imulating spatial changes in groundwater qualitative factors using geostatistical methods (case study: tehran - karaj plain)

changes in groundwater quality, is caused destruction of other resources, either directly or indirectly, due to bad management of groundwater extractions. considering the importance of groundwater resources, especially in arid and semiarid regions, this research was done to modeling the spatial distribution of some groundwater qualitative factors with emphasis on drinking using geostatistical methods. qualitative variables selected are: total hardness, chloride, sulfate and nitrate ions. first of all, normality of data investigated based on kolmogrov-smirnov test and non-normal variables were transformed to normal by using logarithmic transform. then variography and cross-variogram analysis of variables was done. accuracy assessment of results was investigated based on cross validation and root mean square error (rmse). results showed that cokriging method (using auxiliary variables) compared with other geostatistical methods is a more accurate estimator, so interpolating and zoning of variables were done by using cokriging method and drinking water standards.