Glen Canyon Dam Operations
Releases from Glen Canyon Dam in March 2007 will average 9,800 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 March, daily release fluctuations due to load following will likely vary between a low of 7,000 cfs (during late evening and early morning off-peak hours) to a high of 13,000 cfs (during daylight and early evening on-peak hours). On Saturdays and Sundays, release fluctuations will likely vary between a low of 7,000 cfs to a high of 12,000 cfs.
Releases from Glen Canyon Dam in April and May 2007 will be similar to the March pattern. A total of 600,000 acre-feet are scheduled to be released in April and May of 2007.
Upper Colorado River Basin Hydrology
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 in the Colorado River Basin was below average in November, December, and January. January 2007 was particularly poor, with the Upper Basin receiving about 60 percent of average precipitation during the month. Precipitation figures in February 2007 are better, but not enough to substantially shift the water supply picture. Upper Basin precipitation for February 2007 was about average, with precipitation the first half of February being below average, and precipitation the second half above average.
Basinwide snowpack above Lake Powell is currently 81 percent of average (as of March 5, 2007).
Forecasted April through July unregulated inflow to Lake Powell in 2007 is 5.6 million acre-feet, 71 percent of average (March final forecast). The current inflow projection could shift depending upon climate patterns this spring. However, there is now only about a 1 in 8 probability that April through July inflow to Lake Powell will be above average in 2007. This would occur only under a scenario where spring precipitation is much above average, particularly in the months of March and April.
The current elevation of Lake Powell (March 5, 2007) is 3,597.8 feet, 102.2 feet from full pool elevation of 3,700 feet. Reservoir storage is currently 11.52 million acre-feet, or 47 percent of capacity. The water surface elevation of Lake Powell is now near its seasonal low. The lake will likely decrease by one additional foot before anticipated snowmelt runoff, which usually begins in early to mid-April, will cause the water surface elevation to increase once more. Under the current inflow forecast Lake Powell would reach a peak elevation of about 3,615 feet in late June or early July 2007. The peak elevation for Lake Powell in 2006 was 3,611 feet.
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 trending dry. October 2006 featured much above average precipitation, but in the months of November, December, and January, the basin received below average precipitation. The current projection for spring runoff into Lake Powell is 71 percent of average. It is likely that inflow to Lake Powell will be below average once again in 2007. Storage in Lake Powell and Lake Mead remains relatively low, with reservoir storage currently 47 and 55 percent of capacity, respectively. The drought in the Colorado River Basin lingers on.
This release courtesy Tom Ryan, USBOR