Analyzing the Spatial Variations of Groundwater Salinity and Alkalinity in Isfahan Province Using Geostatistics

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 on a broad scale is an essential step in land management. This study aimed to map spatial distribution of two important 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 continuous variations of the EC and SAR indices in Arc GIS 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 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 Khour va Biabanak and Semirom، ranging from 38. 9 to 0. 13، respectively. According to the map of irrigation water quality based on Wilcox method، about 12. 13 % of the region was classified as good، 16% as moderate، 17. 5% as unsuitable and 54. 35% as unusable category. In general، the quality of groundwater in Isfahan province decreases from west to east and also from south to north، especially in playas (non-agricultural lands) where the unusable class is dominant.