Surficial Aquifer

Sometimes called an unconfined or water table aquifer, Florida’s Surficial Aquifer varies by region, consisting of limestone and sand in south Florida and sand and gravel in the panhandle. | Aquifers | Biscayne | Floridan | Intermediate | Surficial | Springs | Estuaries and coast | Water bodies | Florida’s water districts

Intro - Groundwater walker?

We walk on the surficial aquifer every day

By Robert V. Sobczak

Why hike to a lone mountain top ...

When there's good aquifer hiking all around.

Specifically, I'm talking the surficial aquifer. Granted, it's usually covered with some soil, and in south Florida a pock-marked slab of caprock, but it's kind of fun knowing that wherever you walk there's water beneath your feet. In the swamp, often it's above your feet, too. In the same way that the swamp percolates down and recharges the surficial aquifer, the surficial aquifer also recharges the aquifers beneath it. We know the Floridan aquifer is the source of the springs, but did you know that the surficial aquifer is the source of the Floridan? The Intermediate aquifer is also recharged by the surficial aquifer above it. Interestingly, the surficial aquifer is a general catch-all term. In Collier County it's called the Tamiami or Graystone Aquifer. It has other handles in other parts. Who knew one groundwater source could go by several nicknames.

Recent Blog Posts

Swamp Geology
Out of sight out of mind?

When it comes to geology …

It may be last on the swamp check off list.


By check off list, I mean what tourists come to see — with alligators being at the top. I’ve heard it said that some four out of five people visit to the swamp to see an alligator. As interesting as they are to see, they are oddly not present in the geology of the swamp. Even odder, as old as the alligators would have you believe the place to be, the swamp ecosystem is actually quite young, just a few thousand years old. Native American tribes inhabited Florida before the Everglades or the Big Cypress swamp existing. So there are no alligator bones in the geology, it’s all marine limestone, about 3 miles worth underlying the swamp with the upper 50-100 feet forming the Gray Limestone Aquifer. Unlike the Biscayne Aquifer to the east, the Graystone Aquifer isn’t as permeable nor as intensely pumped. With regard to the later, I think that alligators are happy about that.

Geology of the Swamp
Out of sight, out of mind

Not many people visit the swamp …

To see its geology.

Cross sectional sketch of the swamp’s geology

But really, the geology is an underappreciated treasure of the swamp, and not uncoincidently buried under the ground. Did you know there is about 3 miles of marine limestone underlaying the swamp? In layman’s terms, that’s over 500 million years of deposition, all sitting on top of the Senegal Platform rifted away from the African Plate when the last supercontinent Pangaea rifted apart. Most of south florida’s drinking water is in the top 100 feet. About a thousand feed below ground is the cryptic geologic layer known as the boulder zone where coastal cities pump their treated municipal wastewater. Much farther down is the Sunniland Trend that holds a modest reservoir of hydrocarbons. I’m not saying the geology of Florida is as scenic as Yellowstone or other western parks, but it may be more interesting, even if if visualizing it and understanding it requires a good geology book. In that regard, I highly recommend Geology of Florida by Randazzo and Jones and Land from the Sea by Edward Hoffmeister.

cultural waters

Chunk o’ tabby
A diamond in the rough?

Remember being coaxed into being good as a kid …

Or else risk not getting something on your list?

This chunk of limestone
is on display at the Palm Cottage

Like a chunk of coal, or a hunk of rock (as shown above).

Well despair no more!  That’s no ordinary stone: it’s a prized piece of Tamiami Tabby.  The original settlers of Naples didn’t have any cement mills, but with plenty of sand and water and shells they were pretty well set. Mix them together in a broth over the high heat of a buttonwood fire, and then let it dry, and tabby is what you got.

Palm Cottage is the oldest 
house in Naples, Florida

Not as strong as modern cement, but good enough:

They used it to build the Palm Cottage – Naples oldest house – which, just a few blocks from Naples Pier, is still standing.  At least, that’s what I read on the sheet of paper above the rock.

Couldn’t think of a better gift!

Swamp’s subterranean source?
How the history books got it wrong

The Immokalee Rise is often viewed …

As the northern “terrestrial” bounds of the swamp.

The myth of a rain-driven swamp falls apart
when you consider its connection to a higher Lake
Okeechobee, the flooded Lake Flirt floodplain,
Ft. Thompson falls and the underlying karst 
and porous sands of the Immokalee Rise,
prior to drainage of course

But “hydrologically” could it have been its source?

Imagine if you would:

  • A higher pre-drainage Lake Okeechobee, 23 feet above sea level (asl).
  • A fully intact Ft Thomson Falls that pooled water in the Lake Flirt floodplain, 20 ft asl
  • Groundwater flowing laterally through the Immokalee Rise’s underlying karst 
  • Rainwater infiltrating down into the porous sands of the Immokalee Rise  

Under that scenario, Immokalee Mountain wasn’t a dam at all, but the underground spigot that supercharged the headwaters of the swamp.

Special thanks to hydrogeologist and swamp emeritus Jack Meeder on this post!

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Fact: “Just because nobody measured it doesn’t mean it didn’t exist.” Bob Says

Aquifer express

Alligator Alley is more than just a road …

From coast to coast.

Old aquifer adage: The rain
in the Glades soaks mainly
into the Biscayne

It’s a high-wire ride across the top …

Of the underlying aquifers below.

That’s the source of our drinking water, you know!