WSP00672

• File Number: 822.600.10
• Description: Colorado River Annual Operating Plan - Annual Reports
• Basin: Colorado Mainstem
• Date: 1/1/1993
• Author: USDOI/BOR
• Title: Annual Operating Plan
• Water Supply Pro - Doc Type: Annual Report

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8

Black Canyon and maximize recreation potential, releases during 1993 will be carefully
planned to minimize large fluctuations in the daily and monthly flows.

Navajo Reservoir

The 1992 April through July runoff was 790,000 AF or 103 percent of average. Navajo
Reservoir nearly filled in April 1992 and releases of 4,000 cfs were made in order to bypass
the larger than expected April inflow.

Section 7 consultation with FWS for the construction of the Animas-LaPlata Project was
completed in 1992. A 7 year study to evaluate alternative operations of Navajo Reservoir to
benefit endangered fish were outlined in the FDBO. In accordance with this 7 year study,
spring operations of Navajo were modified in 1992 and large releases of up to 4,500 cfs
were made in order to study the effect of large spring flows on the spawning success of
Colorado River squawfish. After the completion of the large spring releases, flows were
reduced to approximately 600 cfs. The objective is to maintain a minimum release of
500 cfs from the reservoir to meet downstream water rights and to preserve the blue ribbon
sport fishery located immediately downstream of the reservoir.

In 1993, Navajo Reservoir is expected to be 3 feet short of fIlling under the most probable
inflow scenario. Releases from the reservoir will be held near 500 cfs through the fall and
winter months and large releases will be made in May and June in order to provide better
spawning conditions for endangered Colorado River squawfish located in the San Juan River.
Additionally, specific releases will be made from the reservoir in order to study habitat
requirements of the squawfish.

Lake Powell

The years 1987 through 1992 have been the lowest 6 COl1secutive years of inflow into Lake
Powell on record. Maintaining the minimum release objective of 8.23 MAF annually from
Lake Powell as set forth in the Operating Criteria during these years has reduced the
reservoir storage by 9.8 MAF. By September 30, 1992, it is expected that Lake Powell will
be about 76 feet from full or 58 percent of capacity at 14.1 MAF. The reservoir storage is
projected to continue to decline through the fall and winter, reaching a seasonal low in
March 1993 of about 90 feet from full at 12.8 MAF.

During water year 1993, the minimum release objective of 8.23 MAF as set forth in the
Operating Criteria will be met. Under most probable inflow conditions, the reservoir will
only recover to a level about 63 feet from full or 15.7 MAF. Due to the extended drought,
it will take approximately 10 years of average inflow to refill the reservoir.

During water year 1993, the interim flow restrictions placed on the releases from Glen
Canyon in 1992 will continue. These interim flow restrictions are based on the best technical
information available and are designed to minimize any damage to downstream resources