WMOD00575

• Title: Suitability of the Upper Colorado River Basin for Precipitation Management
• Date: 10/1/1969
• Weather Modification - Doc Type: Report

of Colorado; by the Green River originating in Wyoming
and flowing into the Colorado River in southern Utah;
by the San Juan River originating in southern Colorado,
flowing through northern New Mexico and joining the
Colorado River in southern Utah. In the northern por-
tion of the basin, there are hundreds of peaks of more
than 13,000 feet in elevation. A highly smoothed topog-
raphy of the basin is shown in Fig. 2.

In high mountain regions, much of the annual run-
off occurs as a result of melting snow. Hence, runoff
is often characterized by a peak flood.season in late
spring followed by low water flow in summer, fall, and
winter. This holds true for the Colorado River and its
tributaries [2].

The annual virgin runoff at Lees Ferry, Arizona,
is noted for its large fluctuation, as shown in Fig. 3.
Virgin runoff is that runoff which takes place without
the interference of man. Virgin runoff is reconstructed
from the actual flow, from data on transmountain diver-
sions, on regulation by dams~ and from estimates of
irrigation diversions and uses. The fluctuation of
annual virgin runoff ranges from a low of 1.08 inches
to a high of 4.10, as measured in the last 51 years [9].

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Percent 0 f the

Are a 0 f the Upper
Colorado River Basin

Elev, >11 11-88-5 <5
ange
% 3 24 63 10

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2. Precipitation management in the Upper Colorado
River Basin. The precipitation management project,
currently planned by the United States Bureau of
Reclamation, Office of Atmospheric Water Resources,
concerns winter cloud seeding operations above certain
high elevation watersheds of the Upper Colorado River
Basin. The precipitation due to cloud seeding which
falls as snow in winter, is expected to increase the
runoff in spring.

The following characteristics of the Upper
Colorado River Basin are favorable for weather modifi-
cation:

(a) High mountain ranges in this region are
favorable for orographic precipitation and in addition,
, the northwest wind brings large supplies of moisture in
winter [10].

(b) Water from snowmelt in early spring through
early summer can be stored and made available when
needed for various kinds of use.

Figures 4 and 5 illustrate the typical variation
of precipitation and runoff in this region. The dis-
tribution of monthly precipitation is, on the average,

N

I

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Fig. 2 The highly smoothed topography of the Upper Colorado River Basin
(in units of 1000's of feet). (After Rasmussen, J.L. [8])

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