Development and Projection of a Composite Drought Index Using Copula Functions under Future Emission Scenarios: Application of CMIP6 Climate Models in the Minab Esteghlal Dam Watershed

Keshavarz, Hojjat Allah; Bazrafshan, Ommolbanin; Shekari, Marzieh; Zamani, Hossein

doi:10.22077/jdcr.2025.10226.1180

Document Type : Original Article

Authors

¹ Ph.D., Student, Department of Natural Resources Engineering and Statistics, Faculty of Agricultural and Natural Resources Engineering, University of Hormozgan, Bandar Abbas, Iran.

² Professor, Department of Natural Resources Engineering and Statistics, Faculty of Agricultural and Natural Resources Engineering, University of Hormozgan, Bandar Abbas, Iran.

³ Assistant Professor, Department of Mathematics and Statistics, Faculty of Science, University of Hormozgan, Bandar Abbas, Iran.

https://doi.org/10.22077/jdcr.2025.10226.1180

Abstract

Composite droughts, which simultaneously affect both meteorological systems and water resources, pose a serious threat to arid and semi-arid regions. This study aimed to model droughts under future climate change scenarios using copula functions. Historical data (1989–2020) and statistically downscaled outputs from the CanESM5 climate model under SSP126, SSP370, and SSP585 scenarios for the future period (2021–2040) were utilized. Watershed runoff was simulated using the IHACRES model. P-12 and R-12 were calculated, and a joint hydro-meteorological drought index (JDHMI) was developed using copula functions. Drought characteristics (frequency, intensity, duration, and magnitude) and trends were analyzed for both historical and future periods. Results indicated that the composite JDHMI exhibited less fluctuation compared to univariate indices, providing a more stable and comprehensive depiction of drought conditions. Under climate change scenarios, the drought pattern is projected to shift from fewer but longer and more severe droughts to more frequent, shorter-duration droughts, particularly under the SSP585 scenario. Although average duration and intensity decreased in some scenarios, the drought "magnitude" index—integrating intensity and duration—increased across all future scenarios, indicating an overall intensification of drought content. Furthermore, the frequency of "severe" droughts significantly increased under all scenarios. Trend analysis confirmed a significant and accelerating decline in the JDHMI index in the future. This framework can serve as a scientific basis for early warning systems, and sustainable water resource management in the face of climate change.

Keywords

Main Subjects

Drought

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Development and Projection of a Composite Drought Index Using Copula Functions under Future Emission Scenarios: Application of CMIP6 Climate Models in the Minab Esteghlal Dam Watershed

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Volume 4, Issue 1 - Serial Number 13May 2026Pages 227-250

Volume 4, Issue 1 - Serial Number 13
May 2026
Pages 227-250