Abstract:
In this study, a spatially distributed parameter model the Areal Nonpoint Source Watershed Environmental Response Simulation (ANSWERS) model has been used to simulate surface runoff and soil erosion in Karso catchment in Bihar, India. The model divides catchment into square elements (grid cells) and uses the connectivity of the cells (derived from slope aspect values) and the continuity equation to route flow to the catchment outlet. The quantity of erosion or deposition occurring within each cell is estimated based on the erodibility of the soil, land cover type of the cell, the rate of flow passing through the cell, and the quantity of sediment in the flow passing through the cell.
The GIS techniques have been utilised for spatial discretization of the Karso catchment in to grids. Model input parameters such as land forms, drainage, soil, landuse/land cover were derived from digital analysis of Landsat Thematic Mapper data with limited ground truth. Information about slope and aspect were generated in a GIS from Survey of India Toposheets. The model predicted hydrographs and sediment graphs within acceptable limits. Besides temporal variation of soil erosion, the model also predicted spatial distribution of soil erosion in the watershed. Based on spatial predictions of the model, the sources of soil erosion have been identified in the watershed. Changes in spatial distribution in sediment production zones with varying rainfall intensities and duration have also been studied and discussed.
