Watershed ecological risk assessment is an important research subject of watershed eco鄄environmental protection and management, which also uses distinct watershed characteristics compared with regional ecological risk assessment. In this paper, we firstly present the concept and definition of watershed ecological risk assessment based on existing research. The watershed ecological risk assessment is a complicated dynamic process, taking eco鄄spatial pattern formed by physical landform differentiation and hydrological process as evaluation region, in order to assess the possibility and its harmful levels of the negative influence caused by natural hazard, artificial interference as well as some other risk sources on each ecosystem and its components in the watershed. The process of ecological risk assessment has great ambiguity, uncertainty and relativity. Thus, the focal point is to investigate the relationship and ecological risk effects among the water, soil, vegetation, biodiversity as well as human activity in different hydrologic compartments of the whole watershed. Secondly, we analyze its spatial鄄temporal characteristics, heterogeneity, regional correlation and integrity and discuss the research hotspot region at present. Based on the properties, the quantity and the extent of risk sources, ecological receptor and ecological endpoint(defined as the damage to ecological receptor) , we divide the ecological risk assessment into several types. Through an overview of the development and related research about the watershed ecological risk assessment, the main research subjects related to watershed ecological risk assessment are classified into three kinds. The first subject is about ecological risk of freshwater system, which concerns mainly about eco鄄toxicological research of one or more contaminants in different compartments of the hydrologic system. The second subject is about ecological risk of natural disasters in watershed, especially the risks of flood, drought, soil erosion on the ecosystem and its components. The third subject is application of comprehensive evluation model for watershed ecological risks involving multiple receptors and risk
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