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Long Island-New Jersey (LINJ) Coastal Drainages Study

Back to LINJ publication list Back to LINJ publication list.

Fact Sheet FS-012-94, by Paul Stackelberg and Mark Ayers

In 1991, the U.S. Geological Survey (USGS) began its National Water-Quality Assessment (NAWQA ) program to (1) document the quality of a large, representative part of the Nation's water resources; (2) define water-quality trends; and (3) identify major factors that affect water quality. In addressing these goals, the program will produce information that will be useful to water policy makers and managers at National, State, and local levels.

Studies of 60 hydrologic systems that include parts of most major river and aquifer systems form the building blocks of the NAWQA program. Study units range in size from about 1,000 mi ² (square miles) to more than 60,000 mi² and represent 60 to 70 percent of the Nation's water use and population served by public water supply. The first 20 studies were begun in 1991; 20 more were begun in 1994, and the remaining 20 are to begin in 1997.


Map of the study area

The Long Island-New Jersey Coastal Drainages NAWQA study, one of 20 begun in 1994, will be coordinated from the USGS office in West Trenton, N.J. The study unit covers more than 6,000 mi² in New York and New Jersey (fig. 1). It includes all of Long Island, Staten Island, and the coastal drainages of New Jersey, excluding the Delaware River Basin. In 1990, the population of study unit was more than 10 million, concentrated mostly on Long Island and in northeastern New Jersey. In 1973, 28 percent of the study unit was developed for residential and urban use, 7 percent was used for industrial and commercial purposes, 14 percent was used for agriculture, 34 percent was forested, 9 percent was wetland, and 8 percent was classified as either surface-water bodies or miscellaneous land use.

About 65 percent of the study unit lies within the Coastal Plain Physiographic Province (fig. 1), 24 percent is within the Piedmont Physiographic Province and 11 percent is within the New England Physiographic Province. The northern half of the Piedmont and New England Physiographic Provinces was ice-covered during the last glacial advance. Surficial deposits on Long Island are glacial in origin with morainal deposits to the north and outwash deposits to the south.

Average annual precipitation ranges from 42 inches in the Coastal Plain to 52 inches in north-central New Jersey, and annual snowfall ranges from 13 inches in southeastern New Jersey to more than 50 inches in north-central New Jersey. Generally, precipitation is evenly distributed throughout the year. Annual average temperature ranges from 56 degrees Fahrenheit in southern New Jersey to 50 degrees Fahrenheit in southern New York.

Hydrogeologic characteristics of provinces north of the Fall Line differ greatly from those of the Coastal Plain (fig. 1). The New England Physiographic Province is underlain by igneous and metamorphic rocks that contain water-bearing weathered and fractured zones typically within 300 feet of the land surface. Aquifers in the Newark Group, which is present in the Piedmont province, consist of shale and sandstone that contain water in weathered joint and fracture systems within 200 to 300 feet of the land surface. The valleys in the glaciated northern half of these two provinces are underlain by stratified drift and glacial till. The stratified drift, composed of poorly sorted sand and gravel with interbedded silt, silty sand, and clay, forms valley-fill aquifers. These aquifers are generally 30 to 40 feet thick, but as much as 300 feet thick in some valleys.

The Coastal Plain (fig. 1) is underlain by a wedge of unconsolidated sediments that form permeable units (aquifers) of sand and gravel interbedded with poorly permeable (confining) units of silt and clay. These interbedded, unconsolidated sediments differ in thickness and areal extent, but generally dip and thicken southeastward to a maximum thickness of about 6,500 feet at the coast. The Coastal Plain aquifers in New Jersey are the Kirkwood-Cohansey aquifer system, the Atlantic City 800-foot sand, the Wenonah-Mount Laurel aquifer, the Englishtown aquifer system, and the Potomac-Raritan-Magothy aquifer system. The Kirkwood-Cohansey aquifer system is largely unconfined, but the other aquifers are confined except where they crop out.

Glacial deposits overlie most of Long Island and form the unconfined (water-table) aquifer and local water-bearing deposits of lesser extent, including the Jameco aquifer. These systems are underlain by the Magothy and Lloyd aquifers, which are generally confined.

The Coastal Plain has relatively flat, thick, sandy soils that allow rapid infiltration of rainfall, in fact, more than 90 percent of streamflow is derived from groundwater discharge. The New England and Piedmont Physiographic Provinces have relatively steep, thin, clayey soils, which produce runoff more rapidly than Coastal Plain soils. Much of western Long Island and northeastern New Jersey consists of urban areas in which psved impesrmisble surfaces yield runoff rapidly.

