The Vulnerability of Shallow Groundwater on a Small Tropical Indonesian Island

Abstract Small islands depend on rainwater as a source of water. Climate variability affects changes in groundwater chemistry on small islands. Pari Island is one such small island, located in Indonesia, with an area of 41.32 ha and a population of 1,441. This study aims to assess the vulnerability of groundwater quality to climate variability based on observations from Pari Island, including the influence of tourism on groundwater. The study used traditional hydrochemistry analysis methods (Piper, Durof, Scholler, and Gibb’s diagrams), a questionnaire survey, and Standardized Precipitation Evapotranspiration Index (SPEI) analysis. The results indicate a strong correlation between SPEI-2 and the total dissolved solid content of groundwater, demonstrating that two-monthly interval precipitation has an impact on groundwater quality. The hydro chemical analysis of samples taken from dug wells shows that, geographically, the influence of climate variability on Pari Island weakened from west to east, corresponding to patterns related to the direction of the monsoon winds of tropical Indonesia. Increased tourism worsened groundwater vulnerability due to increased water demand and resultant wastewater load.