Glen Canyon Dam Update

Glen Canyon Dam Operations

Releases from Glen Canyon Dam in August 2006 will average 13,400 cubic feet per second (cfs) with a total of 824,000 acre-feet scheduled to be released for the month.  On Mondays through Fridays in August, daily release fluctuations due to load following will likely vary between a low of 9,500 cfs (during late evening and early morning off-peak hours) to a high of 17,500 cfs (during daylight and early evening on-peak hours).  On Saturdays, release fluctuations will likely vary between a low of 9,500 cfs to a high of 17,500 cfs.  On Sundays, the range will likely vary from 9,500 cfs to 15,500 cfs.

Releases in September 2006 will be lower.  The volume of release scheduled in September is 540,000 acre-feet (an average of 9,000 cfs).

Upper Colorado River Basin Hydrology

April through July unregulated inflow to Lake Powell was 5.14 maf, or 67 percent of the 30 year average.  Precipitation in the Colorado River Basin in water year 2006 was near average until April 2006.  April, May and June were warm dry months in the basin with basinwide precipitation in April, May and June only 50 percent of average.  These dry spring conditions resulted in a reduction of April through July inflow from what was projected earlier in the year (the April inflow forecast, for instance, projected Lake Powell April through July inflow to be 97 percent of average).  Warm, dry spring conditions also resulted in an earlier runoff than normal.  Unregulated inflow to Lake Powell in April, May, June and July was 103, 89, 53, and 40 percent of average, respectively.  Projected unregulated inflow to Lake Powell for water year 2006 is 8.78 maf, or 73 percent of average.

The water surface elevation of Lake Powell reached a seasonal low on April 7, 2006, at elevation 3,588.7 (111.3 feet from full pool).  The water surface increased from April 7, 2006, until June 22, 2006, when Lake Powell reached a seasonal peak of 3,610.9 (89.1 feet from full pool).  Since that time (June 22nd), the elevation of Lake Powell has been decreasing.  The current (August 9, 2006) elevation of Lake Powell is 3,606.0 feet (94.0 feet from full pool).  Current storage is 12.3 million acre-feet (50 percent of live capacity).

The water surface elevation of Lake Powell will likely continue to decrease through the summer, fall, and winter of 2006 until April 2007, when anticipated snowmelt runoff will cause the water surface level to increase once more.  The projected elevation of Lake Powell on January 1, 2007, is about 3,598 feet.

Upper Colorado River Basin Drought

The Upper Colorado River Basin experienced five consecutive years of extreme drought from September 1999 through September 2004.  In the summer of 1999, Lake Powell was essentially full with reservoir storage at 97 percent of capacity.  Inflow volumes for five consecutive water years were significantly below average.  Total unregulated inflow in water years 2000, 2001, 2002, 2003, and 2004 was 62, 59, 25, 51, and 49 percent of average, respectively.  Lake Powell storage decreased through this five-year drought, with reservoir storage reaching a low of 8.0 million acre-feet (33 percent of capacity) on April 8, 2005. 

Hydrologic conditions improved in water year 2005 in the Upper Colorado River Basin.  Lake Powell increased by 2.77 million acre-feet (31 feet in elevation) during water year 2005.  Unregulated inflow to Lake Powell in water year 2005 was 105 percent of average. 

Unfortunately, in 2006, there has been a return to drier condition in the Colorado River Basin.  Inflow to Lake Powell is almost certain to be below average in 2006.  The current projection for inflow to Lake Powell in water year 2006 is 73 percent of average.  Over the past 7 years (2000 through 2006, inclusive) inflow to Lake Powell will have been below average in all but one year (2005).  While drought conditions eased in 2005, and the inflow in 2006 is not expected to be as extremely low as what occurred in 2000 through 2004, the drought in the Colorado River Basin may not be over.  Historical records show that it is common to have 1 or 2 above average years during sustained multi-year droughts.

The effects of multiple years of low inflow remain visible at Lake Powell where reservoir storage has been reduced.  Lake Powell storage is currently 50 percent of capacity.

This release courtesy Tom Ryan, United States Bureau of Reclamation