The production of a digital precipitation model using the least squares method in the GIS environment (Case Study: Kermanshah Province)

Research Aim: Groundwater is one of the main sources of drinking water, industry and agriculture in arid and semi-arid regions of Iran. Uncontrolled harvesting and entry of contaminating materials into these waters has caused the level of stagnation and the quality of these waters in different areas undergoing changes. Therefore, the knowledge and knowledge about the quantity and quality of these waters and their zoning based on the quantity of their various elements can be effective in making management decisions and reducing the pollution of these resources. The purpose of this study is to compare the definitive interpolation methods and statistical ground for zoning quantitative and qualitative data of Mahidasht plain of Kermanshah province. Research method: In this study, some 40 wells of underground water from 1377 to 1394 were used and qualitative information of 15 underground water wells was used to study the quality parameters including EC, SAR, CL and PH in 1379 and 1394. First, using the Kolmogorov-Smirnov test and Shapiro Wilk test, the normalization of data was investigated. The data were not normal and normalization of quantitative data in 1998 using log method or logarithm and for the normalization of quantitative data in 1394, the distribution method Z was used in SPSS software. In qualitative data other than the sodium absorption quality parameter in 1394, other data had normal distribution. Then GS + software and the GIS environment were used to determine and map the zoning maps using different interpolation methods. Then, quantitative and qualitative parameters were zoned using definitive interpolation methods and ground statistics. Using error estimation criteria, including the mean absolute value of the total deviations, the root mean square error, and the mean error of the bias method, for each quantitative and qualitative parameter in Each period was identified and its zoning map was mapped to the GIS environment. Findings: The results showed that simple and discrete Cokrigingmethods in the quantitative parameter and all the qualitative parameters provide less error. However, statistically, there is no statistically significant difference between the methods that provide the appropriate results. Then, according to the best method in each period, the quantitative parameter changes and qualitative parameters of each period were plotted in the GIS environment. Conclusion:The zoning map of quantitative parameter changes during the studied period (1377-1394) indicated that the groundwater level dropped over a period of 17 years due to the high exploitation, unlawful well drilling and the reduction of rainfall in the plain, and that the northern regions, Northwest, west, and even partly from the center, have fallen more sharply than other parts of the plain.Also, the map of qualitative parameters during the studied period (1379-1394) was also drawn. The results showed that the quality of the parameters in 1394 was insignificant compared to the year 1379, and this increase was indicative of water quality degradation.