RRFW Riverwire – Glen Canyon Dam Update March 8, 2005
Upper Colorado River Basin Hydrology
The Colorado River Basin has now completed 5 consecutive years of severe drought. In the summer of 1999 Lake Powell was essentially full, with reservoir storage at 97 percent of capacity. Since that time, inflow volumes have been below average for 5 consecutive water years. Total unregulated inflow to Lake Powell in water year 2004 was only 51 percent of average. Unregulated inflow in water years 2000, 2001, 2002, and 2003 was 62, 59, 25, and 51 percent of average, respectively. Inflow in water year 2002 was the lowest ever observed since the completion of Glen Canyon Dam in 1963.
Hydrologic conditions have improved over the past 6 months in the Colorado River Basin. Since September 2004, precipitation in the basin has been above average. Snowpack in the basin above Lake Powell is currently 116 percent of average (as of March 8, 2005).
Inflow to Lake Powell, as a percentage of average, has increased since last summer in response to the precipitation events last fall and winter. November 2004 was the first month with above average inflow to Lake Powell since September 1999. Unregulated inflow in January and February was 128 and 118 percent of average, respectively.
As of March 8, 2005, the elevation of Lake Powell is 3,558.4 feet (141.6 feet from full pool). Current storage is 8.21 million acre- feet (34 percent of live capacity).
The National Weather Service (in their March final inflow forecast) is forecasting 8.6 million acre-feet of unregulated inflow to Lake Powell this April through July. This is 108 percent of average.
The water surface elevation of Lake Powell is projected to gradually decline until early-April 2005. Current projections show the lake decreasing to an elevation of about 3,556 feet by early-April. The elevation of Lake Powell is projected to increase from April through mid-July of 2005. Current projections (using the March final inflow forecast) show Lake Powell reaching a peak water surface elevation in July 2005 of about 3,603 feet.
It should be noted, however, there is uncertainty with these projections. Weather conditions this spring will likely result in shifts to inflow projections in 2005.
Operations * Experimental Releases
Daily high fluctuating releases from Glen Canyon Dam, as part of the Glen Canyon Dam experimental flows, are being implemented from January 2, 2005 through the first week of April 2005. On Mondays through Saturdays, releases will range between 5,000 cubic feet per second (cfs) and 20,000 cfs. The 20,000 cfs release will be maintained for about 11 hours (from 9:00 am until about 8:00 pm) and the 5,000 cfs release will be maintained for about 6 hours (from 1:00 am until about 7:00 am). The other hours are transitional, where releases will be between the daily high and the daily low. Releases on Sundays will range between a low of about 5,000 cfs to a high of about 8,000 cfs.
The January through March high fluctuating releases are intended to benefit the endangered humpback chub. These flows helped keep the non-native fish, especially the rainbow and brown trout, in check. The trout are thought to prey upon and compete with native fish such as the endangered humpback chub. This is the third consecutive year of high fluctuating winter releases.
The monthly release volume in March 2005 is scheduled to be 807,000 acre-feet, which averages out to about 14,000 cfs per day on Mondays through Saturdays and 6,700 cfs per day on Sundays. On April 8, 2005 high fluctuating releases are scheduled to end. Releases will be lower in April. A volume of 505,000 acre-feet is scheduled to be released in April.
On November 21, 2004, releases from Glen Canyon Dam were increased for a high-flow experiment. Releases were increased to 41,000 cfs, with this release level maintained for 60 hours. For additional information on the high-flow experiment go to: http://137.77.133.1/uc/feature/GCtestflow/index.html
Because of the draw down condition of Lake Powell, releases from Lake Powell in water year 2005 are being scheduled to meet the minimum release objective of 8.23 million acre-feet. Experimental releases will not change the total volume of water to be released from Lake Powell in water year 2005.
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RRFW Riverwire – Glen Canyon Dam Update December 21, 2010
During December 2010, through the first 19 days of the month, the unregulated inflow to Lake Powell has been tracking towards a monthly volume of 383 kaf (88% of average). This volume is slightly above the volume forecasted for December by the Colorado Basin River Forecast Center on December 1, 2010 which was 360 kaf (83% of average). Although the inflow to Lake Powell during December is projected to be above what was forecasted at the beginning of December, the water surface elevation of Lake Powell at the end of December will likely be about 0.3 feet below what was projected in the December 24-Month Study. The December 24-Month Study projected that Lake Powell would end December at an elevation of 3626.4 feet above sea level. The elevation of Lake Powell at the end of the day on December 31, 2010 will likely be about 3626.1 feet above sea level. The end of month storage in Lake Powell for December 2010 will likely be about 14.6 million acre feet (maf) which is 60.1% of the full capacity of 24.32 maf.
The release volume scheduled for December is 845 thousand acre feet (kaf) which is equivalent to an average daily release rate of approximately 13,750 cubic feet per second (cfs). Daily fluctuations during December have been and will continue to peak near 16,000 cfs during the morning and early evening hours. Daily low releases have been and will continue to occur during the early morning hours (i.e. midnight to about 6:00 am) to about 8,500 cfs. The projected release volume for January is currently 865 kaf which is equivalent to an average daily release rate of approximately 14,050 cfs. The daily peak and low release rate in January will likely also range from 16,000 cfs to about 9,500 cfs respectively.
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 occurs 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 selected 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 December 2010 24-Month Study with the most probable inflow scenario for water year 2011 did project that Balancing is likely to occur in 2011. For this reason, the projected most probable annual release volume for water year 2011 in the December 24-Month Study was 9.00 maf. Given the current range of uncertainty of the forecasted hydrology for water year 2011, it is possible that Equalization could also occur in water year 2011 which would result if the annual release being greater than about 10.7 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). In January, the CBRFC will issue the first water supply forecast for 2011. This new forecast could potentially change the most probable inflow scenario and projected annual release from Glen Canyon Dam.in the January 24-Month Study. Analysis of the probable range of inflows that could occur during water year 2011 indicates that the probability of Equalization occurring in 2011 is currently about 48%. This probability will be updated during the first part of January 2011.
The unregulated inflow forecast for Lake Powell over the next 3 months is as follows: December-360 kaf (83% of average); January-350 kaf (86% of average); February-350 kaf (83% of average). The outlook for water year 2011, incorporating this new forecast, projects the most probable unregulated inflow volume to Lake Powell during water year 2011 to be 9.66 maf (80% 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 4.5 maf (37% of average) to as wet as 15.8 maf (131% of average).
The December 2010 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%)
The Climate Prediction Center outlook (dated November 18, 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.
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 December 19, 2010 the storage in Lake Powell was approximately 14.61 million acre-feet (60.1 % of capacity) which is below desired levels. The overall reservoir storage in the Colorado River Basin as of December 19, 2010 is approximately 32.19 million acre-feet (54.1 % of capacity).
RRFW thanks Rick Clayton of the USBOR for this update.
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RRFW Riverwire – Glen Canyon Dam Update October 27, 2010
Glen Canyon Dam Lake Powell
During October 2010 the unregulated inflow volume to Lake Powell through October 26, 2010 is tracking towards a monthly volume of was 330 thousand acre feet (kaf) (60% of average). This volume will be below the volume forecasted for October which was 375 kaf (69% of average). However, due to significant local precipitation in the region around Lake Powell, the elevation of Lake Powell will likely be about 0.7 feet above the level projected in the October 24-Month Study for the end of October. The elevation of Lake Powell on October 31, 2010 will likely be approximately 3633.75 feet above sea level which corresponds to a live storage of approximately 15.30 maf and 62.9% of the full capacity of 24.32 million acre feet (maf).
On November 1, 2010, the releases from Glen Canyon Dam will resume normal fluctuations for power generations each day. During September and October 2010, the releases were steady with no fluctuations for power generation as part of a 5 year study of steady flows pursuant to the February 2008 Finding of No Significant Impact ‘Experimental Releases from Glen Canyon Dam, Arizona 2008 through 2012’. This was the third year of steady flows of the 5 year study. The steady release rate for this year was 8,000 cubic feet per second (cfs). The volume released during September was 480 kaf and the volume released in October will be approximately 495 kaf.
The release volume scheduled for November is 810 kaf which is equivalent to an average daily release rate of approximately 13,600 cfs. Daily fluctuations will likely peak near 16,000 cfs during the morning and afternoon and evening hours. Daily low releases will occur during the early morning hours (i.e. midnight to about 6:00 am) and will be about 8,000 cfs. The projected release volume for December is currently 865 kaf which is equivalent to an average daily release rate of approximately 14,050 cfs. According to Bureau of Reclamation officials, the daily peak and low release rate in December and January will likely also range from 16,000 cfs to 8,000 cfs respectively.
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 83 megawatts (approximately 2,250 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 83 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 selected 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 October 2010 24-Month Study with the most probable inflow and an 8.23 maf release does project that Balancing is likely to occur in 2011. For this reason, the projected most probable annual release volume for water year 2011 in the October 24-Month Study is 9.00 maf. Given the current range of uncertainty of the forecasted hydrology for water year 2011, it is possible that Equalization could occur in water year 2011 which would result if the annual release being greater than 10.7 maf. Analysis of the probable range of inflows that could occur during water year 2011 indicate that the probability of Equalization occurring in 2011 is currently about 50%.
The current inflow forecast for Lake Powell projects the most probable unregulated inflow volumes for the next 3 months as follows: October-375 kaf (69% of average; November-400 kaf (73% of average); December-375 kaf (86% of average). The outlook for water year 2011 (dated October 3, 2010) projected the most probable unregulated inflow volume to Lake Powell during water year 2011 to be 9.60 maf (80% 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 4.5 maf (37% of average) to as wet as 15.8 maf (131% of average).
The October 2010 24-Month Study has been published and is available here:
http://www.usbr.gov/uc/water/crsp/studies/24Month_10.pdf
The November 2010 24-Month Study will be published by November 10, 2010. 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, 2009 was approximately 90% of average based on the 30 year average for the period from 1971 through 2000. For October 2010, the first month of water year 2011, precipitation in the Upper Colorado River Basin has been above normal and as of October 26th is 170% of average.
The Climate Prediction Center outlook (dated October 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.
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 October 26, 2010 the storage in Lake Powell was 15.32 million acre-feet (63.0 % of capacity) which is still below desired levels while the overall reservoir storage in the Colorado River Basin as of October 26, 2010 is 32.84 million acre-feet (55.2 % of capacity).
RRFW thanks Rick Clayton of the USBOR for his assistance in providing information for this notification.
