Systematic solutions and modeling on eco-water and its allocation applied to urban river restoration: case study in Beijing, China

Water and related environmental problems have become a key barrier to the sustainable development of China, where multiple uses of water and urban water management are two significant means to sustain urban development and the ecological restoration of rivers. A new assessment approach and water system model were developed to estimate eco-water or the volume of water essential for maintaining healthy and sustainable urban river ecosystems under various natural landscapes and water quality objectives. Moreover, multiple scenario analysis was adopted to explore the influences of water quality on eco-water management. The Yongding River in Beijing was selected as a case study. The results showed that the eco-water volume was 0.079, 0.073 and 0.067 billion m3/a under high, medium and low objectives without water quality requirements, and 0.112, 0.107 and 0.101 billion m3/a further considering water quality. The water residence times anticipated under each development scenario were 34.8, 37.5 and 41.5 d, which were 13.0%, 14.5% and 13.6% longer than those when water quality was considered. Better water quality could be achieved by implementing water diversions. The comprehensive implementation of water diversion projects could increase the rate of water discharge by 45.1%, decrease the permanganate concentration by 16.1%, and reduce the water residence time by 28.9% on average. This study is expected to provide scientific bases for good water governance, prepare healthy water systems for sustainable communities, and provide a reference case to achieve multiple uses of water for human uses and ecological river restoration in water short areas in developing countries.