Study of Water Environmental Cumulative Risk Assessment Based on Control Unit and Management Platform Application in Plain River Network

As the gradual deterioration of the environment, the method of environmental risk assessment has been developed from basing only on a single source to basing on a cumulative risk source. In accordance with the water environment features of the plain river network area, a cumulative risk assessment system of water environment in the plain river network area was established in this paper, the design process for which could be divided into three step: (1) Control unit divided reasonably was chosen as the basic unit for water quality management. (2) On that basis, according to the characteristics of the plain river network area, the cumulative risk indexes were selected. The index weight is calculated using entropy method and analytic hierarchy process (AHP), which could determine the risk grade of each control unit. (3) The cumulative risk assessment method is coupled to the existing water environment management platform. The platform with a dynamic database can realize the dynamic calculation and visualization of the cumulative risk grade. In this paper, the Zhejiang area of Taihu Basin was selected to be the research target as the typical plain river network area. Thirty-five control units were divided with regional water environment and control section. Taking the data in the year 2011 as example, the proposed cumulative risk assessment method was used to identify the control units in different grades and the results demonstrated that the numbers of high-, medium-, low-and extremely low-risk control units are 13, 12, 5 and 5, respectively. It is necessary to give priority to the high-risk control unit. Therefore, the cumulative risk assessment method based on the control unit provides an essential theoretical basis for reducing the probability of water pollution and reducing the degree of water pollution damage.