REPORT OF INVESTIGATIONS No. 42


breaking the hydraulic continuity and producing barriers that
retard water movement.
 (3) Faults cutting confining beds could increase ground-water
circulation between aquifers.

 HYDROLOGY

 The water supply of the earth, whether it is on the surface or
below the ground, has its origin in precipitation. Of the
precipitation that reaches the ground, part is returned to the
atmosphere by evapotranspiration; part remains above ground and
is stored temporarily in lakes, ponds, and swamps, or moves to
the sea as streamflow; and part percolates into the ground, some
to replenish the soil moisture and some to enter the zone of
saturation and recharge the ground-water aquifers. Ground water
moves in the aquifers under the influence of gravity, towards areas
of discharge such as streams, lakes, springs, wells and the oceans.

 WITHLACOOCHEE RIVER BASIN

 DESCRIPTION OF BASIN

 The'Withlacoochee River drains 82 percent of the Green Swamp
 area. The total drainage area at stations 42 and 43 at the western
 boundary is 740 square miles, all of which is within the project
 area except for 45 square miles of lakes and hills west of U. S.
 Highway 301 and south of U. S. Highway 98 near Dade City.
 Most of the general topographic and drainage features of the
 Green Swamp area, described in preceding sections of this report,
 apply to the Withlacoochee River basin in particular. The following
 description of the basin refers specifically to this stream system.
 The Withlacoochee River heads in a group of lakes and swamps
 in the north-central part of Polk County in the vicinity of Polk
 City and the town of Lake Alfred (see fig. 5). Lakes Van and
 Juliana, the uppermost of these headwater lakes, drain into Lake
 Mattie. Surface drainage from Lake Mattie spills through a wide
 shallow marsh along the northeastern shoreline and flows
 northward through a series of interconnected shallow swamps and
 ditches to the northern boundary of Polk County. This is generally
 considered to be the major headwater channel of the Withlacoochee
 River. Other headwater tributaries originate in the marshes
 between Lakes Mattie and Lowery and flow generally northward
 between the confining ridges. These channels join near the