Glen Canyon Dam Update


Releases from Glen Canyon Dam in November will be nearly identical to what they were in October. In November, releases will average 8,000 cfs with a total of 476,000 acre-feet scheduled to be released. On Mondays through Saturdays in November, daily fluctuations due to load following will likely vary between a low of 5,000 cfs (during late evening and early morning off-peak hours) to a high of 10,000 cfs (during late afternoon and early evening on-peak hours). On Sundays, releases will be 5,000 cfs from 7 pm until 7 am, and 8,000 cfs from 7 am until 7 pm.

Releases from Glen Canyon Dam in December of 2003 will likely be higher than November. The volume releases in December is likely to be 600,000 acre-feet (an average release of about 10,000 cfs).

Because of the draw down condition of Lake Powell, releases from Lake Powell in water year 2004 are being scheduled to meet the minimum objective release of 8.23 million acre-feet. This is consistent with the requirements of the Criteria for Coordinated Long-Range Operation of Colorado River Reservoirs.

Basin Hydrology

Severe drought conditions in the Colorado River Basin continue. As we move into a new water year there are no signals of the drought easing. Water year 2004 began on October 1, 2003 and the first month of our new water year was much warmer and drier than average. Basinwide precipitation in October was only about 30 percent of average. Soil moisture levels throughout the basin are very low, and as we move into winter it appears likely that the snowpack will be building upon these very dry soils. The scenario is not favorable for next spring's runoff, as much of the melting snow will be absorbed by the dry soil. Reclamation is estimating that with average snowpack conditions this winter, runoff next spring would be about 75 percent of average.

The Colorado River Basin is now in its 5th year of drought. Inflow volumes have been below average for 4 consecutive years. Unregulated inflow in water year 2003 was only 53 percent of average. Unregulated inflow in 2000, 2001 and 2002 was 62, 59, and 25 percent of average, respectively. Inflow in 2002 was the lowest ever observed since the completion of Glen Canyon Dam in 1963.

The trend of low inflow continues. Unregulated inflow in October, 2003 will end up being only 55 percent of average. As of October 31, 2003 observed inflow to Lake Powell is about 6,000 cfs, about 58 percent of what is usually seen in late October.

Low inflows have reduced water storage in Lake Powell. The current elevation of Lake Powell is 3,602.0 feet (98.0 feet from full pool). Current storage is approximately 11.9 million acre-feet (49 percent of capacity). The good news is that even after 4 years of severe drought, Lake Powell is still storing a large volume of water (nearly 12 million acre-feet).

Experimental Flows

Daily high fluctuating releases from Glen Canyon Dam, as part of the Glen Canyon Dam experimental flows, were completed on March 31, 2003. From January through March 2003 releases ranged between a high of 20,000 cfs to a low of 5,000 cfs each day. These same high fluctuating releases are scheduled to be repeated in January through March of 2004.

The January through March high fluctuating releases were intended to benefit the endangered humpback chub. Scientists have recognized that the humpback chub population has been in general decline since highly fluctuating flows were curtailed in November of 1991. Those flows helped keep the non-native fish, especially the rainbow and brown trout, in check. The trout are thought to prey upon and compete with native fish such as the endangered humpback chub.

The experimental flows from Glen Canyon Dam received environmental clearances in December 2002. The flows were analyzed in an environmental assessment in accordance with the National Environmental Policy Act. The experimental flows are the result of ongoing studies by scientists from the United States Geological Survey and were recommended by the Glen Canyon Dam Adaptive Management Work Group, a Federal advisory committee. The experimental flows address the decline of two key resources in the Grand Canyon: sediment and population viability of endangered humpback chub. The Finding of No Significant Impact on the experimental flows can be found at

This release courtesy Tom Ryan.