Although the trend shown in Figure 5 is typical of the region, 
seasonal flow characteristics of streams in the area vary due to 
differences in factors such as basin size, land cover, depressional 
storage, and groundwater relationships. For instance, artesian springs 
flow into the Hillsborough and Alafia Rivers providing an important 
source of baseflow during the dry season. Of particular importance are 
the many minor tributaries which drain small, very flat basins. Baseflow 
levels in these tributaries are very small, and total yearly flows are 
dominated by brief periods of runoff after storm events. For these small 
tributaries, the relative differences between dry and wet season flows 
are probably greater than the values for the three rivers displayed in 
Figure 5. 
DRAINAGE AREAS 
The lands supplying runoff to Tampa and Sarasota Bays can be 
conceptually divided into ten drainage areas (Figure 1). Four of these 
areas are the respective basins of the area’s major rivers,which are from 
north to south; the Hillsborough, Alafia, Little Manatee and Manatee 
Rivers. These rivers originate from the higher terraces in the eastern 
portion of the Tampa Bay watershed and flow in a westerly or 
southwesterly direction emptying into the bay on its eastern shore. The 
hydrology and water quality of these four rivers is addressed later in 
this paper. 
The remaining six drainage areas are not true hydrologic basins 
but rather are low-lying coastal areas which are drained by small 
streams, canals, stormwater conduits and tidal creeks. Three of these 
coastal areas comprise the entire drainage to Sarasota, Boca Ciega, and 
Old Tampa Bays. The remaining three areas drain to the eastern shore of 
Tampa Bay between the mouths of the four major rivers (Figure 1). 
MINOR TRIBUTARIES 
The Tampa Bay Regional Planning Council (TBRPC) recently completed 
an ecological assessment and classification of the minor tributaries to 
Tampa Bay (TBRPC 1986). Forty four creeks were identified, although 
three of these were upstream forks of previously mentioned creeks and one 
was a man made canal (Figure 6). These tributaries to the bay ranged in 
total length from 0.5 to 17.5 miles. Although they are largely ungauged, 
it was assumed that average flow in most of these creeks was less than 
their respective tidal prism. In a review of the meteorology and 
hydrology of Sarasota Bay, Walton and Gibney (1988) identified six 
tributaries supplying runoff to Sarasota Bay. The largest of these, 
Phillippi Creek, drains 58 square miles and actually empties into the Bay 
near Little Sarasota Bay, just to the south. The remaining tributaries 
to Sarasota Bay are small, the largest draining only 12.7 square miles. 
24 
