island building, bulkheading, causeway construction and construction of unnatural tidal 
inlets. Changes in the Everglades estuary were due principally to alterations in the 
watershed following the development of the Everglades for agriculture. In addition, 
local canal building has complicated the water exchange pattern, permitting high- 
salinity water to penetrate areas that were formerly fresh to brackish in nature. 
Salinity is the major environmental factor in the area affecting the plant and animal 
communities. Salinities have changed, beginning about 1920, with a reduction in runoff 
to the Shark River from an estimated average annual flow of 2.3 million acre-ft to a 
measured average of 473,200 acre-ft. Coot Bay and Whitewater Bay salinities are now 
thought to be about twice as high as in the average years prior to 1920. The 
hydroperiod (i.e. the annual period during which runoff measurably dilutes seawater in 
the estuary) probably lasted 12 months of each year of average to above average 
rainfall prior to 1920. Since then this has been reduced to about 7 months. Further 
reduction of runoff from the Everglades, to the area within the Park, will probably 
shorten the hydroperiod to about 5 months. This will permit rapid salinity increase in 
Coot and Whitewater Bays, both by evaporation and by salt intrusion through tidal 
inlets from Florida Bay and the Gulf of Mexico. Florida Bay has a limited watershed that 
acts as a moderating influence on the prevailing high salinities caused by evaporation. 
The salinity pattern of Florida Bay has probably not been altered in historic times. 
However, reduction of its small watershed, particularly the northern part near 
Homestead where annual rainfall is heaviest, could lead to permanent hypersalinity in 
Florida Bay. If salinity increases above 50 - 60 °/oo it may be expected that many 
plants will not survive and many animals will be unable to reproduce successfully. If 
salinity rises above 60 - 70 °/oo many species will die or be forced to leave the region. 
Hypersalinity in Florida Bay would be transmitted to Coot and Whitewater Bays by net 
gain of salt on each flood tide through Buttonwood Canal thereby making conditions 
unfavorable for many desirable animals and plants. At present, Coot and Whitewater 
Bays have salinities ranging between 0 - 5 and 30 - 40 °/oo, averaging about 18-25 
%o. Under these salinity conditions a greater variety of plant and animal life is 
present than in pre-1920 times. With a slight increase in average salinity the region 
would be subject to an invasion by most of the marine species now found off-shore. 
This would favor angling and sightseeing pursuits but would create a situation different 
than in pre-drainage times. We believe that salinities observed are probably most 
favorable for the perpetuation of the area's nursery grounds for shrimp, menhaden, 
crabs and other valuable species. A return to conditions approximating those of the 
pre-drainage period would require a minimum average of 1.5 to 2.0 million acre-ft of 
runoff through the Shark River drainage annually. This should be spread over a full 12 
month period. In many southern estuaries low to moderate salinities should be 
maintained if possible and control should aim at supplying enough freshwater to result 
in annual salinities of about 18 to 30 °/oo. 
1957 - 1962 
Tabb, D. C. (1967) Prediction of estuarine salinities in Everglades National Park, Florida, 
by the use of ground water records. Ph.D. Dissertation University of Miami, Coral Gables, 
FL. 107 pp. 
There is a strong linear relationship between ground water level as expressed by 
elevation of water height in specified wells in the respective watersheds, and salinity 
in the estuaries of Everglades National Park. This relationship can be used to locate the 
freshwater line in the respective coastal rivers, and to predict the salinity of coastal 
estuaries and lagoons. There are two distinct watersheds in Everglades National Park: 
the Taylor Slough drainage discharges into Florida Bay, and the Shark River Valley- 
Everglades drainage feeds the Whitewater Bay - Shark River and lower Ten Thousand 
Islands estuaries. The precision of prediction of salinity increases with proximity to 
the land from which the water supply comes. Errors in prediction are greatest in 
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