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RRFW Riverwire – Glen Canyon Dam Update September 28, 2010
Glen Canyon Dam Lake Powell
During September 2010 through September 26, 2010 the unregulated inflow volume to Lake Powell is trending towards 266 thousand acre feet (kaf) (56% of average). This will be approximately 144 kaf below what was projected in the September 24-Month Study and as a result the elevation of Lake Powell at the end of September will be about 1 foot lower than what was projected in the September 24-Month Study. The September 30th elevation of Lake Powell will likely be approximately 3633.7 feet above sea level. This projected ending elevation corresponds to a live storage of 15.27 million acre feet (maf) which is 62.8% of the full capacity of 24.32 maf.
During August the release volume from Glen Canyon Dam was 801.7 kaf and the hourly releases during most days fluctuated between a peak of 16,500 cubic feet per second (cfs) during the day and a low of 8,500 cfs during the evening and early morning for power generation. On September 1, 2010 and continuing through October 31, 2010, the releases from Glen Canyon Dam will be steady with no fluctuations for power production (excluding system regulation and spinning reserves) for the steady flow experiment pursuant to the February 2008 Finding of No Significant Impact Experimental Releases from Glen Canyon Dam, Arizona 2008 through 2012. This will be the third year of steady flows of the 5 year experiment. The steady release rate is 8,000 cfs which is equivalent to a monthly release volume of approximately 476,000 acre-feet in September 2010 and 492,000 acre-feet in October 2010.
During the steady flow experiment the instantaneous releases from Glen Canyon Dam may fluctuate somewhat to provide approximately 40 megawatts (approximately 1,100 cfs) of system regulation to maintain stable conditions within the electrical generation and transmission system. This translates into momentary release fluctuations of about +/- 1100 cfs above or below the targeted steady release target (8000 cfs). These momentary fluctuations for regulation are very short lived and will typically balance out over the hour. Spinning and non-spinning reserve generation will also be carried at Glen Canyon Dam during the steady flow experiment. When an unanticipated outage event occurs in the generation system, reserve generation at Glen Canyon Dam can also be called upon up to a limit of 83 megawatts (approximately 2,250 cfs of release) 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 limit of 83 megawatts.
The August 2010 24-Month Study (most probable inflow scenario) projected the January 1, 2011 elevation of Lake Powell to be 3628.73 feet. Pursuant to the Interim Guidelines, the determination is that the Operational Tier for water year 2011 will be the Upper Elevation Balancing Tier. Under this Operational Tier, there is a possibility that the annual release volume from Lake Powell could be 8.23 maf. There is also a possibility 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 will depend on the reservoir conditions projected for the end of water year 2011 in the April 2011 24-Month Study with the most probable inflow scenario and 8.23 maf projected for release from Lake Powell. The September 2010 24-Month Study indicates that Equalization is likely to be triggered in April 2011 and the annual release volume for water year 2011 is projected to be 11.28 maf.
There is a high level of uncertainty regarding the hydrologic conditions that will be experienced in water year 2011. Each month, the 24-Month Study will be updated to reflect current reservoir conditions and the most probable inflow forecast. The projected annual release volume for water year 2011 in the 24-Month Study will reflect the implementation of the Upper Elevation Balancing Tier with updated hydrologic conditions and is therefore likely to change each month. It is possible that a relatively small change in the forecast could have a large impact on the projected annual release volume. Based on the current inflow forecast (dated September 1, 2010), there is approximately a 58% probability that Equalization will occur in water year 2011.
The current inflow forecast for Lake Powell projects the most probable unregulated inflow volumes for the next 3 months as follows: Sepember-400 kaf (84% of average); October-475 kaf (87% of average; November-460 kaf (84% of average). The outlook for water year 2011 (dated August 3, 2010) projected the most probable unregulated inflow volume to Lake Powell during water year 2011 to be 10.75 maf (89% of average). It is likely the unregulated volume of inflow to Lake Powell in water year 2011 will be greater than or less than the most probable projection. The range of possible unregulated inflow volumes to Lake Powell is currently projected to be as dry as 5.0 maf (40% of average) to as wet as 17.1 maf (142% of average). In October, this hydrologic outlook for water year 2011 will be updated.
The September 2010 24-Month Study has been published and is available here:
http://www.usbr.gov/uc/water/crsp/studies/24Month_09.pdf
Updated elevation projections for Lake Powell through water year 2010 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 2009, the overall precipitation accumulated through September 30, 2009 was approximately 95% of average based on the 30 year average for the period from 1971 through 2000. For water year 2010 dry conditions have persisted. Estimated percentages of average precipitation for the months thus far in water year 2010 are as follows: October 85%, November 40%, December 130%, January 100% and February 100%, March 90%, April 120%, May 75%, June 100%, July 95%. The overall estimated precipitation percentage of average thus far in water year 2010 for the Upper Colorado River Basin is 96% of average.
The Climate Prediction Center outlook (dated August 19, 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 below 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 maf, 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 maf (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 September 1, 2010 the storage in Lake Powell was 15.36 maf (63.1 % of capacity) which is still below desired levels while the overall reservoir storage in the Colorado River Basin as of September 1, 2010 is 33.73 maf (56.7 % of capacity).
RRFW thanks Rick Clayton of the USBOR for his assistance in providing information for this notification.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 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 September 3, 2010
Glen Canyon Dam Lake Powell
The unregulated inflow volume into Lake Powell for August 2010 was 504 thousand acre feet (kaf ) or 82% of average. The elevation of Lake Powell decreased during the month of August by approximately 2 feet from 3636.5 feet at the beginning of August to 3634.5 feet at the end of August. This ending elevation corresponds to a live storage of 15.37 million acre feet (maf) which is 63.2% of the full capacity. During the month of August the release volume from Glen Canyon Dam was 801.7 kaf and the hourly releases during most days fluctuated for power generation between a peak of 16,500 cubic feet per second (cfs) during the day and a low of 8,500 cfs during the evening and early morning.
On September 1, 2010 and continuing through October 31, 2010, the releases from Glen Canyon Dam will be steady with no fluctuations for power production (excluding system regulation and spinning reserves) for the steady flow experiment pursuant to the February 2008 Finding of No Significant Impact ‘Experimental Releases from Glen Canyon Dam, Arizona 2008 through 2012’. This year will be the third year of steady flows of the 5 year experiment. The steady release rate is 8,000 cfs which is equivalent to a monthly release volume of approximately 476,000 acre-feet in September 2010 and 492,000 acre-feet in October 2010.
During the steady flow experiment the instantaneous releases from Glen Canyon Dam may fluctuate somewhat to provide approximately 40 megawatts (approximately 1,100 cfs) of system regulation to maintain stable conditions within the electrical generation and transmission system. This translates into momentary release fluctuations of about +/- 1100 cfs above or below the targeted steady release target (8000 cfs). These momentary fluctuations for regulation are very short lived and will typically balance out over the hour. Spinning and non-spinning reserve generation will also be carried at Glen Canyon Dam during the steady flow experiment. When an unanticipated outage event occurs in the generation system, reserve generation at Glen Canyon Dam can also be called upon up to a limit of 83 megawatts (approximately 2,250 cfs of release) 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 limit of 83 megawatts.
Pursuant to the Colorado River Interim Guidelines for Lower Basin Shortages and Coordinated Operations for Lakes Powell and Mead (Interim Guidelines) the operational tier for water year 2010 is Upper Elevation Balancing and the projected water year release volume is 8.23 maf. Under this operational tier there was a possibility that Equalization could occur in 2010 if the April 2010 24-Month Study, with 8.23 maf projected for release during water year 2010, indicated a Lake Powell projected elevation on September 30, 2010 greater than 3642 feet above sea level (the Equalization level for water year 2010). This condition was not projected in the April 24-Month Study and for this reason, the release volume for water year 2010 will be 8.23 maf. Monthly release volumes for the remainder of the water year will be scheduled to achieve this water year release volume.
The August 2010 24-Month Study projects that operation tier for Glen Canyon Dam in water year 2011 will be Upper Elevation Balancing but also projects a shift in operations where Equalization will govern the operation beginning in April 2011. The most probable run of the August 24-Month Study projects the water year 2011 release volume to be 11.58 maf. At this point in time, there is a high level of uncertainty regarding the hydrologic conditions that will be experience in 2011. The August 24-Month Study, which includes analysis of a range of possible inflow scenarios in water year 2011, projects that the most probable range of annual releases from Lake Powell will be from 9.0 maf to 14.1 maf. It is currently forecasted that there is approximately a 62% probability that Equalization will occur in water year 2011. This forecast will be updated each month as conditions change.
The unregulated inflow forecast (dated September 1, 2010) for Lake Powell projects the most probable unregulated inflow volumes for the next 3 months as follows: (Sepember-400 kaf [84% of average], October-475 kaf [87% of average], November-460 kaf [84% of average]). The water year outlook for water year 2011 (dated August 3, 2010) projects that the most probable unregulated inflow to Lake Powell during water year 2011 will be 10.75 maf [89% of average]. The probable range [80% probability of occurrence] for the unregulated inflow during water year 2011 is projected to be from 5.0 maf (dry) to 17.1 maf (wet). The water year outlook for 2011 will be updated during the first week of October, 2010.
The September 2010 24-Month Study will be published by September 8th, 2010 and will made available here:
http://www.usbr.gov/uc/water/crsp/studies/24Month_09.pdf
Updated elevation projections for Lake Powell through water year 2010 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 2009, the overall precipitation accumulated through September 30, 2009 was approximately 95% of average based on the 30 year average for the period from 1971 through 2000. For water year 2010 dry conditions have persisted. Estimated percentages of average precipitation for the months thus far in water year 2010 are as follows: October 85%, November 40%, December 130%, January 100% and February 100%, March 90%, April 120%, May 75%, June 100%, July 95%. The overall estimated precipitation percentage of average thus far in water year 2010 for the Upper Colorado River Basin is 96% of average.
The Climate Prediction Center outlook (dated August 19, 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 below 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 August 10, 2010 the storage in Lake Powell was 15.36 million acre-feet (63.1 % of capacity) which is still below desired levels while the overall reservoir storage in the Colorado River Basin as of August 10, 2010 is 33.73 million acre-feet (56.7 % of capacity).
RRFW thanks Rick Clayton of the USBOR for his assistance in providing information for this notification.
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RRFW Riverwire – Glen Canyon Dam Update July 23, 2010
Glen Canyon Dam Lake Powell
The unregulated inflow volume into Lake Powell for July 2010 through July 21st is 550 thousand acre feet (kaf) and at the current inflow rate, the inflow volume for July 2010 will likely be approximately 674 kaf (43% of average). Observed inflows peaked for water year 2010 on June 12, 2010 at 57,600 cubic feet per second (cfs). Since that time inflows have steadily declined and as of July 21, 2010 inflows had decreased to 6,250 cfs. The low water surface elevation for water year 2010 occurred on April 15, 2010 when the elevation dipped to 3618.64 feet above sea level. Since that date the elevation has been on the rise and reached a peak of 3638.82 on June 30, 2010. This will likely be the peak elevation for water year 2010 as inflows are projected to fall below release rates during the next week. The overall elevation increase for water year 2010 was just over 20 feet. By the end of water year 2010 the elevation is projected to be roughly 3634.7 feet above sea level. The April through July forecasted unregulated inflow to Lake Powell is currently 5.77 maf (73% of average) based on the July midmonth forecast.
