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The intensive drainage and associated agriculture south of Lake Okeechobee in the EAA has caused a tremendous loss of organic soils. The compaction and oxidation of organic soils in the agricultural lands south of the lake was one of the first observed environmentally destructive effects of large-scale drainage. In most areas, 5 ft or more of organic soil had been lost by 1984 (Stephens and others, 1984). A recent calculated rate of loss in the EAA is about 1 in/yr (Barry Glaz, Department of Agriculture, written commun., 1994). The maximum thickness of this soil, which is underlain by limestone, was initially only 12-14 ft. The process of oxidative loss of soil continues, although the process has been slowed in some locations by reflooding fallow fields and maintaining a high water table.
Such a large loss of soil has affected hydrology and ecology of the Everglades in many ways. The altitude gradient from the upper to the central Everglades has been greatly affected by the soil loss. The loss of altitude has meant a loss of the hydraulic head that once caused water to flow south. The movement of water from north to south now requires pumpage, and the pumpage effort necessary to move water continues to increase with time as the soil continues to subside. The soil loss also has reduced water-storage capacity, which has caused a reduction in the ability of the area to absorb water and mediate seasonal and long-term variations in rainfall. The problems caused by soil loss are magnified by the enormous spatial extent of the loss. In fact, the loss is not confined to the EAA, but actually extends into the northern parts of WCA-1 and WCA-3A, where additional soil has been lost as a result of the diversion of water.
U.S. Department of the Interior, U.S. Geological Survey
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Last updated: 15 January, 2013 @ 12:43 PM(KP)