His research emphasizes water quality and environmental flow and transport processes. Recent questions addressed involve fate and transport of chemical and biological agents (e.g., nutrients, algae, bacteria, viruses) in different hydrologic units in the Great Lakes region of North America (watersheds, rivers and streams, lakes and groundwater). His research combines data from field observations with computational models to gain insights into complex biophysical processes, make predictions in managing natural resources and frame policy. Two general research themes of current interest are: (a) Coastal processes and water quality in the Great Lakes and (b) Integrated hydrologic modeling in large river basins.