Soil and Water Assessment Tool. R. Srinivasan Texas A&M University

Transcription

1 Soil and Water Assessment Tool R. Srinivasan Texas A&M University

2 Model Philosophy Readily available input Physically based Comprehensive Process Interactions Simulate Management

3 ARS Modeling History Time Line CREAMS USLE (CLEAN WATER ACT) EPIC SWRRB SWAT 1960 s 1970 s 1980 s 1990 s GLEAMS WEPP AGNPS ANN AGNPS

4 Environmental Models Maintained at Temple, TX EPIC Field Scale ALMANAC Field Scale APEX Farm Scale SWAT Watershed Scale

5 SWAT Global Users

6 General Description Continuous Time Daily Time Step One Day Hundreds of Years Distributed Parameter Unlimited Number of Subwatersheds Comprehensive Process Interactions Simulate Management

7 SWAT Watershed System Upland Processes Channel/Flood Plain Processes

8 Example Configuration Cells/Subwatersheds Hydrologic Response Units Output from other Models Point Sources - Treatment Plants

9 Subbasins and Streams

10 Subbasins and Streams Subbasin 18

11 HRU s 28% Range-Sandy 51% Pasture Silt 16% Forest Sandy 4% - Agriculture - Silt Subbasins and Streams

12 Subbasins and Streams

13 Upland Processes Weather Hydrology Sedimentation Plant Growth Nutrient Cycling Pesticide Dynamics Management Bacteria

14 Hydrologic Balance Precipitation Root Zone Vadose (unsaturated) Zone Shallow (unconfined) Aquifer Confining Layer Deep (confined) Aquifer

15 Hydrologic Balance Root Zone Vadose (unsaturated) Zone Infiltration Surface Runoff Shallow (unconfined) Aquifer Confining Layer Deep (confined) Aquifer

16 Hydrologic Balance Evaporation and Transpiration Root Zone Vadose (unsaturated) Zone Shallow (unconfined) Aquifer Infiltration/plant uptake/ Soil moisture redistribution Percolation to shallow aquifer Lateral Flow Confining Layer Deep (confined) Aquifer

17 tile wtr Tile Flow 24 SW ly FCly exp tdrain Q lat SW FC 1 if ly ly 2 SWly, excess K d Lhill sat slp Hydrologic Balance Root Zone Vadose (unsaturated) Zone Tile Flow Shallow (unconfined) Aquifer Confining Layer Deep (confined) Aquifer

18 Hydrologic Balance Root Zone Vadose (unsaturated) Zone Shallow (unconfined) Aquifer Revap from shallow aquifer Percolation to shallow aquifer Return Flow Confining Layer Deep (confined) Aquifer Recharge to deep aquifer

19 Hydrologic Balance Root Zone Vadose (unsaturated) Zone Shallow (unconfined) Aquifer Confining Layer Deep (confined) Aquifer Flow out of watershed Recharge to deep aquifer

20 Hydrologic Balance Evaporation and Transpiration Precipitation Root Zone Vadose (unsaturated) Zone Shallow (unconfined) Aquifer Confining Layer Infiltration/plant uptake/ Soil moisture redistribution Revap from shallow aquifer Percolation to shallow aquifer Surface Runoff Lateral Flow Return Flow Deep (confined) Aquifer Flow out of watershed Recharge to deep aquifer

21 Plant Growth Month 12

22 Plant Growth Yield Prediction Harvest Index Water Stress Residue Cover and Nutrients Optimum Growth Radiation Interception LAI Radiation Use Efficiency Constraints Water, Temperature, Nitrogen, Phosphorus Residue Cover and Nutrients Water, Nitrogen and Phosphorus Uptake Root Growth

23 Climate Change Radiation Use Efficiency Adjusted for CO 2 ET Penman-Monteith Canopy Resistance Adjusted for CO 2 Impact on Leaf Conductance CGM Estimates of Precip, Temperature, Humidity, Solar Radiation, Wind Speed

24 Doorenbos & Kassam 1979 Crop development

25 Why explicit crop growth in a Hydrology Model? Crop cover / vegetation cover determines Transpiration (LAI) Interception Surface runoff (soil cover) Soil erosion (soil cover) Additional water consumption (aet) due to irrigation Nutrient uptake (biomass production) Indirect impact on water quality due to farming practise (i.e. fertilisation, pesticide application)

