Modelling of water pollution in the Thermaikos Gulf with fuzzy parameters

The fuzzy set theory is applied for the definition of the imprecise parameters, which are used in a water pollution model. The physico-chemical coefficients and the loads of pollution sources are expressed in the form of triangular fuzzy numbers. A two-dimensional finite element algorithm, combined with fuzzy logic analysis, is used for the solution of the advection–dispersion equation for ten different water quality variables. The characteristic Galerkin technique was employed for the temporal discretisation, whereas interval operations were conducted for the solution of the algebraic system of equations with fuzzy coefficients. The model was applied for the study of pollution in the Gulf of Thermaikos, located in Northern Greece, for water velocities obtained from a wind-induced circulation model. The concentration distributions of the water quality variables considered are derived in the form of fuzzy numbers, and are presented in relevant diagrams.