That's the good news. The bad news is once salt water gets into a well it is even slower to get out. It has been aided by development that drained lands from the coast to the lip of the Everglades and lowered water tables. Storm water that once seeped into the earth and bolstered the flow of fresh water from west to east now rolls off concrete and asphalt into drains that send it directly into the sea. At the same time, fresh water is siphoned out of the ground and sent to faucets and showerheads for an ever-growing number of homes and businesses cramming into South Florida.
Salt water can move inland in a uniform wedge.
Denser than fresh water, it displaces ground water by sliding under it. The invader crawls fastest through the most porous portions of the Biscayne Aquifer, where that limestone sponge is most absorbent. Saltwater intrusion has long threatened public water wells. In 1988 four Hallandale Beach wells were closed and two shelved for emergency use only, said the town's deputy director of public works, David Pritchard. During the 1971 drought, saltwater intrusion cost Miami-Dade County some wells, Burns said.