canyon Dam to release the appropriate annual volume during 2012 to achieve Equalization objectives as practicably as possible by September 30, 2012.
Current Dam Operations
The operating tier for 2013 is the Upper Elevation Balancing Tier, as establish in August 2012 and pursuant to the Interim Guidelines. However, if hydrologic conditions and projections become wetter, it is possible that beginning in April, the Equalization tier will govern the operations of Lake Powell for the remainder of the water year. Based on analysis of a range of inflow scenarios, the current probability of realizing an inflow volume that would trigger Equalization in 2013 is approximately 20 percent. As hydrologic conditions for Lake Powell and Lake Mead change throughout the year, Reclamation will adjust operations of Glen Canyon Dam to release the appropriate annual volume during 2013 to achieve the governing operating tier objectives as practicably as possible by September 30, 2013.
Releases from Glen Canyon Dam in November in the days prior to and after the High Flow Experiment on November 18-23 will be approximately 8,020 cfs with daily fluctuations between 7,000cfs and 9,000cfs and are consistent with the Glen Canyon Operating Criteria (Federal Register, Volume 62, No. 41, March 3, 1997). The scheduled release volume for November, including the High Flow Experiment, is 724 kaf.
In December, the release volume will likely be about 800 kaf, with fluctuations throughout the day from about 8,250 cfs in the early morning to about 16,250 cfs in the early evening. In January, the release volume will likely be about 800 kaf with daily fluctuations for hydropower.
In addition to daily scheduled fluctuations for power generation, the instantaneous releases from Glen Canyon Dam may also fluctuate to provide 40 Megawatts (MW) of system regulation. These instantaneous release adjustments stabilize the electrical generation and transmission system and translate to a range of about 1,100 cfs above or below the hourly scheduled release rate. Typically, fluctuations for system regulation are very short lived and balance out over the hour and do not have noticeable impacts on downstream river flow conditions.
Releases from Glen Canyon Dam can also fluctuate beyond scheduled fluctuations for power generation when called upon as a partner that shares reserve requirements within the electrical generator community (i.e. balancing area). To provide system reliability, all participating electricity generators within the balancing area maintain a specified level of generation capacity (i.e. reserves) that can be called upon when an unscheduled outage occurs. Glen Canyon Dam typically maintains 43 MW of reserves (approximately 1,100 cfs) for this purpose. Reserve calls can be maintained for a maximum of 2 hours after which time the generation rate should be returned to the original schedule. If reserves from Glen Canyon Dam are called upon, releases from the dam can exceed scheduled levels and can have a noticeable impact on the river downstream from Glen Canyon Dam. Calls for reserves are fairly infrequent and typically are for much less than 43 MW.
Current Inflow Forecasts and Model Projections
The hydrologic outlook forecast for water year 2013 projects that the most probable (median) unregulated inflow volume will be 7.60 maf (70% of average based on the period 1981-2010). Based on this hydrologic outlook, the October 24-Month study projects the annual release volume for water year 2013 will be 8.23 maf and the end of water year reservoir elevation and storage for Lake Powell will be 3608.52 (91.48 feet from full pool) and 12.582 maf (51.7% capacity), respectively.
If hydrologic conditions and projections become wetter, it is possible that beginning in April, the Equalization tier will govern the operations of Lake Powell for the remainder of the water year and the release volume for 2013 could be greater than 8.23 maf. Based on analysis of a range of inflow scenarios, the current probability of realizing an inflow volume that would trigger Equalization in 2013 is approximately 20 percent.
Upper Colorado River Basin Hydrology
Since water year 2005, the Upper Colorado River Basin has experienced significant year to year hydrologic variability. The unregulated inflow to Lake Powell, which is a good measure of hydrologic conditions in the Colorado River Basin, has averaged a water year volume of 10.22 maf (94% of average (period 1981-2010)) during the period from 2005 through 2012. The hydrologic variability during this period has been from a low water year unregulated inflow volume of 4.91 maf (45% of average) in water year 2012 to a high water year unregulated inflow volume of 15.97 maf (147% of average) in water year 2011. Based on observed inflows and current forecasts, water year 2013 unregulated inflow is expected to be 7.59 maf (70% of average).
Overall reservoir storage in the Colorado River Basin has increased by over 4 maf since the beginning of water year 2005 and this is an improvement over the persistent drought conditions during water years 2000 through 2004. From the beginning of water year 2005 to the beginning of water year 2013, the total reservoir storage in the Colorado River Basin increased from 29.8 maf (50% of capacity) to 33.9 maf (57 % of capacity). However, this period experienced increases and decreases in total Colorado Basin storage in response to wet and dry hydrology.
RRFW thanks Katrina Grantz of the USBOR for this information.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ RIVERWIRE is a free service to the community of river lovers from River Runners for Wilderness. To join, send an e-mail address to riverwire@rrfw.org and we’ll add it to the RRFW RIVERWIRE e-mail alerts list. Join RRFW’s listserver to stay abreast of and participate in the latest river issues. It’s as easy as sending a blank e-mail to Rafting_Grand_Canyon-subscribe@yahoogroups.com Check out RRFW’s Rafting Grand Canyon Wiki for free information on Do-It-Yourself Grand Canyon rafting info http://www.rrfw.org/RaftingGrandCanyon/Main_Page Check out new items and donate at the RRFW Store! RRFW is a non-profit project of Living Rivers. https://www.rrfw.org/store
RRFW Riverwire – Glen Canyon Dam Update October 24, 2012
Current Status
Releases from Glen Canyon Dam in October are averaging approximately 8,030 cfs (cubic feet per second) and are steady with no fluctuations for hydropower generation. The scheduled release volume for October is 494 kaf (thousand acre-feet). In September and October, as part of the 2008 FONSI (Finding of No Significant Impact), releases from Glen Canyon Dam will be steady for a steady flow experiment. 2012 is the last year of the 5-year steady flow experiment. The anticipated release volume for November is 600 kaf with fluctuations for power generation throughout the day consistent with the Glen Canyon Operating Criteria (Federal Register, Volume 62, No. 41, March 3, 1997). However, the release volume may be adjusted in the event of a High Flow Experiment. (see below).
This fall marks the first season under a multi-year High Flow Protocol announced earlier this year by Secretary Salazar. See the following link for more details: http://www.doi.gov/news/pressreleases/Salazar-Announces-Improvements-to-Glen -Canyon-Dam-Operations-to-Restore-High-Flows-and-Native-Fish-in-Grand-Canyon .cfm
Under this Protocol, high flow releases are linked to sediment input and other resource conditions below Glen Canyon Dam. Preliminary sediment estimates appear favorable for a high flow experimental release to occur during the period of November 18 – 25, 2012 should sediment and other conditions warrant.
Reclamation’s planning activities for the high flow release are focusing on an anticipated date of November 19, 2012 for the bypass release to begin; however, no final decisions on the dates, duration or amount of the release have been made. Dam operations to ramp up to powerplant capacity prior to the bypass event would begin on November 18. During the High Flow Experiment, total releases from Glen Canyon Dam at full bypass may reach approximately 42,000 cfs. The total experiment, including ramping, could last anywhere from one and a half to six and a half days. November releases from Glen Canyon Dam prior to and after the high flow experiment would fluctuate between 5,000cfs and 8,000cfs. As more information on the potential high flow release becomes available, that information will be updated here.
The unregulated inflow volume to Lake Powell in September was 104 thousand acre-feet (kaf) (25% of average). The release volume from Glen Canyon Dam in September was 481 kaf. The end of September elevation and storage of Lake Powell were 3621.6 feet (78.4 feet from full pool) and 13.93 maf (million acre-feet) (57.3% of full capacity). The reservoir elevation is now declining.
The water year unregulated inflow volume for 2012 was 4.91maf (45.3% of average), placing the 2012 as the third driest on record since the closure of Glen Canyon Dam in 1963. Only 2002 and 1977 were drier, receiving 2.64 maf and 3.53 maf, respectively. In terms of reservoir elevation and storage, Lake Powell reached its peak for water year 2012 on June 3rd at 3636.9 ft (63.1 feet from full pool) and 15.64 maf (64.3% of capacity), respectively. The peak elevation in 2012 was 24 feet below the 2011 peak elevation of 3660.9 ft.
Releases for Water Year 2012 totaled 9.466 maf. Pursuant to the 2007 Interim Guidelines, Lake Powell operated under the Equalization Tier in 2012. Due to the dry hydrologic conditions experienced in 2012, the Equalization release objective was 9.463 maf, which is 8.23 maf plus 1.233 maf (the Equalization release volume from 2011 that could not be achieved by September 30, 2011). Throughout water year 2012, Reclamation adjusted operations of Glen Canyon Dam to release the appropriate annual volume during 2012 to achieve Equalization objectives as practicably as possible by September 30, 2012.
Current Dam Operations
The operating tier for 2013 is the Upper Elevation Balancing Tier, as establish in August 2012 and pursuant to the Interim Guidelines. However, if hydrologic conditions and projections become wetter, it is possible that beginning in April, the Equalization tier will govern the operations of Lake Powell for the remainder of the water year. Based on analysis of a range of inflow scenarios, the current probability of realizing an inflow volume that would trigger Equalization in 2013 is approximately 20 percent. As hydrologic conditions for Lake Powell and Lake Mead change throughout the year, Reclamation will adjust operations of Glen Canyon Dam to release the appropriate annual volume during 2013 to achieve the governing operating tier objectives as practicably as possible by September 30, 2013.
Releases from Glen Canyon Dam in October are averaging approximately 8,030 cfs and are steady with no fluctuations for hydropower generation. The scheduled release volume for October is 494 kaf. In September and October, as part of the 2008 FONSI, releases from Glen Canyon Dam will be steady for a steady flow experiment. 2012 is the last year of the 5-year steady flow experiment.
The anticipated release volume for November is 600 kaf with fluctuations for power generation throughout the day consistent with the Glen Canyon Operating Criteria (Federal Register, Volume 62, No. 41, March 3, 1997). However, the release volume may be adjusted in the event of a High Flow Experiment. This fall marks the first season of a multi-year High-Flow Protocol, under which high flow releases are linked to sediment input and other resource conditions below Glen Canyon Dam. Preliminary analysis appears favorable for a high flow experimental release to occur during the period of November 18 – 25, 2012. During the High Flow Experiment, total releases from Glen Canyon Dam at full bypass may reach approximately 42,000 cfs. The total experiment, including ramping, could last anywhere from one and a half to six and a half days. In the event of a high flow experiment, releases from Glen Canyon Dam prior to and after the high flow experiment are anticipated to fluctuate between 5,000cfs and 8,000cfs.
In December, the release volume will likely be about 800 kaf, with fluctuations throughout the day from about 8,000 cfs in the early morning to about 16,000cfs in the early evening.
In addition to daily scheduled fluctuations for power generation, the instantaneous releases from Glen Canyon Dam may also fluctuate to provide 40 MW of system regulation. These instantaneous release adjustments stabilize the electrical generation and transmission system and translate to a range of about 1,100 cfs above or below the hourly scheduled release rate. Typically, fluctuations for system regulation are very short lived and balance out over the hour and do not have noticeable impacts on downstream river flow conditions.
Releases from Glen Canyon Dam can also fluctuate beyond scheduled fluctuations for power generation when called upon as a partner that shares reserve requirements within the electrical generator community (i.e. balancing area). To provide system reliability, all participating electricity generators within the balancing area maintain a specified level of generation capacity (i.e. reserves) that can be called upon when an unscheduled outage occurs. Glen Canyon Dam typically maintains 43 MW of reserves (approximately 1,100 cfs) for this purpose. Reserve calls can be maintained for a maximum of 2 hours after which time the generation rate should be returned to the original schedule. If reserves from Glen Canyon Dam are called upon, releases from the dam can exceed scheduled levels and can have a noticeable impact on the river downstream from Glen Canyon Dam. Calls for reserves are fairly infrequent and typically are for much less than 43 MW.
Current Inflow Forecasts and Model Projections
The hydrologic outlook forecast for water year 2013 projects that the most probable (median) unregulated inflow volume will be 7.60 maf (70% of average based on the period 1981-2010). Based on this hydrologic outlook, the October 24-Month study projects the annual release volume for water year 2013 will be 8.23 maf and the end of water year reservoir elevation and storage for Lake Powell will be 3608.52 (91.48 feet from full pool) and 12.582 maf (51.7% capacity), respectively.
If hydrologic conditions and projections become wetter, it is possible that beginning in April, the Equalization tier will govern the operations of Lake Powell for the remainder of the water year and the release volume for 2013 could be greater than 8.23 maf. Based on analysis of a range of inflow scenarios, the current probability of realizing an inflow volume that would trigger Equalization in 2013 is approximately 20 percent.
Upper Colorado River Basin Hydrology
Since water year 2005, hydrologic conditions in the Upper Colorado River Basin have resulted in significant year to year variability. The unregulated inflow to Lake Powell, which is a good measure of the hydrologic condition in the Colorado River Basin, has averaged a water year volume of 10.22 maf (94% of average (period 1981-2010)) during the period from 2005 through 2012. The hydrologic variability during this period has been from a low water year unregulated inflow volume of 4.91 maf (45% of average) in water year 2012 to a high water year unregulated inflow volume of 15.97 maf (147% of average) in water year 2011. Based on observed inflows and current forecasts, water year 2013 unregulated inflow is expected to be 7.60 maf (70% of average).
Overall reservoir storage in the Colorado River Basin has increased by over 4 maf since the beginning of water year 2005 and this is an improvement over the drought conditions during water years 2000 through 2004. On October 1, 2004, the beginning of water year 2005, the total reservoir storage in the Colorado River Basin was 29.8 maf (50% of capacity). On October 1, 2012, the beginning of water year 2013, the total reservoir storage in the Colorado River Basin was 33.9 maf (57 % of capacity).
RRFW thanks Katrina Grantz, US Bureau of Reclamation, for this information
RIVERWIRE is a free service to the community of river lovers from River Runners for Wilderness. To join, send an e-mail address to riverwire@rrfw.org and we’ll add it to the RRFW RIVERWIRE e-mail alerts list.
RRFW Riverwire – Glen Canyon Dam Update July 9, 2012
Glen Canyon Dam / Lake Powell
For the Water Supply period April through July, 2012 will most likely be the third driest year on record since the closure of Glen Canyon Dam in 1963. Only 1977 and 2002 will have had lower April-July unregulated inflow volumes to Lake Powell than what is most likely to occur in 2012.
The monthly unregulated inflow volume to Lake Powell for June was 353 thousand acre-feet (kaf) (13% of average). This was very nearly equal to the forecasted unregulated inflow volume at the beginning of June which was 350 kaf. The release volume from Glen Canyon Dam in June was 709 kaf which was 1,000 acre-feet above what was scheduled for release during the month. The end of June elevation and storage of Lake Powell was 3633.90 feet (66.10 feet from full pool) and 15.29 million acre-feet (maf) (62.88% of full capacity).
The Water Supply Forecast for Lake Powell (April through July Unregulated Inflow Volume) for July remained unchanged from June at 2.01 maf (28% of average).
Current Dam Operations
In August 2011, pursuant to the Interim Guidelines, the Operating Tier for Glen Canyon Dam was established to be the Equalization Tier. Under the Equalization Tier when conditions dry out as they have this year, the minimum annual release from Lake Powell can generally be as low as 8.23 maf. However, water year 2011 was a very wet Equalization year and not all of the Equalization release volume for 2011 could be achieved by September 30, 2011. As a result, 1.233 maf of the 2011 Equalization release volume was actually released after the end of water year 2011. This increased the minimum release volume for water year 2012 under Equalization to 9.463 maf. Under the dry hydrologic conditions currently projected for Lake Powell, the water year 2012 release volume is projected to be at this minimum Equalization level of 9.463 maf. As hydrologic conditions for Lake Powell and Lake Mead change throughout the year, Reclamation will adjust operations of Glen Canyon Dam to release the appropriate annual volume during 2012 to achieve Equalization objectives as practicably as possible by September 30, 2012.
Releases from Glen Canyon Dam are now averaging about 14,500 cubic feet per second (cfs) with fluctuations for power generation throughout the day that peak near 18,000 cfs in the afternoons and with early morning low level releases are about 10,000 cfs and this operation is consistent with the Glen Canyon Operating Criteria (Federal Register, Volume 62, No. 41, March 3, 1997). The release volume for July is scheduled to be 889 kaf and this volume is elevated slightly in order to target a release volume in August of 800 kaf. In August, fluctuations are projected to peak near 17,000 cfs during the afternoons with early morning low releases near 9,000 cfs. In September and October, as part of the 2008 FONSI, releases from Glen Canyon Dam will be steady for a steady flow experiment. The targeted release rate for September and October of 2012 is 8,000 cfs.
In addition to daily scheduled fluctuations for power generation, the instantaneous releases from Glen Canyon Dam may also fluctuate to provide 40 megawatts (MW) of system regulation. These instantaneous release adjustments stabilize the electrical generation and transmission system and translate to a range of about 1100 cfs above or below the hourly scheduled release rate. Typically, fluctuations for system regulation are very short lived and balance out over the hour and do not have noticeable impacts on downstream river flow conditions.
Releases from Glen Canyon Dam can also fluctuate beyond scheduled fluctuations for power generation when called upon as a partner that shares reserve requirements within the electrical generator community (i.e. balancing area). There are many generators that supply electricity to the transmission system within the balancing area. At times, a participating generator may experience operating conditions such that it cannot make its scheduled delivery of electricity to the system (i.e. unscheduled outage). To provide system reliability, all participating electricity generators within the balancing area maintain a specified level of generation capacity (i.e. reserves) that can be called upon when an unscheduled outage occurs. Glen Canyon Dam typically maintains 113 MW of reserves for this purpose.
Reserve agreements allow the controllers of the balancing area to call upon Glen Canyon Dam to produce up to an additional 113 MW of electricity beyond what is originally scheduled for a given hour. Reserve calls can be maintained for a maximum of 2 hours after which time the generation rate should be returned to the original schedule. The 113 MW reserve requirement for Glen Canyon Dam translates to approximately 2,800 cfs of flow in the river. When the balancing area controllers call for reserve generation from Glen Canyon Dam, releases from the dam can exceed scheduled levels and have a noticeable impact on the river downstream from Glen Canyon Dam. But these calls for reserves are fairly infrequent and typically are for much less than the required level of 113 MW.
Current Inflow Forecasts and Model Projections
Over the next three months (July, August and September) the forecasted unregulated inflow volume to Lake Powell is projected to be 100 kaf (9% of average), 150 kaf (30% of average) and 200 kaf (49% of average), respectively. These percent of averages are all based on the historic period from 1981 through 2010. The most probable (i.e. 50% likely to be exceeded) unregulated inflow volume for WY2012 is projected to be 5.0 maf (46% of average). Comparing this projected water year unregulated inflow volume to the driest year on record (2002) in which the unregulated inflow volume was only 2.64 maf (24% of average), water year 2012 will likely be very dry, yet not nearly as dry as conditions were in 2002. The currently projected water year unregulated inflow volume of 5.0 maf would rank as the 3rd driest year on record since the closure of Glen Canyon Dam (1963).
The annual release volume from Glen Canyon Dam will likely be 9.463 maf and the elevation of Lake Powell at the end of WY2012 is projected to be 3622.6 feet above sea level which is 77.4 feet from the full pool elevation of 3700 feet. This elevation corresponds to a live storage volume of 14.04 maf (58 % of full capacity). These projections are based on conditions in the July 24-Months Study.
The June 2012 24-Month Study has been published and is available here. The July 2012 24-Month Study will be published by July 13, 2012 and a link to this study will be provided at this website. Updated elevation projections for Lake Powell through water year 2012 based on the most recently published 24-Month Study are maintained at: Lake Powell Projected Elevations.
Upper Colorado River Basin Hydrology
Since water year 2005, hydrologic conditions in the Upper Colorado River Basin have been near average with significant variability from year to year. The unregulated inflow to Lake Powell, which is a good measure of the hydrologic condition in the Colorado River Basin, has averaged a water year volume of 10.98 maf (101% of average (period 1981-2010)) during the period from 2005 through 2011. The hydrologic variability during this period has been from a low water year unregulated inflow volume of 8.62 maf (80% of average) in water year 2006 to a high water year unregulated inflow volume of 15.97 maf (147% of average) which occurred in water year 2011.
Overall reservoir storage in the Colorado River Basin has increased by over 8 maf since the beginning of water year 2005 and this is a significant improvement over the drought conditions during water years 2000 through 2004. On October 1, 2004, the beginning of water year 2005, the total reservoir storage in the Colorado River Basin was 29.84 maf (50.2% of capacity). On October 1, 2011, the beginning of water year 2012, the total reservoir storage in the Colorado River Basin was 38.66 maf (64.8% of capacity). As of July 8, 2012 the total reservoir storage in the Colorado River Basin was 35.80 maf (60.0% of capacity).
RRFW thanks Rick Clayton of the USBOR for this information.
RIVERWIRE is a free service to the community of river lovers from River Runners for Wilderness. To join, send an e-mail address to riverwire@rrfw.org and we’ll add it to the RRFW RIVERWIRE e-mail alerts list.
RRFW Riverwire – Glen Canyon Dam Update May 10, 2012
Glen Canyon Dam, Lake Powell
Snowpack conditions above Lake Powell have been well below average all year and are now nearly melted out. The runoff from the melting snow has been less than impressive and the inflow to Lake Powell so far has peaked at just over 15,000 cubic feet per second (cfs). It is possible that this peak could be exceeded if temperature conditions warm quickly in the coming weeks. The Colorado Basin River Forecast Center will update the Water Supply Forecast for Lake Powell (April through July Unregulated Inflow Volume) in early May. In April this forecast was for 3.50 maf (49% of average) of unregulated inflow to Lake Powell.
The monthly unregulated inflow volume to Lake Powell for April was 764 thousand acre-feet (kaf) (72% of average). This was 36 kaf below what was forecasted in early April. The release volume from Glen Canyon Dam in April was 606 kaf which was 6,000 acre-feet above what was scheduled for release during the month. As a result of the difference between the projections made in early April and actual conditions and operations that occurred in April, the elevation of Lake Powell at the end of April was 0.17 feet (about 2 inches) higher than projected. On April 30, 2012 the elevation of Lake Powell was 3635.76 feet above sea level (64.24 feet below full pool).
Current Dam Operations
Releases from Glen Canyon Dam are now averaging about 10,050 cfs with fluctuations for power generation throughout the day that peak near 13,000 cfs in the afternoons and with early morning low level releases are about 7,000 cfs and this operation is consistent with the Glen Canyon Operating Criteria (Federal Register, Volume 62, No. 41, March 3, 1997). The release volume for May is scheduled to be 600 kaf. In June, the monthly release volume will likely be about 714 kaf. Release fluctuations in June are projected to be in the range from about 9,000 cfs during the early morning hours to an afternoon peak of about 15,000 cfs.
In addition to daily scheduled fluctuations for power generation, the instantaneous releases from Glen Canyon Dam may also fluctuate to provide 40 MW of system regulation. These instantaneous release adjustments stabilize the electrical generation and transmission system and translate to a range of about 1100 cfs above or below the hourly scheduled release rate. Typically, fluctuations for system regulation are very short lived and balance out over the hour and do not have noticeable impacts on downstream river flow conditions.
Releases from Glen Canyon Dam can also fluctuate beyond scheduled fluctuations for power generation when called upon as a partner that shares reserve requirements within the electrical generator community (i.e. balancing area). There are many generators that supply electricity to the transmission system within the balancing area. At times, a participating generator may experience operating conditions such that it cannot make its scheduled delivery of electricity to the system (i.e. unscheduled outage). To provide system reliability, all participating electricity generators within the balancing area maintain a specified level of generation capacity (i.e. reserves) that can be called upon when an unscheduled outage occurs. Glen Canyon Dam typically maintains 113 megawatts (MW) of reserves for this purpose.
Reserve agreements allow the controllers of the balancing area to call upon Glen Canyon Dam to produce up to an additional 113 MW of electricity beyond what is originally scheduled for a given hour. Reserve calls can be maintained for a maximum of 2 hours after which time the generation rate should be returned to the original schedule. The 113 MW reserve requirement for Glen Canyon Dam translates to approximately 2,800 cfs of flow in the river. When the balancing area controllers call for reserve generation from Glen Canyon Dam, releases from the dam can exceed scheduled levels and have a noticeable impact on the river downstream from Glen Canyon Dam. But these calls for reserves are fairly infrequent and typically are for much less than the required level of 113 MW.
In August 2011, pursuant to the Interim Guidelines, the Operating Tier for Glen Canyon Dam was established to be the Equalization Tier. Under the Equalization Tier for 2012, with 1.233 million acre feet (maf) of release carried over from 2011 to 2012, the annual release volume for 2012 could be as low as 9.46 maf or higher depending on actual inflow conditions. As hydrologic conditions for Lake Powell and Lake Mead change throughout the year, Reclamation will adjust operations of Glen Canyon Dam to release the appropriate annual volume during 2012 to achieve Equalization objectives as practicably as possible by September 30, 2012.
Current Inflow Forecasts and Model Projections
Over the next three months (May, June and July) the forecasted unregulated inflow volume to Lake Powell is projected to be 1,050 kaf (45% of average), 1,150 kaf (43% of average) and 500 kaf (46% of average), respectively. These percent of averages are all based on the historic period from 1981 through 2010. Combining this forecast with the April Water Supply Forecast and extending projections to the end of WY2012, the most probable (i.e. 50% likely to be exceeded) unregulated inflow volume for WY2012 is projected to be 6.79 maf (63% of average).
Comparing this projected water year unregulated inflow volume to the driest year on record (2002) in which the unregulated inflow volume was only 2.64 maf (24% of average), water year 2012 will likely be very dry yet not close to the driest year on record. There is still a fair amount of uncertainty associated with the forecast conditions for the remainder of the water year.. Recent analysis indicates that it is reasonably possible for the actual unregulated inflow volume for water year 2012 to be as low as 4.9 maf (45% of average) or as high as 9.2 maf (85% of average) depending on the range of precipitation patterns that could occur over the next several months.
Based on the reasonable range inflow conditions that could occur this year, the annual release volume from Glen Canyon Dam could be as low as 9.46 maf to as high as 9.81 maf. Under the most probable inflow condition, the annual release volume is projected to be 9.46 maf and the elevation of Lake Powell at the end of WY2012 is projected to be 3632.5 feet above sea level. This elevation corresponds to a live storage volume of 15.14 maf (62 % of full capacity). These projections are based on conditions in the April 24-Months Study.
