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Trends in Water Quality of New Jersey Streams, Water Years 1986-95

U.S. Geological Survey Water-Resources Investigations Report 98-4204

Prepared in cooperation with the New Jersey Department of Environmental Protection

By R. Edward Hickman and Thomas H. Barringer

View the report in Portable Document Format (PDF) WRIR 98-4204 (10.4 MB)


Trend tests were conducted on values of 24 water-quality characteristics measured at 83 surface-water-quality stations on streams in New Jersey during water years 1986-95. Characteristics tested include physical properties and concentrations of nutrients, bacteria, and major dissolved constituents. Seasonal Kendall uncensored tests and tobit regression were used to determine whether unadjusted values of water quality or flow-adjusted values of water quality increased or decreased during this period.

Results of tests on instantaneous streamflow measured at the time of water-quality measurements indicate that streamflow decreased during the period of study; 20 of the 81 stations tested showed decreasing values of instantaneous streamflow. No station showed increasing values of instantaneous streamflow. Because the locations of stations with decreasing streamflow are widespread, it is likely that these trends are due to changes in weather patterns rather than to changes in the amount of water withdrawals.

Results of tests on nutrients are consistent with the expected effects of upgrades to sewage-treatment plants, which occurred in the State of New Jersey during the period of study. For all nutrients tested other than total nitrate plus nitrite, more stations showed decreasing unadjusted and flow-adjusted values than showed increasing unadjusted and flow-adjusted values.

Results for eight major dissolved constituents--specific conductance, total hardness, and dissolved concentrations of solids, sodium, potassium, calcium, magnesium, and chloride--of the nine tested showed more stations with increasing values than stations with decreasing values. Only dissolved sulfate did not show more increases than decreases.

Table of Contents

     Purpose and scope
     Previous investigations
Description of the study area
Methods of analysis
     Data selection and preparation
          Preparation of unadjusted values of water-quality characteristics
          Preparation of flow-adjusted values of water-quality characteristics
     Trend analysis
          Unadjusted values of water-quality characteristics
               Uncensored data sets
               Censored data sets
          Flow-adjusted values of water-quality characteristics
Trends in water-quality characteristics of New Jersey streams
Summary and conclusions
References cited
Appendix 1. Methods used to estimate missing unadjusted values for selected water-quality characteristics
Appendixes 2-25. Summary statistics and results of trend tests for water-quality characteristics of selected surface-water-quality stations in New Jersey, water years 1986-95
     Instantaneous streamflow
     Dissolved oxygen
     Dissolved oxygen (percent)
     5-day biochemical-oxygen demand
     Total alkalinity
     Total nitrogen
     Total ammonia
     Total organic nitrogen
     Total nitrate plus nitrite
     Total phosphorus
     Total organic carbon
     Fecal coliform (MPN)
     Fecal coliform (COL)
     Specific conductance
     Dissolved solids
     Dissolved sodium
     Dissolved potassium
     Total hardness
     Dissolved calcium
     Dissolved magnesium
     Dissolved chloride
     Dissolved sulfate

Suggested citation:
Hickman, R.E., and Barringer, T.H., 1999, Trends in water quality of New Jersey streams, water years 1986-95: U.S. Geological Survey Water Resources Investigations Report 98-4204, 174 p.

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View the report in Portable Document Format (PDF) WRIR 98-4204 (10.4 MB)

For more information about USGS activities in New Jersey contact:
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West Trenton, New Jersey 08628
Telephone: (609) 771-3900
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or access the USGS New Jersey Water Science Center home page at:

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