Technical Reports Document Library

During fiscal year 1971, hydrologic studies of the aquifer system formed by the Edwards and associated limestones in the San Antonio area, Texas, were directed toward development of hydrochemical techniques, evaluation of geophysical-logging methods, and applications of tracer studies.

These preliminary investigations indicate that hydrochemical data, such as the tritium content and the ratios of different isotopes of carbon and sulfur, may be useful in determining the general direction of ground-water movement and the age of the water in storage.

The evaluation of geophysical-logging methods indicate that electrical, neutron, temperature, gamma, gamma gamma, and caliper logs will be useful in determining the physical characteristics of the aquifer.

Preliminary application of tracer methods, including point-dilution tests, single-well pulse tests, and transit-time tests indicate that-tracer studies may provide data on interstitial velocity and porosity of the aquifer.

Plans for the program during the 1972 fiscal year include additional hydrochemical studies, additional geophysical logging, water-level measurements in about 300 observation wells, and compilation and analyses of data on well yields, aquifer characteristics, recharge, streamflow, and precipitation.