The purpose of this study was to assess the status of data on recharge for the major aquifers in Texas to provide input to the Groundwater Availability Modeling program at the Texas Water Development Board, evaluate the reliability of the recharge estimates, develop conceptual models for recharge for each of the aquifers, review techniques for quantifying recharge, and recommend appropriate techniques for quantifying the recharge of each of the major aquifers.

Recharge rates for all major aquifers were compiled from published reports. The Edwards aquifer is the most dynamic, and recharge rates are highly variable spatially and temporally. Recharge is fairly accurately quantified using stream-gauge data. Estimates of recharge rates in the Carrizo-Wilcox aquifer range from 0.1 to 5.8 in/yr, with higher recharge in the sandy portions of the aquifer (i.e., the Carrizo and Simsboro Formations). Reported recharge rates for the Gulf Coast aquifer (0.0004 to 2 in/yr) are generally lower than those for the Carrizo-Wilcox aquifer.Regional recharge rates in the High Plains aquifer, outside irrigated areas, are generally low (0.004 to 1.7 in/yr), whereas playa-focused recharge rates are much higher (0.5 to 8.6 in/yr). Irrigated areas also have fairly high recharge rates (0.6 to 11 in/yr). Recharge rates in the Trinity and Edwards-Trinity Plateau aquifers generally range from 0.1 to 2 in/yr. The Seymour aquifer has recharge rates that range from 1 to 2.5 in/yr. Recharge rates for the Hueco-Mesilla Bolson and the Cenozoic Pecos Alluvium are represented as total recharge along mountain fronts and valley floors.

The main techniques that have been used for estimating recharge are Darcy's Law, groundwater modeling, base-flow discharge, and stream loss. Uncertainties in estimates based on Darcy's Law are considered high because of uncertainties in estimates of regional hydraulic conductivity. Recharge estimates based on groundwater model are not considered highly reliable because calibration based on hydraulic head data alone can only be used to estimate the ratio of recharge to hydraulic conductivity. This review of existing data indicates that additional studies are required to provide more quantitative estimates of recharge to the major aquifers.

Reference
Scanlon, B. R., Dutton, A. R., and Sophocleous, M. A., 2003, Groundwater Recharge in Texas: The University of Texas at Austin, Bureau of Economic Geology, Submitted to Texas Water Development Board. [PDF]