Impacts of land-use change on hydrologic responses in the Great Lakes region

Human activities have historically affected hydrology in the upper Midwestern United States, specifically through the conversion of forests and prairie grasslands to agricultural uses. The hydrologic impacts of land-use change due to settlement on the water balance of three Great Lakes states: Minnesota, Wisconsin, and Michigan were analyzed using the Variable Infiltration Capacity (VIC) large-scale hydrology model, and changes in the spatial distribution of vegetation types were studied. Point model simulations demonstrated that the VIC model simulated changes in average annual and monthly evapotranspiration (ET) and total runoff response were in the same direction and had similar magnitudes to values from other published land-use change studies. At regional scales, simulated changes resulting from land-use modifications varied spatially and seasonally, but were strongly correlated to the type of vegetation conversion and the geographic location of the land-use type centroid. Deforestation was most dramatic in the central part of the study domain where five million hectares of deciduous forest have been converted to wooded grasslands and row crop agriculture, which resulted in a 5–15% decrease in ET and a 10–30% increase in total runoff. Northern areas, where land-use change was primarily from majority evergreen to majority deciduous forest, experienced decreases of 5–10% in ET and increases of 20–40% in total runoff. The southern and western parts of the study domain were dominated by a conversion from prairie grasslands to row agriculture crop, resulting in a 10–15% increase in ET and a 20–30% decrease in total runoff.