Hydrogeochemical evolution of spring water in the western lower himalayas: Seasonal changes, quality assessment, and health risks

Spring water serves as a vital freshwater source for Himalayan mountain communities. In order to determine the spring water quality, hydrogeochemical processes, and seasonal changes, thirty-six samples from nine locations in four seasons (2021–2023) were collected and analysed for physicochemical constituents, heavy metals, and stable isotopes (δ¹⁸O and δ²H). The findings demonstrate that a mixture of processes, such as silicate and carbonate weathering through ion exchange and reverse ion exchange processes, regulate the spring water chemistry. The geochemical evolution of spring water is primarily driven by rock weathering, with 86% of the samples exhibiting a Ca.Mg-HCO₃ water type. Most parameters show insignificant seasonal changes except for SiO₂ (p = 0.002), Al (p = 0.007), Co (p = 0.002), Cu (p = 0.00), Li (p = 0.00), Mo (p = 0.00), and Pb (p = 0.00). The isotopic data suggests meteoric origin of spring water, with δ¹⁸O and δ²H values ranging from −8.91‰ to −7.65‰ and −62.7‰ to −51.6‰ (pre-monsoon) and −9.71‰ to −7.86‰ and −63.9‰ to −51.3‰ (post-monsoon), aligning with the local meteoric water line (δ²H = 7.73 × δ¹⁸O+10.45; r² = 0.99). The EWQI and HPI suggest excellent spring water quality in 89%–100% of samples. Among the heavy metals, arsenic poses a potential non-carcinogenic risk in 11%–44% of spring water samples for adults and children. Similarly, arsenic (33%–56%) and nickel (44%–78%) present significant carcinogenic risks, exceeding the acceptable limit of 1 × 10⁻⁴. Overall, the spring water quality is adequate and primarily driven by natural processes, but the levels of As and Ni are in the critical range for human health.