Releases from Glen Canyon Dam during the month of July will fluctuate each day for power generation between a peak hourly average release of about 16,500 cfs, during the morning and afternoon and a daily low hourly average release of 8,500 cfs during the late evening and early morning hours. The release volume scheduled for July is 800,000 acre-feet. The release volume for August will be approximately 800,000 acre-feet.
Bureau of Reclamation officials are projecting August flows to be the same as July flows at this time, between a peak hourly average release of about 16,500 cfs, during the morning and afternoon and a daily low hourly average release of 8,500 cfs during the late evening and early morning hours.
In addition to the daily fluctuation pattern, instantaneous releases from Glen Canyon Dam also fluctuate to provide approximately 40 megawatts (approximately 1,100 cfs) of system regulation to maintain stable conditions within the electrical generation and transmission system. This translates into momentary release fluctuations of about +/- 1100 cfs above or below the hourly average release rate. These momentary fluctuations for regulation are very short lived and typically balance out over the hour. When an unanticipated outage event occurs in the generation system, reserve generation at Glen Canyon Dam can also be called upon up to a limit of 83 megawatts (approximately 2,250 cfs of release) 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 limit of 83 megawatts.
On September 1, 2010 and continuing through October 31, 2010, the releases from Glen Canyon Dam will be steady with no fluctuations for power production (excluding system regulation and spinning reserves) for a steady flow experiment pursuant to the February 2008 Finding of No Significant Impact ‘Experimental Releases from Glen Canyon Dam, Arizona 2008 through 2012’. This year will be the third year of steady flows of the 5 year experiment. The projected release rate being targeted is 8,000 cfs which is equivalent to a monthly release volume of approximately 476,000 acre-feet in September 2010 and 492,000 acre-feet in October 2010. At the end of August, for a period of approximately 3 days, the daily fluctuation schedule will change each day in order to gradually transition to the steady release rate of 8,000 cfs to begin on September 1, 2010.
Pursuant to the Colorado River Interim Guidelines for Lower Basin Shortages and Coordinated Operations for Lakes Powell and Mead (Interim Guidelines) the operational tier for water year 2010 is Upper Elevation Balancing and the projected water year release volume is 8.23 million acre feet (maf). Under this operational tier there was a possibility that Equalization could occur in 2010 if the April 2010 24-Month Study,with 8.23 maf projected for release during water year 2010, indicated a Lake Powell projected elevation on September 30 , 2010 greater than 3642 feet above sea level (the Equalization level for water year 2010). This condition was not projected in the April 24-Month Study and for this reason, the release volume for water year 2010 will be 8.23 maf. Monthly release volumes for the remainder of the water year will be scheduled to achieve this water year release volume.
The July 2010 24-Month Study projects that operation tier for Glen Canyon Dam in water year 2011 will be Upper Elevation Balancing but also projects a shift to Equalization in April 2011. The projected water year 2011 release volume is 11.5 maf. It should be cautioned however that at this time of year, the inflow assumptions used in the 24-Month Study for the following water year are based on statistical averages and do not reflect current hydrologic conditions. There is a high level of uncertainty about what the inflow conditions will be in water year 2011. In August 2010 the Colorado Basin River Forecast Center will issue an inflow projection for water year 2011 and this will be the basis of the inflow assumptions used in the August 2010 24-Month Study. It is currently forecasted that there is approximately a 59% probability that Equalization will occur in water year 2011. This forecast will be updated each month as conditions change.
The July 2010 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 2010 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 2009, the overall precipitation accumulated through September 30, 2009 was approximately 95% of average based on the 30 year average for the period from 1971 through 2000. For water year 2010 dry conditions have persisted. Estimated percentages of average precipitation for the months thus far in water year 2010 are as follows: October 85%, November 40%, December 130%, January 100% and February 100%, March 90%, April 120%, May 75%, June 100%, . The overall estimated precipitation percentage of average thus far in water year 2010 for the Upper Colorado River Basin is 87% of average.
The Climate Prediction Center outlook (dated July 15, 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 below 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 July 21, 2010 the storage in Lake Powell was 15.73 million acre-feet (64.7 % of capacity) which is still below desired levels while the overall reservoir storage in the Colorado River Basin as of June 30, 2010 is 34.37 million acre-feet (57.8 % of capacity).
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RRFW Riverwire – Glen Canyon Dam Update June 25, 2010
Glen Canyon Dam / Lake Powell
The unregulated inflow volume into Lake Powell so far for June (as of June 23rd) is 2.42 million acre feet (maf). Observed inflows peaked on June 12, 2010 at 57,600 cubic feet per second (cfs) and have declined since that time to 26,300 cfs on June 23, 2010. At the current rate of decline is it estimated that the unregulated inflow to Lake Powell for the month of June will be approximately 2.7 maf (88% of average). This will be well above the projected unregulated inflow from the June 24-month study which was 2.05 maf (66% of average). The Colorado Basin River Forecast Center did increase the June forecast to 2.45 maf (79% of average) on June 15th and this volume will now likely be exceeded on June 24th.
As a result of the additional volume of inflow that is being observed this month, the elevation of Lake Powell is much higher than what was projected in the June 24-Month Study. It is now likely that the peak elevation this summer will be in the range from 3638 to 3640 feet above sea level rather than the previously projected peak of 3634 to 3635 feet above sea level. The April through July forecasted unregulated inflow to Lake Powell is currently 5.45 maf (69% of average) based on the June mid month forecast. This forecast will be updated during the first week of July.
Releases from Glen Canyon Dam during the month of June will fluctuate each day for power generation between a peak hourly average release of about 12,500 cfs, during the morning and afternoon and a daily low hourly average release of 6,500 cfs during the late evening and early morning hours. The release volume scheduled for June is 600,000 acre-feet. The release volume scheduled for July is 800,000 acre-feet and daily fluctuations will range between 16,500 cfs during the afternoon and evening hours and 8.500 cfs during the late night and early morning hours. The release volume for August is projected to be 800,000 acre-feet and this will be confirmed in late July.
In addition to the daily fluctuation pattern, instantaneous releases from Glen Canyon Dam also fluctuate to provide approximately 40 megawatts (approximately 1,100 cfs) of system regulation to maintain stable conditions within the electrical generation and transmission system. This translates into momentary release fluctuations of about +/- 1100 cfs above or below the hourly average release rate. These momentary fluctuations for regulation are very short lived and typically balance out over the hour. When an unanticipated outage event occurs in the generation system, reserve generation at Glen Canyon Dam can also be called upon up to a limit of 83 megawatts (approximately 2,250 cfs of release) 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 limit of 83 megawatts.
On September 1, 2010 and continuing through October 31, 2010, the releases from Glen Canyon Dam will be steady with no fluctuations for power production (excluding system regulation and spinning reserves) for a steady flow experiment pursuant to the February 2008 Finding of No Significant Impact Experimental Releases from Glen Canyon Dam, Arizona 2008 through 2012. This year will be the third year of steady flows of the 5 year experiment. The projected release rate being targeted is 8,000 cfs which is equivalent to a monthly release volume of approximately 476,000 acre-feet in September 2010 and 491,000 acre-feet in October 2010. At the end of August, for a period of approximately 3 days, the daily fluctuation schedule will change each day in order to gradually transition to the steady release rate of 8,000 cfs to begin on September 1, 2010.
Pursuant to the Colorado River Interim Guidelines for Lower Basin Shortages and Coordinated Operations for Lakes Powell and Mead (Interim Guidelines) the operational tier for water year 2010 is Upper Elevation Balancing and the projected water year release volume is 8.23 maf. Under this operational tier there was a possibility that Equalization could occur in 2010 if the April 2010 24-Month Study ,with 8.23 maf release during water year 2010, projected that the elevation of Lake Powell on September 30 , 2010 was to be greater than 2010 equalization level (3642 feet above sea level). This condition, however, was not projected in the April 2010 24-Month Study. Therefore, the release volume for water year 2010 will be 8.23 maf. Projected monthly release volumes for the remainder of the water year will be scheduled to meet this annual release volume.
The June 2010 24-Month Study projects that operation tier for Glen Canyon Dam in water year 2011 will be Upper Elevation Balancing. The June 2010 24-Month Study also projects a shift to Equalization in April 2011 with a projected annual release volume of 11.15 maf. It should be cautioned however that at this time of year, the inflow scenario assumed in the 24-Month Study for the following water year is based on the statistical average and does not reflect a current projection from the Colorado Basin River Forecast Center (CBRFC). There is a high level of uncertainty about what the inflow conditions will be like in water year 2011. In August 2010 the CBRFC will issue an inflow projection for water year 2011 and the August 2010 24-Month Study will be based on this inflow projection rather than statistical average. It is currently forecasted that there is approximately a 62% probability that Equalization will occur in water year 2011. This forecast will be updated each month as conditions change.
The July 2010 24-Month Study will be published by July 12, 2010 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 2010 based on the most recently published 24-Month Study are maintained at: Lake Powell Projected Elevations: http://www.usbr.gov/uc/water/crsp/studies/lppwse.html
Upper Colorado River Basin Hydrology
In the Upper Colorado River Basin during water year 2009, the overall precipitation accumulated through September 30, 2009 was approximately 95% of average based on the 30 year average for the period from 1971 through 2000. For water year 2010 dry conditions have persisted. Estimated percentages of average precipitation for the months thus far in water year 2010 are as follows: October 85%, November 40%, December 130%, January 100% and February 100%, March 90%, April 120%, May 80%. The overall estimated precipitation percentage of average thus far in water year 2010 for the Upper Colorado River Basin is 87% of average.
The Climate Prediction Center outlook (dated May 20, 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.
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 June 23, 2010 the storage in Lake Powell was 15.8 million acre-feet (64.8 % of capacity) which is still below desired levels while the overall reservoir storage in the Colorado River Basin as of June 23, 2010 is 34.65 million acre-feet (58.3 % of capacity).
