An Impact Assessment Method of Dam/Sluice on Instream Ecosystem and its Application to the Bengbu Sluice of China

A method is presented for impact evaluation of dams/sluices on their downstream aquatic ecosystems in the absence of detailed long‐sequence ecology ecosystem data. It is based on the analysis of relations between indices of water quality and aquatic organisms. It can be applied to a river section absent of long‐sequence ecology ecosystem data. For this study it was used to evaluate the effects of the Bengbu Sluice (BS), a typical sluice in the Huai River in China. Results indicate that in April and May the impact of BS on different downstream aquatic organisms varied. The most significant impact was on phytoplankton, with 91.7% of phytoplankton indices showing a 100% increase in quantity and biomass. The second most significant was on zooplankton, with 60.0% of zooplankton showing greater increase in quantity and biomass. The least significant impact was on zoobenthos, with only 33.3% showing greater increase in quantity and biomass. Most of these organisms have higher pollution‐resistibility. These findings suggest that the present operation scheme will gradually lead to biodiversity decrease in the downstream aquatic ecology system, which will harm the instream aquatic ecology. Overall, BS has a negative impact on the downstream aquatic ecology system. It is argued that, in order to reduce the negative impact on the downstream aquatic ecology system, the operation of BS needs to be improved so that the discharge into the downstream river course is increased. Data comparison of the aquatic ecosystem condition between 1982 and 2006 also demonstrates the decreasing aquatic ecosystem quality downstream of BS.