Quantifying ecosystem-human water trade-offs: A clean water scarcity perspective

Yangtze River basin. Water security is a long-standing concern in developing and developed countries, putting rigorous standards on the reliability of approaches applied to identity and access water scarcity. Previous methods for assessing water scarcity have primarily focused on the quantitative and qualitative needs of human water consumption, underestimating the spatiotemporal fluctuation in water demand of ecosystems and the impacts of ecological water scarcity. Here, we introduce a novel approach to estimate clean water stress index by integrating changes in ecosystem requirement and human demand. We calculated clean water stress index (CWSI) and distinguished different types of water scarcity in the Yangtze River basin. Results indicate an upward tendency in CWSI from 2010 to 2020, with severe deficiencies occurred in upstream regions. Nearly 9.52 % of grid cells were threatened by ecology-based water scarcity. The increase in environmental flow requirement exacerbated clean water scarcity, which was unevenly distributed across temporal and spatial dimensions. The weighted Theil’s index increased from 0.283 in 2010–0.417 in 2020. Scenario simulations show that the variations of clean water stress index were predominantly driven by natural factor, while human activity assumed a secondary role. Our proposed approach provides a novel perspective for elucidating the impacts of ecosystem and human on water security. • A novel method to evaluate the water competition between ecosystem and human. • Inadequate environment flow requirement exacerbates clean water scarcity. • The pattern of clean water stress index is predominantly shaped by natural factors. • Natural factors exacerbate regional inequality of clean water scarcity.