Although it has been extensively mined and is also characterized by high 
constituent levels, the South Prong has had significantly better water 
quality than the North Prong. Water quality below the confluence of the 
North and South Prongs has generally been intermediate between these two 
branches. 
Water quality in the Alafia river basin has shown significant 
improvement since the mid-1970’s due to the implementation of pollution 
abatement practices by the phosphate industry in response to federal, 
state, and local regulations. The recycling and better management of 
waste effluents plus an elimination of slime-pond spills have resulted in 
significant reductions in constituents such as total phosphorus, 
orthophosphate, and fluoride. Nutrient levels are still extremely high 
in the river (Table 2), however, and the Alafia is a major source of 
nutrients to Tampa Bay. Data collected during 1979 indicate that since 
the initiation of advanced wastewater treatment at the Hookers Point STP, 
the Alafia has become the predominant source of both total nitrogen and 
phosphorus to Hillsborough Bay (see Garrity, McCann and Murdoch 1985). 
Flowing into the Alafia River fourteen miles above its mouth is 
Lithia Springs, an artesian system that discharges groundwater at an 
average rate of 46 cubic feet per second. Water quality in the spring 
reflects groundwater conditions, with excellent water clarity and a 
nearly constant temperature year round (75°F). An interesting aspect of 
the spring’s water chemistry is its high nitrate concentrations, which 
ranged from 2.3 to 3.2 mg/1 during 1984-1986. Crystal Springs, which 
flows into the Hillsborough River, similarly show high nitrate levels, 
averaging 1.8 mg/1 during this same period. These data indicate that at 
some locations in Hillsborough County high nitrate groundwaters may have 
a pronounced influence on instream concentrations. Stream-groundwater 
relationships in the region are complex, however, and it is difficult to 
assess how widespread this phenomenon might be. Similarly, the causes of 
high nitrate concentrations in these two springs are not known, and the 
regional extent of this condition is poorly documented. 
Little Manatee River 
The Little Manatee River is the smallest of the four major rivers 
draining to Tampa Bay and is generally considered to be the one in the 
best ecological condition. Land use in the basin is primarily 
agricultural with light urban development occurring on two small 
tributaries and at the town of Ruskin near the mouth of the river. The 
floodplain of the river in the middle and upper reaches is largely intact 
and mangroves or saltmarsh line the shore of much of the lower river. 
Water quality in the upper reaches is generally high in color with 
moderately high nutrient levels, presumably due to agricultural, highway 
and wetland runoff. One phosphate mine, which is currently inactive, has 
a permitted discharge into the headwaters of the river. Nutrient inputs 
from undisturbed soils and vegetative associations are uncertain, 
however, so the effects of land alteration on background nutrient levels 
are difficult to assess. Values for selected water quality parameters 
39 