Since water year 2005, hydrologic conditions in the Upper Colorado River Basin have been near average with significant variability from year to year. The unregulated inflow to Lake Powell, which is a good measure of the hydrologic condition in the Colorado River Basin, has averaged a water year volume of 10.98 maf (101% of average (period 1981-2010)) during the period from 2005 through 2011. The hydrologic variability during this period has been from a low water year unregulated inflow volume of 8.62 maf (80% of average) in water year 2006 to a high water year unregulated inflow volume of 15.97 maf (147% of average) which occurred in water year 2011.
Overall reservoir storage in the Colorado River Basin has increased by over 8 maf since the beginning of water year 2005 and this is a significant improvement over the drought conditions during water years 2000 through 2004. On October 1, 2004, the beginning of water year 2005, the total reservoir storage in the Colorado River Basin was 29.84 maf (50.2% of capacity). On October 1, 2011, the beginning of water year 2012, the total reservoir storage in the Colorado River Basin was 38.66 maf (64.8% of capacity). As of May 2, 2012 the total reservoir storage in the Colorado River Basin was 37.17 maf (62.3% of capacity).
RRFW thanks Rick Clayton of the USBOR for this information.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ RIVERWIRE is a free service to the community of river lovers from River Runners for Wilderness. To join, send an e-mail address to riverwire@rrfw.org and we’ll add it to the RRFW RIVERWIRE e-mail alerts list. Join RRFW’s listserver to stay abreast of and participate in the latest river issues. It’s as easy as sending a blank e-mail to Rafting_Grand_Canyon-subscribe@yahoogroups.com Check out RRFW’s Rafting Grand Canyon Wiki for free information on Do-It-Yourself Grand Canyon rafting info http://www.rrfw.org/RaftingGrandCanyon/Main_Page Check out new items and donate at the RRFW Store! RRFW is a non-profit project of Living Rivers. https://www.rrfw.org/store
RRFW Riverwire – Glen Canyon Dam Update February 10, 2012
Glen Canyon Dam, Lake Powell
In January 2012 the unregulated inflow volume to Lake Powell was 356 thousand acre feet (kaf), or 99% of average. This volume is very close to the final forecast for January issued by the Colorado Basin River Forecast Center on January 5th which was 375 kaf. The elevation of Lake Powell on January 31st, 2012 was 3636.90 feet above sea level (63.10 feet below full pool). During January, the elevation of Lake Powell decreased by 3.52 feet and it is likely that the elevation will continue to decrease near this rate for approximately 2 more months. By late March or early April, when the snowpack begins to melt, inflows will likely increase to a point where they are greater than releases and the elevation will begin to rise. Snowpack conditions above Lake Powell are 77% of average as of February 8, 2012.
The current Water Supply forecast (April through July Unregulated Inflow Volume) for Lake Powell for 2012 is 5.05 million acre feet (maf) which is 71% of average. Based on this inflow forecast, it is currently projected that the most probable annual release from Glen Canyon Dam in water year 2012 will be 9.46 maf. At this time of year however, there is a high level of uncertainty in hydrologic forecasts and the annual release volume from Glen Canyon Dam in WY2012 will ultimately be based on the actual inflows that occur during 2012 rather than this Water Supply forecast.
Current Dam Operations
In August 2011, pursuant to the Interim Guidelines, the Operating Tier for Glen Canyon Dam was established to be the Equalization Tier. Under the Equalization Tier for 2012, with 1.233 maf of release carried over from 2011 to 2012, the annual release volume for 2012 could be as low as 9.46 maf or higher depending on actual inflow conditions. As hydrologic conditions for Lake Powell and Lake Mead change throughout the year, Reclamation will adjust operations of Glen Canyon Dam to release the appropriate annual volume during 2012 to achieve Equalization objectives as practicably as possible by September 30, 2012.
Releases from Glen Canyon Dam are currently averaging about 12,500 cubic feet per second (cfs) with fluctuations for power generation throughout the day that peak near 13,000 cfs in the afternoons and with early morning low level releases are about 7,000 cfs. This operation is consistent with the Glen Canyon Operating Criteria (Federal Register, Volume 62, No. 41, March 3, 1997). The release volume for February is scheduled to be 650 kaf. In March, the monthly release volume will likely be 600 kaf and fluctuating releases from Glen Canyon Dam will likely average about 10,100 cfs each day with scheduled daily fluctuations occurring within the range from 7,000 cfs to 13,000 cfs.
In addition to daily scheduled fluctuations for power generation, the instantaneous releases from Glen Canyon Dam may also fluctuate to provide 40 megawatts (MW) of system regulation. These instantaneous release adjustments stabilize the electrical generation and transmission system and translate to a range of about 1100 cfs above or below the hourly scheduled release rate. Typically, fluctuations for system regulation are very short lived and balance out over the hour and do not have noticeable impacts on downstream river flow conditions.
Releases from Glen Canyon Dam can also fluctuate beyond scheduled fluctuations for power generation when called upon as a partner that shares reserve requirements within the electrical generator community (i.e. balancing area). There are many generators that supply electricity to the transmission system within the balancing area. At times, a participating generator may experience operating conditions such that it cannot make its scheduled delivery of electricity to the system (i.e. unscheduled outage). To provide system reliability, all participating electricity generators within the balancing area maintain a specified level of generation capacity (i.e. reserves) that can be called upon when an unscheduled outage occurs. Glen Canyon Dam typically maintains 113 MW of reserves for this purpose.
Reserve agreements allow the controllers of the balancing area to call upon Glen Canyon Dam to produce up to an additional 113 MW of electricity beyond what is originally scheduled for a given hour. Reserve calls can be maintained for a maximum of 2 hours after which time the generation rate should be returned to the original schedule. The 113 MW reserve requirement for Glen Canyon Dam translates to approximately 2,800 cfs of flow in the river. When the balancing area controllers call for reserve generation from Glen Canyon Dam, releases from the dam can exceed scheduled levels and have a noticeable impact on the river downstream from Glen Canyon Dam. But these calls for reserves are fairly infrequent and typically are for much less than the required level of 113 MW.
Current Inflow Forecasts and Model Projections
Over the next three months (February, March and April) the forecasted unregulated inflow volume to Lake Powell is projected to be 390 kaf (99% of average), 550 kaf (83% of average) and 800 kaf (76% of average), respectively. These percent of averages are all based on the historic period from 1981 through 2010. Combining this forecast with the February Water Supply Forecast and extending projections to the end of WY2012, the most probable (i.e. 50% likely to be exceeded) unregulated inflow volume for WY2012 is projected to be 8.48 maf (78% of average). There is significant uncertainty associated with this forecast. Recent analysis indicates that it is reasonably possible for the actual unregulated inflow volume to be as low as 5.48 maf (51% of average) or as high as 12.65 maf (117% of average) depending on the range of precipitation patterns that could occur over the next several months.
Based on the reasonable range inflow conditions that could occur this year, the annual release volume from Glen Canyon Dam could be as low as 9.46 maf to as high as 12.92 maf. Under the most probable inflow condition, the annual release volume is projected to be 9.46 maf and the elevation of Lake Powell at the end of WY2012 is projected to be 3643.2 feet above sea level. This elevation corresponds to a live storage volume of 16.38 maf (67% of full capacity).
Upper Colorado River Basin Hydrology
Since water year 2005, hydrologic conditions in the Upper Colorado River Basin have been near average with significant variability from year to year. The unregulated inflow to Lake Powell, which is a good measure of the hydrologic condition in the Colorado River Basin, has averaged 10.98 maf (101% of average (period 1981-2010)) per year during the period from 2005 through 2011. The hydrologic variability during this period has been from a low water year unregulated inflow of 8.62 maf (80% of average) in water year 2006 to a high of 15.97 maf (147% of average) which occurred in water year 2011.
Overall reservoir storage in the Colorado River Basin has increased by nearly 10 maf since the beginning of water year 2005 and this is a significant improvement over the drought conditions during water years 2000 through 2004. On October 1, 2004, the beginning of water year 2005, the total reservoir storage in the Colorado River Basin was 29.84 maf (50.2% of capacity). As of January 30, 2012 the total reservoir storage in the Colorado River Basin was 38.35 maf (64.3% of capacity). RRFW thanks Rick Clayton of the USBOR for this information.
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RRFW Riverwire – Glen Canyon Dam Update January 19, 2012
Glen Canyon Dam, Lake Powell
During December 2011 the unregulated inflow volume to Lake Powell was 359 thousand acre-feet (kaf). This represents 99% of average based on the historic period from 1981 through 2010. This was well below the volume forecasted for the month of December which was 500 kaf (138% of average). As a result, the elevation of Lake Powell at the end of December was 3639.7 feet above sea level which was 1.1 feet lower than projected at the beginning of December.
Snowpack conditions above Lake Powell are well below average for this time of year. As of January 9, 2012 the overall snowpack above Lake Powell was only 60% of average. Reclamation has received the first Water Supply forecast for 2012 and the April through July unregulated inflow to Lake Powell is projected to be 5.05 million acre-feet (maf) which is 71% of average. Based on this forecast, the projected most probable (i.e. 50% likely to be exceeded) annual release volume from Glen Canyon Dam in water year 2012 will be 9.46 maf. At this time of year however, there is a high level of uncertainty in hydrologic forecasts and the annual release volume from Glen Canyon Dam in WY2012 will ultimately be based on actual hydrology rather than forecasted hydrology.
Current Dam Operations
In response to the Water Supply forecast issued for Lake Powell in January, Reclamation has reduced the release volume for January from 1000 kaf to 850 kaf. This reduction began on January 10, 2012. Releases from Glen Canyon Dam are currently averaging about 13,200 cubic feet-per-second (cfs) with fluctuations for power generation throughout the day that peak near 17,500 cfs in the afternoons. Early morning low releases are about 9,500 cfs. This operation is consistent with the Glen Canyon Operating Criteria (Federal Register, Volume 62, No. 41, March 3, 1997).
It is forecasted that in February, releases from Glen Canyon Dam will most likely be about 650 kaf which is a daily average of 11,300 cfs. Fluctuations will range between 7,000 cfs off peak to 13,000 cfs on-peak. In March, current forecasts estimate a likely release of 600 kaf which is a daily average of 9,758 cfs. Fluctuations will range between 7,000 cfs off peak and 13,000 cfs on peak. February’s release volume will most likely not change. While the release volume in March won’t be less than 600 kaf, if the basin hydrology becomes wetter than currently expected, there is a moderate chance that Reclamation will increase the release volume.
In addition to hourly release fluctuations for load following power generation, the instantaneous releases from Glen Canyon Dam may also fluctuate somewhat to provide 40 MW of system regulation. These instantaneous release adjustments stabilize the electrical generation and transmission system and translate to a range of about 1100 cfs above or below the hourly release rate that is scheduled for a given hour. Typically, fluctuations for system regulation are very short lived and balance out over the hour and do not have noticeable impacts on river flow conditions.
Releases from Glen Canyon Dam can also fluctuate beyond the typical load following pattern when called upon as a partner that shares reserve requirements within the electrical generator community (i.e. control area). There are many generators that supply electricity to the transmission system within the control area. At times, a participating generator may experience operating conditions such that it cannot make its scheduled delivery of electricity to the system (i.e. outage). To provide system reliability, all participating electricity generators within the control area maintain a specified level of generation capacity (i.e. reserves) that can be called upon when an outage occurs. Glen Canyon Dam typically maintains 109 megawatts (MW) of reserves for this purpose.
Reserve agreements allow the controllers of the transmission system to call upon Glen Canyon Dam for up to 109 MW of additional generation beyond what is originally scheduled for a given hour. These calls for reserve generation can be maintained for up to 2 hours in total duration. The 109 MW reserve requirement for Glen Canyon Dam translates to approximately 2,700 cfs of flow in the river and calls for reserves can have noticeable impacts on river flow conditions. Calls for reserves are fairly infrequent and typically are for much less than the maximum requirement of 109 MW.
In August 2011, as part of the Colorado River Annual Operating Plan process, the Operating Tier for Glen Canyon Dam was determined to be the Equalization Tier under the 2008 Interim Guidelines. Under the Equalization Tier, with 1.233 maf of release volume carried over from 2011 to 2012, the annual release volume for WY2012 could be as low as 9.46 maf to as high as 13.1 maf or higher depending on actual inflow conditions. As inflow and storage conditions for Lake Powell and Lake Mead change throughout the year, Reclamation will make practicable adjustments to the operation of Glen Canyon Dam to release the appropriate annual volume during 2012. The overall goal during 2012 in terms of annual release will be to achieve the objectives of the Equalization Tier of the Interim Guidelines.
Current Inflow Forecasts and Model Projections
Over the next three months (January, February, March) the forecasted unregulated inflow volume to Lake Powell is projected to be 375 kaf (104% of average), 410 kaf (104% of average) and 575 kaf (86% of average), respectively. These percent of averages are all based on the historic period from 1981 through 2010. Combining this forecast with the January Water Supply Forecast and extending projections to the end of Water Year (WY) 2012, the mostprobable (i.e. 50% likely to be exceeded) unregulated inflow volume for WY2012 is now projected to be 8.55 maf (79% of average). The minimum probable (i.e. 90% likely to be exceeded) unregulated inflow volume for WY2012 is now projected to be 5.48 maf (51% of average). The maximum probable (i.e. 10% likely to be exceeded) unregulated inflow volume for WY2012 is now projected to be 12.65 maf (117% of average).
Based on this range of possible inflow conditions, the January 24-Month Study projects the annual release volume for WY2012 to be as lows as 9.46 maf (under the minimum probable inflow condition) to as high as 13.01 maf (under the maximum probable inflow condition). Under the most probable inflow condition, the annual release volume is projected to be 9.46 maf and the elevation of Lake Powell at the end of WY2012 is projected to be 3643.9 feet above sea level. This elevation corresponds to a live storage volume of 16.47 maf (68% of full capacity).
Upper Colorado River Basin Hydrology
Since water year 2005, hydrologic conditions in the Upper Colorado River Basin have been near average with significant variability from year to year. The unregulated inflow to Lake Powell, which is a good measure of the hydrologic condition in the Colorado River Basin, has averaged 10.98 maf (101% of average (period 1981-2010) per year during the period from 2005 through 2011. The hydrologic variability during this period has been from a low water year unregulated inflow of 8.62 maf (80% of average) in water year 2006 to a high of 15.97 maf (147% of average) which occurred in water year 2011.
Overall reservoir storage in the Colorado River Basin has increased by nearly 10 maf since the beginning of water year 2005 and this is a significant improvement over the drought conditions during water years 2000 through 2004. On October 1, 2004, the beginning of water year 2005, the total reservoir storage in the Colorado River Basin was 29.84 maf (50.2% of capacity). As of January 10, 2012 the total reservoir storage in the Colorado River Basin was 38.54 maf (64.8% of capacity).
RRFW thanks Rick Clayton of the USBOR for this information.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ RIVERWIRE is a free service to the community of river lovers from River Runners for Wilderness. To join, send an e-mail address to riverwire@rrfw.org and we’ll add it to the RRFW RIVERWIRE e-mail alerts list.
RRFW Riverwire – Glen Canyon Dam Update Dec 14, 2011
Glen Canyon Dam / Lake Powell
During November 2011 the unregulated inflow volume to Lake Powell was 570 thousand acre feet (kaf ) – 108% of average. This was very close to the forecast volume issued by the Colorado Basin River Forecast Center on November 1, 2011. The forecast volume was 600 kaf (110% of average). Releases from Glen Canyon Dam during November were 1099 kaf and the elevation of Lake Powell decreased by 4.59 ending November at an elevation of 3645.69 feet above sea level. Releases from Glen Canyon Dam are currently averaging approximately 20,300 cfs and are near steady. This release rate is likely to continue to near the end of December and then will likely be reduced to a daily average release of approximately 16,300 cfs with daily fluctuations for power generation.
Current Dam Operations
Releases from Glen Canyon Dam for the Steady Flow Experiment (see Experimental Releases from Glen Canyon Dam, Arizona 2008 through 2012, Final Environmental Assessment and Finding of No Significant Impact) ended at midnight on October 31, 2011. The steady flow target for 2011 was 15,500 cfs which was the maximum sustainable release rate from Glen Canyon Dam during September and October. Since then, releases from Glen Canyon Dam have been maximized at powerplant capacity which varies depending on unit efficiency and availability. Current releases are approximately 20,300 cfs.
Since March 2011, releases from Glen Canyon Dam have been maximized through the powerplant in order to achieve the Equalization objectives of the Interim Guidelines. The Equalization objective for water year 2011 was to release sufficient volume from Glen Canyon Dam during the water year such that the elevation of Lake Powell would be 3643 feet above sea level on September 30, 2011.
Inflows to Lake Powell during the spring and summer of 2011 were well above average and the 7 months of maximum powerplant capacity releases from Glen Canyon Dam were not sufficient to achieve an elevation of 3643 feet on September 30, 2011. The elevation of Lake Powell on September 30, 2011 was 3653.01 feet above sea level and this translates to a volume of 1.233 maf that was in storage in Lake Powell on September 30, 2011 that would have otherwise been released for Equalization during water year 2011 if the powerplant had the capacity to make these higher releases.
Releases through the powerplant during the first 3 months of water year 2012 (October, November and December, 2011) have continued at powerplant capacity in order to make up for the Equalization releases that were not made in water year 2011 due to the limitations of the powerplant. It is currently projected that the additional release volume will be completed by the end of December 2011 at which time releases from Glen Canyon Dam will be reduced. It is estimated that this release reduction will likely occur on or about December 28, 2011. The instantaneous release rate from Glen Canyon Dam may fluctuate somewhat to provide 40 MW of system regulation.
These instantaneous release adjustments maintain stable conditions within the electrical generation and transmission system and result in momentary release fluctuations within a range of about 1100 cfs above or below the targeted hourly release rate. The momentary fluctuations for regulation are very short lived and typically balance out over the hour.
Spinning and non-spinning reserve generation may also be maintained at Glen Canyon Dam. In order for Colorado River Storage Project (CRSP) powerplants to participate in the electrical generation and transmissions system, these powerplants must maintain a level of generation capacity available in reserve to assist the local control area for when unanticipated generation outages occur. The current CRSP powerplant reserve requirement is 109 MW (equivalent to approximately 2,675 cfs of release from Glen Canyon Dam).
When an electrical outage occurs within the control area, CRSP powerplants can be called upon to provide up to 109 MW of additional generation for up to 2 hours. Under normal circumstances, calls for reserves are infrequent and for much less than the required 109 MW. Because Glen Canyon Powerplant is the largest facility of the CRSP powerplants, typically most of the CRSP reserve requirement is maintained at Glen Canyon Dam but at times this reserve requirement is maintained at other plants within the CRSP system.
Current Inflow Forecasts and Model Projections
Over the next three months (December, January and February) the forecasted unregulated inflow to Lake Powell is projected to be above average with monthly percent of average forecasts of 115%, 111% and 107%, respectively. Based on these updated forecast values and the Hydrologic Outlook for water year 2012 (provided in October, 2011) the current projection for the most probable unregulated inflow volume to Lake Powell for water year 2012 is 11.4 maf (95% of average). At this time of year, there is a high level of uncertainty associated with this projection. Based on this projection, the December 2011 24-Month Study projects the water year 2012 most probable release volume will be 11.9 maf under the Equalization Tier of the Interim Guidelines. The December 2011 24-Month Study also projects the elevation condition for Lake Powell and Lake Mead at the end of water year 2012 to be 3645.0 feet and 1139.4 feet, respectively.
Upper Colorado River Basin Hydrology
Since water year 2005, hydrologic conditions in the Upper Colorado River Basin have been slightly below average with significant variability from year to year. The unregulated inflow to Lake Powell, which is a good measure of the hydrologic condition in the Colorado River Basin, has averaged 11.15 maf per year during the period from 2005 through 2011. This is slightly below the official average of 12.04 maf per year. The hydrologic variability during this period has been from a low water year unregulated inflow of 8.40 maf (70% of average) in water year 2006 to a high of over 16.77 maf (139% of average) which occurred in water year 2011.
Overall reservoir storage in the Colorado River Basin has increased by nearly 10 maf since the beginning of water year 2005 and this is a significant improvement over the drought conditions during water years 2000 through 2004. On October 1, 2004, the beginning of water year 2005, the total reservoir storage in the Colorado River Basin was 29.84 maf (50.2% of capacity). As of December 6, 2011, the total reservoir storage in the Colorado River Basin was 38.41 maf (64.6% of capacity).
RRFW thanks Rick Clayton, US Bureau of Reclamation
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ RIVERWIRE is a free service to the community of river lovers from River Runners for Wilderness. To join, send an e-mail address to riverwire@rrfw.org and we’ll add it to the RRFW RIVERWIRE e-mail alerts list.
RRFW Riverwire – Glen Canyon Dam Update November 7, 2011
Glen Canyon Dam Lake Powell
During October 2011 the unregulated inflow volume to Lake Powell was 575 thousand acre feet (kaf) which is 105% of average. This was approximately 75 kaf below what was projected in the October 24-Month Study and resulted in the elevation of Lake Powell ending October about 1.26 feet below what was projected in the October 24-Month Study. The October 31th, 2011 elevation of Lake Powell was 3650.27 feet above sea level which corresponds to a live storage of approximately 17.25 million acre feet (maf) and 70.9% of the full capacity of 24.32 maf.
For water year 2011, the observed unregulated inflow volume to Lake Powell was 16.77 maf (139% of average for the 1971-2000 historical period of record). The 2011 water year unregulated inflow volume was the 6th wettest out of 48 years since the closure of Glen Canyon Dam (1963). Water year unregulated inflow volumes of the magnitude observed in water year 2011 (or greater) would statistically be expected to occur in about 12-14% of all years.
The 2011 water year release volume from Glen Canyon Dam was 12.52 maf and this was the largest water year release volume made from Glen Canyon Dam since water year 1998. During water year 2011 the above average inflow volume combined with the large water year release volume from Glen Canyon Dam resulted in Lake Powell realizing a net gain in elevation (year over year) of 19.35 feet which translates to an increase in live storage in Lake Powell of 2.32 maf.
Current Dam Operations
Releases from Glen Canyon Dam for the 2011 steady flow experiment ended at midnight on October 31, 2011. Releases from Glen Canyon Dam are now being maximized within unit availability to release Equalization water for 2011. At the end of water year 2011 (September 30, 2011) the elevation of Lake Powell was 3653.01 feet above sea level and this was 10.01 feet above the Equalization level for water year 2011 (3643 feet) and translated to a volume of 1.123 maf that was in storage above the 2011 Equalization level. Releases from Glen Canyon Dam are being made at the full capacity of the power-plant to release this additional volume in order to achieve the 2011 Equalization objective. Once this additional volume has been released, releases from Glen Canyon Dam will be reduced from the full capacity of the power-plant. Current projections are that this objective will likely be completed by late December 2011.
Beginning on November 4, 2011, releases from Glen Canyon Dam will be adjusted to approximately 15,025 cubic feet per second (cfs) until the end of the day on November 10, 2011. Releases will likely be steady during this period. Glen Canyon Dam will maintain 109 megawatts (MW) of generation capacity for possible calls on reserve generation and 40 MW of generation capacity for system regulation.
Beginning on November 11, 2011, releases from Glen Canyon Dam will be adjusted to approximately 19,325 cfs until the end of the day on November 17, 2011. Releases will likely be steady during this period. Glen Canyon Dam will maintain 69 MW of generation capacity for possible calls on reserve generation and 40 MW of generation capacity for system regulation.
Beginning on November 18, 2011, releases from Glen Canyon Dam will be adjusted to approximately 20,750 cfs until the end of the day on November 30, 2011. Releases will likely be steady during this period. Glen Canyon Dam will maintain 15 MW of generation capacity for possible calls on reserve generation and 40 MW of generation capacity for system regulation.
The total release volume for November will be approximately 1.100 maf in order to complete this release schedule. Hourly and daily average releases from Glen Canyon Dam for November 2011 will be scheduled through Western Area Power Administration. While daily fluctuations are not anticipated during November, all release adjustments will be scheduled to be consistent with the Glen Canyon Dam Operating Criteria (Federal Register, Volume 62, No. 41, March 3, 1997).
The anticipated release volume for December 2011 will be 1.225 maf. This will be confirmed in a subsequent notification toward the end of November.
While the release rate from Glen Canyon Dam over the next two months will likely be near steady, the instantaneous releases from Glen Canyon Dam may fluctuate somewhat to provide 40 MW of system regulation. These instantaneous release adjustments maintain stable conditions within the electrical generation and transmission system and result in momentary release fluctuations within a range of about 1,100 cfs above or below the targeted hourly release rate. The momentary fluctuations for regulation are very short lived and typically balance out over the hour.
Spinning and non-spinning reserve generation may also be maintained at Glen Canyon Dam. In order for Colorado River Storage Project (CRSP) power-plants to participate in the electrical generation and transmissions system, these power-plants must maintain a level of generation capacity available in reserve to assist the local control area for when unanticipated generation outages occur. The current CRSP power-plant reserve requirement is 100 MW (equivalent to approximately 2,675 cfs of release from Glen Canyon Dam). When an electrical outage occurs within the control area, CRSP power-plants can be called upon to provide up to 100 MW of additional generation for up to 2 hours. Under normal circumstances, calls for reserves are infrequent and for much less than the required 100 MW. Because Glen Canyon Power-plant is the largest facility of the CRSP power-plants, most of the CRSP reserve requirement is maintained at Glen Canyon Dam but at times this reserve requirement is maintained at other plants within the CRSP system.
Current Inflow Forecasts and Model Projections
Over the next three months (October, November and December) the forecasted unregulated inflow to Lake Powell is projected to be above average with monthly percent of average forecasts of 119%, 115% and 120%, respectively. The hydrologic outlook forecast for water year 2012 has been revised in October and now projects that the most probable (median) unregulated inflow volume to be 11.6 maf (96% of average based on the period from 1971 through 2000). Based on this revised hydrologic outlook forecast, the October 24-Month Study projects the annual release volume for water year 2012 will likely be 12.26 maf. The October 24-Month Study also projects that the end of water year reservoir elevation and storage for Lake Powell will likely be 3645.00 feet (55.00 feet from full pool) and 16.60 maf (68% of capacity), respectively.
The October 2011 24-Month Study has been published and is available here:
This study will be updated to reflect November 2011conditions during the second week of November 2011. Updated elevation projections for Lake Powell through water year 2012 based on the most recently published 24-Month Study are maintained at:
Since water year 2005, hydrologic conditions in the Upper Colorado River Basin have been slightly below average with significant variability from year to year. The unregulated inflow to Lake Powell, which is a good measure of the hydrologic condition in the Colorado River Basin, has averaged 11.15 maf per year during the period from 2005 through 2011. This is slightly below the official average of 12.04 maf per year. The hydrologic variability during this period has been from a low water year unregulated inflow of 8.40 maf (70% of average) in water year 2006 to a high of over 16.77 maf (139% of average) which occurred in water year 2011.
