Assessment of spring water vulnerability and hydrogeochemical evolution in the Khulgad micro watershed of Kosi basin, Kumaun Lesser Himalaya, India

Spring water is the lifeline for the mountain communities for drinking, irrigation, and domestic needs. This study focused on the vulnerability of spring water and its geochemical evolution under varying geological conditions. We collected 98 spring samples during pre-monsoon (PRM) and post-monsoon (POM) periods and analysed for major ion chemistry. Among the 18 parameters analysed, pH, NO₃⁻, F⁻, and K⁺ concentrations exceed the permissible drinking water quality limits during PRM period, except F⁻ during POM period. However, the source of Cl⁻ and SO₄²⁻ water types is linked to anthropogenic inputs. The principal component analysis and hydrochemical proxies reveal that NO₃⁻ contamination in spring water is from agriculture via surface runoff, while F⁻ and K⁺ are of geogenic origin. The research shows that the quality of spring water in the head watershed is at risk, and urgent attention is required to prevent the villagers’ consumption of contaminated spring water.