Water is crucial for life; we’d only survive a few days without it. Our bodies use this magic ingredient for all sorts of essential functions, and 55 to 60% of our flesh and blood is water.
Yet, in a recent survey, 95% of residents in Miami-Dade and Broward counties didn't know the source of their drinking water. If you’re part of that vast majority, you may be wondering, where does the water in your faucet come from? And the answer is just below your feet: an underground reservoir of freshwater recharged by the Everglades.
If you live in Miami-Dade, Broward, Monroe, or parts of Palm Beach County, a vast subterranean world links us to the River of Grass. Unfortunately, 50% of the Everglades has been drained, while alterations to hydrology, pollution, invasive species, and climate change threaten what remains. Efforts to restore the Everglades are underway to help secure our drinking water and clean water economy. Keep reading to learn more about how water flows, seeps, and pours from the River of Grass to your tap.
The Biscayne Aquifer in a Nutshell
State map showing the spatial extent of the Biscayne Aquifer (in pink) in southeastern Florida. The water supply in this region is predominantly collected by pumping just a few feet below the ground in a highly porous layer of limestone called the Biscayne Aquifer, which covers of all Miami-Dade County, almost all of Broward County, and the southeast portion of Palm Beach County. It also covers part of Monroe County.
Millions of residents and tourists in South Florida rely on freshwater pumped from the Biscayne Aquifer and more than 300 million gallons of water are pumped out of this aquifer every day. That would cover nearly 700 football fields in one foot of water! More than half of this water is used for drinking and bathing, while an additional 12% is used for landscaping and recreation. This freshwater is also used for agriculture and other industries.
If your memories of Earth Science class are a little fuzzy, aquifers are underground water-bearing layers that hold and transfer water to wells. This underground water is called “groundwater.” In fact, more than 98% of available freshwater is groundwater. Some aquifers can be recharged directly from rainfall, while others are covered by impermeable layers and recharged through underground sources of water from other areas.
The Biscayne Aquifer has an average thickness of about 80 feet and can receive water directly from the surface. It has large, interconnected voids that store and allow water to pass through. So, when a drop of water hits the ground, it not only infiltrates quite quickly but also has the freedom to move around the limestone base. If you have a well, you are probably drinking that same drop of water that recharged the aquifer some time ago. Because of the shallowness of the Biscayne Aquifer, interactions with the surface water and groundwater determine our water supply.
Rest & Recharge: The Everglades’ Outsized Role in the Biscayne Aquifer
If a drop of water falls on the Everglades, and no one is around to see it, does it make a
splash?
You may never have wondered about the destiny of a rainwater droplet, but the moment it falls in the Everglades, it has three distinct paths. It can either evaporate and return to the atmosphere, flow through the River of Grass to the estuaries, or infiltrate the soil. If it lands on the soft mud of the River of Grass, it ultimately fills in voids in underground rocks and recharges the Biscayne Aquifer. Because the aquifer is highly porous, rainfall over the Everglades continuously recharges it. Florida is one of the rainiest states in the U.S., receiving an average of 50 to 60 inches per year. With its unique porous soil and rock, water from the Everglades doesn't just seep into the aquifer, it pours down, and the groundwater responds quickly to rain falling over the Everglades.
If a drop of water falls over Miami, however, it has a very different fate. Urban areas are mostly covered by impervious surfaces such as concrete, houses, and roads, so water falling here usually evaporates or flows into canals and eventually the ocean. Also, since urban areas here are flat, they can be easily flooded, and dumping the water out of the cities as quickly as possible is often the best option. Because of this, groundwater recharge by rainfall in these areas is minimal.
This is where the Everglades comes into play. Water below the Everglades is usually under higher hydraulic pressure than in urban areas, meaning the groundwater is pushed east out of the Everglades into the urban areas. Like surface water, the groundwater generally flows east from the Everglades, discharging into the Atlantic Ocean.
On its journey through the Biscayne Aquifer, we step in and take our cut, pumping Everglades water from well fields with 139 pumping wells in Miami-Dade County alone. Broward and Palm Beach counties also take their fair share from the Biscayne Aquifer. Water is exported further to Miami Beach and the Florida Keys. The local municipalities are responsible for water quality control and getting the water into your faucets.
Canals: Roadways of Everglades Water to the Biscayne Aquifer
While the vast sawgrass marshes and sloughs of the Everglades are key for recharging the Biscayne Aquifer, there is another way of recharging, via the canals. Canals serve as roadways for Everglades water to the urban areas of southeast Florida, particularly Miami-Dade and Broward counties. To this day, canals continue to drain water from the Everglades for agriculture, while simultaneously protecting the urban areas from flooding resulting from rainfall.
Canals also have an important role in the dry season. Since southeast Florida receives less than 30% of its yearly rainfall at this time, water levels in the Biscayne Aquifer are lower than during the wet season. To maintain a reliable water supply, we drain large volumes of water from the Everglades into the urban areas through canals. Because the canals are highly permeable, when water levels are higher, they recharge the aquifer. This method of recharge is critical for the dry season water supply in South Florida; water wouldn’t reach your house without it. Your swimming pool would be empty, your lawn dry, and your shower and kitchen devoid of freshwater. This also serves to slow the landward intrusion of saltwater into the Biscayne Aquifer.
Everglades Restoration Provides Hope For The Future
Total annual volume of groundwater pumped in billions of gallons from a set of 13 well fields containing 91 pumping wells in Miami-Dade County. The Miami-Dade Water and Sewer Department data were based on daily pumping volumes.
Our thirst for water has increased over time and shows no signs of slowing down in the future. From 2010 to 2020, the population of Miami-Dade County increased by around 8%. Over the same time frame, the groundwater pumped from Miami-Dade wells for public uses increased by around 10%.
Because of this mounting population pressure, the demand for groundwater is expected to increase. While maintaining a reliable urban water supply may be difficult in the future given threats from climate change, drought, and sea level rise, Everglades restoration offers a solution.
Meet the Authors
Dr. Anteneh Abiy, Hydrogeologist, and Dr. Ruscena Wiederholt, Quantitative Ecologist for The Everglades Foundation.