Analysis of Ecological Drought Risk Characteristics and Leading Factors in the Yellow River Basin

With the increasing number and intensity of drought events, understanding the ecological drought risk in the Yellow River Basin has become an important prerequisite for ecological protection in the Basin. Based on the climate, environment, and human activities in the Yellow River Basin, this study constructed the ecological drought risk evaluation index system and model, revealed the spatial distribution characteristics of risk, and analyzed the dominant factors responsible for ecological drought risk through the bivariate local Moran's I index and an optimal parameter-based geographic detector (OPGD) based model. The results show that the high-hazard areas are mainly located in the northeast of the upper reaches and the middle reaches, and the high-exposure areas are mainly located on the northeast slope of the Qinghai–Tibet Plateau, the Qinling Mountains, Ziwuling Mountains, Taihang Mountains, and Liupan Mountains. The high-vulnerability areas are mainly located in the middle and lower reaches of the Basin, and the high-sensitivity areas are mainly located in the source area of the Yellow River, the Loess Plateau area, except for the irrigated areas. High-risk areas of ecological drought are mainly located on the northern Shaanxi Plateau, the central Gansu Plateau, the Ningxia Plain, and the Hetao Plain (except for irrigated areas). From the perspective of land use types, the ecological drought risk from high to low is wasteland, grassland, woodland, farmland, and town areas. High risk areas account for 20.30% of the total watershed area. Through spatial correlation analysis, it was found that the upper reaches were affected by both surface temperature and precipitation, whereas the Guanzhong Basin and lower reaches were mainly affected by precipitation only. The dominant factors associated with vulnerability and sensitivity were precipitation utilization efficiency and fractional vegetation coverage, respectively. Hazard is the dominant factor leading to regional differences in ecological drought risk, and vulnerability, sensitivity, and exposure can alter the local characteristics of the spatial distribution of ecological drought risk.