Assessing and mapping the groundwater potability in Vallipuram coastal area, Jaffna peninsula, Sri Lanka by weighted arithmetic water quality indexing method

Abstract

Ground water is an extremely valuable resource and pollution of ground water resources is a matter of serious concern. Though more than 80% of people in the Jaffna region, rely on groundwater self-supply wells, the extent to which self-supply wells delivers safe water and the associated risk factors for contamination remain unclear. In response to community requests and the National Water Supply & Drainage Board's (NWS&DB) provision of water from four ground water wells through 150m lateral pipes, a study was initiated to assess quality of well water within a 1.5km radius from the NWS&DB wells. This study involved the evaluation and mapping of groundwater quality parameters and the application of the Water Quality Index (WQI) to determine water potability. The study revealed that numerous parameters, such as turbidity, color, TDS, total hardness, total alkalinity, chloride, fluoride, total iron, calcium, and sulfate concentrations, exceeded SriLankan drinking water standards, while pH, nitrate, nitrite, and total phosphates remained within acceptable limits in all 120 wells. Heavy metals like arsenic and cadmium were absent in all samples. Microbiological results showed contamination with total coliform and E.coli bacteria throughout the study area. Considering physical and chemical parameters, the WQI values ranged from 4.5 to 287.2, with 72 wells suitable for drinking. However, when microbiological parameters were factored in, only three wells were deemed safe for drinking, underscoring the critical necessity for aquifer protection, thorough cleaning, and the immediate implementation of regular well chlorination or disinfection measures tosafeguard the health and well-being of the community.