WSP12637

• File Number: 8282.300
• Description: Colorado River Operations and Accounting - Lower Basin Administrative Procedures
• State: CO
• Basin: Colorado Mainstem
• Water Division: 5
• Date: 8/1/1996
• Author: DOI-BOR
• Title: Description and Assessment of Operations-Maintenance and Sensitive Species of the Lower Colorado River - Volume I - Report - 08-01-96
• Water Supply Pro - Doc Type: Report/Study

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002343

1.218 maf of flood storage is above elevation 1221.4, which is the top of the raised spillway
gates.

Flood Control regulations specify that once flood releases exceed 40,000 cfs, the releases
shall be maintained at the highest rate until the reservoir drops to elevation 1221.4 ms!.
Releases may then be gradually reduced to 40,000 cfs until the prescribed seasonal storage
space is available.

The flood control regulations set forth two primary criteria to deal with snowmelt:
1) preparatory reservoir space requirements, and 2) application of runoff forecasts to
determine releases.

In preparation for the coming year's season of snow accumulation and associated runoff,
progressive expansion bf total Colorado River system reservoir space is required during the
latter half of each year. Minimum available flood control space increases from 1.5 J.Tlaf on
August 1 to 5.35 maf on January 1. Required flood storage space can be located within
Lake Mead and in specified upstream projects: Lakes Powell and Navajo, and Blue Mesa,
Flaming Gorge and Fontenelle Reservoirs. Minimum Lake Mead space required for
exclusive flood control is 1.5 maf. The following chart shows the amount of required flood
storage space by date: .

Minimum Required System Space

Date

Amount in acre-feet

August 1
September 1
October 1
November 1
December 1
January 1

1,500,000
2,270,000
3,040,000
3,810,000
4,580,000
5,350,000

Normal space-building releases from Lake Mead to meet the required August 1 to
January 1 flood control space are limited to a maximum of 28,000 cfs. Releases based on
the water entitlement holders' demand are much less than 28,000 cfs.

Between January 1 and July 31, flood releases, based on forecasted inflow, may be required
to prevent filling of ~e Mead beyond its 1.5 maf minimum space. Starting on January 1,
the Colorado River Forecasting Service issues runoff forecasts each month through July 31.
The release schedule contained in the COE regulations is based on increasing releases in six
steps (shown in the following chart):

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