April 1, 2009

How waters get to our local springs.

Published in the Crystal River Current, Wednesday, April 1, 2009

Millions of years ago huge pressures pushed Florida into the light of day out of the ocean. As the land took on the shape of shore lines and hilly parts, the limestone rock was bent and cracked. Over time, as rains fell and forests grew, moisture soaking in etched a myriad of holes in the rocks enabling water to be contained underground, in “aquifers” (similar to that of a sponge). Rocks were covered with sediments from the sea, as plants and animals enabled soils to evolve. Rain precipitation from the atmosphere is the source of Florida's ground water.

Land changed both above ground, and under ground. Acid-charged underground waters gradually ate away at the rocks. Holes grew into cavities and cracks (fissures) enlarged. Underground water, held there under weight of water above, flowed from higher pressure areas to lower pressure areas. Water flowed more slowly through the smaller holes and more quickly, taking the easier path, as those flows encountered the fissures and cavities.

Underground flows vent (emerge) as surface water as a fissure conducts the water there, or into a shallow water body. Sometimes, it may vent from a near vertical “solution pipe” directly from an artesian (under pressure) cavity. Or, a cavity near the land surface may simply cave in its roof. These vents are either termed a seep (slow flow) or a spring (faster flow).

In 1951, Dr. Robert Vernon, produced a remarkable map of Florida, not of the topography but showing the pressure of water in the aquifer. Lines on the map showed piezometric contours, (meaning, piezo = pressure, metric = measure, contour = line joining points of equal measure). For the first time, he showed locations of many fracture sets, or fissures, in the aquifer rocks.

Northwesterly peizometric flows to Citrus County come from higher pressure regions in Polk and Pasco counties to the south, with converging southwesterly flows from an area between Alachua and Putnam counties to the north.

Next time, we shall consider our local springs.

Norman Hopkins. Director, Kings Bay Association.