RRFW thanks Rick Clayton of the USBOR for his assistance in providing information for this notification.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 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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Check out new items and donate at the RRFW Store! RRFW is a non-profit project of Living Rivers. ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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RRFW Riverwire – Glen Canyon Dam Update February 7, 2010
Glen Canyon Dam and Lake Powell
The unregulated inflow volume into Lake Powell in January 2010 was just below what was forecasted at the beginning of January. The unregulated inflow to Lake Powell for the month of January was 304,000 acre-feet (75% of average). This was about 26,000 acre-feet below the unregulated inflow volume that was projected in the January 2010 24-Month Study. For this reason, the elevation of Lake Powell at the end of January was about 2 inches below what was projected in the January 2010 24-Month Study. The end of January Lake Powell elevation was 3622.12 feet above sea level which was over 4 feet lower than the elevation on January 1, 2010.
The release volume for January 2010 was 900,480 acre-feet. Daily peak releases for power generation in January were 17,500 cfs during the morning and afternoon with lows of approximately 9,500 cfs in the very early morning hours. In February 2010 the scheduled release volume for the month is 640,000 acre-feet. Peak releases each day for power generation in February will be approximately 14,000 cfs with lows of about 8,000 cfs.
In addition to the daily fluctuation pattern, instantaneous releases from Glen Canyon Dam also fluctuate to provide approximately 40 megawatts of system regulation to maintain stable conditions within the electrical generation and transmission system. These momentary fluctuations for regulation are very short lived and typically balance out over the hour. Glen Canyon Dam also provides a level of reserve generation that can be called upon when unanticipated outages occur within the generation system. When an outage event occurs, reserve generation at Glen Canyon Dam can be called upon and this additional reserve generation is typically maintained for 2 hours or less.
The official Water Supply Forecast (April-July Unregulated Inflow Volume) for Lake Powell issued by the Colorado Basin River Forecast Center will be updated during the first week of February. The January official forecast for Lake Powell unregulated inflow was 6.2 million acre-feet (maf) which is 78% of average for the period from 1971 to 2000. The preliminary Water Supply Forecast updated for February has been released and is 6.0 maf (76% of average). The official Water Supply Forecast is expected to be released later this week.
Based on the January forecast, the January 2010 24-Month Study projected that the water year release volume from Lake Powell was likely to be 8.23 maf pursuant to the Interim Guidelines. However, the operating tier for Glen Canyon Dam in water year 2010 is Upper Elevation Balancing and under this tier there is a possibility for an April adjustment. It is possible, if hydrologic conditions become wetter than current levels, that an April adjustment to Equalization could occur and under Equalization the projected water year release from Glen Canyon Dam could be greater than 10.5 maf.
As of early January, given the hydrologic conditions within the Colorado River Basin and the range of possible inflow scenarios that could occur in 2010, Reclamation estimates that there is was about a 21% probability that an April adjustment to the Equalization Tier will occur. This estimate is based on many factors that are changing through time. Reclamation will update this estimated probability each month to provide stakeholders some probablistic estimate of the possibility that Equalization will occur in water year 2010.
The January 2010 24-Month Study has been published and is available here: http://www.usbr.gov/uc/water/crsp/studies/24Month_01.pdf
Updated elevation projections for Lake Powell through water year 2010 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 2009, the overall precipitation accumulated through September 30, 2009 was approximately 95% of average based on the 30 year average for the period from 1971 through 2000. For water year 2010 the dry conditions have continued. Precipitation for October 2009 was 85% of average and for November, precipitation was estimated to be only 40% of average. In December 2009, the estimated precipitation above Lake Powell was 115% of average.
The Climate Prediction Center outlook (dated January 21, 2010) for temperature over the next 3 months indicates that temperatures in the northern reaches of the Upper Colorado River Basin have an increased probability of being above average. Accumulated precipitation over the next 3 months are projected to be near average in the Upper Colorado River Basin (above Lake Powell) while are projected to be above average in the Lower Colorado River Basin (below Lake Powell).
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 31, 2010 the storage in Lake Powell was 13.99 million acre-feet (57.52 percent of capacity) which is still below desired levels while the overall reservoir storage in the Colorado River Basin as of January 31, 2010 is 33.01 million acre-feet (55.64 percent of capacity).
RRFW thanks Rick Clayton of the USBOR for his assistance in providing information for this notification.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 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 October 14, 2009
Lake Powell
The unregulated inflow volume into Lake Powell during September 2009 was 0.265 million acre-feet (maf) which was 56% of average based on the period from 1971-2000. This was below the unregulated inflow volume that was forecasted at the beginning of September, which was 0.400 maf.
As a result, the elevation of Lake Powell at the end of September was about 1.3 feet lower than projected in the September 24-Month Study.
For water year 2009, the annual volume released from Lake Powell was 8.235 maf and the end of water year elevation of Lake Powell was 3635.37 feet above sea level (64.63 feet from full pool). The end of water year elevation for 2009 was 8.5 feet above the end of water year elevation recorded for 2008. The 2009 end of water year storage content was 15.36 maf which was 63.2% of full capacity (24.322 maf). The unregulated inflow to Lake Powell during water year 2009 was 10.63 maf which is 88% of the average based on the historic period from 1971-2000.
During September and October, releases from Glen Canyon Dam have been and will continue to be steady at a targeted release rate of 10,000 cubic feet per second (cfs) pursuant to the ‘February 2008 Finding of No Significant Impact Experimental Releases from Glen Canyon Dam, Arizona 2008 through 2012’ and consistent with the ‘Final Environmental Assessment – Experimental Releases from Glen Canyon Dam, Arizona, 2008 through 2012’. Fluctuations for power system regulation and spinning reserves will occur if necessary during this steady release period. The release volume for October will likely be near 0.615 maf as a continuation of the steady release period
As of October 1, 2009, the unregulated inflow to Lake Powell for water year 2010 is projected to have an 80% probability of being within the range between 4.7 maf and 16.5 maf. There is an estimated 10% probability that the water year 2010 unregulated inflow volume will be below 4.7 maf and there is also an estimated 10% probability that the water year 2010 unregulated inflow volume will be greater than 16.5 maf.
Based on the range of probable inflow volumes and through implementation of the Interim Guidelines, there is approximately a 55% probability that Equalization will occur in 2010. The determination of whether or not Equalization will occur in 2010 will be based on the projected September 30 Lake Powell water surface elevations of the 2010 April 24-Month Study. If Equalization does occur in 2010, the water year release volume would be approximately 10.5 maf. If however, Equalization does not occur in 2010 (45% probability), the water year release volume could be 8.23 maf or possibly 9.0 maf depending on the projected September 30 Lake Mead water surface elevation in the April 24-Month Study. Each month these forecasted probabilities will be updated as hydrologic conditions change in the Upper Colorado River Basin.
Upper Colorado River Basin Hydrology
In the Upper Colorado River Basin during water year 2009, the overall precipitation accumulated through September 30, 2009 is approximately 95% of average based on the 30 year average for the period from 1971 through 2000. The final 3 months of water year 2009 all had accumulated precipitation rates that were all below average with 60, 45 and 80% of average occurring in July, August and September respectively.
The Climate Prediction Center outlook (dated September 17, 2009) for temperature over the next 3 months indicates that temperatures in the southwest have an increased probability of being above average while accumulated precipitation is projected to be near average in the Upper Colorado River 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 September 30, 2009 the storage in Lake Powell was 15.46 million acre-feet (63.6 percent of capacity) which is still below desired levels while the overall reservoir storage in the Colorado River Basin as of September 1, 2009 is 34.2 million acre-feet (57.5 percent of capacity).
RRFW thanks Rick Clayton of the USBOR for his assistance in providing information for this notification.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 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. ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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RRFW Riverwire – Glen Canyon Dam Update September 11, 2009
Glen Canyon Dam and Lake Powell
The unregulated inflow volume into Lake Powell during August 2009 was 0.323 million acre-feet (maf) which was 52% of average based on the period from 1971-2000. This was well below the unregulated inflow volume that was forecasted at the beginning of August (0.550 maf). As a result, the elevation of Lake Powell at the end of August was about 2.5 feet lower than projected in the August 24ÂÂMonth Study. The release volume during August from Glen Canyon Dam was 0.802 maf and the elevation of Lake Powell on August 31, 2009 was 3637.40 feet above sea level. The current forecast of the most probable (median) unregulated inflow volume for September through November is 1.350 maf which is 86% of average.
During September thus far through September 10, the unregulated inflow volume to Lake Powell was only 70,500 acre-feet. At this rate, the monthly volume of unregulated inflow would be approximately 211,000 acre-feet which would be well below the forecasted level of 400,000 acre-feet. It is likely that the elevation of Lake Powell at the end of September will be on the order of 1 foot lower than the elevation projected for the end of September in the September 24-month study which was 3636.7 feet above sea level.
During August 2009, releases from Glen Canyon Dam followed a daily fluctuation pattern for power generation that included an afternoon peak to approximately 16,500 cfs with an early morning low release rate of approximately 8,500 cfs. During the last 3 days of August, the fluctuation pattern was tapered by reducing the afternoon peak each day and increasing the early morning low release rate to 10,000 cfs. These modifications were made to provide a transition from the fluctuating release regime to a steady release regime which began on September 1, 2009.
During September and October, releases from Glen Canyon Dam will be held steady at a targeted release rate of 10,000 cfs pursuant to the February 2008 Finding of No Significant Impact Experimental Releases from Glen Canyon Dam, Arizona 2008 through 2012 and consistent with the Final Environmental Assessment Experimental Releases from Glen Canyon Dam, Arizona, 2008 through 2012. Fluctuations for power system regulation and spinning reserves will occur if necessary during this steady release period. The release volume for September will be approximately 0.595 maf which will achieve a water year release volume of 8.23 maf for water year 2009 pursuant to the Colorado River Interim Guidelines for Lower Basin Shortages and Coordinated Operations for Lakes Powell and Mead (Interim Guidelines). The release volume for October will likely be near 0.615 maf as a continuation of the steady release period
In water year 2010, the unregulated inflow to Lake Powell is projected to have an 80% probability of being within the range between 5 maf and 18 maf. There is an estimated 10% probability that the 2010 unregulated inflow volume will be below 5 maf and there is also an estimated 10% probability that the 2010 unregulated inflow volume will be greater than 18 maf.
Based on the range of probable inflow volumes and through implementation of the Interim Guidelines, there is approximately a 65% probability that Equalization will occur in 2010. The determination of whether or not Equalization will occur in 2010 will be based on the results of the 2010 April 24 Month Study. If Equalization does occur in 2010, the water year release volume would be approximately 10.4 maf or greater. If however, Equalization does not occur in 2010 (35% probability), the water year release volume would be 8.23 maf. Each month these forecasted probabilities will be updated as hydrologic conditions change in the Upper Colorado River Basin.
