One of the main buzz words today of perils to Florida is "Sinkholes." Geologically speaking, these are areas that have collapsed or subsided due to dissolving of the limestone beneath them or the collapse of pockets due to a reduction of water pressure. It is good that people have become somewhat educated about them and their possible role in recharging and contaminating the Floridan Aquifer. It should be stressed though that these are in the "Big Picture" recent geological events of minor significance to the Floridan Aquifer.

The role of karst limestone formation and its role in the Floridan Aquifer and the resultant major landforms like the Brooksville Ridge that recharge it day after day have become overshadowed by this myopic focus on sinkholes.

Sometimes it easier to understand a phenomena by doing what's called "reverse engineering", that is, looking at something from the end rather than the beginning. The springs along the coast in Citrus County have to be supplied by water from somewhere, but how much and from where?

On average the main springs along the Gulf coast (the Crystal River, Homosassa and Chassahowitzka groups) discharge over 1,300 cubic feet of water per second. In layman's terms that translates to:

     Over 850 million (850,000,000) gallons per day
     Or over 310 billion (310,000,000,000) gallons per year.

This yearly magnitude of water would require a square tank with a base 3,450' X 3,450' and a height of 3,450 feet to contain that much water!!! That's a tank measuring .65 miles in all three dimensions.

So where does all that water just to feed these springs come from? The surface waters (lakes, ponds, rivers, streams, marshes, etc.) of the county as well as land areas not located on the Brooksville Ridge supply very little to the springs since upwards of 90% + of the water that they receive from rain either evaporates, transpires through plant life, or drains to the Gulf of Mexico.

Citrus County has an average yearly rainfall of 55 inches. If the surface waters and land other than the Brooksville Ridge (nearly 200,000 acres) absorbed 10% of that rainfall, or 5.5 inches, about 30 billion gallons or 9% of the springs' needs would be met. So where does the rest come from?

The Brooksville Ridge accounts for nearly 190,000 acres of Citrus County's 374,000 acres of land area, over 50% of the county's land area. Its many hills and valleys within a short distance of one another is one of the distinguishing features of karst topography. The Brooksville Ridge is even more unique in that the surface above the karst limestone is composed primarily of sand. It does not have a confining layer of clay or low permeability sediments that characterize other areas of the Florida Peninsula.

Rain falling on the Brooksville Ridge percolates rapidly down through the sand and into the karst limestone that forms the Floridan Aquifer, the porous rock formed over some 40 million years that holds water. It is ironic that actually the wettest area of the county is at its surface apparently always dry. In regions of Florida where there are confining layers, one finds surface water bodies that have formed on the perched water tables. The Brooksville Ridge is then the place of lakes that aren't. This is the signature of karst topography.

These sands began to be deposited on the karst limestone some 1.5 million years ago during the Pleistocene Epoch through alternating rises and falling of the oceans. The closed valleys or closed-depressions (in Europe they are called dolines) that are found throughout the Brooksville Ridge are indicators of fractures in the karst limestone that have channeled water at greater rates and produced conduits or caverns as more limestone dissolves. As these fissures slowly filled with sand the ground level receded producing valleys. These depressions account for 20% (38,562 acres) of the ridge in the county and represent 73% (2,021 on ridge and 2,782 total in county) of all closed-depressions in the county. The largest is over 2,600 acres and 43 are over 200 acres in area. Although the fractures have to an extent filled with sand, little resistance to water flow is created. The closed-depressions funnel all the water raining on the ridge to the conduits and fractures.

It is reasonable to assume that at least 80% of all the rain falling on the Brooksville Ridge is absorbed very quickly into therefore the Floridan Aquifer. Where else could it go? The ridge is sparsely vegetated, so there is little transpiration, and the water does not stand even in the most heavy rains, so there is little time for evaporation. Accordingly, the Brooksville Ridge is noted in all the scientific literature as a very high aquifer recharge area. In fact, the Brooksville Ridge is known as one of the highest direct recharge areas in the world.

But let us now relate that back to the springs that sit just a few miles to its west. Given that 80% of the rainfall is absorbed, that amounts to 44 inches of rainfall being absorbed per year on average by the ridge. This gives the following results:

Feature of Brooksville Ridge	Acres	Aquifer Recharge	Portion of Springs Discharge Per Year
Closed-Depressions	38,562	46,073,437,361	15%
Hills	151,108	180,542,113,290	58%
Total:			73%

So if one combines this 73% from the ridge with the 9% from the rest of the county, one obtains 82% of the water the springs would require just to feed themselves.

Not accounted for is the water withdrawn from the aquifer for human use or the water needs of the county's smaller springs or the transpiration from plants. This additional water comes from the aquifer outside the county.

It is important to note though that the county does not have enough water alone to feed its own major springs. It's already maxed out and drawing on water outside the county. The springs therefore are a regional resource as their needs depend on aquifer water resources outside the county. Any talk of sharing our abundance are then completely ludicrous since we do not have enough for our own needs, not for even our springs. We already operate at a deficit.

The Floridan Aquifer supplies all the water to the springs.