Glen Canyon Dam Update

Glen Canyon Dam Operations

Releases from Glen Canyon Dam in December 2006 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 Fridays in December, daily release fluctuations due to load following will likely vary between a low of 9,000 cfs (during late evening and early morning off-peak hours) to a high of 17,000 cfs (during daylight and early evening on-peak hours). On Saturdays, release fluctuations will likely vary between a low of 9,000 cfs to a high of 16,000 cfs. On Sundays, release fluctuations will likely vary between a low of 9,000 cfs to a high of 15,500 cfs.

Releases in January 2007 will likely be very similar to December 2006. A total of 800,000 acre-feet (an average of 13,000 cfs) are scheduled to be released in January 2007

Upper Colorado River Basin Hydrology

The "Four Corners" region experienced extraordinary amounts of precipitation during October 2006. Precipitation events were particularly intense in the vicinity of Lake Powell. Record-breaking daily flows for the month of October were observed on the San Juan, Dolores, San Rafael, Fremont/Dirty Devil, Escalante, and Paria Rivers in the first half of October. The most exceptional of these high flows were the flood flows on the Fremont/Dirty Devil on October 6 and 7, 2006. The stage (level of the river) of the Dirty Devil (at the "Dirty Devil above Poison Springs Wash near Hanksville, Utah" surface water discharge station) increased by more than 15 feet during the flood event. Initial calculations from hydrologists working for the United States Geological Survey estimate an instantaneous peak flow of about 42,000 cfs on the Dirty Devil on October 6 or October 7, 2006.

Inflow from the Dirty Devil River and other drainages which outlet into Lake Powell resulted in remarkable increases in Lake Powell on October 6, October 7, and October 8, 2006. Daily increases in the water surface elevation of Lake Powell on these three days were 1.33 feet, 0.97 feet, and 0.74 feet, respectively. Lake Powell rarely increases in storage during the month of October. However, in October 2006, Lake Powell increased in storage by 609,000 acre-feet, gaining 6.2 feet in elevation.

While October 2006 was a very wet month in the Upper Colorado River Basin, normal conditions returned in November. Aggregate precipitation above Lake Powell during October 2006 was over 200 percent of average. November 2006 basinwide precipitation was approximately 85 percent of average. Unregulated inflow into Lake Powell in November was 559,000 acre-feet, or 103 percent of average.

The current elevation of Lake Powell (December 4, 2006) is 3,606.5 feet. Reservoir storage is currently 12.38 million acre-feet, 51 percent of capacity.

The water surface elevation of Lake Powell is likely to decrease between now and April 2007 when anticipated snowmelt runoff will cause the water surface level to increase once more. The projected elevation of Lake Powell on January 1, 2007, is approximately 3,604 feet. The current projection for April 1, 2007 is approximately 3,598 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 condition 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 off to a good start. Precipitation in the Colorado River Basin in October 2006 was over 200 percent of average, and Lake Powell increased by 6.2 feet during the month, in large part due to exceptional precipitation events in the regions surrounding the lake. Nevertheless, historical records show that it is common to have periods of above average precipitation and runoff during a protracted multi-year drought. The drought in the Colorado River Basin may not be over.

This release courtesy Tom Ryan, United States Bureau of Reclamation.