Upper Colorado River Basin Hydrology
In the Upper Colorado River Basin during water year 2009, the overall precipitation accumulated through September 1, 2009 is approximately 100% of average based on the 30 year average for the period from 1971 through 2000. Early in the water year (October and November 2008) accumulated precipitation was well below average but rebounded in December with the monthly accumulated precipitation estimated to be approximately 185% of average within the Upper Colorado River Basin. Below average precipitation returned during the winter months (January, February and March) followed by above average precipitation during the spring months (April, May and June). Of note, in June the accumulated precipitation was estimated to be 215% of average. Below average accumulated precipitation returned in July and August and projected to persist through the end of water year 2009.
The Climate Prediction Center outlook (dated August 20, 2009) for temperature over the next 3 months indicates that temperatures in the southwest have an increased probability of being above average while accumulated precipitation is projected to be near average in the Upper Colorado River 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 September 1, 2009 the storage in Lake Powell was 15.7 million acre-feet (65 percent of capacity) which is still below desired levels while the overall reservoir storage in the Colorado River Basin as of September 1, 2009 is 34.8 million acre-feet (58.5 percent of capacity).
RRFW thanks Rick Clayton of the USBOR for his assistance in providing information for this notification.
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RRFW Riverwire – Glen Canyon Dam Update November 21, 2008
Glen Canyon Dam Operations
The monthly release volume for November 2008 is scheduled to be 600,000 acre-feet. During the months of September and October, releases from Glen Canyon Dam were steady at approximately 12,080 cubic feet per second (cfs) as described in the Final Environmental Assessment for Experimental Releases from Glen Canyon Dam, Arizona, 2008 through 2012 (EA).
Beginning on Saturday November 1, 2008 operation of Glen Canyon Dam will begin daily fluctuations for power generation as described in the Operating Criteria for Glen Canyon Dam and the 1996 Record of Decision (ROD) on the Operation of Glen Canyon Dam. Daily average releases during November will be about 10,000 cfs. Monday through Friday releases will peak each afternoon to about 13,000 cfs with early morning releases of approximately 7,000 cfs. Weekend peak flows will be about 12,750 cfs with morning low releases near 7,000 cfs.
The water year release volume from Glen Canyon Dam during water year 2008 was 8.978 million acre feet (maf) with an equalization volume of 748,000 acre-feet. This volume was based on actual and forecasted inflow and reservoir operation conditions for Lake Powell and Lake Mead under the Equalization Tier of the Interim Guidelines. The 2008 water year ending elevation and storage for Lake Powell was 3626.90 feet above sea level and 14.51 maf respectively. This was a 2.58 maf increase in storage year over year. Lake Powell begins water year 2009 at 59.6% of full capacity.
Under the Interim Guidelines, the water year 2009 operational tier is Upper Elevation Balancing. Under the Upper Elevation Balancing Tier, the projected release volume from Glen Canyon Dam for water year 2009 is 8.23 maf. As described in section 6.B.3 of the Interim Guidelines, if the April 2009 24-month study projects Lake Powell’s end of water year 2009 reservoir elevation to be above 3639 feet above see level, the Equalization Tier would govern for the remainder of water year 2009. Under the Equalization Tier, it is possible for the water year release volume to be greater than 8.23 maf.
Actual and forecasted inflows to Lake Powell have been declining over the past several months. The volume of unregulated inflow to Lake Powell in October was 372,290 acre-feet (67% of average). The forecasted unregulated inflow for months of November, December and January is 1.05 million acre-feet (79% of average).
Upper Colorado River Basin Hydrology
Precipitation in the basin above Lake Powell was below average during the summer months and has continued through September. Precipitation during June, July and August 2008 was 70%, 65% and 90% of average respectively with precipitation in September measured at 70% of average. The overall precipitation in the Upper Colorado River Basin for water year 2008 was near average (about 101%). Precipitation in October 2008 was 65% of average. The unregulated inflow to Lake Powell during the April through July 2008 was 8.906 maf (112% of average). The long range outlook for unregulated inflow to Lake Powell for water year 2009 is projected to be 10.58 maf (88% of the 1971-2000 average).
The Upper Colorado River Basin is experiencing a protracted multi-year drought. Since 1999, inflow to Lake Powell has been below average in every year except water year 2005 and 2008. In the summer of 1999, Lake Powell was essentially full with reservoir storage at 23.5 million acre-feet, or 97 percent of capacity. Inflow to Lake Powell in 1999 was 109 percent of average. The manifestation of drought conditions in the Upper Colorado River Basin began in the fall months of 1999. A five year period of extreme drought occurred in water years 2000, 2001, 2002, 2003, and 2004 with unregulated inflow to Lake Powell only 62, 59, 25, 51, and 49 percent of average, respectively. Lake Powell storage decreased through this five-year period, with reservoir storage reaching a low of 8.0 million acre-feet (33 percent of capacity) on April 8, 2005.
Drought conditions eased in water year 2005 in the Upper Colorado River Basin. Precipitation was above average in 2005 and unregulated inflow to Lake Powell was 105 percent of average. Lake Powell increased by 2.77 million acre-feet (31 feet in elevation) during water year 2005. But as is often the case, one favorable year does not necessarily end a protracted drought. In 2006, there was a return to drier conditions in the Colorado River Basin. Unregulated inflow to Lake Powell in water year 2006 was only 71 percent of average.
Water year 2007 was another year of below average inflow with unregulated inflow into Lake Powell at 68 percent of average. Over the past 9 years (2000 through 2008, inclusive), inflow to Lake Powell has been below average in all but two years (2005 and 2008). Drought conditions have eased in water year 2008 with above average inflows to the main stem Colorado River reservoirs (with the exception of Flaming Gorge and Fontenelle Reservoirs). Reservoir storage in the Colorado River Basin, however, is still below desired levels with the overall Colorado River system storage at the beginning of water year 2009 of 34.0 maf which is 59.3% of capacity.
This release courtesy Rick Clayton, Hydraulic Engineer, Upper Colorado Region US Bureau of Reclamation.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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RRFW Riverwire – Glen Canyon Dam Update August 27, 2008
Glen Canyon Dam Operations
The monthly release volume for September 2008 is scheduled to be 719,000 acre-feet. During the months of September and October, releases from Glen Canyon Dam will be steady as described in the Final Environmental Assessment for Experimental Releases from Glen Canyon Dam, Arizona, 2008 through 2012 (EA). Beginning on September 1, 2008, releases from Glen Canyon Dam will be steady at 12,083 cfs and will remain at this level through the end of the day on October 31, 2008. The monthly volume for October 2008 that corresponds to this steady release rate is 743,000 acre-feet.
The water year release volume from Glen Canyon Dam in water year 2008 is being determined under the Equalization Tier of the Interim Guidelines. Under the Equalization Tier, the water year release volume in 2008 is being adjusted each month in order to target an end of water year elevation at Lake Mead of 1105 feet above sea level. Based on system conditions as of August 26, 2008 and projected operations at Lake Mead for the remainder of water year 2008, the release volume from Glen Canyon Dam for September 2008 will be set to 719 kaf which corresponds to the steady release rate of 12,083 cfs. This adjustment is being made now in order to implement the steady flows which are to begin on September 1, 2008.
Upper Colorado River Basin Hydrology
Precipitation in the basin above Lake Powell was above average in July (150% of average). The overall precipitation in the Upper Colorado River Basin for water year 2008 so far has been 105% of average. The unregulated inflow to Lake Powell during the April through July period was 8.84 maf (111% of average). Unregulated inflow to Lake Powell from now to the end of October is projected to be above average (106%). The long range outlook for water year 2009 projects that the most probable unregulated inflow to Lake Powell will be 91% of the 30-year average (1971-2000) however there is a wide range of uncertainty associated with these long range outlooks.
Upper Colorado River Basin Drought
The Upper Colorado River Basin is experiencing a protracted multi-year drought. Since 1999, inflow to Lake Powell has been below average in every year except water year 2005 and 2008.
In the summer of 1999, Lake Powell was essentially full with reservoir storage at 23.5 million acre-feet, or 97 percent of capacity. Inflow to Lake Powell in 1999 was 109 percent of average. The manifestation of drought conditions in the Upper Colorado River Basin began in the fall months of 1999. A five year period of extreme drought occurred in water years 2000, 2001, 2002, 2003, and 2004 with unregulated inflow to Lake Powell only 62, 59, 25, 51, and 49 percent of average, respectively. Lake Powell storage decreased through this five-year period, with reservoir storage reaching a low of 8.0 million acre-feet (33 percent of capacity) on April 8, 2005.
Drought conditions eased in water year 2005 in the Upper Colorado River Basin. Precipitation was above average in 2005 and unregulated inflow to Lake Powell was 105 percent of average. Lake Powell increased by 2.77 million acre-feet (31 feet in elevation) during water year 2005. But as is often the case, one favorable year does not necessarily end a protracted drought. In 2006, there was a return to drier conditions in the Colorado River Basin. Unregulated inflow to Lake Powell in water year 2006 was only 71 percent of average.
Water year 2007 was another year of below average inflow with unregulated inflow into Lake Powell at 68 percent of average. Over the past 9 years (2000 through 2008, inclusive), inflow to Lake Powell has been below average in all but two years (2005 and 2008). Drought conditions have eased in water year 2008 with above average inflows to the main stem Colorado River reservoirs with the exception of Flaming Gorge and Fontenelle Reservoirs. Reservoir storage in the Colorado River Basin, however, is still below desired levels with the overall Colorado River system storage (above Lake Mead) projected to be about 58% of capacity at the end of water year 2008.
Reservoir storage in Lake Powell and Lake Mead has decreased during the past 8 years but is projected to increase by the end of water year 2008. Current reservoir storage in Lake Powell is 61 percent of capacity. Storage in Lake Mead is 46 percent of capacity.
This release courtesy Rick Clayton, Hydraulic Engineer, Upper Colorado Region 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.
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Lake Powell – Glen Canyon Dam – Current Status – Feb. 5th, 2008 Glen Canyon Dam Operations Releases from Glen Canyon Dam in February 2008 will average 10,400 cubic feet per second (cfs) with a total of 600,000 acre-feet scheduled to be released for the month. On Mondays through Fridays in February, daily release fluctuations due to load following will likely vary between a low of 8,500 cfs (during late evening and early morning off-peak hours) to a high of 14,500 cfs (during daylight and early evening on-peak hours). On Saturdays and Sundays, release fluctuations will likely vary between a low of 8,500 cfs to a high of 14,000 cfs. In March 2008, a high flow test may be implemented. As a result of information resulting from scientific monitoring and research activities and stakeholder discussions in the Glen Canyon Dam Adaptive Management Program, Reclamation has proposed a 2008 high flow test. The release characteristics of such a test would be identical to the test conducted in November 2004 (with a maximum release of about 41,500 cfs for 60 hours), but under much more highly enriched fine sediment conditions, a unique situation during the last 10 years. The purpose of this test would be to determine the effectiveness of rebuilding and reworking sandbar deposits and backwaters in Marble and Grand Canyons. The Department of the Interior has concurred with (1) Reclamation’s proposal to initiate environmental compliance activities on the proposed test, and (2) the United States Geological Survey’s proposal to continue planning and scheduling scientific monitoring and research activities related to the test. Th e test is proposed to occur in early March; however, a final decision on whether to conduct such a test has not been made. Such a decision is currently expected to be made about mid-February 2008, only after environmental compliance actions are complete. The scheduled release volume for March 2008 in the current 24 month study is 600,000 acre-feet. If the high flow test occurs as proposed, the release volume for March 2008 may be adjusted to accommodate this test. The annual release from Lake Powell for water year 2008 would not change as a result of the high flow test.
