Beyond intensity: An impact-based drought risk framework for the semi-arid Jequitinhonha River Basin, Brazil

Drought risk assessments commonly rely on intensity-based indicators, which limits their ability to represent the cumulative and socially mediated nature of drought impacts. This study proposes an impact-based drought risk framework that extends the traditional Drought Risk Index (DRI) by explicitly incorporating drought duration and magnitude in addition to intensity by considering a multi-timescale Standardized Precipitation Index (SPI) calculations with a Social Vulnerability Index. The framework was applied to the Jequitinhonha River Basin, a highly vulnerable semi-arid region in Brazil, and validated using 239 officially issued municipal emergency decrees as proxies for observed drought-related impacts. Multivariate analyses indicate that the first two principal components explain approximately 70% of the variance in the combined impact-risk dataset. Drought duration-based risk, particularly when derived from SPI-12, shows the strongest and most consistent association (rho >0.4) with agricultural, economic, social, and water quality impacts, clearly outperforming intensity-based risk assessments. Spatial analyses further reveal systematically higher drought risk in the middle and lower portions of the basin, where prolonged precipitation deficits coincide with elevated social vulnerability. Overall, the impact-based validation confirms that duration-based drought risk indices, especially at longer accumulation timescales, provide a more reliable representation of drought risk in a highly vulnerable semi-arid context. Consequently, the proposed framework offers an operational and transferable basis for drought risk assessment, supporting more effective prioritization, resource allocation, and design of drought mitigation and adaptation strategies.