TRANSPOSED CLIMATES FOR STUDY OF WATER-SUPPLY VARIABILITY ON THE LAURENTIAN GREAT-LAKES

Hydrological models of the Great Lakes basin were used to study the se nsitivity of Great Lakes water supplies to climate warming by driving them with meteorological data from four U.S. climate zones that were t ransposed to the basin. Widely different existing climates were select ed for transposition in order to identify thresholds of change where m ajor impacts on water supplies begin to occur and whether there are no n-linear responses in the system. The climate zones each consist of 43 years of daily temperature and precipitation data for 1,000 or more s tations and daily evaporation-related variables (temperature, wind spe ed, humidity, cloud cover) for approximately 20-35 stations. A key cha racteristic of these selected climates was much larger variability in interannual precipitation than currently experienced over the Great La kes. Climate data were adjusted to simulate lake effects; however, a c omparison of hydrologic results with and without lake effects showed t hat there was only minor effects on water supplies.