By developing an evaluation index system and applying of analytic hierarchy process(AHP)comprehensive evaluation

an ecological risk assess-ment of the ecosystems in the Shitoukoumen Reservoir basin was carried out with considerations of natural conditions and human disturbance of the study area.Based on historical documents and field survey

three factors including point source pollution

non-point source pollution and drought were selected as risk sources.The results show that ecological risks of the basin displayed substantial spatial variability.The key ecological risk sources were total nitrogen and phosphorus in the water

with weight coefficients of 0.2247and0.1945

respectively.The results of this study provided quantitatively a theoretic basis and data support for the environmental management and ecological risk decisionmaking.