Hydrological Modeling to Identify and Manage Critical Erosion-Prone Areas for Improving Reservoir Life: Case Study of Barakar Basin

In this investigation, an effort was made to model the hydrology and to identify critical erosion-prone areas of the Barakar Basin ($\mathrm{6,293}{\mathrm{km}}^2$) in Jharkhand state, India using the soil and water assessment tool (SWAT). This effort is helpful to select and adopt suitable soil conservation measures to reduce soil erosion. Input data include daily rainfall, and air temperature; and monthly runoff, sediment yield and reservoir inflow data of 5 years. Additional data were the topographical map, soil map, land resource data, and satellite imageries of the study area. The model was calibrated and validated for monthly inflow to the Maithon and Tilaiya Reservoirs for the periods of 1997–1999 and 2000–2001, respectively. In addition, it was also calibrated and validated for monthly runoff and sediment yield from two subwatersheds (Banha and Karso), located within Barakar Basin for the monsoon season of the same period. The calibration and validation results established good agreement (less than 10% deviation) between the observed- and model-predicted values in all cases. The identified critical areas using model-predicted sediment yield were compared with results of a report obtained from the Soil Conservation Department of Damodar Valley Corporation (DVC), Hazaribagh. The erosion class map developed using simulation results matched spatially well with the DVC-prepared map based on sediment yield index. A management plan was developed to treat the subwatersheds with conservation practices. Subwatersheds were divided into seven priority classes for treating them sequentially to reduce reservoir sedimentation rate. In the model, conservation practices were accounted for through curve number, universal soil loss equation (USLE) cover factor, USLE support factor, and farm pond. Adaptation of the management plan resulted in decreased sedimentation rate. The sedimentation rate decreased from the current rate of 0.76 and $4.59{\mathrm{mm}}^3/\mathrm{year}$ to 0.56 and $1.41{\mathrm{mm}}^3/\mathrm{year}$ for Tilaiya and Maithon Reservoirs, respectively. Furthermore, the life of Tilaiya and Maithon Reservoirs increased by 29 and 166 years, respectively. These results suggest that SWAT can be used to identify critical subwatersheds and to develop management plans to control erosion from critical areas by reducing the reservoir sedimentation rate.