During the 1997 water year, ground-water levels were measured in 188 wells. Previous record low water levels were exceeded in 18 of the 188 wells in the statewide observation-well network during the 1997 water year. Fifteen of the record low water levels were in wells located in the Coastal Plain, and three were in wells located in the northern part of the State. Previous record high water levels were exceeded in 26 network observation wells during the 1997 water year. Six of these wells are screened in the Englishtown aquifer system and the Wenonah-Mount Laurel aquifer in the northern part of the Coastal Plain in Monmouth and Ocean Counties, and seven are screened in the Potomac-Raritan-Magothy aquifer system in the southern part of the Coastal Plain in Gloucester County.
Water-level measurements in confined aquifers in the Coastal Plain in water year 1997, together with those made during previous years, show three general trends. Water levels in observation wells that tap some of the heavily pumped confined aquifers in the southern part of the Coastal Plain continued to undergo long-term net declines; water levels in some of the confined aquifers in the northern part of the Coastal Plain (Monmouth, eastern Middlesex, Ocean, and northeastern Burlington Counties) continued to rise; and long-term water-level declines in the Potomac-Raritan-Magothy aquifer system in Burlington, Camden, and Gloucester Counties began to abate.
The greatest long-term water-level decline in an observation well has been measured in the New Brooklyn Park 3 observation well (NJ-WRD well number 7-478), screened in the Wenonah-Mount Laurel aquifer in Camden County. The water level in this well has declined more than 60 feet since April 1983. Water levels in other observation wells in the Wenonah-Mount Laurel aquifer in the southern Coastal Plain (NJ-WRD well numbers 5-1155 and 33-20) also declined.
Previous record low water levels were exceeded in six observation wells screened in the Atlantic City 800-foot sand (Atlantic and Cape May Counties) in the 1997 water year (NJ-WRD well numbers 1-37, 1-578, 1-702, 9-302, 9-306, and 9-337). Water levels also declined in two other wells screened in the Atlantic City 800-foot sand in Atlantic County (NJ-WRD well numbers 1-180 and 1-703).
Water levels in wells screened in the Piney Point aquifer in Cumberland County (NJ-WRD well numbers 11-44, 11-96, and 11-163) and one well in Atlantic County (NJ-WRD well number 1-834) also continued to decline. Water levels in the remaining three network observation wells screened in the Piney Point aquifer in Ocean County were relatively unchanged.
In 1986, the New Jersey Department of Environmental Protection (NJDEP) designated two "Critical Water-Supply Management Areas" in the New Jersey Coastal Plain. Ground-water withdrawals from specified aquifers in these areas were reduced, and new allocations may be limited. In Critical Area 1, which consists of Middlesex, Monmouth, and Ocean Counties, withdrawals from the Wenonah-Mount Laurel aquifer, Englishtown aquifer system, and Upper and Middle Potomac-Raritan-Magothy aquifers are restricted. Pumpage restrictions in this area began in 1989. In Critical Area 2, which consists of Camden, most of Burlington and Gloucester, and parts of Atlantic, Cumberland, Ocean, Monmouth, and Salem Counties, withdrawals from the Upper, Middle, and Lower Potomac-Raritan-Magothy aquifers are restricted. Pumping restrictions here went into effect in 1996.
Early in the 1991 water year, long-term declines in water levels reversed in several observation wells screened in the deep, confined aquifers (Potomac-Raritan-Magothy aquifer system, Englishtown aquifer system, and Wenonah-Mount Laurel aquifer) in southern Monmouth and northern Ocean Counties (Critical Area 1). Water levels in network observation wells in the Englishtown aquifer system, and the Wenonah-Mount Laurel aquifer (NJ-WRD well numbers 25-353, 25-429, 25-486, 25-637, 25-638, 29-138, 29-503, and 29-534) continued to rise during the 1997 water year. This rise in water levels is the result of a reduction in ground-water withdrawals and an increase in surface-water withdrawals for public water supply and a shift in withdrawals from deep, confined aquifers to shallower aquifers. The recovery of water levels in some observation wells in the Potomac-Raritan-Magothy aquifer system in Monmouth and Ocean Counties may be leveling off (NJ-WRD well numbers 25-206, 25-272, 25-316, 25-635, 25-639, 29-19, and 29-85). Water levels in some observation wells in these aquifers in Middlesex County (NJ-WRD well numbers 23-229, 23-365, and 23-439), however, may still be recovering.
