Assessing and predicting Lake Chloride Concentrations in the Lake-Rich Urbanizing Halifax Region, Canada

Abstract

Study region: Halifax, Nova Scotia, Canada. Study focus: Many lakes in the Halifax region are approaching or exceeding the chronic freshwater aquatic life guideline for chloride (Cl-), presumably due to the application of deicing salts. These exceedances represent an ecological risk that requires mitigation for lakes currently experiencing high Cl-, and preventative steps should be taken to protect lakes that will be impacted by future development. In this study we paired geospatial analysis with linear regression methods to identify key factors contributing to elevated Cl- in Halifax lakes, and applied a mass balance modeling approach to estimate annual Cl- loading rates for dominant land uses within the region. New hydrological insights for the region: - The watershed variables found to be most predictive of mean lake [Cl-] were the % urban coverage, road density, and stormwater pipe density in a watershed. - Annual Cl- loading rates for the four primary land use categories in the region were: rural 1–3 g/m2/yr, commercial 0–9 g/m2/yr, residential 97–162 g/m2/yr, and roads 804–964 g/m2/yr. - The mass balance model developed in this study could be used to predict Cl- loading associated with planned developments, and subsequent impacts on receiving lakes.