Investigation of Spatio-Temporal Variation in Groundwater Resource Quality using Geo-Statistical Methods (Case Study: Lordegan Plain, Chaharmahal and Bakhteyari Province)

Groundwater resources are considered as the most important sources of drinking water, agriculture and industry. investigation of quality changes and decreases is necessary in groundwater level due to excessive exploitation of these resources.In this research, investigated the spatiotemporal variations of groundwater quality parameters for drinking and agriculture in 18 wells during the statistical period of 1991-2015 in Lordegan plain of Chaharmahal and Bakhteyari province.The studied parameters were including Cl-, TH, TDS, Na+, SO4-2, SAR and EC. In order to estimating the semivariance model and determining the best interpolation method used the GS+ 5.1.1 software and RMSE and MBE criteria. Finally, spatial variation of parameters was calculated using IDW method in ArcGIS10.3 and parameters variations trend investigated using nonparametric Man-Kendall test in MAKESENS 1.0 software. The results showed that the TDS and TH parameter is better condition in plain than Cl-, Na+ and SO4-2 Also; in agricultural aspect the SAR and EC parameters have a very good condition during the statistical period in this plain. Trend analysis results showed that the TDS, TH, EC, SO4-2 and Cl- parameters have positive and SAR and Na+ have descended trend.