Readme File for the South Florida Hydrology Data Download


*Format for Hydrology Data

The data format used is comma-separated value (csv) and/or tab-delimited files that can be imported into most spreadsheet programs.

Water level is reported in feet as referenced to the North American Vertical Datum of 1988 (NAVD 88), discharge in cubic feet per second, specific conductance in micro-siemens per centimeter, salinity in parts per thousand (Land-Margin salinity is represented in practical salinity units), and temperature in degrees Celsius.


*Methodology

Several methods were used in the study to describe the magnitude and distribution of flow and salinity at the mangrove transition zone and along the southern coastline of Florida. Field data-collection procedures and discharge calculation techniques for instrumented stations are summarized below.

--Water level, temperature, salinity, and discharge

Data collected at instrumented sites included continuous (15-minute or hourly) measurements of water level, water velocity, salinity/specific conductance, temperature, and periodic measurements of discharge for index velocity calibrations. More information on index velocity techniques is discussed in Hittle and others (2001) and Morlock and others (2002), and Ruhl and other (2005). Stations with transmitting data loggers send field data every 1 to 4 hours into the database of the FISC Ft. Lauderdale office by way of the Geostationary Operational Environmental Satellite (GOES). Non-transmitting sites are routinely serviced and field data is manually uploaded to the USGS database.

Boat mounted acoustic Doppler current profilers (ADCP) were used to measure discharge at the estuarine 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 (Simpson 2002 and Oberg and others 2005). The ADCP also has the capability to measure water depth, flow direction, and speed 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 is calculated by dividing the total measured discharge by the cross-sectional area corresponding to the water level at the time of measurement (Sauer 2002 and Ruhl and others 2005).

Acoustic velocity meter (AVM) and acoustic Doppler velocity meter (ADVM) systems were used to measure continuous water velocity. The velocity measured by the ADVM systems represents an "index" of the mean water velocity. The index velocity is a measured velocity at the instrumented sites that can be used to compute the mean channel velocity.

Water level data are used to determine water depth and to calculate the stage-dependent cross-sectional area. Water level data were collected an incremental shaft encoder equipped with a pulley, stainless-steel tape, weight, and float inside an 8 in. polyvinyl chloride pipe stilling well (Sauer 2002), pressure sensors, or acoustic transducers. Corrections to water level data follow USGS quality assurance quality control protocols (Rantz and others 1982 and Sauer 2002).

Salinity is measured near the water surface and the bottom of the water column to help determine the presence of freshwater flow and to examine potential effects on the acoustic signals caused by salinity stratification. Continuous salinity measurements are important for describing the seasonal patterns of freshwater flow (wet/dry season) and for identifying bi-directional flow. Elevations of the continuous monitors are available upon request. Temperature is measured to acquire physical information on creek or wetland characteristics, and to monitor possible vertical gradients that also could affect acoustic signals. Due to biological fouling and electronic drift, the continuous monitor requires routine cleaning and calibration to maintain data quality. During the period of record (water years 1996-2003), continuous monitors were calibrated during site visits to ambient conditions using a reference probe (USGS National Field Manual). Ambient salinity conditions were measured with a portable reference probe that was calibrated and or verified against a range of laboratory specific conductance standards. The determination of fouling and drift errors from water year 2003 to current follow the guidelines set forth in Wagner and others (2005). Reference temperature probes are verified against a NIST thermometer prior to field trips. When in situ temperature measurements differ by more than 0.2¡C when compared to the reference temperature probe, the in situ probe is replaced.

--References

Hittle, C.D., Patino, E., Zucker, M., 2001, Freshwater Flow from Estuarine Creeks into Northeastern Florida Bay: USGS Water-Resources Investigation Report 01-4164, p. 32.

Morlock, S.E., Nguyen, H.T., and Ross, J.H., 2002, Feasibility of acoustic Doppler velocity meters for the production of discharge records from U.S. Geological Survey streamflow-gaging stations: U.S. Geological Survey Water-Resources Investigations Report 01-4157.

Oberg, Kevin A.; Morlock, Scott E.; Caldwell, William Scott, 2005, Quality-assurance plan for discharge measurements using acoustic Doppler current profilers: U.S. Geological Survey SIR 2005-5183.

Rantz, S.E. and others, 1982, Measurement and Computation of Streamflow Volume 1. Measurement of Stage and Discharge: U.S. Geological Survey Water Supply Paper 2175.

Ruhl, C.A., Simpson, M. R., 2005, Computation of discharge using the index-velocity Method in tidally affected areas: U.S. Geological Survey SIR 2005-5004.

Sauer, Vernon B., 2002, Standards for the analysis and processing of surface-water data and information using electronic methods: U.S. Geological Survey Water-Resources Investigations Report 01-4044.

Simpson, Michael R., 2002, Discharge measurements using a broad-band acoustic Doppler current profiler: U.S. Geological Survey Open-File Report 2001-1.

U.S. Geological Survey Office of Surface Water Technical Memorandum No. 2006.01.

U.S. Geological Survey, variously dated, National field manual for the collection of water-quality data: U.S. Geological Survey Techniques of Water-Resources Investigations, book 9, chaps. A1-A9, available online at http://pubs.water.usgs.gov/twri9A.

