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Summary of Annual Hydrologic Conditions - 2002
Volume 2: Groundwater
Ground water is one of the Nation’s most important natural resources. It provides about 40 percent of our Nation’s public water supply. In New Jersey, more than onehalf of the drinking-water supply comes from ground water. Managing the development and use of the ground-water resource so that the supply can be maintained for an indefinite time without causing unacceptable environmental, economic, or social consequences is of paramount importance. The New Jersey Water Supply Plan reported in 1990 that the majority of New Jersey’s water supplies are now developed, and although supplies are sufficient for the foreseeable future in most regions, some regions (mostly those relying heavily on ground water) are presently in deficit. As population and demand for water increase, strategic water management will be required for New Jersey to meet its future water-supply needs.
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. Long-term systematic measurement of water levels in observation wells provides the data needed to evaluate changes in the ground-water resource over time. Records of ground-water levels are used to evaluate the effects of climate changes and water-supply development, to develop ground-water models, and to forecast trends.
New Jersey was in the midst of a 4 -year-drought during the 2002 water year. Statewide precipitation was more than 11 inches below normal from October 2001 through September 2002. The normal precipitation of 47.2 inches per water year is based on precipitation values from 1971 to 2000. As of September 2002, monthly precipitation, as calculated from a spatially weighted average of stations throughout New Jersey, had been below normal 36 of the past 50 months, including 12 of the past 15 months. (Office of the N.J. State Climatologist, Rutgers University, New Jersey, unpub. data accessed March 4, 2002, on the World Wide Web at URL http://climate.rutgers.edu) The period from September 2001 to February 2002 constituted the driest consecutive 6 months recorded since record keeping began in 1895. In November 2001, a drought warning was issued for the Delaware River Basin area. In January, the New Jersey Department of Environmental Protection (NJDEP) expanded the warning to the Northeast and Coastal areas of the State. By March, Governor McGreevey had declared a Water Emergency for all of New Jersey. Statewide water-use restrictions remained in effect throughout the remainder of the 2002 water year. More New Jersey drought information can be found on the NJDEP drought web site at: www.njdrought.org.
The effects of climate on daily mean water levels in six observation wells during water year 2002 can be seen in the hydrographs shown in figure 1. Monthly extreme and long-term average water levels are shown for comparison. The Taylor, Readington School 11, and Cranston Farms 15 observation wells (NJ-WRD well numbers 37-202, 19-270, and 21-364) are open to fractured-rock aquifers; the Morrell 1, Lebanon State Forest 23-D, and Vocational School 2 observation wells (NJ-WRD well numbers 23-104, 5-689, 11-42) tap unconfined sand and gravel aquifers. These wells are all part of the USGS-NJDEP Drought Monitoring Network.
During the 2002 water year, ground-water levels were measured in 184 wells. 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. Previous record low water levels were exceeded in 70 of the 184 wells in the statewide observation-well network during the 2002 water year. Fifty-nine of the record low water levels were in wells located in the Coastal Plain, and 11 were in wells located in the northern part of the State. Twenty-one of these record low levels occurred in wells that tap unconfined aquifers in the southern part of the State, and 11 occurred in stratified drift and fractured rock aquifers in the north. These record low ground-water levels can be directly attributed to the drought conditions that prevailed during the water year. Previous record high water levels were exceeded in one network observation well during the 2002 water year. That well is located in Cape May County.
Water levels measured in confined aquifers in the Coastal Plain in water year 2002, together with those measured during previous years, show three general trends. (1) Water levels in observation wells that tap the Atlantic City 800-foot sand of the Kirkwood Formation, parts of 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. (2) In Water Supply Critical Areas 1 and 2, which were established to halt waterlevel declines, water levels in several observation wells have leveled off after rising for several years. Water levels in some observation wells within these areas declined to record lows during the 2002 water year. These water-level declines could be an indirect effect of the 2002 drought. (3) The use of a desalination plant, which pumps brackish water from the Atlantic City 800-foot sand in Cape May City, has affected two confined aquifers in the Cape May City area. Increased withdrawals from the Atlantic City 800-foot sand resulted in a decline in the water level in the Coast Guard 800 observation well (NJ-WRD well number 9-302). A reduction in withdrawals from the Cohansey sand has resulted in higher water levels over the past 4 years in three observation wells (NJ-WRD well numbers 9-48, 9-49, and 9-150) in the Cape May City area.
