The Research Group of System Ecology and Watershed Ecology at Institute of Hydrobiology, Chinese Academy of Sciences (IHB) (Principal Investigator: Prof. CAI Qinghua) recently established a set of biological integrity index based on benthic diatom (D-IBI) to evaluate the impact of the development of small hydropower on river ecosystem. The index includes four diatom parameters which can effectively distinguish the habitat condition of the reference and damaged sample points.  

The results of their study show that: the healthy condition of the impacted points is significantly lower than the reference point and the points downstream from the dam are the most seriously damaged; With the recovery of the flow, the damaged points are gradually improving. A management idea "evaluation-management-verification", proposed by Prof. Cai’s research group, puts the minimum instream environmental flow, which is obtained from theory, into practice. The research group uses the evaluation index to prove the effectiveness, thus determining the appropriate minimum instream environmental flow, and minimizing the impact of small hydropower on river ecosystem.  

Monitoring 23 small hydropower stations located in the Xiangxi River watershed, Prof. Cai’s research group has earlier observed that the development of cascade run-of-river dams had significant influence on benthic diatom community by using the model which is established by the relationship between diatoms and environmental factors on the reference points to predict the species richness of diatoms on damaged points (Aquatic Sciences, 2010, 72:117-125). They also studied the impact of constructing a typical small hydropower station on Xiangxi River on benthic algae community. They found that, 2-3 years after the small hydropower was built up, the benthic algae community had significantly changed (Journal of the North American Benthological Society, 2009, 28 (1) : 69-79). 

The research is one of the long-term monitoring works of the three gorges reservoir-Xiangxi River Ecosystem Lab of the Chinese academy of sciences/China Yangtze Three Gorges Group Company. It was funded by the key program of the National Natural Science Foundation of China “the study on the damage of the small hydropower group on river ecosystem and the recovery mechanism – a case study in Xiangxi river”(30330140).  

The research finding was published online in the journal Ecological Indicators (Development and evaluation of a diatom-based index of biotic integrity (D-IBI) for rivers impacted by run-of-river dams” (doi:10.1016/j.ecolind.2011.10.013). It was mainly completed by IHB’s graduate student WU Naicheng et al.