WSP09796

• File Number: 8220.200.06.M
• Description: Imperial Dam
• Basin: Colorado Mainstem
• Date: 1/1/1981
• Author: USDOI/BOR
• Title: Regional Director's Report of Flows and Diversions at Imperial Dam and All Actions Affecting the Coordination Thereof - Calendar Year 1981
• Water Supply Pro - Doc Type: Annual Report

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1.

INTRODUCTION

Imperial Dam is located on the Colorado River 5 miles above Laguna Dam and
approximately 20 miles north of Yuma, ^rizona.

Construction of the dam and desilting works was started in 1935 and
completed in 1938 under the authorization of the Boulder Canyon Project Act
of 1928.

Imperial Dam is a slab and buttress type structure extending across the
Colorado River from the California to the Arizona shore. Its overall
length is 3,485 feet. The maximum height of the dam is 45 feet, and it
raises the normal water surface elevation of the river 23 feet. The
overflow weir section of the dam is 1,198 feet in length with an ogee
downstream slab. With open sluiceway gates, it is calculated that a flood
of 180,000 cubic feet per second (cfs) could be discharged with 6 feet of
freeboard remaining on the nonoverflow structure.

The principal purpose of Imperial Dam is to divert water from the
Colorado River to the All-American and Gila Gravity Main Canals. It
provides capabilities for diversion of 15,155 cfs to the All-American Canal
and 2,200 cfs to the Gila Gravity Main Canal. The storage capacity of the
reservoir above the dam is minor. The reservoir area now consists of a
shallow lake with channels to the All-American and Gila Headworks.
Operation of Imperial Dam is coordinated with operation of Laguna Dam and
Senator Wash Regulating Reservoir to obtain the optimum use of available
riverflow.

On May 1, 1952, in accordance with provisions of the Contract Amendatory of
and Supplemental to the All-American Canal Contract dated December I, 1932
(Contract No. Ilr-747, Supplemental), the care, operation, and maintenance
of the headworks and desilting basins of the All-American Canal, the
All-American Canal from Imperial Dam to and including Pilot Knob Wasteway,
the Coache1la Canal to 6A Check (Station 2602+60), the Government Camp and
buildings, and appurtenances necessary to the operation of these facilities
were transferred to the Imperial Irrigation District (District).

Secretarial Order 2685. which has been superseded by authorization
contained in paragraph No.2 of the Assistant Commissioner's letter to the
Regional Director, Boulder City, Nevada, subject: "Imperial Dam Flows and
Diversions," dated October 27, 1965, provides that a report summarizing the
monthly and special reports and expenditures by the United States for
performance of functions delegated by the Secretary of the Interior for the
preceding calendar year be submitted not later than February 1.

This "Report of Flows and Diversions at Imperial Dam and All Actions
Affecting the Coordination Thereof" for calendar year 1981 summarizes the
following.

1. Flows and diversions at the principal points listed on the Master
Schedule of Flows and Diversions at Imperial Dam.