Fuzzy Modelling for Uncertainty Propagation and Risk Quantification in Environmental Water Systems

Risk-based management of environmental systems, like rivers, lakes, groundwater aquifers and coastal areas, is a very useful approach for combating specific problems, like water pollution and loss of ecosystems biodiversity. Uncertainties that could be inherent to natural variabilities in space and time, such as those due to hydrological and climatic variations, together with uncertainties related to human activities or terrorist attacks, may produce various risks and failures affecting both human health and ecosystems integrity. The fuzzy set theory, in combination with mathematical modelling based on partial differential equations, is proposed in this paper, in order to propagate uncertainties in estimating output variables in water quality problems of water systems. Uncertainties in input variables and values of model parameters are first introduced as fuzzy numbers. Then, they are propagated using fuzzy arithmetic. Output variables, like water pollution and environmental risk, are estimated in terms of fuzzy numbers.