Assessment and Prediction of Soil Erosion and its Impact on the Storage Capacity of Reservoirs in the Bharathapuzha River Basin, India

Soil, one of the non-renewable resources on this planet, is being depleted at an alarming rate due to various anthropogenic activities. The effect of soil erosion could range from on-site ecosystem fragmentation to off-site reservoir storage capacity loss. Though soil erosion is caused by various agents such as wind, water, etc., water erosion is the major type. Heavy rainfall during the monsoons and the relatively thin cover of soil over the bedrock aggravates the damage potential of this form of erosion in the state of Kerala, India. Water-induced soil erosion in the Bharathapuzha river basin in Kerala, which is blessed with cultivable land resources and intensive agricultural activities, has been undertaken for quite long and has started impacting agricultural activities, drinking water supply, and reservoir storage capacity in the basin. In this background, this study was taken up to assess the effects of climate and land use–land cover dynamics on soil erosion in the Bharathapuzha river basin over the last three decades. Soil erosion from the river basin was estimated by the Revised Universal Soil Loss Equation (RUSLE), and these estimates were verified with the observed sediment load in the Bharathapuzha river at the Kumbidi river gauging station. The storage capacity loss of some of the reservoirs located in the river basin, estimated by the Integrated Bathymetric Survey (IBS), was compared with the likely storage capacity loss of these reservoirs estimated based on soil erosion from the catchment areas upstream. Soil loss from the river basin for a future period was predicted using projections of future climate under two Representative Concentration Pathways (RCP 4.5 and RCP 8.5) from four regional climate data experiments and future land use–land cover. Annual soil loss estimation maps for 2020 and 2035 under RCP4.5 and RCP8.5 reveal the urgent necessity to plan and implement soil conservation measures in the erosion hotspots, especially in the Malampuzha, Anamala, and Attapady sub-basins.