Blog: What is seawater intrusion? A hydrogeologist explains the shifting balance between fresh and salt water at the coast
Seawater intrusion is the movement of saline water from the ocean or estuaries into freshwater systems. The seawater that has crept up the Mississippi River in the summer and early fall of 2023 is a reminder that coastal communities teeter in a fragile land-sea balance. Fresh water is essential for drinking, irrigation and healthy ecosystems. When seawater moves inland, the salt it contains can wreak havoc on farmlands, ecosystems, lives and livelihoods. … In groundwater basins of central and southern California, widespread pumping has caused groundwater levels to drop hundreds of feet in some areas. This is tipping the seesaw and causing groundwater from the sea to move far inland. Accessible groundwater has supported irrigated agriculture in these areas, but now the double hazard of reduced groundwater availability and seawater intrusion threatens crops like strawberries and lettuce.