The National Park Service (NPS) maintains hydrologic monitoring stations for measuring water level (stage) and water quality in Big Cypress National Preserve and Everglades National Park (fig 1). The data collected at these stations provide a historical baseline for assessing hydrologic conditions and making a wide range of management decisions. We have assessed selected waterquality data at these stations and at nearby canal sites for the period of record, 1959-2000, to define baseline conditions and to evaluate whether long-term trends have occurred.

Figure 1. Hydrologic monitoring stations in Big Cypress National Preserve and Everglades National Park [larger image]

Long-term changes in water levels, flows, water management, and upstream land use also affect water quality in Big Cypress National Preserve and Everglades National Park, based on analysis of available data (1959-2000). Specific conductance and concentrations of chloride increased in the Taylor Slough and Shark River Slough in the 1980s and early 1990s; for example, chloride concentrations more than doubled from 1960 to the 1990, primarily due to greater canal transport of high-dissolved solids into the sloughs. Some of the long-term trends in sulfate and total phosphorus were likely attributable to the high percentage of values reported as “less-than” and “zero”, and to changes in reporting levels over the period of record. High spikes in nutrient concentrations were evident during dry periods of the 1980s and attributable to (1) increased canal inflows of water that is nutrient-rich relative to marsh inflows, (2) increased nutrient releases from breakdown of organic bottom sediment, or (3) increased build-up of nutrient waste from concentrations of aquatic biota and wildlife in remaining ponds. Long-term changes in water quality over the period of record are less pronounced in the western Everglades and the Big Cypress Swamp, however, seasonal and drought-related changes are evident.

Water quality varies spatially across the region due to natural variations in geology, hydrology, and vegetation and because of differences in water management and land use. Nutrient concentrations are relatively low in Big Cypress National Preserve and Everglades National Park compared with concentrations in parts of the northern Everglades that are near agricultural and urban lands. Concentrations of total phosphorus generally are higher in Big Cypress National Preserve (median values, 1991-2000, were mostly above 0.015 mg/L) than in Everglades National Park (median values, 1991-2000, below 0.01 mg/L), probably because of higher phosphorus in natural sources such as shallow soils, rocks, and ground water in the Big Cypress region than in the Everglades region. Concentrations of chloride and sulfate, however, are higher in Everglades National Park (median values in Shark River Slough, 1991-2000, mostly above 2 mg/L sulfate and 50 mg/L chloride) than in Big Cypress National Preserve (median values, 1991-2000, less than 1 mg/L sulfate and at most sites less than 20 mg/L chloride) probably due to the canal transport system that conveys more water from an agricultural source into Everglades National Park than into Big Cypress National Preserve.

Trace elements and contaminants such as pesticides and other toxic organics are in relatively low concentrations in Big Cypress National Preserve and Everglades National Park compared with concentrations in parts of the northern Everglades, which are near agricultural and urban sources. Concentrations rarely exceeded aquatic life criteria in Big Cypress National Preserve and Everglades National Park. Atrazine was the only pesticide that exceeded the criteria (in 2 out of 304 samples). The pesticides p, p'-DDE, lindane, and heptachlor expoxide exceeded criteria in canal bed sediments in 16, 2, and 1 percent of the samples, respectively.

Contact: McPherson, Benjamin F. 10500 University Center Dr., Suite 215, Tampa, FL, 33612, Phone: 813-975-8620, ext 126, Fax 813-975-0839, bmcphers@usgs.gov

(This abstract was taken from the Greater Everglades Ecosystem Restoration (GEER) Open File Report 03-54)

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