Nutrient Delivery from the Mississippi River to the Gulf of Mexico and Effects of Cropland Conservation Mike White, Jeff Arnold, Lee Norfleet, Santhi Chinnasamy, and Mauro DiLuzio USDA-ARS Grassland, Soil and Water Research Laboratory USDA-NRCS Texas AgriLife Blackland Research Center
Justify US conservation expenditures (about 2 billion annually) Demonstrate water quality improvements due to conservation Uses SWAT and APEX
Public Data SWAT Model Complete Model Survey Data APEX Crop Field APEX Cultivated fields 18,000 farmer surveys SWAT All other landuses 2,200 Subbasins (8 digit HUC) 1,300 in MRB Streams/rivers Reservoirs SWAT Routing Delivered Load Prediction
Constituents Flow Sediment Nitrogen (TN, NO 3, NH 3, TKN) Phosphorus (TP, SP) Calibration 38 Sites
CEAP uses a custom SWAT Incompatible with existing software and interfaces Using expert knowledge Rules based calibration Automate manual calibration decision process Supports about 30 parameters Hydrology Matches measured data Flow, sediment, nutrients loads at fixed sites Considers other knowledge Sediment losses by landuse type Reach delivery ratios (aggregation/degradation) Reservoir trapping typical Reach sediment delivery low Increase SPCON Upland sediment yield too low Increase HRU slope Surface runoff too high Reduce curve number
Validation based on multiple indicators that a model represents the system Comparison to monitoring data 17 sites NSE Relative Error Comparison with SPARROW 1,300 locations R 2 >0.95 Comparison based on literature values and expert knowledge Export coefficients SWAT Check Delivery ratio analysis and inspection
Identical Farms Local Local Load Load 100 kg 100 kg 100 kg Differing Position 50 km 500 km Reservoir 50 km Delivered Load 90 kg Gulf 65 kg 25 kg 9
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No-Practice scenario Without the conservation practices reported by the CEAP survey Not a worst case scenario No landowner conservation ethic
Scenario Total Nitrogen (Million Kg/yr) Load From All Sources Delivered to the Gulf Total Phosphorus (Million kg/yr) No Conservation Practices 1,640 165 Current Conservation Condition 1,350 132 Reduction due to Conservation 18% 20%
Increase spatial resolution 2,200 Subbasins (HUC 8) to 60,000 (HUC 10-12) 75,000 HRUs to 2 million HRUs Expand calibration data 750 Sites More detailed data SSURGO Soils 15,000+ Weather gages
Break the Basin into submodels Build Dependency Tree Some are independent Others depend on flow from upstream Transfer water from one to another via saved hydrographs Execute models individually Asynchronously when dependences are satisfied Run on many processors or computers at once
Not Ready Ready Processing Finished Start Gulf
Not Ready Ready Processing Finished Cycle #0.5 Identify models without unmet dependencies Gulf
Not Ready Ready Processing Finished Cycle #1 Select 4 models to run Gulf
Not Ready Ready Processing Finished Cycle #2 Identify models without unmet dependencies and Select another 4 models to run Gulf
Not Ready Ready Processing Finished Cycle #3 Identify models without unmet dependencies and Select another 4 models to run Gulf
Not Ready Ready Processing Finished Cycle #4 Identify models without unmet dependencies and Select another 4 models to run Gulf
Not Ready Ready Processing Finished Cycle #5 Identify models without unmet dependencies and Select another 4 models to run Gulf
Not Ready Ready Processing Finished Cycle #6 Identify models without unmet dependencies and Select available models to run Gulf Grassland, Soil and Water Research Laboratory, 25 Temple, TX
Not Ready Ready Processing Finished Cycle #7 Identify models without unmet dependencies and Select available models to run Gulf
Not Ready Ready Processing Finished Cycle #8 Identify models without unmet dependencies and Select available models to run Gulf
Not Ready Ready Processing Finished Finished 23 Subbasins processed in 8 cycles Gain = 23/8 = 280% Gulf
Manager Server Node Client Model Repository Network Share SWATHUC8 01001001 01001002 01001003
Windows Cluster 150 cores 3.3-2.0 GHZ 60,000 HRU model run for 37 Years takes 6 min on 8 nodes