Abstract: Assessment on ecological risks of large reservoirs is an important part of eco-environmental
protection and improvement, but few of its studies have been reported. This paper constructs a multi-level
risk receptor or an evaluation index system of multiple risk sources that describes the complicated
relationships and mechanism in ecological risks, on the basis of identifying these sources and receptor of the
valley area of terrestrial ecosystems in a case study of the Nuozhadu reservoir on the Lancang River. We
followed the thoughts of relative risk model (RRM) and developed a multi-level fuzzy model of
comprehensive evaluation to handle the variety of risk evaluation indicators and measures, the difficulties in
quantification of some indicators, and the fuzziness in human cognition of ecological system. Results show
that this model can give a quantitative score of fuzzy evaluation on the ecological risks for each receptor. By
comparative analysis, they provide crucial information to the scheme design of eco-environmental
improvement for the reservoir area. This contributes to gradual slowdown of the negative ecological effect,
further promotion of social, economic, ecological and environmental benefits, and sustainable utilization of
the reservoir area, making beneficial attempts for study on ecological risk assessment of large reservoirs.