Comprehensive drought risk assessment and its driving mechanism for the water source area of the Western Route of South-to-North Water Diversion Project in China

Abstract

The Western Route of South-to-North Water Diversion Project (WR-SNWDP) is a key national infrastructure in China to transfer water from the headwaters of the Yangtze River. The complicated environment and escalating climate change impacts, such as extreme droughts in the upper Yangtze Basin, pose serious challenges to the implementation of WR-SNWDP. However, the spatio-temporal evolution of drought risk and its driving mechanism in this area remains unclear. Here, the water source area of WR-SNWDP was selected as the study area and drought hazards characteristics were first extracted considering both the meteorological and hydrological drought indices. A multi-dimensional drought evaluation system of “hazard, vulnerability, and exposure” was established that takes into account ecosystem resilience as well as disaster prevention and mitigation capacity. A Random Forest-based comprehensive drought risk assessment was conducted from 2001 to 2018, and the driving mechanisms were analyzed using Geodetector. Our results indicate that there are evident spatio-temporal heterogeneities of drought risk with high risk areas shifting westward, particularly in the Tongtian and Jinsha River Basins. Drought risk peaked in 2006, with ecosystem resilience playing a significant role in response to drought risk formation. Precipitation, temperature, and vegetation are dominant factors, and their interactions, particularly between precipitation and vegetation, strongly explain drought risk evolution. The results underscore the significant trends in spatio-temporal shifts of drought risk in the context of climate change and highlight that more attention needs to be paid to the coupling effects among driving factors on drought risk in the water source area of WR-SNWDP.