Assessment of urban stormwater chloride and its impact on surface water trends

Project overview

A large number of water bodies have not yet been assessed for their vulnerability to chloride pollution by surface runoff. Researchers are working to address this knowledge gap by applying new analyses and developing predictive relationships to identify high-risk water bodies.

In this project, researchers are developing a comprehensive characterization of chloride in surface runoff of streams and storm drains across Minnesota cities. This characterization will be used to develop a predictive understanding of the watershed, waterbody, climate, and stormwater management factors that influence chloride transport in storm drains and streams.

This work builds on a large Twin Cities metro area stormwater monitoring data collection and incorporates datasets from outside the region, including stream monitoring and time series data for salt application, continuous discharge, and conductivity logging. Researchers are using the data to better understand road salt retention and lag times, and factors influencing chloride trends across a gradient of urban land cover, drainage networks and salt inputs. 

In addition to identifying high-risk water bodies, the research results could also be used to develop procedures to estimate chloride lost from surface runoff to groundwater by infiltration, including through best management practices, and for investigating the influence of salt application reductions and chloride loss to groundwater on chloride trends in selected urban lakes. 

This project will produce an improved characterization of chloride in surface runoff in Minnesota and provide assessment tools to practitioners to identify areas of Minnesota cities where attention should be paid to best management practice siting as well as the vulnerability of lake and stream health.

Research questions

• What are the major watershed and climate drivers of the timing and magnitude of chloride export in stormwater (streams and storm drains)?
• How do surface waters and stormwater BMPs impact the timing and magnitude of chloride transport to downstream waterbodies?
• How are the temporal trends of chloride in representative receiving waters (lakes, streams) impacted by watershed features and by factors such as changes in salt use or implementation of stormwater BMPs?