A Statistical Study of the Hydrological Character of the Edwards Aquifer

The Edwards Aquifer is located in south-central Texas with a length of about 180 miles, and varying width from 5 to 40 miles. It is one of the most permeable and productive artesian limestone aquifers in the United States and supplies drinking water to more than 1.5 million people in San Antonio and the Austin-San Antonio corridor. Water from the aquifer is vital to the agricultural and light industrial economy of the region. Discharge from the aquifer provides water to many springs in the area, including two large springs, San Marocs and Comal Springs. Flows from the these springs provide water for the tourist and recreation industry, critical habitat for several endangered species and appropriated water use downstream for the Gulf Coastal Plain and the San Antonio Bay ecosystem. A major storm occurred in south-central Texas on October 17, 1998, through October 19, 1998 with most of the precipitation falling within the first 24 hours. The storm had two main centers of rainfall; one with 30 inches of rainfall and a second with about 22 inches of rainfall. This storm provided a unique stress on the Edwards Aquifer that allowed us to study the correlation between the surface water and groundwater systems and infer information about recharge, storage, and flow in the Aquifer. The study found that the initial response of river and stream flow to the precipitation event was very rapid and produced sharp peaks in flow with fast recession curves. Well and spring response was slower, with the well response times significantly longer than those of the springs. The data shows interesting correlations between the surface and ground water systems that are indicative of aquifer characteristics and help provide insight for future management decisions.