Overall reservoir storage in the Colorado River Basin has increased by nearly 10 maf since the beginning of water year 2005 and this is a significant improvement over the drought conditions during water years 2000 through 2004. On October 1, 2004, the beginning of water year 2005, the total reservoir storage in the Colorado River Basin was 29.84 maf (50.2% of capacity). As of October 12, 2011, the total reservoir storage in the Colorado River Basin was 38.62 maf (64.9% of capacity).
RRFW thanks Rick Clayton of the USBOR for this information.
RIVERWIRE is a free service to the community of river lovers from River Runners for Wilderness. To join, send an e-mail address to riverwire@rrfw.org and we’ll add it to the RRFW RIVERWIRE e-mail alerts list.
RRFW Riverwire – Glen Canyon Dam Update October 13, 2011
Glen Canyon Dam Lake Powell
During September 2011 the unregulated inflow volume to Lake Powell was 532 thousand acre feet (kaf) or 112% of average. This was approximately 93 kaf below what was projected in the September 24-Month Study and resulted in the elevation of Lake Powell ending September about 0.92 feet below what was projected in the September 24-Month Study. The September 30th, 2011 elevation of Lake Powell was 3653.01 feet above sea level which corresponds to a live storage of approximately 17.59 million acre feet (maf) and 72.3% of the full capacity of 24.32 maf.
For water year 2011, the observed unregulated inflow volume to Lake Powell was 16.77 maf (139% of average for the 1971-2000 historical period of record). The 2011 water year unregulated inflow volume was the 6th wettest out of 48 years since the closure of Glen Canyon Dam (1963). Water year unregulated inflow volumes of the magnitude observed in water year 2011 (or greater) would statistically be expected to occur in about 12-14% of all years.
The 2011 water year release volume from Glen Canyon Dam was 12.52 maf and this was the largest water year release volume made from Glen Canyon Dam since water year 1998. During water year 2011 the above average inflow volume combined with the large water year release volume from Glen Canyon Dam resulted in Lake Powell realizing a net gain in elevation (year over year) of 19.35 feet which translates to an increase in live storage in Lake Powell of 2.32 maf.
Current Dam Operations
Releases from Glen Canyon Dam are now being made for a steady flow experiment that will continue to the end of October. Releases from Glen Canyon Dam are steady at approximately 15,500 cubic feet per second (cfs) and will likely remain at the level through October 31, 2011 to complete the 2 month steady flow experiment.
In early November through November 10, 2011, releases will likely continue to be steady near 15,500 cfs due to ongoing maintenance work at Glen Canyon Power-plant on units 5 and 6. On or about November 11, 2011 releases will likely be increased to approximately 22,600 cfs when units 5 and 6 are returned to service. The projected release volume for November is 1200 kaf.
While the release rate from Glen Canyon Dam over the next several months will likely be near steady, the instantaneous releases from Glen Canyon Dam may fluctuate somewhat to provide 40 MW of system regulation. These instantaneous release adjustments maintain stable conditions within the electrical generation and transmission system and result in momentary release fluctuations within a range of about 1100 cfs above or below the targeted hourly release rate. The momentary fluctuations for regulation are very short lived and typically balance out over the hour.
Spinning and non-spinning reserve generation is also maintained at Glen Canyon Dam. In order for Colorado River Storage Project (CRSP) power-plants to participate in the electrical generation and transmissions system, these power-plants must maintain a level of generation capacity available in reserve to assist the local control area for when unanticipated generation outages occur. The current CRSP power plant reserve requirement is 100 MW (equivalent to approximately 2,675 cfs of release from Glen Canyon Dam). When an electrical outage occurs within the control area, CRSP power-plants can be called upon to provide up to 100 MW of additional generation for up to 2 hours. Under normal circumstances, calls for reserves are infrequent and for much less than the required 100 MW. Because Glen Canyon Power-plant is the largest facility of the CRSP power-plants, most of the CRSP reserve requirement is maintained at Glen Canyon Dam.
Current Inflow Forecasts and Model Projections
Over the next three months (October, November and December) the forecasted unregulated inflow to Lake Powell is projected to be above average with monthly percent of average forecasts of 119%, 115% and 120%, respectively. The hydrologic outlook forecast for water year 2012 has been revised in October and now projects that the most probable (median) unregulated inflow volume to be 11.6 maf (96% of average based on the period from 1971 through 2000). Based on this revised hydrologic outlook forecast, the October 24-Month Study projects the annual release volume for water year 2012 will likely be 12.26 maf. The October 24-Month Study also projects that the end of water year reservoir elevation and storage for Lake Powell will likely be 3645.00 feet (55.00 feet from full pool) and 16.60 maf (68% of capacity), respectively.
Upper Colorado River Basin Hydrology
Since water year 2005, hydrologic conditions in the Upper Colorado River Basin have been slightly below average with significant variability from year to year. The unregulated inflow to Lake Powell, which is a good measure of the hydrologic condition in the Colorado River Basin, has averaged 11.15 maf per year during the period from 2005 through 2011. This is slightly below the official average of 12.04 maf per year. The hydrologic variability during this period has been from a low water year unregulated inflow of 8.40 maf (70% of average) in water year 2006 to a high of over 16.77 maf (139% of average) which occurred in water year 2011.
Overall reservoir storage in the Colorado River Basin has increased by nearly 10 maf since the beginning of water year 2005 and this is a significant improvement over the drought conditions during water years 2000 through 2004. On October 1, 2004, the beginning of water year 2005, the total reservoir storage in the Colorado River Basin was 29.84 maf (50.2% of capacity). As of October 12, 2011, the total reservoir storage in the Colorado River Basin was 38.62 maf (64.9% of capacity).
RRFW thanks Rick Clayton of the USBOR for this information.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ RIVERWIRE is a free service to the community of river lovers from River Runners for Wilderness. To join, send an e-mail address to riverwire@rrfw.org and we’ll add it to the RRFW RIVERWIRE e-mail alerts list.
RRFW Riverwire – Glen Canyon Dam Update August 7, 2011
Glen Canyon Dam Lake Powell
The unregulated inflow volume to Lake Powell so far in July (as of July 28th) has been 4.15 million acre feet (maf). At the current rate the unregulated inflow volume for July will likely be approximately 4.33 maf which is 278% of average. This July volume will likely be the 2nd wettest July on record since the closure of Glen Canyon Dam (1963). Only 1995 had a wetter July than this year at 4.41 maf. The expected unregulated inflow volume for the April through July period is approximately 12.9 maf (162% of average).
The reservoir elevation of Lake Powell has increased significantly so far this runoff season. On April 9, 2011 the elevation of Lake Powell was 3609.7 feet above sea level which was the lowest elevation observed so far in 2011. Since that time the elevation of Lake Powell has increased by over 50 feet and on July 28, 2011 the reservoir elevation of Lake Powell was 3660.79 feet above sea level (39.21 feet from full pool). The last time Lake Powell’s reservoir elevation was at this level was in October of 2001 (over 10 years ago) near the beginning of the recent drought. The live storage of Lake Powell on July 28, 2011 was 18.60 maf which is 76% of capacity. The elevation of Lake Powell is very near the peak elevation that will occur this year. Inflows to Lake Powell are steadily declining and by early August will be less than the release rate at Glen Canyon Dam. When this occurs, the elevation will gradually begin to decline and this condition will continue through the fall and winter months.
Current Dam Operations
Releases from Glen Canyon Dam are approximately 24,100 cubic feet per second (cfs) which is very near the full capacity of the power plant. The release volume for July will likely be approximately 1.485 maf. Releases in August will be similar to July with releases projected to be approximately 24,000 cfs. On August 2nd, 1 unit at Glen Canyon Dam will be out of service from approximately 7:00 am to 4:00 pm for a short term maintenance project. This will reduce the release rate during this period to approximately 20,000 cfs. At the end of August, releases will likely be gradually reduced to approximately 15,000 cfs as a transition to the Steady Flow Experiment to be conducted during September and October of 2011. This year will be the 4th year of a 5 year study of steady flows during September and October as describe in the 2008 Environmental Assessment and Finding of No Significant Impact. The target release rate for the steady flow experiment this year is approximately 15,000 cfs depending on the available capacity of Glen Canyon Power Plant.
While the release rate over the next several months is likely to be steady, the instantaneous releases from Glen Canyon Dam may fluctuate somewhat to provide 40 Mega Watts (MW) of system regulation. These instantaneous release adjustments maintain stable conditions within the electrical generation and transmission system and result in momentary release fluctuations within a range of about 1100 cfs above or below the targeted hourly release rate. The momentary fluctuations for regulation are very short lived and typically balance out over the hour.
Spinning and non-spinning reserve generation is also maintained at Glen Canyon Dam. In order for Colorado River Storage Project (CRSP) power plants to participate in the electrical generation and transmissions system, these powerplants must maintain a level of generation capacity available in reserve to assist the local control area for when unanticipated generation outages occur. The current CRSP power plant reserve requirement is 100 MW (equivalent to approximately 2,675 cfs of release from Glen Canyon Dam). When an electrical outage occurs within the control area, CRSP power plants can be called upon to provide up to 100 MW of additional generation for up to 2 hours. Under normal circumstances, calls for reserves infrequent and for much less than the required 100 MW. Because Glen Canyon Power plant is the largest facility of the CRSP power plants, most of the CRSP reserve requirement is maintained at Glen Canyon Dam.
Annual Operations-Coordinated Operation of Lake Mead and Lake Powell under Interim Guidelines for Water Year 2011
In August of 2010, the 24-Month Study was used to project the January 1, 2010 elevations of Lake Powell and Lake Mead. Based on these projected elevations and pursuant to the December 2007 Record of Decision on Colorado River Interim Guidelines for Lower Basin Shortages and the Coordinated Operations of Lake Powell and Lake Mead (Interim Guidelines), the operating tier for water year 2011 was selected to be Upper Elevation Balancing. Operation of Glen Canyon Dam under Upper Elevation Balancing can result in annual releases as low as 7.0 maf to as high as 13 maf or greater depending on system conditions. The operational outcome of the Upper Elevation Balancing Tier is largely dependent on system conditions at the end of the water year that are projected in the April 24-Month Study.
The April 2011 24-Month Study projected the end of water year elevation for Lake Powell would be above 3643 feet which is the Equalization Level for 2011. For this reason, pursuant to the Interim Guidelines, Equalization will govern the operation of Glen Canyon Dam for the remaining months of water year 2011. For more information on the Interim Guidelines click here:
The Water Supply forecast for Lake Powell (April through July Unregulated Inflow Volume) is 12.0 maf (151% of average) and the water year unregulated inflow to Powell for 2011 is projected to be 16.2 maf (135% of average). The unregulated inflow forecasts for Lake Powell over the next 3 months are as follows: July-4,000 kaf (257% of average); August-1,000 kaf (162% of average): September-670 kaf (141% of average). These forecasts were last updated on July 15, 2011. Incorporating these new forecasts, the projected most probable unregulated inflow for water year 2011 is now 16.7 maf (139% of average). This is the median projection for water year 2011. There is a 50% chance that the actual volume could be higher and there is a 50% the actual volume could be lower than this projected volume.
The July 24-Month Study projected a Lake Powell WY 2011 annual release volume of 12.45 maf. Due to recent increases to the inflow forecast for Lake Powell, Equalization may not be fully achieved by the end of the water year. The projected Lake Powell releases will be updated each month to reflect changing hydrology in order to achieve the operation specified by the Equalization Tier.
The July 2011 24-Month Study has been published and will be available here:
The Upper Colorado River Basin has experienced a protracted multi-year drought since early 2000. During this drought, the inflows to Lake Powell have been below average in every year except water years 2005, 2008 and likely 2011. In the summer of 1999, Lake Powell was close to full with reservoir storage at 23.5 million acre-feet, or 97 percent of capacity. During the next 5 years (2000 through 2004) unregulated inflow to Lake Powell was well below average. This resulted in Lake Powell storage decreasing during this period to 8.0 million acre-feet (33 percent of capacity) which occurred on April 8, 2005.
During 2005, 2008 and 2009, drought conditions eased somewhat with near or above average inflow conditions and net gains in storage to Lake Powell. This year (2011) will likely be another above average inflow year. As of July 28, 2011 the storage in Lake Powell was approximately 18.60 million acre-feet (76.0 % of capacity) which is still below the desired operating level for this time of year. The overall reservoir storage in the Colorado River Basin as of July 28, 2011 is approximately 39.20 million acre-feet (65.9 % of capacity).
RRFW thanks Rick Clayton of the USBOR for this information.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ RIVERWIRE is a free service to the community of river lovers from River Runners for Wilderness. To join, send an e-mail address to riverwire@rrfw.org and we’ll add it to the RRFW RIVERWIRE e-mail alerts list.
Wooo Hooo! Anyone been into Cataract Canyon this season? Photos?
(175% of average). This was below the forecasted volume for June, which was > 6.1 maf (198% of average) but was still the third wettest June on record > since the closure of Glen Canyon Dam. The observed inflow to Lake Powell > peaked on June 11th and 12th at just over 96,000 cfs. Inflows are now > declining but are still averaging about 80,000 cfs (as of July 5, 2011). The > forecasted unregulated inflow volume for July was increased from 3.30 maf to > 3.53 maf (226% of average) which would be the 3rd wettest July for Lake > Powell since the operation of Glen Canyon Dam began in 1963.
RRFW Riverwire Glen Canyon Dam Update July 8, 2011
Glen Canyon Dam Lake Powell
The unregulated inflow volume to Lake Powell for June 2011 was 5.40 maf (175% of average). This was below the forecasted volume for June, which was 6.1 maf (198% of average) but was still the third wettest June on record since the closure of Glen Canyon Dam. The observed inflow to Lake Powell peaked on June 11th and 12th at just over 96,000 cfs. Inflows are now declining but are still averaging about 80,000 cfs (as of July 5, 2011). The forecasted unregulated inflow volume for July was increased from 3.30 maf to 3.53 maf (226% of average) which would be the 3rd wettest July for Lake Powell since the operation of Glen Canyon Dam began in 1963.
The reservoir elevation of Lake Powell has increased significantly so far this runoff season. On April 9, 2011 the elevation of Lake Powell was 3609.7 feet above sea level which was the lowest elevation observed so far in 2011. Since that time the elevation of Lake Powell has increased by 42.7 feet to 3652.4 feet on July 5, 2011. The elevation is projected to continue to rise and should peak near 3660 by the end of July. The last time Lake Powell’s reservoir elevation was at this level was in October of 2001 (over 10 years ago) near the beginning of the recent drought.
Current Dam Operations
Releases from Glen Canyon Dam are approximately 24,400 cfs which is very near the full capacity of the powerplant. This release rate includes reserving enough generation capacity for up to 100 MW of reserve generation and 40 MW of system regulation. As the elevation of Lake Powell increases, the capacity of the powerplant will change and operation of Glen Canyon Dam will be adjusted daily to maximize release volumes. It is anticipated that the release volume for July will be approximately 1,465 kaf. The actual release volume for July will largely depend on generation unit efficiencies that occur throughout the month and could be higher or lower than this estimated release volume.
While the release rate over the next several months is likely to be steady, the instantaneous releases from Glen Canyon Dam may fluctuate somewhat to provide 40 MW of system regulation. These instantaneous release adjustments maintain stable conditions within the electrical generation and transmission system and result in momentary release fluctuations within a range of about 1100 cfs above or below the targeted hourly release rate. The momentary fluctuations for regulation are very short lived and typically balance out over the hour.
Spinning and non-spinning reserve generation is also maintained at Glen Canyon Dam. In order for Colorado River Storage Project (CRSP) powerplants to participate in the electrical generation and transmissions system, these powerplants must maintain a level of generation capacity available in reserve to assist the local control area for when unanticipated generation outages occur. The current CRSP powerplant reserve requirement is 100 MW (equivalent to approximately 2,675 cfs of release from Glen Canyon Dam). When an electrical outage occurs within the control area, CRSP powerplants can be called upon to provide up to 100 MW of additional generation for up to 2 hours. Under normal circumstances, calls for reserves infrequent and for much less than the required 100 MW. Because Glen Canyon Powerplant is the largest facility of the CRSP powerplants, most of the CRSP reserve requirement is maintained at Glen Canyon Dam.
Annual Operations-Coordinated Operation of Lake Mead and Lake Powell under Interim Guidelines for Water Year 2011
In August of 2010, the 24-Month Study was used to project the January 1, 2010 elevations of Lake Powell and Lake Mead. Based on these projected elevations and pursuant to the December 2007 Record of Decision on Colorado River Interim Guidelines for Lower Basin Shortages and the Coordinated Operations of Lake Powell and Lake Mead (Interim Guidelines), the operating tier for water year 2011 was selected to be Upper Elevation Balancing. Operation of Glen Canyon Dam under Upper Elevation Balancing can result in annual releases as low as 7.0 maf to as high as 13 maf or greater depending on system conditions. The operational outcome of the Upper Elevation Balancing Tier is largely dependent on system conditions at the end of the water year that are projected in the April 24-Month Study.
The April 2011 24-Month Study projected the end of water year elevation for Lake Powell would be above 3643 feet which is the Equalization Level for 2011. For this reason, pursuant to the Interim Guidelines, Equalization will govern the operation of Glen Canyon Dam for the remaining months of water year 2011. For more information on the Interim Guidelines click http://www.usbr.gov/lc/region/programs/strategies/RecordofDecision.pdf
Current Inflow Forecasts and Model Projections
The Water Supply forecast for Lake Powell (April through July Unregulated Inflow Volume) is 12.0 maf (151% of average) and the water year unregulated inflow to Powell for 2011 is projected to be 16.2 maf (135% of average). The unregulated inflow forecasts for Lake Powell over the next 3 months are as follows: July-3,530 kaf (226% of average); August-950 kaf (155% of average): September-670 kaf (141% of average). These forecasts were last updated on July 1, 2011. Incorporating these new forecasts, the projected most probable unregulated inflow for water year 2011 is now 16.2 maf (131% of average). This is the median projection for water year 2011. There is a 50% chance that the actual volume could be higher and there is a 50% the actual volume could be lower than this projected volume.
The June 24-Month Study projects a Lake Powell WY 2011 annual release volume of 12.44 maf. Due to recent increases to the inflow forecast for Lake Powell, Equalization may not be fully achieved by the end of the water year. The projected Lake Powell releases will be updated each month to reflect changing hydrology in order to achieve the operation specified by the Equalization Tier.
The Upper Colorado River Basin has experienced a protracted multi-year drought since early 2000. During this drought, the inflows to Lake Powell have been below average in every year except water years 2005, 2008 and likely 2011. In the summer of 1999, Lake Powell was close to full with reservoir storage at 23.5 million acre-feet, or 97 percent of capacity. During the next 5 years (2000 through 2004) unregulated inflow to Lake Powell was well below average. This resulted in Lake Powell storage decreasing during this period to 8.0 million acre-feet (33 percent of capacity) which occurred on April 8, 2005.
During 2005, 2008 and 2009, drought conditions eased somewhat with near or above average inflow conditions and net gains in storage to Lake Powell. This year (2011) will likely be another above average inflow year. As of July 5, 2011 the storage in Lake Powell was approximately 17.52 million acre-feet (72.0 % of capacity) which is still below the desired operating level for this time of year. The overall reservoir storage in the Colorado River Basin as of July 5, 2011 is approximately 37.48 million acre-feet (63.0 % of capacity).
RRFW thanks Rick Clayton of the USBOR for this information.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ RIVERWIRE is a free service to the community of river lovers from River Runners for Wilderness. To join, send an e-mail address to riverwire@rrfw.org and we’ll add it to the RRFW RIVERWIRE e-mail alerts list.
RRFW Riverwire – Glen Canyon Dam Update June 8, 2011
Glen Canyon Dam Lake Powell
The unregulated inflow volume to Lake Powell for May 2011 was been 2.35 million acre feet (maf) (102% of average). Inflows have increased due to snowmelt runoff within the basin and observed inflows to Lake Powell are averaging nearly 75,000 cubic feet per second (cfs). Observed inflows will likely continue to increase in June and could reach levels near 140,000 cfs by late June. The spring runoff is well under way and there is still significant snow yet to melt at the higher elevations within the basin. Inflows will likely be very high over the next 2 months. The forecasted unregulated inflow for June is 6.1 maf which would be the 2nd wettest June for Lake Powell since the initial operation of Glen Canyon Dam began in 1963.
The elevation of Lake Powell will increase significantly during the months of June and July, 2011. As of June 7, 2011 the elevation of Lake Powell was 3628.4 feet which is about 19 feet above the low elevation of the year (3609.7 feet on April 9, 2011). During June and July, the elevation will likely increase rapidly and is projected to reach a peak elevation for the year in early August 2011 of approximately 3660 to 3665 feet above sea level. This would be 35 to 40 feet below the full pool elevation of 3700 feet. The last time Lake Powell was at an elevation in this range was in October of 2001 near the beginning of the most current drought.
Current Dam Operations
The releases from Glen Canyon Dam are approximately 22,400 cfs which is very near the full capacity of the power plant allowing for 100 megawatts of reserve generation and 40 megawatts of regulation. As the elevation of Lake Powell increases, the capacity of the power plant will also increase and operation of the power plant will be adjusted day by day to release the maximum volume possible. It is anticipated that the release volume for June will be approximately 1,369 kaf with 7 generating units operating at full capacity. The actual release volume for June will largely depend on the generation unit efficiencies that occur throughout the month and could be higher or lower than this anticipated volume.
While the release rate over the next several months is likely to be steady at or near full power plant capacity, the instantaneous releases from Glen Canyon Dam may fluctuate somewhat to provide approximately 40 megawatts of system regulation. These instantaneous release adjustments maintain stable conditions within the electrical generation and transmission system and result in momentary release fluctuations within a range of about 1100 cfs above or below the targeted hourly release rate. The momentary fluctuations for regulation are very short lived and typically balance out over the hour.
Spinning and non-spinning reserve generation is also maintained at Glen Canyon Dam. In order for Colorado River Storage Project (CRSP) power plants to participate in the electrical generation and transmissions system, these dams must maintain a level of generation capacity in reserve to assist the local control area to maintain electrical supply when unanticipated generation outages occur within the control area. The CRSP power plants are required to maintain 100 megawatts (approximately 2,675 cfs of release) of capacity in reserve for these unanticipated outages. When an electrical outage occurs, CRSP power plants can be called upon to provide up to an additional 100 megawatts of generation above what was originally scheduled for a duration of 2 hours or less. Under normal circumstances, calls for reserve generation occur fairly infrequently and are for much less than the required 100 megawatts. Because Glen Canyon Power plant is the largest facility of the CRSP power plants, typically most of the CRSP reserve requirement is maintained there rather than the other CRSP power plants.
Annual Operations-Coordinated Operation of Lake Mead and Lake Powell under Interim Guidelines for Water Year 2011
In August of 2010, the 24-Month Study was used to project the January 1, 2010 elevations of Lake Powell and Lake Mead. Based on these projected elevations and pursuant to the December 2007 Record of Decision on Colorado River Interim Guidelines for Lower Basin Shortages and the Coordinated Operations of Lake Powell and Lake Mead (Interim Guidelines), the operating tier for water year 2011 was selected to be Upper Elevation Balancing. Operation of Glen Canyon Dam under Upper Elevation Balancing can result in an annual release as low as 7.0 maf when balancing or as high as would be required to achieve Equalization which could be as low as 8.23 maf or as high as 13 maf or greater depending on system conditions. The operational outcome of Upper Elevation Balancing is largely dependent on system conditions at the end of the water year that are projected in the April 24-Month Study. For more information on the Interim Guidelines click here: http://www.usbr.gov/lc/region/programs/strategies/RecordofDecision.pdf
Current Inflow Forecasts and Model Projections
Snowpack conditions above Lake Powell that occurred during the winter of 2010-2011 were well above average and resulted in a snowpack condition above Lake Powell on April 10, 2011 that was 119% of average. Typically the snowpack peaks during the first part of April and snow levels normally begin to decrease after about April 10th each year. Temperatures in April of 2011, however, were well below average which allowed the snowpack to continue to build through the month of April. On May 1, 2011 the snowpack above Lake Powell reached its peak level for the year which was approximately 130% of the average seasonal peak snowpack condition. Below average temperatures in the basin persisted in May and by June 1, 2011 only about 30% of the snowpack had melted. The as of June 8, 2011 about 50% of the accumulated snowpack for 2011 had melted. There is still significant snowpack within the basin which will support high inflow conditions for several months.
The Water Supply forecast for Lake Powell (April through July Unregulated Inflow Volume) is now 12.6 maf (159% of average) and the water year unregulated inflow to Powell for 2011 is projected to be 16.7 maf (138% of average). The last water year where Lake Powell observed that level of unregulated inflow was 1997 when the unregulated inflow volume was 17.4 maf (145% of average) and only 5 of 47 years since the closure of Glen Canyon Dam have had unregulated inflow volumes greater than what is projected for this year.
The unregulated inflow forecast for Lake Powell over the next 3 months based on the May preliminary Water Supply forecast is as follows: June-6,100 kaf (198% of average); July-3,300 kaf (212% of average); August-950 kaf (155% of average). This forecast was last updated on June 3, 2011. Incorporating these new forecasts the most probable Lake Powell unregulated inflow volume projection for water year 2011 is 16.7 maf (138% of average). This is the median unregulated inflow volume that is forecasted to occur for water year 2011. There is a 50% chance that the unregulated inflow volume will be higher or lower than this volume. A reasonable range of possible inflows is defined by a minimum probable inflow volume and a maximum probable inflow volume. These volumes represent what would be expected to be achieved or exceeded 90% of the time (minimum inflow volume) and 10% of the time (maximum inflow volume). The forecasted water year (2011) minimum probable inflow volume issued for May is 15.1 maf (125% of average). The forecasted water year (2011) maximum probable inflow volume issued for May is 18.5 maf (154% of average). Given this range, there is still a significant amount of uncertainty for how 2011 will play over the next 4 months.
The May 2011 24-Month Study, with the 2011 most probable inflow condition projected the annual release volume to be 12.46 maf. This release volume is the estimated maximum volume that can be released through Glen Canyon Power plant by September 30, 2011. This annual release volume does not achieve the Equalization objective of the Interim Guidelines by September 30th, 2011. As hydrologic conditions change during the remainder of water year 2011, actual and projected releases from Glen Canyon Dam will be adjusted to achieve the Equalization objective of the Interim Guidelines as practicably as is possible by September 30th, 2011. If the Equalization objective is not achieved by September 30th, releases from Glen Canyon Dam will likely remain at power plant capacity until the Equalization objective is achieved.
