Evaluating the Human–Water Relationship over the Past Two Decades Using the SMI-P Method across Nine Provinces along the Yellow River, China

The foundation for ensuring the sustainable utilization of natural resources and human well-being lies in achieving a harmonious balance between nature and humans. In the Yellow River basin (YRB), numerous water crises, including floods, droughts, soil erosion, and water pollution, threaten its crucial role as a significant economic belt and ecological barrier. Unfortunately, less comprehension regarding the complex human–water relationship in this region has impeded watershed water management decision-makers from identifying key priorities for intervention. Here, we selected 29 evaluation indicators, including water resources, environment, ecology, society, economy, and science and technology from three dimensions: healthy water systems, sustainable human systems, and synergy of human–water system. We applied the entropy weight method, hierarchical analysis, and Single index quantification, multiple index synthesis, and poly-criteria integration (SMI-P) methods to quantify the spatial–temporal variation of the human–water harmony degree (HWHD) in nine provinces of the YRB from 2002 to 2021. We observed a consistent increase in the HWHD across all provinces in the YRB in the past two decades. Notably, five provinces have transitioned from Complete disharmony (0 ≤ HWHD ≤ 0.2) to Nearly complete disharmony (0.2 < HWHD ≤ 0.4). Additionally, the average growth rate of the downstream provinces is faster compared to those upstream. By 2021, the HWHD of upstream provinces like Sichuan and Ningxia, constrained by slower growth, became the two lowest provinces of the YRB, at 0.19 and 0.12 respectively. These findings offer valuable guidance for the region and similar areas grappling with the complex challenges of human–water conflicts, providing insights to navigate and address such dilemmas effectively.