Modeling Spatial and Temporal Changes in Groundwater Quality in Arid Zones Using Geostatistical Methods(Case Study: Koohpaye- Segzi Plain in Esfahan)

Groundwater resources are as one of the most important water resource in arid and semi- arid areas, thenprotection of their qualityis very important. On the other hand, monitoring andevaluating the groundwaterqualityarecomplex andexpensive, so usinginterpolation methodslooknecessary. Inthisresearch, thespatial and temporalvariationsofwaterqualityparametersinKoohpaye– Segzi Plainof EsfahanincludingEc, TDSandNain theperiods of 1374-1389 werestudied andthe rateand direction ofchanges inwater qualityparametersare specified. First, four the geostatisticalanddeterministic methodsexecutableinArcGIS 9.3, including the Kriging, CoKriging, RBF and IDW, were studied.Then the best of function and equationwere selected for each of the mentionedmethodsand the best method for each parameter in each year of data period based on the lowest value of RMSE. FinallyzoningmapparametersinArcGIS 9.3,was plotted The result obtained are showed that for each year and parameter specific method with function or power have best result and regular trend are not exist in there. But, in years after 1383, Kriging and CoKriging method have best results than other mothods. The resultsshow thatwaterquality inKoohpaye– SegziPlainhavedramaticallyreduced in 1389than in1374.Most ofthechangeshave been occurrednearzayanderood river, as critical points have been appeared in Southern area of this plain. This show the effective role of zayanderood river in groundwater aquifer.