7285

• UCREFRP Catalog Number: 7285
• Author: Stewart, J. M.
• Title: Summary of Water-Resources Activities of the U.S. Geological Survey in Colorado, Fiscal Year 1987.
• USFW Year: 1987.
• USFW - Doc Type: Open-File Report 87-388,
• Copyright Material: NO

PROJECT TITLE:

Hydrology of the Closed Basin
Project Area, San Luis Valley,
Colorado

STUDY LOCATION:

Upper San Luis Valley in Saguache,
Rio Grande, and Alamosa Counties

PROJECT NUMBER:

CO-81-146

COOPERATING AGENCY:

U.S. Bureau of Reclamation

PROJECT CHIEF AND
OFFICE:

Kenneth R. Watts, Subdistrict Office, Pueblo

PROJECT DURATION:

October 1980 to September 1987

PROBLEM: The Closed Basin project area is an internally drained part of the
Closed Basin, that is separated from the Rio Grande drainage in the Upper
San Luis Valley. Significant quantities of water, now lost to evapotran-
spiration, could be salvaged and used for agriculture, and(or) used to
partially fulfill Colorado's obligations to the Rio Grande Compact.

OBJECTIVES: Describe and evaluate quantitatively the hydrology of the project
area. Construct and interrogate digital models to evaluate the effect of
a lternat i ve 1 ocat ions of we 11 s and pump i ng patterns on ground water 1 n
the unconfined aquifer and confined zone.

APPROACH: Compile and evaluate existing data on wells, pumpage, vegetation,
and ground-water and surface-water i nfl ow to quantify the hydro 1 ogi c
budget. Drill test holes to define hydraulic gradients, geology, hydro-
geology, and water quality. Build and interrogate a two-dimensional
finite-difference model to estimate well spacing and pumping patterns
that woul d keep drawdown in the unconfi ned aquifer 1 ess than 2 feet at
the project-area boundary.

PROGRESS: A two-dimensional model of ground-water flow previously developed
to evaluate the potential effects of the Closed Basin Project was revised
to use the McDonald-Hirbaugh modules-code. All sensitivity tests and
simulations were rerun, using the modular-model source code, and the
results were compared to those from the two-D Trescott model. The inter-
pretive report was revised. Compilation of water-level data for the San
Luis Valley was begun.

PLANS FOR FY 87: A data report will be completed summarizing ground-water
data for the San Luis Valley. Operation of approximately 50 continuous-
recording wells will be continued near the perimeter of the Closed Basin
Project.

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