Effects of long-term environmental flow releases on the restoration and preservation of Baiyangdian Lake,a regulated Chinese freshwater lake

Environmental flow releases provide the water regime required to maintain the aquatic ecosystem health, which are subject to intensive human disturbance. We used decades of data to determine whether the long-term use of flow releases had successfully restored China’s Baiyangdian Lake ecosystem. We used fuzzy-logic inference and field data to compare the water level regime, water quality, and ecological variables before and after the releases. Critical components of the water level regime, including the annual mean, the 7-day low, and the 30-day low and high water levels, differed significantly before and after the releases. The releases slightly improved water quality compared with the pre-1997 level, except in 2003. The reed area and fish yield have been greatly increased by these flows since 1997, but changes in the reed yield and fish species were not significant. We discuss the advantages and drawbacks of the current environmental flow releases for Baiyangdian Lake, and propose that the release patterns have adversely affected the lake’s natural level regime from an ecological perspective. Therefore, we suggest that accounting for recent research on environmental flows, including the implementation of adaptive management, will be required to implement more sustainable and ecologically effective releases of environmental flows.