Glen Canyon Dam Update

Glen Canyon Dam Operations

In May 2005, a volume of 605,000 acre-feet is scheduled to be released from Lake Powell, which is an average of 9,800 cubic feet per second (cfs). On Mondays through Saturdays in May, daily fluctuations due to load following will likely vary between a low of about 7,000 cfs (during late evening and early morning off-peak hours) to a high of about 13,000 cfs (during late afternoon and early evening on-peak hours). On Sundays, releases will likely vary between a low of about 7,000 cfs during off-peak hours to a high of about 11,500 cfs during on-peak hours.

Over Memorial Day weekend, there are four days where steady releases of 8,000 cfs will be scheduled. This steady 8,000 cfs release is being made as part of the Grand Canyon Monitoring and Research Center's annual over flight for data collection essential for research and long-term monitoring of the Grand Canyon. Releases will be ramped down the afternoon of May 26 so that the 8,000 cfs release is achieved by 6 p.m. mountain standard time. The 8,000 cfs flow will then be maintained through the holiday weekend until Tuesday morning (May 31), when a normal load-following pattern is scheduled to be reestablished. It is possible, however, that a return to a load-following release pattern may be reinstated on Memorial Day (May 30). It is also possible that the steady release of 8,000 cfs may be extended for up to 3 additional days (May 30, June 1, and June 2). The exact date and time that operations return to normal load following will depend upon when the data collection activity is completed.

A volume of 800,000 acre-feet is scheduled to be released in June.

This is an average flow of 13,400 cfs. The exact load-following pattern has not yet been finalized, but releases in June are likely to vary between a low of about 9,000 cfs to a high of about 17,000 cfs.

Because of the draw down condition of Lake Powell, releases from Lake Powell in water year 2005 are being scheduled to meet the annual release objective of 8.23 million acre-feet.

Upper Colorado River Basin Hydrology

The Colorado River Basin has now completed 5 consecutive years of extreme drought. In the summer of 1999, Lake Powell was essentially full with reservoir storage at 97 percent of capacity. Since that time, inflow volumes have been below average for 5 consecutive water years.

Total unregulated inflow to Lake Powell in water year 2004 was only 51 percent of average. Unregulated inflow in water years 2000, 2001, 2002, and 2003 was 62, 59, 25, and 51 percent of average, respectively.

Inflow in water year 2002 was the lowest ever observed since the completion of Glen Canyon Dam in 1963.

Hydrologic conditions have improved over the past 8 months in the Upper Colorado River Basin. Since September 2004, precipitation in the Upper Basin has been above average. Rains in the fall of 2004 helped reduce soil moisture deficits caused by the drought. River flows also responded to the fall rains with increased flows. November 2004, for instance, was the first month with above average inflow to Lake Powell since September of 1999.

Snowpack in the Upper Colorado River Basin ranged from average to moderately above average throughout the winter of 2004-2005. Snowpack in the Basin above Lake Powell is currently 114 percent of average (as of May 4, 2005).

Snowmelt runoff began in April 2005, with inflow to Lake Powell increasing significantly in mid-April. Observed inflow so far in 2005 has been as high as 27,800 cfs (April 27, 2004). This flow exceeds last year's peak inflow (21,400 cfs on May 14, 2004). Inflow has declined somewhat in the last week in response to cooler than average temperatures in the Upper Colorado River Basin. Observed inflow on May 4, 2005, was 24,900 cfs. Inflow is expected to increase substantially in the latter part of May. Peak daily inflow is likely to exceed 50,000 cfs in May and/or June of this year.

Total unregulated inflow to Lake Powell in April 2005 was 1,188,000 acre-feet, which is 121 percent of average.

Lake Powell reached a low elevation on April 8, 2005, at 3,555.1 feet

(144.9 feet from full pool). Reservoir storage had declined to 33 percent of live capacity. The last time Lake Powell had been this low was in May 1969. The water surface elevation has been increasing since April 8. As of May 4, 2005, the elevation of Lake Powell is 3,564.5 feet (135.5 feet from full pool). Current storage is 8.65 million acre-feet (36 percent of live capacity).

The National Weather Service (in their May final inflow forecast) is forecasting 8.6 million acre-feet of unregulated inflow to Lake Powell this April through July. This is 108 percent of average. The elevation of Lake Powell is projected to increase through mid-July of 2005.

Current projections (using the May final inflow forecast) show Lake Powell reaching a peak water surface elevation in July 2005 of about 3,602 feet. It should be noted, however, that there remains uncertainty with these projections. Weather conditions this spring could result in shifts to inflow projections for 2005.

This release courtesy Tom Ryan, US Bureau of Reclamation.