USING SWAT-MODFLOW FOR ARID BASIN MODELING AND PREDICTION

This project investigated the local geologic and hydrogeologic aspects of Wild Horse Basin in order to develop a computer model that would simulate possible impacts from pumping. Wild Horse Basin consists of approximately 21,000 acres and lies 100 miles east of El Paso. It is part of the larger Salt Basin that extends southward from the Sierra Diablo Plateau. Arid basins common to southwestern Texas and surrounding states have been given little attention until the recent demand for their natural resources.

The city of El Paso, Texas, currently receives their water from the Hueco Bolson. Due to population growth and industrial expansion the availability of fresh water in the Hueco Bolson is in question. Problems associated with future over-production include encroachment of saline water from the north and east, accompanied by water level declines. SWAT output parameters were combined with VISUAL MODFLOW in order to develop an independent study of the basin. A transient model calibrated to pumping decline rates and water drawdown levels was developed and run for a 20-year period. Aquifer parameters, such recharge and rates of infiltration among the various soils were assessed from field data gathered by the Guelph Permeameter.

This integrated modeling approach provided visual groundwater-surface water interactions pertinent to aquifer replication. The SWAT-MODFLOW model was used for prediction and also to learn more about Wild Horse Basin, as little is presently known about its hydrogeology.