Spatial and Temporal Modeling of Road Salts in a Watershed With Mixed, Urban and Agricultural Land Use

Outcomes from these activities present spatial and temporal data for Cl – within a watershed impacted by deicing agents. Results identify seasonal trends in the concentration of Cl – in the LKC watershed, with elevated concentrations in the winter. However, periodic spikes during the summer follow precipitation events. The spikes appear to be associated with Cl – stored within the aquifer system that is released in response to infiltration associated with the precipitation events. The continued use of roads salts will continue to elevate the concentration of Cl – with in the waters. If the application of Cl – ceased, the watershed would not fully recover within 50 years. Residual Cl – would remain in the system. The numerical modeling approach provides an initial evaluation; additional modeling incorporating transient flow will be needed to support all future research activities and develop appropriate BMPs for Cl – applications.The Illinois State Geological Survey and the Illinois State Water Survey have examined the issue of road salts in the Chicago metropolitan area and the subsequent effects on the Illinois River watershed. A pilot GIS model developed to evaluate the transport and fate of Cl – within Illinois indicated that data are spatially and temporally too variable to accurately assess the problem. Our data suggest a balance between spatial resolution and temporal resolution exists. While our sampling points were closer together, the 2-week time period was to coarse to model accurately the pulse of Cl- moving through the system. A finer temporal resolution is needed to develop more adequate GIS and flow models.Increases in road salts use, leading to increases in stream/groundwater chloride concentrations, are fueling the need for useful tools to study chloride fate and transport. Linear regression modeling has been used many times to predict the movement of a contaminant and is used here to predict chloride concentrations downstream. Land cover, representing impervious surfaces, drainage area, and discharge are all controlling factors in chloride concentration downstream, however there must be other factors controlling chloride concentration other than the ones viewed in this study. This study also revealed that there is an impacted area around an urban setting. Chloride concentrations are less diluted upstream due to the chlorides stored and discharging into the upstream sites. More dilution occurs downstream due to the waters discharging into downstream locations are agriculturally derived.’