The port city of Tianjin is in desperate need of water. The surface and groundwater supplies of this sprawling northeast Chinese metropolis have shrunk to dangerously low levels due to decades of reduced rainfall and overexploitation of the Hai River that flows through the city. According to the Tianjin Environmental Protection Bureau, the city’s per capita water resources are one-twentieth of China’s national average, far below the UN benchmark for a water-stressed region.