Research on the risk of drought disasters in the middle reaches of the Yellow River coupled with ecosystem entity

ABSTRACT Drought is one of the most significant natural disasters. In this study, we utilized the middle reaches of the Yellow River as the subject of our investigation. We characterized the exposure of ecosystem disaster-bearers by NDVI and established a probabilistic framework for assessing the vulnerability of ecosystems under drought stress, coupling ecosystems and human society disaster-bearers. The SPI was selected to identify the attributes of drought by employing the travel theory, and the bivariate joint distribution of drought duration and intensity was constructed by utilizing the Copula function. The temporal and spatial changes in drought risk in the middle reaches of the Yellow River are investigated using the risk calculation formula defined by the IPCC. The results indicate that a few areas, including the Wei River, Wuding River, Fen River, and Yiluo River basins, are prone to drought events with low drought duration and low drought intensity. The drought risk exhibited an upward trend, gradually expanding outward from the mainstem area. The area of high drought risk in the two-variable AND relationship migrated upstream from the downstream of the Wuding River, the Beiluo River, the Jing River, the Wei River, and the Fen River.