Copula-based analysis of hydrological drought frequency in Poyang Lake Basin

In this study,hydrological drought characteristics were identified using run-length theory and analyzed using Mann-Kendall method.Meanwhile,the Kolmogorov-Smirnov(K-S) method was employed to evaluate the goodness-of-fit of the eight probability functions.The multivariate analysis method,copula function,was introduced with aim to investigate joint probability behaviors of drought-duration and drought-severity of the major tributaries of the Poyang Lake Basin,the largest fresh-water wetland in China,and the cause and influence of probability change of hydrological characteristics was explored meaningfully.The results indicate that:(1) Lognormal distribution is the candidate distribution function with the highest goodness-of-fit in the study of hydrological drought over the Poyang Lake basin.(2) The number of drought is the least and the drought-duration is the longest in Ganjiang River Basin and Raohe River Basin,while the number of drought is the most and the drought-duration is the shortest in Fuhe River Basin.(3) The frequency of drought-duration and drought-severity in Fuhe River is higher than other River Basin,but the frequency of drought-duration and drought-severity in Raohe River is lower than other River Basin.Hydraulic facilities and forestation are helpful to decrease the drought-severity,but the increasing of agriculture land can increase drought-severity.