中文摘要：

基于Clayton copula和Kendall分布函数分析广东西江马口站和北江三水站枯水流量的联合分布及其风险概率。根据两站流量之间的时空关联与变异,以1959—2010年西江马口站历年连续7日平均最小流量和对应期间的北江三水站枯水流量为样本,分别计算1959—1985年和1986—2010年两个时段（分别称为样本A和样本B）的西江北江枯水流量联合分布的＂或＂重现期、＂且＂重现期和二次重现期及其最可能的设计分位数。结果表明：1样本B中马口站的枯水流量设计值小于样本A相应重现期设计值,三水站则显著增大;21985年后西江和北江枯水流量同频率遭遇的可能性较前期明显减小;3二次重现期所对应的累积频率代表了特定设计频率情况下西江和北江枯水流量遭遇的风险率;4由更严谨的二次重现期计算的马口站枯水流量最大可能设计值Q7d,T=20a、Q7d,T=10a和Q7d,T=2a设计值或更适合分别作为西江三角洲供水规划、生态需水和调水压咸设计参考值。

英文摘要：

The risk analysis approach based on Clayton copula and Kendall distribution function is used to analyze the joint distribution of low flows between Xijiang River in Makou and Beijiang River in Sanshui,which are connected through the Sixianjiao waterway in Guangdong,China. Using samples with seven consecutive average minimum flows of Makou gauge and the corresponding low flows of Sanshui gauge during the hydrological years 1959—2010,the＂OR,＂＂AND,＂and secondary return period of the joint distributions of low flows between 1959 and 1985（ referred to as sample A） and between 1986 and 2010（ referred to as sample B） of the two rivers were calculated using the Clayton copula and Kendall distribution function,respectively. The main conclusions of this study can be summarized as follows： 1 The design quantiles of the low flows of Makou in sample B are less than the design quantiles for the corresponding return periods of sample A,while the design quantiles of low flows significantly increased in Sanshui;2 The encounter probabilities of low flows between Xijiang River and Beijiang River were significantly reduced,with the same frequencies of samples A and B since 1985; 3 The cumulative frequencies calculated using the secondary return period represent the risk possibilities between Xijiang River and Beijiang River low flows with specific design frequencies; 4 The Q7 d,T = 20 a,Q7d,T = 10 a,and Q7 d,T = 2aof the most likely design quantiles calculated using the secondary return period for the Makou and Sanshui gauges may be more suitably used as the design reference for water supply planning of the West River Delta during the low water season.