New Jersey Water Science Center
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Summary of Annual Hydrologic Conditions - 2003
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. Currently, more than one-half of New Jersey’s drinking-water is supplied by over 300,000 wells that serve more than 4 million people. (John P. Nawyn, U. S. Geological Survey, written commun., 2004) As population and demand for water increase, strategic water management will be required for New Jersey to meet its future water-supply needs. 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 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. Ground-water levels are currently measured in 185 wells: 114 wells are equipped for continuous water-level monitoring, 16 wells are equipped to measure maximum and minimum water levels between site visits, and 55 wells are measured manually from two to six times per year.
The USGS, in cooperation with the New Jersey Department of Environmental Protection (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 vailable 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. During 2003, the Network was expanded hydrologically and areally with the addition of six new wells equipped with continuous recorders. 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. Ground-water data for New Jersey can be accessed on the Internet web pages of the USGS at http://waterdata.usgs.gov/nj/nwis/gw. Real- time data from a National Ground Water Climate Response Network of about 150 wells, including the 15 wells in New Jersey, can be accessed at http://groundwaterwatch.usgs.gov/.
During the 2003 water year, ground-water levels were measured in 185 wells. 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 23 of the 185 wells in the statewide observation-well network during the 2003 water year. Twenty-one of the record low water levels were in wells located in the Coastal Plain, and two were in wells located in the northern part of the State. Thirteen of these record low levels occurred in wells that tap unconfined aquifers in the southern part of the State, and two occurred in stratified drift and fractured rock aquifers in the north. These record low ground-water levels can be attributed directly to the drought conditions that prevailed during the early part of the water year. Previous record high water levels were exceeded in 16 network observation wells during the 2003 water year.
At the beginning of water year 2003, New Jersey was returning to normal conditions after experiencing 4 years of drought conditions. During droughts, it takes longer for the deficiencies of precipitation to show up in the ground-water system than in the surface-water system. This time lag causes ground-water levels to be the last to show the effects of the onset of drought and the last to return to normal after a drought ends. By December 2002, most ground-water levels had returned to normal seasonal levels. On January 8, 2003, Governor McGreevey lifted New Jersey’s statewide Water Emergency which had been in effect for the previous 10 months. The drought years were followed by the fifth wettest calendar year since 1895. The average statewide precipitation totaled 57.5 inches, more than 10 inches greater than the normal annual mean. Annual mean precipitation for New Jersey is 47.2 inches per water year based on precipitation during 1971-2000. (Office of the N.J. State Climatologist, Rutgers University, New Jersey, unpub. data, accessed March 4, 2003, on the World Wide Web at URL http://climate.rutgers.edu) More New Jersey drought information can be found on the NJDEP drought web site at: www.njdrought.org.
The effects of the wet year on daily mean water levels in six observation wells during water year 2003 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 hydrographs show the recovery of water levels in these wells from the drought. 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 and show a somewhat slower recovery from the drought than wells that tap the fractured rock aquifers. These wells are all part of the USGS-NJDEP Drought Monitoring Network.
Water levels in most wells that tap unconfined aquifers in the Coastal Plain show the effects of recent climate patterns. The low water levels in 1995, 1998, 1999, 2001, and 2002 are the result of dry years, and the high water levels in 2003 are the result of the recent wet year. Water levels in these wells, in general, are similar regardless of which aquifer the wells are completed in.
For wells that tap fractured rock aquifers and stratified drift deposits in northern New Jersey, trends in water levels are not as similar as those for wells that tap the Coastal Plain unconfined aquifers. The effects of recent droughts can be seen in many wells that tap various aquifers; however, some wells do not show the effects of drought as clearly and may be influenced more by nearby withdrawals or local confinement.
Water levels in the confined aquifers in the Coastal Plain of New Jersey have been reacting to changes in withdrawals for the past 10 years. In 1986, 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 concern about long-term declines in ground-water levels in these areas where ground water is the primary source of water supply. Groundwater 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. In Critical Area 2, withdrawals from the Potomac- Raritan-Magothy aquifer system have been restricted since 1996.
