WSP04162

• File Number: 8200.750
• Description: San Juan River General
• State: CO
• Basin: San Juan/Dolores
• Water Division: 7
• Date: 6/1/1987
• Author: Wheeler and Assoc
• Title: Documentation for McElmo Creek Hydrology Analysis - Historic and Virgin Flow Conditions - June 1987
• Water Supply Pro - Doc Type: Report/Study

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PART IV. McELMO CREEK DRAINAGE BASIN

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McElmo Creek drains a 346 square mile area as measured at the Colorado-

Utah state line. Elevations within the drainage basin range from 4900 feet

at the state line to about 7000 feet in the eastern areas of the drainage basin.

Ute Peak, located on the southwestern boundary of the drainage basin, extends

to an elevation of 10,000 feet, but the area of the mountain above 8000 feet

in the drainage basin is limited to only about 1.5 square miles.

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Precipitation varies from less than ten inches per year at the state line

to 18 inches at the eastern end of the basin, based on data from the map entitled

"Colorado Average Annual Precipitation 1951-80," published by the U.S. Geologi-

cal Survey (Scale 1:500,000). Local annual precipitation near the summit of

Ute Peak may be 20 to 25 inches. Isohyetals of mean annual precipitation are

shown on Figure 2.

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The town of Cortez is located within the McElmo Creek drainage basin.

A summary of census figures for Cortez is presented below:

. Year Population
1950 2,680
1960 6,764
1970 6,032
1980 7,095
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The northern and eastern portions of the McElmo Creek drainage basin

include much of the area known as the Montezuma Valley, which is dominated

by irrigated fannland. Native vegetation throughout the basin varies with eleva-

tion and soils. Pinon and juniper is scattered throughout the area, interspersed

with sagebrush. A distinct zone of riparian vegetation exists along McElmo

Creek and its major tributaries, consisting of cottonwood and box elder trees,

salt cedar, willows, and other brush.

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