Soil Water Assessment Tool (SWAT) Model Input Assefa Melesse

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

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

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

SWAT Database

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

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

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

SWAT Model Input: Land cover cont.

SWAT Model Input: Soil Runoff, infiltration, sediment and anion exchange 1: 5M vector (Source: http://www.isric.nl/) 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.

SWAT Database: Soil cont.

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

SWAT Database: Weather cont.

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

SWAT Database: Fertilizer

SWAT Database: Pesticide

Discussion