Edwards Aquifer Supply Management Using Aquifer Storage and Recovery

James C. Dwyer¹ and Grant L. Snyder^2
1 CH2M HILL, Austin, Texas
² URS Corporation, San Antonio, Texas

The Edwards Aquifer of the Balcones Fault Zone is the primary source of water for the greater San Antonio population. The Edwards Aquifer Authority is preparing a programmed reduction in water withdrawal as part of its plan to protect endangered species that rely on Comal and San Marcos Spring flows. Reductions would limit the System’s service operations during periods of normal precipitation and significantly reduce withdrawals during drought. Aquifer water rights are being leased and purchased for short-term augmentation.

Strategies are being implemented or under study for replacement of sources no longer available. The aquifer storage and recovery plan involves managing withdrawals to achieve full permit utilization while minimizing impact on seasonal high spring flow. The aquifer would be produced at a rate exceeding current demands. The excess would be stored in the confined Carrizo-Wilcox Aquifer, southern Bexar County, and recovered later for peak demand periods or to augment curtailed supplies during drought. Benefits include a 25-percent reduction in peak summer withdrawals, no evaporative losses or environmental impacts, and more complete utilization of the Aquifer.

Startup for the storage and recovery system is early 2004. Phase I construction includes a 30 million gallons per day well field, treatment plant, high-service pump station, and 27 miles of distribution pipeline. Phase II adds 11 additional wells and increase the capacity of the project to 64 million gallons per day. Innovations are geophysical logging, pre-packed well screens, reverse-flow well pumps and piping, and a comparison of two popular down-hole control valves.

AAPG Search and Discovery Article #90032©2004 GCAGS 54th Annual Convention, San Antonio, Texas, October 10-12, 2004