Abstract: An index system for the risk assessment of water environment quality of Taihu Lake drainage basin is put forward. According to the measured data of seven sections during 2011-2015, we calculate the attribute importance of each index and select four important indexes together with the eutrophication indicator. Furthermore, in the light of measured water quality data and criterion for water quality classification, we obtain the results of water environment quality risk assessment for Taihu Lake drainage basin by combining Shannon entropy and cloud model under the principle of maximum degree of membership. Results reveal that the water environment quality of the Taihu Lake drainage basin is at medium risk level. Corresponding countermeasures need be taken to reduce the risk of water pollution.The research results offer scientific basis for improving the water quality in the Taihu lake drainage basin.

Key words: Shannon entropy, cloud model, water environment, eutrophication, risk assessment