Upper Colorado River Basin Hydrology Precipitation in the Upper Colorado River Basin was 160 percent of average in January 2008. This was the second month in a row where basin precipitation was well above normal making up for a very dry November 2007. Basin wide snowpack was only 35 percent of average on November 29, 2007, but has increased steadily during December 2007 and January 2008 to 132% of average on February 4, 2008. The climate outlook over the next 3 months is for near normal precipitation and above normal temperatures. Inflow to Lake Powell is currently 7,400 cfs (February 4, 2008). Total unregulated inflow to Lake Powell so far in water year 2008 (October through January) is 82 percent of average with January measured at 83 percent of average. Forecasted April through July unregulated inflow to Lake Powell in 2008 is 9.5 million acre-feet, 120 percent of average (February final forecast). This inflow projection could shift depending upon climate patterns the remainder of the winter and into the spring. Typically by February 1st, the snow accumulation season is about 60% complete. The current elevation of Lake Powell (February 4, 2008) is 3,590.5 feet, 109.5 feet from full pool elevation of 3,700 feet. Reservoir storage is currently 10.87 million acre-feet, or 45 percent of capacity. The water surface elevation of Lake Powell is now near its seasonal low. In April, anticipated snowmelt runoff will cause the water surface elevation to begin to increase. Under the current inflow forecast, Lake Powell would reach a peak elevation of about 3639 feet in July 2008. The peak elevation for Lake Powell in 2007 was 3,611.7 feet.
Upper Colorado River Basin Drought The Upper Colorado River Basin is experiencing a protracted multi-year drought. Since 1999, inflow to Lake Powell has been below average in every year except one. In the summer of 1999, Lake Powell was essentially full with reservoir storage at 23.5 million acre-feet, or 97 percent of capacity. Inflow to Lake Powell in 1999 was 109 percent of average. The manifestation of drought conditions in the Upper Colorado River Basin began in the fall months of 1999. A five year period of extreme drought occurred in water years 2000, 2001, 2002, 2003, and 2004 with unregulated inflow to Lake Powell only 62, 59, 25, 51, and 49 percent of average, respectively. Lake Powell storage decreased through this five-year period, with reservoir storage reaching a low of 8.0 million acre-feet (33 percent of capacity) on April 8, 2005. Drought conditions eased in water year 2005 in the Upper Colorado River Basin. Precipitation was above average in 2005 and unregulated inflow to Lake Powell was 105 percent of average. Lake Powell increased by 2.77 million acre-feet (31 feet in elevation) during water year 2005. But as is often the case, one favorable year does not necessarily end a protracted drought. In 2006, there was a return to drier conditions in the Colorado River Basin. Unregulated inflow to Lake Powell in water year 2006 was only 71 percent of average. Water year 2007 was another year of below average inflow with unregulated inflow into Lake Powell at 68 percent of average. Over the past 8 years (2000 through 2007, inclusive), inflow to Lake Powell has been below average in all but one year (2005). Reservoir storage in Lake Powell and Lake Mead has decreased during the past 8 years. Reservoir storage in Lake Powell is 45 percent of capacity. Storage in Lake Mead is 50 percent of capacity. Updated: February 5, 2008 This release courtesy of Rick Clayton, Bureau of Reclamation.
RRFW_Riverwire@att.net
RRFW Riverwire – Glen Canyon Dam Update
January 8, 2008
Glen Canyon Dam Operations Releases from Glen Canyon Dam in January 2008 will average 13,000 cubic feet per second (cfs) with a total of 800,000 acre-feet scheduled to be released for the month. On Mondays through Fridays in January, daily release fluctuations due to load following will likely vary between a low of 9,000 cfs (during late evening and early morning off-peak hours) to a high of 17,000 cfs (during daylight and early evening on-peak hours). On Saturdays and Sundays, release fluctuations will likely vary between a low of 9,000 cfs to a high of 16,500 cfs.
Releases in February 2008 are scheduled to be the lower than January 2008. A total of 600,000 acre-feet is scheduled to be released in February 2008 which is a daily average of 10,400 cfs.
In March 2008, a high flow test may be implemented. As a result of information resulting from scientific monitoring and research activities and stakeholder discussions in the Glen Canyon Dam Adaptive Management Program, Reclamation has proposed a 2008 high flow test. The dam release characteristics of such as test would be identical to the test conducted in November 2004 (with a maximum release of about 41,500 cfs for 60 hours), but under much more highly enriched fine sediment conditions, a unique situation during the last 10 years. This purpose of this test would be to determine the effectiveness of rebuilding and reworking sandbar deposits and backwaters in Marble and Grand Canyons. The Department of the Interior has concurred with (1) Reclamation’s proposal to initiate environmental compliance activities on the proposed test, and (2) the United States Geological Survey’s proposal to continue planning and scheduling scientific monitoring and research activities related to the te st. The test is proposed to occur in early March; however, a final decision on whether to conduct such a test has not been made. Such a decision is currently expected to be made about mid-February 2008, only after environmental compliance actions are complete. The annual release from Lake Powell for water year 2008 (currently projected to be 8.23 million acre-feet) would not change as a result of the high flow test.
Upper Colorado River Basin Hydrology Precipitation in the Upper Colorado River Basin was 200 percent of average in December 2007. This made up for November 2007, a month which was almost devoid of storm systems. Basinwide snowpack was only 35 percent of average on November 29, 2007, but increased steadily in the month of December. January 2008, thus far, has continued the “wet” pattern seen in December. Basinwide snowpack above Lake Powell is currently 114 percent of average (January 8, 2008).
Inflow to Lake Powell is currently 8,000 cfs (January 7, 2008). Total unregulated inflow in October, November and December 2007 was 85, 73, and 92 percent of average, respectively.
Forecasted April through July unregulated inflow to Lake Powell in 2008 is 8.0 million acre-feet, 101 percent of average (January final forecast). This inflow projection could shift depending upon climate patterns the remainder of the winter and into the spring. Mid-January marks the half-way point in the snow accumulation season.
The current elevation of Lake Powell (January 8, 2008) is 3,593.6 feet, 106.4 feet from full pool elevation of 3,700 feet. Reservoir storage is currently 11.15 million acre-feet, or 46 percent of capacity. The water surface elevation of Lake Powell is now near its seasonal low. The water surface elevation of Lake Powell will likely decrease by about 4 feet between now and April. In April, anticipated snowmelt runoff will cause the water surface elevation to begin to increase. Under the current inflow forecast, Lake Powell would reach a peak elevation of about 3,628 feet in July 2008. The peak elevation for Lake Powell in 2007 was 3,611.7 feet.
Upper Colorado River Basin Drought The Upper Colorado River Basin is experiencing a protracted multi-year drought. Since 1999, inflow to Lake Powell has been below average in every year except one.
In the summer of 1999, Lake Powell was essentially full with reservoir storage at 23.5 million acre-feet, or 97 percent of capacity. Inflow to Lake Powell in 1999 was 109 percent of average. The manifestation of drought conditions in the Upper Colorado River Basin began in the fall months of 1999. A five year period of extreme drought occurred in water years 2000, 2001, 2002, 2003, and 2004 with unregulated inflow to Lake Powell only 62, 59, 25, 51, and 49 percent of average, respectively. Lake Powell storage decreased through this five-year period, with reservoir storage reaching a low of 8.0 million acre-feet (33 percent of capacity) on April 8, 2005. Drought conditions eased in water year 2005 in the Upper Colorado River Basin. Precipitation was above average in 2005 and unregulated inflow to Lake Powell was 105 percent of average. Lake Powell increased by 2.77 million acre-feet (31 feet in elevation) during water year 2005. But as is often the case, one favorable year does not necessarily end a protracted drought. In 2006, there was a return to drier conditions in the Colorado River Basin. Unregulated inflow to Lake Powell in water year 2006 was only 71 percent of average.
Water year 2007 was another year of below average inflow with unregulated inflow into Lake Powell at 68 percent of average. Over the past 8 years (2000 through 2007, inclusive), inflow to Lake Powell has been below average in all but one year (2005).
Reservoir storage in Lake Powell and Lake Mead has decreased during the past 8 years. Reservoir storage in Lake Powell is 46 percent of capacity. Storage in Lake Mead is 50 percent of capacity. Courtesy of Tom Ryan, Bureau of Reclamation
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RRFW Riverwire – Glen Canyon Dam Update
June 6, 2007
Glen Canyon Dam Operations
Releases from Glen Canyon Dam in June 2007 will average 13,400 cubic feet per second (cfs) with a total of 800,000 acre-feet scheduled to be released for the month. On Mondays through Fridays in June, daily release fluctuations due to load following will likely vary between a low of 9,000 cfs (during late evening and early morning off-peak hours) to a high of 17,000 cfs (during daylight and early evening on-peak hours). On Saturdays, release fluctuations will likely vary between a low of 9,000 cfs to a high of 15,500 cfs. On Sundays, release fluctuations will likely vary between a low of 9,000 cfs to a high of 15,000 cfs.
Releases from Glen Canyon Dam in July and August 2007 will be similar to June. A total of 804,000 acre-feet is scheduled to be released in July and August of 2007, which is an average flow of 13,100 cfs.
Upper Colorado River Basin Hydrology
Projections for April through July runoff to Lake Powell in 2007 remain low. The water supply picture in the Colorado River Basin neither improved nor weakened in May. The May final unregulated inflow forecast for April through July runoff into Lake Powell is 4.0 million acre-feet. This is only 50 percent of average.
May was a month with periods of much above average temperatures with higher than expected inflow. Unregulated inflow to Lake Powell in May 2007 was 1,578,000 acre-feet (69 percent of average). The peak snowmelt-runoff inflow to Lake Powell for 2007 occurred on May 23, 2007 when inflow reached 31,600 cfs. The water surface elevation of Lake Powell increased by 9.3 feet in May 2007.
While inflow was higher than projected in May, the projection for inflow to Lake Powell in June is not so bright. There is very little snowpack remaining in the Upper Colorado River Basin and inflow to Lake Powell in June is projected to be only about 35 percent of average.
