Glen Canyon Dam Update

Glen Canyon Dam Operations

Releases from Glen Canyon Dam in November will average 8,400 cubic feet per second (cfs) with a total of 500,000 acre-feet scheduled to be released in the month. On Mondays through Fridays in November, daily release fluctuations due to load following will likely vary between a low of 5,250 cfs (during late evening and early morning off-peak hours) to a high of 10,250 cfs (during on-peak hours, which in winter months occur in the mid-morning hours and again in the late afternoon and early evening hours). On Saturdays, releases will vary between a low of 5,250 cfs during off-peak hours to a high of 10,000 cfs during on-peak hours. On Sundays, releases will likely vary between a low of 5,250 cfs and a high of 9,500 cfs. Releases from Glen Canyon Dam will increase in December of 2005. The volume of release in December is likely to be 800,000 acre-feet (an average release of about 13,000 cfs).

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. 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 (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 water 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. While hydrologic conditions have improved, and the severity of drought conditions has eased, it is premature to declare that the drought in the Upper Colorado River Basin is over at this time.

During 2005, Lake Powell reached a low elevation on April 8, 2005, of 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 of 2005, reaching a peak elevation of 3,608.4 feet on July 14, 2005 (91.6 feet from full pool). The current elevation of Lake Powell is 3,602.8 feet (97.2 feet from full pool). Current storage is 12.0 million acre-feet (49 percent of live capacity).

Inflow to Lake Powell was above average during water year 2005 as a whole, but trailed off in the mid to late summer months. Unregulated inflow in the months of July, August, and September was 91, 77, and 68 percent of average, respectively. Fortunately, precipitation in the Upper Colorado River Basin was above average during October, and inflow rebounded. Unregulated inflow in October 2005 was 586,000 acre-feet, 105 percent of average.

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 approximately 3,600 feet.

This release courtesy Tom Ryan, U.S. Bureau of Reclamation