Hydrogeology of the small island: a case study of Pisang island, West Coast Regency, Lampung province

Abstract

Pisang Island has an area of 1.5 km2. The issue on small islands pertains to the quality and quantity of water. This is related to an increasing population and growing water demand. This research aims to address the sustainability of water resources. Therefore, a hydrogeological concept is required to assess and predict potential water resources to maintain the quality and quantity of water. The methodology used in this research includes geological mapping, measurement of rock resistivity, hydrometeorological analysis, and water quality testing. The research indicates that the lithologies of Pisang Island calcareous gravelly sand, calcareous sandstone, and porous limestone. The aquifer system on Pisang Island is unconfined. The aquifer was spread throughout the island with varying thicknesses. The lithology of calcareous gravelly sand is found in the island’s northern part, with a thickness ranging from 15 to 90 m. Calcareous sandstone is located in fold slopes of 3 to 5 m thickness. Porous limestone is distributed across the island, with a 30–170 m thickness. Pisang Island has an annual rainfall of 3,101.93 mm/year, evapotranspiration of 2,017.91 mm/year, and infiltration of 511.23 mm/year. The groundwater flow pattern moves from high elevations in hilly areas to low elevations in coastal areas.