ANTHROPOGENIC IMPACTS OF TOURISM TO KARST ENVIRONMENTS IN THE PHILIPPINES

Tropical karst is highly sensitive to surface and subsurface changes, with natural and anthropogenic factors contributing to its potential degradation and overexploitation. Thus, the appropriate management and protection of karst environments are needed. This study aims to determine the anthropogenic-driven changes in the karst landscape and groundwater resources of El Nido, Palawan Province. Interferometric Synthetic Aperture Radar (IfSAR), LandSat 8, and Google Earth imagery were used for pre-field geomorphological and land cover delineation. Semi-detailed stratigraphic surveys and rock sampling were conducted. In-situ water quality testing and sampling were done to obtain physicochemical parameters such as pH, conductivity, and total dissolved solids. Focusing on preliminary findings from El Nido, petrographic characterization and microfossil age dating have shown that the limestone is composed of Middle Permian faunal assemblage. Geomorphological analysis shows that the area is dominated by karst towers, remnant valleys, sinkholes, and caves. Georesistivity surveys reveal that the water-saturated layer becomes thicker in the extensive floodplains of Villa Libertad, Dewil Valley, and Villa Paz. In contrast, the town center has a thin and permeable water-saturated layer that is approximately 2-3 m thick. Fecal coliform, nitrates, and sulfates are relatively higher in groundwater collected from karst areas in the urban and tourism center.