Maya P Bhatt^{1, 2,}, Ganesh B Malla³, William H McDowell^{2, 4}

Drinking water quality reflects both geologic and anthropogenic influences. This study examines drinking water quality in groundwater, municipal supplies, and natural springs of Kathmandu, Nepal. Major ions, trace metals, nutrients, dissolved organic matter, and dissolved silica were analyzed on samples collected twice from ten sites within Kathmandu Valley. Groundwater chemistry is dominated by NaCl, with concentrations Na >> Ca >> Mg > K > NH₄, and Cl >> SO₄ >> NO₃ >> PO₄. This dominance of NaCl in regional groundwater suggests the strong influence of human activities in altering water quality. In natural spring water, Na and Cl were also dominant, but overall concentrations were much lower (346.74 mg/L Cl in groundwater versus 56.10 mg/L in spring water). In municipal tap water, chemical composition is primarily released from natural biogeochemical processes. Trace metals like Al, Ba, Cu, Fe, Mn, V, and Zn were detected in all water systems, while others were below analytical detection limits. Groundwater and natural spring water exceeded WHO guidelines for Na, NO₃, and Fe, while municipal water remained within acceptable limits. Data analysis utilized Bootstrapping with B = 1000 iterations and provided 95% confidence interval estimates for chemical parameters comparing with standard values. A Bootstrapped one-way ANOVA was conducted to compare these parameters across the drinking water systems, highlighting policy-related findings. Additionally, we performed correlation and multiple regression analyses among the chemical parameters, generating a range of predictive models. This study highlights the urgent need to improve water management and infrastructure in the Kathmandu Valley and provides recommendations for policy interventions such as protecting water resources, public awareness, minimize pollution, develop and implement strict regulation and community-based approaches to address these issues. Understanding drivers of variability in urban water quality in developing countries is essential to meeting united nation’s sustainable development goals and protecting public health.

Major Ions, Drinking Water Quality Assessment, Bootstrapping Estimation and Testing, Predictive Techniques, Trace Elements, Dissolved Organic Carbon (DOC), Water Resources Management