REPORT OF INVESTIGATIONS No. 41


4.0   i Well 016-535-342b                                      Z
                    0                                          _j~0
             Wole( level
                I-                                              -30                                                             I.'

524
                                                               0
   I.0%                                                     3000 _Z
                                 :Chloride
                                     VMl 015-535-232
  1.0                                                       2000

  0                                                         1000

                                                            0
    NOV. DEC. JAN. FEB. MAR. APR. MAY JUNE JULY  AU. SEP. OCT. NOV. DEC. JAN. FEB, MAR. APR. MAY aLINE
    961                  1962                      1963
Figure 28. Graphs showing the rise of water levels and change in chloride
     content of ground water after construction of Deer Point Dam.

below the ground. These are the sand hills, sinks and lakes, the flatwoods forest, and the coastal sand dunes and wave-cut bluffs. 
    The surface materials on which the physiographic features have developed are generally very porous, permeable sands which are from 0 to 140 feet thick. These sands form the water-table aquifer. A confining layer, or aquiclude, of sandy clay and clayey shell material separates the water-table aquifer and the Floridan aquifer.
    In the bay area and along the gulf coast there are two artesian aquifers. Here the formation that forms the aquiclude is thicker than it is to the north and is overlain and in part underlain by some shellhash beds which contain water under artesian pressure. Water producing zones in the shell-hash beds above the aquiclude are termed the secondary artesian aquifer.
    The Floridan aquifer underlies the entire basin below the aquielude. It is composed of limestone formations that include the lower units of the shell-hash beds and are as much as 1,200 feet thick.
    The basin receives an average of 58 inches of rainfall per year. A part~of the rainfall is absorbed by the porous surface sands and a part moves directly into the streams. Some water from the sands moves to the streams and maintains flow during periods of no rain-