Improving synergy of the water-agriculture-ecology system in arid areas using a novel co-optimization model

In arid areas, the intricate interconnections and competition among water, agriculture, and ecology are particularly pronounced. Enhancing the synergy within the water-agriculture-ecology (WAE) system, while seeking common ground of competing sectors, presents a formidable challenge in managing water and land resources. In this study, the synergy of the WAE system was assessed using a coordinated development degree function, which was developed by considering the coefficient of variation and spatial distance projection. We investigated the multi-factor dynamic regulation of the WAE system through a water-agriculture-ecology co-optimization (WAECO) modelling framework, which adheres to a regulatory model that follows global-to-local optimization and bottom-up feedback. Using this framework, key factors, such as reservoir water supply, groundwater exploitation, and planting structure in the Shiyang River Basin (SRB), a typical arid basin in northwest China, were regulated. Results indicated crop yields and economic benefits in the baseline year reflected increments of 1.2 % and 5.4 %, respectively, compared to the actual scenario, while simultaneously increasing ecological water satisfaction by 11.1 % post-co-optimization. Through bilateral regulations between supply and demand, the annual average water deficit of the WAE system notably decreased from 7.5 % to 3.4 % in the mixed irrigation area of Liuhe midstream. The WAECO model effectively reconciled competing sectoral interests and improved the synergy of the WAE system, as indicated by a 6.3 % improvement in the coordinated development degree over the static regulation model. The new framework integrates a broad spectrum of regulatory factors and provides decision-makers with thorough and practical information, thereby facilitating the integrated management of the WAE system in arid areas.