The estuaries of Florida's southwest coast are an integral part of the south Florida ecosystem. Nutrients are transported to these coastal waters by surface-water and ground-water flows from Everglades National Park (ENP) and Big Cypress Preserve, and by nearshore and offshore tidal currents. The quantities of water and nutrients discharged from streams and sloughs that flow to the coastal area from upland areas of ENP and Big Cypress Preserve currently are unknown.

As an element of the U.S. Geological Survey South Florida Ecosystem Program, water flows and nutrient loads for three major streams along the southwest coast of South Florida are currently (1997) being monitored. The three streams that were selected for continuous monitoring receive water from the Shark Slough drainage area and discharge to the Gulf of Mexico. Data collection began in 1996 and will end in 1998.

Continuous monitoring stations were established on the Broad, Harney, and Shark Rivers. The stations use in-situ sensors to measure stream velocity, water level, specific conductance, and temperature. Stream velocity is measured using an upward-looking acoustic Doppler profiler (ADP). Water level is measured using a pressure transducer. Specific conductance is measured using two four-electrode conductance sensors near the surface and bottom of the water column. Temperature is measured using an integral thermistor in the specific conductance sensors.

The Harney and Shark River stations were installed in October and November 1996. The Harney River station ADP malfunctioned and was replaced in January 1997. The Broad River station was installed in December 1996 to January 1997.

The in-situ sensors are calibrated and cleaned monthly. Stream discharge is measured monthly using an acoustic Doppler current profiler. Water-quality samples are collected monthly using a modified equal width increment method and are analyzed for total and dissolved nitrogen and phosphorus. The discharge measurements, water-quality, and in-situ sensor data will be used to compute velocity/water-level/discharge relations and discharge/nutrient load relations, which will then be used to estimate continuous discharge and nutrient loads for the three rivers.

The Broad River is the northernmost of the three rivers, and its monitoring station is located approximately 15 river kilometers from the river mouth. Stream-velocity data for January through May, 1997, ranged from approximately +40 cm/s downstream to approximately -40 cm/s upstream. The range in water level during this period was approximately 1.1 m. Specific conductance ranged from approximately 1,000 to 40,000 mS/cm for the same period. Measured discharge ranged from +20 to approximately -20 m3/s.

Total nitrogen concentrations for six samples from the Broad River ranged from 0.83 to 1.42 mg/L and dissolved nitrogen concentrations ranged from 0.71 to 1.12 mg/L. Total phosphorus concentrations were consistently 0.020 mg/L and dissolved phosphorus concentrations ranged from 0.002 to 0.010 mg/L.

The Harney River is located south of the Broad River and connects to Tarpon Bay. The monitoring station is located approximately 7 km from the river mouth. Stream velocity during January to May 1997 ranged from approximately +60 to -70 cm/s. The range in water level was approximately 1.8 m. Specific conductance ranged from approximately 1,200 to 50,000 mS/cm. Discharge ranged from approximately +140 to -150 m3/s.

Total nitrogen concentrations for five samples from the Harney River ranged from 0.70 to 1.26\x11mg/L and dissolved nitrogen concentrations ranged from 0.63 to 1.06 mg/L. Total phosphorus concentrations ranged from 0.020 to 0.030 mg/L, and dissolved phosphorus concentrations ranged from 0.009 to 0.020 mg/L.

The Shark River is the southernmost of the three rivers, and connects to Tarpon Bay, which provides a common link between the Harney and Shark Rivers. The monitoring station is located approximately 10 km from the river mouth. Stream velocity ranged from approximately +70 cm/s to -70\x11cm/s. The range in water level was approximately 1.4 m. Specific conductance ranged from approximately 1,200 to 50,000 mS/cm. Discharge ranged from approximately +120 to -120 m3/s.

Total nitrogen concentrations for four samples from the Shark River ranged from 0.63 to 1.03 mg/L and dissolved nitrogen concentrations ranged from 0.55 to 0.87 mg/L. Total phosphorus concentrations ranged from 0.010 to 0.020 mg/L, and dissolved phosphorus concentrations ranged from 0.006 to 0.020\x11mg/L.

Measurement of stream discharge and nutrient loads for the three rivers is still in its initial stages and will continue through 1998. These data will be used to identify flow and water quality changes in the rivers as water releases and pollution control methods for the Everglades are altered. Additionally, data from this study can be used by other scientists conducting ecological or hydrodynamic studies in the estuarine area. Initial data are available on a provisional basis from the USGS.

Back to Project Homepage