Des Moines Headwaters, Lower Des Moines, and East Fork Des Moines River Basins Watershed Model Development) Prepared for Minnesota Pollution Control Agency Prepared by One Park Drive, Suite 200 • PO Box 14409 Research Triangle Park, NC 27709 June 27, 2016 wq-ws4-52c (This page left intentionally blank.) Des Moines River Watershed Model Report June 28, 2016 Table of Contents 1 Introduction ...................................................................................................................1 2 Watershed Model Development ...................................................................................5 2.1 Upland Representation ......................................................................................................................5 Geology, Soils, and Slopes ........................................................................................................5 Land Use and Land Cover .........................................................................................................9 Development of HRUs ............................................................................................................. 12 2.2 Meteorology .................................................................................................................................... 15 Data Processing ....................................................................................................................... 15 Auxiliary Weather Series ......................................................................................................... 19 2.3 Model Segmentation and Reach Network ....................................................................................... 20 Subwatershed Delineation ....................................................................................................... 20 Stream Reach and Lake Delineation ........................................................................................ 23 Representation of Groundwater-Surface Water Interactions ................................................... 25 Reach Hydraulics ..................................................................................................................... 27 Lake Storage and Outflow ....................................................................................................... 27 2.4 Point Source Discharges .................................................................................................................. 28 3 Model Calibration and Validation Approach .............................................................31 3.1 Flow and Water Quality Data .......................................................................................................... 31 Flow Gaging Data .................................................................................................................... 31 Water Quality Data .................................................................................................................. 32 3.2 Hydrology Calibration Approach .................................................................................................... 34 3.3 Sediment Calibration Approach ...................................................................................................... 36 3.4 Water Quality Calibration Approach ............................................................................................... 39 4 Hydrology Calibration and Validation Results...........................................................43 4.1 Snow Calibration ............................................................................................................................. 43 4.2 Constraints on Soil Moisture Balance and Evapotranspiration ....................................................... 45 4.3 Flow Calibration .............................................................................................................................. 47 4.4 Flow Validation ............................................................................................................................... 52 4.5 Water Balance Summary ................................................................................................................. 53 5 Sediment Calibration ..................................................................................................55 5.1 Upland Sediment Loading Rates ..................................................................................................... 55 5.2 Reach Sediment Mass Balance ........................................................................................................ 56 5.3 Instream versus Upland Sediment Sources ..................................................................................... 58 5.4 Calibration to Observed Total Suspended Solids Data .................................................................... 58 iii Des Moines River Watershed Model Report June 28, 2016 5.5 Comparison to FLUX Load Estimates ............................................................................................ 64 6 Nitrogen and Phosphorus Calibration .........................................................................67 6.1 Nutrient Model Setup ...................................................................................................................... 67 Nonpoint Sources ..................................................................................................................... 67 Point Sources ........................................................................................................................... 69 Channel Sources ...................................................................................................................... 70 Atmospheric Deposition .......................................................................................................... 71 Regeneration from Lake Sediment .......................................................................................... 71 6.2 Nutrient Calibration ......................................................................................................................... 71 Comparison of Model to Observations .................................................................................... 72 Comparison of Model to FLUX Estimates of Delivered Load ................................................ 79 Consistency with Lake Analyses ............................................................................................. 83 7 Water Temperature Calibration ..................................................................................87 8 Algae and Dissolved Oxygen Calibration ..................................................................89 8.1 Algae ............................................................................................................................................... 89 8.2 Dissolved Oxygen ........................................................................................................................... 91 9 Potential Model Enhancements ..................................................................................95 10 References .................................................................................................................97 (The following appendices are included in a separate document.) Appendix A. Detailed Snow Calibration Results Appendix B. Detailed Flow Calibration Results Appendix C. Detailed Flow Validation Results Appendix D. Suspended Solids and Water Quality Calibration and Validation iv Des Moines River Watershed Model Report June 28, 2016 List of Tables Table 2-1. NLCD Land Use for 2006 and 2011 in the Des Moines River Watershed ................ 10 Table 2-2. Land Use Aggregation for the Des Moines River Watershed HSPF Model .............. 11 Table 2-3. Hydrologic Response Units for the Des Moines River Watershed Model ................. 14 Table 2-4. Lakes Represented Explicitly in the Des Moines River Watershed Model ............... 24 Table 2-5. Permitted Point Source Discharges in the Des Moines River Watershed .................. 28 Table 3-1. Flow Gages in the Des Moines River Watershed Model Domain ............................. 31 Table 3-2. Water Quality Calibration Locations for the Des Moines River Watershed Model .. 33 Table 3-3. Performance Targets for HSPF Hydrologic Simulation (Magnitude of Annual and Seasonal Relative Mean Error (RE); Daily and Monthly NSE) ............................................ 36 Table 3-4. Performance Targets for HSPF Sediment Simulation (Magnitude of Annual and Seasonal Relative Average Error (RE) on Daily Values) ...................................................... 39 Table 3-5. Performance Targets for HSPF Water Quality Simulation (Magnitude of Annual and Seasonal Relative Average Error (RE) on Daily Values) ............................................... 42 Table 4-1. HSPF Snow Calibration Parameter Values ................................................................ 43 Table 4-2. Summary of Snow Calibration Results ...................................................................... 45 Table 4-3. Summary of Evapotranspiration Calibration Results ................................................. 46 Table 4-4. Selected Hydrology Parameters for Pervious Land.................................................... 47 Table 4-5. Summary of Flow Calibration Results ....................................................................... 48 Table 4-6. Summary of Flow Validation