The public need for near real-time water data is more important now than ever before. Hydrologic data are a valuable source of information used for various tasks, such as the design of dams, bridges, and culverts and the forecasting of potential floods or droughts. Today, the U.S. Geological Survey (USGS) in Florida posts data from nearly 700 real-time surface-water, ground-water, and water-quality stations across the State on the Internet at URL http://waterdata.usgs.gov/fl/nwis/rt/. These permanent, real-time stationsmany of which are in tidal zonescan be supplemented with temporary stations (not real time) to measure coastal surge during extreme storms (for example, see "Predicting Flooding and Coastal Hazards," this issue, and "Monitoring Hurricane Wilma's Storm Surge," Sound Waves, February 2006).
Satellite Telemetry in Florida
In 1972, staff from the USGS office in Miami installed the State's first Data Collection Platform (DCP) in the Everglades, as part of a project with the National Aeronautics and Space Administration (NASA) to test the performance and reliability of a Data Collection System (DCS), using the LANDSAT-1 satellite as the data-relay platform. The DCP collected water-level and precipitation data in the remote field location and transmitted it to the Goddard Space Flight Center in Maryland via LANDSAT-1. After preliminary processing at the flight center, the data were sent in teletype messages two to three times per day to the USGS office, where they were entered into a programmable calculator for processing into the final product. When the final calculations were completed, the data were transferred via teletype to the water-management agencies. Thus, in 1972, getting data from the point of collection to the users took approximately 2 hours, required several steps, and was not automated.
After the initial test project in 1972, additional DCPs were installed each year to meet the needs of water-management agencies and the public, and by 2000, a total of 353 USGS DCPs were transmitting near-real-time water data in the State of Florida. The number of DCPs has increased since then: as of March 21, 2007, a total of 683 USGS DCPs were transmitting in Florida.
Today, DCP data are received via the Geostationary Operational Environmental Satellite (GOES). The GOES satellite appears motionless as it orbits the Earth because it is located in the equatorial plane, approximately 23,000 mi above the Earth's surface. Data from the GOES satellite are received by the DCS (Data Collection System) Automated Processing System (DAPS) in Wallops, Virginia. DAPS is a centralized computer-based processing unit that monitors the GOES satellite for new transmissions. Each DCP has a scheduled transmission interval that ranges from 1 to 4 hours, although during flood events, the DCP can be programmed to transmit as often as the recording interval of the data (for example, every 15 minutes). DAPS distributes the new transmissions to USGS receiving stations through the domestic communications satellite (DOMSAT). Raw transmissions from DOMSAT are translated into a computer-readable format by using a USGS decoding program, and then are uploaded to the USGS National Water Information System Web page (NWISWeb) at URL http://waterdata.usgs.gov/nwis/rt/. The entire automated process, moving data from the gage to end users, takes only a few minutes.
Data Users and Benefits
Hydrologic data can assist various users, such as water-management and emergency-operations agencies, scientists, engineers, transportation users, and recreational water users to (1) evaluate water-use trends and plan for future use, including setting regulatory statutes on water levels, flow, and water-quality parameters; (2) predict and prepare for floods and droughts; (3) regulate reservoir levels and releases from reservoirs; and (4) navigate streams safely. The types of hydrologic data collected and published throughout Florida include stage, elevation, streamflow, water velocity, water temperature, salinity, specific conductance (related to salinity), dissolved oxygen, and weather parameters, such as precipitation, barometric pressure, wind speed and direction, humidity, and temperature.
Timely data delivery is imperative for decision makers to use the data efficiently in making critical decisions, such as forecasting a flood and evacuating and closing roads in low-lying areas. Timely delivery can minimize the loss of life and reduce property damage if sufficient time is available to move property out of the predicted area of flooding.
Another benefit of having the gaging network function in real time is that if a DCP malfunctions (for example, because of battery failure, instrument failure, or vandalism), a hydrographer is alerted and can make an immediate field trip to the gage location to rectify the problem, thus reducing the loss of data to the end user. Before the advent of DCPs and real-time data, if a data logger failed the failure would not be detected or fixed until the next scheduled field trip, usually every 6 to 8 weeks. Such delays sometimes resulted in loss of data for a significant period. In the infancy of USGS stream-gage data collection, data for missing periods could not always be estimated because there were no nearby gages to use as a comparison; today, streamflow data for nontidal streams can almost always be estimated by using a hydrographic comparison of upstream or downstream gages. In fact, having several gages on one stream helps the National Weather Service, emergency-management officials, and others more accurately determine the timing and magnitude of floods.
Real-Time Status in Florida
The USGS in Florida is striving to have 100 percent of the continuous-record gaging network available to the public in real time. Overall in Florida, 70 percent of all continuous-record gages are reporting on DCPs in real time, including 86 percent of surface-water, 46 percent of ground-water, and 84 percent of water-quality gages. The distribution of continuous-record stations varies across the State, depending on cooperator and USGS needs versus cost. Funding availability for the gaging program is the most significant factor in determining how quickly the USGS in Florida will achieve its goal of 100 percent of all continuous-record gages being available to the public in real time.
Not only are real-time data available on NWISWeb, but also historical daily values and various statistics for gages throughout Florida can be viewed at and downloaded from URL http://waterdata.usgs.gov/fl/nwis/nwis. The availability of all these data is a real asset for society, allowing agencies and the public to make more informed decisions regarding the use of water resources in Florida and the Nation.
Note: The following publications, available at USGS libraries (URL http://library.usgs.gov/), contain additional information about the early use of satellite telemetry for USGS water data:
Shope, W.G., and Paulson, R.W., 1979, U.S. Geological Survey application of satellite telemetry for the support of hydrologic data collection, in Deutsch, Morris, Wiesnet, D.R., and Rango, Albert, eds., Satellite hydrology; proceedings of the Fifth Annual William T. Pecora Memorial Symposium on Remote Sensing, Sioux Falls, S.D., June 10-15, 1979: Middleburg, Va., American Water Resources Association, p. 60-64.
Wimberly, E.T., 1975, Satellite relay and processing of hydrologic data in south Florida: U.S. Geological Survey Water-Resources Investigations, no. 12-75, 19 p.
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