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Isfahan province

Continuous decline of groundwater quality for agricultural purposes has become a major concern in extensive arid and semi-arid regions; therefore, mapping the quality of groundwater in a broad scale is an essential step in land management. This study aimed to map spatial distribution of two importantant groundwater quality indices including EC and SAR in Isfahan province, Iran, using geostatistical techniques. Different techniques such as Kriging, IDW and RBF were applied to water quality data of 540 groundwater wells to map contimuous variations of the EC and SAR indices in ArcGIS 9.3 environment. Among the interpolation methods, the kriging by circular variogram model performed best and had the lowest RMSe error. Therefore, the produced maps from this technique were classified based on Wilcox method. Results showed that the EC varies across the province from 392.2 in the west to about 17917.6 µmmhos/ cm in the northwest and eastern parts of the study area. The highest and lowest SAR values were estimated in the towns of Khoorobiabanak and Semirom, ranging from 38.9 to 0.13, respectively. According to the map of irrigatiojn water quality based on Wilcox method about 12.13 % of the region has been classified as good, 16% as moderate, 17.5% as unsuitable and 54.35% as unusable category. In general, the quality of groundwater in the Isfahan province decreases from west to east and also from south to north especially in playas (non-agrultural lands) where the unsuable class is dominated.