8045

• UCREFRP Catalog Number: 8045
• Author: Pacey, C. A. and P. C. Marsh.
• Title: Resource Use by Native and Non-Native Fishes of the Lower Colorado River
• USFW Year: 1998.
• USFW - Doc Type: Literature Review, Summary, and Assessment of Relative Roles of Biotic and Abiotic Factors in Management of an Imperiled Indigenous Ichthyofauna-Final Report.
• Copyright Material: NO

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Other structures downstream from Parker Dam mostly were constructed as points of
diversion to accommodate agricultural uses along the floodplain.and adjacent uplands.
Included are Headgate Rock (Squaw) Diversion Dam (River Kilometer [RK] 285,
measured upstream from the Southerly International Boundary of United States and
Mexico), Palo Verde Irrigation Diversion (RK 214), Imperial Dam (RK 78), Laguna Darn
(RK 70) and Morelos Dam (RK 35). Headgate Rock diverts water into Colorado River
Indian Tribes (CRIT) canals, and backs up a short (less than a kilometer), shallow area
known as Moovalya Lake. Palo Verde Dam diverts water to California agriculture in the
Blythe area. Imperial Dam serves as intake point for the Gila Gravity Main Canal,
which waters Arizona agriculture in the Yuma area, and for the All American Canal,
which serves the Coachella and Imperial valleys of California. Imperial Reservoir is
shallow and only a few kilometers long, and acts as a sediment settling basin for canal
intakes. Laguna Dam, built in 1906 as the first structure to interdict the lower Colorado
River, is no longer in service. Finally, Morelos Dam distributes water into Mexican
canals in an amount determined by Treaty Agreements. Except in wet years, the
discharge is nil in the Colorado River below Morelos Dam and sometimes no water
passes over the river delta to its mouth at the Gulf of California (Sea of Cortez).
River Reaches -- River reaches along the lower Colorado River all are tailwaters below
dams and free-flowing streams above impoundments. Inflows to these reaches are the
river itself, augmented seasonally by irrigation returns and sporadically by runoff from
adjacent watersheds during heavy precipitation. The Gila River, which drains a
substantial proportion of central Arizona and part of southwestern New Mexico, enters
the Colorado River near RK 54 at Yuma. The Gila itself is highly regulated, and except
during floods, flow in its lower reaches is comprised of irrigation returns, or absent.
Withdrawals of Colorado River water from riverine reaches mostly are minor to irrigate
local agriculture or supply domestic needs.