Water-Quality Trends in New England Rivers During the 20th Century

Water-Resources Investigations Report 03-4012

By Keith W. Robinson, Jean P. Campbell, and Norbert A. Jaworski

The full report is available in pdf.



Water-quality data from the Merrimack, Blackstone, and Connecticut Rivers in New England during parts of the 20th century were examined for trends in concentrations of sulfate, chloride, residue upon evaporation, nitrate, and total phosphorus. The concentrations of all five of these constituents show statistically significant trends during the century. Annual concentrations of sulfate and total phosphorus decreased during the second half of the century, whereas annual concentrations of nitrate, chloride, and residues increased throughout the century. In the Merrimack River, annual chloride concentrations increased by an order of magnitude. Annual nitrate concentrations also increased by an order of magnitude in the Merrimack and Connecticut Rivers. These changes in the water quality probably are related to changing human activities. Most notable is the relation between increasing use of road de-icing salts and chloride concentrations in rivers. In addition, changes in concentrations of nitrate and phosphorus probably are related to agricultural use of nitrogen and phosphorus fertilizers. For all the water-quality constituents assessed, concentrations were greatest in the Blackstone River. The Blackstone River Basin is smaller and more highly urbanized than the other basins studied. Data-collection programs that span multiple decades can provide valuable insight on the effects of changing human population and societal activities on the water quality of rivers. This study was done as part of the U.S. Geological Survey's National Water-Quality Assessment Program.




Purpose and Scope


Data Sources and Methods of Analysis

Description of the Merrimack, Blackstone, and Connecticut Rivers

Changes in the Water Quality of the Merrimack, Blackstone, and Connecticut Rivers During the
20th Century





Total Phosphorus


References Cited

For additional information write to:

District Chief
U.S. Geological Survey
New Hampshire/Vermont District
361 Commerce Way
Pembroke, NH 03275-3718
or through our Web site at


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