1. Soil Water Assessment Tool (SWAT) Model Input
Assefa Melesse

2. SWAT features Physically based Uses readily available inputs
Needs basin-specific data on “...weather, soil properties, topography, vegetation, and land management practices...”
Benefits:
Ungaged watersheds can be modeled
Sensitivity to different input data can be quantified
Uses readily available inputs
GIS sets often already compiled by different agencies
Computationally efficient
Even for very large basins
Determines long-term impacts
SWAT is a continuous time model

3. SWAT
MODEL OBJECTIVE
Predict the effect of management decisions (Climate and vegetative changes, reservoir management, groundwater withdrawals, water transfer) on water, sediment, nutrient and pesticide yields on large, ungaged river basins.
MODEL COMPONENTS:
Weather, surface runoff, percolation, ET, transmission losses, pond & reservoir storage, crop growth & irrigation, groundwater flow, reach routing, nutrient & pesticide loading, water transfer

4. SWAT Model Input INPUT DATA: Physical Weather Hydrological
Elevation, Land cover, soil
Weather
Rainfall, air temperature (Min and max), solar radiation, wind speed and relative humidity
Hydrological
Stream flow, sediment and nutrient delivery data
Non-point and point source pollution data
Fertilizer and pesticide application data
Point source of pollution

5. SWAT Database

6. SWAT Model Input: Elevation
INPUT DATA:
DEM:
SRTM (90m) from USGS or other sources (
Watershed delineation
Stream network and confluences
Entering point sources

7. SWAT Model Input: Land cover
INPUT DATA:
Land cover
Landsat-derived (Level I?) data
CN, manning’s coefficient
land cover/land use map will need to be
reclassified into SWAT land cover/plant types.
Three options

8. SWAT Model Input: Land cover cont.
to use USGS category codes when creating the map (or use a USGS land use/land cover map).
to select the SWAT land cover/plant type or urban code for each category
to create a look up table that identifies the 4-letter SWAT code for the different categories of land cover/land use

9. SWAT Model Input: Land cover cont.

10. SWAT Model Input: Soil
Runoff, infiltration, sediment and anion exchange
1: 5M vector (Source:
The user will import SWAT soil files (.sol) or type the soil data into the User Soils database for each of the map categories prior to creating the project.

11. SWAT Database: Soil cont.

12. SWAT Model Input: Weather
Rainfall, solar radiation, air temperature, humidity and wind speed
Major input for hydrology, sediment and chemical transport ET
Source: Weather station data from each island
Each weather station location will be entered with the corresponding data

13. SWAT Database: Weather cont.

14. SWAT Model Input: Chemicals
Fertilizer and pesticide data
Large number of names of fertilizer and pesticide in the SWAT database
New chemicals can be entered
Allows if manure is used in the application

15. SWAT Database: Fertilizer

16. SWAT Database: Pesticide

17. Discussion