Coupling coordination relationship of water resources, eco-environment and socio-economy in the water-receiving area of the Lower Yellow River

Fully understanding the interrelationship and the coordinated development level of water resources (WR), eco-environment (EE) and socio-economy (SE) is an essential precondition for regional sustainable development. We constructed a complex analytical framework consisting of WR, EE and SE subsystems in the water-receiving area of the Lower Yellow River, and quantitatively investigated the coupling coordination relationship among them. An improved obstacle degree model was developed to analyze the level and the major obstacles of coordinated development from 2001 to 2020, together with the coupling coordination degree model. A prediction model combined by the autoregressive integrated moving average model, the gray model and the artificial neural network model was built to explore the development trend from 2021 to 2025. It was found that (1) the coordinated development level showed a continuous growth from reluctant coordination in 2001–2002 to high coordination in 2015–2020. Spatially, Shandong province was slightly more coordinated than that of Henan province on the whole. (2) With sustained rapid SE development and growing pressure on water supply and environmental capacity, the major obstacles for coordinated development changed from SE factors to WR and EE factors before and after 2010. (3) The coordinated development level will continue to increase in 2021–2025, especially in the "promote WR and EE protection" scenario. In the future, water scarcity will become the key problems for coordinated development. Taking account of the available water diversion from the Yellow River, local government should put more effort into water use efficiency improvement. These results offer an important reference for decision-making and management of regional sustainable development.