Qualitative Zoning of Groundwater Resources Using Geostatistical and GIS Methods (Case Study: Soleymanshah Watershed)

In many regions especially dry areas such as Iran, groundwater resources are the main sources to provide the needed drinking and agricultural water. Agricultural activities and excessive use of the chemical pesticides are the important sources which decrease the groundwater quality. Therefore, in this research, using Geostatistical methods including Kriging and weighted Inverse Distance the spatial distribution of TDS, SAR, chloride and nitrate amounts of groundwater were evaluated in the Kermanshah- Soleymanshah watershed. To this regard, Parameters values of groundwater of 60 wells in watershed were sampled. To analyze the spatial distribution of the groundwater quality the Geostatistical software ArcGIS version 10 was used. The performance criteria for evaluating the used methods were Mean Error (ME) and Root Mean Square Error (RMSE) along with the Cross Validation method. RSS index was used to select the appropriate model. The results showed that the ordinary Kriging was the best method to estimate the qualitative parameters of the groundwater. Finally, the map of the spatial distribution parameter’s amounts was provided based on the best method