SOME FLORIDA^ LAKES AND LAKE BASINS. lAQ 



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Solution in the limestone occurs both above and below the water 

 line, but chiefly above. As solution continues the overlying ma- 

 terial is no longer able to support its own weight and caves in, form- 

 ing a sink or natural opening from the surface to the limestone. As 

 long as this sink remains open, water passes through and escapes 

 readily into the limestone. Drilled or dug wells serve as artificial 

 openings to the same formation. Wells drilled into this limestone 

 will serve either as supply wells from which water may be pumped 

 or as drainage wells into which water may be conducted. It is 

 generally the case that a well entering this formation that can not 

 bo appreciably affected by pumping, will also conduct water readily. 

 If the openings into the well are sufficiently free to permit ready 

 flow to the well when being pumped, they are, conversely, sufficient- 

 ly open to allow the water to spread rapidly from the well when 

 used as a drainage well. The amount of water held in the pores 

 and cavities of the limestone is so great that the water level is not 

 appreciably afifected either by the water removed when a well is 

 being pumped, or by the water added when a well or sink is used 

 for drainage purposes. 



Attempts to enlarge existing sinks or to re-open sinks that have 

 become clogged have usually proved futile. It is doubtless true that 

 the opening through sinks is a more or less winding channel and to 

 rc-open this when clogged with debris is difficult. 



Better success has been obtained by dug or drilled wells. Where 

 the underlying porous formation into which the. well is to be drained 

 lies near the surface, dug wells can be used to advantage and may 

 be preferable. Dr. H. Bjystra has used this method in draining a 

 small lake or "prairie" on his farm near Brooksville, Florida. At 

 this locality the cavernous limestone lies near the surface and is 

 reached by relatively shallow wells. The one difficulty experienced 

 as reported by Dr. Bjystra is the fact that during the summer rainy 

 season in one or two instances the rainfall has been so heavy within 

 a short space of time that the wells were unable to carry away the 

 water as fast as it fell, the result being temporary overflow of the 

 farm and serious injury to growing crops. When used as pasture 

 land the temporary or partial overflows are, of course, less serious. 



Drilled or bored wells have been in some instances notably suc- 

 cessful. An advantage in the drilled well is that it can be put 

 down to any required depth, and when properly cased and screened 

 is permanent. The effectiveness of the well is dependent upon the 

 structure of the formation penetrated. If the water-conducting 

 power of the formation reached by the well is slight a limit is there- 

 by placed on the effectiveness of the well. Unless the flow of 



