Load Estimation Using Soil
and Water Assessment Tool
(SWAT)
Watershed Model: Soil and Water Assessment
Tool (SWAT)
 SWAT evaluates impacts of land use,
management, and climate on hydrology
and water quality
 It is a very widely used model
 Applied in every state and 32 different
countries
2
Land Use
+
Soils
Hydrologic
Response
Unit (HRU)
Land Management Practices
• Streamflow
•Groundwater
•Surface Water
• Evapotranspiration
• Suspended Solids
• Nitrogen
• Phosphorus
• Pesticides
3
Evaporation and
Transpiration
Hydrologic Balance
Precipitation
Surface Runoff
Root Zone
Infiltration/plant uptake/ Soil
moisture redistribution
Vadose
(unsaturated) Zone
Shallow
(unconfined)
Aquifer
Revap from shallow
aquifer
Lateral Flow
Percolation to
shallow aquifer
Confining Layer
Deep (confined)
Aquifer
Flow out of watershed
Recharge to
deep aquifer
Return Flow
Why do we need SWAT?
SWAT can help answer various “what if”
questions related to impacts of
agricultural and urban land use and
management on runoff, sediment,
nutrient, pesticide and bacteria transport
Calibration Statistics (1995- Validation Statistics (2005 2004) 10 years
2009) 5 years
Station Name
Monthly R2
Monthly NS
Monthly R2
Monthly NS
367.90
0.85
0.85
0.83
0.82
Kokomo Creek near Kokomo
64.63
0.8
0.74
0.75
0.72
Wildcat creek near Kokomo
614.00
0.9
0.9
0.97
0.94
Wildcat creek near Owasco
1009.00
0.92
0.91
0.89
0.87
Wildcat creek near Lafayette
2045.00
0.89
0.88
0.89
0.88
642.40
0.87
0.87
0.83
0.8
Wildcat near Jerome
South fork creek near Lafayette
Area (km2)
Station 36
8
TN calibration WCC
Sim TN
120000
Obs TN
Monthly averaged kg/day
100000
80000
60000
40000
20000
0
Jan-95
Jan-96
Jan-97
Jan-98
Jan-99
Jan-00
Jan-01
Jan-02
Jan-03
Jan-04
Jan-05
Jan-06
Jan-07
Jan-08
Jan-09
Nitrate Loads
Year
Nitrate Load
(Lbs/year)
2007
2,752,200
2008
3,000,800