Could the hydrological conditions of Lake Baiyangdian support a booming metropolis?

In 2017, the Chinese government announced the development of another metropolis called Xiong'an New Area (XNA) to relieve the population and service pressures affecting Beijing. By the programs of the Chinese governments, the largest natural freshwater wetland of the XNA, Lake Baiyangdian (BYD), will provide the key ecosystem services for the region. However, whether the hydrological conditions of BYD can support this booming metropolis is still unclear. The hydrological condition evolutions and the ecological water demand of BYD in the near future were evaluated. The results showed that to maintain the ecosystem function of BYD and provide ecological services for the XNA, the annual ecological water demands of BYD ranged from 3.10 × 10⁸ m³ to 6.35 × 10⁸ m³ under different water exchange scenarios. Due to the insufficient water resources within the watershed, under the scenario of a 1.0 time year^-1 frequency of lake water exchange, in wet years, normal flow years and dry years 1.32 × 10⁸ m³, 2.10 × 10⁸ m³ and 3.38 × 10⁸ m³ of external water from the Yellow and Yangtze Rivers must be transferred into BYD to satisfy the ecological restoration of the XNA, and the costs may be as much as 77-277 million RMB (11.0-39.57 million USD) per year. The predicted results show that the external water demands may decrease slightly by 0.58 × 10⁸-0.95 × 10⁸ m³ year^-1 and 1.02 × 10⁸-1.19 × 10⁸ m³ year^-1 in the 2030s and 2050s, respectively. Agricultural water consumption reduction, inflow water quality improvement and the intelligent use and management of urban reclaimed water are necessary for maintaining the ecosystem function of BYD, and externally transferred water may be a potential factor needed to support the growing XNA.