Geographic Mapping of Tube Wells and Assessment of Saltwater Intrusion in the Coastal Areas of La Union

Abstract

A large number of coastal aquifers are threatened by saltwater intrusion. Over-abstraction due to high demands for domestic water supply is the main cause of saltwater intrusion. This can also be accelerated by the rise in sea level due to climate change and global warming. This reduces the fresh groundwater resources. With the impact of sea level rise and over-pumping combined together, the problem becomes even more serious. A large part of the province of La Union in the Ilocos Region, Northern Philippines is lying along the coastline, with its community stakeholders depending on wells for their source of water. Considering the safety of users, the study aimed to determine the incidence of saltwater intrusion in the coastal communities of La Union. In this study, the descriptive-qualitative research design was used. A questionnaire was formulated to determine the perceptions of the community stakeholders on the quality of water they are using but their responses were verified by the use of salinity meter to test the actual water salinity from the tube wells. Through the use of handheld Global Positioning System (GPS), the geographical coordinates depicting the location of the wells included in the study were identified. There was a total of 42 barangays selected as study sites. Using quota sampling, a total of 420 tube wells were subjected to analysis. A geographical map of tube wells showing the affected areas served as an output of the study. The research revealed that salt intrusion already exists into tube wells along coastal areas of La Union. Community stakeholders had already resorted to other sources/means for their water consumption.