Releases from Glen Canyon Dam in July will be moderately higher than in June. A total of 900,000 acre-feet will be released from Glen Canyon Dam during July 2002. On Mondays through Fridays in July, daily fluctuations due to load following will likely vary between a low of about 10,000 cfs (during late evening and early morning off-peak hours) to a high of about 18,000 cfs (during late afternoon and early evening on-peak hours). On Saturdays during this period, releases will likely vary between a low of about 10,000 cfs during off-peak hours, to a high of about 16,500 cfs during on-peak hours. On Sundays, releases will likely vary between a low of about 10,000 cfs during off-peak hours to a high of about 15,000 cfs during on-peak hours.
August releases will likely be the same as July. A total of 900,000 acre-feet are scheduled to be released in August, 2002 which averages out to 14,600 cfs. September releases will be much lower than August. Releases in September, 2002 will likely be 475,000 acre-feet which averages out to 8,000 cfs.
Water year 2002 continues to be an extremely dry year in the Colorado River basin. The July preliminary inflow forecast issued by the National Weather Service is calling for 1.30 million acre-feet of unregulated inflow to Lake Powell during the April through July runoff period. This is only 16 percent of average. Since the completion of Glen Canyon Dam, there has been only one year where April through July inflow was below the level projected for 2002. This was the very dry year of 1977 when April through July inflow to Lake Powell was only 1.28 million acre-feet. It is possible that 2002 April through July inflow could end up being below the 1977 total.
Unregulated inflow to Lake Powell during May, and June 2002 was the lowest ever recorded since closure of Glen Canyon Dam in 1963. In May and June, only 312,000 and 364,000 acre-feet, respectively, of unregulated inflow reached Lake Powell, breaking the previous lows of 328,000 acre-feet and 438,000 acre-feet, which occurred in May and June of 1977. Much below average inflow is expected to continue through the summer into the fall.
Drier than average conditions have now prevailed for the past three years in the Colorado River basin. Both water years 2000 and 2001 were below average inflow years. Total unregulated inflow into Lake Powell in water year 2000 was 62 percent of average, while water year 2001 registered inflow at 59 percent of average.
On April 24, 2002, members of the Glen Canyon Adaptive Management Work Group (AMWG) recommended experimental flow tests similar to the 1996 Beach/Habitat-Building Test Flow in which high flows (45,000 cfs) were released to test the ability of those flows to create beaches and conserve sediment for resource management purposes in the Grand Canyon. The new test would be triggered if substantial new sediment inputs come into the system, and if the monitoring and research shows that the antecedent conditions have retained that sediment so it is available for beach/habitat building. The AMWG is a federally chartered advisory group to Secretary of the Interior Gale Norton. The AMWG will forward the recommendation to Secretary Norton. More information on the recommended experimental flows can be found at www.uc.usbr.gov/pao/exp_flows_glencanyondam.html.
Three consecutive years of below average hydrology have reduced water storage in Lake Powell. The current elevation of Lake Powell is 3,640.6 feet (59.4 feet from full pool). Current storage is approximately 16.1 million acre-feet (66 percent of capacity). The water surface elevation of Lake Powell will continue to decline for the remainder of this year. The current projection shows that the water surface elevation of Lake Powell will be about 3625 feet (75 feet below full pool) on January 1, 2003. Hydrologic conditions often change, however, and the actual end-of-year elevation of Lake Powell will depend, in large part, on weather conditions in the Colorado River Basin from now through the end of the year.
Because of the draw down condition of Lake Powell, and this year's expected low runoff, releases from Lake Powell in water year 2002 are being scheduled to meet the minimum objective release of 8.23 million acre-feet. This is consistent with the requirements of the 1970 Criteria for Coordinated Long-Range Operation of Colorado River Reservoirs.
This release courtesy Tom Ryan