Wagner, R.J., Boulger, W.R., and Smith, B.A., 2006, Revised Guidelines and standard procedures for continuous water-quality monitors: site selection, field operation, calibration, record computation, and reporting: U.S. Geological Survey Techniques and Methods, Book 9, Chapter B.


--Everglades Land-Margin Ecosystem Hydrology Data (Subset of South Florida Hydrology Data)

---Instantaneous surface and ground water level

Instantaneous surface and ground water levels were initially recorded hourly. To better characterize tidal influence, the sampling interval was increased to every 15 minutes at lower estuary gages in 2003. At freshwater marsh gages, the sampling interval was increased to every 15 minute interval after 2006. To improve water level accuracy, 10-tip float/pulley potentiometers used for surface water were replaced with float/pulley SDI shaft encoders and passive resistance tape sensors were replaced with vented pressure transducer sensors for groundwater in 2003. All water levels were measured in decimal feet and referenced to the NAVD 88 datum.

---Instantaneous surface and ground water specific conductivity and salinity

Toroidal induction conductivity sensors were initially used to measure specific conductance (corrected to 25 degrees C) for instantaneous surface and groundwater measurements. At each gage, specific conductance was measured by pumping water through tubing from each well into a single measurement chamber. This method was problematic and discontinued in 2001, due to excessive data loss from power failure and equipment fouling. The pumping method was replaced with in situ sensors. In 2003, toroidal sensors were replaced with 2-electrode conductivity/temperature sensors or "sondes" to improve accuracy and reduce measurement drift. Specific conductance was initially done hourly on the half-hour and increased after 2003 to a 15 minute interval to coincide with water level sampling. Specific conductivity field measurements were measured in millisiemens per cm^2. Specific conductance values were converted into Practical Salinity Units (PSU) afterward within the database using the 1985 UNESCO standard formula (UNESCO, 1985).

---Instantaneous surface and ground water temperature

Supplemental thermistor temperature probes were added in 1999, because toroidal specific conductivity sensors did not output water temperature. Water temperature sampling for surface and groundwater toroidal/thermistors were replaced in 2003 with single 2-electrode conductivity/ temperature "sondes" for each well. Temperature was initially sampled hourly on the half-hour and increased after 2003 to a 15 minute interval to coincide with water level sampling. Water temperature data were recorded in degrees Celsius.

---Instantaneous rainfall

Instantaneous rainfall was measured only at gages free of tree canopy interference. Beginning in 1997, rainfall was only measured at gages LO4 and CH2. Additional rain gages were added at gages SH1, SH2, SH5, LO1, LO2 and BSC from 2000-2001. Rain was measured with funnel style pulse tipping buckets (0.01 inch per tip). Rainfall measurements were recorded in decimal inches and stored as hourly summed data.

---Data collection, storage and retrieval

Instantaneous water data were recorded and stored on site within a data logger/controller powered with a solar photovoltaic (PV) 12 volt battery system. Logger stored data were initially transferred daily to the computer database at Everglades National Park (ENP) via a local RF radio network. After 2006, GOES satellite transmitters were used to send daily data from the loggers to GOES satellites using National Environmental Satellite Data and Information Service (NESDIS). Incoming data were transmitted via internet from NESDIS to ENP database. The data were reviewed, and validated at the project level (Anderson and Balentine, 2011).

---Calibration, data review and validation (QA/QC)

Quality Assurance and Quality Control (QA/QC) of the hydrologic data was fundamental to the USGS-BRD Land-Margin Ecosystem study. Gages located on the primary network transects (Shark and Lostmans) were scheduled for routine field visits every 30-60 days. Sensors were cleaned, calibrated and logger data were manually collected during each field visit. As needed, repair or replacement of faulty equipment was done.

Secondary network transect gages (CH1, CH2, LO4) were scheduled for visits every 90-120 days. Gage visits were made more frequently in response to observed data irregularities, or evidence of equipment failure and data loss. Monitoring equipment was calibrated or replaced (if inoperable) when field measured values exceeded acceptable study tolerance ranges. Instantaneous data were transferred to the USGS South Florida Information Access (SOFIA) web portal after project data was locally reviewed for quality assurance and control (QA/QC) and validation. Data is considered _furnished_ data to the USGS SOFIA hydrologic database (Larsen, 2008).

--References

Anderson, G.H., and K.M. Balentine. 2011. Standard Operating Procedures for USGS-BRD Land-Margin Ecosystem Study hydrological instrument calibration and quality control of physical water parameter data collected in Everglades National Park. BRD-USGS unpublished report. Homestead, FL, 29 p.

Larsen, M.C. 2008. Water Resources Discipline Policy on Accepting Furnished Records. U.S. Geological Survey, WRD Discipline Policy Memorandum 2008.01. Reston, VA.

UNESCO. 1985. The International System of Units (SI) in Oceanography. Techn. Pap. Mar. Sci., 45: 124 p.


*Further Information 

Further information on this study, including additional data, metadata, format, methodology, location maps, and sites listings can be found at:
http://sofia.usgs.gov/exchange/sfl_hydro_data/index.html