Northern Trinity/Woodbine GAM Assessment of Groundwater Use in the Northern Trinity Aquifer Due To Urban Growth and Barnett Shale Development Prepared for Texas Water Development Board Austin, Texas TWDB Contract Number: 0604830613 Prepared by R. W. Harden & Associates, Inc. Hydrologists • Geologists • Engineers Austin, Texas January 2007 The seals appearing on this document were authorized by James E. Bené, P.G. 2089 and Robert Harden, P.E. 79290 on January 11, 2007. Changes to the Report Date The following edits have been made to the original report published on January 11, 2007. (1) Appendix 3, page 3-1: Additional narratives are provided to better explain the pumpage data sets and histograms presented in this appendix. The pumpage data presented includes county use estimates and may include pumpage from all aquifers within a county, and not necessarily correspond to the Trinity/Woodbine GAM pumpage inputs ………………………………………………………………07-24-2007 (2) Appendix 2, page 2-45: Changed reported units for recycled water from 2,500 gal/day/unit (~2 gpm) to 2,500 bbl/day/unit (~73 gpm)………………………04-09-2007 (3) Executive Summary, page 1, paragraph 1: We have now included Denton County to the description of the study area. The study area included Denton County but we did not list Denton County in the original Executive Summary…………………………...02-12-2007 (4) Appendix 2, page 2-21, Table 1: Changed the caption from “2000-2005 Historical Groundwater Use in the Barnett Shale(all sources, AF/yr)” to “2000-2005 Historical Water Use in the Barnett Shale (all sources, AF/yr)”………………………….02-12-2007 (5) Appendix 3, page 3-82, Table 3-3: This table shows predictive groundwater use under a high use scenario. In the original report, Table 3-3 had the same numbers as Table 3-2, groundwater use under a low use scenario. We have changed the numbers in table 3-3 to include the correct values………………………………………………….......02-07-2007 Assessment of Groundwater Use i Urban Growth and Barnett Shale Uses Northern Trinity/Woodbine GAM Table of Contents Executive Summary...................................................................................................................1 Acknowledgements....................................................................................................................5 Introduction................................................................................................................................7 Study Area .................................................................................................................................7 Updated Groundwater Demand Estimates...............................................................................12 Rural Domestic and Municipal Demand Projections ................................................................12 Barnett Shale Water Use............................................................................................................14 Total Groundwater Use..............................................................................................................18 Distribution of Pumpage............................................................................................................23 Barnett Shale Production .......................................................................................................23 Vertical Distribution of Pumpage ......................................................................................24 Distribution of Other Use Categories ....................................................................................25 Results of GAM Simulations...................................................................................................26 Regional Changes in Water Levels............................................................................................26 Changes in Piezometric Head ................................................................................................26 Effect of Drought ...................................................................................................................27 Water Table Depletion...........................................................................................................40 Regional Changes in Aquifer Water Budgets............................................................................40 Site Specific Well Drawdown Issues.........................................................................................45 Limitations of Model Results...................................................................................................48 Conclusions..............................................................................................................................48 References................................................................................................................................50 Assessment of Groundwater Use i Urban Growth and Barnett Shale Uses Northern Trinity/Woodbine GAM Table of Tables Table 1. Estimates of Total Water Use in 2000......................................................................10 Table 2. Predicted Total Water Use........................................................................................11 Table 3. Non-Barnett Shale Demands on the Trinity Aquifer by County ..............................13 Table 4. Non-Barnett Shale Demands on the Woodbine Aquifer by County.........................13 Table 5a. Percent Use by Category – Low Groundwater Demand Estimate..........................19 Table 5b. Percent Use by Category – High Groundwater Demand Estimate.........................20 Table 6. Model Water Budget – Year 2000............................................................................43 Table 7. Model Water Budget – Year 2025 – Low Demand Scenario...................................43 Table 8. Model Water Budget – Year 2000............................................................................44 Table 9. Model Water Budget – Year 2025 – High Demand Scenario ..................................44 Table of Figures Figure 1. Study Area.................................................................................................................9 Figure 2. Annual Gas Well Completions in Barnett Shale .....................................................16 Figure 3. Total Annual Barnett Shale Groundwater Demand Projections..............................17 Figure 4. Total Groundwater Use by Category - Low Demand Estimate ..............................21 Figure 5. Total Groundwater Use by Category - High Demand Estimate..............................22 Figure 6. Projected Water Level Change in Hosston (2000 through 2025) – Low Demand Estimate.................................................................................................28 Figure 7. Projected Water Level Change in Hensell (2000 through 2025) – Low Demand Estimate.................................................................................................29 Figure 8. Projected Water Level Change in Paluxy (2000 through 2025) – Low Demand Estimate.................................................................................................30 Figure 9. Projected Water Level Change in Woodbine (2000 through 2025) – Low Demand Estimate.................................................................................................31 Figure 10. Projected Water Level Change in Hosston (2000 through 2025) – High Demand Estimate................................................................................................32 Figure 11. Projected Water Level Change in Hensell (2000 through 2025) – High Demand Estimate................................................................................................33 Figure 12. Projected Water Level Change in Paluxy (2000 through 2025) – High Demand Estimate................................................................................................34 Figure 13. Projected Water Level Change in Woodbine (2000 through 2025) – High Demand Estimate................................................................................................35 Assessment of Groundwater Use ii Urban Growth and Barnett Shale Uses Northern Trinity/Woodbine GAM Figure 14. Historical Simulated Drawdown in Hosston (1880 – 2000) .................................36 Figure 15. Historical Simulated Drawdown in Hensell (1880 – 2000) ..................................37 Figure 16. Historical Simulated Drawdown in Paluxy (1880 – 2000) ...................................38 Figure 17. Historical Simulated Drawdown in Woodbine (1880 – 2000)..............................39 Figure 18. Location of New Water Table Depletion Areas in High Demand Estimate – Hosston (2000 – 2025).................................................................................................42 Figure 19. Well Drawdown Diagram......................................................................................47 Table of Appendices Appendix 1. Updated Rural and Domestic Supplies Appendix 2. Barnett Shale Groundwater Use Estimates Appendix 3. County Groundwater Use Estimates Appendix 4. Draft Report Comments and Responses Assessment of Groundwater Use iii Urban Growth and Barnett Shale Uses Northern Trinity/Woodbine GAM This page intentionally left blank. Assessment of Groundwater Use iv Urban Growth and Barnett Shale Uses Northern Trinity/Woodbine GAM EXECUTIVE SUMMARY Increasing water use due to growing population, drought, and natural gas production have heightened concerns in North-Central