Time Scale of the Formation of Fresh Groundwater Lens on an Atoll Island under the Influence of Land Reclamation

Abstract

For atolls, fresh groundwater lens (FGL) represents a crucial resource. Land reclamation is a common way of expanding the FGL. However, few studies have examined the effects of land reclamation on the FGL on the time scale. In this study, we are the first to quantify the effect of land reclamation on the time scale of dynamic processes in FGL. It was found that reclamation length and thickness had a much greater effect on fresh groundwater volume and lens stabilization time than the hydraulic conductivity of filling materials. Specifically, the fresh groundwater volume increased 1.18 times, and the lens stabilization time increased 1.12 times for every 1.67-fold increase in reclamation length. Furthermore, enhancing reclamation thickness from 1 to 12 m notably extended the lens stabilization time from over 15 to 46 years. Meanwhile, the effect on fresh groundwater volume diminished with an increasing reclamation length and thickness. Thus, extensive reclamation on atolls may not yield the expected outcomes, leading to high reusability and time costs. This work provides insights into the effects of land reclamation on FGL and evaluates these effects in terms of time. This valuable insight can guide the use of land reclamation to obtain more freshwater resources in a shorter period.