Assessing the effect of heterogeneous land reclamation on saltwater intrusion into unconfined coastal aquifers

Several aquifers worldwide are vulnerable to the serious problem of saltwater intrusion (SI). Groundwater pumping, irregular sea level, and global warming increase SI. Protecting the coastal aquifers is essential, as coastal regions consider groundwater systems to be major freshwater sources. This paper is one of the few that assesses the impact of land reclamation on SI in both homogeneous and heterogeneous aquifers. The study utilizes both laboratory-scale cases and real dimension-scale cases of unconfined aquifers. A pioneering effort was made to explore the effect of heterogeneous land reclamation on SI. Simulation is done using SEAWAT code. The saltwater intrusion length repulsion ratio (RL) and the saltwater intrusion area repulsion ratio (RA) were computed to assess the effect of land reclamation on SI. The results showed that RL and RA increase with the increase of the reclaimed land width ratio (WRL/La). The growth rates of RA were higher for the (WRL/La) value up to 25%. Decreasing the hydraulic conductivity of reclaimed land increases the RL and RA. In case of heterogeneous land reclamation, using the upper layer with low hydraulic conductivity is the proper choice. Furthermore, rising the low hydraulic conductivity upper layer thickness increases the retard of SI. In real dimension-scale case, using heterogeneous land reclamation with a low hydraulic conductivity upper layer comprising 75% of the aquifer depth demonstrated the greatest impact on retarding SI, where using a WRL/La of just 20% results in an RL equals 91.6% and RA equals 68.2%.