Experimental and numerical modeling of sand column applied on recharge reservoir to control seawater intrusion

Abstract

Excessive groundwater exploitation may lead to groundwater depletion, causing groundwater level at the inland lower than sea level and result in seawater intrusion (SWI) in a coastal aquifer. To control the occurrence of SWI, an alternative solution is to increase the replenishment of groundwater using a recharge reservoir. If a recharge reservoir is built in a region with soil hydraulic conductivity below 10-5 cm/s (semi impermeable), then a sand column is usually proposed, put on the bottom of the recharge basin and directly connected to the aquifer layer. The purpose of this study is to analyze the effectiveness of the sand column’s application in the recharge reservoir to control SWI. This research is an experimental study that combines physical and numerical modeling of the recharge basin with sand columns under a laboratory scale. The results of this research are beneficial for field applications because the process that occurs in the recharge reservoir can be determined prior to the real construction in the field. The results of the research are also useful to investigate whether the recharge reservoir is effective or not as a buffer of SWI in coastal aquifers. The expected result is that by using sand columns in the recharge basin, seawater intrusion can be controlled. It is hypothesized that the higher the number of sand column density and water level on the reservoir, the farther the freshwater saltwater interface is pushed toward the sea.

Physical modeling of sand columns application in recharge reservoir to prevent seawater intrusion

“…However, since the piezometric groundwater pressure is greater than the sea level due to groundwater recharge, this pressure can be neutralized, and the flow of water from land to ocean can be balanced by seawater and groundwater (Azis et al 2019). Seawater intrusion occurs when this equilibrium is disturbed, typically caused by a lack of groundwater recharge and heavy groundwater pumping (Azis et al 2020).…”

“…If the seawater has reached a well, the well will become acidic and cannot be used for everyday uses (Bear et al 2010). Therefore, efforts must be made by applying water to the soil, both naturally and artificially, so incorporating water into the soil may be accelerated (Azis et al 2020). A way to artificial groundwater recharge is by infiltration reservoirs that may trap surface runoff.…”