Reservoir storage is currently 12.74 million acre-feet, or 52 percent of capacity. The current elevation of Lake Powell (June 6, 2007) is 3,610.1 feet, 89.9 feet from full pool elevation of 3,700 feet. The elevation is now likely near the peak for the year. The elevation of Lake Powell is likely to increase until mid-June and then begin to decline. The projected elevation of Lake Powell on July 1, 2007 is 3,610.4 feet.
Upper Colorado River Basin Drought
The Upper Colorado River Basin is experiencing a protracted multi-year drought. Since 1999, inflow to Lake Powell has been below average in every year except one.
In the summer of 1999, Lake Powell was essentially full with reservoir storage at
23.5 million acre-feet, or 97 percent of capacity. Inflow to Lake Powell in 1999 was 109 percent of average. The manifestation of drought conditions in the Upper Colorado River Basin began in the fall months of 1999. A five year period of extreme drought occurred in water years 2000, 2001, 2002, 2003, and 2004 with unregulated inflow to Lake Powell only 62, 59, 25, 51, and 49 percent of average, respectively. Lake Powell storage decreased through this five-year period, with reservoir storage reaching a low of 8.0 million acre-feet (33 percent of capacity) on April 8, 2005.
Drought conditions eased in water year 2005 in the Upper Colorado River Basin. Precipitation was above average in 2005 and unregulated inflow to Lake Powell was 105 percent of average. Lake Powell increased by 2.77 million acre-feet (31 feet in elevation) during water year 2005. But as is often the case, one favorable year does not necessarily end a protracted drought. In 2006, there was a return to drier conditions in the Colorado River Basin. Unregulated inflow to Lake Powell in water year 2006 was only 73 percent of average.
Water year 2007 will be another year of below average inflow. The current projection for spring runoff into Lake Powell is only 50 percent of average. Projected inflow to Lake Powell for the entire 2007 water year is 68 percent of average. With 2007 projected to be a below average inflow year, one sees that over the past 8 years (2000 through 2007, inclusive) inflow to Lake Powell will have been below average in all but one year (2005).
Reservoir storage in Lake Powell and Lake Mead has decreased over the past 8 years. Reservoir storage in Lake Powell and Lake Mead is currently 52 and 50 percent of capacity, respectively.
This update courtesy Tom Ryan, Bureau of Reclamation
adkramoo
RRFW Riverwire – GLEN CANYON DAM UPDATE Updated December 4, 2006
Glen Canyon Dam Operations
Releases from Glen Canyon Dam in December 2006 will average 13,000 cubic feet per second (cfs) with a total of 800,000 acre-feet scheduled to be released for the month. On Mondays through Fridays in December, daily release fluctuations due to load following will likely vary between a low of 9,000 cfs (during late evening and early morning off-peak hours) to a high of 17,000 cfs (during daylight and early evening on-peak hours). On Saturdays, release fluctuations will likely vary between a low of 9,000 cfs to a high of 16,000 cfs. On Sundays, release fluctuations will likely vary between a low of 9,000 cfs to a high of 15,500 cfs.
Releases in January 2007 will likely be very similar to December 2006. A total of 800,000 acre-feet (an average of 13,000 cfs) are scheduled to be released in January 2007
Upper Colorado River Basin Hydrology
The “Four Corners” region experienced extraordinary amounts of precipitation during October 2006. Precipitation events were particularly intense in the vicinity of Lake Powell. Record-breaking daily flows for the month of October were observed on the San Juan, Dolores, San Rafael, Fremont/Dirty Devil, Escalante, and Paria Rivers in the first half of October. The most exceptional of these high flows were the flood flows on the Fremont/Dirty Devil on October 6 and 7, 2006. The stage (level of the river) of the Dirty Devil (at the “Dirty Devil above Poison Springs Wash near Hanksville, Utah” surface water discharge station) increased by more than 15 feet during the flood event. Initial calculations from hydrologists working for the United States Geological Survey estimate an instantaneous peak flow of about 42,000 cfs on the Dirty Devil on October 6 or October 7, 2006.
Inflow from the Dirty Devil River and other drainages which outlet into Lake Powell resulted in remarkable increases in Lake Powell on October 6, October 7, and October 8, 2006. Daily increases in the water surface elevation of Lake Powell on these three days were 1.33 feet, 0.97 feet, and 0.74 feet, respectively. Lake Powell rarely increases in storage during the month of October. However, in October 2006, Lake Powell increased in storage by 609,000 acre-feet, gaining 6.2 feet in elevation.
While October 2006 was a very wet month in the Upper Colorado River Basin, normal conditions returned in November. Aggregate precipitation above Lake Powell during October 2006 was over 200 percent of average. November 2006 basinwide precipitation was approximately 85 percent of average. Unregulated inflow into Lake Powell in November was 559,000 acre- feet, or 103 percent of average.
The current elevation of Lake Powell (December 4, 2006) is 3,606.5 feet. Reservoir storage is currently 12.38 million acre-feet, 51 percent of capacity.
The water surface elevation of Lake Powell is likely to decrease between now and April 2007 when anticipated snowmelt runoff will cause the water surface level to increase once more. The projected elevation of Lake Powell on January 1, 2007, is approximately 3,604 feet. The current projection for April 1, 2007 is approximately 3,598 feet.
Upper Colorado River Basin Drought
The Upper Colorado River Basin experienced five consecutive years of extreme drought from September 1999 through September 2004. In the summer of 1999, Lake Powell was essentially full with reservoir storage at 97 percent of capacity. Inflow volumes for five consecutive water years were significantly below average. Total unregulated inflow in water years 2000, 2001, 2002, 2003, and 2004 was 62, 59, 25, 51, and 49 percent of average, respectively. Lake Powell storage decreased through this five-year period, with reservoir storage reaching a low of 8.0 million acre-feet (33 percent of capacity) on April 8, 2005.
Hydrologic conditions improved in water year 2005 in the Upper Colorado River Basin. Lake Powell increased by 2.77 million acre-feet (31 feet in elevation) during water year 2005. Unregulated inflow to Lake Powell in water year 2005 was 105 percent of average.
Unfortunately, in 2006, there was a return to drier condition in the Colorado River Basin. Unregulated inflow to Lake Powell in water year 2006 was 73 percent of average. Over the past 7 years (2000 through 2006, inclusive) inflow to Lake Powell has been below average in all but one year (2005).
Water year 2007 (which began on October 1, 2006) is off to a good start. Precipitation in the Colorado River Basin in October 2006 was over 200 percent of average, and Lake Powell increased by 6.2 feet during the month, in large part due to exceptional precipitation events in the regions surrounding the lake. Nevertheless, historical records show that it is common to have periods of above average precipitation and runoff during a protracted multi-year drought. The drought in the Colorado River Basin may not be over.
This release courtesy Tom Ryan, United States Bureau of Reclamation.
canyons_owner
RRFW Riverwire – GLEN CANYON DAM UPDATE June 6, 2006
Glen Canyon Dam Operations
Releases from Glen Canyon Dam in June 2006 will average 13,400 cubic feet per second (cfs) with a total of 800,000 acre-feet scheduled to be released for the month. On Mondays through Fridays in June, daily release fluctuations due to load following will likely vary between a low of 9,000 cfs (during late evening and early morning off-peak hours) to a high of 17,000 cfs (during daylight and early evening on-peak hours). On Saturdays, release fluctuations will likely vary between a low of 9,000 cfs to a high of 15,500 cfs. On Sundays, the range will likely vary from 9,000 cfs to 15,000 cfs.
Releases in July and August will likely be very similar to releases in June. Releases from Glen Canyon Dam are scheduled to be 822,000 acre-feet in July 2006 (an average of 13,300 cfs) and 824,000 acre-feet in August 2006 (an average of 13,400 cfs).
Upper Colorado River Basin Hydrology
Inflow projections to Lake Powell have been reduced in response to warm and dry spring conditions in the Colorado River Basin. April and May 2006 precipitation in the Upper Colorado River Basin was approximately 65 and 35 percent of average, respectively. The June final inflow forecast, issued by the National Weather Service on June 5, 2006, is projecting April through July unregulated inflow to Lake Powell for 2006 to be 5.9 million acre-feet, 74 percent of average. Inflow projections earlier in the year were significantly higher (the April inflow forecast, for instance, projected Lake Powell inflow to be 97 percent of average). It is now almost a certainty that inflow to Lake Powell will be below average in 2006.
Thus far, inflow to Lake Powell in water year 2006 (which began on October 1, 2005) has been about 89 percent of average. Unregulated inflow in April 2006 was 103 percent of average and unregulated inflow in May was 89 percent of average. The snow melt runoff has occurred earlier than normal in 2006. Peak inflow to Lake Powell in 2006 was 41,700 cfs and occurred on May 29, 2006. It is unlikely that inflow will exceed this level the remainder of 2006. There is now only a limited amount of snowpack remaining in the Colorado River Basin. Inflow volumes in June and July are forecasted to be much below average levels (65 percent of average in June and 55 percent of average in July).
The water surface elevation of Lake Powell reached a seasonal low on April 7, 2006, at elevation 3,588.7 (111.3 feet from full pool). The current (June 6, 2006) elevation of Lake Powell is 3,607.1 feet (92.9 feet from full pool). Current storage is 12.4 million acre-feet (51 percent of live capacity).
Lake Powell will increase in elevation until late June or early July. The current projected high elevation of Lake Powell for 2006 is about 3,613 feet (87 feet from full pool). However, the actual high elevation could deviate from this projection due to weather patterns in June and July.
Upper Colorado River Basin Drought
The Upper Colorado River Basin experienced five consecutive years of extreme drought from September 1999 through September 2004. In the summer of 1999, Lake Powell was essentially full with reservoir storage at 97 percent of capacity. Inflow volumes for five consecutive water years were significantly below average. Total unregulated inflow in water years 2000, 2001, 2002, 2003, and 2004 was 62, 59, 25, 51, and 49 percent of average, respectively. Lake Powell storage decreased through this five-year drought, with reservoir storage reaching a low of 8.0 million acre-feet (33 percent of capacity) on April 8, 2005.
Hydrologic conditions improved in water year 2005 in the Upper Colorado River Basin. Lake Powell increased by 2.77 million acre-feet (31 feet in elevation) during water year 2005. Unregulated inflow to Lake Powell in water year 2005 was 105 percent of average.
Inflow to Lake Powell is almost certain to be below average in 2006, however. Over the past 7 years (2000 through 2006, inclusive) inflow to Lake Powell will have been below average in all but one year (2005). While drought conditions eased in 2005, and the inflow in 2006 is not expected to be as extremely low as what occurred in 2000 through 2004, the drought in the Colorado River Basin may not be over. Historical droughts show that it is common to have 1 or 2 above average years during sustained multi-year droughts.
