The Freshwater-Saltwater Interface

07/24/26

“What makes the interface between saltwater and freshwater so unique?”

Freshwater and saltwater have substantially different properties. When they meet in coastal aquifers, they form a Freshwater-Saltwater Interface. The freshwater-saltwater interface is a transition zone where freshwater “floats” as a layer above the zone of transition (which in turn “floats” above more pure saltwater) because of saltwater’s greater density. The further down you go in a coastal aquifer, the saltier the groundwater becomes. Coastal aquifer infrastructure operators must be careful with the freshwater-saltwater interface, because overpumping can lead to upconing of saltwater and result in saltwater intrusion.  

• Earth/Climate science
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