A regional scale assessment of land use/land cover and climatic changes on water and energy cycle in the upper Midwest United States

This study examines the relative impact of regional land-cover/land-use patterns and projected future climate change on hydrologic processes. Historic, present and projected future land cover data were used to drive the variable infiltration capacity (VIC) model using observed meteorological forcing data for 1983-2007 over Wisconsin (USA). The current and projected future (year 2030) land cover data were developed using the land transformation model (LTM). The VIC model simulations were driven using downscaled and bias-corrected projected future climate forcing from three different Intergovernmental Panel for Climate Change (IPCC) AR4 general circulation models (GCMs): HadCM3, PCM and GFDL. Sensitivity results conducted on a single grid cell show that annual average surface runoff and baseflow were increased by 8 and 6 mm, respectively, while evapotranspiration was reduced by 15 mm when a fully forested grid was converted to cropland. Results also indicate that annual average net radiation and sensible heat flux were reduced considerably due to forest-to-cropland conversion, and the reduction was more prominent in winter and spring seasons due to effect of snow albedo. Forest-to-cropland conversion also resulted in increased latent heat flux in summer (JJA) while this land transformation increased the snow water equivalent in winter (DJF) and spring (MAM). Complete conversion of forest to cropland resulted in a decrease of the radiative surface temperature on an annual basis with more cooling occurring in winter and summer. Impacts of historic deforestation were similar to what was expected based on a single grid sensitivity analysis.