FINAL REPORT COLORADO RIVER ENVIRONMENTAL MODELS PHASE 3: INKS LAKE, LAKE LBJ, LAKE MARBLE FALLS Prepared for: LOWER COLORADO RIVER AUTHORITY Prepared by: In conjunction with MARCH 2011 FINAL REPORT COLORADO RIVER ENVIRONMENTAL MODELING SYSTEM PHASE 3: INKS LAKE, LAKE LBJ, LAKE MARBLE FALLS Prepared for: LOWER COLORADO RIVER AUTHORITY Prepared by: 8000 Centre Park Drive, Suite 200 Austin, TX 78754 in conjunction with 901 S Mopac, Bldg IV, Suite 280 Austin, TX 78746 MARCH 2011 CREMs Phase 3 Inks Lake, Lake LBJ, Lake Marble Falls Table of Contents TABLE OF CONTENTS SECTION 1 INTRODUCTION ......................................................................................... 1-1 1.1 Background ............................................................................................................ 1-1 1.1.1 Inks Lake System ............................................................................................. 1-1 1.1.2 Lake LBJ System .............................................................................................. 1-2 1.1.3 Lake Marble Falls System ................................................................................ 1-2 1.1.4 Relevant Ordinances ......................................................................................... 1-3 1.1.4.1 TCEQ Highland Lakes Discharge Ban .................................................... 1-3 1.1.4.2 Highland Lake Watershed Ordinance...................................................... 1-3 1.2 Summary of the Phase 1 Effort ............................................................................... 1-3 1.3 Objectives of the CREMs Phase 2 and 3 Effort ....................................................... 1-4 1.4 Overview of the Phase 3 Report ............................................................................. 1-5 SECTION 2 MONITORING PROGRAM ........................................................................ 2-1 2.1 Overview................................................................................................................ 2-1 2.2 Program 1: Expanded Routine Monitoring.............................................................. 2-1 2.2.1 Expanded List of Parameters ............................................................................ 2-3 2.2.1.1 Laboratory Parameters ............................................................................ 2-3 2.2.1.2 Additional Field Parameters ................................................................... 2-4 2.2.2 Higher Resolution Sampling at Boundaries ....................................................... 2-5 2.2.3 Higher Resolution Sampling in the Lake ........................................................... 2-5 2.2.4 Additional Lake Stations .................................................................................. 2-5 2.2.5 Additional Tributary Stations ............................................................................ 2-5 2.2.6 Expanded Vertical Sampling ............................................................................ 2-5 2.2.7 Lower Detection Limits .................................................................................... 2-5 2.3 Program 2: Storm Water Monitoring ...................................................................... 2-6 2.3.1 Storm Types and Sampling Frequency .............................................................. 2-7 2.3.2 Tributary and Lake Stations .............................................................................. 2-8 2.4 Program 3: Remote Monitoring .............................................................................. 2-8 2.4.1 Thermistors and Thermistor Chains .................................................................. 2-8 2.4.2 Automated Profilers .......................................................................................... 2-9 2.5 Program 4: Special Manual Monitoring .................................................................. 2-9 2.5.1 Phytoplankton Investigation Study.................................................................... 2-9 SECTION 3 WATERSHED MODEL ............................................................................... 3-1 3.1 Introduction ............................................................................................................ 3-1 3.1.1 State Variables of Concern and Model Timestep ............................................... 3-1 PARSONS/ANCHOR QEA LLC i FINAL REPORT March 2011 CREMs Phase 3 Inks Lake, Lake LBJ, Lake Marble Falls Table of Contents 3.1.2 Model Input and Development .......................................................................... 3-2 3.1.2.1 Geospatial Input Data and Hydrologic Response Unit Generation ........... 3-2 3.1.2.2 Climatic Temporal Input Data ................................................................ 3-2 3.1.2.3 Point Source Dischargers ........................................................................ 3-3 3.1.3 General Description of Calibration ................................................................... 3-3 3.1.4 Calibration Data ............................................................................................... 3-3 3.2 Lake LBJ Watershed .............................................................................................. 3-4 3.2.1 Lake LBJ Watershed Spatial Domain ............................................................... 3-4 3.2.1.1 Geology .................................................................................................. 3-5 3.2.1.2 Climate ................................................................................................... 3-5 3.2.1.3 Topography ............................................................................................ 3-6 3.2.1.4 Soils ....................................................................................................... 3-6 3.2.1.5 Land Cover ............................................................................................. 3-7 3.2.1.6 Watershed Ordinance ............................................................................. 3-7 3.2.1.7 Point Sources .......................................................................................... 3-7 3.2.1.8 Sub-Watershed Delineation .................................................................. 3-10 3.2.2 Lake LBJ SWAT Model Calibration ............................................................... 3-10 3.2.2.1 Hydrology Calibration Data .................................................................. 3-10 3.2.2.2 Hydrology Calibration Approach .......................................................... 3-12 3.2.2.3 Water Quality Calibration Data ............................................................ 3-14 3.2.2.4 Water Quality Calibration Approach..................................................... 3-16 3.2.2.5 Watershed Operations........................................................................... 3-18 3.2.3 Lake LBJ SWAT Model Results ..................................................................... 3-18 3.2.3.1 Hydrology Calibration Results .............................................................. 3-18 3.2.3.2 Sediment Calibration Results ................................................................ 3-20 3.2.3.3 Nutrient Calibration Results ................................................................. 3-21 3.3 Lake Marble Falls Watershed ............................................................................... 3-24 3.3.1 Lake Marble Falls Watershed Spatial Domain ................................................ 3-24 3.3.1.1 Geology ................................................................................................ 3-25 3.3.1.2 Climate ................................................................................................. 3-25 3.3.1.3 Topography .......................................................................................... 3-25 3.3.1.4 Soils ..................................................................................................... 3-25 3.3.1.5 Land Cover ........................................................................................... 3-26 3.3.1.6 Watershed Ordinance ........................................................................... 3-26 3.3.1.7 Point Sources ........................................................................................ 3-26 PARSONS/ANCHOR QEA LLC ii FINAL REPORT March 2011 CREMs Phase 3 Inks Lake, Lake LBJ, Lake Marble Falls Table of Contents 3.3.1.8 Sub-watershed Delineation ................................................................... 3-26 3.3.1.9 Lake Marble Falls SWAT Model Calibration........................................ 3-27 3.3.1.10 Hydrology Calibration Data .................................................................. 3-27 3.3.1.11 Hydrology Calibration Approach .......................................................... 3-27 3.3.1.12 Water Quality Calibration Data ............................................................ 3-28 3.3.1.13 Water Quality Calibration Approach..................................................... 3-28 3.3.1.14 Watershed Operations........................................................................... 3-29 3.3.2 Lake Marble Falls SWAT Model Results ........................................................ 3-29 3.3.2.1 Hydrology Calibration Results .............................................................. 3-29 3.3.2.2 Water Quality Calibration Results .......................................................