ABSTRACT
Fuzzy logic, an appropriate classification method to classify water chemistry samples into similar groups, is an efficient tool for describing hydro-geological environments. Geological and hydro-chemical systems, in some cases, are too complex to be analyzed by conventional graphics and statistical methods. Chemical and physical characteristic in the natural cycle of change, are often continuous and not abrupt, or, in other words, physiochemical processes do not always have separate outlets. Because of this continuity, statistical groups may not be well separated from each other and instead, they may form a sequence in which different groups may overlap. In these circumstances, fuzzy logic can be useful for modeling and grouping. In this study, 30 samples of Urmia plain underground water have been divided in three groups, using fuzzy segmentation, and then these groups have been studied for concentration of total solutes and their types. The concentration of ions dissolved in the underground water, is increased from the first group to the third group. In the first and second groups, the water type is ChloroSodic and in the third group it is calcic sulphate. In order to identify the geochemical processes governing the water table, chart combination, ion ratios and saturation indices of calcite, dolomite and gypsum samples has been evaluated. Results showed that the chemical composition of underground water supply is strongly influenced by the river feeding, sediments forming the groundwater table and surface evaporation of aquifer.
