WSPC12729

• File Number: 8282.600.40
• Description: Colorado River AOP Status Report
• Basin: Colorado Mainstem
• Author: USDOI/BOR
• Title: Colorado River Reservoir Operations Status Reports Partial Part 2 2004, with staff comments
• Water Supply Pro - Doc Type: Data

and plans for this fall and winter 2004 operations were discussed. These are open forum discussions
on the operation of Navajo Reservoir with many interested groups participating. Anyone interested
in the general operation ofthe reservoir is encouraged to attend. Please contact Pat Page in
Reclamation's Durango, Colorado Office at [phone] for information about these meetings or
the daily operation of Navajo Reservoir.

Glen Canvon Dam - Lake Powell

Operations

Releases will be lower in September 2004 than in July and August. A volume of 480,000 acre-feet
is scheduled to be released from Lake Powell in September, which is an average of 8,070 cubic feet
per second (cfs). Releases had been averaging about 14,600 cfs in July and August. On Mondays
through Fridays and on Sundays in September, daily fluctuations due to load following will likely
vary between a low of about 5,000 cfs (during late evening and early morning off-peak hours) to a
high of about 10,000 cfs (during late afternoon and early evening on-peak hours). On Saturdays,
releases will likely vary between a low of about 5,000 cfs during off-peak hours to a high of about
9,750 cfs during on-peak hours. The release pattern in October will likely be similar to September.
A volume of 492,000 acre-feet is scheduled to be released in October, which is an average of8,000
cfs.

Because ofthe draw down condition of Lake Powell, releases from Lake Powell in water year 2004
are being scheduled to meet the minimum release objective of 8.23 million acre-feet. This is
consistent with the requirements of the Criteria for Coordinated Long-Range Operation of Colorado
River Reservoirs.

Upper Colorado River Basin Hydrology

The Colorado River Basin is completing its 5th year of drought. In July 1999, Lake Powell was
essentially full, with reservoir storage at 97 percent of capacity. Since that time, inflow volumes
have been below average for 5 consecutive years. The last month when inflow to Lake Powell was
above average was September 1999. Unregulated inflow in water years 2000, 2001, 2002, and 2003
was 62, 59, 25, and 51 percent of average, respectively. Total unregulated inflow for water year
2004 is likely to be 51 percent of average, almost the same volume as 2003. Inflow in water year
2002 was the lowest ever observed since the completion of Glen Canyon Dam in 1963.

The summer season in the Colorado River Basin has featured cooler than average temperatures with
precipitation at near average levels. With the exception of the Green River Basin above Flaming
Gorge, river flows around the basin have been much below average this summer. Unregulated
inflow to Lake Powell in July was only 35 percent of average and inflow in August will likely end
up being only 29 percent of average. Peak inflow to Lake Powell this year occurred on May 14
(about three weeks earlier than normal) when inflow was 21,400 cfs. As of August 30,2004
observed inflow to Lake Powell was 4,400 cfs about 45 percent of what is normally seen as August
comes to a close.

Low inflows the past 5 years have reduced water storage in Lake Powell. The current elevation (as
of August 30,2004) of Lake Powell is 3,572 feet (128 feet from full pool). Current storage is 9.3
million acre-feet (38 percent oflive capacity).

The water surface elevation at Lake Powell reached a seasonal low of3,582.7 feet on April 2, 2004
and then increased to a seasonal high on June 14,2004, reaching an elevation of3,587.4 feet. The
water surface has since been declining, and will likely continue to decline for the remainder of the