REAL-TIME SURFACE-WATER MONITORING IN NEW JERSEY, 2003

 A network of 93 gaging stations that provide surface-water stage, flow (discharge), and tide-level data on a “realtime” basis through satellite, radio, and telephone telemetry is operating (May 2003) in New Jersey through a cooperative 

effort of the U.S. Geological Survey (USGS) and other agencies. The stream data from these stations are transmitted every 

1 to 4 hours and then are immediately posted for viewing on the Internet. This fact sheet describes the “real-time” monitoring network, and the equipment used to measure stage and flow and to transmit the data for viewing on the Internet. 

Instructions for viewing the data are included. The agencies cooperating in the operation and maintenance of the “realtime” surface-water data network are

Background

This statewide network consists of several sub-networks that were created to provide time-critical surfacewater data as well as information on long-term hydrologic 

conditions and trends in stream stage, flow (discharge), 

and tide levels within the State of New Jersey and to make 

the data available quickly. The gaging stations in these 

“real-time” networks, located throughout New Jersey (fig. 

1), provide time-critical information for the monitoring of 

floods, droughts, and daily streamflow conditions needed 

for public safety; water-supply management; and the daily 

operations of water supply and receiving-water discharges. 

This combined statewide network, for example, provides 

data that allow for timely flood warnings to the public and 

evacuations in flood-prone areas. The system provides upto-date observations of drought conditions for the optimum 

management of water supplies and up-to-date information 

on streamflow conditions for fishermen, canoeists, kayakers, boaters, and other recreational users. In addition, the 

data from this network can be used to estimate the most 

recent stream and tide conditions at nearby stations that do 

not have satellite telemetry.

Surface-water stage and streamflow information typically is used by engineers, planners, water-supply managers, emergency-management personnel, and the general 

public for a variety of purposes. Some of the uses for this 

streamflow information include incorporation into the 

design of bridges, dams, flood detention and control strucU.S. Army Corps of Engineers 

U.S. Department of Defense 

N.J. Dept. of Environmental Protection 

N.J. Dept. of Transportation

Essex County, N.J.

Hunterdon County, N.J.

Somerset County, N.J. 

Union County, N.J. 

Brick Township Municipal Utilities 

Authority 

Perth Amboy Water Department

Princeton Sewer Operating Committee

Westwood Borough, N.J.

Lake Hopatcong Commission 

N.J. Water Supply Authority. 

REAL-TIME SATELLITE

STAGE GAGES

REAL-TIME TELEPHONE/RADIO

STAGE GAGES

EXPLANATION

CENTRAL

COASTAL NORTH

COASTAL SOUTH

NORTHEAST

NORTHWEST

SOUTHWEST

0 10 20 30 MILES

0 10 20 30 KILOMETERS

DROUGHT REGION

U.S. Department of the Interior

U.S. Geological Survey

USGS Fact Sheet FS-048-03

July 2003

Figure 1. Location of current and planned gages that transmit 

“real-time” stage data.
tures, and waterways, and consideration of up-to-date information on river water levels and streamflows for water-supply management, wastewater-treatment plant design and 

permitting, flood and drought warning and management, 

and long-term trend analysis. In addition, the general public 

often finds this information valuable for planning and decision making for outdoor recreational activities involving 

the State’s waterways. The most critical use of “real-time” 

data are for flood monitoring and the timely evacuation of 

residents and the general public from flood-prone areas. 

In addition, during droughts the “real-time” data are used 

to keep water-supply managers and the general public 

accurately informed so that sound and timely water-supply 

management decisions can be made. 

Description of the Network

Most continuous recording gaging stations are located 

on large streams with drainage areas of 10 square miles 

or more. The “real-time” statewide networks of gaging 

stations are part of several existing networks established 

for stream flood warning, coastal tide and storm-surge 

flood monitoring, and drought warning. Specifically these 

networks include the Passaic Flood Warning System, 

Somerset County Flood Information System, Rahway River 

and Pascack Brook Flood Warning Systems, New Jersey 

Tide Telemetry System, and New Jersey Drought Monitoring System. Fact sheets that describe the Somerset County 

Flood Information System (Summer, 1998a), Passaic 

Flood Warning System (Summer, 1998c), and Tide Telemetry System (Summer, 1998b) can be found at the http:

//nj.usgs.gov/ web site. 

Most “real-time” gaging stations report both current 

stage and streamflow conditions. Gaging stations located 

in coastal back-bay areas generally report only tide-stage 

information. Some “real-time” stations provide information 

on local weather and water quality. Other characteristics 

recorded and transmitted at these sites include, but are not 

limited to, water and air temperatures, wind direction and 

speed, rainfall, barometric pressure, dissolved oxygen, pH, 

specific conductance, and turbidity.

Recorder

Shelf

Floor

Water surface

Water surface

Valves Intakes

(From Wahl and others, 1995)

Satellite

radio antenna

Description of Data Collection and Reporting 

System 

The stream stage (the level of the stream typically 

measured in feet above a datum point) or tide level at each 

station in the network is automatically measured at 6- or 

15-minute intervals, and the value is stored by a data-collection platform (DCP) located on site (fig. 2, fig. 3, and 

fig. 4).

Every 1 to 4 hours, a burst of data is broadcast from 

the site to the National Oceanic and Atmospheric Administration’s GOES (Geostationary Operational Environmental 

Satellite) satellite and relayed to a ground station. The data 

then are retransmitted by the DOMSAT (commercial) satellite to a USGS ground station, decoded, and automatically 

posted to the USGS, New Jersey District, Internet web page 

for viewing (fig. 5). Radio and telephone telemetry at some 

of the surface-water stations provides either an alternate 

pathway or, for some critical surface-water stations, a more 

direct pathway for the transmission of “real-time” information. The stage data for most of the stream-gaging stations 

are used to compute the stream discharge (the flow of the 

stream, typically measured in cubic feet per second) using 

an established relation between stage and flow, referred to 

as a rating curve.

