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 geographic information s ystems (GIS), We demonstrate this approach by estimating chloride concentra tions in surface water due to road salt transport through ground water in a large coastal watershed in Michigan. The geologically parameterized model for this study provides a good fit to measured hydraulic heads in the water shed and offers a method to estimate spatially and temporally variable solu te fluxes via ground water to streams and lakes. The results demonstrate th at there is a considerable legacy of land use influencing surface water qua lity at the study site. The simulated chloride concentrations produced with salted roads as the only chloride source are similar to measured surface w ater chloride concentrations throughout most of the watershed, except in re gions where other sources for chloride (e.g., high-density septic systems, locations of oil brine fields) likely exist, Impacts of other land use rela ted solutes on baseflow surface water quality could also be explored using this approach. As a result, watershed managers could be provided with quant itative information about the potential impacts of developments and associa ted surface-applied solutes on future surface water quality.