Glen Canyon Dam Update

Lake Powell - Glen Canyon Dam - Current Status - Feb. 5th, 2008
Glen Canyon Dam Operations

Releases from Glen Canyon Dam in February 2008 will average 10,400 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 February, 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 14,500 cfs (during daylight and early evening on-peak hours). On Saturdays and Sundays, release fluctuations will likely vary between a low of 8,500 cfs to a high of 14,000 cfs.

In March 2008, a high flow test may be implemented. As a result of information resulting from scientific monitoring and research activities and stakeholder discussions in the Glen Canyon Dam Adaptive Management Program, Reclamation has proposed a 2008 high flow test. The release characteristics of such a test would be identical to the test conducted in November 2004 (with a maximum release of about 41,500 cfs for 60 hours), but under much more highly enriched fine sediment conditions, a unique situation during the last 10 years. The purpose of this test would be to determine the effectiveness of rebuilding and reworking sandbar deposits and backwaters in Marble and Grand Canyons. The Department of the Interior has concurred with (1) Reclamation's proposal to initiate environmental compliance activities on the proposed test, and (2) the United States Geological Survey's proposal to continue planning and scheduling scientific monitoring and research activities related to the test. The test is proposed to occur in early March; however, a final decision on whether to conduct such a test has not been made. Such a decision is currently expected to be made about mid-February 2008, only after environmental compliance actions are complete. The scheduled release volume for March 2008 in the current 24 month study is 600,000 acre-feet. If the high flow test occurs as proposed, the release volume for March 2008 may be adjusted to accommodate this test. The annual release from Lake Powell for water year 2008 would not change as a result of the high flow test.

Upper Colorado River Basin Hydrology

Precipitation in the Upper Colorado River Basin was 160 percent of average in January 2008. This was the second month in a row where basin precipitation was well above normal making up for a very dry November 2007. Basin wide snowpack was only 35 percent of average on November 29, 2007, but has increased steadily during December 2007 and January 2008 to 132% of average on February 4, 2008. The climate outlook over the next 3 months is for near normal precipitation and above normal temperatures.

Inflow to Lake Powell is currently 7,400 cfs (February 4, 2008). Total unregulated inflow to Lake Powell so far in water year 2008 (October through January) is 82 percent of average with January measured at 83 percent of average.

Forecasted April through July unregulated inflow to Lake Powell in 2008 is 9.5 million acre-feet, 120 percent of average (February final forecast). This inflow projection could shift depending upon climate patterns the remainder of the winter and into the spring. Typically by February 1st, the snow accumulation season is about 60% complete.

The current elevation of Lake Powell (February 4, 2008) is 3,590.5 feet, 109.5 feet from full pool elevation of 3,700 feet. Reservoir storage is currently 10.87 million acre-feet, or 45 percent of capacity. The water surface elevation of Lake Powell is now near its seasonal low. In April, anticipated snowmelt runoff will cause the water surface elevation to begin to increase. Under the current inflow forecast, Lake Powell would reach a peak elevation of about 3639 feet in July 2008. The peak elevation for Lake Powell in 2007 was 3,611.7 feet.

Upper Colorado River Basin Drought

The Upper Colorado River Basin is experiencing a protracted multi-year drought. Since 1999, inflow to Lake Powell has been below average in every year except one.

In the summer of 1999, Lake Powell was essentially full with reservoir storage at 23.5 million acre-feet, or 97 percent of capacity. Inflow to Lake Powell in 1999 was 109 percent of average. The manifestation of drought conditions in the Upper Colorado River Basin began in the fall months of 1999. A five year period of extreme drought occurred in water years 2000, 2001, 2002, 2003, and 2004 with unregulated inflow to Lake Powell only 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.

Drought conditions eased in water year 2005 in the Upper Colorado River Basin. Precipitation was above average in 2005 and unregulated inflow to Lake Powell was 105 percent of average. Lake Powell increased by 2.77 million acre-feet (31 feet in elevation) during water year 2005. But as is often the case, one favorable year does not necessarily end a protracted drought. In 2006, there was a return to drier conditions in the Colorado River Basin. Unregulated inflow to Lake Powell in water year 2006 was only 71 percent of average.

Water year 2007 was another year of below average inflow with unregulated inflow into Lake Powell at 68 percent of average. Over the past 8 years (2000 through 2007, inclusive), inflow to Lake Powell has been below average in all but one year (2005).

Reservoir storage in Lake Powell and Lake Mead has decreased during the past 8 years. Reservoir storage in Lake Powell is 45 percent of capacity. Storage in Lake Mead is 50 percent of capacity.

Updated: February 5, 2008

This release courtesy of Rick Clayton, Bureau of Reclamation.