FLORIDA GEOLOGICAL SURVEY


into the Floridan aquifer in outcrop areas. Water is discharged
from the aquifer by (1) outflow to areas of lower piezometric head,
(2) seepage and spring flow into the streams, (3) upward leakage
to the nonartesian aquifer in areas of artesian flow, (4)
evapotranspiration, or (5) pumpage.
 Piezometric maps of the area were made from water-level
measurements in about four hundred wells. These maps were
analyzed to determine areas of recharge and discharge and the
direction and rate of ground-water movement.
 The first piezometric map of peninsular Florida was prepared
by Stringfield (1936) and the latest, figure 33, was prepared by
Healy (1961).
 Ground water moves from high head to low head in a direction
perpendicular to the contour lines. Piezometric mounds, referred
to as "highs," usually indicate areas of recharge to the aquifer.
Piezometric depressions or troughs, referred to as "lows," usually
indicate areas of discharge from the aquifer. Recharge and
discharge may take place anywhere from the high to the low
where geologic and hydrologic conditions are favorable. Therefore,
there is no one point of recharge nor one point of discharge. The
difference in head between contour lines divided by the distance
between them is the hydraulic gradient of the piezometric surface.
The hydraulic gradient varies because of (1) unequal amounts of
recharge or discharge, (2) differences in permeability within the
aquifer, (3) differences in thickness of the aquifer, or (4) boundary
conditions within the aquifer.
 Ground water in the central part of the Florida Peninsula moves
outward in all directions from an elongated piezometric high that
extends approximately from central Lake County to southern
Highlands County, generally referred to as the "Polk high," and
from a smaller piezometric high in Pasco County, commonly
referred to as the "Pasco high." The Green Swamp area occupies
a relatively small part of the Polk high. The top of the Polk high
occurs within the southeastern part of the Green Swamp area.
 Ground-water drainage areas in the Floridan aquifer do not
coincide with the surface-water drainage areas in the Green Swamp,
shown in figure 34. The ground-water divides in the aquifer shift
slightly in response to recharge and discharge. Therefore, the
positions of the divides as shown in figure 34 were considered to be
average for determining the size of the ground-water drainage
areas that contribute outflow from the Green Swamp area toward
the major surface drainage areas. Water in the Floridan aquifer