U.S. Geological Survey Fact Sheet FS-129-02 (PDF:524k)
March 2003

Prepared in cooperation with the NEW JERSEY DEPARTMENT OF ENVIRONMENTAL PROTECTION

REAL-TIME GROUND-WATER-LEVEL MONITORING IN NEW JERSEY, 2002

By Walter D. Jones, Anthony S. Navoy, and Daryll A. Pope

Background This network was created to provide data to indicate water-level trends in shallow ground-water systems within the State of New Jersey and to make the data available in the shortest time possible. The wells in this network are located throughout New Jersey (fig. 1) and were chosen because they are completed in shallow aquifers (table 1). The monitoring of shallow aquifers is important because these aquifers are relied on for water supply and irrigation. Additionally, the natural discharge from shallow aquifers provides base flow to streams. Water levels in these aquifers respond relatively quickly to precipitation and dry periods, so the rapid reporting of water-level data is necessary to follow trends. This network, for example, provides data that allow observation of the onset of drought conditions in ground water. Also, the data from this network can be used to estimate the most recent water-level trend in surficial-aquifer wells not outfitted with satellite telemetry.

Figure 1. Location of the 15 observation wells transmitting real-time data and New Jersey Department of Environmental Protection Drought Regions.

Description of the Network Six of the wells are completed in the unconfined parts of the sand and gravel aquifers of the New Jersey Coastal Plain, namely the Kirkwood-Cohansey aquifer system, the Englishtown aquifer system, and the Holly Beach water-bearing zone. Additional information about the aquifers of the Coastal Plain can be found in Zapecza (1989). Eight of the wells are in northern New Jersey and are completed in bedrock formations, namely the Passaic Formation, the Stockton Formation, the Allentown Dolomite, and the Bossardsville Limestone, or in Precambrian Rocks (table 1). Although these wells are deeper, the fractures in the bedrock are connected to the land surface; therefore, water levels respond quickly to precipitation. One well is completed in a stratified-drift aquifer in northern New Jersey. Water levels have been collected at these 15 sites for periods that range from 11 to 80 years. Herman and others (1998) summarize the important aquifers of New Jersey. Well locations were selected to obtain an even distribution of sites throughout New Jersey and to attempt to locate wells within each of the six Drought Regions established by NJDEP (Hoffman, 2001). The areas represented by each Drought Region (fig. 1) are based on large-scale watersheds and similarity of water-supply characteristics, and are defined "so as to match municipal boundaries in order to assist enforcement of mandated water cutbacks during drought emergencies" (Hoffman 2001, p. 1).

Figure 2. Typical equipment at a real-time ground-water-level network site, including the observation well, equipment shelter, data collection platform, solar power panel, and satellite antenna.

Description of Data Collection and Reporting System

Water levels in each well in the network are automatically measured at hourly intervals and stored by a Data Collection Platform (DCP) located on site (fig. 2). Every 4 hours, a burst of data is broadcast from the site to the GOES satellite and relayed to a ground station. The data are retransmitted by the DOMSAT satellite to a USGS ground station, decoded, and automatically posted to the New Jersey District USGS Internet web page for viewing (fig. 3). To ensure the accuracy of the data, each well is visited every 6 to 8 weeks by a USGS technician who makes a manual water-level measurement to check the automated system and to perform maintenance on the equipment.

Figure 3. Schematic drawing showing data transmission from an observation well through satellite telemetry to users on the Internet.

Where to View Data

The ground-water level 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=gw. This page lists each well in the network and indicates the latest water-level measurement.
2. Choose an observation well by clicking on its station number. This leads to a page that summarizes the characteristics of the well, lists the monthly water-level statistics, and shows a hydrograph of the hourly measurements for the latest 7 days (fig. 4).
3. The output format can be modified to produce a table of water-level values or a hydrograph. The timeframe for the table or 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 produce a presentation-quality hydrograph that can be downloaded easily and printed by the viewer.

Figure 4. Example of an actual ground-water hydrograph that can be viewed and printed from the real-time network web page.

The monthly statistics and historical data are provided on the web page to put the current water level in context. The number of years of data used to calculate the statistics is provided first. Statistics on the water levels are provided in terms of the depth to water below land surface. The minimum depth to water for a well actually describes the highest water level measured in that well for the month, and the maximum depth to water describes the lowest water level for the month. The 75 and 25 percent exceedance values are the water levels that were surpassed by 75 and 25 percent, respectively, of all daily mean depths to water during the month. The latest water-level value (obtained from the table or from the line above the hydrograph) can be compared to the monthly statistics.

Because the water-level data are shown automatically, the message "Provisional data subject to revision" is incorporated into the graphs and charts on the web page. 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. For more information about this issue, click on the "Provisional data subject to revision" heading.

For these 15 sites, daily mean depths to water below land surface also are available for the last 550 days (approximately 18 months). A location map, water-quality data, and a database of monthly water levels can be accessed from the home page for each well.

USGS, in cooperation with NJDEP and other agencies, regularly monitors water levels in about 175 other wells in New Jersey. The data from these wells, although not posted on a real-time basis, are available on the web site http://nj.usgs.gov/gw/gw_hydrographs.html. Ground-water data for all wells routinely monitored by USGS, including those of the real-time network, are summarized in an annually published report (for example, Jones, 2002).

Future Sites

The ultimate goal of this joint effor of the USGS and the NJDEP is to establish a network of about 21 wells that will provide an even geographic and hydrologic distribution of real-time monitoring wells in order to characterize shallow-ground-water conditions statewide.

--Walter D. Jones, Anthony S. Navoy, and Daryll A. Pope

References Cited

Herman, G.C., Canace, R.J., Stanford, S.D., Pristas, R.S., Sugarman, P.J., French, M.A., Hoffman, J.L., Serfes, M.S., and Mennel, W.J., 1998, Aquifers of New Jersey: New Jersey Geological Survey, Open-File Map, OFM-24, 1 sheet.

Hoffman, J. L., 2001, Development of New Jersey drought regions: New Jersey Geological Survey Technical Memorandum 01-1, 18 p.

Jones, W. D., 2002, Water Resources Data, New Jersey, Water Year 2001, Volume 2. Ground-Water Data: U. S. Geological Survey Water-Data Report NJ-01-2, 232 p.

Zapecza, O.S., 1989, Hydrogeologic framework of the New Jersey Coastal Plain: U. S. Geological Survey Professional Paper 1404-B, 49 p., 24 pl.

Related Internet Links

• The home page for the NJDEP is <http://www.state.nj.us/dep/>.
• The NJDEP drought information web page is <http://www.njdrought.org/>.
• The home page for the NJDEP New Jersey Geological Survey, which has information on aquifers and related data, is <http://www.state.nj.us/dep/njgs/>.
• 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/>.
• The boundaries of the drought regions, as defined by NJDEP, are available as N.J. Geological Survey Digital Geodata Series data set DGS00-1, "Drought Regions in New Jersey" at <http://www.state.nj.us/dep/njgs/geodata/dgs00-1.htm>.

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