FLORIDA GEOLOGICAL SURVEY


 The specific yield of the sand comprising the nonartesian aquifer
ranged from 31.0 to 43.9 percent by laboratory analysis (table 8)
and from 12.5 to 47 percent by analysis of water-level fluctuations
caused by local rainfall, shown in figure 30.
 The highest values (22.2 and 47 percent) are considered to be
representative of the aquifer in the sandy ridges that surround
the eastern and southern part of the Green Swamp area. The lower
values (12.5 and 18 percent) are considered to be representative
for the clayey sands in the central portion of the area.

CHEMICAL CHARACTERISTICS OF NONARTESIAN GROUND WATER

 Water in the nonartesian aquifer in the eastern part of the
Green Swamp area is less mineralized than that in the Floridan
aquifer. The mineral content of water from the shallow wells in
this area, ranging from 30 to 50 ppm, is due to the low solubility
of the sand and clay which comprise the aquifer. The principal
dissolved mineral constituents are sodium and chloride. The iron
content ranged from 0.19 to 4.0 ppm. The 4.0 ppm in water from
well 808-139-1 was the highest found in the Green Swamp area.
The color of water from wells in the area was less than 15 units
which is lower than that of surface water.
 In the western part of the area, the nonartesian aquifer is
almost nonexistent. The chemical characteristics of water in most
shallow wells and in the Floridan aquifer are similar.

 SECONDARY ARTESIAN AQUIFER

 RELATION TO GREEN SWAMP AREA

 The secondary artesian aquifer is composed of interbedded
limestone in the undifferentiated clay (table 4). About 36 feet of
the aquifer is present in well 810-144-1 in the southern part of the
Green Swamp area. The aquifer thickens southward from the
southern boundary of the area and is an important source of
artesian water in southern Polk County. The aquifer pinches out
northward and is absent in most of the Green Swamp area.
 The aquifer is recharged by downward percolation of water from
the overlying nonartesian aquifer and discharges principally by.
downward leakage to the Floridan aquifer.
 Fluctuations of the piezometric surface of the secondary
artesian aquifer were recorded in well 805-155-3 (fig. 25) and the