In the Upper Colorado River Basin during water year 2010, the overall precipitation accumulated through September 30, 2010 was approximately 90% of average based on the 30 year average for the period from 1971 through 2000. For Water Year 2011 thus far, the estimated monthly precipitation within the Upper Colorado River Basin (above Lake Powell) as a percentage of average has been: (October – 135%, November – 95%, December – 225%, January – 50%, February – 100%, March – 85%, April – 155%, May – 155%)
The Climate Prediction Center outlook (dated May 19, 2011) for temperature over the next 3 months indicates that temperatures in the Upper Colorado River Basin are expected to be above average while precipitation over the next 3 months is projected to be near average in the northern reaches of the basin while below average in the southern reaches of the basin.
Upper Colorado River Basin Drought
The Upper Colorado River Basin has experienced a protracted multi-year drought since early 2000. During this drought, the inflows to Lake Powell have been below average in every year except water years 2005, 2008 and likely 2011. In the summer of 1999, Lake Powell was close to full with reservoir storage at 23.5 million acre-feet, or 97 percent of capacity. During the next 5 years (2000 through 2004) unregulated inflow to Lake Powell was well below average. This resulted in Lake Powell storage decreasing during this period to 8.0 million acre-feet (33 percent of capacity) which occurred on April 8, 2005. During 2005, 2008 and 2009, drought conditions eased somewhat with near or above average inflow conditions and net gains in storage to Lake Powell. 2011 will be another above average inflow year so drought conditions have eased somewhat in the Colorado River Basin over the past 6 years. As of June 7, 2011 the storage in Lake Powell was approximately 14.68 million acre-feet (60.4 % of capacity) which is still below desired levels. The overall reservoir storage in the Colorado River Basin as of June 7, 2011 is approximately 33.82 million acre-feet (56.9 % of capacity).
RRFW thanks Rick Clayton of the USBOR for this information.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ RIVERWIRE is a free service to the community of river lovers from River Runners for Wilderness. To join, send an e-mail address to riverwire@rrfw.org and we’ll add it to the RRFW RIVERWIRE e-mail alerts list.
RRFW Riverwire – Glen Canyon Dam Update May 9, 2011
Glen Canyon Dam / Lake Powell
The unregulated inflow to Lake Powell for April 2011 was 983 thousand acre feet (kaf) (100% of average) which was 117 kaf below the level forecasted for April by the Colorado Basin River Forecast Center which was 1100 kaf (112% of average). On April 9, 2011, the elevation of Lake Powell reached 3609.7 feet above sea level which will likely be the lowest level that occurs during water year 2011. As of May 2, 2011 the elevation had increased to 3612.1 feet above sea level. Inflows are averaging about 25,000 cfs while releases are averaging about 14,400 cfs so the elevation is increasing at over 1 inch per day. It is projected that the elevation of Lake Powell could increase by more than 40 feet to a peak elevation of approximately 3655 feet above sea level by late July or early August which would be approximately 45 feet from the full pool elevation of 3700 feet.
Current Dam Operations
The release volume currently scheduled for May is 1103 kaf. Releases in May, from May 1 through May 13 will be near steady at 14,400 cfs. On May 14, 2011 it is projected that Units 3 and 4 will be returned to service. When this occurs, releases from Glen Canyon Dam will be increased such that daily peak releases will be about 22,000 cfs and off peak releases will be about 16,000 cfs.
The projected release volume for June is currently projected to be 1398 kaf to 1458 kaf. Flows in June will likely be steady, with releases between 23,500 cfs and 24,500 cfs during June in all hours. This will be the estimated power plant capacity during that month based on unit performance.
In addition to daily operations that may or may not include daily fluctuation patterns for load following power generation, the instantaneous releases from Glen Canyon Dam may also fluctuate somewhat to provide approximately 40 megawatts of system regulation. These instantaneous release adjustments maintain stable conditions within the electrical generation and transmission system and result in momentary release fluctuations within a range of about 1100 cfs above or below the targeted hourly release rate. The momentary fluctuations for regulation are very short lived and typically balance out over the hour.
Spinning and non-spinning reserve generation is also maintained at Glen Canyon Dam. In order for Glen Canyon Dam (and other Colorado River Storage Project dams) to participate in the electrical generation and transmissions system, Glen Canyon Dam must provide a level of reserve generation to assist the local control area to maintain electrical supply when unanticipated generation unit outages occur within the control area. Glen Canyon is required to maintain 99 megawatts (approximately 2,650 cfs of release) of capacity in reserve for these unanticipated outages. When an electrical outage occurs, Glen Canyon Dam can be called upon to provide up to an additional 99 megawatts of generation above what was originally scheduled for Glen Canyon Dam for a duration of 2 hours or less. Under normal circumstances, calls for reserve generation occur fairly infrequently and are for much less than the required 99 megawatts.
Annual Operations-Coordinated Operation of Lake Mead and Lake Powell under Interim Guidelines for Water Year 2011
In August of 2010, the 24-Month Study was used to projected the January 1, 2010 elevations of Lake Powell and Lake Mead. Based on these projected elevations and pursuant to the December 2007 Record of Decision on Colorado River Interim Guidelines for Lower Basin Shortages and the Coordinated Operations of Lake Powell and Lake Mead (Interim Guidelines), the operating tier for water year 2011 was selected to be Upper Elevation Balancing. Operation of Glen Canyon Dam under Upper Elevation Balancing can result in an annual release as low as 7.0 million acre feet (maf) when Balancing or as high as would be required to achieve Equalization which could be as low as 8.23 maf or as high as 13 maf or greater depending on system conditions. The operational outcome of Upper Elevation Balancing is largely dependent on system conditions at the end of the water year that are projected in the April 24-Month Study. For more information on the Interim Guidelines see:
Snowpack conditions above Lake Powell have persisted to be above average since late December 2010. The overall snowpack above Lake Powell on May 2, 2011 was 160% of the seasonal average. The snowpack conditions have continued to build basin wide throughout April when typically snowpack begins to melt in April. Temperatures in the Colorado River Basin have remained below average and this has protected the snowpack beyond what was expected just one month ago. The Water Supply forecast for Lake Powell (April through July Unregulated Inflow Volume) was 9.7 maf (123% of average) at mid-April but has been increased substantially for May which is now 11.5 maf (145% of average). The 2011 water year projected unregulated inflow volume was projected in April to be 13.11 maf (109% of average). With the increased forecast for May the updated 2011 water year projected unregulated inflow volume is now 15.34 maf (127% of average). The last water year where Lake Powell observed that level of unregulated inflow was 1996 when the unregulated inflow volume was 17.05 maf (142% of average) and in the 47 years since the closure of Glen Canyon Dam there have only been 8 years where the unregulated inflow volume was at or above the level projected for this year.
The unregulated inflow forecast for Lake Powell over the next 3 months based on the May preliminary Water Supply forecast is as follows: May-3,000 kaf (130% of average); June-5,200 kaf (169% of average); July-2,300 kaf (148% of average). Incorporating these new forecasts the most probable Lake Powell unregulated inflow volume projection for water year 2011 is 15.34 maf (127% of average). This is the median unregulated inflow volume that is forecasted to occur for water year 2011. There is a 50% chance that the unregulated inflow volume will be higher or lower than this volume. A reasonable range of possible inflows is defined by a minimum probable inflow volume and a maximum probable inflow volume. These volumes represent what would be expected to be achieved or exceeded 90% of the time (minimum inflow volume) and 10% of the time (maximum inflow volume). The forecasted water year (2011) minimum probable inflow volume issued for May is 12.4 maf (103% of average). The forecasted water year (2011) maximum probable inflow volume issued for May is 18.1 maf (150% of average). Given this range, there is still a significant amount of uncertainty for how 2011 will play over the next 5 months.
The April 2011 24-Month Study, with the 2011 most probable inflow condition projects that Equalization will be required under the Interim Guidelines and the projected annual release volume from this study is projected to be 11.56 maf. The increased forecast will almost certainly increase the projected annual release volume when the May 24-month study is completed. As hydrologic conditions change during the remainder of the water year, this annual release volume projection will be adjusted to achieve the objectives of the Equalization Tier of the Interim Guidelines.
The April 2011 24-Month Study has been published and is available here:
In the Upper Colorado River Basin during water year 2010, the overall precipitation accumulated through September 30, 2010 was approximately 90% of average based on the 30 year average for the period from 1971 through 2000. For Water Year 2011 thus far, the estimated monthly precipitation within the Upper Colorado River Basin (above Lake Powell) as a percentage of average has been: (October – 135%, November – 95%, December – 225%, January – 50%, February – 100%, March – 90%)
The Climate Prediction Center outlook (dated April 21, 2010) for temperature over the next 3 months indicates that temperatures in the Upper Colorado River Basin are expected to be above average while precipitation over the next 3 months is projected to be near average in the northern reaches of the basin while below average in the southern reaches of the basin.
Upper Colorado River Basin Drought
The Upper Colorado River Basin continues to experience a protracted multi-year drought. Since 1999, inflow to Lake Powell has been below average in every year except water years 2005 and 2008. In the summer of 1999, Lake Powell was close to full with reservoir storage at 23.5 million acre-feet, or 97 percent of capacity. During the next 5 years (2000 through 2004) unregulated inflow to Lake Powell was well below average. This resulted in Lake Powell storage decreasing during this period to 8.0 million acre-feet (33 percent of capacity) which occurred on April 8, 2005. During 2005, 2008 and 2009, drought conditions eased somewhat with near or above average inflow conditions and net gains in storage to Lake Powell. 2011 will be another above average inflow year so drought conditions are easing somewhat in the Colorado River Basin. As of May 2, 2011 the storage in Lake Powell was approximately 12.95 million acre-feet (53.2 % of capacity) which is below desired levels. The overall reservoir storage in the Colorado River Basin as of April 18, 2011 is approximately 31.58 million acre-feet (53.1 % of capacity).
RRFW thanks Rick Clayton of US Bureau of Reclamation for this update.
RIVERWIRE is a free service to the community of river lovers from River Runners for Wilderness. To join, send an e-mail address to riverwire@rrfw.org and we’ll add it to the RRFW RIVERWIRE e-mail alerts list.
RRFW Riverwire – Glen Canyon Dam Update April 8, 2011
Glen Canyon Dam / Lake Powell
The unregulated inflow to Lake Powell for March 2011 was 594 kaf (90% of average). Observed inflows to Lake Powell have increased over the past several weeks and are currently averaging about 10,400 cfs. With daily average release rate from Glen Canyon Dam that is about 16,000 cfs, the elevation of Lake Powell is still declining , but the rate of decline has been moderated by these increased inflow conditions. The elevation of Lake Powell at midnight on April 7, 2011 was 3609.84 feet above sea level (90.16 feet from full pool). The elevation of Lake Powell will begin to increase later in April when inflows exceed releases. It is projected that the elevation of Lake Powell could increase by more than 30 feet to a peak elevation of approximately 3643 feet above sea level by late July or early August.
Current Dam Operations
The release volume scheduled for April is 966 kaf. During the first 3 days of April, daily releases fluctuates for power production between an afternoon peak of approximately 19,600 cfs and an early morning low release of approximately 14,000 cfs. On April 4, 2011, Glen Canyon Powerplant Units 3 and 4 were taken out of service for approximately 6 weeks for annual maintenance. Releases from Glen Canyon Dam were set to 16,000 cfs with no fluctuations for power generation at that time due to limited capacity of the available generating units at Glen Canyon Power Plant. Releases of 16,000 cfs steady will likely continue until the end of April. In early May, releases will likely be steady at about 15,000 cfs for the first 13 days of the month. On May 14, 2011 it is projected that Units 3 and 4 will be returned to service. When this occurs, releases from Glen Canyon Dam will be increased such that peak releases will be about 22,000 cfs and off peak releases will be about 16,000 cfs. The projected release volume for May is approximately 1.10 maf.
In addition to daily operations that may or may not include daily fluctuation patterns for load following power generation, the instantaneous releases from Glen Canyon Dam may also fluctuate somewhat to provide approximately 40 megawatts of system regulation. These instantaneous releases adjustments maintain stable conditions within the electrical generation and transmission system and result in momentary release fluctuations within a range that is about 1100 cfs above or below the targeted release rate for a given hour of the day. These momentary fluctuations for regulation are very short lived and typically balance out over the hour. Spinning and non-spinning reserve generation can also occur at Glen Canyon Dam. When an unanticipated electrical outage event occurs within the electrical transmission system, reserve generation at Glen Canyon Dam can be called upon up to a maximum of 98 megawatts (approximately 2,600 cfs of release) for a duration of up to 2 hours. Under normal circumstances, calls for reserve generation occur fairly infrequently and are for much less than the required 98 megawatts.
Annual Operations-Coordinated Operation of Lake Mead and Lake Powell under Interim Guidelines for Water Year 2011
In August of 2010, the 24-Month Study model projected the January 1, 2010 elevation of Lake Powell and Lake Mead under the most probable inflow scenario. Pursuant to the December 2007 Record of Decision on Colorado River Interim Guidelines for Lower Basin Shortages and the Coordinated Operations of Lake Powell and Lake Mead (Interim Guidelines) and based on this August projection, the operational tier for water year 2011 was selected to be the Upper Elevation Balancing Tier. Under this operational tier, there is a possibility that the annual release volume from Lake Powell could be as low as 8.23 maf and there is also a possibility under this tier that Equalization or Balancing could occur which would result in an annual release volume greater than 8.23 maf.
The possibility of Equalization or Balancing in water year 2011 is dependent upon the reservoir conditions of Lake Powell and Lake Mead projected at the end of the water year in the Most Probable April 24-Month Study when the projected Glen Canyon Dam annual release condition is 8.23 maf . The April 24-Month Study, with a projected water year release of 8.23 maf projects the elevation of Lake Powell on September 30, 2011 (end of water year 2011) to be 3662.63 feet above sea level which is above the Equalization Level for 2011 (3643 feet). Based on this model projection and consistent with the Interim Guidelines, the Equalization Tier will govern the operation of Lake Powell for the remainder of water year 2011.
Current Inflow Forecasts and Model Projections
Snowpack conditions above Lake Powell have persisted to be above average since late December 2010. The overall snowpack above Lake Powell on April 7, 2011 was 115% of average. The current Water Supply forecast for Lake Powell (April through July Unregulated Inflow Volume) is 9.5 maf (120% of average) and this forecast was issued by the CBRFC on April 4, 2011.
The unregulated inflow forecast for Lake Powell over the next 3 months is as follows: April-1,100 kaf (112% of average); May-3,000 kaf (130% of average); June-3,850 kaf (125% of average). Incorporating these new forecasts with the current Water Supply forecast, the projected unregulated inflow volume to Lake Powell during water year 2011 is now 13.11 maf (109% of average). These forecasts combined with projected inflows in August and September of 2011 make up the 2011 Most Probable water year inflow condition. The Most Probable inflow condition has a statistical probability of being achieved that is 50%. In other words, there is a 50% chance that the unregulated inflow volume for water year 2011 for Lake Powell will be 13.11 maf or greater.
A Minimum Probable water year inflow conditions has also been developed for water year 2011. The Minimum Probable inflow condition has a statistical probability of being achieved that is 90%. The 2011 Minimum Probable water year inflow condition is currently 10.5 maf (87% of average). A Maximum Probable water year inflow condition has also been developed for water year 2011. The 2011 Maximum Probable inflow condition is currently 16.2 maf (135% of average).
The April 2011 24-Month Study, with the 2011 Most Probable inflow condition projects that Equalization will be required under the Interim Guidelines and the projected annual release volume is projected to be 11.56 maf. As hydrologic conditions change during the remainder of the water year, this annual release projection will be adjusted to achieve the Equalization Tier of the Interim Guidelines.
Upper Colorado River Basin Hydrology
In the Upper Colorado River Basin during water year 2010, the overall precipitation accumulated through September 30, 2010 was approximately 90% of average based on the 30 year average for the period from 1971 through 2000. For Water Year 2011 thus far, the estimated monthly precipitation within the Upper Colorado River Basin (above Lake Powell) as a percentage of average has been: (October – 135%, November – 95%, December – 225%, January – 50%, February – 100%, March- 90%)
The Climate Prediction Center outlook (dated March 17, 2010) for temperature over the next 3 months indicates that temperatures in the Upper Colorado River Basin are expected to be above average while precipitation over the next 3 months is projected to be near average in the northern reaches of the basin while below average in the southern reaches of the basin.
Upper Colorado River Basin Drought
The Upper Colorado River Basin continues to experience a protracted multi-year drought. Since 1999, inflow to Lake Powell has been below average in every year except water years 2005 and 2008. In the summer of 1999, Lake Powell was close to full with reservoir storage at 23.5 million acre-feet, or 97 percent of capacity. During the next 5 years (2000 through 2004) unregulated inflow to Lake Powell was well below average. This resulted in Lake Powell storage decreasing during this period to 8.0 million acre-feet (33 percent of capacity) which occurred on April 8, 2005. During 2005, 2008 and 2009, drought conditions eased somewhat with net gains in storage to Lake Powell. As of April 7, 2011 the storage in Lake Powell was approximately 12.71 million acre-feet (52.2 % of capacity) which is below desired levels. The overall reservoir storage in the Colorado River Basin as of April 7, 2011 is approximately 31.42 million acre-feet (52.8 % of capacity).
RRFW thanks Rick Clayton, US Bureau of Reclamation for this update.
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RRFW Riverwire – Glen Canyon Dam Update January 11, 2011
Glen Canyon Dam – Lake Powell
During December 2010 the unregulated inflow to Lake Powell was 417 thousand acre feet (kaf) (96% of average). This was 57 kaf above the volume forecasted by the Colorado Basin River Forecast Center (CBRFC) on December 1, 2010 which was 360 kaf (83% of average). The elevation of Lake Powell at the end of the day on December 31, 2010 was 3626.54 feet above sea level (73.46 feet from full pool) which corresponds to a live storage content of 14.44 maf (59.5% of capacity).
During the last half of December, precipitation within the Upper Colorado River Basin was well above average and the snowpack conditions have increased significantly. On December 17, 2010 the snowpack above Lake Powell was estimated to be 102% of average. By December 31, 2010 the snowpack conditions above Lake Powell had increased to an estimated 151% of average. Precipitation above Lake Powell for the first 3 months of water year 2011 has been well above average at nearly 150% of average.
Based on these conditions and projected climate conditions over the next several months, the CBRFC has issued the Final Water Supply Forecast (April through July 2011 forecasted unregulated inflow volume) for Lake Powell that is well above average at 9.5 million acre feet (maf) which is 120% of average. This forecast translates into an increase to the expected inflow to Lake Powell for water year 2011 that is more than 3 million acre-feet more than what was projected one month ago.
Operation of Glen Canyon Dam during January 2011 has been modified based on this new forecast. On Sunday January 9, 2011, releases from Glen Canyon Dam were increased to an average daily release volume of approximately 34,000 acre-feet which translates to an average daily release of 17,100 cfs. Releases are scheduled to peak for power generation during the afternoon hours for the remainder of January to 20,500 cfs. Releases during the early morning hours are approximately 12,500 cfs.
The release volume for February is projected to be 981,000 kaf which the estimated capacity of Glen Canyon Power plant under the scheduled maintenance unit outage plan with an allowance of capacity to provide spinning reserves and regulation. It is anticipated that fluctuations for power generation will be minimal in February and the estimated release rate will likely be approximately 17,600 cfs.
In addition to the daily fluctuation pattern for power generation, the instantaneous releases from Glen Canyon Dam may also fluctuate somewhat to provide approximately 40 megawatts of system regulation. These instantaneous releases adjustments maintain stable conditions within the electrical generation and transmission system and result in momentary release fluctuations within a range that is about 1100 cfs above or below the targeted release rate for a given hour of the day. These momentary fluctuations for regulation are very short lived and typically balance out over the hour. Spinning and non-spinning reserve generation is also maintained at Glen Canyon Dam. When an unanticipated electrical outage event occur within the electrical transmission system, this reserve generation at Glen Canyon Dam can be called upon up to a limit of 98 megawatts (approximately 2,600 cfs of release) for a duration of up to 2 hours. Under normal circumstances, calls for reserve generation occur fairly infrequently and are for much less than the limit of 98 megawatts.
In August of 2010, the August 2010 24-Month Study Model was used to project the January 1, 2010 elevation of Lake Powell and Lake Mead under the most probable inflow scenario. Pursuant to the Interim Guidelines and based on this August projection, the operational tier for water year 2011 was determined to be the Upper Elevation Balancing Tier. Under the Upper Elevation Balancing Tier, there is a possibility that the annual release volume from Lake Powell could be 8.23 maf. There is also a possibility under this tier that Equalization or Balancing could occur in 2011 which would result in an annual release volume greater than 8.23 maf.
The possibility of Equalization or Balancing in 2011 is dependent on the end of water year 2011 reservoir conditions projected in the April 2011 24-Month Study under the most probable inflow scenario and with 8.23 maf projected for release from Lake Powell during water year 2011. For this reason it will not be known for certain whether Equalization or Balancing will occur in water year 2011 until April 2011. 24-Month Studies prior to April 2011 can project that Equalization or Balancing are likely to occur, but these projections are subject to change with changes in the forecasted hydrology of the Colorado River Basin. It is possible that a relatively small change in forecasted hydrology can have a large impact on the projected annual release volume.
The January 2011 24-Month Study with the most probable inflow scenario for water year 2011 projects that Equalization is likely to occur in 2011. For this reason, the projected most probable annual release volume for water year 2011 in the January 24-Month Study is 11.367 maf. Given the current range of uncertainty of the forecasted hydrology for water year 2011, it is possible that Balancing could also occur in water year 2011 which would result if the annual release being 9.0 maf. Each month the 24-Month Study is updated to reflect the most probable inflow scenario which is based on the most recent forecast from the Colorado River Basin Forecast Center (CBRFC). Analysis of the probable range of inflows that could occur during water year 2011 indicates that the probability of realizing an inflow volume that would trigger Equalization in 2011 is currently about 76%. This probability will be updated again during the first part of February 2011.
The unregulated inflow forecast for Lake Powell over the next 3 months is as follows: January-380 kaf (94% of average); February-380 kaf (90% of average); March-670 kaf (101% of average). The outlook for water year 2011, incorporating this new forecast and the January Final Water Supply Forecast, the most probable unregulated inflow volume to Lake Powell during water year 2011 is now 13.19 maf (110% of average). It is possible that the unregulated volume of inflow to Lake Powell in water year 2011 will be greater than or less than the most probable projection. The probable range of unregulated inflow volumes to Lake Powell during water year 2011 is currently projected to be as dry as 8.9 maf (74% of average) to as wet as 18.6 maf (154% of average).
Upper Colorado River Basin Hydrology
In the Upper Colorado River Basin during water year 2010, the overall precipitation accumulated through September 30, 2010 was approximately 90% of average based on the 30 year average for the period from 1971 through 2000. For Water Year 2011 thus far, the estimated monthly precipitation within the Upper Colorado River Basin (above Lake Powell) as a percentage of average has been: (October – 135%, November – 95%,December -230%).
The Climate Prediction Center outlook (dated December 16, 2010) for temperature over the next 3 months indicates that temperatures in the Upper Colorado River Basin are expected to be near average while precipitation over the next 3 months is also projected to be near average.
Upper Colorado River Basin Drought
The Upper Colorado River Basin continues to experience a protracted multi-year drought. Since 1999, inflow to Lake Powell has been below average in every year except water years 2005 and 2008. In the summer of 1999, Lake Powell was close to full with reservoir storage at 23.5 million acre-feet, or 97 percent of capacity. During the next 5 years (2000 through 2004) unregulated inflow to Lake Powell was well below average. This resulted in Lake Powell storage decreasing during this period to 8.0 million acre-feet (33 percent of capacity) which occurred on April 8, 2005. During 2005, 2008 and 2009, drought conditions eased somewhat with net gains in storage to Lake Powell. As of January 10, 2011 the storage in Lake Powell was approximately 14.26 million acre-feet (58.6 % of capacity) which is below desired levels. The overall reservoir storage in the Colorado River Basin as of January 10, 2011 is approximately 32.29 million acre-feet (54.3 % of capacity).
RRFW thanks Rick Clayton of the USBOR for this update.
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RRFW Riverwire – Glen Canyon Dam Update November 7, 2012
Current Status
Releases from Glen Canyon Dam are currently averaging approximately 8,020 cubic feet per second (cfs) with fluctuations for hydropower generation between approximately 7,000 cfs (nighttime) and 9,000 cfs (daytime). The reservoir elevation is 3619.2 feet and declining.
On November 18-23, 2012, the Department of Interior will conduct the first High Flow Experiment under a multi-year High Flow Protocol announced earlier this year by Secretary Salazar. Under this Protocol, high flow releases are linked to sediment input and other resource conditions below Glen Canyon Dam.
Beginning on the evening of November 18th, releases from Glen Canyon Dam will begin ramping up to full power plant capacity (approximately 27,300 cfs). At midday on November 19th, bypass tubes at Glen Canyon Dam will be opened and releases will continue to increase up to full power plant and bypass capacity (approximately 42,300 cfs) by the evening of November 19th. Releases will be maintained at peak release for 24 hours and then begin ramping back down. Releases will return to normal operations in the evening of November 23rd. The entire experiment, including ramping is expected to last 5 days, with 24 hours at peak release.
November releases from Glen Canyon Dam prior to and after the High Flow Experiment are expected to fluctuate between 7,000cfs and 9,000cfs. The elevation of Lake Powell is expected to decrease approximately 2 ½ feet during the 5 day experiment. To view the most current reservoir elevation, content, inflow and release, click on: http://www.usbr.gov/uc/water/rsvrs/ops/crsp_40_gc.html
The unregulated inflow volume to Lake Powell in October was 189 thousand acre-feet (kaf) (37% of average). The release volume from Glen Canyon Dam in October was 498 kaf. The end of October elevation and storage of Lake Powell were 3619.5 feet (80.5 feet from full pool) and 13.71 million acre feet (maf) (56.4% of full capacity). The reservoir elevation is now declining.
The water year unregulated inflow volume for 2012 was 4.91maf (45.3% of average), placing the 2012 as the third lowest on record since the closure of Glen Canyon Dam in 1963. In terms of reservoir elevation and storage, Lake Powell reached its peak for water year 2012 on June 3rd at 3636.9 ft (63.1 feet from full pool) and 15.64 maf (64.3% of capacity), respectively.
