Glen Canyon Dam Operations
Releases from Glen Canyon Dam in April 2007 will average 10,000 cubic feet per second (cfs) with a total of 600,000 acre-feet scheduled to be released for the month. On Mondays through Fridays in April, daily release fluctuations due to load following will likely vary between a low of 6,500 cfs (during late evening and early morning off-peak hours) to a high of 12,500 cfs (during daylight and early evening on-peak hours). On Saturdays and Sundays, release fluctuations will likely vary between a low of 6,500 cfs to a high of 12,000 cfs.
Releases from Glen Canyon Dam in May 2007 will be similar to the April pattern. A total of 600,000 acre-feet are scheduled to be released in May of 2007.
Upper Colorado River Basin Hydrology
The water supply picture in the Colorado River Basin weakened in March 2007. March was a warmer and drier than normal month. Normally, basinwide snowpack continues in increase during the month of March. This was not the case in 2007 as warm temperatures resulted in net loss of snowpack above Lake Powell. While inflow was above average during March 2007 (unregulated inflow for the month was 795,000 acre-feet or 120 percent of average), the resultant is a significantly reduced April through July runoff projection. The National Weather Service in their April final forecast is projecting 4.0 million acre-feet of runoff into Lake Powell during the 2007 April through July period. This is only 50 percent of average.
Water year 2007 (which began on October 1, 2006) started out "wet," with October precipitation over 200 percent of average. Unfortunately, the pattern quickly changed. Precipitation was below average in November and December of 2006, and January and March of 2007. February 2007 precipitation was near average. As we begin the April through July runoff season, snowpack above Lake Powell is only 64 percent of average (as of April 4, 2007). It is nearly certain that inflow to Lake Powell will be below average in 2007.
The current elevation of Lake Powell (April 4, 2007) is 3,599.1 feet, 100.9 feet from full pool elevation of 3,700 feet. Reservoir storage is currently 11.65 million acre-feet, or 48 percent of capacity. The water surface elevation of Lake Powell reached a seasonal low of 3,597.4 feet on March 16, 2007. Under the current inflow forecast Lake Powell would reach a seasonal peak elevation of about 3,606 feet in late June 2007.
Upper Colorado River Basin Drought
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 five-year period, with reservoir storage reaching a low of 8.0 million acre-feet (33 percent of capacity) on April 8, 2005.
Hydrologic conditions improved in water year 2005 in the Upper Colorado River Basin. Lake Powell increased by 2.77 million acre-feet (31 feet in elevation) during water year 2005. Unregulated inflow to Lake Powell in water year 2005 was 105 percent of average.
Unfortunately, in 2006, there was a return to drier conditions in the Colorado River Basin. Unregulated inflow to Lake Powell in water year 2006 was 73 percent of average. Over the past 7 years (2000 through 2006, inclusive) inflow to Lake Powell has been below average in all but one year (2005).
Water year 2007 (which began on October 1, 2006) is shaping up to be yet another year with below average inflow. The current projection for spring runoff into Lake Powell is only 50 percent of average. It is highly likely that inflow to Lake Powell will be below average once again in 2007. Reservoir storage in Lake Powell and Lake Mead is currently 48 and 54 percent of capacity, respectively. The drought in the Colorado River Basin continues.
This release courtesy Tom Ryan, Bureau of Reclamation