Spatio-temporal Variable of groundwater parameters Using Geo-statisticalmethods in Mashhad Plain

Groundwater is the main source of agricultural, drinking and industrial needs, especially in arid and semi-arid regions. The aim of this study was to investigate the relationship between groundwater quality and water level in Mashhad Plain. In this study, qualitative information of 41 underground water piezometer wells for months of feeding and evacuation was investigated in 2001-2015. The GS software and the GIS environment were used to map and Zonation using different interpolation methods. The results showed that the ordinary Kriging method with the lowest RMSe and the highest R2 had the best estimate in the region. The study of the predominant class of groundwater in Mashhad plain was classified as "good" and "moderate" for agricultural use, with Wilcox, C2-S1 and C3-S1 charts for drinking purposes. The results of the review of water quality parameters showed that, other than Mg, the rest of the parameters had incremental changes over the years, and among these parameters, electrical conductivity (EC) and the total dissolved solids (TDS) had a more significant increase, which reduced water quality during this It's been years. The average correlation between the spatial variation of the surface of the stand and the EC is -0.35 and -0.45, which indicates increased salinity by decreasing the aquifer's water level. The results of this research indicate that the main cause of water quality decline in Mashhad plain was the existence of industrial and residential areas and agricultural land development.