Study on the Nexus Effects of Water Conservation, Pollutant Control and Carbon Emissions of a Multi-Source Water Supply System

Water scarcity and the greenhouse effect are two global issues that have attracted researchers’ attentions for decades. A multi-source water supply system has been established in a typical Chinese city experiencing a water shortage—namely, Yiwu City—in order to solve the city’s water shortage problem. Our study focuses on the integrated analysis of water conservation, pollutant control and carbon emissions in the multi-source water supply system, and a comprehensive model is derived in order to simulate these three factors together. It is confirmed that the multi-source water supply system has significantly improved the efficiency of local water allocation and the water supply guarantee rate, considering that the replacement rate of reclaimed water varies from 0% to 50%. It is anticipated that water conservation and pollutant control can be achieved simultaneously in Yiwu City, although accomplishing these goals and also reducing carbon emissions is difficult due to the significant impact of local topography and geomorphology. When the proportion of reclaimed water used in landscape ecological water increases from 0 to 50%, COD emissions decrease by 656 t/a, NH3-N emissions decrease by 11 t/a, and the corresponding carbon emissions increase by 0.096 × 104 t CO2/a. The simulation results of this study provide important references for addressing water shortage issues and achieving carbon emission reduction goals in Yiwu City and other similar cities experiencing water shortages in the future.