Releases for Water Year 2012 totaled 9.466 maf. Pursuant to the 2007 Interim Guidelines, Lake Powell operated under the Equalization Tier in 2012, releasing 9.463 maf, which is 8.233 maf plus 1.233 maf (the Equalization release volume from 2011 that could not be achieved by September 30, 2011). Throughout water year 2012, Reclamation adjusted operations of Glen Canyon Dam to release the appropriate annual volume during 2012 to achieve Equalization objectives as practicably as possible by September 30, 2012.
Current Dam Operations
The operating tier for 2013 is the Upper Elevation Balancing Tier, as establish in August 2012 and pursuant to the Interim Guidelines. However, if hydrologic conditions and projections become wetter, it is possible that beginning in April, the Equalization tier will govern the operations of Lake Powell for the remainder of the water year. Based on analysis of a range of inflow scenarios, the current probability of realizing an inflow volume that would trigger Equalization in 2013 is approximately 20 percent. As hydrologic conditions for Lake Powell and Lake Mead change throughout the year, Reclamation will adjust operations of Glen Canyon Dam to release the appropriate annual volume during 2013 to achieve the governing operating tier objectives as practicably as possible by September 30, 2013.
Releases from Glen Canyon Dam in November in the days prior to and after the High Flow Experiment on November 18-23 will be approximately 8,020 cfs with daily fluctuations between 7,000cfs and 9,000cfs and are consistent with the Glen Canyon Operating Criteria (Federal Register, Volume 62, No. 41, March 3, 1997). The scheduled release volume for November, including the High Flow Experiment, is 724 kaf.
In December, the release volume will likely be about 800 kaf, with fluctuations throughout the day from about 8,250 cfs in the early morning to about 16,250 cfs in the early evening. In January, the release volume will likely be about 800 kaf with daily fluctuations for hydropower.
In addition to daily scheduled fluctuations for power generation, the instantaneous releases from Glen Canyon Dam may also fluctuate to provide 40 Megawatts (MW) of system regulation. These instantaneous release adjustments stabilize the electrical generation and transmission system and translate to a range of about 1,100 cfs above or below the hourly scheduled release rate. Typically, fluctuations for system regulation are very short lived and balance out over the hour and do not have noticeable impacts on downstream river flow conditions.
Releases from Glen Canyon Dam can also fluctuate beyond scheduled fluctuations for power generation when called upon as a partner that shares reserve requirements within the electrical generator community (i.e. balancing area). To provide system reliability, all participating electricity generators within the balancing area maintain a specified level of generation capacity (i.e. reserves) that can be called upon when an unscheduled outage occurs. Glen Canyon Dam typically maintains 43 MW of reserves (approximately 1,100 cfs) for this purpose. Reserve calls can be maintained for a maximum of 2 hours after which time the generation rate should be returned to the original schedule. If reserves from Glen Canyon Dam are called upon, releases from the dam can exceed scheduled levels and can have a noticeable impact on the river downstream from Glen Canyon Dam. Calls for reserves are fairly infrequent and typically are for much less than 43 MW.
Current Inflow Forecasts and Model Projections
The hydrologic outlook forecast for water year 2013 projects that the most probable (median) unregulated inflow volume will be 7.60 maf (70% of average based on the period 1981-2010). Based on this hydrologic outlook, the October 24-Month study projects the annual release volume for water year 2013 will be 8.23 maf and the end of water year reservoir elevation and storage for Lake Powell will be 3608.52 (91.48 feet from full pool) and 12.582 maf (51.7% capacity), respectively.
If hydrologic conditions and projections become wetter, it is possible that beginning in April, the Equalization tier will govern the operations of Lake Powell for the remainder of the water year and the release volume for 2013 could be greater than 8.23 maf. Based on analysis of a range of inflow scenarios, the current probability of realizing an inflow volume that would trigger Equalization in 2013 is approximately 20 percent.
Upper Colorado River Basin Hydrology
Since water year 2005, the Upper Colorado River Basin has experienced significant year to year hydrologic variability. The unregulated inflow to Lake Powell, which is a good measure of hydrologic conditions in the Colorado River Basin, has averaged a water year volume of 10.22 maf (94% of average (period 1981-2010)) during the period from 2005 through 2012. The hydrologic variability during this period has been from a low water year unregulated inflow volume of 4.91 maf (45% of average) in water year 2012 to a high water year unregulated inflow volume of 15.97 maf (147% of average) in water year 2011. Based on observed inflows and current forecasts, water year 2013 unregulated inflow is expected to be 7.59 maf (70% of average).
Overall reservoir storage in the Colorado River Basin has increased by over 4 maf since the beginning of water year 2005 and this is an improvement over the persistent drought conditions during water years 2000 through 2004. From the beginning of water year 2005 to the beginning of water year 2013, the total reservoir storage in the Colorado River Basin increased from 29.8 maf (50% of capacity) to 33.9 maf (57 % of capacity). However, this period experienced increases and decreases in total Colorado Basin storage in response to wet and dry hydrology.
RRFW thanks Katrina Grantz of the USBOR for this information.
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RRFW Riverwire – Glen Canyon Dam Update October 24, 2012
Current Status
Releases from Glen Canyon Dam in October are averaging approximately 8,030 cfs (cubic feet per second) and are steady with no fluctuations for hydropower generation. The scheduled release volume for October is 494 kaf (thousand acre-feet). In September and October, as part of the 2008 FONSI (Finding of No Significant Impact), releases from Glen Canyon Dam will be steady for a steady flow experiment. 2012 is the last year of the 5-year steady flow experiment. The anticipated release volume for November is 600 kaf with fluctuations for power generation throughout the day consistent with the Glen Canyon Operating Criteria (Federal Register, Volume 62, No. 41, March 3, 1997). However, the release volume may be adjusted in the event of a High Flow Experiment. (see below).
This fall marks the first season under a multi-year High Flow Protocol announced earlier this year by Secretary Salazar. See the following link for more details: http://www.doi.gov/news/pressreleases/Salazar-Announces-Improvements-to-Glen -Canyon-Dam-Operations-to-Restore-High-Flows-and-Native-Fish-in-Grand-Canyon .cfm
Under this Protocol, high flow releases are linked to sediment input and other resource conditions below Glen Canyon Dam. Preliminary sediment estimates appear favorable for a high flow experimental release to occur during the period of November 18 – 25, 2012 should sediment and other conditions warrant.
Reclamation’s planning activities for the high flow release are focusing on an anticipated date of November 19, 2012 for the bypass release to begin; however, no final decisions on the dates, duration or amount of the release have been made. Dam operations to ramp up to powerplant capacity prior to the bypass event would begin on November 18. During the High Flow Experiment, total releases from Glen Canyon Dam at full bypass may reach approximately 42,000 cfs. The total experiment, including ramping, could last anywhere from one and a half to six and a half days. November releases from Glen Canyon Dam prior to and after the high flow experiment would fluctuate between 5,000cfs and 8,000cfs. As more information on the potential high flow release becomes available, that information will be updated here.
To view the most current reservoir elevation, content, inflow and release, click on: http://www.usbr.gov/uc/water/rsvrs/ops/crsp_40_gc.html.
The unregulated inflow volume to Lake Powell in September was 104 thousand acre-feet (kaf) (25% of average). The release volume from Glen Canyon Dam in September was 481 kaf. The end of September elevation and storage of Lake Powell were 3621.6 feet (78.4 feet from full pool) and 13.93 maf (million acre-feet) (57.3% of full capacity). The reservoir elevation is now declining.
The water year unregulated inflow volume for 2012 was 4.91maf (45.3% of average), placing the 2012 as the third driest on record since the closure of Glen Canyon Dam in 1963. Only 2002 and 1977 were drier, receiving 2.64 maf and 3.53 maf, respectively. In terms of reservoir elevation and storage, Lake Powell reached its peak for water year 2012 on June 3rd at 3636.9 ft (63.1 feet from full pool) and 15.64 maf (64.3% of capacity), respectively. The peak elevation in 2012 was 24 feet below the 2011 peak elevation of 3660.9 ft.
Releases for Water Year 2012 totaled 9.466 maf. Pursuant to the 2007 Interim Guidelines, Lake Powell operated under the Equalization Tier in 2012. Due to the dry hydrologic conditions experienced in 2012, the Equalization release objective was 9.463 maf, which is 8.23 maf plus 1.233 maf (the Equalization release volume from 2011 that could not be achieved by September 30, 2011). Throughout water year 2012, Reclamation adjusted operations of Glen Canyon Dam to release the appropriate annual volume during 2012 to achieve Equalization objectives as practicably as possible by September 30, 2012.
Current Dam Operations
The operating tier for 2013 is the Upper Elevation Balancing Tier, as establish in August 2012 and pursuant to the Interim Guidelines. However, if hydrologic conditions and projections become wetter, it is possible that beginning in April, the Equalization tier will govern the operations of Lake Powell for the remainder of the water year. Based on analysis of a range of inflow scenarios, the current probability of realizing an inflow volume that would trigger Equalization in 2013 is approximately 20 percent. As hydrologic conditions for Lake Powell and Lake Mead change throughout the year, Reclamation will adjust operations of Glen Canyon Dam to release the appropriate annual volume during 2013 to achieve the governing operating tier objectives as practicably as possible by September 30, 2013.
Releases from Glen Canyon Dam in October are averaging approximately 8,030 cfs and are steady with no fluctuations for hydropower generation. The scheduled release volume for October is 494 kaf. In September and October, as part of the 2008 FONSI, releases from Glen Canyon Dam will be steady for a steady flow experiment. 2012 is the last year of the 5-year steady flow experiment.
The anticipated release volume for November is 600 kaf with fluctuations for power generation throughout the day consistent with the Glen Canyon Operating Criteria (Federal Register, Volume 62, No. 41, March 3, 1997). However, the release volume may be adjusted in the event of a High Flow Experiment. This fall marks the first season of a multi-year High-Flow Protocol, under which high flow releases are linked to sediment input and other resource conditions below Glen Canyon Dam. Preliminary analysis appears favorable for a high flow experimental release to occur during the period of November 18 – 25, 2012. During the High Flow Experiment, total releases from Glen Canyon Dam at full bypass may reach approximately 42,000 cfs. The total experiment, including ramping, could last anywhere from one and a half to six and a half days. In the event of a high flow experiment, releases from Glen Canyon Dam prior to and after the high flow experiment are anticipated to fluctuate between 5,000cfs and 8,000cfs.
In December, the release volume will likely be about 800 kaf, with fluctuations throughout the day from about 8,000 cfs in the early morning to about 16,000cfs in the early evening.
In addition to daily scheduled fluctuations for power generation, the instantaneous releases from Glen Canyon Dam may also fluctuate to provide 40 MW of system regulation. These instantaneous release adjustments stabilize the electrical generation and transmission system and translate to a range of about 1,100 cfs above or below the hourly scheduled release rate. Typically, fluctuations for system regulation are very short lived and balance out over the hour and do not have noticeable impacts on downstream river flow conditions.
Releases from Glen Canyon Dam can also fluctuate beyond scheduled fluctuations for power generation when called upon as a partner that shares reserve requirements within the electrical generator community (i.e. balancing area). To provide system reliability, all participating electricity generators within the balancing area maintain a specified level of generation capacity (i.e. reserves) that can be called upon when an unscheduled outage occurs. Glen Canyon Dam typically maintains 43 MW of reserves (approximately 1,100 cfs) for this purpose. Reserve calls can be maintained for a maximum of 2 hours after which time the generation rate should be returned to the original schedule. If reserves from Glen Canyon Dam are called upon, releases from the dam can exceed scheduled levels and can have a noticeable impact on the river downstream from Glen Canyon Dam. Calls for reserves are fairly infrequent and typically are for much less than 43 MW.
Current Inflow Forecasts and Model Projections
The hydrologic outlook forecast for water year 2013 projects that the most probable (median) unregulated inflow volume will be 7.60 maf (70% of average based on the period 1981-2010). Based on this hydrologic outlook, the October 24-Month study projects the annual release volume for water year 2013 will be 8.23 maf and the end of water year reservoir elevation and storage for Lake Powell will be 3608.52 (91.48 feet from full pool) and 12.582 maf (51.7% capacity), respectively.
If hydrologic conditions and projections become wetter, it is possible that beginning in April, the Equalization tier will govern the operations of Lake Powell for the remainder of the water year and the release volume for 2013 could be greater than 8.23 maf. Based on analysis of a range of inflow scenarios, the current probability of realizing an inflow volume that would trigger Equalization in 2013 is approximately 20 percent.
Upper Colorado River Basin Hydrology
Since water year 2005, hydrologic conditions in the Upper Colorado River Basin have resulted in significant year to year variability. The unregulated inflow to Lake Powell, which is a good measure of the hydrologic condition in the Colorado River Basin, has averaged a water year volume of 10.22 maf (94% of average (period 1981-2010)) during the period from 2005 through 2012. The hydrologic variability during this period has been from a low water year unregulated inflow volume of 4.91 maf (45% of average) in water year 2012 to a high water year unregulated inflow volume of 15.97 maf (147% of average) in water year 2011. Based on observed inflows and current forecasts, water year 2013 unregulated inflow is expected to be 7.60 maf (70% of average).
Overall reservoir storage in the Colorado River Basin has increased by over 4 maf since the beginning of water year 2005 and this is an improvement over the drought conditions during water years 2000 through 2004. On October 1, 2004, the beginning of water year 2005, the total reservoir storage in the Colorado River Basin was 29.8 maf (50% of capacity). On October 1, 2012, the beginning of water year 2013, the total reservoir storage in the Colorado River Basin was 33.9 maf (57 % of capacity).
RRFW thanks Katrina Grantz, US Bureau of Reclamation, for this information
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RRFW Riverwire – Glen Canyon Dam Update July 9, 2012
Glen Canyon Dam / Lake Powell
For the Water Supply period April through July, 2012 will most likely be the third driest year on record since the closure of Glen Canyon Dam in 1963. Only 1977 and 2002 will have had lower April-July unregulated inflow volumes to Lake Powell than what is most likely to occur in 2012.
The monthly unregulated inflow volume to Lake Powell for June was 353 thousand acre-feet (kaf) (13% of average). This was very nearly equal to the forecasted unregulated inflow volume at the beginning of June which was 350 kaf. The release volume from Glen Canyon Dam in June was 709 kaf which was 1,000 acre-feet above what was scheduled for release during the month. The end of June elevation and storage of Lake Powell was 3633.90 feet (66.10 feet from full pool) and 15.29 million acre-feet (maf) (62.88% of full capacity).
The Water Supply Forecast for Lake Powell (April through July Unregulated Inflow Volume) for July remained unchanged from June at 2.01 maf (28% of average).
Current Dam Operations
In August 2011, pursuant to the Interim Guidelines, the Operating Tier for Glen Canyon Dam was established to be the Equalization Tier. Under the Equalization Tier when conditions dry out as they have this year, the minimum annual release from Lake Powell can generally be as low as 8.23 maf. However, water year 2011 was a very wet Equalization year and not all of the Equalization release volume for 2011 could be achieved by September 30, 2011. As a result, 1.233 maf of the 2011 Equalization release volume was actually released after the end of water year 2011. This increased the minimum release volume for water year 2012 under Equalization to 9.463 maf. Under the dry hydrologic conditions currently projected for Lake Powell, the water year 2012 release volume is projected to be at this minimum Equalization level of 9.463 maf. As hydrologic conditions for Lake Powell and Lake Mead change throughout the year, Reclamation will adjust operations of Glen Canyon Dam to release the appropriate annual volume during 2012 to achieve Equalization objectives as practicably as possible by September 30, 2012.
Releases from Glen Canyon Dam are now averaging about 14,500 cubic feet per second (cfs) with fluctuations for power generation throughout the day that peak near 18,000 cfs in the afternoons and with early morning low level releases are about 10,000 cfs and this operation is consistent with the Glen Canyon Operating Criteria (Federal Register, Volume 62, No. 41, March 3, 1997). The release volume for July is scheduled to be 889 kaf and this volume is elevated slightly in order to target a release volume in August of 800 kaf. In August, fluctuations are projected to peak near 17,000 cfs during the afternoons with early morning low releases near 9,000 cfs. In September and October, as part of the 2008 FONSI, releases from Glen Canyon Dam will be steady for a steady flow experiment. The targeted release rate for September and October of 2012 is 8,000 cfs.
In addition to daily scheduled fluctuations for power generation, the instantaneous releases from Glen Canyon Dam may also fluctuate to provide 40 megawatts (MW) of system regulation. These instantaneous release adjustments stabilize the electrical generation and transmission system and translate to a range of about 1100 cfs above or below the hourly scheduled release rate. Typically, fluctuations for system regulation are very short lived and balance out over the hour and do not have noticeable impacts on downstream river flow conditions.
Releases from Glen Canyon Dam can also fluctuate beyond scheduled fluctuations for power generation when called upon as a partner that shares reserve requirements within the electrical generator community (i.e. balancing area). There are many generators that supply electricity to the transmission system within the balancing area. At times, a participating generator may experience operating conditions such that it cannot make its scheduled delivery of electricity to the system (i.e. unscheduled outage). To provide system reliability, all participating electricity generators within the balancing area maintain a specified level of generation capacity (i.e. reserves) that can be called upon when an unscheduled outage occurs. Glen Canyon Dam typically maintains 113 MW of reserves for this purpose.
Reserve agreements allow the controllers of the balancing area to call upon Glen Canyon Dam to produce up to an additional 113 MW of electricity beyond what is originally scheduled for a given hour. Reserve calls can be maintained for a maximum of 2 hours after which time the generation rate should be returned to the original schedule. The 113 MW reserve requirement for Glen Canyon Dam translates to approximately 2,800 cfs of flow in the river. When the balancing area controllers call for reserve generation from Glen Canyon Dam, releases from the dam can exceed scheduled levels and have a noticeable impact on the river downstream from Glen Canyon Dam. But these calls for reserves are fairly infrequent and typically are for much less than the required level of 113 MW.
Current Inflow Forecasts and Model Projections
Over the next three months (July, August and September) the forecasted unregulated inflow volume to Lake Powell is projected to be 100 kaf (9% of average), 150 kaf (30% of average) and 200 kaf (49% of average), respectively. These percent of averages are all based on the historic period from 1981 through 2010. The most probable (i.e. 50% likely to be exceeded) unregulated inflow volume for WY2012 is projected to be 5.0 maf (46% of average). Comparing this projected water year unregulated inflow volume to the driest year on record (2002) in which the unregulated inflow volume was only 2.64 maf (24% of average), water year 2012 will likely be very dry, yet not nearly as dry as conditions were in 2002. The currently projected water year unregulated inflow volume of 5.0 maf would rank as the 3rd driest year on record since the closure of Glen Canyon Dam (1963).
The annual release volume from Glen Canyon Dam will likely be 9.463 maf and the elevation of Lake Powell at the end of WY2012 is projected to be 3622.6 feet above sea level which is 77.4 feet from the full pool elevation of 3700 feet. This elevation corresponds to a live storage volume of 14.04 maf (58 % of full capacity). These projections are based on conditions in the July 24-Months Study.
The June 2012 24-Month Study has been published and is available here. The July 2012 24-Month Study will be published by July 13, 2012 and a link to this study will be provided at this website. Updated elevation projections for Lake Powell through water year 2012 based on the most recently published 24-Month Study are maintained at: Lake Powell Projected Elevations.
Upper Colorado River Basin Hydrology
Since water year 2005, hydrologic conditions in the Upper Colorado River Basin have been near average with significant variability from year to year. The unregulated inflow to Lake Powell, which is a good measure of the hydrologic condition in the Colorado River Basin, has averaged a water year volume of 10.98 maf (101% of average (period 1981-2010)) during the period from 2005 through 2011. The hydrologic variability during this period has been from a low water year unregulated inflow volume of 8.62 maf (80% of average) in water year 2006 to a high water year unregulated inflow volume of 15.97 maf (147% of average) which occurred in water year 2011.
Overall reservoir storage in the Colorado River Basin has increased by over 8 maf since the beginning of water year 2005 and this is a significant improvement over the drought conditions during water years 2000 through 2004. On October 1, 2004, the beginning of water year 2005, the total reservoir storage in the Colorado River Basin was 29.84 maf (50.2% of capacity). On October 1, 2011, the beginning of water year 2012, the total reservoir storage in the Colorado River Basin was 38.66 maf (64.8% of capacity). As of July 8, 2012 the total reservoir storage in the Colorado River Basin was 35.80 maf (60.0% of capacity).
RRFW thanks Rick Clayton of the USBOR for this information.
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RRFW Riverwire – Glen Canyon Dam Update May 10, 2012
Glen Canyon Dam, Lake Powell
Snowpack conditions above Lake Powell have been well below average all year and are now nearly melted out. The runoff from the melting snow has been less than impressive and the inflow to Lake Powell so far has peaked at just over 15,000 cubic feet per second (cfs). It is possible that this peak could be exceeded if temperature conditions warm quickly in the coming weeks. The Colorado Basin River Forecast Center will update the Water Supply Forecast for Lake Powell (April through July Unregulated Inflow Volume) in early May. In April this forecast was for 3.50 maf (49% of average) of unregulated inflow to Lake Powell.
The monthly unregulated inflow volume to Lake Powell for April was 764 thousand acre-feet (kaf) (72% of average). This was 36 kaf below what was forecasted in early April. The release volume from Glen Canyon Dam in April was 606 kaf which was 6,000 acre-feet above what was scheduled for release during the month. As a result of the difference between the projections made in early April and actual conditions and operations that occurred in April, the elevation of Lake Powell at the end of April was 0.17 feet (about 2 inches) higher than projected. On April 30, 2012 the elevation of Lake Powell was 3635.76 feet above sea level (64.24 feet below full pool).
Current Dam Operations
Releases from Glen Canyon Dam are now averaging about 10,050 cfs with fluctuations for power generation throughout the day that peak near 13,000 cfs in the afternoons and with early morning low level releases are about 7,000 cfs and this operation is consistent with the Glen Canyon Operating Criteria (Federal Register, Volume 62, No. 41, March 3, 1997). The release volume for May is scheduled to be 600 kaf. In June, the monthly release volume will likely be about 714 kaf. Release fluctuations in June are projected to be in the range from about 9,000 cfs during the early morning hours to an afternoon peak of about 15,000 cfs.
In addition to daily scheduled fluctuations for power generation, the instantaneous releases from Glen Canyon Dam may also fluctuate to provide 40 MW of system regulation. These instantaneous release adjustments stabilize the electrical generation and transmission system and translate to a range of about 1100 cfs above or below the hourly scheduled release rate. Typically, fluctuations for system regulation are very short lived and balance out over the hour and do not have noticeable impacts on downstream river flow conditions.
Releases from Glen Canyon Dam can also fluctuate beyond scheduled fluctuations for power generation when called upon as a partner that shares reserve requirements within the electrical generator community (i.e. balancing area). There are many generators that supply electricity to the transmission system within the balancing area. At times, a participating generator may experience operating conditions such that it cannot make its scheduled delivery of electricity to the system (i.e. unscheduled outage). To provide system reliability, all participating electricity generators within the balancing area maintain a specified level of generation capacity (i.e. reserves) that can be called upon when an unscheduled outage occurs. Glen Canyon Dam typically maintains 113 megawatts (MW) of reserves for this purpose.
Reserve agreements allow the controllers of the balancing area to call upon Glen Canyon Dam to produce up to an additional 113 MW of electricity beyond what is originally scheduled for a given hour. Reserve calls can be maintained for a maximum of 2 hours after which time the generation rate should be returned to the original schedule. The 113 MW reserve requirement for Glen Canyon Dam translates to approximately 2,800 cfs of flow in the river. When the balancing area controllers call for reserve generation from Glen Canyon Dam, releases from the dam can exceed scheduled levels and have a noticeable impact on the river downstream from Glen Canyon Dam. But these calls for reserves are fairly infrequent and typically are for much less than the required level of 113 MW.
In August 2011, pursuant to the Interim Guidelines, the Operating Tier for Glen Canyon Dam was established to be the Equalization Tier. Under the Equalization Tier for 2012, with 1.233 million acre feet (maf) of release carried over from 2011 to 2012, the annual release volume for 2012 could be as low as 9.46 maf or higher depending on actual inflow conditions. As hydrologic conditions for Lake Powell and Lake Mead change throughout the year, Reclamation will adjust operations of Glen Canyon Dam to release the appropriate annual volume during 2012 to achieve Equalization objectives as practicably as possible by September 30, 2012.
Current Inflow Forecasts and Model Projections
Over the next three months (May, June and July) the forecasted unregulated inflow volume to Lake Powell is projected to be 1,050 kaf (45% of average), 1,150 kaf (43% of average) and 500 kaf (46% of average), respectively. These percent of averages are all based on the historic period from 1981 through 2010. Combining this forecast with the April Water Supply Forecast and extending projections to the end of WY2012, the most probable (i.e. 50% likely to be exceeded) unregulated inflow volume for WY2012 is projected to be 6.79 maf (63% of average).
Comparing this projected water year unregulated inflow volume to the driest year on record (2002) in which the unregulated inflow volume was only 2.64 maf (24% of average), water year 2012 will likely be very dry yet not close to the driest year on record. There is still a fair amount of uncertainty associated with the forecast conditions for the remainder of the water year.. Recent analysis indicates that it is reasonably possible for the actual unregulated inflow volume for water year 2012 to be as low as 4.9 maf (45% of average) or as high as 9.2 maf (85% of average) depending on the range of precipitation patterns that could occur over the next several months.
Based on the reasonable range inflow conditions that could occur this year, the annual release volume from Glen Canyon Dam could be as low as 9.46 maf to as high as 9.81 maf. Under the most probable inflow condition, the annual release volume is projected to be 9.46 maf and the elevation of Lake Powell at the end of WY2012 is projected to be 3632.5 feet above sea level. This elevation corresponds to a live storage volume of 15.14 maf (62 % of full capacity). These projections are based on conditions in the April 24-Months Study.
The April 2012 24-Month Study has been published and is available here: http://www.usbr.gov/uc/water/crsp/studies/24Month_04.pdf
Upper Colorado River Basin Hydrology
Since water year 2005, hydrologic conditions in the Upper Colorado River Basin have been near average with significant variability from year to year. The unregulated inflow to Lake Powell, which is a good measure of the hydrologic condition in the Colorado River Basin, has averaged a water year volume of 10.98 maf (101% of average (period 1981-2010)) during the period from 2005 through 2011. The hydrologic variability during this period has been from a low water year unregulated inflow volume of 8.62 maf (80% of average) in water year 2006 to a high water year unregulated inflow volume of 15.97 maf (147% of average) which occurred in water year 2011.
