Validation and calibration of SWAT model for Kollur River Basin, Kundapura Taluk, Udupi District, Karnataka, India

The present research work has been carried out for the Kollur River Basin, Kundapura Taluk of Udupi District of Karnataka. Kollur River is tributaries of Chakra and Souparnika Rivers. The problem of seawater getting mixed with underground water tables has become acute in many gram panchayats like Maravanthe and Senapura, located near the seashore. Villages like Vandse and Chittur, situated some distance away from the sea, have another problem on hand. The drinking water sources of these villages have dried up due to the depletion of the water table. To understand the hydrology of this complex landscape, the SWAT-CUP model was calibrated and validated using the SUFI-2, considering 14 important hydrologic parameters based on literature sources. The SUFI-2 tool employs stochastic calibration, which recognizes and expresses model errors and uncertainties as ranges account for all underlying variables, conceptual framework, parameters, and observed values. Our watershed model has eight sub-basins and 126 Hydrological Response Units (HRU) to simulate hydrological processes. Climate data from 2007 to 2021 revealed that the most precipitation occurred from June to September, with a maximum of 789 mm in June and a low of 0 mm in January. The hydrographs of 95 PPU plots were obtained from single iterations (500 simulations). The p-factor and r-factor were found to be 0.15 and 1.59, respectively. The accuracy of the simulation findings between observed and model-generated streamflow values was satisfactory. The SWAT-CUP enhanced streamflow models by lowering parameter uncertainty. It can be concluded that less sensitive parameters require more time to reduce the uncertainty than more sensitive values due to wider confidential intervals.