Glen Canyon Dam Operations
Releases from Glen Canyon Dam in July 2007 will average 13,100 cubic feet per second (cfs) with a total of 804,000 acre-feet scheduled to be released for the month. On Mondays through Fridays in July, daily release fluctuations due to load following will likely vary between a low of 9,000 cfs (during late evening and early morning off-peak hours) to a high of 17,000 cfs (during daylight and early evening on-peak hours). On Saturdays, release fluctuations will likely vary between a low of 9,000 cfs to a high of 16,000 cfs. On Sundays, release fluctuations will likely vary between a low of 9,000 cfs to a high of 15,000 cfs.
Releases from Glen Canyon Dam in August 2007 will be similar to July. A total of 804,000 acre-feet is scheduled to be released August 2007, which is an average flow of 13,100 cfs. Releases are scheduled to be decreased in September. The current schedule shows 603,000 acre-feet of release in September 2007.
Upper Colorado River Basin Hydrology
Inflow to Lake Powell in June was much below average, but was greater than the volume forecasted. Unregulated inflow to Lake Powell in June 2007 was 1,307,500 acre-feet (42 percent of average). Projected unregulated inflow for June 2007 was 1,100,000 acre-feet, so while actual inflow was much below average, it was 207,500 acre-feet above the level forecasted.
April through July unregulated inflow to Lake Powell in 2007 is expected to be about 4.2 million acre-feet which is 53 percent of average. Water year inflow to Lake Powell for 2007 (October 2006 through September 2007) is projected to be 70 percent of average. The 2007 water year inflow was boostedby the heavy storm events that took place in October 2006 resulting in Lake Powell increasing by 6.2 feet during that particular month.
Lake Powell reached a seasonal peak elevation of 3,611.7 feet on June 25, 2007. The current elevation of Lake Powell (July 5, 2007) is 3,611.2 feet with 12.85 million acre-feet of storage (53 percent of capacity).
The water surface elevation of Lake Powell will likely decrease between now and March of 2008. The projected elevation of Lake Powell on January 1, 2008 is 3,599 feet.
Upper Colorado River Basin Drought
The Upper Colorado River Basin is experiencing a protracted multi-year drought. Since 1999, inflow to Lake Powell has been below average in every year except one.
In the summer of 1999, Lake Powell was essentially full with reservoir storage at 23.5 million acre-feet, or 97 percent of capacity. Inflow to Lake Powell in 1999 was 109 percent of average. The manifestation of drought conditions in the Upper Colorado River Basin began in the fall months of 1999. A five year period of extreme drought occurred in water years 2000, 2001, 2002, 2003, and 2004 with unregulated inflow to Lake Powell only 62, 59, 25, 51, and 49 percent of average, respectively. Lake Powell storage decreased through this five-year period, with reservoir storage reaching a low of 8.0 million acre-feet (33 percent of capacity) on April 8, 2005.
Drought conditions eased in water year 2005 in the Upper Colorado River Basin. Precipitation was above average in 2005 and unregulated inflow to Lake Powell was 105 percent of average. Lake Powell increased by 2.77 million acre-feet (31 feet in elevation) during water year 2005. But as is often the case, one favorable year does not necessarily end a protracted drought. In 2006, there was a return to drier conditions in the Colorado River Basin. Unregulated inflow to Lake Powell in water year 2006 was only 73 percent of average.
Water year 2007 will be another year of below average inflow. The current projection for April through July runoff into Lake Powell is only 53 percent of average. Projected inflow to Lake Powell for the entire 2007 water year is 70 percent of average. With 2007 projected to be a below average inflow year, one sees that over the past 8 years (2000 through 2007, inclusive) inflow to Lake Powell will have been below average in all but one year (2005).
Reservoir storage in Lake Powell and Lake Mead has decreased during the past 8 years. Reservoir storage in Lake Powell and Lake Mead is currently 53 and 49 percent of capacity, respectively.
Courtesy Tom Ryan, Bureau of Reclamation