WMOD00301

• Title: Precipitation Pattern Analysis - Uinta Baisn - Wasatch Front
• Date: 10/1/1990
• State: UT
• Weather Modification - Doc Type: Report

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Introduction

This study was conducted in agreement with the Division of Water Resources, State of Utah. For
several years Utah has maintained an active precipitation augmentation program that operates
during the winter months. The intent of the program is to increase precipitation in the Wasatch
Mountains and increase water harvest. There is concern in the Uinta Basin that precipitation
augmentation in the Wasatch Mountains is depleting the Eastern Utah moisture source.

To address these concerns this study presents Utah in her Western United States climate setting,
noting effects of terrain; average annual precipitation amounts and comparisons; historical and
present drought relationships; storm types; precipitation station correlations; and orographic model
results. In each of these topics we address the general western setting and then the very specific
setting of the Uinta Basin.

Utah Climatic Setting

Utah is located about 500 miles inland from the Pacific Ocean. The State is a land of high
mountains, elevated plateaus and deserts. Elevations in the State vary from near 2,350 feet in the
southwest corner of Utah to 13,528 feet at Kings Peak in the Uinta Mountains. The Wasatch Range
extends some two hundred miles from the northern border to Nephi ill central Utah, and has several
peaks in excess of 10,000 feet. The Uinta Mountains reach about 150 miles east from the Wasatch
Mountains to the Colorado border with several peaks in excess of 12,000 feet.

South and east of the Wasatch and Uinta Mountains lie the Colorado Plateaus. The High Plateaus,
the western portion of the Colorado Plateaus, extend southward from Nephi into Arizona and are
about 40 miles across, with summits reaching elevations in excess of 11,000 feet. South of the Uinta
Mountains lie the Tavaputs Plateaus and the great Canyonlands of the Colorado with elevations of
8,000 to 10,000 feet.

The Uinta Basin, except for the narrow Green River Canyon, resembles the Basin of an ancient sea
or lake and is surrounded by the Uinta Mountains on the north, the Wasatch Mountains on the West
and the high Colorado Plateaus on the south and east.

Although the Utah climate is classified as semiarid, there are enormous differences between the
alpine climates of the Uinta Mountains and the desert climate in the Uinta Basin. Annual
precipitation varies from over 40 inches in the high elevations of the Uintas to less than 6 inches
near Ouray. The unique setting of the Uinta Basin, surrounded by mountainous terrain, is aptly
shown on the satellite view of Utah in Figure 1.

The mountains and high plateaus (Figure 2) have a great influence upon the distribution of
precipitation in Utah. This is shown on the annual normal precipitation map in Figure 3. Utah's
Climatic Divisions are shown in Figure 4.

Annual normal precipitation by climatic division tabulated in Table 1 shows annual values for the
Uinta Basin Division are lower than any other division in Utah. Differences in the 30-year averages
reflect the droughts of the 1930's and 1970's.