PARENT SESSION
Symposium #20: Extreme event analysis in ecology.
Sponsored by ESA Statistical Ecology and Long Term Studies Sections
Organized by: B. Li and R. G. Balice.
Thursday, August 9, 2001. 8:00 AM to 12:10 PM. Madison Ballroom A
Uncertainty analysis of California streamflow under current and projected climates.
Miller, Norman1, 1
ABSTRACT- Streamflow is a major resource for agricultural and industrial growth as well as the ecological health of the world's sixth largest economy, California. Understanding the timing and magnitude of streamflow trends and the range of uncertainty in predicting such trends is of prime importance to the sustainability of California's productivity and ecology. Recent shifts toward an earlier runoff have been observed and may be attributed to natural low frequency climate phenomena, such as the multi-Decadal Pacific Oscillation. However, the balance of evidence suggests a discernable human influence on the global climate and that increases in the global temperature may be caused by fossil fuel emissions of green house gasses (GHG). A number of studies to determine the potential consequences of increasing GHG concentration have been initiated. The focus here is on understanding the downscaling of global climate information to the watershed scale and determining the likelihood of extreme events, levels of uncertainty, and uncertainty reduction. We have selected eleven watersheds in California and analyzed the mean monthly streamflow for a present day and a future climate. Each set of simulations is based upon the Hadley Centre's HadCM2 simulation and is dynamically downscaled using the NCAR and the Berkeley Lab Regional Climate Models. Resulting watershed mean-area precipitation and temperature were used as input to well calibrated and verified soil moisture accounting-streamflow models for each of the eleven basins. We indicate model bias for present day and the sensitivity of the future climate simulation compared to the present climate simulation. Extreme events are discussed in the context of probabilities of exceedance, histograms, and quantile plots.
KEY WORDS: climate change, streamflow, uncertainty, California