Glen Canyon Dam Operations
Releases from Glen Canyon Dam in June 2006 will average 13,400 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 June, 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 15,500 cfs. On Sundays, the range will likely vary from 9,000 cfs to 15,000 cfs.
Releases in July and August will likely be very similar to releases in June. Releases from Glen Canyon Dam are scheduled to be 822,000 acre-feet in July 2006 (an average of 13,300 cfs) and 824,000 acre-feet in August 2006 (an average of 13,400 cfs).
Upper Colorado River Basin Hydrology
Inflow projections to Lake Powell have been reduced in response to warm and dry spring conditions in the Colorado River Basin. April and May 2006 precipitation in the Upper Colorado River Basin was approximately
65 and 35 percent of average, respectively. The June final inflow forecast, issued by the National Weather Service on June 5, 2006, is projecting April through July unregulated inflow to Lake Powell for 2006 to be 5.9 million acre-feet, 74 percent of average. Inflow projections earlier in the year were significantly higher (the April inflow forecast, for instance, projected Lake Powell inflow to be 97 percent of average). It is now almost a certainty that inflow to Lake Powell will be below average in 2006.
Thus far, inflow to Lake Powell in water year 2006 (which began on October 1, 2005) has been about 89 percent of average. Unregulated inflow in April 2006 was 103 percent of average and unregulated inflow
in May was 89 percent of average. The snow melt runoff has occurred
earlier than normal in 2006. Peak inflow to Lake Powell in 2006 was 41,700 cfs and occurred on May 29, 2006. It is unlikely that inflow will exceed this level the remainder of 2006. There is now only a limited amount of snowpack remaining in the Colorado River Basin.
Inflow volumes in June and July are forecasted to be much below average levels (65 percent of average in June and 55 percent of average in July).
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 (June 6, 2006) elevation of Lake Powell is 3,607.1 feet (92.9 feet from full pool). Current storage is 12.4 million acre-feet (51 percent of live capacity).
Lake Powell will increase in elevation until late June or early July. The current projected high elevation of Lake Powell for 2006 is about 3,613 feet (87 feet from full pool). However, the actual high elevation could deviate from this projection due to weather patterns in June and July.
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.
Inflow to Lake Powell is almost certain to be below average in 2006, however. 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 droughts 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 51 percent of capacity.
This release courtesy Tom Ryan, U.S. Bureau of Reclamation