The effects of multiple years of low inflow remain visible at Lake Powell where reservoir storage has been reduced. Lake Powell storage is currently 51 percent of capacity.
This release courtesy Tom Ryan, U.S. Bureau of Reclamation
________________________________________________
canyons_owner
RRFW Riverwire – GLEN CANYON DAM UPDATE
April 4, 2006
Glen Canyon Dam Operations
Releases from Glen Canyon Dam in April 2006 will average 10,000 cubic feet per second (cfs) with a total of 600,000 acre-feet scheduled to be released for the month. On Mondays through Sundays in April, daily release fluctuations due to load following will likely vary between a low of 6,250 cfs (during late evening and early morning off-peak hours) to a high of 12,250 cfs (during daylight and early evening on-peak hours).
The release volume from Glen Canyon Dam is currently scheduled to be 600,000 acre-feet in May 2006. June 2006 releases are currently scheduled to be 800,000 acre-feet.
Upper Colorado River Basin Hydrology
March 2006 featured cooler than average temperatures in the Upper Colorado River Basin. Precipitation was moderately above average for the month. This pattern helped boost snowpack in the Upper Colorado River Basin. As March began, basinwide snowpack above Lake Powell was below average (93 percent of average on March 1, 2006), but increased throughout the month. Precipitation in the Upper Colorado River Basin during March was approximately 130 percent of average. Basinwide snowpack (as of April 4, 2006) is currently 103 percent of average. The distribution of snow in the basin continues to vary by geographical location although this variability was reduced somewhat in March when the southern regions of the basin finally experienced a few significant storm systems. The northern regions continue to fare better than regions in the south. Snowpack in the San Juan River Basin, for instance, is only 65 percent of average, while snowpack in the Duchesne, Yampa and Colorado River headwaters is about 115 to 120 percent of average.
Inflow to Lake Powell in water year 2006 (which began on October 1, 2005) thus far has been about 88 percent of average. Inflow, as a percentage of average, has dropped somewhat the past two months, however. Unregulated inflow in February 2006 was 79 percent of average.
Unregulated inflow in March 2006 was 448,100 acre-feet, only 68 percent of average. The low March inflow was a function of cooler than average temperatures during the month.
The National Weather Service issued the April final inflow forecast on April 4, 2006. Forecasted April through July unregulated inflow to Lake Powell for
2006 is 7.7 million acre-feet, 97 percent of average.
The current (April 4, 2006) elevation of Lake Powell is 3,588.7 feet (111.3 feet from full pool). Current storage is 10.7 million acre- feet (44 percent of live capacity).
The water surface elevation of Lake Powell is now at its seasonal low. The water surface elevation will increase during April, May, and June, and probably in early July as well. The current projected high elevation of Lake Powell in 2006 is about 3,625 feet (75 feet from full pool), occurring in mid-July. The actual high elevation could deviate from this projection however. Weather patterns from now through the end of spring will influence the volume of inflow to Lake Powell during this year’s April through July snowmelt runoff season.
Upper Colorado River Basin Drought
The Upper Colorado River Basin experienced five consecutive years of extreme drought from September 1999 through September 2004. In the summer of 1999, Lake Powell was essentially full with reservoir storage at 97 percent of capacity. Inflow volumes for five consecutive water years were significantly below average. Total unregulated inflow in water years 2000, 2001, 2002, 2003, and 2004 was 62, 59, 25, 51, and 49 percent of average, respectively.
Lake Powell storage decreased through this five-year drought, with reservoir storage reaching a low of 8.0 maf
(33 percent of capacity) on April 8, 2005.
Hydrologic conditions improved in water year 2005 in the Upper Colorado River Basin. Lake Powell increased by 2.77 million acre- feet (31 feet in
elevation) during water year 2005. Unregulated inflow to Lake Powell in water year 2005 was 105 percent of average.
The effects of the drought remain visible at Lake Powell where reservoir storage has been reduced. Lake Powell storage is currently only 44 percent of capacity.
This release courtesy Tom Ryan, U.S. Bureau of Reclamation
canyons_owner
RRFW Riverwire – GLEN CANYON DAM UPDATE
March 3, 2006
Glen Canyon Dam Operations
Releases from Glen Canyon Dam in March will average 9,800 cubic feet per second (cfs) with a total of 600,000 acre-feet scheduled to be released for the month. On Mondays through Sundays in March, daily release fluctuations due to load following will likely vary between a low of 6,000 cfs (during late evening and early morning off-peak hours) to a high of 12,000 cfs (during on-peak hours, which in March occurs in the mid-morning hours and again in the late afternoon and early evening hours).
The release volume from Glen Canyon Dam is currently scheduled to be 600,000 acre-feet in both April and May of 2006.
Upper Colorado River Basin Hydrology
February 2006 was a dry month in the Colorado River Basin. As February
began, basinwide snowpack above Lake Powell was above average. As the
month progressed, however, snowpack dropped below average with a total
decrease of 15 percentage points during the month. Precipitation in
the Upper Colorado River Basin during February was approximately 50 percent of average. Basinwide snowpack (as of March 2, 2006) is currently 93 percent of average. The distribution of snow in the basin varies greatly by geographical location. Snowpack in the San Juan River Basin, for instance, is only 40 percent of average, while snowpack in the Yampa and Colorado River headwaters is about 115 to 120 percent of
average.
Inflow to Lake Powell in water year 2006 (which began on October 1,
2005) has been near average, although it dropped off somewhat in February.
Unregulated inflow from October 2005 through February 2006 was 94 percent of average. However, unregulated inflow in February 2006 was only 79 percent of average.
In response to the minimal amount of precipitation in February, the National Weather Service has reduced the inflow forecast for Lake Powell
this spring. The current forecasted April through July unregulated
inflow to Lake Powell for 2006 is 7.2 million acre-feet, 91 percent of average.
The current elevation of Lake Powell is 3,589.7 feet (110.3 feet from full pool). Current storage is 10.8 million acre-feet (44 percent of live capacity).
The water surface elevation of Lake Powell is now near its seasonal low.
The water surface elevation is likely to remain near elevation 3,590 feet during March 2006 and then begin to increase in April 2006, when anticipated snowmelt runoff will cause inflow to exceed the level of release. The current projected high elevation of Lake Powell in 2006 is about 3,620 feet (80 feet from full pool), occurring in mid-July.
The actual high elevation could deviate significantly from this projection however. Weather patterns from now through the end of spring will influence the volume of inflow to Lake Powell during this year’s April through July snowmelt runoff season.
Upper Colorado River Basin Drought
The Upper Colorado River Basin experienced five consecutive years of extreme drought from September 1999 through September 2004. In the summer of 1999, Lake Powell was essentially full with reservoir storage at 97 percent of capacity. Inflow volumes for five consecutive water years were significantly below average. Total unregulated inflow in water years 2000, 2001, 2002, 2003, and 2004 was 62, 59, 25, 51, and 49 percent of average, respectively. Lake Powell storage decreased through this five-year drought, with reservoir storage reaching a low of 8.0 maf
(33 percent of capacity) in early April of 2005.
Hydrologic conditions improved in water year 2005 in the Upper Colorado River Basin. Lake Powell increased by 2.77 million acre- feet (31 feet in
elevation) during water year 2005. Unregulated inflow to Lake Powell in water year 2005 was 105 percent of average.
The effects of the drought remain visible at Lake Powell where reservoir storage has been reduced. Lake Powell storage is currently only 44 percent of capacity.
This release courtesy Tom Ryan, U.S. Bureau of Reclamation
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canyons_owner
RRFW Riverwire – GLEN CANYON DAM UPDATE
January 4, 2006
Glen Canyon Dam Operations
Releases from Glen Canyon Dam in January will average 13,000 cubic feet per second (cfs) with a total of 800,000 acre-feet scheduled to be released for the month. On weekdays in January, daily release fluctuations due to load following will likely vary between a low of 9,000 cfs (during late evening and early morning off-peak hours) to a high of 17,000 cfs (during on-peak hours, which in winter months occurs in the mid-morning hours and again in the late afternoon and early evening hours). On Saturdays, releases will likely vary between a low of 9,000 cfs to a high of 16,000 cfs. On Sundays, releases will likely vary between a low of 9,000 cfs to a high of 15,500 cfs.
The release in February 2006 from Glen Canyon Dam is currently scheduled to be 800,000 acre-feet (an average release of about 14,400 cfs). Releases are currently scheduled to be reduced to 600,000 acre-feet in March 2006.
Upper Colorado River Basin Hydrology
The Upper Colorado River Basin experienced five consecutive years of extreme drought from September 1999 through September 2004. In the summer of 1999, Lake Powell was essentially full with reservoir storage at 97 percent of capacity. Inflow volumes for five consecutive water years were significantly below average. Total unregulated inflow in water years 2000, 2001, 2002, 2003, and 2004 was 62, 59, 25, 51, and 49 percent of average, respectively.
Hydrologic conditions improved in water year 2005 (October 2004 through September 2005) in the Upper Colorado River Basin. The elevation of Lake Powell increased by 31 feet during water year 2005 and storage in Lake Powell increased by 2.77 million acre-feet. Unregulated inflow to Lake Powell in water year 2005 was 105 percent of average.
On April 8, 2005, prior to the favorable snowmelt runoff of 2005, reservoir storage at Lake Powell reached a low of 3,555 feet (145 feet from full pool). The reservoir has declined to 33 percent of capacity,
and had not been that low since 1969. The current elevation of Lake Powell is 3,597.9 feet (102.1 feet from full pool). Current storage is 11.5 million acre-feet (47 percent of live capacity).
Thus far in water year 2006 (which began on October 1, 2005) inflow to Lake Powell has been close to average. Unregulated inflow in October and November of 2005 was 105 and 95 percent of average, respectively.
Unregulated inflow in December 2005 was 360,000 acre-feet, 82 percent of average.
Basinwide snowpack in the Upper Colorado River Basin is currently 109 percent of average (as of January 4, 2006). Precipitation in the basin since October 1, 2005 has been about 115 percent of average. The distribution of snow in the basin varies greatly by geographical location. Snowpack in the upper San Juan River basin, for instance, is only 35 percent of average, while snowpack in the Yampa and Colorado
River headwaters is about 140 percent of average.
Forecasted April through July unregulated inflow to Lake Powell in 2006 is 8.5 million acre-feet, 107 percent of average.
The water surface elevation of Lake Powell is likely to decrease until late March or early April 2006 when anticipated snowmelt runoff will cause the water surface level to increase once more. The current projection the water surface elevation at Lake Powell on April 1, 2006, is about 3,592 feet.
This release courtesy Tom Ryan, U.S. Bureau of Reclamation
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