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| DOI： |
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| Analyzing the Drought Frequency in Shaying River Basin Using the Three-dimensional Copula Function |
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MA Jianqin, HE Pengfei, PENG Gaohui, CUI Bifeng, LIU Lei
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Liaoyang Hydrology Bureau of Liaoning Provincial， Liaoyang 110000， China
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| Abstract: |
| This paper analyzed the drought characteristics based on data measured in 1951— 2008 from two hydrological stations in the Shaying River Basin. We took standardized runoff index as an indicator of the hydrological drought, calculating the hydrological drought characteristics including drought duration, drought severity, and peak of the drought severity, using the theory of run test. The joint distributions of the drought characteristic variables were analyzed using four types of symmetric and asymmetric Archimedean Copulas functions; the goodness of the fitting of the functions was evaluated using the Kolmogorov-Smirnov test method. The results showed that the Frank Copula function gave the best fitting for two-dimensional joint distributions of two characteristic drought variables, while the M3 copula function worked better for fitting three-dimensional joint distributions of three characteristic drought variables. It was also found that the return period calculated from single variable was greater than that calculated from the two- and three-dimensional distribution for the joint return periods, but less than that from the two-and three-dimensional distributions for the co-occurrence return periods. Thus, the Copula functions are able to describe the multivariate joint distributions of hydrological drought variables in the Shaying River Basin. |
| Key words: Shaying River Basin; Standardized Runoff Index; theory of run; Copulas function; return period |
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