Glen Canyon Dam Operations
Releases from Glen Canyon Dam in February will average 14,400 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 February, daily release fluctuations due to load following will likely vary between a low of 10,000 cfs (during late evening and early morning off-peak hours) to a high of 18,000 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 Sundays, releases will likely vary between a low of 10,000 cfs to a high of 16,500 cfs.
Releases from Glen Canyon Dam will likely be reduced in March 2006.
The current schedule is for 600,000 acre-feet (an average release of about 9,750 cfs) to be released in March. Releases in April 2006 are currently scheduled to be 600,000 acre-feet as well.
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. Lake Powell storage decreased through this 5 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 (October 2004 through September 2005) in the Upper Colorado River Basin. The elevation of Lake Powell increased by 31 feet from October 1, 2005 to October 1, 2006 and storage in Lake Powell increased by 2.77 million acre-feet during this same period. Unregulated inflow to Lake Powell in water year 2005 was 105 percent of average.
Thus far, water year 2006 (which began on October 1, 2005) is shaping up to be an average inflow year for Lake Powell. Unregulated inflow in
October, November, and December of 2005 was 105, 95 and 82 percent of average, respectively. Unregulated inflow in January 2006 was 368,000 acre-feet, 91 percent of average. Forecasted April through July unregulated inflow to Lake Powell in 2006 is 8.3 million acre-feet, 105 percent of average. This the February preliminary forecast issued by the National Weather Service on February 1, 2006.
The current elevation of Lake Powell is 3,594.2 feet (105.8 feet from full pool). Current storage is 11.2 million acre-feet (46 percent of live capacity).
Basinwide snowpack in the Upper Colorado River Basin is currently 105 percent of average (as of February 1, 2006). Precipitation in the basin since October 1, 2005 has been about 110 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 42 percent of average, while snowpack in the Yampa and Colorado River headwaters is about 130 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 for the water surface elevation at Lake Powell on April 1, 2006, is about 3,590 feet. The current projected high elevation of Lake Powell in 2006 is about 3,630 feet, 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.
This release courtesy Tom Ryan, U.S. Bureau of Reclamation