From Bureau of Economic Geology, The University of Texas at Austin (
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Bureau Seminar, November 16, 2012

Potential Economic Impacts of Instream Flows for Central Texas Freshwater Mussels

Link to streaming video: available 11.16.2012 at 8:55am

Dr. Brad Wolaver
Research Associate, Bureau of Economic Geology

Texas water resources already taxed by drought are becoming more important as population grows. Environmental flows (EF) for aquatic habitat preservation could further reduce supplies if five Central Texas freshwater unionid mussel species are listed as endangered. This study estimates potential economic impacts water shortages induced by EF for mussels in Brazos, Colorado, and Guadalupe-San Antonio River basins (36% Texas area,~95,000 square miles). Water supply reductions for EFs were simulated with Water Availability Model, aggregated by county, and categorized by: (1) Steam electric, (2) Commercial and industrial, (3) Municipal, and (4) Agriculture. Counties were identified with surface water supply deficits and power plant cooling reservoir operating level frequency changes were calculated. Economic impacts were estimated with and without water transfers ("integrated market" and "segmented market"). EF- impacted counties already had supply issues. Reductions ranged from 3–33% to 13–67% of baseline stream flow under low and high EF scenarios (95% and 75% exceedances probabilities, respectively). Brazos River basin has no shortages. Colorado River basin shortages include Tom Green (55,000 acre-feet/year, af/yr) and Wharton Counties (82,000 af/yr) in worst-case. Groundwater imports reduce Bexar (74,000 af/yr) and Medina County (4,000 af/yr) Guadalupe-San Antonio River basin shortages to 8,000 af/yr. Bexar County power plant reservoir supply reductions cause economic impacts up to $107M if no water transfers occur. Non-power economic impacts can be almost entirely mitigated by water transfers, which reduce worst-case total losses from $37M to $1.6M. Establishing water markets (and also including conjunctive use of surface water and groundwater, aquifer storage and recovery, interbasin transfers, and conservation) should mitigate most economic impacts if mussels are listed. In light of Texas' water supply challenges, approaches need to be developed for environmental flows and to have a broad range of strategies to decrease any economic impacts related to flow reductions.