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). 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