The next time you drive through north-central Florida, look around. You’ll see that, in most instances, we lack things that are common in other parts of the USA. These include:
- Roadside ditches
- Gutters and downspouts
- Storm sewers
- Surface streams
Why? We don’t need them. Our ground is so porous, the minute water hits it, it disappears underground. This phenomenon helps explain why we have so many springs and sinkholes.
A giant sponge
The topsoil through much of north-central Florida is largely sand. Sand is incredibly absorbent. Pour a cup of water on a patch of beach sand; it will disappear almost instantly.
Below this thin layer of topsoil is what geologists call Ocala Limestone. It is among the most porous types of limestone. If you think water can’t move through solid rock, pour some on a piece of Ocala Limestone. Watch what happens. It’s almost like pouring water on sand.
The net effect is that the ground here in north-central Florida is like a giant sponge. As soon as rainwater hits it, that water is absorbed.
Down and out…
The water that passes through the surface layers of sand and rock travels downward until it hits the aquifer. It generally doesn’t have to travel far. At Blue Grotto, the top of the aquifer or water table is usually less than 20 feet from normal ground level.
It’s important to understand that the top of the aquifer is higher than sea level. In the Williston area, this difference is around 50 feet. This means that gravity is constantly forcing our groundwater in the direction of the Gulf of Mexico.
If need be, this water will move through the rock itself. But, if it can find an easier way to do so, it will.
Care to drop some acid?
Before it goes underground, the rainwater typically passes through a thin layer of decaying organic matter. As it does, it can absorb the carbon dioxide that is a byproduct of the decomposition. This forms a very weak solution known as carbonic acid.
How weak is this acid? Extremely weak. Filtered, it is perfectly safe for human consumption. In fact, there is a large plant near Ginnie Springs that bottles and sells water from the spring. Still, giving the vast scale of geologic time, even this weak acid can eat away at the soft limestone.
In our article on What Created Blue Grotto, we describe the process by which north-central Florida’s springs and sinkholes form. Suffice it to say that, without the porous nature of the ground here, there would be no springs or sinkholes.
Streams vs. Runs
Throughout much of the USA, most rainwater does not go underground. It is channeled into streams which, in turn, feed rivers and eventually end up in the ocean.
In north-central Florida, should you come across what appears to be a stream, it’s not actually a stream at all but rather a spring run. You can tell a spring run from a stream fed by rainwater runoff by its clarity. Spring runs tend to be very clear. The only place you are likely to see a “normal” stream of equal clarity is in the mountains.
Our region’s two major rivers, the Suwannee and the Santa Fe originate in swamplands to the north and east of us. This explains their dark, tannic appearance. However, on the rivers’ way to the Gulf of Mexico, various springs and spring runs empty into them.
When they do, you will see a very dramatic incursion of crystal-clear spring water into the dark, tannic river water. As the water moves downstream, the two eventually mix. However, the river ends up being clearer in the process. Depending on the time of year and recent rains, it can be a lot clearer.
The river that isn’t
You may be familiar with the nearby Rainbow River. It originates in Rainbow Springs State Park north of Dunnellon and flows for over five miles to the Withlacoochee River. Divers like to take the water taxi from KP Hole Park upstream, then drift for up to a mile or more in the shallow, clear water back to their starting point.
The thing about Rainbow River is that it is not really a river at all but the area’s largest spring run. This explains its unusual clarity. If you do the Rainbow drift dive, you will come across a number of places where additional spring water empties into the “river.” Among the most interesting of these are pockets of water-saturated sand that appear to boil.
An area like no other
By now it should be apparent that north-central Florida provides divers with opportunities unlike anywhere else in the USA. In addition to Blue Grotto, you should plan on diving Devil’s Den, Paradise Spring, Troy Spring and Rainbow River. It may take more than one trip to do so, but it’s time well spent.