Overall reservoir storage in the Colorado River Basin has increased by over 8 maf since the beginning of water year 2005 and this is a significant improvement over the drought conditions during water years 2000 through 2004. On October 1, 2004, the beginning of water year 2005, the total reservoir storage in the Colorado River Basin was 29.84 maf (50.2% of capacity). On October 1, 2011, the beginning of water year 2012, the total reservoir storage in the Colorado River Basin was 38.66 maf (64.8% of capacity). As of May 2, 2012 the total reservoir storage in the Colorado River Basin was 37.17 maf (62.3% of capacity).
RRFW thanks Rick Clayton of the USBOR for this information.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ RIVERWIRE is a free service to the community of river lovers from River Runners for Wilderness. To join, send an e-mail address to riverwire@rrfw.org and we’ll add it to the RRFW RIVERWIRE e-mail alerts list. Join RRFW’s listserver to stay abreast of and participate in the latest river issues. It’s as easy as sending a blank e-mail to Rafting_Grand_Canyon-subscribe@yahoogroups.com Check out RRFW’s Rafting Grand Canyon Wiki for free information on Do-It-Yourself Grand Canyon rafting info http://www.rrfw.org/RaftingGrandCanyon/Main_Page Check out new items and donate at the RRFW Store! RRFW is a non-profit project of Living Rivers. https://www.rrfw.org/store
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RRFW Riverwire – Glen Canyon Dam Update February 10, 2012
Glen Canyon Dam, Lake Powell
In January 2012 the unregulated inflow volume to Lake Powell was 356 thousand acre feet (kaf), or 99% of average. This volume is very close to the final forecast for January issued by the Colorado Basin River Forecast Center on January 5th which was 375 kaf. The elevation of Lake Powell on January 31st, 2012 was 3636.90 feet above sea level (63.10 feet below full pool). During January, the elevation of Lake Powell decreased by 3.52 feet and it is likely that the elevation will continue to decrease near this rate for approximately 2 more months. By late March or early April, when the snowpack begins to melt, inflows will likely increase to a point where they are greater than releases and the elevation will begin to rise. Snowpack conditions above Lake Powell are 77% of average as of February 8, 2012.
The current Water Supply forecast (April through July Unregulated Inflow Volume) for Lake Powell for 2012 is 5.05 million acre feet (maf) which is 71% of average. Based on this inflow forecast, it is currently projected that the most probable annual release from Glen Canyon Dam in water year 2012 will be 9.46 maf. At this time of year however, there is a high level of uncertainty in hydrologic forecasts and the annual release volume from Glen Canyon Dam in WY2012 will ultimately be based on the actual inflows that occur during 2012 rather than this Water Supply forecast.
Current Dam Operations
In August 2011, pursuant to the Interim Guidelines, the Operating Tier for Glen Canyon Dam was established to be the Equalization Tier. Under the Equalization Tier for 2012, with 1.233 maf of release carried over from 2011 to 2012, the annual release volume for 2012 could be as low as 9.46 maf or higher depending on actual inflow conditions. As hydrologic conditions for Lake Powell and Lake Mead change throughout the year, Reclamation will adjust operations of Glen Canyon Dam to release the appropriate annual volume during 2012 to achieve Equalization objectives as practicably as possible by September 30, 2012.
Releases from Glen Canyon Dam are currently averaging about 12,500 cubic feet per second (cfs) with fluctuations for power generation throughout the day that peak near 13,000 cfs in the afternoons and with early morning low level releases are about 7,000 cfs. This operation is consistent with the Glen Canyon Operating Criteria (Federal Register, Volume 62, No. 41, March 3, 1997). The release volume for February is scheduled to be 650 kaf. In March, the monthly release volume will likely be 600 kaf and fluctuating releases from Glen Canyon Dam will likely average about 10,100 cfs each day with scheduled daily fluctuations occurring within the range from 7,000 cfs to 13,000 cfs.
In addition to daily scheduled fluctuations for power generation, the instantaneous releases from Glen Canyon Dam may also fluctuate to provide 40 megawatts (MW) of system regulation. These instantaneous release adjustments stabilize the electrical generation and transmission system and translate to a range of about 1100 cfs above or below the hourly scheduled release rate. Typically, fluctuations for system regulation are very short lived and balance out over the hour and do not have noticeable impacts on downstream river flow conditions.
Releases from Glen Canyon Dam can also fluctuate beyond scheduled fluctuations for power generation when called upon as a partner that shares reserve requirements within the electrical generator community (i.e. balancing area). There are many generators that supply electricity to the transmission system within the balancing area. At times, a participating generator may experience operating conditions such that it cannot make its scheduled delivery of electricity to the system (i.e. unscheduled outage). To provide system reliability, all participating electricity generators within the balancing area maintain a specified level of generation capacity (i.e. reserves) that can be called upon when an unscheduled outage occurs. Glen Canyon Dam typically maintains 113 MW of reserves for this purpose.
Reserve agreements allow the controllers of the balancing area to call upon Glen Canyon Dam to produce up to an additional 113 MW of electricity beyond what is originally scheduled for a given hour. Reserve calls can be maintained for a maximum of 2 hours after which time the generation rate should be returned to the original schedule. The 113 MW reserve requirement for Glen Canyon Dam translates to approximately 2,800 cfs of flow in the river. When the balancing area controllers call for reserve generation from Glen Canyon Dam, releases from the dam can exceed scheduled levels and have a noticeable impact on the river downstream from Glen Canyon Dam. But these calls for reserves are fairly infrequent and typically are for much less than the required level of 113 MW.
Current Inflow Forecasts and Model Projections
Over the next three months (February, March and April) the forecasted unregulated inflow volume to Lake Powell is projected to be 390 kaf (99% of average), 550 kaf (83% of average) and 800 kaf (76% of average), respectively. These percent of averages are all based on the historic period from 1981 through 2010. Combining this forecast with the February Water Supply Forecast and extending projections to the end of WY2012, the most probable (i.e. 50% likely to be exceeded) unregulated inflow volume for WY2012 is projected to be 8.48 maf (78% of average). There is significant uncertainty associated with this forecast. Recent analysis indicates that it is reasonably possible for the actual unregulated inflow volume to be as low as 5.48 maf (51% of average) or as high as 12.65 maf (117% of average) depending on the range of precipitation patterns that could occur over the next several months.
Based on the reasonable range inflow conditions that could occur this year, the annual release volume from Glen Canyon Dam could be as low as 9.46 maf to as high as 12.92 maf. Under the most probable inflow condition, the annual release volume is projected to be 9.46 maf and the elevation of Lake Powell at the end of WY2012 is projected to be 3643.2 feet above sea level. This elevation corresponds to a live storage volume of 16.38 maf (67% of full capacity).
Upper Colorado River Basin Hydrology
Since water year 2005, hydrologic conditions in the Upper Colorado River Basin have been near average with significant variability from year to year. The unregulated inflow to Lake Powell, which is a good measure of the hydrologic condition in the Colorado River Basin, has averaged 10.98 maf (101% of average (period 1981-2010)) per year during the period from 2005 through 2011. The hydrologic variability during this period has been from a low water year unregulated inflow of 8.62 maf (80% of average) in water year 2006 to a high of 15.97 maf (147% of average) which occurred in water year 2011.
Overall reservoir storage in the Colorado River Basin has increased by nearly 10 maf since the beginning of water year 2005 and this is a significant improvement over the drought conditions during water years 2000 through 2004. On October 1, 2004, the beginning of water year 2005, the total reservoir storage in the Colorado River Basin was 29.84 maf (50.2% of capacity). As of January 30, 2012 the total reservoir storage in the Colorado River Basin was 38.35 maf (64.3% of capacity). RRFW thanks Rick Clayton of the USBOR for this information.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ RIVERWIRE is a free service to the community of river lovers from River Runners for Wilderness. To join, send an e-mail address to riverwire@rrfw.org and we’ll add it to the RRFW RIVERWIRE e-mail alerts list.
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RRFW Riverwire – Glen Canyon Dam Update January 19, 2012
Glen Canyon Dam, Lake Powell
During December 2011 the unregulated inflow volume to Lake Powell was 359 thousand acre-feet (kaf). This represents 99% of average based on the historic period from 1981 through 2010. This was well below the volume forecasted for the month of December which was 500 kaf (138% of average). As a result, the elevation of Lake Powell at the end of December was 3639.7 feet above sea level which was 1.1 feet lower than projected at the beginning of December.
Snowpack conditions above Lake Powell are well below average for this time of year. As of January 9, 2012 the overall snowpack above Lake Powell was only 60% of average. Reclamation has received the first Water Supply forecast for 2012 and the April through July unregulated inflow to Lake Powell is projected to be 5.05 million acre-feet (maf) which is 71% of average. Based on this forecast, the projected most probable (i.e. 50% likely to be exceeded) annual release volume from Glen Canyon Dam in water year 2012 will be 9.46 maf. At this time of year however, there is a high level of uncertainty in hydrologic forecasts and the annual release volume from Glen Canyon Dam in WY2012 will ultimately be based on actual hydrology rather than forecasted hydrology.
Current Dam Operations
In response to the Water Supply forecast issued for Lake Powell in January, Reclamation has reduced the release volume for January from 1000 kaf to 850 kaf. This reduction began on January 10, 2012. Releases from Glen Canyon Dam are currently averaging about 13,200 cubic feet-per-second (cfs) with fluctuations for power generation throughout the day that peak near 17,500 cfs in the afternoons. Early morning low releases are about 9,500 cfs. This operation is consistent with the Glen Canyon Operating Criteria (Federal Register, Volume 62, No. 41, March 3, 1997).
It is forecasted that in February, releases from Glen Canyon Dam will most likely be about 650 kaf which is a daily average of 11,300 cfs. Fluctuations will range between 7,000 cfs off peak to 13,000 cfs on-peak. In March, current forecasts estimate a likely release of 600 kaf which is a daily average of 9,758 cfs. Fluctuations will range between 7,000 cfs off peak and 13,000 cfs on peak. February’s release volume will most likely not change. While the release volume in March won’t be less than 600 kaf, if the basin hydrology becomes wetter than currently expected, there is a moderate chance that Reclamation will increase the release volume.
In addition to hourly release fluctuations for load following power generation, the instantaneous releases from Glen Canyon Dam may also fluctuate somewhat to provide 40 MW of system regulation. These instantaneous release adjustments stabilize the electrical generation and transmission system and translate to a range of about 1100 cfs above or below the hourly release rate that is scheduled for a given hour. Typically, fluctuations for system regulation are very short lived and balance out over the hour and do not have noticeable impacts on river flow conditions.
Releases from Glen Canyon Dam can also fluctuate beyond the typical load following pattern when called upon as a partner that shares reserve requirements within the electrical generator community (i.e. control area). There are many generators that supply electricity to the transmission system within the control area. At times, a participating generator may experience operating conditions such that it cannot make its scheduled delivery of electricity to the system (i.e. outage). To provide system reliability, all participating electricity generators within the control area maintain a specified level of generation capacity (i.e. reserves) that can be called upon when an outage occurs. Glen Canyon Dam typically maintains 109 megawatts (MW) of reserves for this purpose.
Reserve agreements allow the controllers of the transmission system to call upon Glen Canyon Dam for up to 109 MW of additional generation beyond what is originally scheduled for a given hour. These calls for reserve generation can be maintained for up to 2 hours in total duration. The 109 MW reserve requirement for Glen Canyon Dam translates to approximately 2,700 cfs of flow in the river and calls for reserves can have noticeable impacts on river flow conditions. Calls for reserves are fairly infrequent and typically are for much less than the maximum requirement of 109 MW.
In August 2011, as part of the Colorado River Annual Operating Plan process, the Operating Tier for Glen Canyon Dam was determined to be the Equalization Tier under the 2008 Interim Guidelines. Under the Equalization Tier, with 1.233 maf of release volume carried over from 2011 to 2012, the annual release volume for WY2012 could be as low as 9.46 maf to as high as 13.1 maf or higher depending on actual inflow conditions. As inflow and storage conditions for Lake Powell and Lake Mead change throughout the year, Reclamation will make practicable adjustments to the operation of Glen Canyon Dam to release the appropriate annual volume during 2012. The overall goal during 2012 in terms of annual release will be to achieve the objectives of the Equalization Tier of the Interim Guidelines.
Current Inflow Forecasts and Model Projections
Over the next three months (January, February, March) the forecasted unregulated inflow volume to Lake Powell is projected to be 375 kaf (104% of average), 410 kaf (104% of average) and 575 kaf (86% of average), respectively. These percent of averages are all based on the historic period from 1981 through 2010. Combining this forecast with the January Water Supply Forecast and extending projections to the end of Water Year (WY) 2012, the mostprobable (i.e. 50% likely to be exceeded) unregulated inflow volume for WY2012 is now projected to be 8.55 maf (79% of average). The minimum probable (i.e. 90% likely to be exceeded) unregulated inflow volume for WY2012 is now projected to be 5.48 maf (51% of average). The maximum probable (i.e. 10% likely to be exceeded) unregulated inflow volume for WY2012 is now projected to be 12.65 maf (117% of average).
Based on this range of possible inflow conditions, the January 24-Month Study projects the annual release volume for WY2012 to be as lows as 9.46 maf (under the minimum probable inflow condition) to as high as 13.01 maf (under the maximum probable inflow condition). Under the most probable inflow condition, the annual release volume is projected to be 9.46 maf and the elevation of Lake Powell at the end of WY2012 is projected to be 3643.9 feet above sea level. This elevation corresponds to a live storage volume of 16.47 maf (68% of full capacity).
Upper Colorado River Basin Hydrology
Since water year 2005, hydrologic conditions in the Upper Colorado River Basin have been near average with significant variability from year to year. The unregulated inflow to Lake Powell, which is a good measure of the hydrologic condition in the Colorado River Basin, has averaged 10.98 maf (101% of average (period 1981-2010) per year during the period from 2005 through 2011. The hydrologic variability during this period has been from a low water year unregulated inflow of 8.62 maf (80% of average) in water year 2006 to a high of 15.97 maf (147% of average) which occurred in water year 2011.
Overall reservoir storage in the Colorado River Basin has increased by nearly 10 maf since the beginning of water year 2005 and this is a significant improvement over the drought conditions during water years 2000 through 2004. On October 1, 2004, the beginning of water year 2005, the total reservoir storage in the Colorado River Basin was 29.84 maf (50.2% of capacity). As of January 10, 2012 the total reservoir storage in the Colorado River Basin was 38.54 maf (64.8% of capacity).
RRFW thanks Rick Clayton of the USBOR for this information.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ RIVERWIRE is a free service to the community of river lovers from River Runners for Wilderness. To join, send an e-mail address to riverwire@rrfw.org and we’ll add it to the RRFW RIVERWIRE e-mail alerts list.
Join RRFW’s listserver to stay abreast of and participate in the latest river issues. It’s as easy as sending a blank e-mail to Rafting_Grand_Canyon-subscribe@yahoogroups.com
Check out RRFW’s Rafting Grand Canyon Wiki for free information on Do-It-Yourself Grand Canyon rafting info http://www.rrfw.org/RaftingGrandCanyon/Main_Page
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RRFW Riverwire – Glen Canyon Dam Update Dec 14, 2011
Glen Canyon Dam / Lake Powell
During November 2011 the unregulated inflow volume to Lake Powell was 570 thousand acre feet (kaf ) – 108% of average. This was very close to the forecast volume issued by the Colorado Basin River Forecast Center on November 1, 2011. The forecast volume was 600 kaf (110% of average). Releases from Glen Canyon Dam during November were 1099 kaf and the elevation of Lake Powell decreased by 4.59 ending November at an elevation of 3645.69 feet above sea level. Releases from Glen Canyon Dam are currently averaging approximately 20,300 cfs and are near steady. This release rate is likely to continue to near the end of December and then will likely be reduced to a daily average release of approximately 16,300 cfs with daily fluctuations for power generation.
Current Dam Operations
Releases from Glen Canyon Dam for the Steady Flow Experiment (see Experimental Releases from Glen Canyon Dam, Arizona 2008 through 2012, Final Environmental Assessment and Finding of No Significant Impact) ended at midnight on October 31, 2011. The steady flow target for 2011 was 15,500 cfs which was the maximum sustainable release rate from Glen Canyon Dam during September and October. Since then, releases from Glen Canyon Dam have been maximized at powerplant capacity which varies depending on unit efficiency and availability. Current releases are approximately 20,300 cfs.
Since March 2011, releases from Glen Canyon Dam have been maximized through the powerplant in order to achieve the Equalization objectives of the Interim Guidelines. The Equalization objective for water year 2011 was to release sufficient volume from Glen Canyon Dam during the water year such that the elevation of Lake Powell would be 3643 feet above sea level on September 30, 2011.
Inflows to Lake Powell during the spring and summer of 2011 were well above average and the 7 months of maximum powerplant capacity releases from Glen Canyon Dam were not sufficient to achieve an elevation of 3643 feet on September 30, 2011. The elevation of Lake Powell on September 30, 2011 was 3653.01 feet above sea level and this translates to a volume of 1.233 maf that was in storage in Lake Powell on September 30, 2011 that would have otherwise been released for Equalization during water year 2011 if the powerplant had the capacity to make these higher releases.
Releases through the powerplant during the first 3 months of water year 2012 (October, November and December, 2011) have continued at powerplant capacity in order to make up for the Equalization releases that were not made in water year 2011 due to the limitations of the powerplant. It is currently projected that the additional release volume will be completed by the end of December 2011 at which time releases from Glen Canyon Dam will be reduced. It is estimated that this release reduction will likely occur on or about December 28, 2011. The instantaneous release rate from Glen Canyon Dam may fluctuate somewhat to provide 40 MW of system regulation.
These instantaneous release adjustments maintain stable conditions within the electrical generation and transmission system and result in momentary release fluctuations within a range of about 1100 cfs above or below the targeted hourly release rate. The momentary fluctuations for regulation are very short lived and typically balance out over the hour.
Spinning and non-spinning reserve generation may also be maintained at Glen Canyon Dam. In order for Colorado River Storage Project (CRSP) powerplants to participate in the electrical generation and transmissions system, these powerplants must maintain a level of generation capacity available in reserve to assist the local control area for when unanticipated generation outages occur. The current CRSP powerplant reserve requirement is 109 MW (equivalent to approximately 2,675 cfs of release from Glen Canyon Dam).
When an electrical outage occurs within the control area, CRSP powerplants can be called upon to provide up to 109 MW of additional generation for up to 2 hours. Under normal circumstances, calls for reserves are infrequent and for much less than the required 109 MW. Because Glen Canyon Powerplant is the largest facility of the CRSP powerplants, typically most of the CRSP reserve requirement is maintained at Glen Canyon Dam but at times this reserve requirement is maintained at other plants within the CRSP system.
Current Inflow Forecasts and Model Projections
Over the next three months (December, January and February) the forecasted unregulated inflow to Lake Powell is projected to be above average with monthly percent of average forecasts of 115%, 111% and 107%, respectively. Based on these updated forecast values and the Hydrologic Outlook for water year 2012 (provided in October, 2011) the current projection for the most probable unregulated inflow volume to Lake Powell for water year 2012 is 11.4 maf (95% of average). At this time of year, there is a high level of uncertainty associated with this projection. Based on this projection, the December 2011 24-Month Study projects the water year 2012 most probable release volume will be 11.9 maf under the Equalization Tier of the Interim Guidelines. The December 2011 24-Month Study also projects the elevation condition for Lake Powell and Lake Mead at the end of water year 2012 to be 3645.0 feet and 1139.4 feet, respectively.
Upper Colorado River Basin Hydrology
Since water year 2005, hydrologic conditions in the Upper Colorado River Basin have been slightly below average with significant variability from year to year. The unregulated inflow to Lake Powell, which is a good measure of the hydrologic condition in the Colorado River Basin, has averaged 11.15 maf per year during the period from 2005 through 2011. This is slightly below the official average of 12.04 maf per year. The hydrologic variability during this period has been from a low water year unregulated inflow of 8.40 maf (70% of average) in water year 2006 to a high of over 16.77 maf (139% of average) which occurred in water year 2011.
Overall reservoir storage in the Colorado River Basin has increased by nearly 10 maf since the beginning of water year 2005 and this is a significant improvement over the drought conditions during water years 2000 through 2004. On October 1, 2004, the beginning of water year 2005, the total reservoir storage in the Colorado River Basin was 29.84 maf (50.2% of capacity). As of December 6, 2011, the total reservoir storage in the Colorado River Basin was 38.41 maf (64.6% of capacity).
RRFW thanks Rick Clayton, US Bureau of Reclamation
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RRFW Riverwire – Glen Canyon Dam Update November 7, 2011
Glen Canyon Dam Lake Powell
During October 2011 the unregulated inflow volume to Lake Powell was 575 thousand acre feet (kaf) which is 105% of average. This was approximately 75 kaf below what was projected in the October 24-Month Study and resulted in the elevation of Lake Powell ending October about 1.26 feet below what was projected in the October 24-Month Study. The October 31th, 2011 elevation of Lake Powell was 3650.27 feet above sea level which corresponds to a live storage of approximately 17.25 million acre feet (maf) and 70.9% of the full capacity of 24.32 maf.
For water year 2011, the observed unregulated inflow volume to Lake Powell was 16.77 maf (139% of average for the 1971-2000 historical period of record). The 2011 water year unregulated inflow volume was the 6th wettest out of 48 years since the closure of Glen Canyon Dam (1963). Water year unregulated inflow volumes of the magnitude observed in water year 2011 (or greater) would statistically be expected to occur in about 12-14% of all years.
The 2011 water year release volume from Glen Canyon Dam was 12.52 maf and this was the largest water year release volume made from Glen Canyon Dam since water year 1998. During water year 2011 the above average inflow volume combined with the large water year release volume from Glen Canyon Dam resulted in Lake Powell realizing a net gain in elevation (year over year) of 19.35 feet which translates to an increase in live storage in Lake Powell of 2.32 maf.
Current Dam Operations
Releases from Glen Canyon Dam for the 2011 steady flow experiment ended at midnight on October 31, 2011. Releases from Glen Canyon Dam are now being maximized within unit availability to release Equalization water for 2011. At the end of water year 2011 (September 30, 2011) the elevation of Lake Powell was 3653.01 feet above sea level and this was 10.01 feet above the Equalization level for water year 2011 (3643 feet) and translated to a volume of 1.123 maf that was in storage above the 2011 Equalization level. Releases from Glen Canyon Dam are being made at the full capacity of the power-plant to release this additional volume in order to achieve the 2011 Equalization objective. Once this additional volume has been released, releases from Glen Canyon Dam will be reduced from the full capacity of the power-plant. Current projections are that this objective will likely be completed by late December 2011.
Beginning on November 4, 2011, releases from Glen Canyon Dam will be adjusted to approximately 15,025 cubic feet per second (cfs) until the end of the day on November 10, 2011. Releases will likely be steady during this period. Glen Canyon Dam will maintain 109 megawatts (MW) of generation capacity for possible calls on reserve generation and 40 MW of generation capacity for system regulation.
Beginning on November 11, 2011, releases from Glen Canyon Dam will be adjusted to approximately 19,325 cfs until the end of the day on November 17, 2011. Releases will likely be steady during this period. Glen Canyon Dam will maintain 69 MW of generation capacity for possible calls on reserve generation and 40 MW of generation capacity for system regulation.
Beginning on November 18, 2011, releases from Glen Canyon Dam will be adjusted to approximately 20,750 cfs until the end of the day on November 30, 2011. Releases will likely be steady during this period. Glen Canyon Dam will maintain 15 MW of generation capacity for possible calls on reserve generation and 40 MW of generation capacity for system regulation.
The total release volume for November will be approximately 1.100 maf in order to complete this release schedule. Hourly and daily average releases from Glen Canyon Dam for November 2011 will be scheduled through Western Area Power Administration. While daily fluctuations are not anticipated during November, all release adjustments will be scheduled to be consistent with the Glen Canyon Dam Operating Criteria (Federal Register, Volume 62, No. 41, March 3, 1997).
The anticipated release volume for December 2011 will be 1.225 maf. This will be confirmed in a subsequent notification toward the end of November.
While the release rate from Glen Canyon Dam over the next two months will likely be near steady, the instantaneous releases from Glen Canyon Dam may fluctuate somewhat to provide 40 MW of system regulation. These instantaneous release adjustments maintain stable conditions within the electrical generation and transmission system and result in momentary release fluctuations within a range of about 1,100 cfs above or below the targeted hourly release rate. The momentary fluctuations for regulation are very short lived and typically balance out over the hour.
Spinning and non-spinning reserve generation may also be maintained at Glen Canyon Dam. In order for Colorado River Storage Project (CRSP) power-plants to participate in the electrical generation and transmissions system, these power-plants must maintain a level of generation capacity available in reserve to assist the local control area for when unanticipated generation outages occur. The current CRSP power-plant reserve requirement is 100 MW (equivalent to approximately 2,675 cfs of release from Glen Canyon Dam). When an electrical outage occurs within the control area, CRSP power-plants can be called upon to provide up to 100 MW of additional generation for up to 2 hours. Under normal circumstances, calls for reserves are infrequent and for much less than the required 100 MW. Because Glen Canyon Power-plant is the largest facility of the CRSP power-plants, most of the CRSP reserve requirement is maintained at Glen Canyon Dam but at times this reserve requirement is maintained at other plants within the CRSP system.
Current Inflow Forecasts and Model Projections
Over the next three months (October, November and December) the forecasted unregulated inflow to Lake Powell is projected to be above average with monthly percent of average forecasts of 119%, 115% and 120%, respectively. The hydrologic outlook forecast for water year 2012 has been revised in October and now projects that the most probable (median) unregulated inflow volume to be 11.6 maf (96% of average based on the period from 1971 through 2000). Based on this revised hydrologic outlook forecast, the October 24-Month Study projects the annual release volume for water year 2012 will likely be 12.26 maf. The October 24-Month Study also projects that the end of water year reservoir elevation and storage for Lake Powell will likely be 3645.00 feet (55.00 feet from full pool) and 16.60 maf (68% of capacity), respectively.
The October 2011 24-Month Study has been published and is available here:
http://www.usbr.gov/uc/water/crsp/studies/24Month_10.pdf
This study will be updated to reflect November 2011conditions during the second week of November 2011. Updated elevation projections for Lake Powell through water year 2012 based on the most recently published 24-Month Study are maintained at:
http://www.usbr.gov/uc/water/crsp/studies/lppwse.html
Upper Colorado River Basin Hydrology
Since water year 2005, hydrologic conditions in the Upper Colorado River Basin have been slightly below average with significant variability from year to year. The unregulated inflow to Lake Powell, which is a good measure of the hydrologic condition in the Colorado River Basin, has averaged 11.15 maf per year during the period from 2005 through 2011. This is slightly below the official average of 12.04 maf per year. The hydrologic variability during this period has been from a low water year unregulated inflow of 8.40 maf (70% of average) in water year 2006 to a high of over 16.77 maf (139% of average) which occurred in water year 2011.