In Critical Area 2, the shift to withdrawals of surface water and of ground water from shallower confined and unconfined aquifers began in 1996. As a result, the long-term water-level declines have ceased in observation wells screened in the Potomac-Raritan-Magothy aquifer system (NJ-WRD well numbers 5-258, 5-261, 5-262, 5-440, 5-645, 7-117, 7-412, 7-413, 7-476, 7-477, 15-671, 15-741, 15-742, 33-251, and 33-253). Water levels in seven observation wells screened in the Potomac-Raritan-Magothy aquifer system in Gloucester County exceeded their previous highs of record. The water level in the Deptford Deep observation well (NJ-WRD well number 15-671) exceeded the previous highest level by more than 10 feet.
The effects of climate on daily mean water levels in four observation wells during water year 1997 can be seen in the hydrographs shown in figure 1. Monthly extreme and long-term-average water levels are shown for comparison. The Taylor well (NJ-WRD well number 37-202) and the Cranston Farms 15 well (NJ-WRD well number 21-364) are open to fractured-rock aquifers; the Lebanon State Forest 23-D well (NJ-WRD well number 5-689) and the WTMUA Monitoring 1 well (NJ-WRD well number 15-1033) are screened in an unconfined sand and gravel aquifer. These wells are distant from pumping centers.
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EXPLANATION
UNSHADED AREA-- Indicates range between highest
and lowest monthly water level, prior to the
current year
DASHED LINE-- Indicates mean of monthly mean
water levels, prior to the current year
SOLID LINE-- Indicates daily mean water level
for the current year, break in line indicates
missing data.
LOCATION OF WELL (on map)-- Number corresponds
to hydrograph number show below
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    Figure 1. Ground-water levels at key observation well in New Jersey during water year 1997.
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In this assessment, water was collected from 22 shallow wells in Watershed Management Area 19--18 wells in Burlington County and 4 wells in Camden County (fig. 2). The depth of the wells that were sampled ranged from 10 to 85 feet below land surface.
 Figure 2. Locations of 22 wells sampled in water year 1997 as part of the U.S. Geological Survey-New Jersey Department of Environmental Protection cooperative ambient ground-water quality network showing wells in which quality of water is or may be affected by quality of water in nearby streams. |
Three factors that affect the quality of shallow ground water in an unconfined aquifer are (1) mixing with water from losing stream reaches, (2) the geologic material through which the ground water flows, and (3) land use. Three of the 22 wells sampled (fig.2) are located near losing stream reaches; water in these wells is most likely to be affected by the quality of water in the nearby stream. Three additional wells are located near stream reaches that appear to be losing water to the unconfined aquifer; water in these wells also may be affected by streamwater quality. The remaining 16 wells are not located near losing stream reaches. The 22 wells sampled are screened in seven different hydrogeologic units, which are composed of different geologic materials, and are located in urban, agricultural, and undeveloped land-use areas (based on New Jersey Department of Environmental Protection digital data, 1: 24,000 scale, 1986) (table 1).
Table 1. Hydrogeologic unit, land use, and results of analyses for selected waterquality constituents in samples from 22 wells sampled as part of U.S. GeologicalSurvey -N.J. Department of Environmental Protection (cooperative) Ambient Ground-Water-Quality Network, water year 1997The major-ion chemistry of the water from the 22 wells is highly variable (fig.3). Concentrations of dissolved oxygen in 5 of the 19 wells in which this constituent was measured were less than or equal to 1.0 milligrams per liter; this ground water is considered to be anoxic. Anoxic water was found in wells in agricultural and urban land-use areas, but not in wells in undeveloped land-use areas (table 1).
