Glen Canyon Dam Operations
Releases from Glen Canyon Dam in May 2006 will average 9,800 cubic feet per second (cfs) with a total of 600,000 acre-feet scheduled to be released for the month. On Mondays through Fridays in May, daily release fluctuations due to load following will likely vary between a low of 6,000 cfs (during late evening and early morning off-peak hours) to a high of 12,000 cfs (during daylight and early evening on-peak hours). On Saturdays, release fluctuations will likely vary between a low of 6,000 cfs to a high of 11,500 cfs. On Sundays, the range will likely vary from 6,000 cfs to 11,000 cfs.
Releases will be increased in June. Releases from Glen Canyon Dam are scheduled to be 800,000 acre-feet in June 2006 (an average of 13,400 cfs) and 820,000 acre-feet in July 2006.
Upper Colorado River Basin Hydrology
April 2006 precipitation in the Upper Colorado River Basin was below average (approximately 65 percent of average). Significant reductions in snowpack occurred during the month. As April began, basinwide snowpack above Lake Powell was near average (102 percent of average on April 1, 2006, to be precise), but decreased throughout the month due to lack of precipitation and earlier than normal snowmelt. Basinwide snowpack (as of May 3, 2006) is currently 71 percent of average.
The National Weather Service issued the May final inflow forecast on May 3, 2006. Forecasted April through July unregulated inflow to Lake Powell for 2006 is now 6.8 million acre-feet, 86 percent of average. The May inflow forecast was revised downward from the April projection (projected inflow in the April final forecast was 7.7 million acre-feet, 97 percent of average). While not a poor inflow year (like the severe drought years from 2000 through 2004), it is likely that 2006 will be a year with below average inflow to Lake Powell.
Thus far, inflow to Lake Powell in water year 2006 (which began on October 1, 2005) has been about 90 percent of average. Unregulated inflow in April 2006 was 1,014,800 acre-feet, 103 percent of average. Unregulated inflow in January, February, and March was 91, 79, and 68 percent of average, respectively.
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 current (May 3, 2006) elevation of Lake Powell is 3,593.6 feet (106.4 feet from full pool). Current storage is 11.2 million acre-feet (46 percent of live capacity).
Lake Powell will increase in elevation during May, June, and probably in early July as well. The current projected high elevation of Lake Powell for 2006 is about 3,618 feet (82 feet from full pool), occurring in early-July. However, the actual high elevation could deviate from this projection. Weather patterns from now through the end of spring will influence the volume of inflow to Lake Powell during this year's April through July snowmelt runoff season.
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.
The effects of the drought remain visible at Lake Powell where reservoir storage has been reduced. Lake Powell storage is currently 46 percent of capacity.
This release courtesy Tom Ryan, U.S. Bureau of Reclamation