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

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 o cial Indonesian government websites and direct eld 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 m 3 in January and only 50,001 m 3 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 ow 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 signi cant 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.closest to Tunda Island in Banten Province, is also currently experiencing a freshwater crisis (Kepel et al. 2023).The inhabitants of Tunda Island, which has approximately 276 hectares of land, are divided into two administrative regions: Timur Village (TV) and Barat Village (BV). The population density is 543.5 per square kilometer. Aquaculture and shing are the primary sources of income for the island community. Tunda Island is morphologically classi ed as a reef island with an elevation between 0 and 12 meters, according to the digital elevation model (DEM) data. Geologically, Tunda Island consists of Quaternary reef limestone (Rusmana et al. 1991). Nevertheless, Tunda Island has an aquifer system with low productivity, low-to-high transmissivity, and a discharge greater than 10 L/s (Soetrisno 1986). Material and methods Meteorological dataThe meteorological data for Serang, Banten was downloaded from the Agency of Meteorology, Climatology, and Geophysics of the Republic of Indonesia (BMKG) (http://dataonline.bmkg.go.id/home; accessed in 2015) and the European Center for Medium-Range Weather Forecast (ECMWF) (https://www.ecmwf.int/; accessed in 2023). The climate data combination is composed of total daily rainfall from 1979 to 2022. The data was then further processed to obtain the average monthly precipitation (Fig. 1).Composite analysis (e.g., Yin et al. 2022) was used to determine the effect of El Niño-Southern Oscillation ...