Skip Links

USGS - science for a changing world

Scientific Investigations Report 2012–5047

Prepared in cooperation with the New Jersey Department of Environmental Protection

Variations in Statewide Water Quality of New Jersey Streams, Water Years 1998–2009

By Heather A. Heckathorn and Anna C. Deetz

Thumbnail of and link to report PDF (21 MB)Abstract

Statistical analyses were conducted for six water-quality constituents measured at 371 surface-water-quality stations during water years 1998–2009 to determine changes in concentrations over time. This study examined year-round concentrations of total dissolved solids, dissolved nitrite plus nitrate, dissolved phosphorus, total phosphorus, and total nitrogen; concentrations of dissolved chloride were measured only from January to March. All the water-quality data analyzed were collected by the New Jersey Department of Environmental Protection and the U.S. Geological Survey as part of the cooperative Ambient Surface-Water-Quality Monitoring Network.

Stations were divided into groups according to the 1-year or 2-year period that the stations were part of the Ambient Surface-Water-Quality Monitoring Network. Data were obtained from the eight groups of Statewide Status stations for water years 1998, 1999, 2000, 2001–02, 2003–04, 2005–06, 2007–08, and 2009. The data from each group were compared to the data from each of the other groups and to baseline data obtained from Background stations unaffected by human activity that were sampled during the same time periods.

The Kruskal-Wallis test was used to determine whether median concentrations of a selected water-quality constituent measured in a particular 1-year or 2-year group were different from those measured in other 1-year or 2-year groups. If the median concentrations were found to differ among years or groups of years, then Tukey’s multiple comparison test on ranks was used to identify those years with different or equal concentrations of water-quality constituents. A significance level of 0.05 was selected to indicate significant changes in median concentrations of water-quality constituents.

More variations in the median concentrations of water-quality constituents were observed at Statewide Status stations (randomly chosen stations scattered throughout the State of New Jersey) than at Background stations (control stations that are located on reaches of streams relatively unaffected by human activity) during water years 1998–2009. Results of tests on concentrations of total dissolved solids, dissolved chloride, dissolved nitrite plus nitrate, total phosphorus, and total nitrogen indicate a significant difference in water quality at Statewide Status stations but not at Background stations during the study period. Excluding water year 2009, all significant changes that were observed in the median concentrations were ultimately increases, except for total phosphorus, which varied significantly but in an inconsistent pattern during water years 1998–2009.

Streamflow data aided in the interpretation of the results for this study. Extreme values of water-quality constituents generally followed inverse patterns of streamflow. Low streamflow conditions helped explain elevated concentrations of several constituents during water years 2001–02. During extreme drought conditions in 2002, maximum concentrations occurred for four of the six water-quality constituents examined in this study at Statewide Status stations (maximum concentration of 4,190 milligrams per liter of total dissolved solids) and three of six constituents at Background stations (maximum concentration of 179 milligrams per liter of total dissolved solids). The changes in water quality observed in this study parallel many of the findings from previous studies of trends in New Jersey.

First posted April 19, 2012

For additional information contact:
Director, New Jersey Water Science Center
U.S. Geological Survey
810 Bear Tavern Road, Suite 206
West Trenton, NJ 08628
http://nj.usgs.gov/

Part or all of this report is presented in Portable Document Format (PDF); the latest version of Adobe Reader or similar software is required to view it. Download the latest version of Adobe Reader, free of charge.


Suggested citation:

Heckathorn, H.A. and Deetz, A.C., 2012, Variations in statewide water quality of New Jersey streams, water years 1998–2009: U.S. Geological Survey Scientific Investigations Report 2012–5047, 54 p.



Contents

Abstract

Introduction

Purpose and Scope

Study Area

Previous Investigations

Study Methods and Design

Selection of Water-Quality Stations

Field and Laboratory Measurements and Sample Collection

Streamflow

Preparation for Statistical Analysis

Laboratory Reporting Conventions

Recensoring of Nondetect Data

Calculation of Total Nitrogen

Calculation of Summary Statistics

Kaplan-Meier Method

Regression on Order Statistics Method

Highly Censored Datasets

Identification of Variations in Statewide Water-Quality

Kruskal-Wallis Test

Tukey’s Multiple Comparison Test

Mann-Whitney Test

Graphical Representation of Data

Variations in Statewide Water Quality of Streams in New Jersey

Identification of Variations in Statewide Water Quality

Total Dissolved Solids

Dissolved Chloride

Dissolved Nitrite Plus Nitrate

Dissolved Phosphorus

Total Phosphorus

Total Nitrogen

Identification of Consistent Increases or Decreases in Statewide Water Quality

Comparison of Water Quality between Statewide Status Stations and Background Stations

Comparison of Variations in Water Quality to Streamflow

Comparison of Variations in Annual Water Quality to Results of Previous Trend Tests

Summary and Conclusions

Acknowledgments

References Cited

Appendix 1. Description of selected Background and Statewide Status water-quality stations included in the study of variations in statewide water quality of New Jersey streams, water year 1998

Appendix 2. Description of selected Background and Statewide Status water-quality stations included in the study of variations in statewide water quality of New Jersey streams, water year 1999

Appendix 3. Description of selected Background and Statewide Status water-quality stations included in the study of variations in statewide water quality of New Jersey streams, water year 2000

Appendix 4. Description of selected Background and Statewide Status water-quality stations included in the study of variations in statewide water quality of New Jersey streams, water years 2001–02

Appendix 5. Description of selected Background and Statewide Status water-quality stations included in the study of variations in statewide water quality of New Jersey streams, water years 2003–04

Appendix 6. Description of selected Background and Statewide Status water-quality stations included in the study of variations in statewide water quality of New Jersey streams, water years 2005–06

Appendix 7. Description of selected Background and Statewide Status water-quality stations included in the study of variations in statewide water quality of New Jersey streams, water years 2007–08

Appendix 8. Description of selected Background and Statewide Status water-quality stations included in the study of variations in statewide water quality of New Jersey streams, water year 2009

Appendix 9. Description of selected Index streamgaging stations included in the study of variations in statewide water quality of New Jersey streams, water years 1998–2009


Accessibility FOIA Privacy Policies and Notices

Take Pride in America logo USA.gov logo U.S. Department of the Interior | U.S. Geological Survey
URL: http://pubs.usgs.gov/sir/2012/5047/
Page Contact Information: GS Pubs Web Contact
Page Last Modified: Thursday, January 10, 2013, 07:50:32 PM