Author(s): Chaelim Lee; Yeji Son; Sangdan Kim
Linked Author(s):
Keywords: Bivariate return period; Dam operation; Alpha-shape; Drought structure
Abstract: Understanding how dam operations influence hydrological droughts is essential for assessing drought resistance in regulated river basins. This study quantifies how dam regulation restructures drought duration–intensity relationships by comparing drought events derived from natural inflow conditions with those generated under regulated outflow conditions. Hydrological drought events were identified using the Standardized Runoff Index (SRI), and structural differences between natural and regulated regimes were examined through an Alpha-shape-based bivariate return period analysis. The results show that regulated conditions generally reduce drought duration and intensity, demonstrating considerable resistance to drought propagation in most dams. However, this resistance is mainly observed for mild to moderate droughts; under severe drought conditions, the mitigating effect of dam regulation weakens or disappears, revealing vulnerabilities in current operational rules under extreme hydrological stress. These findings highlight how dam operations reorganize drought structure and indicate that Alpha-shape-based bivariate return period analysis provides an effective framework for evaluating drought resilience in regulated river systems.
Year: 2026