GLOBAL-WARMING EFFECTS ON NEW-YORK STREAMFLOWS

Impacts of global warming on streamflows were estimated for four large watersheds in New York State using a daily streamflow model. Three different 100-yr daily weather sequences were input to the model. The first was produced using statistics of current (1961-90) weather records. The second and third sequences were based on modifications of these historic statistics according to the monthly mean temperature and precipitation changes associated with a doubling of atmospheric CO2 as predicted by two different general circulation models. For 2 x CO2 conditions, mean annual water balances for all four watersheds indicated modest (1-9%) decreases in precipitation, but much larger (16-42%) decreases in streamflow due to increases in evapotranspiration. Winter flows generally increased, but flows in the remaining seasons often decreased. Monthly streamflow changes varied considerably among watersheds, and we could not attribute these changes to specific differences in land uses or soils.