SALINITY OF LAKE MICHIGAN TRIBUTARIES AS AFFECTED BY ROAD SALTING

Application of de-icing salts to roads, sidewalks, and parking lots has become a common occurrence in much of North America with increasing volumes of salt applied in the past half-century. This salt is ultimately carried away from the applied surfaces after dissolution and has been shown to raise salinity levels in surrounding soils and groundwater with much of the salt added to streams and carried through the local stream network out of the watershed. This research focuses on three small tributary streams near the headwaters of Salt Creek, a tributary of the East Arm Little Calumet River in northwest Indiana which flows into Lake Michigan. Each tributary drains a landscape with a distinct level of urbanization with one tributary sampled downstream of an impoundment reservoir. Unlike previous studies which just focused on changing conductivity or ion concentration, this work included discharge measurement to assess total salt discharge and the role of an in-stream reservoir on concentration moderation. Preliminary results show variation based on land use with moderation of salinity peaks by the reservoir as expected. Future continuation of the project aims to identify the volumes of de-icing salts applied within each catchment and quantify the proportions entering soils, streams, and groundwater.