Saltwater intrusion

Saltwater intrusion is the movement of saline water into freshwater aquifers, commonly when groundwater pumping or drought lowers freshwater pressure. It can make groundwater unsuitable for drinking and irrigation.

Ghyben–Herzberg relation: A hydrostatic approximation relating freshwater depth below sea level to freshwater head above sea level in a coastal aquifer. It estimates how lowering freshwater head raises the freshwater–saltwater boundary.
Seawater intrusion in the Gaza Strip: The advance of seawater and saline groundwater into the heavily used coastal aquifer beneath the Gaza Strip. It illustrates severe intrusion where intensive extraction and limited recharge coincide.
Electrical resistivity tomography: A geophysical imaging method that estimates subsurface electrical resistivity from measurements made at the surface or in boreholes. Saline groundwater is conductive, so resistivity images can reveal its extent.
Groundwater salinization: An increase in dissolved salts in groundwater from natural or human-driven sources. Saltwater intrusion is one pathway by which groundwater becomes more saline.
Saltwater wedge: A wedge-shaped body of saline water that extends inland beneath freshwater in a coastal aquifer. Its position and shape describe the classic pattern of coastal intrusion.
Chennai aquifer: A coastal groundwater system beneath Chennai, India, affected by seawater intrusion and freshwater extraction. Its coastal wells show how urban demand can pull saline water inland.
Chloride in groundwater: Chloride concentration is a common indicator of salinity in groundwater samples. Rising chloride can provide an early warning of saline water reaching wells.
Drinking water quality: The chemical, physical, and microbiological characteristics that determine whether water is suitable for drinking. Elevated salinity can make an aquifer’s water unacceptable for drinking.
Groundwater pumping: The extraction of water from an aquifer through wells. Pumping lowers freshwater pressure and can draw saline water toward wells.
Biscayne Aquifer: A shallow, highly permeable limestone aquifer in southeastern Florida that supplies much of the region’s freshwater. Its porous coastal geology makes saltwater intrusion a major water-supply concern.

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