Investigation of BMPs to control erosion and nutrient losses using SWAT model

The Upper Cauvery Basin faces water quality issues due to sediment erosion and nutrient loss from agricultural non-point source pollution, as cropland dominates the region. Identifying critical source areas (CSAs) is vital for selecting best management practices (BMPs) to mitigate this deterioration. This study used the flow-calibrated SWAT model to identify CSAs and evaluate the effectiveness of structural BMPs - contour farming, filter strips, streambank stabilisation, porous gully plugs and non-structural BMPs - no-till, cover crops, manure incorporation at hydrological response unit (HRU), subbasin, and watershed levels. Simulations showed streambank stabilisation was most effective for sediment reduction at the watershed scale (57.27%), while filter strips reduced sediment significantly at the subbasin (37.91%) and HRU (43.75%) levels and performed best for total nitrogen (TN) and total phosphorus (TP) reduction. Among non-structural BMPs, no-till reduced sediment, and manure incorporation reduced TN and TP. Structural BMPs proved more effective overall than non-structural BMPs.