In the framework of the national nuclear emergency planning, only the atmospheric dispersion has been taken into account thus far. Nevertheless liquid accidental releases are also possible. Such releases not only have an effect in the short term but also the long term. After an accident actions are needed to protect the people (and environment) inside the influence area, and it is important to know what the status of the resource is (in the case of the Meuse River the quality of the drinking water) and how long it will take before the health risk becomes sufficiently low again. In the specific case of the Meuse, not only the nuclear power plant of Tihange located at the south side of the Meuse River but also other facilities such as Chooz, IRE, Prayon release their radioactive effluents into the river basin. The significant use of Meuse River as a source of drinking water clearly emphasizes the need for the assessment of the possible consequences of the routine and accidental releases in the short and long terms on man and environment. The objective of proposed doctoral research is to develop a reliable mathematical model to be used as a decision support tool (DST) for the assessment of the environmental impact of radioactive effluents and as early warning systems for accidental liquid releases into the Meuse River in Belgium. This model will provide the decision makers with different criteria for a fast diagnosis and pro-active environmental protection design.