New Jersey Water Science Center
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Summary of Annual Hydrologic Conditions - 1998
Volume 1: Groundwater
More than one-half of New Jersey's drinking water comes from ground water. Concerns about the long-term availability of the ground-water supply and the effects of development on ground-water systems are of major importance. Long-term water-level records are needed to evaluate the effects of climate changes on ground-water systems, to develop a data base that can be used to measure the effects of development, to facilitate the prediction of future ground-water supplies, and to provide data for ground-water-resource management. These data document the general response of the ground-water system to natural climate changes and ground-water withdrawals. The U.S. Geological Survey (USGS) has operated a network of observation wells in New Jersey for the purpose of monitoring water-level changes throughout the State since 1923.
During the 1998 water year, ground-water levels were measured in 190 wells. Previous record low water levels were exceeded in 22 of the 190 wells in the statewide observation-well network during the 1998 water year. Sixteen of the record low water levels were in wells located in the Coastal Plain, and six were in wells located in the northern part of the State. Previous record high water levels were exceeded in 17 network observation wells during the 1998 water year. Sixteen of these wells are located in the Coastal Plain. Observation wells in which water levels exceeded their previous measured extremes (highest or lowest water levels), and for which more than 2 years of data are available, are listed in table 1 (view table in pdf format).
Water levels measured in confined aquifers in the Coastal Plain in water year 1998, together with those measured during previous years, show three general trends. Water levels in observation wells that tap the Atlantic City 800-foot sand of the Kirkwood Formation, the Wenonah-Mount Laurel aquifer, and the Piney Point Formation in the southern part of the Coastal Plain continued to undergo long-term net declines. Water levels in the Potomac-Raritan-Magothy aquifer system, Englishtown aquifer system, and the Wenonah-Mount Laurel aquifer in the northern part of the Coastal Plain (Monmouth, eastern Middlesex, Ocean, and northeastern Burlington Counties), which had been rising since 1990, appear to be leveling off. A 2-year rise in water levels in the Potomac-Raritan-Magothy aquifer system in Burlington, Camden, and Gloucester Counties has reversed a trend of long-term water-level declines.
The Wenonah-Mount Laurel aquifer has shown the greatest water-level fluctuations of any aquifer in the 1998 water year. Five wells tapping this aquifer set record lows, and two set record highs during the year. The greatest long-term water-level decline in an observation well occurred in the New Brooklyn 3 observation well (NJ-WRD well number 07-478), screened in the Wenonah-Mount Laurel aquifer in Camden County. The water level in this well declined more than 65 feet since April 1983. In contrast, one of the greatest increases in water levels occurred in the Doe-Sea Girt observation well (NJ-WRD well number 25-486), screened in the Wenonah-Mount Laurel aquifer in Monmouth County. The water level in this well rose more than 116 feet from September 1988 to September 1998.
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 Potomac-Raritan-Magothy aquifer system 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 Potomac-Raritan-Magothy aquifer system, Englishtown aquifer system, and Wenonah-Mount Laurel aquifer in Critical Area 1. Water levels in eight network observation wells in these aquifers exceeded their previous record highs during the 1998 water year (NJ-WRD well numbers 23-351, 25-316, 25-429, 25-486, 25-635, 25-637, 29-503, and 29-530). 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. Water-level data collected during 1998 indicate, however, that the recovery of water levels in some observation wells in the Potomac-Raritan-Magothy aquifer system, Englishtown aquifer system, and Wenonah-Mount Laurel aquifer in Monmouth and Ocean Counties may be leveling off (NJ-WRD well numbers 25-206, 25-272, 25-353, 25-638, 25-639, 29-19, and 29-85). Water levels in some observation wells in the Potomac-Raritan-Magothy aquifer system in Middlesex County (NJ-WRD well numbers 23-228, 23-229, 23-365, and 23-439) also appear to be leveling off.
In Critical Area 2, the shift in withdrawals away from the deeper, confined aquifers to surface water and ground water in 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 several of these wells have recovered to the levels measured during the 1970's. Since spring 1995, the water level in the Hutton Hill 1 observation well (NJ-WRD well number 07-117) has risen more than 26 feet. This shift in withdrawals to shallower aquifers has caused water levels in the Wenonah-Mount Laurel aquifer to decline in several observation wells, however (NJ-WRD well numbers 5-1155, 5-1387, 15-1126, 33-20).
The effects of climate on daily mean water levels in four observation wells during water year 1998 can be seen in the hydrographs shown in figure 1. Monthly extreme and long-term average water levels are shown for comparison. The Taylor Obs well (NJ-WRD well number 37-202) and the Cranston Farms 15 Obs well (NJ-WRD well number 21-364) are open to fractured-rock aquifers; the Lebanon State Forest 23-D Obs well (NJ-WRD well number 5-689) and the WTMUA Monitoring 1 Obs well (NJ-WRD well number 15-1033) are screened in an unconfined sand and gravel aquifer. These wells are distant from pumping centers.
A dry period during September and October 1997 caused water levels to decline in many observation wells open to unconfined and fractured-rock aquifers throughout the State. Above-average cumulative precipitation from November through June reversed that trend and caused water levels to rise throughout the State. Previous record high water levels were exceeded in six observation wells open to unconfined or fractured-rock aquifers during April, May, and June of the 1998 water year (NJ-WRD well numbers 7-746, 7-747, 29-1059, 29-1060, 21-0365, and 23-351). A prolonged dry period began in July and caused water levels to decline throughout the remainder of the water year. Previous record low water levels were exceeded in six observation wells open to unconfined or fractured-rock aquifers during the 1998 water year (NJ-WRD well numbers 19-251, 21-289, 21-364, 21-365, 27-1191, and 37-359).