Dynamic simulation of the water-energy-food nexus (WEFN) based on a new nexus in arid zone: A case study in Ningxia, China

'Quantity-type' water shortages and 'quality-type' water shortages are important factors that constrain the security and coordinated development of regional water-energy-food nexus (WEFN) system, especially in arid areas where water is scarce. Therefore, it is of great significance to accurately identify the coupling and mutual feedback effects of the WEFN on different types of water resources demand. This information can be used to understand the regional WEFN and alleviate pressure on regional water resources. In this study, a new relationship diagram of the WEFN system was formed with the incorporation of the water footprint (WF), which can characterize a system's water demand, water source type, water pollution amount and pollution type. Based on this nexus, a WEFN system feedback model suitable for arid regions was established using the system dynamics approach. Taking Ningxia, China, as a case study, six future scenarios were designed, and the development trends of the WEFN system under different development scenarios were simulated to explore the impact of different policies on the WEFN. Finally, practical suggestions to promote the synergistic development of WEFN systems were proposed. The results indicate that the rational distinction between 'quantity-type' and 'quality-type' water resources can effectively alleviate the regional water stress and promote the coordinated development of water, energy and food. And the water security is the main factor that constrains the coordinated development of the WEFN system in Ningxia. Incorporating water environmental pollution policies into the water subsystem is necessary. Furthermore, the resource saving scenario and energy production restructuring adjustment scenario can effectively alleviate the energy security problems that has resulted from rapid economic development. In addition, Ningxia urgently needs to optimize its food production structure to address a continuous reduction in the food security index.