Urban centres increasingly have difficulties meeting water needs within their hydrologic basins. To sustain urban water supply, cities and water source regions have increased telecouplings (socio-economic and environmental interactions over distances). To analyse these complex interactions, we apply the new telecoupling framework to the water-stressed megacity of Beijing’s imported water supply. We found that Beijing’s remote water sources have lower risk than local supply, but connections impact the sending systems. The telecoupling framework provides a standard, systematic and flexible tool for evaluating the sustainability of urban water supply. It also identifies a number of research gaps for future quantification efforts.