Trajectory in water scarcity and potential water savings benefits in the Yellow River basin

Water scarcity caused by the mismatched spatiotemporal characteristics of water demand and supply threatens the sustainable development of many countries around the world. The Yellow River is the second largest river in China but suffers from intense human activity and scarce water resources. Most current studies on water scarcity assessment have coarse spatial and temporal resolution or are based over short periods, which precludes our understanding of the long-term trajectories of water scarcity. Moreover, the water savings potential and implications for water scarcity alleviation have not been well understood. Here, we conducted a comprehensive analysis of water scarcity in the Yellow River basin (YRB) during the period 1965-2013 using a survey-based water withdrawal dataset and water availability simulated by a well-validated hydrological model. Our results showed that regional water stress has continuously increased over the past five decades and has exceeded the threshold above which both ecological and socio-economic water resources are unsustainable since the 1990 s. Regions with high water stress were mostly distributed between the Lanzhou and Toudaoguai hydrological stations where large irrigated districts occur. There were 30.1-34.7 % and 20.2-35.5 % of the total population suffered from seasonal and perennial water scarcity, respectively, during different periods. Increased water withdrawal and population growth were the primary factors that caused changes in the exposure of the population to water scarcity. Meanwhile, we found that in the absence of upstream water consumption, water scarcity could be alleviated or removed for 4-13.2 % of the downstream population, especially during seasons when water is scarce (e.g., spring and winter). Water efficiency improvements could save 10.1 % of the total water usage (3.3 km3), of which a 7.8 % saving could come from irrigation, roughly 3.4 times the potential saving from industry (2.3 %). Irrigation savings can increase industrial added value by 4 %, while industrial water savings can meet the localized domestic water use of 4 % of urban, or 10 % of rural residents in sub-basins without water scarcity. These findings provide a basis for the design of measures to alleviate water scarcity and facilitate sustainable water resource management in the YRB.