Abstract: In order to comprehensively and objectively reflect the impacts of human disturbances on river ecosystems, various countries and regions have set up a series of river health assessment methods based on the ecological responses of fish, diatom, and macroinvertebrates to the human disturbances. Among these assessment methods, the methods based on fish still pay attention to the application and perfection of the index of biotic integrity, those based on diatom have a wider application, and the methods based on macroinvertebrates are still at the leading place. As for the construction of indicator systems, in addition to the evaluation at the levels of community structure and function, the evaluation based on biological taxonomy (family, genera and species) is made. At present, the multivariate assessments of the ecological responses of aquatic organisms to human disturbances are the most common assessment methods, but the methods tend to lack consideration of information redundancy among the various indicators. The longterm use of the indicator systems should be further studied.

Key words: extreme climatic events, break trend analysis, temporal and spatial variations, climate change, Songnen Grassland.