Experimental Investigation to Assess the Efficiency of Subsurface Barrier in Heterogeneous Aquifer With a Sloping Ocean-Aquifer Boundary

Abstract

Seawater intrusion is an ongoing issue exacerbated internationally by the growing need for freshwater along coastlines, which is affected by shifting sea levels and changing climates, challenging sustainable management. This research primarily focuses on determining intrusion behaviour within a sloping boundary in a heterogeneous aquifer and assessing the efficiency of subsurface barriers. The glass-box method was incorporated with an inclined permeable barrier. High-resolution images were taken at defined intervals and enhanced for clear intrusion visuals. Comparing the results of the heterogeneous base case and barrier installed condition, a huge quantity of about 38.93% of groundwater was conserved from being contaminated. Homogeneous media shows a faster rate of intrusion with a progressive rate of contamination, while heterogeneous media, without barrier, shows slower rates of intrusion due to reduced permeability. Longitudinal dispersivity as 0.5 cm and transverse dispersivity as 0.05 cm were considered. The Péclet number was calculated as 3, which comes under the range defined in the literature. Sensitivity analysis for the height of the barrier shows that a higher height is required for remediation by heterogeneous media of higher permeability. Analysis of the toe length using sensitivity analysis in the heterogeneous case shows a range of 24.82 to 75 cm before barrier installation and a range of 13.05–65.24 cm after installation of a barrier (15, 20, and 25 cm height). This implies that a higher toe length had formed with a smaller barrier height, and lower efforts were required for backwashing.