Okeechobee, Lake, Florida, USA
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OKEECHOBEE, LAKE, FLORIDA, USA Paul V. McCormick1, R. Thomas James2 1 Joseph W. Jones Ecological Research Center, Newton, GA, USA 2 South Florida Water Management District, West Palm Beach, FL, USA
Introduction Lake Okeechobee is a large (1,730 km2), shallow (mean depth 2.7 m) subtropical lake located at the center of the Kissimmee-Okeechobee-Everglades watershed of southern Florida (Figure 1). The present-day lake contains three distinct ecological zones (Figure 2: Havens and Gawlik, 2005): a deeper pelagic zone underlain by mud sediments with waters high in nutrients and resuspended sediments, a shallower nearshore zone underlain by sand and peat sediments with varying water quality and coverage of submerged aquatic vegetation, and a littoral zone of sand and peat that is lower in nutrients and supports a diverse emergent wetland plant community that provides critical foraging and breeding habitat for much of the lake’s fauna. Direct rainfall, most of which falls during the summer wet season, contributes over half of the water entering the lake, with much of the remainder coming from the lake’s major tributary, the Kissimmee River, to the north. Due to its large surface area and warm climate, roughly two thirds of the lake’s water losses are due to evapotranspiration, with water releases to estuaries on Florida’s east and west coast, agricultural lands, and the Florida Everglades accounting for the remainder. The lake is managed as a multipurpose resource that provides significant economic and environmental benefits to the region. It plays a central role in regional flood control and water supply for more than seven million people (U. S. Census Bureau, 2010). The lake is used heavily by
both resident and migratory water birds, including threatened and endangered species (Audubon of Florida, 2005), and contains an internationally recognized sports fishery that provides more than US $17 million annually to the local economy (Bell, 2006).
Pre-settlement condition The lake formed approximately 6,000 years BP in a large, shallow depression during a period of increasing rainfall and sea level rise following the last glaciation (Brooks, 1974). The depth of the lake increased in tandem with the accretion of deep peat soils in the sawgrass (Cladium jamaicense) wetlands of the Florida Everglades to the south, which formed a natural dam that had raised lake levels by 4–5 m by the late nineteenth century (Brooks, 1974). The Everglades also served as the sole natural outlet from the lake, which discharged large volumes of water seasonally as sheet flow across its broad southern shoreline. In addition to this direct connection to the Everglades, the pre-settlement lake was bordered on all other sides by a nearly continuous fringe of herbaceous and forested wetlands (Lodge, 2004). Human modifications Lake Okeechobee has undergone substantial changes during the past century as a result of human development of the southern Florida peninsula (Blake, 1980). A series of regional drainage projects began in the 1880s to control Lak
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