RRFW Riverwire – Glen Canyon Dam Update
December 6, 2007
Glen Canyon Dam Operations
Releases from Glen Canyon Dam in December 2007 will average 13,000 cubic feet per second (cfs) with a total of 800,000 acre-feet scheduled to be released for the month. On Mondays through Fridays in December, 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 and Sundays, release fluctuations will likely vary between a low of 9,000 cfs to a high of 16,000 cfs.
Releases in January 2008 are scheduled to be the same as December 2007 (800,000 acre-feet). The load following pattern in January 2008 will likely be very similar to December 2007.
Upper Colorado River Basin Hydrology
November 2007 was a “dry” month in Upper Colorado River Basin. Fortunately, a major storm system reached the basin the final day of November. Prior to this storm, basinwide snowpack was extremely low (only 35 percent of average on November 29, 2007). Basinwide snowpack was boosted by this storm, and is currently 71 percent of average (December 5, 2007). Another major storm system is approaching the Colorado River Basin, and is forecasted to delivery significant amounts of moisture December 7-8, 2008.
Inflow to Lake Powell is currently 9,800 cfs (December 5, 2007). Total unregulated inflow in October and November 2007 was 85 and 73 percent of average, respectively.
April through July unregulated inflow to Lake Powell in 2007 was 4.05 million acre-feet, only 51 percent of average. Water year inflow to Lake Powell for 2007 (October 2006 through September 2007) was 68 percent of average.
The current elevation of Lake Powell (December 5, 2007) is 3,598.3 feet with 11.59 million acre-feet of storage (48 percent of capacity).
The water surface elevation of Lake Powell will likely decrease between now and March of 2008. The current projected elevation of Lake Powell on January 1, 2008 is 3,594 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 71 percent of average.
Water year 2007 was another year of below average inflow with unregulated inflow into Lake Powell at 68 percent of average. Over the past 8 years (2000 through 2007, inclusive), inflow to Lake Powell has 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 is 48 percent of capacity. Storage in Lake Mead is also 48 percent of capacity.
This release courtesy Tom Ryan, USBOR
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