Spatial variations of ground water quality in Birjand Plain for agriculture

More than 85 percent of current ground water resources extractions are supplying agriculture water demands in Birjand Plain. Because of the importance of water quality for irrigation, 47 samples collected from piezometric wells in Birjand Plain, to determine ground water quality suitability for agriculture. pH and EC values measured at filed campaign beside laboratory analysis of water samples for major ions concentrations. After chemical analysis of water samples, different geo-statistical models had used to model Cl, HCO3, SAR, pH and EC water qualities parameters. Then the error of each simulation was calculated. Finally, the best method was performed to prepare spatiality maps of Cl, HCO3, SAR, pH and EC parameters in Birjand aquifer based on FAO classification. The interpolation errors assessment highlighted Kriging as the most accurate method for all investigated parameters, in compare to Inverse Distance weighting (IDW) and Radial Basis Functions (RBF). The spatiality maps based on FAO classification show that ground water resources in Birjand plain are not applicable for agriculture due to extremely high values of SAR, Cl, and HCO3, where its usage has limited a little for agriculture by EC and its quality has a suitable range of pH.