March 2002. Beginning Friday May 24, 2002, steady releases of 8,000 cubic feet per second (cfs) will be made from Glen Canyon Dam. This steady 8,000 cfs release sequence will continue for 9 or 10 days (being completed either on June 1 or June 2). A return to normal load following patterns will follow the completion of this 8,000 cfs release. This special release is being made to support research and long-term monitoring of the Grand Canyon. Contractors working for the Grand Canyon Monitoring and Research Center will be collecting airborne images of the Grand Canyon as well as topographic data during this special release
Releases in June will be higher than in May. A total of 747,000 acre-feet will be released from Glen Canyon Dam during June 2002. Releases in most of June (after the steady 8,000 cfs flow sequence is completed) will average about 12,800 cfs.
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.
Water year 2002 is shaping up to be an extremely dry year in the Colorado River Basin. Basinwide precipitation has been significantly below average and snowpack in the Upper Colorado River Basin is currently an abysmal 14 percent of average (as of May 22, 2002). The May mid-month inflow forecast issued by the National Weather Service is calling for 1.6 million acre-feet of unregulated inflow to Lake Powell during this years April through July runoff. This is only 20 percent of average. Since the completion of Glen Canyon Dam, there has been only one year where 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 1.3 million acre-feet.
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.
Unregulated inflow to Lake Powell has been significantly below average so far in water year 2002. Unregulated inflow to Lake Powell in January, February, and March of 2002 was 69, 53, and 45 percent of average, respectively. Unregulated inflow in April 2002 was 380,000 acre-feet, only 39 percent of average.
Three consecutive years of below average hydrology have reduced water storage in Lake Powell. The current elevation of Lake Powell is 3,644 feet (56 feet from full pool). Current storage is approximately 16.5 million acre-feet (68 percent of capacity). Under the 20 percent of average inflow forecast, Lake Powell will not increase in elevation during the April through July time period as it normally does. It is likely that the elevation of Lake Powell will remain near its current level for the remainder of May and the first half of June. By late June, however, the water surface elevation will begin to again decline. The current projection is that by the end of the calendar year, the water surface elevation of Lake Powell will be about 3,620 feet (80 feet below full pool). Hydrologic conditions often change 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 years 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