摘要
Climate change is likely to lead to an increased frequency and intensity of extreme weather events, including floods and droughts. Hydrological drought refers to deficiencies in surface and subsurface water supplies and is usually measured by streamflow, and lake, reservoir and ground water levels. Properly assessing hydrological drought is crucial to decision-making and management of regional water resources. In this study, changes in hydrological drought frequency over the Xijiang River Basin in South China are investigated through an analysis of daily streamflow data observed at major hydrological stations along the river during the period 1951-013. The main results are as follows: (1) Standardized Runoff Drought Index is a suitable measure for regional hydrological drought research in the Xijiang Basin, as its correlation coefficient with actual disaster areas is above 0.6 for Wuzhou hydrological station; (2) the hydrological droughts in the Xijiang Basin typically have a short duration that are often less than 60?days; (3) there were three serious hydrological drought periods (the 1950s to mid-1960s, the late 1980s to mid-1990s and the mid-2000s to early 2010s) and two drought relief periods (the late 1960s to mid-1980s and the late 1990s to early 2000s) for the Xijiang Basin; (4) hydrological droughts in the Xijiang River occur frequently and are mainly concentrated in summer and spring, although serious hydrological droughts can easily arise in autumn. Droughts tend to be more frequent but less severe moving from upstream to downstream, and a long duration often accompanies high severity for a single drought event; and (5) severe hydrological droughts in upstream and midstream areas are characterized by long durations and high severities, respectively. Return periods based on copula could generally reflect actual drought situations, and severe and extreme hydrological droughts occur when return periods greater than 20 and 50?a, respectively.