WMOD00314

• Project Name: Uintah Ecology Project
• Title: Potential Ecological Impacts of Snowpack Augmentation in the Uintah Mountains, Utah
• Date: 4/20/1981
• State: UT
• Weather Modification - Doc Type: Report

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17

ABSTRACT

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Only a small area on the headwaters of the Weber and Provo Rivers

received over 102 cm (40 in) of precipitation during the 1973-78 period.
Longer term records confirm that conclusion for the entire Uinta Moun-
tains. Throughout the range, most (> 75%) of the water-year precipi-
tation comes during the October-June period. Winter precipitation is
far more reliable than summer precipitation. The north and west sides
. ;~
of the range receive 16-18% more precipitation than the south and east

sides. On the average, precipitation shows an increase of about 7.6 cm

per 305 m (3.0 in/IOOO ft.) increase in elevation in the Uintas.

Surface runoff water is almost wholly attributable to cool season

(October-June) precipitation. Although April 1 snowpack accounts for less

than half of the cool season precipitation, that snowpack accounts for over

96% of the year-to-year variation in streamflow. Our runoff model predicts

that a 10% increase in the average April 1st snowpack will elevate stream-

flows 13% above average.

Multiple regression analysis shows that streamflow can be expected

to decrease 4.8% if all the deciduous forests on the west end of the

Uintas are permitted to be displaced by coniferous forests through

natural succession. Removal of forest cover and replacement with her-

baceous vegetation should increase streamflow significantly. For max-

imum increases in streamflow, weather modification must be accompanied

by vegetation management programs that preserve deciduous forests at the

expense of conifers and herblands at the expense of forests.

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