The Antlers Sandstone of Early Cretaceous age occurs in all or parts of Atoka, Bryan, Carter, Choctaw, Johnston, Love, Marshall, McCurtain, and Pushmataha Counties, a 4,400-square-mile area in southeastern Oklahoma parallel to the Red River. The sandstone comprising the Antlers aquifer is exposed in the northern one-third of the area, and ground water in the outcrop area is unconfined. Younger Cretaceous rocks overlie the Antlers in the southern two thirds of the study area where the aquifer is confined. The Antlers extends in the subsurface south into Texas where it underlies all or parts of Bowie, Cooke, Fannin, Grayson, Lamar, and Red River Counties. An area of approximately 5,400 square miles in Texas is included in the study.
The Antlers Sandstone consists of sand, clay, conglomerate, and limestone deposited on an erosional surface of Paleozoic rocks. Saturated thickness in the Antlers ranges from 0 feet at the updip limit to probably more than 2,000 feet, 25 to 30 miles south of the Red River.
Simulated recharge to the Antlers based on model calibration ranges from 0.32 to about 0.96 inch per year. Base flow increases where streams cross the Antlers outcrop, indicating that the aquifer supplies much of the base flow.
Pumpage rates for 1980 in excess of 35 million gallons per year per grid cell for public supply, irrigation, and industrial uses total 872 million gallons in the Oklahoma part of the Antlers and 5,228 million gallons in the Texas part of the Antlers.
Ground-water flow in the Antlers aquifer was simulated using one active layer in a three-dimensional finite-difference mathematical model. Simulated aquifer hydraulic conductivity values range from 0.87 to 3.75 feet per day. A vertical hydraulic conductivity of 1.5x10-4 foot per day was specified for the younger confining unit at the start of the simulation. An average storage coefficient of 0.0005 was specified for the confined part of the aquifer; a specific yield of 0.17 was specified for the unconfined part.
Because pumping from the Antlers is minimal, calibration under transient conditions was not possible. Consequently, the head changes resulting from projection simulations in this study are estimates only. Volumetric results of the six projection simulations from the years 1990 to 2040 indicate that the decrease in the volume of ground water in storage due to pumping approximately 9,700,000 acre-feet from 1970 to 2040 is less than 0.1 percent.