Supplementary Material to "spatially Explicit Assessment of Water Scarcity and Potential Mitigating Solutions in a Large Water-Limited Basin: the Yellow River Basin in China"

Abstract. Comprehensive assessment of the long-term evolution of water scarcity and its driving factors is essential for designing effective water resource management strategies. However, the role of water withdrawal and water availability components in determining water scarcity and potential mitigating measures in large water-scarce basins are poorly understood. Here, an integrated analytical framework was applied to the Yellow River basin (YRB), where the water crisis has been a core issue for sustainable development. Analysis of the water scarcity index (WSI) and other critical indicators, including frequency, duration, and exposed population, suggest that the YRB experienced unfavorable changes in water crisis during 1965‒2013. Irrigation dominated the increase in WSI in the northwest part of the basin before 2000, whereas climate change was primarily responsible for changes in the WSI in most sub-basins during the recent decade. Meanwhile, local water management and climate change adaptation were shown to be important in determining total water availability at the sub-basin scale. Water demand in the 2030s is predicted to be 37.4 km3 based on the trajectory of historical water use, worsening 28.7 % and easing 12.5 % of the total population, respectively. To meet all sectoral water needs, a 10 km3 water deficit is projected. The potential improvements in irrigation efficiency could solve 26 % of this deficit, thereby easing the pressure on external water transfer projects. In conclusion, the integration of water supply and demand-oriented strategies is essential to effectively alleviate the water crisis in the YRB. Our results have vital implications for water resource management in basins facing similar water crises to that in the YRB.