Identifying Water Source Locations on a Data-Limited Small Island Using GIS and the Factor Index Method

This study presents an integrated methodological framework for identifying potential freshwater sources on data-limited small islands by combining Geographic Information Systems (GIS), the Soil and Water Assessment Tool (SWAT), and the Factor Index Method. The approach was applied to Sichang Island, Thailand, where five criteria?watershed area ratio, stream length ratio, slope, land use, and location accessibility?were used to assess and rank suitable locations for water gauge monitoring stations. The analysis identified eight optimal sites, with field surveys confirming that four of these locations aligned closely with natural stream networks and existing spring water ponds. The results demonstrate that this approach can accurately delineate hydrological features and prioritize monitoring locations without extensive field data. By validating geospatial predictions with ground-truthing, this framework reduces the need for costly and time-consuming fieldwork. It enhances planning precision, supports efficient resource allocation, and can serve as a replicable model for sustainable water resource management on other small islands with similar data constraints.