Underground Barrier Wall Evaluation for Controlling Saltwater Intrusion in Sloping Unconfined Coastal Aquifers

Abstract

Barrier walls are considered one of the most effective methods for facilitating the retreat of saltwater intrusion (SWI). This research plans to examine the effect of using barrier walls for controlling of SWI in sloped unconfined aquifers. The sloping unconfined aquifer is considered with three different bed slopes. The SEAWAT model is implemented to simulate the SWI. For model validation, the numerical results of the seawater wedge at steady state were compared with the analytical solution. Increasing the ratio of flow barrier depth (db/d) forced the saltwater interface to move seaward and increased the repulsion ratio (R). With a positive sloping bed, further embedding the barrier wall from 0.2 to 0.7 caused R to increase from 0.3% to 59%, while it increased from 1.8% to 41.7% and from 3.4% to 46.9% in the case of negative and horizontal slopes, respectively. Embedding the barrier wall to a db/d value of more than 0.4 achieved a greater R value in the three bed-sloping cases. Installing the barrier wall near the saltwater side with greater depth contributed to the retreat of the SWI. With a negative bed slope, moving the barrier wall from Xb/Lo = 1.0 toward the saltwater side (Xb/Lo = 0.2) increased R from 7.21% to 68.75%, whereas R increased from 5.3% to 67% for the horizontal sloping bed and from 5.1% to 64% for the positive sloping bed. The numerical results for the Akrotiri coastal aquifer confirm that the embedment of the barrier wall significantly affects the controlling of SWI by increasing the repulsion ratio (R) and decreasing the SWI length ratio (L/La). Cost-benefit analysis is recommended to determine the optimal design of barrier walls for increasing the cost-effectiveness of the application of barrier walls as a countermeasure for controlling and preventing SWI in sloped unconfined aquifers.

Integrating numerical modelling and scenario-based sensitivity analysis for saltwater intrusion management: case study of a complex heterogeneous island aquifer system

“…The increase in barrier wells (BWs) was also helpful in controlling the SWI. Armanuos et al ( 2020 ) studied how the BWs control SWI in sloping unconfined aquifers and found that BWs are very effective in facilitating the retreat of SWI in coastal aquifers. Similarly, our results also indicate that SWIs are controlled by adding BWs.…”

Verification of experimental saltwater intrusion interface in unconfined coastal aquifers using numerical and analytical solutions

“…Therefore, proper management and understanding of coastal aquifers are crucial components of global water security. Comprehensive numerical models, such as SUTRA (Voss & Koch, 2001), SEAWAT (Guo & Langevin, 2002), and FEFLOW (Diersch, 2013), have been developed to simulate the SWI under various conditions (Armanuos et al, 2019(Armanuos et al, , 2020a(Armanuos et al, , 2020bGuo et al, 2020;Gao et al, 2021;Abdoulhalik et al, 2021).…”

Large-Scale Physical Modeling of Salt-Water Intrusion

“…Seawater intrusion in coastal aquifers is a worldwide problem caused, among other factors, by aquifer overexploitation related to human activities, such as irrigation and drinking water supply, and the reduction in natural groundwater recharge due to climate change [1]. To prevent or limit the deterioration of both surface water and groundwater quality due to salt-water contamination, research studies have been developed to fully comprehend the problem and identify its fundamental parameters, as well as to evaluate possible countermeasures, such as cut-off walls (e.g., [2][3][4][5][6][7][8][9][10][11][12]).…”