Abstract:
The soil and water assessment tool (SWAT) is a widely used hydrological model that
evaluates the effects of land management practices on water, sediment and
agricultural chemical yields within large and intricate watersheds. This study aimed
to configure the SWAT+ model in QGIS interface for the Endane model catchment in
Rathnapura. A land use map of the study area was produced using Google Earth Pro.
The catchment area of 720 ha included 67.25% forest cover, 24.56% home gardens
and 7.24% tea lands as the major land use types. Daily rainfall and maximum and
minimum temperatures were collected as weather data formatted into a text file for
SWAT model input. In order to create a soil properties map for SWAT model input,
52 soil samples were collected using the grid sampling method, representing the
different land uses of the study area. The soils were analyzed for pH, electrical
conductivity (EC) and bulk density. Inverse distance weighting (IDW) and Kriging
interpolation techniques were employed to map the soil properties with IDW
interpolation determined to be the most effective technique based on the RMSE and
MAE values in the Endane area. The soil in the forest region was acidic with very
low EC levels, while home gardens showed higher EC levels compared to other land
uses. These results indicated that different land uses exhibit varying EC and pH levels.
The input files developed from this research will support the configuration of the
SWAT model for the Endane watershed.
