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Summary of Annual Hydrologic Conditions - 2004
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). New Jersey’s population is expected to grow by almost a million people over the next 20 years (Garden State Environews, 2004). As demand for water increases, 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 since 1923 for the purpose of monitoring ground water-level changes throughout the State. 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.
During 2004, ground-water levels were measured in 196 wells: 125 wells were equipped for continuous water-level monitoring, 16 wells were equipped to measure maximum and minimum water levels between site visits, and 55 wells were measured manually from two to six times per year. Data for 12 new wells are included in this report. Five wells in Cumberland County are monitored continuously to provide data on spatial variations in recharge as it relates to contaminant loading. A study of ground water/surface water interaction in the pinelands region of southern New Jersey has begun and continuous water-level data from seven wells in the pinelands region are included in this report.
The USGS, in cooperation with the New Jersey Department of Environmental Protection (NJDEP), established
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 World Wide Web pages of the USGS at http://waterdata.usgs.gov/nj/nwis/gw. Real- time data from a National Ground Water Climate Response Network, which includes the 16 real-time equipped wells in New Jersey, can be accessed at http://groundwaterwatch.usgs.gov/.
During the 2004 water year, ground-water levels were measured in 196 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 7 of the 196 wells in the statewide observation-well network during the 2004 water year. All of the record low water levels were in wells located in the Coastal Plain. These record low levels are the result of increasing withdrawals from wells that tap two confined aquifers-- the Atlantic City 800-foot sand of the Kirkwood Formation and the Piney Point aquifer in the southern part of the State. Previous record high water levels were exceeded in 10 network observation wells during the 2004 water year.
New Jersey’s average annual precipitation ranges from about 40 inches along the southeastern coast to 51 inches in the north-central part of the State. Statewide, the annual mean precipitation 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 Feb. 14, 2004, on the World Wide Web at URL http://climate.rutgers.edu). The above average ground-water levels measured during 2003-04 water years in wells completed in unconfined and fractured rock aquifers are directly related to the annual precipitation, which was more than 13 inches above average during the period.
The effects of climate on daily mean water levels in six observation wells during water year 2004 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.
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 and 2004 are the result of the recent wet years. 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. During water year 2004, water levels in many observation wells tapping stratified drift aquifers rose to their highest level in the last 10 years. Most notable was the water level in the Briarwood School well (27-12) where the level rose more than 13 feet.
Water levels in the confined aquifers in the Coastal Plain of New Jersey have been reacting to changes in withdrawals over the past 10 years. In 1986, NJDEP designated two “Critical Water-Supply Management Areas” in the New Jersey Coastal Plain. (See figure 2.) This designation 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. 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. 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
Water levels measured in confined aquifers in the Coastal Plain in water year 2004, together with those measured during previous years, show the effects of the Critical Area cutbacks and changes in ground-water withdrawal
Water levels in the confined Cohansey aquifer in Cape May County have been relatively constant 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 a reduction in withdrawals related to the use of a desalinization
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 (1-180, 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, and 29-1210); water levels in 3 wells in Cumberland County declined from 2 to 14 feet from April to September 2004 (11-44, 11-96 and 11-163). Water levels in the aquifer in parts of Ocean and Burlington
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 2002-04 (5-1155, 5-1387,and 7-478). 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 from December 1962 to December 2001 but has recently leveled off and showed slight recovery since 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 (29-138, 29-503 and 29-530). Water-levels in several wells in southern Monmouth County, however, have shown slight declines over the past 3 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. Water levels in the Englishtown aquifer system have been recovering since 2003 at two wells in Burlington County (5-259 and 5-1390).
Water levels in the Potomac-Raritan-Magothy aquifer system have been affected by cutbacks in withdrawals