Uncertainty evaluation of copula analysis of hydrological droughts in the.pdf

The joint probability behaviors of extreme hydro-eteorological events, such as droughts, have been receiving
increasing attentions in recent years. Since extreme hydro-meteorological events are reflected by more than
one variable, such as duration and intensity, copula functions have been widely applied. However, uncertainties of copula- based analysis of hydrological droughts as a result of selection of marginal distribution and copulas
have not yet received significant concerns. The aim of this study is to evaluate such uncertainties based on
Bayesian approach. The method is used to analyze hydrological drought in the East River basin (China), which is the principal supplier ofwater resources for megacities in the Pearl River Delta and also for Hong Kong. The results indicate that the credible intervals of most likely design drought events with a return period of 20 years in
terms of drought severity and duration are considerably large at all stations in the East River basin, covering the drought event curves at return periods of 10 and 50 years. Also the influences of heavy-tailed marginal distribution on the uncertainty evaluation of joint distribution have been investigated. Results show that the stronger the
heavy- tiledmarginal distribution, the greater the uncertainty of the joint distribution, especially for the extreme
event. Results of this study provide a technical reference for uncertainty evaluation in copula-based analysis of drought events at regional and global scales. The large credible interval of drought severity and duration greatly challenges measures of mitigation of drought hazards and water resource management.