Evaluating Surface Water–Groundwater Interactions and Water Quality in the Indravati River Basin Using Conceptual and MCDM Models

Water resources worldwide are increasingly stressed due to population growth, urban expansion, climate change, and land use changes. Fertilizers, irrigation runoff, wastewater, and industrial pollution notably impact the Indravati River basin in India. This study addressed the critical gap in previous research by developing a hydrological and water quality model using QSWAT and performing uncertainty analysis through global sensitivity analysis (GSA). GSA, conducted using the SWAT-CUP with the SUFI-2 algorithm, identified key sensitive parameters, including Manning’s n for the main channel, soil water capacity, and curve number for moisture condition II. Model validation indicated strong performance, with R2 values ranging from 0.78 to 0.84 and NSE values between 0.77 and 0.81, demonstrating good alignment with observed streamflow and water quality data. QSWATMOD was subsequently applied to assess the surface water-groundwater (SW-GW) conditions by addressing the limitations of the previous research. Additionally, twenty-five subwatersheds were prioritized using novel SWAT-integrated multicriteria decision-making (MCDM) ensemble techniques, including SWAT–BayBWM-FuzVIKOR, SWAT-VIKOR, and SWAT-SAW, based on water quality criteria. The hybrid SWAT–BayBWM-FuzVIKOR model outperformed the other methods based on the proportion of changes (PoCs) and severity of changes (SoCs), demonstrating superior capability in capturing the complex, nonlinear dynamics of the basin. These findings in this research provide valuable insights for guiding targeted conservation and remediation efforts across any river basin under study.