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Groundwater quality evaluation for drinking purpose using water quality index in Kathmandu Valley, Nepal



Groundwater is a significant source of drinking water in Kathmandu Valley of Nepal. The study aims to evaluate the groundwater quality in terms of water quality index. We compared the physicochemical and microbial parameters of 159 groundwater samples. The study showed that conductivity, hardness, chloride, and nitrate were found to be significantly higher in well water and ammonia was found to have significantly higher concentrations in boring water. The Spearman’s rank correlation coefficient demonstrated a positive correlation between conductivity and hardness, turbidity and iron, total hardness and chloride, and ammonia and arsenic. The drinking water quality parameters including pH, conductivity, turbidity, chloride, hardness, iron, ammonia, total coliform, and Escherichia coli count exceeded National Drinking Water Quality Standards, 2022 by 7.55%, 22.01%, 50.94%, 1.26%, 3.77%, 69.81%, 41.51%, 93.71%, and 47.17% samples, respectively. The water quality index showed that 38.36% of groundwater samples fall under grade-E which requires proper treatment before use. Linear regression revealed that with the increase in turbidity and iron, the water quality index also increases. The principal component analysis identified hardness, iron, conductivity, and nitrate as the major variables governing groundwater quality with no significant difference between well and boring water. Results suggest an urgent need for appropriate treatment of groundwater to mitigate pollutants.