A REVIEW OF RIVER HABITAT ASSESSMENTS AND APPLICATIONS

River habitat is the integration of physical, chemical, and biological conditions that river organisms rely on, and is an important part of river ecosystems. Assessments of river habitat can help understand river ecological health condition, identify causes of habitat degradation, and provide clues and solutions for river ecological restorations. We reviewed river habitat assessment methods and applications from the global literature pool that published between the 1980s and 2018. According to their focuses and objectives, these methods were divided into two types: predictive model and multi-variable assessment method. We then compared advantages and disadvantages of these methods. The predictive model method is suitable for monitoring long-term habitat dynamics, but it needs to take natural undisturbed rivers as a reference and requires a large amount of historical data. This method is not easy to be developed and applied in a nationwide scale. The multi-variable assessment method is rapid and convenient, but its evaluating process is relatively complex and the evaluation criteria are different by regions, so the findings may have some limitations. We also summarized and classified these methods into the ones suitable for small and medium wadeable streams and the ones suitable for large non-wadeable rivers where the latter is less developed. Most of the current river habitat assessment applications in Chinese rivers are developed and modified from one or two most commonly used ones in other countries. Moreover, those applications and modifications are individual river-based, and the habitat conditions of these river basins have not been well studied. Thus, we suggest the following approaches to further develop habitat assessment methods for Chinese rivers to reach sustainable river basin management: (1) determine more scientific and standardized scoring indicators and meet the characteristics of different rivers according to their local conditions; (2) expand the scope of assessments, conduct habitat monitoring from watershed and landscape scale, and pay attention to the health status of the whole river basin; (3) expand the time scale, establish models and conduct long-term dynamic evaluations; and (4) encourage the government to initiate large scale planning and collaborations among management agencies, and to integrate region-based habitat data and establish the nationwide river habitat mega database.