Glen Canyon-Lake Powell Update

In August 2005, a volume of 872,000 acre-feet is scheduled to be released from Lake Powell, which is an average of 14,200 cubic feet per second (cfs). On Mondays through Fridays in August, daily fluctuations due to load following will likely vary between a low of about 10,000 cfs (during late evening and early morning off-peak hours) to a high of about 18,000 cfs (during late afternoon and early evening on-peak hours). On Saturdays, releases will likely vary between a low of about 10,000 cfs during off-peak hours to a high of about 16,000 cfs during on-peak hours. On Sundays, releases will likely vary between a low of about 10,000 cfs during off-peak hours to a high of about 15,000 cfs during on-peak hours.

Releases in September 2005 will be lower. A volume of 495,000 acre-feet is currently scheduled to be released in September 2005. This is an average flow of 8,300 cfs.

Because of the draw down condition of Lake Powell, releases from Lake Powell in water year 2005 are being scheduled to meet the release objective of 8.23 million acre-feet.

Upper Colorado River Basin Hydrology

The Colorado River Basin experienced 5 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 5 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 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 improved in water year 2005 in the Upper Colorado River Basin. Precipitation in the Upper Basin in water year 2005 has been above average. Rains in the fall of 2004 helped reduce soil moisture deficits caused by the drought. River flows responded to the fall rains with increased flows. November 2004, for instance, was the first month with above average inflow to Lake Powell since September of 1999. Snowpack in the Upper Colorado River Basin ranged from average to moderately above average throughout the winter of 2004-2005.

April through July is the snowmelt runoff period in the Colorado River Basin. Unregulated inflow to Lake Powell during April through July was 8.81 million acre-feet in 2005. This is 111 percent of average. Unregulated inflow to Lake Powell in water year 2005 (October 2004 through September 2005) is projected to be 108 percent of average.

Inflow to Lake Powell reached a peak of 77,000 cfs on May 28, 2005. Peak inflow to Lake Powell had not been this high since 1997. The snowmelt runoff is now over for the year. Inflow to Lake Powell is currently 8,700 cfs.

Lake Powell reached a low elevation on April 8, 2005, at 3,555 feet (145 feet from full pool). Reservoir storage had declined to 33 percent of live capacity. The last time Lake Powell had been this low was in May 1969. The water surface elevation increased through the spring and early summer, reaching a peak elevation of 3,608.4 feet on July 14, 2005. The current elevation of Lake Powell is 3,605.8 feet (94.2 feet from full pool). Current storage is 12.3 million acre-feet (51 percent of live capacity).

The water surface elevation of Lake Powell will likely continue to decrease through the fall and winter until April 2006, when anticipated snowmelt runoff will cause the water surface level to increase once more. The projected elevation of Lake Powell on January 1, 2006 is 3,603 feet.

Courtesy Tom Ryan, Bureau of Reclamation