WMOD00414

• Title: Water and Choice in the Colorado River Basin
• Date: 5/1/1968
• Weather Modification - Doc Type: Report

CHAPTER TWO

The Setting

AN ARID DRAINAGE BASIN

The Colorado River system is the largest in the United States that flows mainly
in arid country through lands having chronic water deficiency for cultivation
of crops. Except in the high mountains where there is a water surplus, irrigation
is necessary for regular crop growth.
The river is 1,440 miles long and drains a basin 244,000 square miles in
area, including parts of seven states and a piece of Mexico (see location map
on page xi). Arizona is almost entirely within the basin; about half of Utah
and half of Colorado are included. Although the Colorado is long and drains a
large basin, it is small in flow (Figure 1). Despite its small flow, the Colorado
exports water to other basins (Figure 2). Indeed, more water is diverted from
the Colorado basin than from any other river basin in the United States;
present and anticipated out-of-basin diversions total more than 5.2 million
acre-feet* annually, of a total virgin flow t of perhaps 15 million acre-feet
(mat).
The landscape of the basin is colorful and angular, lacking the softened
contours of more humid regions. Broadly speaking, it is the result of differ-
ential uplift and erosion of segments of the earth's crust, segments that are
broad and horizontal in the upper basin but narrow and tilted in most of
the lower basin.

* An acre-foot is the amount of water required to cover one acre to a depth of one
foot, approximately 326,000 gallons.
t Virgin flow is the measured flow plus an estimate of net man-induced depletions
upstream.

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