Minnesota Pollution Control Agency Project Manager: Dr. Hafiz Munir Long Prairie River Watershed TMDL Project: Final Project Report Prepared by: WENCK ASSOCIATES, INC. 1800 Pioneer Creek Center P.O. Box 249 Maple Plain, Minnesota 55359-0249 July 2004 (763) 479-4200 FTN ASSOCIATES, LTD. 3 Innwood Circle, Suite 220 Little Rock, AR 72211 (501) 225-7779 Table of Contents 1.0 EXECUTIVE SUMMARY ............................................................................................. 1-1 2.0 INTRODUCTION/ PROBLEM STATEMENT........................................................... 2-1 3.0 APPLICABLE WATER QUALITY STANDARDS .................................................... 3-1 4.0 BACKGROUND INFORMATION ............................................................................... 4-1 4.1 General Description of River and Watershed...................................................... 4-1 4.1.1 Sub-watersheds...................................................................................... 4-1 4.1.2 Land Use................................................................................................ 4-2 4.1.3 Soils ....................................................................................................... 4-2 4.2 Climate and Meteorological Data........................................................................ 4-2 4.3 Hydrology ............................................................................................................ 4-3 4.4 Point Sources ....................................................................................................... 4-3 4.5 Non-Point Sources ............................................................................................... 4-5 4.6 Previous Studies................................................................................................... 4-6 5.0 REVIEW AND ANALYSIS OF DATA FROM OTHER SOURCES ........................ 5-1 5.1 Introduction and Summary of Findings ............................................................... 5-1 5.2 Water Quality Data .............................................................................................. 5-2 5.3 Data Analysis....................................................................................................... 5-4 6.0 FIELD INVESTIGATION METHODS........................................................................ 6-1 6.1 Parameters............................................................................................................ 6-2 6.2 Locations.............................................................................................................. 6-3 6.3 Schedule............................................................................................................... 6-3 6.4 Data Collection Methods ..................................................................................... 6-5 6.4.1 Sample Handling and Custody ............................................................ 6-11 6.4.2 Quality Control Measures ................................................................... 6-11 6.4.3 Data Assessment and Oversight .......................................................... 6-12 Table of Contents (continued) 7.0 RESULTS OF FIELD INVESTIGATIONS ................................................................. 7-1 7.1 Pollutant Loadings ............................................................................................... 7-1 7.1.1 Point Source Loadings........................................................................... 7-1 7.1.2 River Loadings ...................................................................................... 7-2 7.1.3 Discussion of Point Sources and Non-point Sources ............................ 7-2 7.2 Statistical Analysis............................................................................................... 7-3 7.2.1 DO ......................................................................................................... 7-3 7.2.2 DO Daily Range .................................................................................... 7-4 7.3 DO Impairment Analysis ..................................................................................... 7-4 8.0 OVERVIEW OF MODELING APPROACH............................................................... 8-1 8.1 Conceptual Model Approach and Setup .............................................................. 8-4 8.1.1 QUAL – TX........................................................................................... 8-5 8.1.2 SWAT Model ........................................................................................ 8-7 8.1.3 Sensitivity Analysis............................................................................... 8-8 8.1.4 Calibration/Validation Tolerance Goals................................................ 8-9 8.2 Model Calibration and Validation Sites............................................................. 8-10 9.0 QUAL-TX MODELING ................................................................................................. 9-1 9.1 Introduction.......................................................................................................... 9-1 9.2 Model Configuration............................................................................................ 9-2 9.3 Hydraulics............................................................................................................ 9-3 9.3.1 Stream Flow Gauging............................................................................ 9-3 9.3.2 Low-flow Extrapolation ........................................................................ 9-4 9.3.3 Dye Studies............................................................................................ 9-4 9.3.4 Carlos Reach Hydraulics ....................................................................... 9-5 9.4 Kinetic Rates........................................................................................................ 9-6 9.4.1 Reaeration Rates.................................................................................... 9-6 9.4.2 Photosynthetic Productivity .................................................................. 9-8 9.4.3 Sediment Kinetic Rates ....................................................................... 9-10 9.4.4 Ultimate Carbonaceous BOD.............................................................. 9-13 9.4.5 Nitrogen Kinetic Rates ........................................................................ 9-16 9.4.6 Temperature Corrections for Kinetics................................................. 9-17 9.5 Boundary and Initial Conditions........................................................................ 9-17 9.5.1 Headwaters and Tributaries................................................................. 9-18 9.5.2 Point Source Inputs.............................................................................. 9-18 9.5.3 Initial Conditions................................................................................. 9-18 9.6 Non-point Source Inputs.................................................................................... 9-19 Table of Contents (continued) 9.6.1 Published Historical Groundwater Discharge Rates ........................... 9-19 9.6.2 Calculated Incremental Inflows for Monitoring Periods..................... 9-19 9.6.3 Water Quality of Incremental Inflows................................................. 9-21 9.7 Model Calibration, Verification, and Sensitivity............................................... 9-23 9.7.1 Model Calibration................................................................................ 9-23 9.7.2 Model Verification .............................................................................. 9-25 9.7.3 Model Sensitivity ................................................................................ 9-26 9.8 Critical Condition Projections ........................................................................... 9-28 9.8.1 7Q10 Model Setup............................................................................... 9-28 9.8.2 TMDL Projection Simulation.............................................................. 9-36 10.0 SWAT MODEL ............................................................................................................. 10-1 10.1 Model Configuration.......................................................................................... 10-1 10.2 Watershed Data.................................................................................................. 10-2 10.3 Climatic Data ..................................................................................................... 10-5 10.4 Hydrologic Inputs .............................................................................................. 10-6 10.5 Hydrologic Calibration ...................................................................................... 10-7 10.6 Water Quality Inputs.......................................................................................... 10-9 10.7 Sediment Calibration ......................................................................................... 10-9 10.8 Nutrient Calibration ......................................................................................... 10-10 10.9 Model Verification........................................................................................... 10-11 10.10 Model Results .................................................................................................