swat: soil & water assessment tool
TRANSCRIPT
SWAT: Soil & Water Assessment Tool
Created and primarily maintained by Jeff Arnold, USDA-ARS, Temple, TX.
Used locally and presented by Tamie Veith, USDA-ARS, State College, PA
SWATSoil & Water Assessment Tool
Nonpoint source simulation model Hydrologically-driven Continuous time-step Divides watershed into HRUs w/in subbasins
HRU = hydrologic response unit = soil/landuse/slope units
Routes by subbasin
Input Data – widely available DEM – usually 10 or 30 meter Soil survey – SSURGO Basic land use – PAMAP Stream network and outlet point
– USGS, aerial photo, blue line stream Precipitation (daily or breakpoint)
Min, max air temperature Humidity, solar radiation, wind speed
Streamflow (m3/s) – for calibration
OPTIONAL
Input Data – harder to quantify
Field boundaries Rotational land use and management BMPs
placement, maintenance, lifespan Stream quality – for calibration
Sediment, N, P, chemicals (atrazine) Biochemical oxygen demand, dissolved
oxygen, algae, coliform bacteria
Output -- Environmental Stream reach and outlets
Stream flow Sediment, N, P, chemicals (atrazine) Biochemical oxygen demand, dissolved oxygen, algae,
coliform bacteria
Crops # days water, nutrient stressed Biomass, yield, evapotranspiration
Overland Water movement - surface, lateral, groundwater Erosion Nutrients – surface, leaching, soil Mass water balance
Output – Land management
By careful pre- and post processing and deduction.
Output – Regulatory, economic
NONE
End User
Researcher or simulation modeler for conservationists and policy makers
Software
SWAT http://swatmodel.tamu.edu Free
ESRI ArcGIS Desktop w/ Spatial Analyst http:// www.esri.com ArcEditor: $7000 ArcView: $1500 Spatial Analyst: $2500 GIS viewers: freeUniversity or Agency may have site license
Training
SWAT modeling 2 day workshops $500 each yearly in TX
SWAT data processing 1 day workshop $200
ArcGIS online tutorials 1 to 3 day workshops free to $500/8hr sites around US
Also may be available through university
Scale of Relevance
Watershed+ within-field variability
+ topography+ soils
+ detailed land management+ hydrology / nutrient losses
+ individual fields+ watershed
USDA / ARS
BMP placement: Farm-level
Crop rotations & contour strip crop
Crop rotations & nutrient management plans
Contour strip crop & nutrient management plans
Nutrient management plans
Riparian forest buffers None
Basic Optimal
BMP placement: Watershed-level
Same P loss, 30% cheaper
Assumptions / Limitations Limited surface routing Daily rainfall by volume
Intense or 2-day storms can be muted
Best for long-term, steady-state predictions Underpredicts low-flow and extreme event volumes
Stream model, QUAL2E Steady-state, 1-dimensional flow and water quality in
well-mixed streams
Farm 4
Farm 3
Farm 1
Farm 2
No natural flow boundaries
Other boundaries: economic, social, political
Adjacent fields managed differently
Down stream water quality impacts
Boundaries Seldom Coincide
Whole Farm Approach
USDA / ARS
IFSM: Integrated Farm System Model
Whole farm simulation modelDriven by farm production Process-basedDaily time-step Evaluated seasonally or annually Output to end user is average annual with
standard deviation
Created and maintained by Al Rotz, USDA-ARS, State College, PA
Integrated Farm System Model
Input Data Crop type, rotation, quality management practices, timing, machinery storage facilities and selling strategy
Animal type, housing, feed, replacement strategy management equipment and facilities manure management
BMP / alternative management scenarios Cultural/social considerations
Output -- Environmental Surface runoff and sediment from farm N overland, leached, volatilized, soil balance
P overland in runoff or sediment-bound, soil balance
K overland, soil balance
Ammonia, & greenhouse gas emissionsDairyGHG & DairyGEM – Emission predicting models. Use same processes but less user input.
Output – Farm management Crops # days water stressed, biomass, yield, CP, NDF
Animals production, replacement, rations fed
Output – Economic All production costs Labor, machinery, facilities, feed/bedding/fertilizer/fuel Net return to farm
End User / Training
Researcher, conservationist for the farmer or policymaker
Farmer is most knowledgeable about inputs and best farm representation
BUT model is largely a researcher tool No HELP desk
DairyGEM is more user-friendly
Software - Free http://www.ars.usda.gov/Main/docs.htm?docid=2708
Scale of Relevance
Farm crop growth feeding strategies milk production farm profitability nutrient balances
off-farm nutrient losses
Compare farm-level effects of manure application methods
Precision management
Parameters ID
Farm net return 1
Purchased feed cost 2
Seed, fertilizer cost 3
Machinery cost 4
Total production cost 5
Milk and animal income 6
Sed-P loss from corn 7
Sed-P loss from the farm 8
Sediment loss from corn fields 9
Sediment loss from the farm 10-90% -60% -30% 0% 30%
10
9
8
7
6
5
4
3
2
1
-90% -60% -30% 0% 30%
10
9
8
7
6
5
4
3
2
1
• 4 ha increase in corn area• 5% increase milk prodn. • No till
•12 ha small grain • No till
0.3-0.1
-2 -1 0 1 2
P balance
Assumptions / Limitations
Not strictly continuous Infrequently harvested grasses difficult
Dairy, beef, or crop farms Corn, soybean, small grain, alfalfa, grasses
No spatial placement within farm
No split management on same crop
USDA
Pasture Systems and Watershed Management Research Unit
Mention of trade names or commercial products in this publication is solely for the purpose of providing specific information and does not imply recommendation or endorsement by the U.S. Department of Agriculture. USDA is an equal opportunity provider and employer.
Agricultural Research Service
USDA / ARS
USDA Model Descriptions
USGS Surface Water and Water Quality Models Information Clearinghouse http://smig.usgs.gov/SMIC/SMIC.html
Some ARS Software and Datasets: http://www.ars.usda.gov/services/