Releases from Glen Canyon Dam in December 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 Saturdays in December, 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 16,500 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 Sundays, releases will likely vary between a low of 8,500 cfs to a high of 16,000 cfs.
Releases from Glen Canyon Dam in January 2006 will likely be the same as December. 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.
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 3,602.2 feet (97.8 feet from full pool). Current storage is 11.9 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 105 percent of average. Unregulated inflow in November 2005 was 515,000 acre-feet or 95 percent of average.
Basinwide snowpack in the Upper Colorado River Basin is currently 86 percent of average (as of December 2, 2005). It is very early in the snow season, however, and this figure has limited significance.
The water surface elevation of Lake Powell is likely to decrease 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. The current projection for April 1, 2006, is approximately 3,592 feet.
This release courtesy Tom Ryan, U.S. Bureau of Reclamation