The principal river systems within the study unit are the Hackensack, Passaic, Raritan, Toms, Mullica, and Great Egg Harbor Rivers in New Jersey. Many other smaller rivers and streams drain the Coastal Plain, including the Peconic River on Long Island.

The Hackensack River drains 202 mi², mostly within the Piedmont Physiographic Province. The basin is heavily urbanized. Downstream reaches of the river receive urban runoff and point-source discharges. The basin contains three major water-supply reservoirs. The Passaic River (950 mi²-drainage) starts in the mostly forested New England Physiographic Province and flows through the Piedmont Physiographic Province, which is densely populated and highly industrialized. Many upstream reaches are relatively pristine, whereas downstream reaches receive urban runoff and point-source discharges. The Passaic basin contains seven major water-supply reservoirs. The Raritan River drains 1,105 mi² across the New England, Piedmont, and Coastal Plain Physiographic Provinces. Upstream reaches of the river receive agricultural runoff, whereas downstream reaches receive urban runoff and point-source discharges. The basin contains two major water-supply reservoirs and receives a significant diversion, as much as 100 Mgal/d (million gallons per day), from the Delaware River for water supply. Water-supply facilities in all three river systems are inter-connected and transfer of water is common.

Rivers that drain the Coastal Plain of New Jersey include the Toms (192 mi²), Mullica (569 mi²), and Great Egg Harbor (347 mi²) Rivers. Their combined drainage area includes most of the Pinelands, an area of sandy lowlands covered with scrub pine and oak. The drainage areas of Long Island rivers and streams are largely residential with high population density and some commercial land use. Water in much of the New Jersey Pinelands is of pristine quality, whereas water in other parts of the New Jersey Coastal Plain and in much of Long Island have been affected by agricultural and lawn chemicals, septic-tank effluent, and synthetic organic compounds from domestic and commercial use.

Major water uses in the study unit include domestic, commercial, industrial, mining, power production, and crop irrigation. In 1985, 73 percent of the 2,230 Mgal/d of freshwater used in all of New Jersey was surface water and 27 percent was groundwater. Of the 961 Mgal/d used for public supply in 1985, about 57 percent was surface water and 43 percent was groundwater. However, about 77 percent of the public supply north of the Fall Line was from surface-water sources, whereas, only 29 percent south of the Fall Line was from surface-water sources. Total domestic and commercial use in New Jersey, including deliveries from public supply, was 804 Mgal/d serving about 7.5 million people in the State. In 1985, 469 Mgal/d was withdrawn from Long Island's aquifers to serve nearly 3 million people living there.


Coordination among the USGS, water-management agencies, and other related scientific organizations is essential to the NAWQA program. A study-unit liaison committee consisting of representatives from Federal, State, and local agencies, universities, and the private sector who have water-resources responsibilities has been organized for this study. Specific activities of the liaison committee include definition of major water-quality issues, sharing of water-quality and other data, assisting in the design of the study, and review of planning activities, findings, and interpretations, including reports. The Long Island-New Jersey Coastal Drainages study-unit liaison committee held its first meeting on May 13, 1994.


The committee identified two broad water-quality issues that are priorities in the study unit: (1) the effects of point discharges and nonpoint-source runoff to streams and, ultimately, Barnegat Bay and the New York/New Jersey Harbor Complex and; and (2) the vulnerability of public and domestic water supplies to contamination from urban, industrial, and agricultural land use. Nutrients and toxic substances are of great concern as part of these issues, primarily because the current scientific understanding of processes governing the presence, distribution, fate, and biological effects of these contaminants is limited.

The committee specifically suggested that due to the wealth of available data the groundwater component of the study should focus on analysis of existing data and on collecting data on processes affecting the source, transport, and fate of selected constituents within aquifer systems in the study unit. Major groundwater needs identified include developing a better understanding of (1) relations between shallow-groundwater quality and land-use patterns, (2) spatial and temporal trends in groundwater quality, (3) vulnerability of wells to contamination, (4) age-dating of groundwater, and (5) groundwater/surface-water interactions. Major surface-water needs identified include developing a better understanding of the effects of and processes associated with (1) toxic materials (such as trace elements and synthetic organic compounds), (2) nutrients, (3) sediments (particularly those related to the transport and fate of toxic materials and nutrients), (4) stormwater quality, and (5) interbasin transfers of water. A suggested focus was to relate sources and loads of nutrients and toxic materials to sediment quality, bioaccumulation in tissues, aquatic community effects, land use, and other factors.

The large population, extensive urban and industrial development, and, in some areas, agricultural activities, are the main causes of water-quality problems in the study unit. The NAWQA program can provide additional data and understanding to facilitate solution of these problems. Initial efforts will focus on identifying gaps in the data and developing a comprehensive understanding of the issues from an already rich water-quality data base.

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