Excessive use of groundwater aquifers may result in low quality groundwater. The chloride content and the sodium adsorption ratio (SAR) are among the most important water quality parameters, that is, the estimation of these two parameters and, consequently, Na⁺, Ca²⁺ and Mg²⁺ concentration are much more time-consuming and expensive than water salinity measurement. Thus, it seems necessary to find a guideline to estimate SAR and chloride using salinity extent. For this purpose, geostatistic (cokriging and kriging) methods can be very helpful. In this study, the chloride content and SAR of groundwater in Boukan area were determined by irrigation water salinity (ECw) and the two kriging and cokriging methods were applied. The comparison of the obtained results indicated that for the estimation of both parameters of SAR and Cl, the cokriging method was more accurate than kriging method. However, they differ slightly and, in general, the two methods have suitable accuracy to estimate SAR and Cl- based on water salinity parameter.

Key words: Sodium adsorption ratio, chloride, geostatistic methods, groundwater.