Managing and optimizing urban water supply system for sustainable development: Perspectives from water-energy-carbon nexus

The Sustainable Development Goals call for a balanced and integrated manner to achieve sustainable development in dimensions of socio-economy and environment. Clarifying the nexus between water, energy, and carbon emission (WEC-Nexus) is vital for the city's sustainability. Urban water supply system (UWSS) plays a significant role in water supply and carbon mitigation. Therefore, a multi-objective optimization model was conducted for trade-offs among socio-economic and environmental benefits and applied to a proposed three-stage UWSS of Beijing. According to the sub-indicators of SDGs, we conceived five scenarios to predict the development of water scarcity and environmental impacts, carbon emissions, and economic costs. Using the system dynamics (SD) model, WEC-Nexus and economic performance under different scenarios were simulated. The results showed that the carbon emission was the highest in 2036 under an economically fast-growing scenario (3.47 × 1010 tCO2), and exceptionally-high water demand (4.68 × 109 m3) and poor pollution (8.98 × 109 mg) were produced. The most promising outcomes came from scenarios of technological advancement and ecological conservation. Energy intensity and the behavior of city dwellers led to significant disparities among emitters. We have also recommended constructive policies for Beijing to develop a low-carbon and sustainable ecosystem of UWSS. This study could provide references to measures for sustainable urban development, contributing to efficient water allocation and carbon reduction.