Copula-Based Analysis of Hydrological Extremes and Implications of Hydrological Behaviors in the Pearl River Basin, China

It is believed that the currently increasing temperature, also known as global warming, has altered the hydrological cycle and thus the hydrometeorological extremes become frequent. In this study, the authors analyze hydrological extremes defined by 7-day high flow and low flow of the Pearl River Basin by using a copula family. The results indicate that the concurrent occurrence of extreme high and low flow is of small probability. It implies that the probability is small that the lower Pearl River Basin is attacked by heavy droughts or floods because of the combined effects of high or low flow of the two major tributaries of the Pearl River, i.e., the West and North Rivers. Therefore, the authors can conclude that the joint probability of hydrological extremes of two tributaries of a river basin could be small, albeit the occurrence of hydrological extremes of an individual river is of large probability. Besides, the results of this study also reveal increasing 7-day low flow in winter, which should be because of seasonal shifts of precipitation on the basis of the previous studies. The results of this study mean much for the sound human understanding of statistical behaviors of hydrological extremes in humid regions, and also for effective water resource management and development of human mitigation to the natural hazards in the changing environment.