Application of Geostatistical Techniques for Assessment of Groundwater Quality Foumanat Gilan

Groundwater is considered to be the main source of drinking and agricultural purposes. Therefore, it is essential to be aware of its quality for the proper management of water resources. In this study, qualitative data of 42 observation wells of years(2004-2013) were used to determine the best method for analyzing spatial interpolation quality of the ground water to be used for agricultural purposes. No significant difference of empirical relationship between TDS and EC with respect to the global relationship were observed in the study area. It is also found that, SAR in area was also affected by the concentration of Na. Water quality is classified according to Wilcox was in the category of slightly saline. A comparative analysis between geostatistical methods (Kriging, Cokriging and Inverse distance weighted) showed that the algorithm averages with RMSE and MAE amount are 9.655 to 6.755 and R2 value of 0.6 better results in the estimation of qualitative parameters in the study area. The spatial variations maps of EC and SAR were analyzed for the period of 5 years (2004-2008 and 2008-2013) it is found that the concentrations in the East more than in the West and the lowland plains has been in the trend of increasing concentrations. Also the borders lines of Western and Southwestern parts of Plain are considered to be area, where in terms of lesser concentration of EC and SAR.