REGIONAL HYDROLOGIC CONSEQUENCES OF INCREASES IN ATMOSPHERIC CO2 AND OTHER TRACE GASES

Water-balance modeling techniques - modified for assessing climatic impacts - were developed and tested for a major watershed in northern California using climate-change scenarios from both state-of-the-art general circulation models and from a series of hypothetical scenarios. Results of this research suggest strongly that plausible changes in temperature and precipitation caused by increases in atmospheric trace-gas concentrations could have major impacts on both the timing and magnitude of runoff and soil moisture in important agricultural areas. Of particular importance are predicted patterns of summer soil-moisture drying that are consistent across the entire range of tested scenarios. In addition, consistent changes were observed in the timing of runoff - specifically dramatic increases in winter runoff and decreases in summer runoff.