Overall reservoir storage in the Colorado River Basin has increased by nearly 10 maf since the beginning of water year 2005 and this is a significant improvement over the drought conditions during water years 2000 through 2004. On October 1, 2004, the beginning of water year 2005, the total reservoir storage in the Colorado River Basin was 29.84 maf (50.2% of capacity). As of October 12, 2011, the total reservoir storage in the Colorado River Basin was 38.62 maf (64.9% of capacity).
RRFW thanks Rick Clayton of the USBOR for this information.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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RRFW Riverwire – Glen Canyon Dam Update October 13, 2011
Glen Canyon Dam Lake Powell
During September 2011 the unregulated inflow volume to Lake Powell was 532 thousand acre feet (kaf) or 112% of average. This was approximately 93 kaf below what was projected in the September 24-Month Study and resulted in the elevation of Lake Powell ending September about 0.92 feet below what was projected in the September 24-Month Study. The September 30th, 2011 elevation of Lake Powell was 3653.01 feet above sea level which corresponds to a live storage of approximately 17.59 million acre feet (maf) and 72.3% of the full capacity of 24.32 maf.
For water year 2011, the observed unregulated inflow volume to Lake Powell was 16.77 maf (139% of average for the 1971-2000 historical period of record). The 2011 water year unregulated inflow volume was the 6th wettest out of 48 years since the closure of Glen Canyon Dam (1963). Water year unregulated inflow volumes of the magnitude observed in water year 2011 (or greater) would statistically be expected to occur in about 12-14% of all years.
The 2011 water year release volume from Glen Canyon Dam was 12.52 maf and this was the largest water year release volume made from Glen Canyon Dam since water year 1998. During water year 2011 the above average inflow volume combined with the large water year release volume from Glen Canyon Dam resulted in Lake Powell realizing a net gain in elevation (year over year) of 19.35 feet which translates to an increase in live storage in Lake Powell of 2.32 maf.
Current Dam Operations
Releases from Glen Canyon Dam are now being made for a steady flow experiment that will continue to the end of October. Releases from Glen Canyon Dam are steady at approximately 15,500 cubic feet per second (cfs) and will likely remain at the level through October 31, 2011 to complete the 2 month steady flow experiment.
In early November through November 10, 2011, releases will likely continue to be steady near 15,500 cfs due to ongoing maintenance work at Glen Canyon Power-plant on units 5 and 6. On or about November 11, 2011 releases will likely be increased to approximately 22,600 cfs when units 5 and 6 are returned to service. The projected release volume for November is 1200 kaf.
While the release rate from Glen Canyon Dam over the next several months will likely be near steady, the instantaneous releases from Glen Canyon Dam may fluctuate somewhat to provide 40 MW of system regulation. These instantaneous release adjustments maintain stable conditions within the electrical generation and transmission system and result in momentary release fluctuations within a range of about 1100 cfs above or below the targeted hourly release rate. The momentary fluctuations for regulation are very short lived and typically balance out over the hour.
Spinning and non-spinning reserve generation is also maintained at Glen Canyon Dam. In order for Colorado River Storage Project (CRSP) power-plants to participate in the electrical generation and transmissions system, these power-plants must maintain a level of generation capacity available in reserve to assist the local control area for when unanticipated generation outages occur. The current CRSP power plant reserve requirement is 100 MW (equivalent to approximately 2,675 cfs of release from Glen Canyon Dam). When an electrical outage occurs within the control area, CRSP power-plants can be called upon to provide up to 100 MW of additional generation for up to 2 hours. Under normal circumstances, calls for reserves are infrequent and for much less than the required 100 MW. Because Glen Canyon Power-plant is the largest facility of the CRSP power-plants, most of the CRSP reserve requirement is maintained at Glen Canyon Dam.
Current Inflow Forecasts and Model Projections
Over the next three months (October, November and December) the forecasted unregulated inflow to Lake Powell is projected to be above average with monthly percent of average forecasts of 119%, 115% and 120%, respectively. The hydrologic outlook forecast for water year 2012 has been revised in October and now projects that the most probable (median) unregulated inflow volume to be 11.6 maf (96% of average based on the period from 1971 through 2000). Based on this revised hydrologic outlook forecast, the October 24-Month Study projects the annual release volume for water year 2012 will likely be 12.26 maf. The October 24-Month Study also projects that the end of water year reservoir elevation and storage for Lake Powell will likely be 3645.00 feet (55.00 feet from full pool) and 16.60 maf (68% of capacity), respectively.
Upper Colorado River Basin Hydrology
Since water year 2005, hydrologic conditions in the Upper Colorado River Basin have been slightly below average with significant variability from year to year. The unregulated inflow to Lake Powell, which is a good measure of the hydrologic condition in the Colorado River Basin, has averaged 11.15 maf per year during the period from 2005 through 2011. This is slightly below the official average of 12.04 maf per year. The hydrologic variability during this period has been from a low water year unregulated inflow of 8.40 maf (70% of average) in water year 2006 to a high of over 16.77 maf (139% of average) which occurred in water year 2011.
Overall reservoir storage in the Colorado River Basin has increased by nearly 10 maf since the beginning of water year 2005 and this is a significant improvement over the drought conditions during water years 2000 through 2004. On October 1, 2004, the beginning of water year 2005, the total reservoir storage in the Colorado River Basin was 29.84 maf (50.2% of capacity). As of October 12, 2011, the total reservoir storage in the Colorado River Basin was 38.62 maf (64.9% of capacity).
RRFW thanks Rick Clayton of the USBOR for this information.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ RIVERWIRE is a free service to the community of river lovers from River Runners for Wilderness. To join, send an e-mail address to riverwire@rrfw.org and we’ll add it to the RRFW RIVERWIRE e-mail alerts list.
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RRFW Riverwire – Glen Canyon Dam Update August 7, 2011
Glen Canyon Dam Lake Powell
The unregulated inflow volume to Lake Powell so far in July (as of July 28th) has been 4.15 million acre feet (maf). At the current rate the unregulated inflow volume for July will likely be approximately 4.33 maf which is 278% of average. This July volume will likely be the 2nd wettest July on record since the closure of Glen Canyon Dam (1963). Only 1995 had a wetter July than this year at 4.41 maf. The expected unregulated inflow volume for the April through July period is approximately 12.9 maf (162% of average).
The reservoir elevation of Lake Powell has increased significantly so far this runoff season. On April 9, 2011 the elevation of Lake Powell was 3609.7 feet above sea level which was the lowest elevation observed so far in 2011. Since that time the elevation of Lake Powell has increased by over 50 feet and on July 28, 2011 the reservoir elevation of Lake Powell was 3660.79 feet above sea level (39.21 feet from full pool). The last time Lake Powell’s reservoir elevation was at this level was in October of 2001 (over 10 years ago) near the beginning of the recent drought. The live storage of Lake Powell on July 28, 2011 was 18.60 maf which is 76% of capacity. The elevation of Lake Powell is very near the peak elevation that will occur this year. Inflows to Lake Powell are steadily declining and by early August will be less than the release rate at Glen Canyon Dam. When this occurs, the elevation will gradually begin to decline and this condition will continue through the fall and winter months.
Current Dam Operations
Releases from Glen Canyon Dam are approximately 24,100 cubic feet per second (cfs) which is very near the full capacity of the power plant. The release volume for July will likely be approximately 1.485 maf. Releases in August will be similar to July with releases projected to be approximately 24,000 cfs. On August 2nd, 1 unit at Glen Canyon Dam will be out of service from approximately 7:00 am to 4:00 pm for a short term maintenance project. This will reduce the release rate during this period to approximately 20,000 cfs. At the end of August, releases will likely be gradually reduced to approximately 15,000 cfs as a transition to the Steady Flow Experiment to be conducted during September and October of 2011. This year will be the 4th year of a 5 year study of steady flows during September and October as describe in the 2008 Environmental Assessment and Finding of No Significant Impact. The target release rate for the steady flow experiment this year is approximately 15,000 cfs depending on the available capacity of Glen Canyon Power Plant.
While the release rate over the next several months is likely to be steady, the instantaneous releases from Glen Canyon Dam may fluctuate somewhat to provide 40 Mega Watts (MW) of system regulation. These instantaneous release adjustments maintain stable conditions within the electrical generation and transmission system and result in momentary release fluctuations within a range of about 1100 cfs above or below the targeted hourly release rate. The momentary fluctuations for regulation are very short lived and typically balance out over the hour.
Spinning and non-spinning reserve generation is also maintained at Glen Canyon Dam. In order for Colorado River Storage Project (CRSP) power plants to participate in the electrical generation and transmissions system, these powerplants must maintain a level of generation capacity available in reserve to assist the local control area for when unanticipated generation outages occur. The current CRSP power plant reserve requirement is 100 MW (equivalent to approximately 2,675 cfs of release from Glen Canyon Dam). When an electrical outage occurs within the control area, CRSP power plants can be called upon to provide up to 100 MW of additional generation for up to 2 hours. Under normal circumstances, calls for reserves infrequent and for much less than the required 100 MW. Because Glen Canyon Power plant is the largest facility of the CRSP power plants, most of the CRSP reserve requirement is maintained at Glen Canyon Dam.
Annual Operations-Coordinated Operation of Lake Mead and Lake Powell under Interim Guidelines for Water Year 2011
In August of 2010, the 24-Month Study was used to project the January 1, 2010 elevations of Lake Powell and Lake Mead. Based on these projected elevations and pursuant to the December 2007 Record of Decision on Colorado River Interim Guidelines for Lower Basin Shortages and the Coordinated Operations of Lake Powell and Lake Mead (Interim Guidelines), the operating tier for water year 2011 was selected to be Upper Elevation Balancing. Operation of Glen Canyon Dam under Upper Elevation Balancing can result in annual releases as low as 7.0 maf to as high as 13 maf or greater depending on system conditions. The operational outcome of the Upper Elevation Balancing Tier is largely dependent on system conditions at the end of the water year that are projected in the April 24-Month Study.
The April 2011 24-Month Study projected the end of water year elevation for Lake Powell would be above 3643 feet which is the Equalization Level for 2011. For this reason, pursuant to the Interim Guidelines, Equalization will govern the operation of Glen Canyon Dam for the remaining months of water year 2011. For more information on the Interim Guidelines click here:
http://www.usbr.gov/lc/region/programs/strategies/RecordofDecision.pdf
Current Inflow Forecasts and Model Projections
The Water Supply forecast for Lake Powell (April through July Unregulated Inflow Volume) is 12.0 maf (151% of average) and the water year unregulated inflow to Powell for 2011 is projected to be 16.2 maf (135% of average). The unregulated inflow forecasts for Lake Powell over the next 3 months are as follows: July-4,000 kaf (257% of average); August-1,000 kaf (162% of average): September-670 kaf (141% of average). These forecasts were last updated on July 15, 2011. Incorporating these new forecasts, the projected most probable unregulated inflow for water year 2011 is now 16.7 maf (139% of average). This is the median projection for water year 2011. There is a 50% chance that the actual volume could be higher and there is a 50% the actual volume could be lower than this projected volume.
The July 24-Month Study projected a Lake Powell WY 2011 annual release volume of 12.45 maf. Due to recent increases to the inflow forecast for Lake Powell, Equalization may not be fully achieved by the end of the water year. The projected Lake Powell releases will be updated each month to reflect changing hydrology in order to achieve the operation specified by the Equalization Tier.
The July 2011 24-Month Study has been published and will be available here:
http://www.usbr.gov/uc/water/crsp/studies/24Month_07.pdf
Updated elevation projections for Lake Powell through water year 2011 and 2012 based on the most recently published 24-Month Study are maintained at:
http://www.usbr.gov/uc/water/crsp/studies/lppwse.html
Upper Colorado River Basin Hydrology
The Upper Colorado River Basin has experienced a protracted multi-year drought since early 2000. During this drought, the inflows to Lake Powell have been below average in every year except water years 2005, 2008 and likely 2011. In the summer of 1999, Lake Powell was close to full with reservoir storage at 23.5 million acre-feet, or 97 percent of capacity. During the next 5 years (2000 through 2004) unregulated inflow to Lake Powell was well below average. This resulted in Lake Powell storage decreasing during this period to 8.0 million acre-feet (33 percent of capacity) which occurred on April 8, 2005.
During 2005, 2008 and 2009, drought conditions eased somewhat with near or above average inflow conditions and net gains in storage to Lake Powell. This year (2011) will likely be another above average inflow year. As of July 28, 2011 the storage in Lake Powell was approximately 18.60 million acre-feet (76.0 % of capacity) which is still below the desired operating level for this time of year. The overall reservoir storage in the Colorado River Basin as of July 28, 2011 is approximately 39.20 million acre-feet (65.9 % of capacity).
RRFW thanks Rick Clayton of the USBOR for this information.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ RIVERWIRE is a free service to the community of river lovers from River Runners for Wilderness. To join, send an e-mail address to riverwire@rrfw.org and we’ll add it to the RRFW RIVERWIRE e-mail alerts list.
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Jenny
Fun water level @ 68,000 c’s. Thanks for sharing. — In Yahoo Canyons Group, curtis kohler wrote:
Try this Jenny >  > http://www.youtube.com/watch?v=OpCsfcThJfY
ÂÂ
> — On Fri, 7/8/11, Jenny wrote:
> From: Jenny To: Yahoo Canyons Group
Date: Friday, July 8, 2011, 9:40 AM
> ÂÂ
Wooo Hooo! Anyone been into Cataract Canyon this season? Photos?
(175% of average). This was below the forecasted volume for June, which was > 6.1 maf (198% of average) but was still the third wettest June on record > since the closure of Glen Canyon Dam. The observed inflow to Lake Powell > peaked on June 11th and 12th at just over 96,000 cfs. Inflows are now > declining but are still averaging about 80,000 cfs (as of July 5, 2011). The > forecasted unregulated inflow volume for July was increased from 3.30 maf to > 3.53 maf (226% of average) which would be the 3rd wettest July for Lake > Powell since the operation of Glen Canyon Dam began in 1963.
>
curtis kohler
Try this Jenny  http://www.youtube.com/watch?v=OpCsfcThJfY ÂÂ
— On Fri, 7/8/11, Jenny jenny.carverbc@gmail.com> wrote:
From: Jenny jenny.carverbc@gmail.com> Subject: [from Canyons Group] Re: RRFW Riverwire – Glen Canyon Dam Update To: Yahoo Canyons Group Date: Friday, July 8, 2011, 9:40 AM
ÂÂ
Wooo Hooo! Anyone been into Cataract Canyon this season? Photos?
Jenny
Wooo Hooo! Anyone been into Cataract Canyon this season? Photos?
riverwire@rrfw.org
RRFW Riverwire Glen Canyon Dam Update July 8, 2011
Glen Canyon Dam Lake Powell
The unregulated inflow volume to Lake Powell for June 2011 was 5.40 maf (175% of average). This was below the forecasted volume for June, which was 6.1 maf (198% of average) but was still the third wettest June on record since the closure of Glen Canyon Dam. The observed inflow to Lake Powell peaked on June 11th and 12th at just over 96,000 cfs. Inflows are now declining but are still averaging about 80,000 cfs (as of July 5, 2011). The forecasted unregulated inflow volume for July was increased from 3.30 maf to 3.53 maf (226% of average) which would be the 3rd wettest July for Lake Powell since the operation of Glen Canyon Dam began in 1963.
The reservoir elevation of Lake Powell has increased significantly so far this runoff season. On April 9, 2011 the elevation of Lake Powell was 3609.7 feet above sea level which was the lowest elevation observed so far in 2011. Since that time the elevation of Lake Powell has increased by 42.7 feet to 3652.4 feet on July 5, 2011. The elevation is projected to continue to rise and should peak near 3660 by the end of July. The last time Lake Powell’s reservoir elevation was at this level was in October of 2001 (over 10 years ago) near the beginning of the recent drought.
Current Dam Operations
Releases from Glen Canyon Dam are approximately 24,400 cfs which is very near the full capacity of the powerplant. This release rate includes reserving enough generation capacity for up to 100 MW of reserve generation and 40 MW of system regulation. As the elevation of Lake Powell increases, the capacity of the powerplant will change and operation of Glen Canyon Dam will be adjusted daily to maximize release volumes. It is anticipated that the release volume for July will be approximately 1,465 kaf. The actual release volume for July will largely depend on generation unit efficiencies that occur throughout the month and could be higher or lower than this estimated release volume.
While the release rate over the next several months is likely to be steady, the instantaneous releases from Glen Canyon Dam may fluctuate somewhat to provide 40 MW of system regulation. These instantaneous release adjustments maintain stable conditions within the electrical generation and transmission system and result in momentary release fluctuations within a range of about 1100 cfs above or below the targeted hourly release rate. The momentary fluctuations for regulation are very short lived and typically balance out over the hour.
Spinning and non-spinning reserve generation is also maintained at Glen Canyon Dam. In order for Colorado River Storage Project (CRSP) powerplants to participate in the electrical generation and transmissions system, these powerplants must maintain a level of generation capacity available in reserve to assist the local control area for when unanticipated generation outages occur. The current CRSP powerplant reserve requirement is 100 MW (equivalent to approximately 2,675 cfs of release from Glen Canyon Dam). When an electrical outage occurs within the control area, CRSP powerplants can be called upon to provide up to 100 MW of additional generation for up to 2 hours. Under normal circumstances, calls for reserves infrequent and for much less than the required 100 MW. Because Glen Canyon Powerplant is the largest facility of the CRSP powerplants, most of the CRSP reserve requirement is maintained at Glen Canyon Dam.
Annual Operations-Coordinated Operation of Lake Mead and Lake Powell under Interim Guidelines for Water Year 2011
In August of 2010, the 24-Month Study was used to project the January 1, 2010 elevations of Lake Powell and Lake Mead. Based on these projected elevations and pursuant to the December 2007 Record of Decision on Colorado River Interim Guidelines for Lower Basin Shortages and the Coordinated Operations of Lake Powell and Lake Mead (Interim Guidelines), the operating tier for water year 2011 was selected to be Upper Elevation Balancing. Operation of Glen Canyon Dam under Upper Elevation Balancing can result in annual releases as low as 7.0 maf to as high as 13 maf or greater depending on system conditions. The operational outcome of the Upper Elevation Balancing Tier is largely dependent on system conditions at the end of the water year that are projected in the April 24-Month Study.
The April 2011 24-Month Study projected the end of water year elevation for Lake Powell would be above 3643 feet which is the Equalization Level for 2011. For this reason, pursuant to the Interim Guidelines, Equalization will govern the operation of Glen Canyon Dam for the remaining months of water year 2011. For more information on the Interim Guidelines click http://www.usbr.gov/lc/region/programs/strategies/RecordofDecision.pdf
Current Inflow Forecasts and Model Projections
The Water Supply forecast for Lake Powell (April through July Unregulated Inflow Volume) is 12.0 maf (151% of average) and the water year unregulated inflow to Powell for 2011 is projected to be 16.2 maf (135% of average). The unregulated inflow forecasts for Lake Powell over the next 3 months are as follows: July-3,530 kaf (226% of average); August-950 kaf (155% of average): September-670 kaf (141% of average). These forecasts were last updated on July 1, 2011. Incorporating these new forecasts, the projected most probable unregulated inflow for water year 2011 is now 16.2 maf (131% of average). This is the median projection for water year 2011. There is a 50% chance that the actual volume could be higher and there is a 50% the actual volume could be lower than this projected volume.
The June 24-Month Study projects a Lake Powell WY 2011 annual release volume of 12.44 maf. Due to recent increases to the inflow forecast for Lake Powell, Equalization may not be fully achieved by the end of the water year. The projected Lake Powell releases will be updated each month to reflect changing hydrology in order to achieve the operation specified by the Equalization Tier.
The July 2011 24-Month Study will published on July 8, 2011 and will be available here: http://www.usbr.gov/uc/water/crsp/studies/24Month_07.pdf
Updated elevation projections for Lake Powell through water year 2011 and 2012 based on the most recently published 24-Month Study are maintained at:
http://www.usbr.gov/uc/water/crsp/studies/lppwse.html
Upper Colorado River Basin Hydrology
The Upper Colorado River Basin has experienced a protracted multi-year drought since early 2000. During this drought, the inflows to Lake Powell have been below average in every year except water years 2005, 2008 and likely 2011. In the summer of 1999, Lake Powell was close to full with reservoir storage at 23.5 million acre-feet, or 97 percent of capacity. During the next 5 years (2000 through 2004) unregulated inflow to Lake Powell was well below average. This resulted in Lake Powell storage decreasing during this period to 8.0 million acre-feet (33 percent of capacity) which occurred on April 8, 2005.
During 2005, 2008 and 2009, drought conditions eased somewhat with near or above average inflow conditions and net gains in storage to Lake Powell. This year (2011) will likely be another above average inflow year. As of July 5, 2011 the storage in Lake Powell was approximately 17.52 million acre-feet (72.0 % of capacity) which is still below the desired operating level for this time of year. The overall reservoir storage in the Colorado River Basin as of July 5, 2011 is approximately 37.48 million acre-feet (63.0 % of capacity).
RRFW thanks Rick Clayton of the USBOR for this information.
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RRFW Riverwire – Glen Canyon Dam Update June 8, 2011
Glen Canyon Dam Lake Powell
The unregulated inflow volume to Lake Powell for May 2011 was been 2.35 million acre feet (maf) (102% of average). Inflows have increased due to snowmelt runoff within the basin and observed inflows to Lake Powell are averaging nearly 75,000 cubic feet per second (cfs). Observed inflows will likely continue to increase in June and could reach levels near 140,000 cfs by late June. The spring runoff is well under way and there is still significant snow yet to melt at the higher elevations within the basin. Inflows will likely be very high over the next 2 months. The forecasted unregulated inflow for June is 6.1 maf which would be the 2nd wettest June for Lake Powell since the initial operation of Glen Canyon Dam began in 1963.
The elevation of Lake Powell will increase significantly during the months of June and July, 2011. As of June 7, 2011 the elevation of Lake Powell was 3628.4 feet which is about 19 feet above the low elevation of the year (3609.7 feet on April 9, 2011). During June and July, the elevation will likely increase rapidly and is projected to reach a peak elevation for the year in early August 2011 of approximately 3660 to 3665 feet above sea level. This would be 35 to 40 feet below the full pool elevation of 3700 feet. The last time Lake Powell was at an elevation in this range was in October of 2001 near the beginning of the most current drought.
Current Dam Operations
The releases from Glen Canyon Dam are approximately 22,400 cfs which is very near the full capacity of the power plant allowing for 100 megawatts of reserve generation and 40 megawatts of regulation. As the elevation of Lake Powell increases, the capacity of the power plant will also increase and operation of the power plant will be adjusted day by day to release the maximum volume possible. It is anticipated that the release volume for June will be approximately 1,369 kaf with 7 generating units operating at full capacity. The actual release volume for June will largely depend on the generation unit efficiencies that occur throughout the month and could be higher or lower than this anticipated volume.
While the release rate over the next several months is likely to be steady at or near full power plant capacity, the instantaneous releases from Glen Canyon Dam may fluctuate somewhat to provide approximately 40 megawatts of system regulation. These instantaneous release adjustments maintain stable conditions within the electrical generation and transmission system and result in momentary release fluctuations within a range of about 1100 cfs above or below the targeted hourly release rate. The momentary fluctuations for regulation are very short lived and typically balance out over the hour.
Spinning and non-spinning reserve generation is also maintained at Glen Canyon Dam. In order for Colorado River Storage Project (CRSP) power plants to participate in the electrical generation and transmissions system, these dams must maintain a level of generation capacity in reserve to assist the local control area to maintain electrical supply when unanticipated generation outages occur within the control area. The CRSP power plants are required to maintain 100 megawatts (approximately 2,675 cfs of release) of capacity in reserve for these unanticipated outages. When an electrical outage occurs, CRSP power plants can be called upon to provide up to an additional 100 megawatts of generation above what was originally scheduled for a duration of 2 hours or less. Under normal circumstances, calls for reserve generation occur fairly infrequently and are for much less than the required 100 megawatts. Because Glen Canyon Power plant is the largest facility of the CRSP power plants, typically most of the CRSP reserve requirement is maintained there rather than the other CRSP power plants.
Annual Operations-Coordinated Operation of Lake Mead and Lake Powell under Interim Guidelines for Water Year 2011
In August of 2010, the 24-Month Study was used to project the January 1, 2010 elevations of Lake Powell and Lake Mead. Based on these projected elevations and pursuant to the December 2007 Record of Decision on Colorado River Interim Guidelines for Lower Basin Shortages and the Coordinated Operations of Lake Powell and Lake Mead (Interim Guidelines), the operating tier for water year 2011 was selected to be Upper Elevation Balancing. Operation of Glen Canyon Dam under Upper Elevation Balancing can result in an annual release as low as 7.0 maf when balancing or as high as would be required to achieve Equalization which could be as low as 8.23 maf or as high as 13 maf or greater depending on system conditions. The operational outcome of Upper Elevation Balancing is largely dependent on system conditions at the end of the water year that are projected in the April 24-Month Study. For more information on the Interim Guidelines click here: http://www.usbr.gov/lc/region/programs/strategies/RecordofDecision.pdf
Current Inflow Forecasts and Model Projections
Snowpack conditions above Lake Powell that occurred during the winter of 2010-2011 were well above average and resulted in a snowpack condition above Lake Powell on April 10, 2011 that was 119% of average. Typically the snowpack peaks during the first part of April and snow levels normally begin to decrease after about April 10th each year. Temperatures in April of 2011, however, were well below average which allowed the snowpack to continue to build through the month of April. On May 1, 2011 the snowpack above Lake Powell reached its peak level for the year which was approximately 130% of the average seasonal peak snowpack condition. Below average temperatures in the basin persisted in May and by June 1, 2011 only about 30% of the snowpack had melted. The as of June 8, 2011 about 50% of the accumulated snowpack for 2011 had melted. There is still significant snowpack within the basin which will support high inflow conditions for several months.
The Water Supply forecast for Lake Powell (April through July Unregulated Inflow Volume) is now 12.6 maf (159% of average) and the water year unregulated inflow to Powell for 2011 is projected to be 16.7 maf (138% of average). The last water year where Lake Powell observed that level of unregulated inflow was 1997 when the unregulated inflow volume was 17.4 maf (145% of average) and only 5 of 47 years since the closure of Glen Canyon Dam have had unregulated inflow volumes greater than what is projected for this year.
