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Integrating Multiscale Observations of U.S. Waters
CASE STUDY I —MONITORING THE HYDROLOGYOF THE EVERGLADES IN SOUTH FLORIDA
The Florida Everglades (Figure 4-1) is one of the world’s largest freshwater wetlands. It was once a free-flowing river of grass that provided clean water from Lake Okeechobee to Florida Bay. The marshes and swamps acted as natural filters that recharged underground aquifers in the South Florida region.
Historically the pre-channelized Everglades hydrologic balance was maintained through long, slow, continuous, gravity flow of water. Because of the diversion of water, channelization of transient rivers, and loss of elevation through oxidation of soils, pump stations are now required to move water from canals to marsh areas or from one canal segment to another or to return seepage water that would otherwise be lost from the greater Everglades. Over 50 such stations now exist, pumping volumes ranging from ~200 cfs to ~4800 cfs (Susan Sylvester, SFWMD, written commun., November 2006).
Accordingly, today the releases from Lake Okeechobee are controlled. During normal climatic conditions, Lake Okeechobee outflows are able to meet the large water needs to the south of the lake. However, when the climate remains abnormally dry for an extended period (for one or two seasons), inflows may diminish to very low levels during the same period that demands on the lake will peak. Consequently, lake stages may fall very quickly to extremely low levels. Conversely, when climatic conditions are wetter than normal, large volumes of water enter the lake, coinciding with periods when water demands to the south will be minimal. These events cause lake stages to rise very quickly and require large volumes of water to be discharged to the Water Conservation Areas (WCAs) or to the St. Lucie and Caloosahatchee estuaries. Abrupt changes in flow or very large releases through the estuaries are harmful to these ecosystems.
The WCAs are the primary source of supplemental water for the highly developed urban areas along the southeast coast of Florida, with the lake being the alternate source. The WCAs were built as large water-storage impoundments in the Everglades to provide both water supply and flood protection for the urban areas. In addition to the agricultural and municipal water consumptive needs, water releases from the lake are required to meet the needs of the Everglades and the numerous coastal ecosystems. The WCAs and the Everglades National Park (ENP) are known today as the remnant Everglades. Water held in and released from the WCAs effectively recharges the Biscayne aquifer in some areas.
Over the past half-century measures taken to satisfy agricultural and urban development goals have degraded the Everglades ecosystems. To restore and maintain the vitality of these ecosystems as well as to enhance the reliability and quantity and quality of water supplies, and provide flood protection, the U.S. Army Corps of Engineers (USACE), the South Florida Water Management District and numerous other federal, state, local, and tribal partners involved in water