New Jersey Ambient Surface-Water-Quality Monitoring Network

Science Center Objects

The USGS New Jersey Water Science Center, in cooperation with the NJ Department of Environmental Protection (NJDEP), New Jersey Water Supply Authority, and the Delaware River Basin Commission, maintain the New Jersey Ambient Surface-Water-Quality Monitoring Network (ASWQMN) — a collection of monitoring stations on streams throughout New Jersey. Constituent concentration data from the ASWQMN are used to determine statewide water-quality status and trends, define the quality of water in streams near the downstream end of each NJDEP Watershed Management Area (WMA), define background water quality in each of the four physiographic provinces of New Jersey, and define the quality of water in streams that drain targeted land-use areas. The ASWQMN consists of as many as 126 stations located throughout the 20 WMAs in New Jersey. 

The Federal Clean Water Act and Section 106 of the U.S. Environmental Protection Agency’s Water Pollution Control Grants mandate that states monitor the quality of their ambient waters. In order to meet these requirements, the cooperative Ambient Surface-Water-Quality Monitoring Network (ASWQMN) was established in 1976 to determine the status of and trends in the quality of water in New Jersey’s freshwater streams and rivers. As part of this network, the U.S. Geological Survey (USGS) New Jersey Water Science Center and the New Jersey Department of Environmental Protection (NJDEP), in cooperation with the New Jersey Water Supply Authority and the Delaware River Basin Commission, collect water samples quarterly and streambed-sediment samples annually at surface-water-monitoring stations throughout New Jersey.

USGS Technician using a sampler to collect discrete water-quality samples

USGS Hydrographer Brad Bjorklund using a DH-81 isokinetic sampler to collect a discrete water-quality sample, August 2016. 

(Public domain.)


The ASWQMN provides surface-water-quality information to facilitate the effective planning and management of New Jersey’s water resources and provides water-quality information to the public. The data obtained are used to:

  • Define the quality of water in streams in urban, suburban agricultural, and undeveloped environments
  • Establish, review, and revise water-quality standards
  • Identify causes and sources of water-quality impairments
  • Support the implementation of water-management programs, such as source water protection plans and TMDL development, and to evaluate the effectiveness of these programs.
  • Determine statewide water-quality status and trends
  • Provide the baseline water-quality data needed to evaluate impacts of spills and storm events



The ASWQMN consists of summaries of 126 surface-water-quality monitoring sites including 76 fixed and 50 periodic sites statewide, which are sampled quarterly. The locations of the fixed sites do not change over time and fall into three categories—land-use indicator, watershed integrator, and background sites.  Fifty new sites are randomly selected every 2 years for sampling to ensure a statistically valid statewide assessment. 



YSI Sonde Multi-parameter meter

A multiparameter instrument is used to collect field parameters.  

(Public domain.)


ASWQMN Site Types

Fixed Sites

The fixed, long-term sites determine status and trends of  ambient water-quality of  surface waters in the State of NJ. General objectives of the Fixed sites include:

  • Continued tracking of status and trends in ambient water quality
  • Establish background water quality by physiographic provinces
  • Obtain water quality data that can be correlated with specific land uses
  • Coordinate the collection of water chemistry and biological data at common locations in cooperation with NJ Department of Environmental Protection

Periodic Sites

The periodic component of the ASWQMN allows for a comprehensive statistical evaluation of statewide water quality by routinely changing the sites that are included as a subset of the ASWQMN. This subset of sites provides data from a set of randomly selected sites to assess water quality statewide (1998-2011) or provides data from a set of selected sites in priority regions, basins, and/or watersheds (2011 - present).



What is Collected?

  • Field parameters (dissolved-oxygen concentration, pH, specific conductance, turbidity, and water temperature)
  • In Surface Water - concentrations of major ions, nutrients, dissolved and particulate carbon and nitrogen species, dissolved and suspended solids, ultraviolet absorbance, and selected Per- and Polyfluoroalkyl Substances (PFAS); and, at selected sites, concentrations of trace elements and pesticides.
  • In concentrations of polyaromatic hydrocarbons (PAHs), polychlorinated biphenyl (PCB) compounds, inorganic carbon, organic carbon, and trace elements in streambed sediment at selected sites.