Understanding the WEN of megacities has implications not only for more efficient resource utilization but also for synergistic regional development and corporation.

Results of this assessment show that water for local internal energy production and transformation accounts for 220 million m3/year, or 5.6% of its total freshwater use in 2016, and the energy for local water abstraction, supply, and treatment is 3.06 billion kWh, accounting for 1.1% of its total energy consumption for the same year. The external water for “imported” energy is 290 million m3/year, 1.3 times of Beijing’s freshwater use for internal energy.

This means that more water for energy is consumed outside Beijing than within Beijing. The energy for external water is negligible because the bulk of the water transfer into Beijing relies on gravity and because the energy for construction of the transfer infrastructure is not included.

The analysis reveals the contradiction between the two independently conceived policies of Beijing: to meet the “three-red-line” target in the water sector, recycled water and transferred water use will rise, making it more difficult to meet its carbon emission control targets. Therefore, the authors argue that adopting low energy intensity, nature-based water recycling is a wise policy choice.