Prediction of surface runoff and erosion rate using SWAT (soil water assesment tool) model in Selopamioro catchment as directions of soil and water conservation

Selopamioro catchment part of Oyo Watershed, is located in downstream area of Selopamioro village which consist of steep slope gradient, and has been constantly exposed to intensive farming activities. Thus, this watershed is susceptible to erosion. One of models to predict the impact of land use on hydrological and sedimentary conditions is SWAT (Soil Water Assessment Tool). Therefore, the purpose of this research was to apply the SWAT model in predicting surface runoff and erosion. The result of this study will be used as initial analysis to support the direction of soil and water conservation. Topography, land use, and climate data were collected to simulate erosion and surface runoff. Two adjacent sub-catchments namely DTA 1 and DTA 2 were analyzed. Surface runoff in DTA 1 is 333,660,000 liters/year and in DTA 2 is 316,920,000 liter/year. The erosion rate in DTA 1 is 24.6 mm/year and in DTA 2 is 21 mm/year. The result of SWAT model tends to be overestimate. This shows that SWAT model might not suitable to be used for erosion prediction in tropical agriculture country, such as Indonesia. Updates of SWAT data for physical characteristic in tropical country might need to be carried out for reliable result.