Qualitative zoning of groundwater to assessment suitable drinking water using fuzzy logic spatial modelling via GIS

Due to shortage of surface water, resources of ground water in Iran (like many other countries with dry and semi-dry weather) have turned into the most important and reliable source for water supply. Thus, it is necessary to consider the quality of this resource for drinking purposes. The aim of this study was to assessment suitable drinking water based on a fuzzy approach in Asalem region, Iran. For reduce the uncertainty, fuzzy logic spatial modelling via GIS was applied. To receive these aims, four stages were performed. In stage 1, we calculate the values of eighteen conventional and effective factors used for drinking water quality classification upon analysing the statistical quality data regarding various ions existing in 15 sample wells dug in 2015. In stage 2, interpolate these factors by kriging method via ArcGIS software. In stage 3, parameter standardization with fuzzy membership function were done. And in stage 4, for Aggregation factors, several fuzzy overlay operations were used. Finally, to identify the best operation, the 'Optimum Index Factor' was used. Results showed that the 'GAMMA 0.9' with highest OIF in most of the factors, is the best overly operation in our study area. According to classified the best operation map, 1.42% of understudied regions are classified in very poor class, 12.48% is grouped in poor class, 78.55% is grouped in fair class, 7.53% is classified in good group and 0.01% is classified as excellent group. In this regard only central parts of the study area have 'fair' to 'good' and 'excellent' groundwater quality for drinking water and in other parts, the quality is within 'very poor' and 'poor' to 'fair'.