[mg/L, milligrams per liter; --, no data available;<,less than]
------------------------------------------------------------------------------------------------------------------------------------------------- NJ- Hydrogeologic unit Predominant land Water type Dis- Volatile organic compounds Nitrogen, WRD use(s) (dominant cation and solved measured in concentrations greater NO2+ Well anion) oxygen, than the laboratory reporting limit NO3, Number mg/L mg/L ------------------------------------------------------------------------------------------------------------------------------------------------- 05-0782 Middle Potomac-Raritan-Magothy Urban Calcium-magnesium-sul 3.0 Not analyzed for VOC's 3.7 aquifer fate 05-0835 Kirkwood-Cohansey aquifer system Undeveloped Sodium-sulfate 9.9 Chloroform 0.07 05-0836 Kirkwood-Cohansey aquifer system Undeveloped Sodium-sulfate 8.7 Chloroform 0.05 05-1092 Kirkwood-Cohansey aquifer system Undeveloped Sodium-chloride 6.2 Chloroform, methyl tert-butyl ether 1.5 05-1349 Vincentown Formation Agricultural Sodium-calcium -chloride 7.4 None 4.4 05-1392 Middle Potomac-Raritan-Magothy Urban Magnesium-chloride 8.9 None 0.77 aquifer 05-1393 Wenonah-Mount Laurel aquifer Urban-undevel Magnesium-sulfate -- None 0.12 oped 05-1394 Wenonah-Mount Laurel aquifer Urban-undevel Calcium-carbonate -- None 0.05 oped 05-1395 Kirkwood-Cohansey aquifer system Undeveloped- Sodium-chloride 7.6 Not analyzed for VOC's 0.18 urban 05-1396 Wenonah-Mount Laurel aquifer Agricultural Calcium-sulfate 8.8 None 9.9 05-1397 Wenonah-Mount Laurel aquifer Agricultural Iron-calcium-sulfate 0.2 None 0.18 05-1398 Englishtown aquifer system Urban Sodium-chloride 0.3 None 1.7 05-1399 Englishtown aquifer system Urban Calcium-sulfate 3.0 Methyl tert-butyl ether 0.07 05-1400 Wenonah-Mount Laurel aquifer Urban Sodium-chloride 4.7 Not analyzed for VOC's 0.98 05-1401 Wenonah-Mount Laurel aquifer Urban Calcium-sulfate 2.7 Not analyzed for VOC's <0.05 05-1402 Kirkwood-Cohansey aquifer system Agricultural Sodium-chloride 0.5 Methyl tert-butyl ether <0.05 05-1403 Hornerstown Sand Agricultural Calcium-chloride 8.8 None 0.9 05-1404 Kirkwood-Cohansey aquifer system Agricultural Magnesium-sodium-chlo 7.5 Chloroform, methyl tert-butyl ether 7.9 ride 07-0871 Upper Potomac-Raritan-Magothy Urban Sodium-chloride 0.4 Not analyzed for VOC's 6.4 aquifer 07-0872 Upper Potomac-Raritan-Magothy Urban Calcium-bicarbonate 4.4 Trichlorofluoromethane, 1,2-dichloro 0.23 aquifer propane 07-0873 Kirkwood-Cohansey aquifer system Urban Sodium-chloride -- None 2.9 07-0874 Kirkwood-Cohansey aquifer system Urban Calcium-bicarbonate 1.0 None 1.0 -------------------------------------------------------------------------------------------------------------------------------------------------
 Figure 3. Trilinear diagram showing the distribution of major ions in ground water from 22 wells sampled in water year 1997 as part of the U.S. Geological Survey-New Jersey Department of Environmental Protection cooperative ambient ground-water quality network. |
Nitrate-plus-nitrite nitrogen concentrations in water from the 22 wells ranged from less than 0.05, the laboratory reporting limit, to 9.9 milligrams per liter (table 1). In general, concentrations of nitrate-plus-nitrite nitrogen were lower in wells in undeveloped land-use areas than in wells in agricultural or urban land-use areas.
Ground water from 17 wells was analyzed for volatile organic compounds (table 1). Water in 7 of the 17 wells contained four different volatile organic compounds in concentrations greater than or equal to the laboratory reporting limit of 0.2 micrograms per liter. Volatile organic compounds were reported in sample water from wells in all three land-use categories. The most frequently reported volatile organic compounds were chloroform and methyl tert-butyl ether; each compound was detected in water samples from four wells. Two samples contained both chloroform and methyl tert-butyl ether, and one contained both trichloroflouromethane and 1,2-dichloropropane. The highest concentrations of chloroform and methyl tert-butyl ether were 1.0 and 5.4 micrograms per liter, respectively, and were not found in water from the same well.
In the 1940's, the USGS established a saltwater-monitoring network in the Coastal Plain of New Jersey to document the movement of saltwater into the freshwater aquifers. The USGS collects and analyzes water samples from USGS and NJDEP observation wells and selected domestic and agricultural-supply wells. These chloride measurements are augmented by chloride-concentration data reported to the NJDEP by owners of public- and industrial-supply wells. During the 1997 water year, the USGS sampled water from 21 wells in seven counties. Chloride concentrations in these samples were supplemented by more than 6,000 additional values that were reported by hundreds of public- and industrial-supply well owners and are stored in NJDEP files.
During the 1997 water year, saltwater intrusion continued in many communities along Raritan Bay, the Atlantic Coast, the Delaware Bay, and the lower Delaware River, and in central Gloucester County. Water in a recently drilled well (NJ-WRD well number 25-771) screened in the Englishtown aquifer system in Sea Bright Borough, Monmouth County, was sampled and analyzed this year. The chloride concentration of the water from this well (15,000 mg/L) is similar to that of seawater. Saltwater was not detected in this aquifer system anywhere else in the Coastal Plain. Additional monitoring is needed to determine whether this high chloride concentration is static or is increasing over time.
New Jersey District Chief
U.S. Geological Survey
810 Bear Tavern Road, Suite 206
West Trenton, NJ 08628
Phone: (609)-771-3901