In Critical Area 1, 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 sources. 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, beginning in 1996 water levels rose in many observation wells screened in the Potomac-Raritan-Magothy aquifer system in Critical Area 2.
Water levels measured in confined aquifers in the Coastal Plain in water year 2003, together with those measured during previous years, show the effects of the Critical Area cutbacks -- recovering water levels in some aquifers in some areas. Declines in water levels in some parts of the shallower confined and unconfined aquifers also have occurred recently. Changes in water levels for each of the confined aquifers in the Coastal Plain are summarized in the following paragraphs. Water levels in the confined Cohansey aquifer in Cape May Couny have been relatively unchanged in wells in the northern part of the county. In wells in the southern part of the county (9-48, 9-49, and 9-150), water levels have recovered about 5 feet since 1999 as a result of changes in withdrawals related to the desalinization plant in Cape May City, which has provided water for public supply since 1998.
Water levels in the Atlantic City 800-foot sand have been affected by withdrawals for the desalination plant. Water levels in the Coast Guard 800 observation well (NJ-WRD well number 9- 302) have declined more than 10 feet since 1998, and water levels in two wells located north of the desalinization plant (9-306 and 9-337) have declined 2 to 4 feet since 1998. In Atlantic County, water levels have been relatively stable over the past 5 years (1-37, 1-180, 1-578, 1-702 and 1-703).
Water levels in the Piney Point aquifer throughout much of the southern part of the State continue to decline. Declines of 3 to 10 feet have occurred over the past 10 years in several wells completed in the Piney Point aquifer (1-834, 1-1219, 11-44 and 29-1210); however, water levels in the aquifer in parts of Ocean and Burlington Counties have been relatively stable (5-407, 5-676, and 29-425). Water levels in the Vincentown aquifer have remained stable over the past 10 years except for periods of drought when levels dropped 1 to 3 feet (5-1250, 25- 636 and 29-139).
Water levels in the Wenonah-Mount Laurel aquifer in parts of Burlington, Camden, Gloucester, and Salem Counties had been declining over the last several years but leveled off during 2002-03 (5-1155, 5-1387, 7-118, 7- 478 and 33-20). The greatest long-term water-level decline in a confined aquifer observation well has occurred in the New Brooklyn Park 3 observation well (07-478), which is screened in the Wenonah-Mount Laurel aquifer in Camden County. The water level in this well declined more than 86 feet since December 1962 but has recently leveled off and showed slight recovery in 2003. Water levels in the northern part of the aquifer leveled off in the late 1990’s after recovering as a result of Critical Area 1 withdrawal cutbacks (25-353, 25-486, and 25-637).
Water levels in observation wells that tap the Englishtown aquifer system recovered and have leveled off in the northern part of the aquifer as a result of Critical Area 1 withdrawal cutbacks (25-486, 29-503 and 29-530). Water-levels in several wells in southern Monmouth County, however, have shown slight declines over the past 2 years (25-429 and 25-638). Water levels in the Toms River 2 Obs well (29-534) in central Ocean County have been rising steadily for the past 10 years. Recent declines in water levels occurred at two wells in Burlington County (5- 259 and 5-1390) because of increased withdrawals from the aquifer in that area.
Water levels in the Potomac-Raritan-Magothy aquifer system have been affected by withdrawal cutbacks in both Critical Areas. Water levels recovered through the late 1990’s in the northern part of the aquifer system as a result of the decreased withdrawals in Critical Area 1 but have declined slightly in recent years at several wells (25- 272, 25-635, 25-639, 29-19, 29-85). In the vicinity of Critical area 2 (Burlington, Camden, and Gloucester Counties), water levels began rising in 1996 and either are continuing to rise slightly or have leveled off in recent years.