FS-011-02: REAL-TIME GROUND-WATER-LEVEL MONITORING IN NEW JERSEY

FS-011-02: REAL-TIME GROUND-WATER-LEVEL MONITORING IN NEW JERSEY

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

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

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A network of seven observation wells that transmit ground-water-level data on a real-time basis through satellite telemetry is operating (started May 2001) in New Jersey through a cooperative effort of the U.S. Geological Survey (USGS) and the New Jersey Department of Environmental Protection (NJDEP). The water-level data from these observation wells are transmitted every 4 hours and then are immediately posted for viewing on the Internet. This fact sheet describes the rationale for real-time monitoring of ground-water levels, the design of the network, and the equipment used to measure water levels and transmit the data to the Internet. Instructions for viewing the data are included.

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.

Figure1. Location of the seven network observation wells transmitting real-time data and New Jersey Environmental Protection Drought Regions.

Table 1. Characteristics of the seven wells in the real-time ground-water level network
[ID, identification; a.s., aquifer system]

Well name	County	USGS Site ID number	Start of record	Aquifer or formation	Well depth (ft)
Lebanon SF 23-D	Burlington	395150074284201	1955	Kirkwood-Cohansey a.s.	33
Vocational School 2	Cumberland	392731075092401	1972	Kirkwood-Cohansey a.s.	47
Readington School 11	Hunterdon	403517074452501	1990	Passaic Formation	101
Cranston Farms 15	Mercer	401804074432601	1990	Stockton Formation	200
Morrell 1	Middlesex	402143074185201	1923	Englishtown a.s.	11
Green Pond 5	Morris	410207074270001	1981	Stratified Drift	120
Taylor Obs	Sussex	410914074540401	1988	Bossardsville Limestone	95

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Description of the Network Three 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 and the Englishtown aquifer system. Further information about the aquifers of the Coastal Plain can be found in Zapecza (1989). Three of the wells are completed in bedrock in northern New Jersey, namely the Passaic Formation, Stockton Formation, and the Bossardsville Limestone (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 in northern New Jersey. Water levels have been collected at these seven sites for periods that range from 11 to 78 years. Herman and others (1998) summarize the significant 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). No wells in the network are currently (2001) located in the Coastal North Region, but the Morrell 1 well in the Central Region is close to the boundary with the Coastal North Region.

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

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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.