Groundwater Quality Assessment Based on the Water Quality Index (WQI): A Case Study of Bhaktapur Municipality

Groundwater resources in the Kathmandu valley are under severe stress both in terms of quantity and quality due to the massive extraction of water from groundwater reserves. Regular monitoring of groundwater quality is prominent for the identification and prevention of the associated risks from the contaminants. Water quality index (WQI) is one of the most effective ways for determining groundwater quality as it is a representative value reflecting the composite influence of multiple water quality parameters. The present study aims to use the WQI for determining the groundwater quality of the Bhaktapur municipality. To achieve the aim, 25 wells were selected randomly from the Bhaktapur municipality by considering their spatial coverage and groundwater samples were collected from those sites during the pre-monsoon, monsoon, and post-monsoon period of 2018. 11 physico-chemical parameters that have a significant influence on water quality including pH, total dissolved solids (TDS), total alkalinity, ammonia, total hardness, electrical conductivity (EC), chloride, turbidity, phosphate, nitrate, and iron were determined. The obtained parametric values were compared with the National Drinking Water Quality Standards (NDWQS) and the World Health Organization (WHO) guidelines to assess the suitability of groundwater for drinking purposes. Then, WQI values were calculated by following the weighted arithmetic index method and the water quality status for each well was categorized based on those values. From this study, the overall status of the groundwater quality of the study area was found to be poor. The water quality status for 1.33% of the groundwater samples was known to be excellent, 24% was good, 32% was poor, 13.3% was very poor and the remaining 29.33% was unsuitable for drinking. The reasons for the poor groundwater quality in the Bhaktapur municipality may be due to septic contamination, agricultural percolation, construction and demolition activities, and the direct influx of rainwater in open wells. The findings of this study may facilitate the implementation of proper science-based management strategies that can protect the groundwater resources and prevent further degradation of the resources.