Impacts of climate change and land use change on runoff from a Great Lakes watershed

Daily VEMAP output from the Hadley Coupled Climate Model (HadCM2) and land use projections from the Southeastern Michigan Council of Governments are used to examine the impacts of climate change and land use change on a regional watershed in southeastern lower Michigan. The precipitation, temperature, moisture, and solar radiation output from HadCM2 are processed before they are used as input to a modified version of the Biosphere-Atmosphere Transfer Scheme (BATS). The modified BATS model (BATS/HYDRO) includes the original 18 BATS land use types along with six new urban land classes as well as an improved surface runoff model, which accounts for impervious surfaces and depression storage. The daily VEMAP output is verified against observations and shown to be appropriate for use as input to the BATS/HYDRO model. The BA TS/HYDRO model is then tested with observed NCEP/NCAR Reanalysis Data and shown to reproduce observed runoff for the period 1990 to 1992 with minimal tuning of initial soil moisture content and daily rainfall distribution. The BATS/HYDRO model is then run using VEMAP output as input for two time periods, 1994 to 2003 and 2090 to 2099 and two land use scenarios, current and future. Model results show that changing climate and changing land use will increase the percentage of precipitation that results in surface runoff from 17.1% to 21.4%. This 4.3% increase is partitioned into a 2.5% increase due to climate change and a 1.6% increase due to land use change.