WSPC04476

• File Number: 8283.200
• Description: Colorado River Basin-Colorado River Computer Models-Colorado River Decision Support System-RAY
• State: CO
• Water Division: 5
• Date: 12/29/1993
• Title: Hydrosphere-Colorado River Model-Technical Overview
• Water Supply Pro - Doc Type: Report/Study

I
I
I
I
I
I
I
J
*
I
'I
I
I
I
I
I
I
I
I

002097

Hydrosphere's Colorado River Model

December 29, 1993
. Page 4

PHYSICAL SYSTEM DESCRIPTION

The Colorado River basin drains approximately 243,000 square miles contained within
the states of Colorado, Wyoming, Utah, New Mexico, Nevada, Arizona, California, and parts
of the Mexican states of Baja, California and Sonora. The river is highly regulated by a total
reservoir storage capacity approximately equal to four times the river's average annual flow.
Figure I shows the geographical extent of the Colorado River basin, the major rivers in the
basin as well as the major reservoirs and diversion structures.

The Colorado River basin is divided both geographically and politically at Lee Ferry.
just downstream of the point where the river crosses the Arizona-Utah border. The Upper
Basin includes lands in the states of Colorado, New Mexico, Utah, Wyoming, and a small part
of Arizona and is the principal source of inflow into the Colorado River system. The Lower
Basin includes lands in the states of Arizona, California, Nevada and New Mexico. A lesser
amount of inflow occurs in the Lower Basin, principally via the Little Colorado, Virgin, Bill
Williams and Gila Rivers.

The natural flows in the basin are highly irregular in occurrence. While the virgin flow
at Lee Ferry has averaged 15.1 million acre-feet annually over its measured period of record,
annual flows in excess of 23 million acre-feet (mat) and less than 7 maf have been recorded.
Over 70% of the annual virgin flow occurs in the months of May, June, and July. Flows have
been recorded for less than 100 years at most points on the river.

Many reservoirs alter the natural flow of the Colorado River. Fourteen of these
reservoirs are modeled in Hydrosphere's Colorado River Model, and they contain a total active
capacity of 61,375,000 acre-feet. The two principal reservoirs, Lakes Powell and Mead
(formed by Glen Canyon and Hoover Dams, respectively), provide over 50 maf of storage.
The other 12 reservoirs are Fontenelle, Flaming Gorge, Starvation, Taylor Park, Blue Mesa,
Morrow Point, Crystal, Ridgway, McPhee, Navaho, Mohave, and Havasu.

Water is diverted from the river at hundreds of relatively small diversion points in the Upper
Basin, The Lower Basin diversions tend to be larger and considerably fewer in number.
Major diversion structures in the Lower Basin include the Colorado River Aqueduct which
delivers water to the Los Angeles basin, the Havasu Pumping Plant/Central Arizona Project
Canal which supplies the Central Arizona Project, the Colorado River Indian Reservation Main
Canal in Arizona's Parker Valley, the Palo Verde Canal which diverts water to the Palo Verde
Irrigation District of California, the All American Canal System bringing water to the Imperial
and Coachella Valleys of California and the Yuma Project in California and Arizona, and the
Gila Main Gravity Canal which serves the Gila project in Arizona. Below the international
boundary, Morelos Dam diverts water for irrigation in Sonora, Mexico.

The Colorado River is already one of the most fully developed in the world. However,
additional storage and diversion projects are being planned and actively pursued throughout the
basin. The U. S. Department of Interior, Bureau of Reclamation, as the principal entity
responsible for operation and administration of the river, maintains a list of future water supply
projects and their depletions anticipated for implementation in each of the basin states. Current
water development plans of the individual states generally anticipate full development of their
legal entitlements by the year 2040.

Hydrosphere Resource Consultants tOO2 Walnut Suite 200 Boulder, Colorado 80302