Variation of ecosystem services in different water supply-demand risk : Signs from the Yangtze River Basin

The water supply of the Yangtze River Basin (YZRB) is threatened by environmental degradation and increasing supply-demand risk, complicating sustainable development in the region. Water resources and ecosystem services are interconnected; however, the impact of water risks on these systems remains poorly understood. This study employed four indicators to assess water supply-demand risk in the YZRB: supply trend, demand trend, average supply-demand ratio, and supply-demand ratio trend. We also examined the distribution of ecosystem services across different risk grades. The findings indicated the following: (1) The overall water supply-demand situation in the YZRB improved from 2000–2020. The high-risk zone (characterized by grades ranging from disappearing to insufficient recharge, grades 1-5) accounts for about 8.77% of the watershed area, and is mainly located in the construction land and some cultivated land in the middle and lower reaches of the watershed, as well as in the upper reaches of the watershed in Zhiduo County, Qinghai Province. The low risk grade (vulnerable and safe, grades 6 and 7) accounts for about 91.23% of the watershed area and is mainly located in the forests, grasslands and part of the arable land within the watershed. As the water supply-demand risk decreases, vegetation cover increases and human activities decrease. (2) As the water supply-demand risk decreases, soil conservation, carbon storage and flood control gradually increase. However, grain production and habitat quality exhibited opposing trends and showed a weak correlation with water supply-demand risk. • Water supply-demand risk in the Yangtze River Basin are assessed. • Different ecosystem services in the different grade of water risk were observed. • About 8.8% (15.3×104km 2 ) of the land is at high water risk. • GP and HQ were not linked to water risk, in contrast to SC, CS, and FC.