Simulation of groundwater flow to assess the effects of groundwater pumping and canal lining in the Mesilla Basin of Dona Ana County, New Mexico and El Paso County, Texas

Abstract

In March 1991, after a decade of litigation over a proposal to pump water from within the state of New Mexico for transportation across state lines into Texas, a Settlement Agreement between the State of New Mexico and the City of El Paso, Texas was negotiated. From this agreement came the expressed desire for a computerized groundwater model capable of simulating interaction between the ground and surface water systems of the Mesilla Basin. The hydrologic repercussions of future pumping withdrawals and proposed irrigation canal lining were of particular concern to the parties of the Settlement Agreement. To meet these concerns, an existing and calibrated groundwater flow model was used to evaluate how these two activities will affect flows in the Rio Grande, flows in the irrigation drain system, water levels in the groundwater system, and water quality in both the surface and groundwater systems. The study involves 98 separate computer simulations: 7 altering future pumping rates, 2 altering canal lining, 5 manipulating the application of diverted surface water to farmlands, and 84 evaluating model sensitivity to selected input parameters. In addition to a detailed presentation of simulation results, this report briefly discusses the physical features of the basin and provides some historical background on water use in the study area. A special chapter is dedicated to discussions concerning surface water capture concepts and factors which influence ground and surface water quality in the basin.