RECHARGE OF THE SOUTHERN SEGMENT OF THE CARRIZO-WILCOX AQUIFER

The southwest segment of the Tertiary-age Carrizo-Wilcox Aquifer spans from south-central Texas to near the Mexican border, a distance of approximately 100 km. During the past century, this segment of the Carrizo-Wilcox Aquifer has been over-pumped as demonstrated by the potentiomentric surface, which has been lowered in excess of 130 m. This dramatic lowering of water level in the aquifer has raised questions on rates and sources of recharge. Field studies, including geophysical surveys, evaluation of limited hydraulic information, and examination of existing water quality data, suggest that recharge in the study area occurs mostly as focused recharge associated with the Nueces and Leona river channels, with limited distributed recharge from precipitation or irrigated farm land. Measurement of the quantity of recharge, including recharge focused in river channels and distributed over the recharge zone, suggests that the rate of recharge is no greater than half the rate of water being pumped