Impact on well water quality due to seawater intrusion and anthropogenic activities in Oluvil, Sri Lanka

Abstract

Groundwater wells are vital for meeting the daily water needs of rural and coastal areas, particularly in Oluvil village, Sri Lanka. The extraction of groundwater from shallow aquifers, mainly through dug wells along the east coastal sands, has raised concerns about challenges such as seawater intrusion and anthropogenic activities that can impact water quality. This research addresses the gap in understanding well water quality in Oluvil by conducting a comprehensive study encompassing physical, chemical, and biological parameters. Utilizing a combination of quantitative and qualitative methods, the study established fifteen sampling stations at varying distances from the sea (<100m, 100 – 300m, 300 - 500m). A questionnaire survey was conducted to gather demographic and area-related data. The findings revealed diverse water qualities associated with the distance from the Oluvil Sea. Wells located at a 300 - 500m distance exhibited slightly elevated levels in mean temperature (27.4⁰C), mean pH (7.35), mean electrical conductivity (0.45 ms/cm), mean total dissolved solids (213.07 mg/L), mean hardness (197.67 mg/L) and mean alkalinity (196.33 mg/L). A higher salinity level (0.21 PSU) was recorded within the 300 - 500m distance compared to <100m and 100 - 300m. E. coli and total coliform bacteria were recorded in most of the wells making those waters unsuitable for human consumption. The well water in Oluvil is not suitable as a potable water source. Long term use of saline well water for irrigation may cause salt deposition in agricultural lands. These results emphasize the need for effective water management practices to ensure the well-being of public health, agriculture, and the environment in the Oluvil region.