Post-Pleistocene patterns of shallow groundwater flow in the Delaware Basin, southeastern New Mexico and west Texas

Abstract

_____ We used a numerical model to evaluate factors potentially affecting ground water flow in the Rustler and Dewey Lake Formations within a northern portion of the Delaware Basin. The model, which is based on the concept of the ground water basin, suggests that flow patterns respond significantly to changes in climate. We include the effects of climate change in the model by varying the amount of moisture that infiltrates to the saturated zone. Calculated hydraulic heads in confined units, such as the Culebra Dolomite Member of the Rustler Formation, change by as much as tens of meters in response to long-term changes in the infiltration rate. Results support the concept that patterns of ground water flow in confined units are strongly influenced by the relief of the overlying water table. A substantial portion of the water flowing in the confined units is derived from slow vertical leakage through underlying and overlying aquitards. Flow rates and directions at depth can apparently be affected by changes of only a few tenths of a millimeter per year in the rate of infiltration to the saturated zone. During the simulated period of time, reversals in the direction of vertical flow through the aquitards occur over extensive areas of the model domain. There is great uncertainty in many of the parameters used in our calculations. We do not, therefore, claim that these results are quantitatively correct. Instead, these results improve our intuitive understanding of regional ground water flow in the shallow portion of the Delaware Basin.