The unregulated inflow forecast for Lake Powell over the next 3 months based on the May preliminary Water Supply forecast is as follows: June-6,100 kaf (198% of average); July-3,300 kaf (212% of average); August-950 kaf (155% of average). This forecast was last updated on June 3, 2011. Incorporating these new forecasts the most probable Lake Powell unregulated inflow volume projection for water year 2011 is 16.7 maf (138% of average). This is the median unregulated inflow volume that is forecasted to occur for water year 2011. There is a 50% chance that the unregulated inflow volume will be higher or lower than this volume. A reasonable range of possible inflows is defined by a minimum probable inflow volume and a maximum probable inflow volume. These volumes represent what would be expected to be achieved or exceeded 90% of the time (minimum inflow volume) and 10% of the time (maximum inflow volume). The forecasted water year (2011) minimum probable inflow volume issued for May is 15.1 maf (125% of average). The forecasted water year (2011) maximum probable inflow volume issued for May is 18.5 maf (154% of average). Given this range, there is still a significant amount of uncertainty for how 2011 will play over the next 4 months.
The May 2011 24-Month Study, with the 2011 most probable inflow condition projected the annual release volume to be 12.46 maf. This release volume is the estimated maximum volume that can be released through Glen Canyon Power plant by September 30, 2011. This annual release volume does not achieve the Equalization objective of the Interim Guidelines by September 30th, 2011. As hydrologic conditions change during the remainder of water year 2011, actual and projected releases from Glen Canyon Dam will be adjusted to achieve the Equalization objective of the Interim Guidelines as practicably as is possible by September 30th, 2011. If the Equalization objective is not achieved by September 30th, releases from Glen Canyon Dam will likely remain at power plant capacity until the Equalization objective is achieved.
Updated elevation projections for Lake Powell through water year 2011 and 2012 based on the most recently published 24-Month Study are maintained at http://www.usbr.gov/uc/water/crsp/studies/lppwse.html
Colorado River Basin Hydrology
In the Upper Colorado River Basin during water year 2010, the overall precipitation accumulated through September 30, 2010 was approximately 90% of average based on the 30 year average for the period from 1971 through 2000. For Water Year 2011 thus far, the estimated monthly precipitation within the Upper Colorado River Basin (above Lake Powell) as a percentage of average has been: (October – 135%, November – 95%, December – 225%, January – 50%, February – 100%, March – 85%, April – 155%, May – 155%)
The Climate Prediction Center outlook (dated May 19, 2011) for temperature over the next 3 months indicates that temperatures in the Upper Colorado River Basin are expected to be above average while precipitation over the next 3 months is projected to be near average in the northern reaches of the basin while below average in the southern reaches of the basin.
Upper Colorado River Basin Drought
The Upper Colorado River Basin has experienced a protracted multi-year drought since early 2000. During this drought, the inflows to Lake Powell have been below average in every year except water years 2005, 2008 and likely 2011. In the summer of 1999, Lake Powell was close to full with reservoir storage at 23.5 million acre-feet, or 97 percent of capacity. During the next 5 years (2000 through 2004) unregulated inflow to Lake Powell was well below average. This resulted in Lake Powell storage decreasing during this period to 8.0 million acre-feet (33 percent of capacity) which occurred on April 8, 2005. During 2005, 2008 and 2009, drought conditions eased somewhat with near or above average inflow conditions and net gains in storage to Lake Powell. 2011 will be another above average inflow year so drought conditions have eased somewhat in the Colorado River Basin over the past 6 years. As of June 7, 2011 the storage in Lake Powell was approximately 14.68 million acre-feet (60.4 % of capacity) which is still below desired levels. The overall reservoir storage in the Colorado River Basin as of June 7, 2011 is approximately 33.82 million acre-feet (56.9 % of capacity).
RRFW thanks Rick Clayton of the USBOR for this information.
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RRFW Riverwire – Glen Canyon Dam Update May 9, 2011
Glen Canyon Dam / Lake Powell
The unregulated inflow to Lake Powell for April 2011 was 983 thousand acre feet (kaf) (100% of average) which was 117 kaf below the level forecasted for April by the Colorado Basin River Forecast Center which was 1100 kaf (112% of average). On April 9, 2011, the elevation of Lake Powell reached 3609.7 feet above sea level which will likely be the lowest level that occurs during water year 2011. As of May 2, 2011 the elevation had increased to 3612.1 feet above sea level. Inflows are averaging about 25,000 cfs while releases are averaging about 14,400 cfs so the elevation is increasing at over 1 inch per day. It is projected that the elevation of Lake Powell could increase by more than 40 feet to a peak elevation of approximately 3655 feet above sea level by late July or early August which would be approximately 45 feet from the full pool elevation of 3700 feet.
Current Dam Operations
The release volume currently scheduled for May is 1103 kaf. Releases in May, from May 1 through May 13 will be near steady at 14,400 cfs. On May 14, 2011 it is projected that Units 3 and 4 will be returned to service. When this occurs, releases from Glen Canyon Dam will be increased such that daily peak releases will be about 22,000 cfs and off peak releases will be about 16,000 cfs.
The projected release volume for June is currently projected to be 1398 kaf to 1458 kaf. Flows in June will likely be steady, with releases between 23,500 cfs and 24,500 cfs during June in all hours. This will be the estimated power plant capacity during that month based on unit performance.
In addition to daily operations that may or may not include daily fluctuation patterns for load following power generation, the instantaneous releases from Glen Canyon Dam may also fluctuate somewhat to provide approximately 40 megawatts of system regulation. These instantaneous release adjustments maintain stable conditions within the electrical generation and transmission system and result in momentary release fluctuations within a range of about 1100 cfs above or below the targeted hourly release rate. The momentary fluctuations for regulation are very short lived and typically balance out over the hour.
Spinning and non-spinning reserve generation is also maintained at Glen Canyon Dam. In order for Glen Canyon Dam (and other Colorado River Storage Project dams) to participate in the electrical generation and transmissions system, Glen Canyon Dam must provide a level of reserve generation to assist the local control area to maintain electrical supply when unanticipated generation unit outages occur within the control area. Glen Canyon is required to maintain 99 megawatts (approximately 2,650 cfs of release) of capacity in reserve for these unanticipated outages. When an electrical outage occurs, Glen Canyon Dam can be called upon to provide up to an additional 99 megawatts of generation above what was originally scheduled for Glen Canyon Dam for a duration of 2 hours or less. Under normal circumstances, calls for reserve generation occur fairly infrequently and are for much less than the required 99 megawatts.
Annual Operations-Coordinated Operation of Lake Mead and Lake Powell under Interim Guidelines for Water Year 2011
In August of 2010, the 24-Month Study was used to projected the January 1, 2010 elevations of Lake Powell and Lake Mead. Based on these projected elevations and pursuant to the December 2007 Record of Decision on Colorado River Interim Guidelines for Lower Basin Shortages and the Coordinated Operations of Lake Powell and Lake Mead (Interim Guidelines), the operating tier for water year 2011 was selected to be Upper Elevation Balancing. Operation of Glen Canyon Dam under Upper Elevation Balancing can result in an annual release as low as 7.0 million acre feet (maf) when Balancing or as high as would be required to achieve Equalization which could be as low as 8.23 maf or as high as 13 maf or greater depending on system conditions. The operational outcome of Upper Elevation Balancing is largely dependent on system conditions at the end of the water year that are projected in the April 24-Month Study. For more information on the Interim Guidelines see:
http://www.usbr.gov/lc/region/programs/strategies/RecordofDecision.pdf
Current Inflow Forecasts and Model Projections
Snowpack conditions above Lake Powell have persisted to be above average since late December 2010. The overall snowpack above Lake Powell on May 2, 2011 was 160% of the seasonal average. The snowpack conditions have continued to build basin wide throughout April when typically snowpack begins to melt in April. Temperatures in the Colorado River Basin have remained below average and this has protected the snowpack beyond what was expected just one month ago. The Water Supply forecast for Lake Powell (April through July Unregulated Inflow Volume) was 9.7 maf (123% of average) at mid-April but has been increased substantially for May which is now 11.5 maf (145% of average). The 2011 water year projected unregulated inflow volume was projected in April to be 13.11 maf (109% of average). With the increased forecast for May the updated 2011 water year projected unregulated inflow volume is now 15.34 maf (127% of average). The last water year where Lake Powell observed that level of unregulated inflow was 1996 when the unregulated inflow volume was 17.05 maf (142% of average) and in the 47 years since the closure of Glen Canyon Dam there have only been 8 years where the unregulated inflow volume was at or above the level projected for this year.
The unregulated inflow forecast for Lake Powell over the next 3 months based on the May preliminary Water Supply forecast is as follows: May-3,000 kaf (130% of average); June-5,200 kaf (169% of average); July-2,300 kaf (148% of average). Incorporating these new forecasts the most probable Lake Powell unregulated inflow volume projection for water year 2011 is 15.34 maf (127% of average). This is the median unregulated inflow volume that is forecasted to occur for water year 2011. There is a 50% chance that the unregulated inflow volume will be higher or lower than this volume. A reasonable range of possible inflows is defined by a minimum probable inflow volume and a maximum probable inflow volume. These volumes represent what would be expected to be achieved or exceeded 90% of the time (minimum inflow volume) and 10% of the time (maximum inflow volume). The forecasted water year (2011) minimum probable inflow volume issued for May is 12.4 maf (103% of average). The forecasted water year (2011) maximum probable inflow volume issued for May is 18.1 maf (150% of average). Given this range, there is still a significant amount of uncertainty for how 2011 will play over the next 5 months.
The April 2011 24-Month Study, with the 2011 most probable inflow condition projects that Equalization will be required under the Interim Guidelines and the projected annual release volume from this study is projected to be 11.56 maf. The increased forecast will almost certainly increase the projected annual release volume when the May 24-month study is completed. As hydrologic conditions change during the remainder of the water year, this annual release volume projection will be adjusted to achieve the objectives of the Equalization Tier of the Interim Guidelines.
The April 2011 24-Month Study has been published and is available here:
http://www.usbr.gov/uc/water/crsp/studies/24Month_12.pdf
Updated elevation projections for Lake Powell through water year 2011 and 2012 based on the most recently published 24-Month Study are maintained at:
http://www.usbr.gov/uc/water/crsp/studies/lppwse.html
Upper Colorado River Basin Hydrology
In the Upper Colorado River Basin during water year 2010, the overall precipitation accumulated through September 30, 2010 was approximately 90% of average based on the 30 year average for the period from 1971 through 2000. For Water Year 2011 thus far, the estimated monthly precipitation within the Upper Colorado River Basin (above Lake Powell) as a percentage of average has been: (October – 135%, November – 95%, December – 225%, January – 50%, February – 100%, March – 90%)
The Climate Prediction Center outlook (dated April 21, 2010) for temperature over the next 3 months indicates that temperatures in the Upper Colorado River Basin are expected to be above average while precipitation over the next 3 months is projected to be near average in the northern reaches of the basin while below average in the southern reaches of the basin.
Upper Colorado River Basin Drought
The Upper Colorado River Basin continues to experience a protracted multi-year drought. Since 1999, inflow to Lake Powell has been below average in every year except water years 2005 and 2008. In the summer of 1999, Lake Powell was close to full with reservoir storage at 23.5 million acre-feet, or 97 percent of capacity. During the next 5 years (2000 through 2004) unregulated inflow to Lake Powell was well below average. This resulted in Lake Powell storage decreasing during this period to 8.0 million acre-feet (33 percent of capacity) which occurred on April 8, 2005. During 2005, 2008 and 2009, drought conditions eased somewhat with near or above average inflow conditions and net gains in storage to Lake Powell. 2011 will be another above average inflow year so drought conditions are easing somewhat in the Colorado River Basin. As of May 2, 2011 the storage in Lake Powell was approximately 12.95 million acre-feet (53.2 % of capacity) which is below desired levels. The overall reservoir storage in the Colorado River Basin as of April 18, 2011 is approximately 31.58 million acre-feet (53.1 % of capacity).
RRFW thanks Rick Clayton of US Bureau of Reclamation for this update.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
RIVERWIRE is a free service to the community of river lovers from River Runners for Wilderness. To join, send an e-mail address to riverwire@rrfw.org and we’ll add it to the RRFW RIVERWIRE e-mail alerts list.
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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RRFW Riverwire – Glen Canyon Dam Update April 8, 2011
Glen Canyon Dam / Lake Powell
The unregulated inflow to Lake Powell for March 2011 was 594 kaf (90% of average). Observed inflows to Lake Powell have increased over the past several weeks and are currently averaging about 10,400 cfs. With daily average release rate from Glen Canyon Dam that is about 16,000 cfs, the elevation of Lake Powell is still declining , but the rate of decline has been moderated by these increased inflow conditions. The elevation of Lake Powell at midnight on April 7, 2011 was 3609.84 feet above sea level (90.16 feet from full pool). The elevation of Lake Powell will begin to increase later in April when inflows exceed releases. It is projected that the elevation of Lake Powell could increase by more than 30 feet to a peak elevation of approximately 3643 feet above sea level by late July or early August.
Current Dam Operations
The release volume scheduled for April is 966 kaf. During the first 3 days of April, daily releases fluctuates for power production between an afternoon peak of approximately 19,600 cfs and an early morning low release of approximately 14,000 cfs. On April 4, 2011, Glen Canyon Powerplant Units 3 and 4 were taken out of service for approximately 6 weeks for annual maintenance. Releases from Glen Canyon Dam were set to 16,000 cfs with no fluctuations for power generation at that time due to limited capacity of the available generating units at Glen Canyon Power Plant. Releases of 16,000 cfs steady will likely continue until the end of April. In early May, releases will likely be steady at about 15,000 cfs for the first 13 days of the month. On May 14, 2011 it is projected that Units 3 and 4 will be returned to service. When this occurs, releases from Glen Canyon Dam will be increased such that peak releases will be about 22,000 cfs and off peak releases will be about 16,000 cfs. The projected release volume for May is approximately 1.10 maf.
In addition to daily operations that may or may not include daily fluctuation patterns for load following power generation, the instantaneous releases from Glen Canyon Dam may also fluctuate somewhat to provide approximately 40 megawatts of system regulation. These instantaneous releases adjustments maintain stable conditions within the electrical generation and transmission system and result in momentary release fluctuations within a range that is about 1100 cfs above or below the targeted release rate for a given hour of the day. These momentary fluctuations for regulation are very short lived and typically balance out over the hour. Spinning and non-spinning reserve generation can also occur at Glen Canyon Dam. When an unanticipated electrical outage event occurs within the electrical transmission system, reserve generation at Glen Canyon Dam can be called upon up to a maximum of 98 megawatts (approximately 2,600 cfs of release) for a duration of up to 2 hours. Under normal circumstances, calls for reserve generation occur fairly infrequently and are for much less than the required 98 megawatts.
Annual Operations-Coordinated Operation of Lake Mead and Lake Powell under Interim Guidelines for Water Year 2011
In August of 2010, the 24-Month Study model projected the January 1, 2010 elevation of Lake Powell and Lake Mead under the most probable inflow scenario. Pursuant to the December 2007 Record of Decision on Colorado River Interim Guidelines for Lower Basin Shortages and the Coordinated Operations of Lake Powell and Lake Mead (Interim Guidelines) and based on this August projection, the operational tier for water year 2011 was selected to be the Upper Elevation Balancing Tier. Under this operational tier, there is a possibility that the annual release volume from Lake Powell could be as low as 8.23 maf and there is also a possibility under this tier that Equalization or Balancing could occur which would result in an annual release volume greater than 8.23 maf.
The possibility of Equalization or Balancing in water year 2011 is dependent upon the reservoir conditions of Lake Powell and Lake Mead projected at the end of the water year in the Most Probable April 24-Month Study when the projected Glen Canyon Dam annual release condition is 8.23 maf . The April 24-Month Study, with a projected water year release of 8.23 maf projects the elevation of Lake Powell on September 30, 2011 (end of water year 2011) to be 3662.63 feet above sea level which is above the Equalization Level for 2011 (3643 feet). Based on this model projection and consistent with the Interim Guidelines, the Equalization Tier will govern the operation of Lake Powell for the remainder of water year 2011.
Current Inflow Forecasts and Model Projections
Snowpack conditions above Lake Powell have persisted to be above average since late December 2010. The overall snowpack above Lake Powell on April 7, 2011 was 115% of average. The current Water Supply forecast for Lake Powell (April through July Unregulated Inflow Volume) is 9.5 maf (120% of average) and this forecast was issued by the CBRFC on April 4, 2011.
The unregulated inflow forecast for Lake Powell over the next 3 months is as follows: April-1,100 kaf (112% of average); May-3,000 kaf (130% of average); June-3,850 kaf (125% of average). Incorporating these new forecasts with the current Water Supply forecast, the projected unregulated inflow volume to Lake Powell during water year 2011 is now 13.11 maf (109% of average). These forecasts combined with projected inflows in August and September of 2011 make up the 2011 Most Probable water year inflow condition. The Most Probable inflow condition has a statistical probability of being achieved that is 50%. In other words, there is a 50% chance that the unregulated inflow volume for water year 2011 for Lake Powell will be 13.11 maf or greater.
A Minimum Probable water year inflow conditions has also been developed for water year 2011. The Minimum Probable inflow condition has a statistical probability of being achieved that is 90%. The 2011 Minimum Probable water year inflow condition is currently 10.5 maf (87% of average). A Maximum Probable water year inflow condition has also been developed for water year 2011. The 2011 Maximum Probable inflow condition is currently 16.2 maf (135% of average).
The April 2011 24-Month Study, with the 2011 Most Probable inflow condition projects that Equalization will be required under the Interim Guidelines and the projected annual release volume is projected to be 11.56 maf. As hydrologic conditions change during the remainder of the water year, this annual release projection will be adjusted to achieve the Equalization Tier of the Interim Guidelines.
Upper Colorado River Basin Hydrology
In the Upper Colorado River Basin during water year 2010, the overall precipitation accumulated through September 30, 2010 was approximately 90% of average based on the 30 year average for the period from 1971 through 2000. For Water Year 2011 thus far, the estimated monthly precipitation within the Upper Colorado River Basin (above Lake Powell) as a percentage of average has been: (October – 135%, November – 95%, December – 225%, January – 50%, February – 100%, March- 90%)
The Climate Prediction Center outlook (dated March 17, 2010) for temperature over the next 3 months indicates that temperatures in the Upper Colorado River Basin are expected to be above average while precipitation over the next 3 months is projected to be near average in the northern reaches of the basin while below average in the southern reaches of the basin.
Upper Colorado River Basin Drought
The Upper Colorado River Basin continues to experience a protracted multi-year drought. Since 1999, inflow to Lake Powell has been below average in every year except water years 2005 and 2008. In the summer of 1999, Lake Powell was close to full with reservoir storage at 23.5 million acre-feet, or 97 percent of capacity. During the next 5 years (2000 through 2004) unregulated inflow to Lake Powell was well below average. This resulted in Lake Powell storage decreasing during this period to 8.0 million acre-feet (33 percent of capacity) which occurred on April 8, 2005. During 2005, 2008 and 2009, drought conditions eased somewhat with net gains in storage to Lake Powell. As of April 7, 2011 the storage in Lake Powell was approximately 12.71 million acre-feet (52.2 % of capacity) which is below desired levels. The overall reservoir storage in the Colorado River Basin as of April 7, 2011 is approximately 31.42 million acre-feet (52.8 % of capacity).
RRFW thanks Rick Clayton, US Bureau of Reclamation for this update.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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RRFW Riverwire – Glen Canyon Dam Update January 11, 2011
Glen Canyon Dam – Lake Powell
During December 2010 the unregulated inflow to Lake Powell was 417 thousand acre feet (kaf) (96% of average). This was 57 kaf above the volume forecasted by the Colorado Basin River Forecast Center (CBRFC) on December 1, 2010 which was 360 kaf (83% of average). The elevation of Lake Powell at the end of the day on December 31, 2010 was 3626.54 feet above sea level (73.46 feet from full pool) which corresponds to a live storage content of 14.44 maf (59.5% of capacity).
During the last half of December, precipitation within the Upper Colorado River Basin was well above average and the snowpack conditions have increased significantly. On December 17, 2010 the snowpack above Lake Powell was estimated to be 102% of average. By December 31, 2010 the snowpack conditions above Lake Powell had increased to an estimated 151% of average. Precipitation above Lake Powell for the first 3 months of water year 2011 has been well above average at nearly 150% of average.
Based on these conditions and projected climate conditions over the next several months, the CBRFC has issued the Final Water Supply Forecast (April through July 2011 forecasted unregulated inflow volume) for Lake Powell that is well above average at 9.5 million acre feet (maf) which is 120% of average. This forecast translates into an increase to the expected inflow to Lake Powell for water year 2011 that is more than 3 million acre-feet more than what was projected one month ago.
Operation of Glen Canyon Dam during January 2011 has been modified based on this new forecast. On Sunday January 9, 2011, releases from Glen Canyon Dam were increased to an average daily release volume of approximately 34,000 acre-feet which translates to an average daily release of 17,100 cfs. Releases are scheduled to peak for power generation during the afternoon hours for the remainder of January to 20,500 cfs. Releases during the early morning hours are approximately 12,500 cfs.
The release volume for February is projected to be 981,000 kaf which the estimated capacity of Glen Canyon Power plant under the scheduled maintenance unit outage plan with an allowance of capacity to provide spinning reserves and regulation. It is anticipated that fluctuations for power generation will be minimal in February and the estimated release rate will likely be approximately 17,600 cfs.
In addition to the daily fluctuation pattern for power generation, the instantaneous releases from Glen Canyon Dam may also fluctuate somewhat to provide approximately 40 megawatts of system regulation. These instantaneous releases adjustments maintain stable conditions within the electrical generation and transmission system and result in momentary release fluctuations within a range that is about 1100 cfs above or below the targeted release rate for a given hour of the day. These momentary fluctuations for regulation are very short lived and typically balance out over the hour. Spinning and non-spinning reserve generation is also maintained at Glen Canyon Dam. When an unanticipated electrical outage event occur within the electrical transmission system, this reserve generation at Glen Canyon Dam can be called upon up to a limit of 98 megawatts (approximately 2,600 cfs of release) for a duration of up to 2 hours. Under normal circumstances, calls for reserve generation occur fairly infrequently and are for much less than the limit of 98 megawatts.
In August of 2010, the August 2010 24-Month Study Model was used to project the January 1, 2010 elevation of Lake Powell and Lake Mead under the most probable inflow scenario. Pursuant to the Interim Guidelines and based on this August projection, the operational tier for water year 2011 was determined to be the Upper Elevation Balancing Tier. Under the Upper Elevation Balancing Tier, there is a possibility that the annual release volume from Lake Powell could be 8.23 maf. There is also a possibility under this tier that Equalization or Balancing could occur in 2011 which would result in an annual release volume greater than 8.23 maf.
The possibility of Equalization or Balancing in 2011 is dependent on the end of water year 2011 reservoir conditions projected in the April 2011 24-Month Study under the most probable inflow scenario and with 8.23 maf projected for release from Lake Powell during water year 2011. For this reason it will not be known for certain whether Equalization or Balancing will occur in water year 2011 until April 2011. 24-Month Studies prior to April 2011 can project that Equalization or Balancing are likely to occur, but these projections are subject to change with changes in the forecasted hydrology of the Colorado River Basin. It is possible that a relatively small change in forecasted hydrology can have a large impact on the projected annual release volume.
The January 2011 24-Month Study with the most probable inflow scenario for water year 2011 projects that Equalization is likely to occur in 2011. For this reason, the projected most probable annual release volume for water year 2011 in the January 24-Month Study is 11.367 maf. Given the current range of uncertainty of the forecasted hydrology for water year 2011, it is possible that Balancing could also occur in water year 2011 which would result if the annual release being 9.0 maf. Each month the 24-Month Study is updated to reflect the most probable inflow scenario which is based on the most recent forecast from the Colorado River Basin Forecast Center (CBRFC). Analysis of the probable range of inflows that could occur during water year 2011 indicates that the probability of realizing an inflow volume that would trigger Equalization in 2011 is currently about 76%. This probability will be updated again during the first part of February 2011.
The unregulated inflow forecast for Lake Powell over the next 3 months is as follows: January-380 kaf (94% of average); February-380 kaf (90% of average); March-670 kaf (101% of average). The outlook for water year 2011, incorporating this new forecast and the January Final Water Supply Forecast, the most probable unregulated inflow volume to Lake Powell during water year 2011 is now 13.19 maf (110% of average). It is possible that the unregulated volume of inflow to Lake Powell in water year 2011 will be greater than or less than the most probable projection. The probable range of unregulated inflow volumes to Lake Powell during water year 2011 is currently projected to be as dry as 8.9 maf (74% of average) to as wet as 18.6 maf (154% of average).
Upper Colorado River Basin Hydrology
In the Upper Colorado River Basin during water year 2010, the overall precipitation accumulated through September 30, 2010 was approximately 90% of average based on the 30 year average for the period from 1971 through 2000. For Water Year 2011 thus far, the estimated monthly precipitation within the Upper Colorado River Basin (above Lake Powell) as a percentage of average has been: (October – 135%, November – 95%,December -230%).
The Climate Prediction Center outlook (dated December 16, 2010) for temperature over the next 3 months indicates that temperatures in the Upper Colorado River Basin are expected to be near average while precipitation over the next 3 months is also projected to be near average.
Upper Colorado River Basin Drought
The Upper Colorado River Basin continues to experience a protracted multi-year drought. Since 1999, inflow to Lake Powell has been below average in every year except water years 2005 and 2008. In the summer of 1999, Lake Powell was close to full with reservoir storage at 23.5 million acre-feet, or 97 percent of capacity. During the next 5 years (2000 through 2004) unregulated inflow to Lake Powell was well below average. This resulted in Lake Powell storage decreasing during this period to 8.0 million acre-feet (33 percent of capacity) which occurred on April 8, 2005. During 2005, 2008 and 2009, drought conditions eased somewhat with net gains in storage to Lake Powell. As of January 10, 2011 the storage in Lake Powell was approximately 14.26 million acre-feet (58.6 % of capacity) which is below desired levels. The overall reservoir storage in the Colorado River Basin as of January 10, 2011 is approximately 32.29 million acre-feet (54.3 % of capacity).
RRFW thanks Rick Clayton of the USBOR for this update.
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Join RRFW’s listserver to stay abreast of and participate in the latest river issues. It’s as easy as sending a blank e-mail to Rafting_Grand_Canyon-subscribe@yahoogroups.com
Check out RRFW’s Rafting Grand Canyon Wiki for free information on Do-It-Yourself Grand Canyon rafting info http://www.rrfw.org/RaftingGrandCanyon/Main_Page
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