Figure 33. 



Hydrograph of monthly mean discharge 

 through Tamiami Trail (adapted from 

 Leach et al. 1972). 



Monthly distance traveled by sheet 

 flows under varying conditions 

 (adapted from Leach et al. 1972). 



year or sequence of years, depends 

 on the timing, duration, and magni- 

 tude of flood and drought condi- 

 tions. Once inside the park, water 

 flows slowly southward as a broad 

 sheet. Under high flow conditions 

 the rate of sheetflow migration may 

 reach 426.7 to 487.7 m (1,400 to 

 1,600 ft) per day or about 80.5 km 

 (50 mi) per year. Under low flow, 

 rates may drop to zero as the water 

 table falls below ground level 

 (Figure 33b). Superimposed onto 

 this slow movement of sheetflow, the 

 constant background forces of evap- 

 oration and transpiration act to 

 remove as much as 85% of the average 



total input of rainfall 

 1974, Parker et al. 1955). 



(Parker 



Thus the picture emerges, not 

 so much of a continuous "river of 

 grass" flowing from Tamiami Canal to 

 Whitewater Bay, Florida Bay, and the 

 Gulf of Mexico, but rather of a 

 series of sheetflow pulses, each 

 from a different runoff year. These 

 are connected to one another to form 

 a continuous but oscillating gra- 

 dient of flow through the Shark 

 River Slough. Seasonal pulses from 

 Tamiami Canal are augmented by local 

 rainfall and diminished by evapo- 

 transpiration. As the seasonal 



78 



