|
Discharge Computation for Instrumented Sites |
Discharge was computed on a 15-minute interval at instrumented sites using mean water velocity and
the cross-sectional area of the channel. Velocity and area relations developed for each site were
used to calculate discharge time-series data for all instrumented sites along the northeastern
coastline of Florida Bay. The ADCP was used
to determine channel depth at specific distances across the width of each creek. These depths were
used with simultaneous stage readings to develop a relation between water level and total
cross-sectional area for the individual sites.
|
|
To develop a time-series record of mean water velocity for any stream using acoustic velocity data, a
relation must be established between the AVM or
ADVM velocities and directly measured
ADCP mean water velocity. Three case scenarios,
based on a velocity estimation model, describe flows under varying conditions at the instrumented sites
in Florida Bay. These scenarios are presented and discussed in Hittle and others (2001).
|
|
The velocity relation (discharge rating) for West Highway Creek was revised after publication of Hittle
and others (2001). Separate discharge ratings were originally required to compute positive and negative
flow, and the negative flow equation was stage dependent (Hittle and others, 2001). Equation 1 is a
simplified rating that was subsequently developed to compute mean positive and negative water velocities
for West Highway Creek between 1996-2000, independent of stage. The rating was developed using a simple
linear regression:
|
|
V = 0.874Vi 0.013 (1)
R2 = 0.96
|
|
where V is mean water velocity, Vi is acoustic line velocity and R2 is the
coefficient of determination. Equation 1 is based on the mathematical formula in
Hittle and others (2001, eq. 3).
|
|
Stillwater Creek, located in western Long Sound, was instrumented in 1999 to establish a better
understanding of freshwater flow entering Long Sound. Prior to instrumentation, Stillwater Creek
discharge was estimated using discharge from West Highway Creek; however, the estimation equation
R2 value was the lowest of all the creeks (table 2).
|
|
|
Table 2. Discharge estimation equations for noninstrumented sites
[Abbreviations: Q, discharge;
QWHWY is discharge value at West Highway Creek,
QMUD is discharge at Mud Creek,
QTAY is discharge value at Taylor River, and
QTRT is discharge at Trout Creek]
Station Name |
Discharge Estimation |
Primary Formula |
Coefficient of Determination (R2) |
Alternate Formula |
Coefficient of Determination (R2) |
East Highway Creek1 |
Q=0.44QWHWY - 5.4 |
0.95 |
Q=0.28QTRT - 5.4 |
0.92 |
Oregon Creek1 |
Q=0.25QWHWY - 0.43 |
0.90 |
Q=0.05QTRT + 11.8 |
0.85 |
Stillwater Creek1,2 |
Q=0.27QWHWY + 5.2 |
0.84 |
Not developed |
Not applicable |
East Creek3 |
Q=0.827QWHWY + 10.7 |
0.99 |
Q=0.76QTAY - 7.0 |
0.87 |
|
|
Upstream Taylor River, which is located about 2 mi north of the mouth of Taylor River, represents
wetland creek flows, whereas the Taylor River site represents flow through the coastal embankment.
The upstream site was instrumented in 1999 to obtain a better understanding of flow in creeks that
lie within the Everglades wetlands. There is no estimated record prior to the installation of this
site due to the present lack of correlation between the upstream and downstream Taylor River sites.
All currently instrumented sites, except for Upstream Taylor River and Stillwater Creek, have
continuous 15-minute record during water years 1996-2000 (table 3).
|
|
|
Table 3. Period of record for Florida Bay monitoring stations
[Period of record is given in water years, except where noted]
Station Name |
Type of Site |
Period of Record |
Estimated |
Continuous 15-minute |
East Highway Creek |
Noninstrumented |
1996 - 2000 |
Not applicable |
West Highway Creek |
Instrumented |
Not applicable |
1996 - 2000 |
Oregon Creek |
Noninstrumented |
1996 - 2000 |
Not applicable |
Stillwater Creek |
Instrumented beginning 1999 |
1996 - mid-1999 |
mid-1999 - 2000 |
Trout Creek |
Instrumented |
Not applicable |
1996 - 2000 |
Mud Creek |
Instrumented |
Not applicable |
1996 - 2000 |
East Creek |
Noninstrumented |
1996 - 2000 |
Not applicable |
Taylor River |
Instrumented |
Not applicable |
1996 - 2000 |
Upstream Taylor River |
Instrumented beginning 1999 |
Not applicable |
mid-1999 - 2000 |
McCormick Creek |
Instrumented |
Not applicable |
1996 - 2000 |
|
|
|