ABSTRACT

Three federally-listed endangered species at Comal and San Marcos Springs of central Texas are dependent upon springflows which issue from the Edwards aquifer. Historic drought conditions can lower discharge rates beneath the levels specified by federal regulations. Projected and existing rates of withdrawals from the Edwards aquifer will exacerbate periods of low discharge from the springs. One option which has been proposed for aquifer management is the augmentation of springflows by one of several methods: injection wells, infiltration galleries, direct addition of water to the lake/river systems, or enhanced recharge of the Edwards aquifer. The feasibility of each method is based upon the local hydrogeological characteristics. Modeling of the injection wells and infiltration galleries calculates the efficiency of these two processes. The former depends upon proximity to the spring orifices and the subsurface permeability structure. The latter depends largely upon the vertical permeability of the Regional Dense Member of the Person Formation. Water-quality considerations for the fauna are not yet documented, but the Edwards aquifer is a compatible source. Augmentation is feasible from hydrogeological and technical standpoints and can be considered as part of a water resources management system.