Hydrogeochemical study and water quality evaluation of the Suru River Basin in the semiarid, high-altitude region of Kargil, Ladakh (India)

To understand the spatiotemporal variation in water quality, assess its suitability for domestic and agricultural use and identify the geochemical processes governing the Suru River Basin in Kargil, Ladakh, water samples were collected during 2023 across three hydrological periods: the early, peak and late snow- and glacier-melt seasons. The river water was alkaline (pH 8.1-8.7) and classified as slightly hard to moderately hard. The ionic composition followed the order Ca2+ >> Mg2+ > K+ > Na+ and HCO3- > SO42- > Cl- > NO3- > F-. Piper and Durov plots indicated a transition in hydrochemical facies from Ca2+-Mg2+-Cl--SO42- upstream to Ca2+-Mg2+-HCO3- downstream. Water quality indices showed poor to unsuitable for drinking, whereas irrigation suitability indices indicated its suitability for agricultural use. Heavy metal concentrations remained within permissible limits. Multivariate analyses highlighted the combined influence of natural weathering, seasonal discharge fluctuations and anthropogenic inputs on river hydrochemistry. Among the machine-learning models evaluated, Random Forest showed the highest predictive accuracy (R2 ≈ 0.999) with the lowest error metrics. Feature-ranking methods identified temperature as the most influential predictor of the Water Quality Index. These findings provide a valuable baseline for future monitoring and sustainable water resource management in the Suru River Basin.