FLORIDA GEOLOGICAL SURVEY


northern boundary of Polk County and flow westward to form the
Withlacoochee River.
 West of State Highway 33 the tributaries of the Withlacoochee
River are not confined by the ridges that are prominent in the area
east of the highway. These tributaries have developed basins that
are generally more fan-shaped than those in the eastern part.
 Pony Creek, which flows northwestward, is the first of the large
tributaries entering the Withlacoochee River west of the Seaboard
Air Line Railroad. Pony Creek heads in a swamp east of Lake
Helene near Polk City. Lake Helene has no surface outlet except
at extremely high stages when it overflows into the Pony Creek
basin.
 Grass Creek, the next large tributary, empties into the
Withlacoochee River about one mile downstream from Pony Creek.
Grass Creek heads in a group of small lakes in the vicinity of Polk
City. the largest of which is Lake Agnes. The outlet from Lake
Agnes is a ditch leading from the northern end of the lake and
connecting with the network of canals and ditches that carry the
water northwestward through the swamp. Several other tributaries
flow into Grass Creek as it crosses the swamp.
 Gator Creek empties into the Withlacoochee River at the
Polk-Pasco County line. This is the largest tributary upstream
from the diffluence of the Withlacoochee River to the Hillsborough
River. Gator Creek heads in several small swamps northeast of
Lakeland and flows northwestward through a network of swamp
channel and ditches.
 From the point of diffluence to the Hillsborough River, the
channel of the Withlacoochee River turns abruptly to the north and
continues northwestward to the western boundary of the Green
Swamp area at U S. Highway 301.
 About 14 miles downstream from the point of diffluence, a major
 canal draining several lakes and swamps east of Dade City empties
 into the river from the west. This canal also carries the drainage
 from an area of hills and lakes west of Dade City and the effluent
 from citrus concentrate plants at Dade City.
 One of the larger tributaries entering the Withlacoochee River
 from the east is formed by the confluence of Devils Creek and
 Gator Hole Slough. Devils Creek heads in a swamp about 21/
 miles east of the Sumter-Pasco County line. At high stages some
 water from the Withlacoochee River moves through a gap in a low
 ridge into Devils Creek. This water returns to the Withlacoochee
 River farther downstream.