The greatest long-term water-level decline in an observation well occurred in the New Brooklyn Park 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 86 feet since December 1962. In contrast, the greatest increase in water levels occurred in the PPWD 6 observation well (NJ-WRD well number 29-530), screened in the Englishtown aquifer system in Ocean County. The water level in this well rose more than 173 feet from August 1989 to April 2001 but declined slightly during 2002.
In 1986, the New Jersey Department of Environmental Protection (NJDEP) designated two “Critical Water-Supply Management Areas” in the New Jersey Coastal Plain. (See figure 2.) This legislation was initiated as a result of concerns about long-term declines in ground-water levels in these areas where ground water is the primary source of water supply. Ground-water withdrawals from specified aquifers in these areas were reduced, and new allocations may be limited. In Critical Area 1, 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, withdrawals from the Potomac-Raritan-Magothy aquifer system are restricted. Pumping restrictions in Critical Area 2 went into effect in 1996.
As a result of the Critical Area legislation, longterm declines in water levels reversed and water levels rose dramatically in the Potomac-Raritan-Magothy aquifer system, Englishtown aquifer system, and Wenonah-Mount Laurel aquifer from 1991 to 1998. This rise in water levels was the result of the reduction in ground-water withdrawals from deep, confined aquifers, an increase in withdrawals from shallower aquifers, and a shift in withdrawals from ground water to surface water levels declined in some observation wells screened in the Potomac-Raritan Magothy aquifer system, the Englishtown aquifer system, and the Wenonah-Mount Laurel aquifer. Record low water levels were recorded in five observation wells in Critical Area 1 (NJ-WRD-well numbers 23-228, 23-229, 25-250, 29-100, 29-140).
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, water levels rose from 1996 through 1999 in many observation wells screened in the Potomac-Raritan-Magothy aquifer system in the Critical Area. During 2002, water levels in 10 observation wells declined to record low levels in and near this Critical Area (NJ-WRD well numbers 05-1391, 15-713, 15-727, 15-728, 15-772, 15-773, 15-774, 33-251, 33-253, 33-348).
The shifting of water withdrawals to shallower confined and unconfined aquifers likely will result in reduced ground-water discharge to streams and wetlands. In addition, the vulnerability of these aquifers to drought and to recharge from undesirable sources likely will increase. The effects of the shift in withdrawals can be seen in water levels in the southern part of the State, where water levels in the Wenonah-Mount Laurel aquifer and the Englishtown aquifer system have declined in seven observation wells (NJ-WRD well numbers 5-259, 5-1387, 07-118, 07-478, 25-250, 29-140, 33-20).
In the northern part of the State, most ground-water withdrawals are from unconfined and fractured rock aquifers. Water levels in 11 observation wells open to stratified drift and fractured rock exceeded their previous record lows during 2002. The water level in the Briarwood school observation well (NJ-WRD well number 27-12) in Morris County declined by 9.4 feet from June 1998 to September 2002 and remained near the lowest recorded levels since monitoring began at this site in 1967.
The U.S.Geological Survey, in cooperation with the NJDEP, established a Drought Monitoring Network in 2001. NJDEP divided New Jersey into six drought regions on the basis of watersheds and water-supply characteristics. Drought indicators (ground-water levels, precipitation, streamflow, and reservoir contents) are monitored continuously in each region. The ground-water-level network, which is one part of the Drought Monitoring Network, was created to provide data to indicate water-level trends in shallow ground-water systems. Satellite telemetry has been added to 15 wells with continuous recorders in order to make the data available in the shortest time possible. An additional seven wells, which previously were measured periodically, were equipped with continuous recorders, and the frequency of measurements was increased at four additional wells. Current data from these wells and other shallow observation wells are compared to monthly statistics of historical data to put the current water levels in context. These data, along with data on precipitation, streamflow, and reservoir contents provide the information needed to determine the hydrologic conditions in each drought region. The USGS Fact Sheet FS-129-02 “Real-Time Ground-Water Level Monitoring in New Jersey” (Jones and others, 2002) describes the ground-water level satellite telemetry segment of the Drought Monitoring Network in more detail. Realtime ground-water-level data can be accessed on the Internet web pages of the USGS at http://water.usgs.gov/nj/nwis/current/?type=gw.