Figure 2. Typical “real-time” surface-water gaging station equipped 

with a data-collection platform and satellite antenna.

Figure 3. Schematic drawing of a stilling well and shelter at a streamgaging station.
GOES DOMSAT

Wallops, Virginia,

Command and

Data Acquistion Center

Internet

USGS

data system

Observation well

and instrument

shelter

 To ensure the accuracy of the data, each station is 

visited every 6 to 8 weeks by a USGS hydrographer who 

makes field measurements of stage and discharge, checks 

the automated systems, and performs maintenance on the 

equipment. The field measurements of stage and discharge 

then are used to verify the relation of stage to discharge.

Where to View Data 

The surface-water data from this network can be 

viewed by following these instructions:

1. Attach to the Internet web page, http://

waterdata.usgs.gov/nj/nwis/current/?type=flow/ . 

This page lists each gaging station in the network 

and indicates the latest reported data.

2. Choose a gaging station by clicking on its Station 

Number. This leads to a page that contains a hydrograph of the stage and discharge data for the last 7 

days (fig. 6) and a summary of the daily mean flow 

statistics. The hydrograph will have indicators for 

daily median flow and flood-stage levels, as appropriate.

3. The timeframe for a hydrograph can be modified 

from the past 7 days up to the past 31 days by changing the value for “Days” in the box located above 

the hydrograph and then clicking on the “get data” 

button. A new hydrograph will then be drawn. Note 

that clicking on the indicated text will draw a presentation-quality hydrograph that can be downloaded 

easily and printed by the viewer.

The daily mean flow statistics are provided on the web 

page to put the stage and discharge data in a historical context. The maximum, mean, and minimum flows (discharge) 

for the period of record for the gaging station are indicated. 

The 80, 50, and 20 percent exceedence values that are 

indicated are the flows that were surpassed by 80, 50, and 

20 percent, respectively, of all daily mean flows. The latest 

flow value (obtained from the table or from the hydrograph) 

can be compared to these statistics.

Because the stage and flow data are shown automatically, the message “Provisional data subject to revision” is 

Figure 5. Schematic drawing showing data transmission from a gaging station through satellite telemetry to users on the World Wide 

Web.

Figure 4. U.S. Geological Survey tide gage at Cape May Harbor in 

Cape May, N.J., which transmits tide elevation and meteorologic data 

via satellite and VHF radio for emergency management and other 

purposes. (Photograph by Peter B. Reilly, U.S. Geological Survey)
included on the web pages. If problems with the measurement, communication, or storage systems are found, revisions will be made to the USGS database at a later time to 

provide the corrected values. 

The surface-water stations with radio telemetry that are 

a part of the Passaic Flood-Warning System transmit on an 

event reporting basis and update as frequently as every 5 

minutes. This more frequent “real-time” data can be viewed 

at http://www.afws.net/ .

USGS, in cooperation with New Jersey Department 

of Environmental Protection and other agencies, regularly measures stage and flow at 27 other gaging stations 

in New Jersey. The data from these stations, although not 

posted on a “real-time” basis, are available on the web site 

http://waterdata.usgs.gov/nj/nwis/sw/ . Surface-water data 

for all stations routinely monitored by USGS, including 

those of the “real-time” network, are summarized in an 

annually published report (for example, Reed and others, 

2002).

The ultimate goal of the USGS and other cooperating 

agencies is to have all surface-water gaging stations in New 

Jersey equipped with “real-time” telemetry equipment.

-- Robert D. Schopp, David A. Stedfast, and Anthony S. 

Navoy

References Cited

Reed, T.J., White, B.T., Centinaro, G.L., Dudek, J.F., Spehar, A.B., Protz, A.R., Shvanda, J.C., Watson, A.F., and 

Holzer, G.K., 2003, Water Resources Data, New Jersey, 

Water Year 2002, Volume 1. Surface-Water Data: U.S. 

Geological Survey Water-Data Report NJ-02-1, 364 p.

Summer, W.M., 1998a, Somerset County Flood Information System: U.S. Geological Survey Fact Sheet 

FS-090-98.

Summer, W.M., 1998b, New Jersey Tide Telemetry System: 

U.S. Geological Survey Fact Sheet FS-091-98.

Summer, W.M., 1998c, Passaic Flood Warning System: 

U.S. Geological Survey Fact Sheet FS-092-98.

Wahl, K.L., Thomas W.O., Jr., and Hirsch, R.M., 1995, The 

stream-gaging program of the U.S. Geological Survey: 

U.S. Geological Survey Circular 1123, 22p.

Related Internet Links

• The home page for the NJDEP is 

http://www.state.nj.us/dep/ .

• The home page for the NJDEP Water Supply Administration, which has information 

related to drought policy and declaration, is 

http://www.state.nj.us/dep/watersupply/ .

• The home page for USGS water-resources information for New Jersey is http://nj.usgs.gov/ .

For additional information contact:

District Chief

U.S. Geological Survey

810 Bear Tavern Road, Suite 206

West Trenton, New Jersey 08628

Telephone number: 609-771-3901

Email: dc_nj@usgs.gov

Figure 6. Example of an actual streamflow hydrograph that can be 

viewed and printed from the “real-time” network web page.