Near the beginning of the 20th century, modifications to the natural hydrologic system of southern Florida, including the Everglades, were undertaken to furnish the urban and agricultural demands of an expanding population. These changes have evolved into an extensive system of canals, levees, pump stations, gated control structures, and water-conservations areas used for the drainage of wetlands, flood control, ground-water replenishment, and the prevention of saltwater intrusion. These modifications to the natural hydrologic system of southern Florida have resulted in the alteration of historical hydropatterns, especially as they relate to the Everglades.

A vital component in ecosystem restoration is the understanding of prerestoration water quality. Because of an expanding population along the southeastern coast of Florida, the health of Biscayne Bay has been threatened by nutrient-laden discharges from the east coast canals, resulting from increased urbanization and agricultural practices. Plans call for extensive changes to the current watermanagement system to restore natural flow patterns into Everglades National Park. These changes--including the filling of canals, removal of levees, and rechannelization of canal discharges to Biscayne Bay--potentially could affect the fragile Biscayne Bay ecosystem. The U.S. Geological Survey conducted a study designed to understand nutrient concentration and distribution within the east coast canal system, compare sampling methods to determine which methods adequately represent stream cross-section water quality, and develop models for the estimation of nutrient loads from the canals to Biscayne Bay. Data were collected during the 1996 and 1997 water years with a report prepared during the 1998 water year.

Major findings from the project are as follows:

In an attempt to understand current and historical water quality, long-term trends in water quality from two surface-water sites potentially affected by the restoration effort, Miami Canal (S-26) and Tamiami Canal - Forty-Mile Bend to Monroe, currently are being investigated. Miami Canal is one of the principal canals that discharges to Biscayne Bay, and the Tamiami Canal site represents flow from the Big Cypress National Preserve to Everglades National Park. Extraneous variation in water-quality data can occur due to both seasonality and discharge. The specific statistical approach undertaken in this study involves compensating for the effects of seasonality and discharge. The application of the Seasonal Kendall Trend Test on residuals from concentration/discharge relations developed from the use of ordinary least squares regression techniques or on unadjusted concentrations was used in the study. This approach removes extraneous variation in the data so that specific anthropogenic processes that have occurred and have affected water quality over time are not "masked" and can be discerned. Trends at the two sites will serve as indicators of both improvement or deterioration in water quality with time.

Study results will identify statistically significant trends and provide quantitative information as to the rate of change in specific constituents over time. Information gained from this study will provide water managers and planners with a better understanding of current water-quality conditions prior to the initiation of restoration efforts and also an understanding of the interdependence of Biscayne Bay and the Everglades ecosystems. Additionally, the information will provide a valuable resource for comparison of prerestoration and postrestoration water quality as well as a means of determining the effectiveness of restoration efforts in enhancing water quality in the Everglades and Biscayne Bay ecosystems.

(This abstract was taken from the Proceedings of the South Florida Restoration Science Forum Open File Report)