Hydrological Simulation and Uncertainty Analysis using SWAT Model on Mahan River Basin, Surajpur, Chattisagarh

Abstract

Soil and Water Assessment Tool (SWAT) and SWAT-CUP are semi-distributed, process-oriented models that accurately replicate the hydrological cycle in large and complex watersheds and calibrate the results. The objective of this study is to assess the effectiveness of the SWAT model and SWAT-CUP software for hydrological analysis, evaluate the uncertainty associated with the SWAT model, and analyse runoff. This model delineates the basin into five sub-basins and 200 hydrological response units. The model calibration and validation were performed with the SUFI-2 algorithm for the periods 2012 to 2017 and 2018 to 2020 respectively, incorporating a two-year warm-up phase. The sensitivity analysis indicates that, ESCO, ALPHA_BF, SOL_BD, SFTMP, CN2, and SOL_AWC are the six parameters affecting the hydrological process. This aspect is essential in assessing output runoff. Among these characteristics, SCS-CN and ALPHA_BF were identified as the most sensitive variables. The calibration results from 2012 to 2017 provide exceptional outcomes, with R2, PBIAS and NS values of 0.94, 0.89, 14.9 and 0.93, respectively. The validation phase from 2018 to 2020 demonstrates commendable results for the same model, producing values of 0.92, 0.86, 19.4 and 0.91, respectively. Twelve parameters were established during calibration, which are essential for runoff modeling in the designated region. A thorough comprehension of hydrological processes and the identification of pertinent parameters are crucial for developing a simulation model. SWAT and SWAT-CUP were chosen over alternative models primarily due to their superior capability in uncertainty assessment, which enhances the reliability of hydrological simulations and informs future decision-making in the selected watersheds.