Evaluation and Modify of Groundwater Quality Monitoring Network of Khanmirza Plain Using Geostatistical Analysis

Because groundwater quality monitoring is very expensive and time consuming, it is necessary to find a method for estimating the hydrochemical variables with the minimum sampling. The aim of this research is to determine the optimal number of sampling wells in Khanmirza plain in Chaharmahal and Bakhtiari. For this purpose, the results of chemical sampling of 19 wells and seven water quality variables including SAR, EC, pH, TH, TDS and the sum of anions and cations for the period 1991 to 2011 were used. At the first, the best geostatistical method for drawing zones for each variable is selected. Then by means of semi-variogram curve the radius of influence of each well is calculated for each variable. According to the amount of radius overlap the minimum number of wells were determined to estimate the average of each variable in the plain. The results showed that to estimate the pH variable one sample well, for the SAR variable 3 sample wells, for the sum of anions and total cations 4 sample wells and for the variables EC, TDS and TH only 5 sampling wells are enough. The results of two-way t-test to validate the results also showed the ability of the proposed wells to properly estimate the studied variables in the plain. Therefore, it can be concluded that in special cases that require necessary and immediate information on groundwater quality in Khanmiza plain, instead of sampling from 19 wells, sampling can be done from a limited number of wells