Spatial modeling of groundwater quality parameters for agricultural consumptions in Azarshahr plain using geostatistical methods

Groundwater is an important source of exploitation in arid and semiarid regions. In the Azarshahr plain, due to the reduction in annual precipitation and lack of surface runoff, groundwater resources play an important role in supplying agricultural, drinking, industrial and domestic water requirements. The aim of this study was to evaluate the quality of groundwater resources in Azarshahr plain for agricultural irrigation and to analyze the EC and SAR variations by using geostatistical methods. So, for spatial mapping of SO4, Cl, TDS, EC and SAR, the observational data from 47 wells in this region, which were measured during the years 2003-2017, were utilized. In order to select the best interpolation method, Kriging approach with Gaussian variogram and IDW methods were used. The obtained results revealed that the Kriging with Gaussian variogram showed the lowest RMSE and the highest NS values. The results of the groundwater quality classification (using Wilcox diagram) and EC/ SAR zoning showed that the groundwater quality in the Azarshahr plain is very saline (C4S1) in most of the cases, which might be linked to the higher amounts of withdrawals from the aquifer.