projects > freshwater flows into northeastern florida bay > work plan
Project Work Plan
Greater Everglades Science Program: Place-Based Studies
Project Work Plan FY 2003
A. GENERAL INFORMATION:
Project Title: Freshwater Flows into Florida Bay
Project Summary: In South Florida, changes in water-management practices to accommodate a large and rapidly growing urban population along the Atlantic coast, as well as intensive agricultural activities, have resulted in a highly managed hydrologic system. This managed system altered the natural hydrology of the Everglades ecosystem, including Florida Bay. During the last few decades, Florida Bay has experienced seagrass die-offs and algal blooms. Both are signals of ecological deterioration that has been attributed to increases in salinity and nutrient content of bay waters. With plans to restore water levels in the Everglades to more natural conditions, changes also are expected in the amount and timing of freshwater discharge through the major creeks into Florida Bay. Flow through the estuarine creeks through the Buttonwood Embankment and into Florida Bay is naturally controlled by the water level in the Everglades; regional wind patterns; and to a lesser extent, tides. Florida Bay restoration requires an understanding of the linkage between the amount of freshwater flowing into the bay and the salinity and quality of the bay environment. Historically, there has been no accurate quantification of the amount of freshwater being discharged into Florida Bay from the mainland due to the difficulties of accurately gaging flows in shallow, bi-directional, and vertically stratified streams.
In 1995, the U.S. Geological Survey (USGS) began a study to gage several major creeks that discharge freshwater into northeastern Florida Bay. This study provides flow, salinity, and water-level data for model development and calibration and also provides baseline data for other physical, biological and chemical studies being conducted in the area. The study is being done as part of the USGS Place-Based Studies Program, which is an effort by the USGS to provide earth science information needed to resolve land-use and water issues. Results from the study will provide scientists with essential information along the Everglades wetland/Florida Bay transition zone where data were not previously available.
Project Objectives and Strategy: The project objectives are to determine the quantity, timing and distribution of freshwater flow into Florida Bay and adjacent estuaries, determine baseline hydrologic conditions and provide information on hydrologic change during the restoration process. Flow, water-level, and salinity data are collected at monitoring sites in estuarine creeks that connect Florida Bay with the Everglades. This project helps determine how freshwater flow affects the health of Florida Bay, a critical component of the CERP, and how changes in water-management practices upstream (Taylor Slough and C-111 basins) directly influence flow and salinity conditions in the estuary. The U.S. Army Corps of Engineers (USACE), South Florida Water Management District (SFWMD), USGS, Everglades National Park (ENP) and other agencies as well as universities are currently using the data from this study to answer specific research questions that will directly benefit the restoration effort.
Potential Impacts and Major Products: Flow and salinity data are critical for establishing performance measures used in the evaluation of CERP projects, such as the C-111 Spreader Canal and the Florida Bay, Florida Keys Feasibility study. Flow into Florida Bay affects salinity, nutrient and sediment transport, and chemical characteristics of the bay, which in turn, affect the health of the ecosystem. Everglades and Florida Bay researchers require measured flow data to compute nutrient, chemical, and sediment fluxes. These flux computations are then used in biological and physical studies of the Florida Bay ecosystem. Additionally, accurate measures of freshwater flow, water level, and salinity are used as input to hydrodynamic models of Florida Bay and the Everglades and for water-budget determinations. Decisions regarding restoration based on scenario testing from hydrodynamic models have a higher degree of confidence when the models are confirmed with measured field data. Lastly, there is a continuing critical need to monitor any flow distribution changes that occur during the CERP implementation to help understand the effects of water-management changes to the watershed.
Products for FY 2003 and FY 2004
The USGS, SFWMD, USACE, and many universities working in the Everglades ecosystem are currently using data from this study. The Florida Bay Program Management Committee is using data from this project in the development of the Florida Bay Standard Data Set for use in constructing hydrodynamic models of the Everglades system.
B. WORK PLAN
Title of Task 1: Freshwater Flows into Northeastern Florida Bay
Task Summary and Objectives: The project objectives are to determine the quantity, timing and distribution of freshwater flow into northeastern Florida Bay. Also, a primary objective is to determine baseline hydrologic conditions and provide information on hydrologic change during the restoration process. Flow, water-level, and salinity data are collected at monitoring sites in estuarine creeks that connect Florida Bay with the Everglades.
Work to be undertaken during the proposal year and a description of the methods and procedures:
At all instrumented sites (West Highway Creek, Stillwater Creek, Trout Creek, Mud Creek, Taylor River, Upstream Taylor River and McCormick Creek), data collection includes continuous 15-minute interval measurements of water level, water velocity, salinity, and temperature and periodic measurements of discharge for acoustic Doppler velocity meter calibrations. All raw data at the instrumented sites are recorded by an electronic data logger and transmitted every 4 hours by way of the Geostationary Operational Environmental Satellite (GOES) into the database of the USGS Miami Subdistrict office. Data collection at the non-instrumented sites (East Highway Creek, Oregon Creek, and East Creek, and Joe Bay creeks) are limited to periodic discharge and salinity measurements. Acoustic Doppler Current Profilers (ADCP's) mounted on a boat are used to measure discharge at the Florida Bay monitoring stations. The ADCP uses the Doppler shift in returned acoustic signals reflected by particles suspended in the water to determine the velocity of moving water. This instrument also has the capability to measure water depth and direction of the boat based on acoustic reflections from the streambed. Discharge and flow direction are both calculated from information provided by the ADCP and computer software. The mean water velocity for the stream or creek section is calculated by dividing the total discharge (measured with the ADCP) by the cross-sectional area corresponding to the water level at the time of measurement. The cross-sectional area is computed by using the site-specific stage area ratings. Water-level data were recorded to determine water depth and to calculate the stage-dependent cross sectional area. Water-level data are collected with an incremental shaft encoder equipped with a pulley, stainless-steel tape, weight, and float inside an 8 in. (inch) polyvinyl chloride pipe stilling well.