Estimation of Temporal and Spatial variations of the Level of the Aquifers in Bisotun Plain of Kermanshah Province with Geostatistical Methods

The use of geospatial methods has been considered due to the spatial relationship in various ecological issues. In order to, the present research was done with the aim of investigating the spatial variations of groundwater level in Bistoun plain located in Kermanshah province during the period of 1991-2015 and especially using interpolation estimation methods. In order to, data of groundwater level of the plain including 21 observation wells, collection and database were prepared in Excel software. Then, Different interpolation methods such as Ordinary Kriging, Inverse Distance Weighing with power of 1 to 5 and co Kriging are used to estimate the groundwater level. To evaluate the methods, we are performed the cross validation technique using Root Mean Square Error (RMSE) and Mean Bias Error (MBE). Then, we are prepared spatial zoning maps at the beginning and end of the study period, and finally we were drawn a map of groundwater level isodrop in ArcGIS 10.4.1 software Results of our analysis showed that the Gaussian semivariogram provides the best explanation for the spatial structure of the data. In addition, Kriging is shown as the most suitable method for estimating the groundwater level. The results obtained indicate a decline in groundwater levels in most of the plain. So that the maximum of this decrease is 22 meters in the southwest of the plain (the effective range of wells 9 and 17) and the minimum decrease is 5 meters in the central part of the plain at the 25 years’ period. The main reasons for reducing groundwater levels is being away from the flow of the river and the increasing growth of water-consuming industries in the region.