WSP05903

• File Number: 8583
• Description: Rio Grande Decision Support System
• State: CO
• Basin: Rio Grande
• Water Division: 3
• Date: 2/1/1998
• Author: Dr. John W. Hernande
• Title: Evaluation Of Salvage Well Production Problems In The Closed Basin Of The San Luis Valley Colorado
• Water Supply Pro - Doc Type: Report/Study

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001 G'J I.)

The almost 3,000 square-mile "Closed Basin" takes it name from the condition that none

of the surface runoff entering the basin discharges into the nearby Rio Grande, The creeks and

streams that are tributary to the Closed Basin are the following (starting from creeks draining the

eastern slopes of the Sangre de Cristos at the southern end of the Basin and going in a counter-

clockwise direction ending at the northwest rim): Zapata, Mederano, Sand, Deadman, Cotton-

wood, Spanish, Willow, Crestone, Rita Alto, Wild Cherry, Cotton, San Luis Creek (due north),

Kerber, Saguache, and Camero and La Garita (from the west), Not all of these streams discharge

directly into the Closed Basin, There are a number of small lakes in the Basin, where the surface

flows from these streams collect. The largest of these lakes or sumps is San Luis Lake about 15

miles north and east of Alamosa, Others include Head and Dollar lakes near San Luis Lake, and

Dry Lakes seven miles south, Valley lakes located outside the Basin are Mishak, and Russell

located 15 to 20 miles north and west of San Luis Lake, Springs are found around the rim of the

basin in the foothills where alluvial fans have formed, Typical elevations at the rim of the valley

are 7600 to 7650 feet. Elevation of the valley floor range from 7520 near San Luis Lake to 7555

near Hooper on the railroad 20 miles to the north of Alamosa (elevation 7536),

The San Luis Valley is underlain by a shallow, unconfined aquifer in a fill that is

typically 90 to 100 feet thick. This water-table aquifer is made up of alternating layers, and

mixtures, offine sands and clays in the Closed Basin area, There are occasional thin zones of

sandy gravel. The depth to water in the shallow aquifer is typically about 10 feet, and the water-

table slopes from the west, north, and east into the trough of the Basin much like the land

surface, A thick layer of blue clay separates the unconfined zone from a series oflower confined

aquifers, The two aquifers are connected in a common recharge area along the eastern and

northern rim of the Basin, by upward leakage, and through wells that are open in both zones,

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