Large recent increases in Cl in northeastern lakes as an indicator of regional development pressure

Presentation (pdf document)

Steve Kahl, Plymouth State University, NH, jskahl@plymouth.edu
Katherine Webster, University of Maine, Orono, ME
Dari Sasson, Plymouth State University, Plymouth NH
Catherine Rosfjord, West Virginia Department of Environmental Protection
Melissa Greenawalt-Yelle, Plymouth State University, NH
June Hammond Rowan, Plymouth State University, NH

Recent reports have linked elevated concentrations of Cl in surface waters to application of salt as a road deicer. We report substantial increases in Cl between 1984 and 2004 in Cl in a statistical population of nearly 4,000 low ANC lakes in the Northeast US. In 20 years the median Cl in the population increased from 1.7 mg/L to almost 3.5 mg/L. Most of the lake population in urbanized southern New England increased in Cl, compared to only 18% of lakes in more remote Maine. Among lakes classified as salt-impacted (half of the total population), median Cl nearly tripled. The other half of the lakes, those in more remote locations, did not exhibit a change in Cl. This recent increase in Cl reflects increasing inputs from road salting, and is coincident with other NPS pollutants and increasing eutrophication of lakes. Chloride is becoming an issue for potable water and ecosystem function in some areas of the northeast. In some communities, water quality non-attainment for Cl standards means that future development will be allocated zero Cl in order to meet TMDLs. Mitigation of high Cl will require changes in the density of development, altered winter road maintenance, modification in the imperviousness characteristics of new development, and/or new chemical approaches to ice control.