Document Type : Original Article
Authors
1 hormozgan univercity
2 hormizgan univercity
Abstract
This study focuses on the development and evaluation of an Integrated Drought Index (IDI) using the vine copula method in the Minab watershed. Given the multidimensional nature of drought and the limitations of univariate indices, this research presents a novel approach for combining four key drought indices (SPI, SRI, SPEI, and SMDI). The results indicated that the Frank copula function with dependence parameters of 4.8 and 1.7 for the SPI-SRI and SRI-SMDI pairs, respectively, was the most suitable dependence model. The hierarchical structure of the vine copula identified the SRI index as the pivotal variable, with the strongest correlation (0.82) observed between SPI and SRI. The developed IDI demonstrated a higher capability in identifying compound droughts compared to univariate indices. Return period analysis revealed that under multivariate conditions, the M│SDP scenario at a 0.99 probability corresponds to a return period of 225,337 years, indicating the rarity of high-magnitude drought events occurring alongside other characteristics. The investigation of relationships between drought characteristics also indicated a strong correlation (0.95) between drought intensity and duration. This study proved that the vine copula method, by modeling the nonlinear relationships between drought variables, provides a powerful tool for comprehensive drought risk assessment. The findings can serve as a scientific basis for water resource management decisions in arid and semi-arid regions, although the computational complexity and the requirement for high-quality data are considered limitations of this method.
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