Comprehensive Environmental Flows Assessment for Multi-Guilds in the Riparian Habitats of the Yangtze River

The development of new strategies for the operation of existing dams is essential for restoring ecosystems that have already been affected by the construction and current regulation of these dams. The assessment of environmental flows (EFs) is significant in guiding such strategic dam operations. However, most of the existing methods just focus on one species or guild without simultaneously considering the interactions with other aquatic organisms. This study proposes an innovative method to determine comprehensive environmental flows (CEFs) for multi-guilds (fish, macroinvertebrates, and hygrophytes) based on the habitat simulation model. We focused on the riparian habitats in the middle reaches of the Yangtze River, coupled the biological preferences of multi-guilds with suitable habitat factors, including velocity, depth, and substrate, and then analyzed the relationships of flow and weighted usable areas to determine the CEFs for multi-guilds. The results showed that while the optimal CEFs could be satisfied only in Spring and Summer, the threshold CEF conditions could be met in the Jianli reach throughout the year after the impoundment of Three Gorges Dam (TGD). The results obtained by using the CEFs assessment could better satisfy the EFs for multi-guilds than the ones developed for individual species. The CEFs could be also used to evaluate the impact of TGD on multi-guilds' habitats and optimize ecologically-friendly operations in already designed dams. This study is helpful for maintaining ecosystem integrity in Yangtze River and provides a good example for use in other dams facing similar issues.