Continuous Hydrologic Data in Florida Bay Channels
Clinton Hittle and Grant Poole
U.S. Geological Survey, Center for Water and Restoration Studies, Miami, FL
Hydrologic data from six channels within Florida Bay (fig. 1) are being collected
by the U.S. Geological Survey (USGS) to help understand flow characteristics
and better define the transport of post-larval Pink Shrimp into and out of the bay.
The data will improve hydrodynamic and biological models being developed for
use with the Comprehensive Everglades Restoration Plan (CERP), a goal of
which is to improve the quantity, quality, timing, and distribution of flows within
the Everglades ecosystem. Continuous water velocity, stage, salinity, and
temperature data have been collected at 15-minute intervals since January 2002.
Monitoring stations are co-located with post larval pink shrimp nets managed by
the USGS, National Oceanographic and Atmospheric Administration (NOAA),
and the University of Miami Rosenstiel School of Marine and Atmospheric
Science (RSMAS).
Figure 1. Location of Florida Bay monitoring stations.
All stations have salinity/temperature probes installed at about mid depth in the
channel; probes are cleaned and calibrated during routine site visits. Elevations
were established on each station in 2002 by the USGS and are referenced to the
North American Vertical Datum of 1988 (NAVD 88). Elevation data was
computed using a helicopter-based differential global positioning system coupled
with a mechanical height finder (fig 2). The elevation data established at each
monitoring station allows for comparisons of water level between the sites.
Figure 2. Helicopter based survey method.
Acoustic Doppler Velocity Meters (ADVM) continuously monitor flow
conditions and water levels within the channels. The ADVM measures an average
water velocity within a fixed sample volume. Continuous channel discharge is
computed using velocity data collected from the ADVM and a boat mounted
Acoustic Doppler Current Profiler (ADCP). Regression analysis is used to relate
the ADVM velocity to mean measured velocity calculated during ADCP
discharge measurements. The resulting equation, known as an index velocity
rating, converts all ADVM index velocities into approximate mean channel
velocities. These corrected velocities are multiplied by the channel area to
produce continuous discharge record. Acquiring ADCP discharge measurements
over the entire range of flow conditions expected to occur at the site improves this
computation method. Figure 3 shows the relation between index velocities and
ADCP mean measured velocities at Whale Harbor Channel.
3.00
2.50
ADCP MEAN MEASURED VELOCITY ,
IN FEET PER SECOND
EXPLANATION
-2.00
Vi
V
Calibration rating
Measured
Index velocity
ADCP mean measured velocity
R2
Coefficient of determination
ADCP
2.00
1.50
1.00
Acoustic Doppler Current Profiler
0.50
-1.50
-1.00
-0.50
0.00
0.00
-0.50
0.50
1.00
1.50
2.00
2.50
-1.00
-1.50
V = 1.13Vi - 0.03
2
R = 0.99
-2.00
-2.50
ADVM INDEX VELOCITY, IN FEET PER SECOND
Figure 3. Velocity relation for the Whale Harbor monitoring station
The continuous discharge data from these sites will benefit studies that require
estimates of total hydraulic transport into and out of the bay, while the continuous
data for all parameters will be valuable for verifying future simulations of Florida
Bay hydrodynamics.
Clinton D. Hittle, U.S. Geological Survey, 9100 N.W. 36th Street, Suite 107,
Miami, FL 33178. Phone: 305-717-5815, Fax: 305-717-5801, cdhittle@usgs.gov