Glen Canyon Dam Update

A total of 600,000 acre-feet will be released from Glen Canyon Dam during December, 2002, which is an average of 9,800 cubic feet second (cfs). On Mondays through Fridays in December, daily fluctuations will likely vary between a low of about 6,250 cfs (during late evening and early morning off-peak hours) to a high of about 12,250 cfs (during daylight hours and early evening on-peak hours). On Saturdays during December, releases will likely vary between a low of about 6,250 cfs during off-peak hours, to a high of about 12,000 cfs during on-peak hours. On Sundays, releases will likely vary between a low of about 6,250 cfs during off-peak hours to a high of about 10,700 cfs during on-peak hours.

Releases in January, 2003 will be higher than December with a total of 810,000 acre-feet scheduled to be released. Experimental flow tests could begin in January 2003. It is highly unlikely that releases will exceed 20,000 cfs this coming January, even if the test flows are implemented.

On April 24, 2002, members of the Glen Canyon Adaptive Management Work Group (AMWG) recommended to the Secretary of the Interior that a two-year experimental flow test be made from Glen Canyon Dam beginning in water year 2003. The recommendation addressed the decline of two key resources in the Grand Canyon: sediment and population viability of endangered humpback chub. Reclamation, the National Park Service, and the United States Geological Survey have jointly prepared an Environmental Assessment (EA) under the National Environmental Policy Act to document the impacts of these proposed experimental flows. The EA can be found at:

Water year 2002 will be remembered as one of the driest years on record in the Colorado River basin. Unregulated inflow to Lake Powell in water year 2002 was only 3.06 million acre-feet or 25 percent of the 30 year average. This is the lowest unregulated inflow ever recorded since the completion of Glen Canyon Dam in 1963. The previous low occurred in 1977 when inflow to Lake Powell was 3.66 million acre-feet.

Inflow to Lake Powell continues to be significantly below average. Unregulated inflow into Lake Powell in September, 2002 was 58 percent of average, and unregulated inflow in October was 56 percent of average.

Inflow in November will likely be about 370,000 acre-feet or 68 percent of average. Inflow to Lake Powell is expected to remain below average through the winter and early spring. Snowpack in the Colorado River basin is 102 percent of average as of November 27, 2002. It should be noted that early season snowpack figures are usually not indicative of runoff volumes the following spring.

Even though snowpack levels are near average for this time of year, drought conditions persist in the Colorado River basin. The basin received some drought relief during the months of September and October, with basinwide precipitation those months being 185 and 110 percent of average, respectively. Precipitation in the Upper Colorado River basin, in November, will likely end up being below average, however. Soil moisture deficits persist, and such deficits affect spring snowmelt runoff, reducing runoff efficiency, causing greater amounts of water to be lost to the soil.

Drier than average conditions have now prevailed for the past three years in the Colorado River basin. Total unregulated inflow into Lake Powell in water year 2000 and 2001 was 62 and 59 percent of average, respectively and only 25 percent of average in 2002. These low inflows have reduced water storage in Lake Powell. The current elevation of Lake Powell is 3,623.4 feet (76.6 feet from full pool). Current storage is approximately 14.1 million acre-feet (58 percent of capacity). The water surface elevation of Lake Powell will likely continue to decline for the remainder of this year. The current projection shows that the water surface elevation of Lake Powell will be about 3620 feet (80 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, releases from Lake Powell in water year 2003 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.