Karst

Surface water

A portion of surface water from precipitation is continually evaporated and transpired back into the atmosphere, part runs off as streams or collects in basins as ponds or lakes, part permeates under ground to enter voids in rocks to flow downhill eventually to the sea. Water contained in the voids in the rocks is subsurface water and that which completely saturates the rock is groundwater. If the top surface of the groundwater is free to fluctuate upwards and downwards the water is under water-table conditions. If the groundwater surface is overlain by a formation that contains few voids, or poorly connected voids or small enough voids to restrict the flow of water, the water is confined and under artesian conditions. (Dr. Robert O. Vernon writing in his 1951 report published as Florida Geological Survey – Bulletin 33)

Ground water flow in Karst terrain

In that report, (on page 43) he also writes, "Limestone is as a rule jointed vertically and bedded horizontally and openings along these joints and beds provide easy avenues of travel for water. The ultimate source of all Florida's ground water is from the rain and precipitates from the atmosphere. As the rain water falls through the air it becomes charged with carbon dioxide gas that combines with water to form carbonic acid. On the ground humic acids from rotting vegetation is added. These are the common solvents of limestone. ...As it moves through pores and open spaces in the limestone it acts as a slow solvent to increase the size of the openings and to connect them to form a continuous system of channels. As these channels are expanded by solution, cave systems are developed horizontally and one system may lie over another and may be connected by vertical tubes and rooms."

Click here to see a Case Study of Groundwater flows.

Karst features

He continues (on page 44), to discuss Karst features as the formation of sinkholes by cave collapse near the surface and how solution pipes are created by upward artesian pressures to form springs or seeps at the ground surface, which in turn may continue to expand in size over time.

Dr Vernon emphasizes (on page 240); "since all fresh water in Citrus county is derived directly from atmospheric precipitation falling locally and on adjacent counties, conservation of groundwater resources requires that water consumed does not exceed that which is readily available from streams, lakes and wells and that this usage be small enough to maintain normal storage of waters on the surface and in the ground. Otherwise, lake levels lower, and well and stream flows decrease".

Click here to see also the report, The Citrus County Aquifer Vulnerability Assessment