Would mixed physical barriers be able to desalinate coastal aquifers from seawater intrusion under pumping conditions?

This study used the SEAWAT model to investigate the potential of using mixed physical barriers (MPB) to control SWI under pumping conditions in typical homogenous and layered heterogeneous coastal aquifers. The numerical models were based on controlled two-dimensional (2D) laboratory tests and field studies in the Biscayne aquifer, which is situated in the Cutler Ridge region close to Deering Estate, Florida, USA. The modelling results revealed critical insights into SWI behaviour under pumping conditions. Specifically, it was observed that the intrusion wedge extended significantly further inland in layered heterogeneous aquifers and homogeneous aquifers compared with the base case without pumping. Results showed that coastal aquifers with bottom low-hydraulic conductivity have smaller SWI compared with top and middle-layered aquifers. The SWI repulsion reached 27% by installing the MPB, while the groundwater salinity increased to 3%, 38% and 121% by increasing the abstraction well rates by 10 m 3 /day, 15 m 3 /day and 20 m 3 /day, compared with no pumping after using the MPB. The current study results are very interesting for coastal aquifer management and require economic study to ensure the feasibility of using this method. • Layered coastal aquifers have high desalination rates compared to homogenous cases. • Aquifers with low-k at the bottom showed smaller SWI compared with cases low-k at the top and the middle. • Desalination reached +27% after installing the mixed physical barrier. • Groundwater salinity changed by +25%,-0.30% and −60% with pumping 10, 15 and 20 m 3 /day.