MEDINA COUNTY REGIONAL WATER MANAGEMENT PLAN Prepared by BEXAR-MEDINA-ATASCOSA WCID #1 P.O. Box 170 Natalia, Texas 78059 (830) 665-2132 - In association with BNC ENGINEERING, LLC. 607 River Bend Drive Georgetown, Texas 78628 (512) 930-1535 MEDINA COUNTY REGIONAL WATER PLAN TABLE OF CONTENTS Executive Summary ......................................................................................................vi Section 1 - Introduction Objectives ............................................................................................. 1-1 Physical Description of the Study Area ................................................. 1-2 Demographic Description .................................................................... 1-12 Economic Description ......................................................................... 1-13 Current Water Planning and Regulatory Status .................................. 1-15 Section 2 - Population Projections and Water Demands Population Projections .......................................................................... 2-1 Water Demands .................................................................................... 2-5 Section 3 - Existing Groundwater Sources Introduction ........................................................................................... 3-1 Methodology ......................................................................................... 3-1 Overview of the Regional Hydrogeology ............................................... 3-1 Water Bearing Characteristics and Aquifer Use ................................... 3-8 Edwards Aquifer ................................................................................. 3-10 Additional Groundwater Sources ........................................................ 3-17 Summary ............................................................................................ 3-31 Section 4 - Existing Surface Water Resources - Getting surface water infonnation from the TNRCC and Water Masters Office Introduction ........................................................................................... 4-1 Existing Surface Water Use .................................................................. 4-1 Available Water Rights ......................................................................... 4-4 Section 5 - Water Resource Management Options Introduction ........................................................................................... 5-1 Section 6 - Demand Versus Supply Comparisons Introduction ........................................................................................... 6-1 Major Municipalities in Medina County .................................................. 6-3 Medina County ...................................................................................... 6-7 Section 7 - Water Supply Altematives Introduction ........................................................................................... 7-1 Liner Construction Economics .............................................................. 7-7 Siphon Replacement ............................................................................ 7-9 Slope Stability ..................................................................................... 7-10 Pearson Lake ..................................................................................... 7-17 TABLE OF CONTENTS (CONT'D) Appendix A 1 - Water Conservation I Drought Contingency Plan Introduction ........................................................................................ A 1-1 Long Term Water Conservation Plan ................................................ A 1-3 Drought Contingency Plan ................................................................. A1-7 Appendix A2 - Utility Evaluation ................................................................................ A2-1 Appendix 8 - SIMYLD-II Analysis I Summary of Results Without Irrigation Conservation, ASR and Pearson Lake ................... 8-2 Without Irrigation Conservation, But With ASR and Pearson Lake ... 8-17 With Irrigation Conservation, But Without ASR and Pearson Lake ... 8-32 With Irrigation Conservation, ASR and Pearson Lake ....................... 8-47 Appendix C - Texas Water Development 80ard Comments ...................................... C-1 ii MEDINA COUNTY REGIONAL WATER PLAN LIST OF FIGURES Figure 1-1 Location Map of Medina County ........................................................... 1-3 Figure 2-1 Population Projections for Medina County ............................................ 2-3 Figure 2-2 Medina County Groundwater Pumpage .............................................. 2-23 Figure 2-3 Average Percentage of Groundwater Pumped from Each Aquifer in Medina County .................................................................................... 2-24 Figure 5-1 Medina Main Dam ................................................................................. 5-8 Figure 5-2 SIMYLD Network. Configuration for Water Supply Operation .............. 5-11 Figure 5-3 Relationships between Historical Medina Lake Diversions into SMA Canal and SMA Canal Losses and Irrigation Usage without Conservation Measures or Pearson Lake ........................................... 5-17 Figure 5-4 Relationships between Historical Irrigation Usage and SMA Canal Losses and Medina Lake Diversions into SMA Canal without Conservation Measures or Pearson Lake ........................................... 5-18 Figure 5-5 Relationships between Irrigation Usage and SMA Canal Losses and Medina Lake Diversions into SMA Canal with Conservation Measures but without Pearson Lake ................................................................... 5-19 Figure 5-6 Relationships between Irrigation Usage and SMA Canal Losses and Medina Lake Diversions into SMA Canal with Conservation Measures and with Pearson Lake ....................................................................... 5-20 Figure 5-7 Relationship between Historical Annual Irrigation Canal Diversions and Historical Annual Inflows to Medina Lake .................................... 5-22 Figure 5-8 Annual Water Use from Medina Lake - Without Pearson Lake, Without ASR, Without Conservation ................................................... 5-23 Figure 5-9 Annual Water Use from Medina Lake - With Pearson Lake, With ASR, Without Conservation ................................................................ 5-24 Figure 5-10 Annual Water Use from Medina Lake - Without Pearson Lake, Without ASR, With Conservation ........................................................ 5-25 Figure 5-11 Annual Water Use from Medina Lake - With Pearson Lake, With ASR, With Conservation ..................................................................... 5-26 iii MEDINA COUNTY REGIONAL WATER PLAN LIST OF TABLES Table 1-1 Stratigraphic Data from Wells in Medina County .................................. 1-9 Table 1-2 Approximate Acreage and Proportionate Extent of the Soils in Medina County .................................................................................... 1-10 Table 1-3 General Demographic Data for Medina County .................................. 1-12 Table 1-4 Agricultural Land Use ......................................................................... 1-14 Table 1-5 Major Crops ........................................................................................ 1-14 Table 2-1 Medina County Population Projections ................................................. 2-2 Table 2-2 Population Projections of Major Cities in Medina County ...................... 2-2 Table 2-3 Population Increase by Decade and Planning Period ........................... 2-4 Table 2-4 County Other Population Projections .................................................... 2-5 Table 2-5 Historical Per Capita Municipal Water Use, GPCD ............................... 2-9 Table 2-6 Historical Municipal Water Use, Ac-FtlYear ........................................ 2-10 Table 2-7 Projected Water System Demands for Municipal Uses ...................... 2-11 Table 2-8 Historical Manufacturing Water Use ................................................... 2-13 Table 2-9 Manufacturing Demand Projections .................................................... 2-14 Table 2-10 Historical Irrigation Water Use ............................................................ 2-15 Table 2-11 Irrigation Demand Projections ............................................................. 2-16 Table 2-12 Groundwater Historical Mining Water Use .......................................... 2-17 Table 2-13 Mining Demand Projections ................................................................ 2-17 Table 2-14 Historical Livestock Use ...................................................................... 2-18 Table 2-15 Livestock Demand Projections ............................................................ 2-19 Table 2-16 Projected Total Water Demand in Medina County .............................. 2-19 Table 2-17 Public Water Suppliers in Medina County for 1994 ............................ 2-21 Table 2-18 Groundwater Pumpage Summary by Major Aquifer ............................ 2-22 Table 2-19 Medina County Groundwater Pumpage .............................................. 2-23 Table 3-1 Geologic and Hydrological Units and Their Water-Bearing Properties. 3-3 Table 3-2 Calculated Average Daily and Total Annual Discharge from the Edwards Aquifer in Medina County by Water Use for the Year 1991. 3-10 Table 3-3 Areal