THE MINIMUM ENVIRONMENTAL FLOW OF POLLUTED RIVERS IN AREAS LACKING ECOLOGICAL DATA-A CASE STUDY OF A HEAVILY POLLUTED RIVER IN THE UPPER HAI RIVER, CHINA

Environmental flow (e-flow) is the quantity, timing, and quality of water flows required to sustain freshwater and estuarine ecosystems. E-flows are crucial parameters for ecosystem restoration. However, few studies have focused on the e-flows of polluted rivers in areas lacking ecological data, which severely hinder the restoration of aquatic ecosystems. In this paper, taking the natural or near-natural flow regimes as the reference system, the recommended e-flow of the Xinxiang Section of the Wei River (XSWR) in China includes two parts: ecological water and water self-purification demand. The Tennant method was used to calculate the ecological water demand, and a one-dimensional steady-state water quality model (OSWQM) was used to calculate the water self-purification demand. The Tennant method was based on natural flow regimes before runoff mutation, and the water quality indicators in the OSWQM were identified by cluster analysis (CA) and discriminant analysis (DA). The results showed that the Hew Station was markedly short of water, and Liu Station has small amount of water shortage, while the e-flows of the other stations can be satisfied. Some guarantee measures were proposed to improve the ecological status of the studied river and canal. This study provides some methods to determine the minimum e-flow of polluted rivers in areas lacking ecological data considering water quantity and quality, which is beneficial to the protection of river ecosystems.