Environmental flow allocation for the Zhangxi River, China

Ningbo city, located in Zhejiang province of China, is a rapidly growing residential and industrial centre, with a current population of 4 million. Its development has required a major water supply expansion programme aimed at providing 400,000 m3 of water per day to Ningbo from the upper reaches of the Zhangxi River by means of a cascade of reservoirs. A loan to support the work was agreed by the World Bank in 2005. Water resources management is achieved through operation of two major reservoirs, Jiaokou (completed in 1980, available storage capacity 75 million m3) and Zhougongzhai (completed in 2006, available storage capacity 93 million m3). Water is released from the reservoirs, via turbines to generate hydropower, to provide for the needs of local industry, irrigated agriculture and public supply along the lower reaches of the River and to maintain the river ecosystem. Surveys of local residents along the Zhangxi River shows that it plays a very important role in the aspects of life, social activity, culture and leisure. Analysis of ecological monitoring data has demonstrated the diverse nature of fish, plants and invertebrates within the river. Some elements of the ecosystem have a high local economic value to local people. However, the River does not have abundant ecological resources. This paper reports environmental flow needed to support key species in the river ecosystem quantified during an initial research project. It recommends a water allocation plan to meet the various water requirements of the ecosystem and local society in addition to Ningbo city.