Identifying Potential Land Use-derived Solute Sources to Stream Baseflow Using Ground Water Models and GIS

This paper presents an approach to examine potential relationships between land use-derived solutes and baseflow surface water quality using regional ground water and solute transport models linked to GIS. We demonstrate this approach by estimating the chloride fluxes from road salt through ground water into surface water in a regional coastal watershed in Michigan. The geologically parameterized model for this case study provides a good fit to measured hydraulic heads in the watershed and allows us to estimate spatially and temporally variable solute fluxes via ground water to streams and directly to the Great Lakes. The results demonstrate that there is a considerable legacy of land use influencing surface water quality at the study site. The simulated chloride concentrations are similar to measured surface water chloride concentrations throughout most of the watershed, except in regions where other sources for chloride (e.g., septic systems, locations of oil brine fields and high-density human populations) likely exist. Impacts of other land use related solutes on baseflow surface water quality could also be explored using this approach. As a result, watershed managers could be provided with better information about the potential impacts of developments and associated surface-applied solutes on future surface water quality.