Estimating Subsidence Induced by Groundwater Abstraction in A Tropical Coastal Alluvium Aquifer

The coastal areas of Indonesia, especially along the northern coast of Java, are experiencing increasing land subsidence as a result of excessive groundwater abstraction, driven by population growth and economic development. Groundwater extraction from coastal aquifers has been associated with soil compaction, leading to subsidence and worsening flood risks due to rising sea levels. Pekalongan, a rapidly growing urban area, highlights these issues, with groundwater levels reportedly falling below safe limits. This study investigates the relationship between groundwater withdrawal and land subsidence, aiming to inform sustainable water management practices and mitigation strategies.
The research combines MODFLOW-2005, three-dimensional groundwater flow model with Subsidence (SUB) package to simulate groundwater dynamic and subsidence in the study area. Findings indicate that groundwater abstraction significantly contributes to land subsidence, with compaction concentrated in clay-rich areas at certain depths. Additionally, the study highlights the compounded effects of land use change and climate change on groundwater recharge, although these factors did not show a significant impact on subsidence within the study area.
Model projections suggest that, in the absence of intervention, subsidence will continue, further exacerbating flood risks. To mitigate these risks, the study proposes a comprehensive strategy focused on controlling groundwater abstraction, transitioning toward increased reliance on surface water, and implementing regional policies tailored to the unique characteristics of local aquifers. Furthermore, the research emphasizes the importance of integrated approaches that combine numerical modelling and remote sensing techniques to enhance the management of coastal aquifers and protect vulnerable regions from the adverse impacts of subsidence.