Mark Zucker
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. 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.
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Patino, Eduardo Zucker, Mark
Prior to the development of currently available acoustic instruments, it was very difficult to gage flows in streams discharging into Florida Bay. Standard methods for field data collection and flow computations are impractical and inaccurate because of the low velocities, flow reversal, and bi-directional flow in which high-salinity water flows inland under freshwater flowing out to the bay. With today's state-of-the art acoustic instrumentation, such as the Acoustic Velocity Meter (AVM) and the Acoustic Doppler Current Profiler (ADCP), it is possible to accurately gage flows in this environment because of the ability of these instruments to quickly measure low or rapidly changing water velocities, even during stratified or bi-directional flow. AVM systems have proven to be accurate instruments in the measurement of water velocities along a horizontal plane across stream and can be permanently installed to collect continuous velocity data that, along with water-level data, are used to produce continuous records of discharge.
ADCP instruments are used to measure water velocities in three dimensions. These measurements are then used to calculate the total flow through a stream section at a given time. The ADCP uses the Doppler shift from four acoustic beams sent downward in set angles to measure the velocity of water, depth, and distance traveled across the stream transect. Field measurements made with the ADCP's are used to develop relations between AVM velocities and discharge at gaged sites.
With the assistance of Everglades National Park, discharge measurements were made with ADCP's near the mouths of the major streams flowing into Florida Bay. Results of these measurements verified the applicability of ADCP's for discharge measurements under these environmental conditions, provided data on high flows into the bay, and helped in the understanding of flow patterns for each of the measured streams.
Project plans are to instrument selected streams flowing into Florida Bay with AVM's and temperature and specific conductance sensors in order to measure most of the total freshwater flow from the mainland into the bay. Sites are located along the mainland coast of east Florida Bay and represent most of the freshwater flowing south into the bay from Taylor Slough and the C-111 Canal basins. Three of these sites (Trout Creek Canal station and two C-111 Canal stations) are instrumented and maintained by Everglades National Park. Monthly ADCP discharge measurements are planned for rating AVM systems, and monthly collection of water samples are planned for total nutrient analysis.
1. Continuous 15 minute-data on flow, water level, salinity and temperature collected from the creek monitoring stations will be either transmitted via satellite to the USGS office in Miami, Florida, or collected during site visits and made available on the USGS SOFIA website.
2. A report on the freshwater flow and salinity data or 'standard data set', to be used in describing Florida Bay for physical, and biological model applications will be produced.
3. As Everglades restoration proceeds, documentation of changes in the flow and salinity to northeastern Florida Bay will be provided.
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Data collection includes continuous 15-minute interval measurements of water level, water velocity, salinity, and temperature data and periodic measurements of discharge for acoustic Doppler velocity meter (ADVM) calibrations at West Highway Creek, Stillwater Creek, Trout Creek, Mud Creek, Taylor River at Mouth, upstream Taylor River, McCormick Creek, Jewfish Creek, Joe Bay 8W and Joe Bay 2E. Monitoring stations where only discharge and water-level are collected include East Highway Creek and Oregon Creek. Salinity only sites include Joe Bay 1E and Joe Bay 5C. Field 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 CWRS office. Nontransmitting stations include Joe Bay 1-2E, 5C, 8W, East Highway Creek and Oregon Creek. Boat mounted acoustic Doppler current profilers (ADCP) are used to measure discharge in the estuarine creeks mentioned above. The ADCP uses the Doppler shift in returned acoustic signals reflected by particles suspended in the water to determine the velocity of moving water. Discharge and flow direction are calculated using the doppler software package. The mean channel water velocity is calculated by dividing the total discharge (measured with the ADCP) by the cross-sectional area determined by the water level at the time of measurement. The cross-sectional area is computed by using the site-specific stage area ratings, which is a function of water level. 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.
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U.S. Department of the Interior, U.S. Geological Survey, Center for
Coastal Geology
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