Hydro-chemical characterisation and quality assessment of shallow groundwater in parts of the Kathmandu Valley, Nepal

Abstract

Groundwater is the main source of water for drinking and irrigation in the Kathmandu Valley of Nepal. Although quality of groundwater is crucial for public health, there is little information available. Considering this, groundwater samples were collected during the post-monsoon and winter from 35 dug wells of Lalitpur Metropolitan City located in the Kathmandu Valley. Chemical analysis of these samples has revealed alkaline nature of groundwater. Factor analysis (FA) and correlation analysis (CoA) have identified lithology, geogenic, and anthropogenic activities as the main factors governing groundwater chemistry. Cluster Analysis (CA) segregated samples into five clusters indicating difference in their hydrochemistry. The Weightage Arithmetic Water Quality Index (WAWQI) has revealed unsuitability of groundwater for drinking. Among the chemical constituents, Fe, Ca2+, Mg2+ and PO43− are found most influential. Concentration of iron, and calcium were much higher than the recommended limit for drinking water. High total coliform (TC) content in particular makes groundwater of the valley totally unsafe for drinking. While percentage of sodium (Na%), sodium adsorption ration (SAR), and salinity hazard values of the samples are found suitable, on the basis of the Permeability Index (PI), several winter and post-monsoon samples were unsuitable for irrigation. This study strongly recommends for treatment and purification of groundwater before supply and use for drinking and irrigation purposes to minimise health-risk.