Coevolution and its influencing factors of the water resources–economy–society–environment composite system in the Yellow River basin

Improving the coevolution level of the water resources–economy–society–environment (WESE) composite system is important for guaranteeing resource security, maintaining an ecological balance and realizing sustainable development. We constructed an index system consisting of water resources, economy, society and environmental subsystems in the Yellow River Basin (YRB). Based on the principle of synergism and the logic of the sequence parameters–subsystem–composite system, the Haken model was introduced to evaluate the coevolution level of the WESE composite system from 2009 to 2022. The geographic detectors was employed to identify the key influencing factors of WESE coevolution. It was revealed that (1) the coevolution level of the WESE composite system exhibited an overall upward trend, with the synergy scores increased from 0.48 to around 0.61. (2) The coevolution levels arranged from high to low are upstream, midstream, and downstream. There was a general uptrend of coevolution levels for all of the provinces, even though parts of them fluctuated strongly. (3) The factors influencing the coevolution level were mainly the water resources subsystem factors. Some targeted suggestions are proposed from the aspects of water resource endowment, water use efficiency, water use structure, and population pressure. These results provide important decision-making references for promoting the coordinated and sustainable development of the WESE composite system in the YRB.