Saltwater Intrusion and the Biscayne Aquifer: What It Means for Miami's Tap Water
Saltwater intrusion is seawater seeping inland underground and mixing with the fresh groundwater in the Biscayne Aquifer, which supplies most of Miami-Dade's drinking water. The USGS has mapped how far it's spread, and Miami-Dade County says rising demand, population growth and sea-level rise all add to the risk. Utilities manage it with wellfield monitoring and canal controls, and your tap water stays treated to drinking water standards.
Why the Biscayne Aquifer Is Exposed
The Biscayne Aquifer is shallow, porous limestone, often just a few feet below the surface, and it's open to the ocean along the coast. Fresh rainwater pushes back against seawater. When the water table drops from drought or heavy pumping, or when sea level rises, the boundary moves inland. The USGS calls saltwater intrusion a major concern for the roughly 2.5 million people who rely on the aquifer.
What's Being Done
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Monitoring. The USGS and the county track the inland edge of saltwater with monitoring wells and publish updated maps.
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Canal control structures hold fresh water higher inland so it pushes back against seawater.
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Alternative sources. The Hialeah RO plant and NMB Water treat brackish Floridan Aquifer water with reverse osmosis.
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Conservation. Miami-Dade's Water Use Efficiency Plan, irrigation limits and fixture rebates reduce pumping on wellfields.
What It Means for Your Tap Water
Utilities don't send salty water to homes. Affected wells get pulled from service or the water gets treated. Over the long term, saltwater intrusion can mean costlier treatment, new water sources and changes in your water's mineral content. Private wells near the coast are more exposed, since no utility monitors them.
What You Can Do
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Save water: shorter showers, fixing leaks and efficient irrigation all help.
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Protect your plumbing from hard, mineral-rich water with softening.
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On a well, test it. Rising chloride or sodium is an early warning sign.
See the benefits of water softening.
Common Questions
Is Miami running out of fresh water? Not today, but saltwater intrusion and growth are long-term pressures, which is why the county pushes conservation and utilities are adding deep-aquifer RO.
Will my tap water taste salty? No. Utilities don't deliver water that exceeds drinking water standards.
What is the Biscayne Aquifer? It's a shallow limestone aquifer under Miami-Dade and Broward counties, and the main source of drinking water for most of Miami-Dade.
What causes saltwater intrusion? Heavy pumping, drought and sea-level rise lower fresh groundwater pressure, letting seawater push inland underground.
Does saltwater intrusion affect private wells? Yes. Coastal private wells are more exposed because no utility monitors them. Rising chloride or sodium in a test is an early warning sign.
Can reverse osmosis remove salt from water? Yes. RO removes most dissolved salts, which is why utilities use it to treat brackish water.