Assessment of Groundwater Quality in the Kathmandu Valley: A Spatial and Physicochemical Analysis

DOI: https://doi.org/10.46610/JoEES.2025.v010i03.005

Abstract

This study investigates the spatial distribution and quality of groundwater utilized by Kathmandu Upatyaka Khanepani Limited (KUKL) in the Kathmandu Valley, Nepal. A total of 60 groundwater samples were analyzed for key physicochemical parameters, including hardness, ammonia, arsenic, chloride, iron, nitrate, phosphate, pH, dissolved oxygen (DO), and E. coli, using geospatial interpolation techniques such as inverse distance weighting (IDW). The findings reveal significant spatial variability in groundwater quality across the valley. Hardness levels ranged from 45.28 to 279.47 mg/L, all within Nepal’s drinking water quality standards (NDWQS) limit of 500 mg/L, though localized high hardness posed aesthetic concerns. Ammonia concentrations varied from 0.1 to 3.0 mg/L, with many areas exceeding the NDWQS limit of 1.5 mg/L, particularly in urban zones like Kathmandu Metropolitan and Bhaktapur Municipality. Arsenic levels ranged from 0.35 to 1.5 mg/L, far exceeding the NDWQS threshold of 0.05 mg/L in parts of Kathmandu and Lalitpur Metropolitan areas, posing severe health risks. Chloride concentrations (0.0038–63 mg/L) and nitrate levels (5–37 mg/L) generally complied with NDWQS limits of 250 mg/L and 50 mg/L, respectively, but localized hotspots highlighted potential usability and health concerns. Iron concentrations (0.15–7.5 mg/L) exceeded the NDWQS limit of 0.3 mg/L in several areas, causing aesthetic issues, while phosphate levels (0.025–1.0 mg/L) surpassed the 0.5 mg/L limit in hotspot regions, contributing to eutrophication risks. DO levels (4.3–10 mg/L) indicated good oxygenation in most areas, though low DO (<5 mg/L) in eastern parts signaled organic pollution. Notably, no E. coli contamination was detected in any of the samples. The predictive accuracy of the IDW model was validated with high R² values (0.53–1.00) and low mean absolute percentage errors (MAPE: 0.56–17.35%). These findings emphasize the need for targeted interventions, stricter regulatory enforcement, and enhanced monitoring to ensure sustainable groundwater management, protect public health, and preserve ecological integrity in the Kathmandu Valley.