UPDATED EVALUATION FOR THE WILLIAMSON, BURNET AND NORTHERN TRAVIS COUNTIES PRIORITY GROUNDWATER MANAGEMENT STUDY AREA Prepared by Abiy K. Berehe, P.G. Water Rights Permitting and Availability Section Water Supply Division Priority Groundwater Management Area File Report November 2005 - page is intentionally blank - TABLE OF CONTENTS EXECUTIVE SUMMARY ............................................................ 1 INTRODUCTION ................................................................... 5 Purpose and Scope ............................................................ 5 Methodology and Acknowledgments .............................................. 5 Location, Climate, and Topography ............................................... 6 Surface Water Resources ....................................................... 7 GEOLOGY AND GROUNDWATER RESOURCES ....................................... 9 Edwards Aquifer ............................................................. 11 Trinity Group Aquifer ......................................................... 17 Minor Aquifers .............................................................. 25 Marble Falls Aquifer ................................................... 25 Ellenburger-San Saba Aquifer ............................................ 25 Hickory Aquifer ....................................................... 25 Other Groundwater Sources ............................................. 26 NATURAL RESOURCES ........................................................... 27 Texas Parks and Wildlife Department Regional Facilities ............................. 27 Springs, Wetlands, and Fishes .................................................. 27 Birds and Waterfowl .......................................................... 28 Amphibians, Reptiles, and Mammals ............................................. 28 Vegetation and Soil ........................................................... 29 Conservation Lands .......................................................... 29 WATER USE, DEMAND, SUPPLY AND AVAILABILITY ................................ 31 Water Usage ................................................................ 31 Population and Water Demand Projections ........................................ 33 Water Supply ............................................................... 38 Groundwater Availability ............................................... 39 Surface Water Availability .............................................. 40 GROUNDWATER AND WATER SUPPLY CONCERNS .................................. 43 Groundwater Quality ......................................................... 43 Water Supply Shortages and Identified Water Management Strategies ................... 45 Burnet County ........................................................ 46 Northern Travis County ................................................. 46 Williamson County .................................................... 47 Other Generally Recommended Strategies .................................. 50 STAKEHOLDER RESPONSE ........................................................ 53 Burnet Water Council ......................................................... 53 Williamson County Water Visionary Committee .................................... 54 Brazos River Authority ........................................................ 55 Municipalities and Water Purveyors ............................................. 55 Others ..................................................................... 56 EXISTING WATER PLANNING, REGULATORY AND MANAGEMENT ENTITIES .......... 59 Federal Agencies ............................................................. 59 State Water Planning and Regulatory Programs ..................................... 59 Regional Groups and Authorities ................................................ 61 Local Government and Water Purveyors .......................................... 62 Summary ................................................................... 65 ADMINISTRATIVE FEASIBILITY OF GROUNDWATER MANAGEMENT ................. 67 Groundwater Management Approaches ........................................... 67 Identified Groundwater Management Strategies .................................... 68 Economic Consideration and Impacts ............................................ 69 Financing Groundwater Management Activities .................................... 70 Management Options ......................................................... 71 Multi-County Groundwater Conservation District ............................ 74 Single-County Groundwater Conservation Districts ........................... 74 Addition to Existing Groundwater Conservation District ....................... 75 Stakeholder GCD Creation Issues and Concerns .................................... 76 SUMMARY ....................................................................... 79 Water Use and Supply ........................................................ 79 Groundwater Supply and Groundwater Quality Concerns ............................ 80 Natural Resources Concerns .................................................... 80 Projected Demand, Availability, and Strategies to Meet Needs ......................... 81 Stakeholder Concerns ......................................................... 82 CONCLUSIONS AND RECOMMENDATIONS .......................................... 85 Study Area Designation Recommendation ......................................... 85 Natural Resource Recommendations ............................................. 86 Groundwater Conservation District Considerations .................................. 86 REFERENCES ..................................................................... 89 APPENDIXES 1. 1990 Critical Area Report Summary for Texas Water Commission ..................... 93 2. Total Water Supply Projections in the Study Area ................................... 96 3. Williamson, Burnet and Northern Travis PGMA study, Updated Population Projection (TWDB, 2004) ............................................................. 103 4. Williamson, Burnet and Northern Travis PGMA study, Updated Water Demand Projection (TWDB, 2004) ............................................................. 107 5. Selected Hydrographs ........................................................ 111 TABLES 1. Estimated Water Use, 2000, Williamson, Burnet and Northern Travis Counties Study Area .. 32 2. Projected Population, Williamson, Burnet and Northern Travis Counties PGMA Study Area . 33 3. Total Water Demand Projections, Williamson, Burnet and Northern Travis Counties PGMA Study Area ................................................................. 36 4. Groundwater Availability, Williamson, Burnet and Northern Travis Counties PGMA Study Area ....................................................................... 40 5. Annual Surface Water Availability, Williamson, Burnet and Northern Travis Counties PGMA Study Area ................................................................. 41 6. Comparison of Water Demand and Current Supply, and Identified Needs in Williamson, Burnet, and Northern Travis Counties. .................................................. 45 FIGURES 1. Williamson, Burnet and Northern Travis Counties Study Area Location Map .............. 8 2. Major and Minor Aquifers, Williamson, Burnet and Northern Travis Counties PGMA Study Area .......................................................................... 10 3. Potetiometric Surface Map, 1997 - 1998, Edwards Aquifer ............................ 13 4. Water-level change in the Edwards Aquifer based on data collected 1987-1988 and data collected 1997-1998 .................................................................. 14 5. Simulated water-level changes 2010 through 2050, with average recharge ................ 15 6. Simulated water-level changes 2010 through 2050, with drought-of-record recharge ........ 16 7. Potetiometric Surface Map, 1997 - 1998, Trinity Aquifer ............................. 19 8. Water-level changes in the Trinity Group aquifers based on data collected 1987-1988 and data collected 1997-1998 .......................................................... 20 9. Simulated Water-level from 2000 to 2030 for layer 5 (Hensell), Assuming Average Recharge 21 10. Simulated Water-level from 2000 to 2030 for layer 7 (Hensell), Assuming drought of record recharge distribution ......................................................... 22 11. Simulated Water-level change from 2000 to 2030 for layer 7 (Hosston), Assuming Average Annual Recharge ............................................................ 23 12. Simulated Water-level change from 2000 to 2030 for layer 7 (Hosston), Assuming Drought of record recharge distribution .................................................... 24 13. Water Purveyors and Public Water Supply Wells in Williamson, Burnet and Northern Travis Counties ................................................................... 66 14. Map Showing Groundwater Management Area and Regional Water Planning Group Boundaries .......................................................................... 73 15. Map showing Groundwater Conservation Districts in Central Texas .................... 78 - page is intentionally blank - EXECUTIVE SUMMARY ppp A 1990 study by the Texas Water Commission [Texas Commission on Environmental Quality (TCEQ) predecessor agency] and Texas Water Development Board (TWDB) determined that Williamson County and parts of Bastrop, Bell, Burnet, Milam, and Travis