Investigating Spatio-Temporal Variations of Groundwater Quality of Guilan Province using Geostatistical Method

Knowledge and awareness of temporal and spatial changes of quality parameters, especially salinity in groundwater and surface water resources and the preparation of zoning maps can be an important step in proper management and planning in the use of water resources. In this research, the trend of spatial and temporal changes of some groundwater quality parameters in Guilan province has been evaluated. Measurement data of some cations and anions sampled from 150 wells in September and March of 2011-2018 and water level data of 282 piezometric wells were collected. The zoning maps obtained by ordinary kriging method were examined. These maps show that in terms of quality parameters, groundwater resources in the central part of Gilan province have higher values ​​and in the growing season due to agricultural activities and fertilization, groundwater quality decreases. Effect of groundwater depth on the concentration of the parameters was assessed. According to the map of groundwater depth changes, the largest area of ​​Gilan province has a water level of 0.23 to 5.5 m. The results of classification of qualitative parameters show that in shallow groundwater depths the concentration of qualitative parameters increases.