7388

• UCREFRP Catalog Number: 7388
• Author: Ohmart, R. D., B. W. Anderson and W. C. Hunter.
• Title: Ecology of the Lower Colorado River from Davis Dam to the Mexico-United States International Boundary
• USFW Year: 1988.
• USFW - Doc Type: A Community Profile.
• Copyright Material: NO

Parker and Imperial Dams operational
by 1938 and Davis Dam by 1951. River
management activities following con-
struction of these dams began to con-
trol the once wild and unpredictable
flows of the lower Colorado River.
These structures permanently changed
the character of the lower Colorado
River by ending the cycle of annual
flooding that had shaped the valley
over geological time.
With floods controlled and irriga-
tion water readily available, large
stands of natural habitat in the
floodplain areas of the lower Colorado
River were rapidly converted to agri-
cultural uses (Figure 15). Wide por-
tions of the floodplain near Yuma,
Blythe, Parker, and Needles were
cleared during the 1940's and 1950's.
During this period the Bureau of
Reclamation designed plans for vegeta-
tion removal to reduce evaporated
water losses, but private entities
removed vegetation for agricultural
development so quickly and extensively
that Federal designs were never imple-
mented. The on I y I arge tracts of
natural terrestrial vegetation remain-
ing on the lower Colorado River are
now on the five Indian Reservations
and the three National Wildlife
Refuges (Figure 1).
Native American communities soon
followed the lead of Anglo-Americans
in bowing to economic incentives by
developing their land for agriculture
during the 1960's and 1970's (Figure
16). Much of the Mohave Valley was
devoid of native vegetation by 1980,

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Figure 15. Alfalfa fields near Parker, AZ. Before conversion to agriculture,
honey mesquite was the dominant vegetation throughout the second terrace in
this valley, extending to the base of the distant mountains. Photo by W.C.
Hunter.
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