In the cluster project "Risk Assessment of New Chemical Substances methods are developed to systematically predict and assess the hazards for man and environment. After the basic screening of a substance has been carried out, a more extensive study can be performed using models adhered to the problem. In the project "Water Quality Models" the applicability of the Exposure Analysis Modelling System II (EXAMS II) has been tested and verified by the construction of an extensive model of the IJssel branch of the Rhine Delta. It can be concluded that the EXAMS II modelling environment is suitable as an advanced water quality model in the risk assessment system.<br>