Hydrogeologic trends in the Dell City area, Hudspeth County, Texas

Abstract

—The Dell City irrigation district lies on the western edge of the Salt Basin in Texas and New Mexico. Extensive irrigation began in the 1950s and the area has been a prolific producer of cotton, alfalfa, melons, onions and garlic. Ground water for irrigation is pumped from underlying Permian carbonates (Bone Spring and Victorio Peak formations). Comparison of data from May 1992 with those of the late 1940s and 1960 shows an average 30-foot drop in the potentiometric surface, but hydraulic gradients in the aquifer are very small. The water table is nearly horizontal and pumping discharge is high, which indicates very high transmissivities, and there is a subtle east-west trough just south of Dell City. There are indications of local recharge within the irrigation area. The distributions of total dissolved solids (TDS) show an unexpected rise in the center of the irrigation district. TDS concentrations decrease radially, until they rise sharply again near the salt flats. This indicates that there has been little salt-water intrusion. The higher TDS near Dell City may be caused by irrigation return flow and a greater proportion of evaporite minerals in shallow sediments within a paleotopographic low. We suggest that the flow system is strongly fault-controlled. This has minimized salt-water intrusion by juxtaposition of hydrostratigraphic units and may control effective recharge areas.