<p>This study presents an integrated methodological framework for identifying potential freshwater source locations on data-limited small islands by combining Geographic Information Systems (GIS), the Soil and Water Assessment Tool (SWAT), and the Factor Index Method. The analytical workflow begins with processing spatial data (topography and land use) in a GIS environment to delineate initial watersheds. These inputs are then coupled with the SWAT model to simulate key hydrological output variables, such as surface runoff and stream network geometry, without requiring extensive historical streamflow data. The simulated outputs are subsequently reintegrated into the GIS environment to derive spatial attributes for each sub-basin. Subsequently, the Factor Index Method is applied to evaluate and rank the sub-basins using five key criteria: watershed area ratio, stream length ratio, slope, land use, and location accessibility. The analysis identified eight optimal sites, with field surveys confirming that four of these locations closely aligned with natural stream networks and existing spring-fed ponds. The results demonstrate that this approach can accurately delineate hydrological features and prioritize monitoring locations without extensive field data. By validating geospatial predictions through 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.</p>