Evaluation of the SWAT model for water balance components under changing climatic conditions in the Mahanadi River Catchment, Chhattisgarh

ABSTRACT The Mahanadi River, crucial for water supply in Chhattisgarh and Orissa, requires precise streamflow and water balance modeling for effective management, particularly with the construction of new dams potentially altering streamflow patterns. The Soil and Water Assessment Tool (SWAT) model was utilized to simulate the hydrological processes within the Mahanadi River Catchment in Chhattisgarh. This model incorporated 32 years of precipitation and temperature data (1985–2017) from the Indian Meteorological Department (IMD) and CMIP6 General Circulation Models (GCMs) to simulate 14 gauging stations. The SWAT model was calibrated and validated using monthly streamflow data to ensure accuracy, employing the Sequential Uncertainty Fitting (SUFI-2) algorithm to assess parameter sensitivity and uncertainty. This approach involved evaluating how well the model predictions matched observed data, using metrics such as the percentage of observations within the 95% Prediction Uncertainty (95PPU) band, and assessing the strength of calibration. The results showed that the SWAT model, when using a combination of IMD and CMIP6 data, effectively replicated streamflow observations compared to models that relied on conventional gauging station data alone. This effectiveness was evident during both the calibration (1985–2004) and the validation period (2004–2017) at the Kalma gauging station, which demonstrated strong statistical indicators (NSE = 0.93/0.92, Cal/Val, Basantpur).