26 What can be simulated? Cropping systems with full crop rotation and farm management Planting / Beginning of growing season irrigation fertilisation pesticide application tillage operation harvest and kill (above-ground biomass is removed) kill/end of growing season (above-ground biomass becomes litter) grazing (biomass removal and manure input) auto irrigation auto fertilisation street sweeping release/impound (for rice)

27 Crop development / Heat Units Synonyms: Growing Degree Days Temperature Sum Heat Units PHU HU HU T AV Tbase when TAV Tbase SWAT Parameters: PHU and HEAT UNITS.mgt file

28 PHU program output

29 Atmospheric N fixation (lightning arc discharge) Nitrogen Cycle fertilizer Symbiotic fixation fertilizer manures, wastes and sludge NO 3 - Soil Organic Matter NO 3 - NH 4 + NO 2 -

30 Nitrogen Cycle Soil Organic Matter NO - 3 immobilization NH + 4 NO 3 - immobilization mineralization NO 2 - nitrification ammonium fixation clay

31 Nitrogen Cycle Harvest NH 3 N 2 N 2 O runoff ammonia volatilization denitrification NO 3 - Soil Organic Matter NO 3 - NH 4 + anaerobic conditions leaching NO 2 - clay

32 Atmospheric N fixation (lightning arc discharge) Nitrogen Cycle Harvest N 2 N 2 O fertilizer Symbiotic fixation fertilizer manures, wastes and sludge NH 3 runoff ammonia volatilization denitrification immobilization Soil Organic Matter mineralization NO - 3 immobilization NH + 4 NO 3 - NO 2 - ammonium fixation anaerobic conditions leaching nitrification clay

33 Phosphorus Cycle fertilizer Harvest runoff manures, wastes, and sludge manures, wastes and sludge H 2 PO 4 - HPO 4-2 mineralization immobilization Soil Organic Matter Adsorbed and fixed Inorganic Fe, Al, Ca, and clay

34 Foliar Application Pesticide Dynamics Degradation Surface Application Washoff Runoff Infiltration Degradation Leaching

35 Management Crop Rotations Removal of Biomass as Harvest/ Conversion of Biomass to Residue Tillage / Biomixing of Soil Fertilizer Applications Grazing Pesticide Applications

36 Management Irrigation Subsurface (Tile) Drainage Water Impoundment (e.g. Rice)

37 Management Urban Areas Pervious/Impervious Areas Street Sweeping Lawn Chemicals Edge of Field Buffers

38 Channel Processes

39 Channel Processes Flood Routing Variable Storage Muskingum Transmission Losses, Evaporation Sediment Routing Degradation and deposition computed simultaneously

40 Channel Processes Nutrients modified QUAL2E/WASP Pesticide Toxic balance developed at University of Colorado

41 In-stream Nutrient Processes Well-mixed Water Layer Atmospheric Aeration Transport in Org N NH 4 NO 2 NO 3 Dissolved Oxygen Carbonaceous BOD Org P Dissolved P Chlorophyll a Algae Transport out Sediment Layer Benthic Demand for Oxygen Benthic Sink/Source for Nutrients

42 In-stream Pesticide Processes Well-mixed Water Layer Volatilization Transport in Settling Well-mixed Sediment Layer Pesticide in Water Degradation Pesticide in Sediment Degradation Burial Transport out Resuspension

43 Impoundments Water Balance Inflow Evaporation Seepage Withdrawals Outflow Spillway Control Target Volume Approach Missouri River Reservoir Operation

44 Impoundments Nutrient Balance Well-mixed System Nitrogen & Phosphorus Loss Rates 2 Settling Periods per Year Pesticide Balance Well-mixed System Toxic balance developed at University of Colorado

45 Upland Processes SWAT Strengths Comprehensive Hydrologic Balance Physically-Based Inputs Plant Growth Rotations, Crop Yields Nutrient Cycling in Soil Land Management - BMP Tillage, Irrigation, Fertilizer, Pesticides, Grazing, Rotations, Subsurface Drainage, Urban-Lawn Chemicals, Street Sweeping

46 Channel Processes SWAT Strengths Flexible Watershed Configuration Water Transfer Irrigation Diversions Sediment Deposition/Scour Nutrient/Pesticide Transport Pond, Wetland and Reservoir Impacts

47 Conclusions SWAT is a product of over 30 years of USDA model development Partnership Texas A&M, ARS, EPA, NRCS Developing models, GIS, databases, applications Widely used for water quality, water supply and climate change

48 The End