temporal trend in water qualities is apparent. Water quality in general is 

 fair, sometimes poor, especially since the river is designated as a potable 

 water supply. 



Alafia River Basin . The Alafia River, located in Hillsborough and Polk 

 Counties, flows westward 24 mi into the Hillsborough Bay. Major tributaries 

 are the North Prong, South Prong, and Little Alafia Rivers. Land use in the 

 basin is largely agricultural (35%), range (17%), and barren lands (12%). The 

 river flows through areas of extensive phosphate mining and rock processing. 

 Industrial sources, primarily phosphate, discharge an average of 63 Mgal/d of 

 wastewater into the Alafia River. Additional sources of pollution include 

 runoff from mines, pastures, and agricultural areas. Occasional slime spills 

 from phosphate processing operations. TKN values are high in the headwaters 

 of North Prong and the Alafia Rivers. Phosphorus concentrations are high in 

 the headwaters but decline downstream. Nitrate-nitrite concentrations also 

 are very high but decrease progressively downstream. In the main stem of the 

 river, DO decreases to extremely low levels for about 5 mi. The Alafia River 

 rarely meets Class III standards for DO in this reach of the river. Concentra- 

 tions of cadmium and mercury greater than State standards have been detected 

 in the North and South Prongs. 



High concentrations of lead have been reported at Lithia in Hillsborough 

 County and high levels of fecal col i form bacteria (1,010 to 5,150/100 ml) have 

 been reported for all of Alafia River. This may be due to the abundance of 

 cattle in the intensively grazed pasture leands along the river. Nitrogen and 

 fecal col i form levels have increased and DO concentrations have decreased in 

 recent decades. In all, organic loading may be responsible for the decline of 

 water quality in recent years. Conversely, phosphorous concentrations have 

 declined. In general, water quality in the Alafia River Basin is fair in the 

 upper reaches of the South Prong, and poor in the North Prong and Alafia 

 Rivers. 



Manatee River Basin . The headwaters of the Manatee River flow approxi- 

 mately 25 mi southwesterly into Tampa Bay from the northeastern corner of 

 Manatee County. This river is impounded at Lake Manatee to provide the drink- 

 ing water supply for Manatee County. Downstream from Fort Hammer, the Manatee 

 River is influenced by tides. Principle tributaries of the Manatee River are 

 Braden River and Gamble Creek. Land uses are primarily agricultural (38%) and 

 rangeland (41%). Bradenton and Palmetto are the major urban areas. Sources 

 of pollution include domestic sewage and surface water runoff from rangeland 

 and agricultural lands. Concentrations of total phosphorus are relatively 

 high (0.26 to 0.52 mg/1), but water quality generally is good throughout the 

 system which is characterized by low concentrations of TKN, nitrate-nitrite, 

 and fecal col i form. In recent years concentrations of total phosphorus and 

 nitrate-nitrite have declined. In general, water quality in the Manatee River 

 basin is very good. 



Withlacoochee River Basin . The Withlacoochee River originates in the 

 Green Swamp near the junction of Lake and Polk Counties, and flows in a north- 

 westerly direction for about 157 mi through Polk, Pasco, Hernando, Sumter, 

 Citrus, Marion, and Levy Counties and discharges into Withlacoochee Bay at 

 Yankeetown. A major portion of the flow is contributed by the Florida aqui- 

 fer. The river basin contains numerous lakes and springs, and the river is 

 impounded for hydro-electric power at Inglis near the gulf in Citrus County. 



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