WSP01172

• File Number: 822.600.10
• Description: Colorado River Annual Operating Plan - Annual Reports
• Basin: Colorado Mainstem
• Date: 1/1/1997
• Author: USDOI/BOR
• Title: Annual Operating Plan
• Water Supply Pro - Doc Type: Annual Report

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reservoir conditions to accomplish the objectives of the Beach/Habitat Building Flow
described in the GCDEIS. Such releases would be consistent with the 1956 Colorado River
Storage Project Act, the 1968 Colorado River Basin Project Act and the 1992 Grand Canyon
Protection Act. Such releases would be managed to the maximum extent possible to (1)
protect river sediment storage downstream or (2) be released in such a way as to reshape
. river topography, redeposit sediment.and enhance aquatic habitat. Pending completion of
NEP A compliance, Reclamation also intends to reinstall the spillway gate extensions at Glen
Canyon Dam to increase the flexibility of managing high runoff years.

During water year 1997, releases greater than the minimum release objective of
10,152 MCM (8.230 MAP) likely will be made to equalize the storage between Lakes Powell
and Mead and/or to avoid anticipated spills. Under the most probable inflow conditions,
releases of 12,261 MCM (9.940 MAP) would be made and the reservoir would gain 588
MCM (0.477 MAP) of storage. Under the probable maximum inflow scenario,
approximately 18,872 MCM (15.300 MAF) will be released during the water year and Lake
Powell would gain 2,026 MCM (1.643 MAP) of storage. This maximum probable inflow
would require releases of about 708 ems (25,000 cfs) for a lengthy period of time.

A Record of Decision on the GCDElS was signed by the Secretary of the Interior, resulting
in the following restrictions on hourly and daily operations.

abl

T e3. Glen Canvon Dam ooeratml!: restnctions
Parameter . (ems) (cfs) conditions
Maximum flow (1) 566.4 25,000
Minimum flow 141.6 5,000 nighttime
226.6 8,000 7:00 am to
7:00 pm
Ramp rates
ascending 70.8 4,000 per hour
descending 42.5 1,500 per hour
Dailv fluctuations (2) 141.6/226.6 5 000 to 8 000

(1) to be evaluated and potentially increased as necessary and in years when delivery to the
Lower Basin exceeds 10,152 MCM (8.23 MAF)

(2) Daily fluctuations limit is 141.6 cms (5,000 cfs) for months with release volumes less
than 740 MCM (.600 MAF); 169.9 ems (6,000 cfs) for monthly release volumes of 740
to. 987 MCM (.600 to .800 MAF); and 226.6 cms (8,000 cfs) for monthly volumes over
990 MCM (.800 MAF)

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