University of Birjand-Research Group of Drought and Climate Change Journal of Drought and Climate change Research 3092-6076 4 1 2026 05 22 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 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 227 250 3827 10.22077/jdcr.2025.10226.1180 FA Hojjat Allah Keshavarz Ph.D., Student, Department of Natural Resources Engineering and Statistics, Faculty of Agricultural and Natural Resources Engineering, University of Hormozgan, Bandar Abbas, Iran. Ommolbanin Bazrafshan Professor, Department of Natural Resources Engineering and Statistics, Faculty of Agricultural and Natural Resources Engineering, University of Hormozgan, Bandar Abbas, Iran. 0000-0003-2524-3992 Marzieh Shekari Assistant Professor, Department of Mathematics and Statistics, Faculty of Science, University of Hormozgan, Bandar Abbas, Iran. 0000-0001-7243-2185 Hossein Zamani Assistant Professor, Department of Mathematics and Statistics, Faculty of Science, University of Hormozgan, Bandar Abbas, Iran. 0000-0003-1126-6288 Journal Article 2025 10 09 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. 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. https://jdcr.birjand.ac.ir/article_3827_b5b8c484824d8a06f4f3d570bc420313.pdf