Managed Aquifer Recharge
This involves artificially recharging the aquifer with freshwater to create a hydraulic barrier that pushes the saltwater interface back toward the sea.
- Injection wells or infiltration basins are used to introduce treated wastewater, stormwater, or imported water.
- Increases freshwater pressure, counteracting the landward flow of saltwater.
- Requires a sustainable source of clean water for recharge and careful monitoring of water quality.
Extraction Barrier Wells
A line of extraction wells is installed parallel to the coast to intercept and pump out intruding saltwater before it contaminates the main freshwater aquifer.
- Creates a localized cone of depression that draws saltwater toward the extraction wells.
- The pumped brackish water must be disposed of, often through desalination or discharge to the ocean.
- Effective for creating a stable freshwater zone but energy-intensive due to continuous pumping.
Injection Barrier Wells
Freshwater is injected through a line of wells to create a high-pressure ridge that physically blocks the advance of the saltwater wedge.
- Forms a permanent or seasonal hydraulic barrier directly against the saltwater interface.
- Often uses highly treated recycled water (e.g., from advanced water purification plants).
- Requires precise engineering and constant management to maintain the pressure ridge.
Optimized Groundwater Extraction
Reducing and strategically relocating pumping wells inland and away from the coast to lower the risk of drawing in saltwater.
- Involves comprehensive modeling of the aquifer to identify safe pumping rates and locations.
- May require developing alternative water supplies to offset reduced pumping near the coast.
- Critical for prevention and is often part of long-term aquifer management plans.
Subsurface Physical Barriers
Constructing impermeable underground walls or slurry cut-off walls to physically block the lateral movement of saltwater.
- Typically used in shallow, unconfined aquifers where the intrusion zone is narrow.
- Construction is complex and costly, often limited to critical, small-scale protection areas.
- Materials include sheet piling, bentonite slurry walls, or subsurface dams.