Hydrogeological investigations at Diamond Y Springs and surrounding area, Pecos County, Texas

This study presents the results of local hydrogeologic investigations at Diamond Y Springs and vicinity, a 660 mi² (1710 km² ) area of north-central Pecos County, Texas. The data confirm the hypothesis of Rustler aquifer waters as the chief source of flow at Diamond Y Springs today. Dissolution of halite and gypsum, base exchange, evaporation, and mixing of the two hydrochemical facies of the Rustler with recent local waters can explain the water chemistry and isotopic composition. The main controls on the regional flow pattern are: (1) the permeability contrast between the Belding-Coyanosa trough fill and the Edwards Formation, (2) the amount of cross-formational flow recharging the Edwards-Trinity (Plateau) aquifer through the Belding fault system, (3) the amount of recharge from the Rustler aquifer, and (4) the amount of groundwater pumped in the Belding-Fort Stockton and Coyanosa irrigation districts.