Application of river habitat diversity to assess river ecological flow-a case study of wu river

Methods to assess the ecological flow in streams can be categorized into the historical flow methods, the hydraulic methods, the habitat methods, and other rules of thumb. However, due to the different characteristics of each stream, it is difficult to set a standard in assessing the ecological flow. The habitat methods are most preferred in developed countries since they provide quantitative indicators. In Taiwan, however, the habitat suitability index (HSI) of target species has not been fully established, and thus the application of habitat methods in assessing ecological flow is hindered. In this study, we use the positive relationship between habitat diversity and the Weighted Usable Area (WUA) to assess the ecological flow. The proposed method takes the biological habitat requirements into consideration while using a simpler calculation process than the habitat methods. In cases which lack for a complete HSI system, this new approach can particularly function as a preliminary assessment for ecological flow in streams.