Saltwater Intrusion

Saltwater intrusion is the movement of saline water into freshwater aquifers, which can lead to contamination of drinking water sources and other consequences. Saltwater intrusion occurs naturally to some degree in most coastal aquifers, owing to the hydraulic connection between groundwater and seawater. Because saltwater has a higher mineral content than freshwater, it is denser and has a higher water pressure. As a result, saltwater can push inland beneath the freshwater. Certain human activities have increased saltwater intrusion in many coastal areas, most importantly groundwater pumping from coastal freshwater wells. Water extraction drops the level of fresh groundwater, reducing its water pressure and allowing saltwater to flow further inland. Other responsible influences include navigation channels or agricultural and drainage canals, which provide conduits for saltwater to be brought inland, and sea level rise. Saltwater intrusion can also be worsened by extreme events like hurricane storm surges.