Spatial and Temporal Patterns of Surface Water Quality on the Big Cypress Seminole Indian Reservation
Dianne Owen and John C. Volin
Florida Atlantic University, Davie, FL
William A. Dunson
Pennsylvania State University, University Park, PA
The Seminole Tribe of Florida is implementing a designated Critical Project, the Water Conservation Plan (WCP), as part of the Comprehensive Everglades Restoration Plan on the Big Cypress Seminole Indian Reservation. The WCP will deliver water from canals on the northeastern side of the Reservation into a system of impounded wetlands on the northwestern side. A portion of the water released from these impounded wetlands will flow into the relatively intact riparian slough system that occupies the southwestern portion of the Reservation. In conjunction with the WCP, we are conducting a series of studies that will provide baseline information on water quality on the Big Cypress Seminole Indian Reservation.
Like much of southern Florida, high levels of phosphorus greatly impact water quality in surface water and canals traversing the Reservation. Prior to major anthropogenic influences levels are believed to have been in the range of 10-30 ppb total phosphorus, yet today many canals on the Reservation often attain substantially higher levels.
Within the Big Cypress region, measurements of surface water quality have been taken for more than 10 years, but nevertheless there remains a substantial gap in our knowledge with regard to comprehensive water quality studies. As a consequence, the 10 ppb standard for [P] is based largely on water quality studies conducted within the sawgrass marsh Everglades while the forested Big Cypress region of the Greater Everglades ecosystem has been largely ignored.
The objective of our studies has been to examine the spatial and temporal patterns of surface water quality on the Big Cypress Seminole Indian Reservation. As a first step, we conducted time series analyses of an extensive database of biweekly surface water quality sampled at 10 sites across the Reservation. A predictive model of TP concentrations in surface water leaving the Reservation was developed through multiple regression analysis of inflow and outflow TP concentrations. Rainfall patterns were investigated using daily rain data recorded at seven stations located on or near the Reservation within the regional watershed. The relationship between rainfall and surface water parameters was explored by time series and multiple regression analysis using rainfall trend models. These analyses showed that TP concentrations entering the Reservation are significantly higher than at outflow points. TP concentrations are positively correlated with rainfall trend models and correlations are significantly improved when the rainfall time series is lagged by three to four weeks. These findings point to mobilization of phosphorus by rainfall as a primary source of phosphorus in surface water entering the Reservation.
We have also examined surface water quality within an impounded forested wetland receiving high-nutrient point-source input from agricultural effluents. Mean TP levels at interior sites and the outflow site were significantly lower than inflow levels. Comparison of relative changes in total phosphorus and chloride ion concentrations provided evidence that biological or chemical processes were the primary mechanism of phosphorus reduction within the impoundment. In parallel with this high-nutrient point-source study, we studied water quality in a relatively low-nutrient nonpoint-source, the Kissimmee Billie Slough, a semi-pristine forested slough located on the southwestern boundary of the Reservation. Overall nutrient levels were found to be generally low across its entire north-south expanse, with mean total Keldjahl nitrogen (TKN) and total phosphorus (TP) concentrations of 1.0270.08 mg l-1 and 0.0240.003 mg l-1, respectively. Preliminary results from this study suggest that potassium, rather than phosphorus, may act as the limiting nutrient within this system. Mean K concentrations within the study basin were extremely low,(0.8430.103 mg l-1), approximately seven times lower than concentrations typically found in other open-water oligotrophic sloughs in the sawgrass marsh Everglades.
We are currently conducting a forest stand-level study within the Kissimmee Billie Slough to determine whether potassium is more limiting to plant growth than phosphorus in this system. Data collected from this study will assist us in determining the fate of surface water nutrients within the Reservation and improving the quality of surface water as it traverses the Reservation and is discharged into the Everglades.
Dianne, Owen, Florida Atlantic University Environmental Sciences, 2912 College Avenue, Davie, FL 33314, Phone: 954-236-1115, Fax: 954-236-1099, , Water Quality