Relating Road Salt to Exceedances of the Water Quality Standard for Chloride in New Hampshire Streams

Abstract

Six watersheds in New Hampshire were studied to determine the effects of road salt on stream water quality. Specific conductance in streams was monitored every 15 min for one year using dataloggers. Chloride concentrations were calculated from specific conductance using empirical relationships. Stream chloride concentrations were directly correlated with development in the watersheds and were inversely related to streamflow. Exceedances of the EPA water quality standard for chloride were detected in the four watersheds with the most development. The number of exceedances during a year was linearly related to the annual average concentration of chloride. Exceedances of the water quality standard were not predicted for streams with annual average concentrations less than 102 mg L(-1). Chloride was imported into three of the watersheds at rates ranging from 45 to 98 Mg Cl km(-2) yr(-1). Ninety-one percent of the chloride imported was road salt for deicing roadways and parking lots. A simple, mass balance equation was shown to predict annual average chloride concentrations from streamflow and chloride import rates to the watershed. This equation, combined with the apparent threshold for exceedances of the water quality standard, can be used for screening-level TMDLs for road salt in impaired watersheds.

Environmental change in Lake Champlain revealed by long-term monitoring

“…Increasing chloride concentrations have been found in lakes (Chapra et al, 2009;Novotny and Stefan, 2009), rivers (Robinson et al, 2003;Kauschal et al, 2005), and groundwater (Mullaney et al, 2009;Eyles and Meriano, 2010) across the northern hemisphere, particularly as a result of the application of deicing salts for winter road maintenance (Chapra et al, 2009;Daley et al, 2009;Trowbridge et al, 2010). Road salt application rates in Vermont state highway districts within the Lake Champlain Basin increased during the 1990s but then declined in more recent years (Fig.…”

River chloride trends in snow-affected urban watersheds: increasing concentrations outpace urban growth rate and are common among all seasons

“…Multiple studies have observed chloride concentrations greater than these benchmark concentrations in streams as a result of road salt runoff. These studies have included local (Ruth, 2003;Trowbridge et al, 2010;Allert et al, 2012;Morgan et al, 2012), regional (Kelly et al, 2012b), and national geographic scopes (Corsi et al, 2010).…”

Increasing chloride concentrations in Lake Constance: characterization of sources and estimation of loads

“…Kelly et al (2008) reported a threefold concentration increase of chloride in a New York creek over 20 years and estimated that deicing salts, sewage, water softeners and natural background contributed 91, 4, 3 and 2%, respectively. In New Hampshire streams, Trowbridge et al (2010) showed that [90% of the chloride originated from road salt. Imported loads amounted to 45-98 t Cl -km -2 year -1 and were correlated with development in the watershed.…”