Trivariate risk assessment to unlock priorities in agriculture-dominated semi-arid region

This study provides crucial insights into sustainable water resource management in an agriculture-dominated, water-scarce region. The long-term hydrologic potential of the Purna sub-catchment (in India) was simulated using the Soil and Water Assessment Tool (SWAT) under a multimetric calibration approach. A comprehensive evaluation of the SWAT-simulated streamflows, incorporating graphical and quantitative assessments (i.e., R² ≥ 0.82 and NSE ≥ 0.81), parametric sensitivity and uncertainty analyses, revealed the hydrological advantages of the multimetric calibration approach over single-site calibration. We introduce the hydrological efficacy index (HEI), representing the natural resiliency of the watersheds, to identify hydrologically efficient areas using long-term hydrological potential and principal component analysis (PCA). The PCA is used to deal with multicollinearity among hydrological variables. The overall vulnerability of the region to escalating water scarcity is determined using multiple hydrologic and socioeconomic indicators derived from observations, simulations, and census data to establish the vulnerability index (VI). Without watershed-based observations, the simulated water yield at 50 % dependability and census-based population data are used to derive the areal water stress index (AWSI). The trivariate risk analysis of HEI-AWSI-VI indicated that 72.4 % of the study region exhibits moderate to high AWSI and VI, with only 37.9 % displaying high HEI. The top 16 priority-ranked watersheds, identified using the analytic hierarchy process (AHP) and modified technique for order preference by similarity to ideal solution (TOPSIS) methods, would bring substantial benefits under sustainable water management practices, covering 60.8 % of the area and 75.6 % of the population. This study underscores the critical need for implementing comprehensive water conservation practices and strategic resource management to enhance resilience against escalating water scarcity.