Assessment of a small island’s groundwater resilience under the pressure of anthropogenic and natural stresses on Tunda Island, Indonesia

Abstract

Abstract Groundwater resilience on small islands, especially low-lying carbonate islands like Tunda, is vulnerable to an expanding population, demand exceeding supply, contamination from human and animal waste, and climate change-related impacts. This study aims to evaluate the resilience of groundwater resources on Tunda Island, Banten, Indonesia, in response to anthropogenic activities and climate change-induced consequences. The data were compiled and collected from the official Indonesian government websites and direct field observations. Analysis of climate data reveals that January has the highest average monthly precipitation, with 292.32 mm, while August has the lowest, with 48.26 mm. This is proportional to monthly meteorological water storage, with amounts of 299,547 m3 in January and only 50,001 m3 in August. Typically, the groundwater levels on Tunda Island are higher than the mean sea level, ranging from 1.07 to 8.71 meters with flow direction from the inland (recharge) to the coast (discharge). Population growth from the last decade (2012–2022) and ten drought events caused by El Nino and positive IOD from 1979 to 2022 have not yet had a significant impact on Tunda Island's groundwater resilience. Similarly, the increase in the number of visitors between 2019 and 2021 has had no effect on the island's water security. However, these anthropogenic and natural stresses will inevitably deplete the island's water supply in the future. Hence, water management and planning, including the determination of regional water balances, were required to maintain the water supply and its sustainability.