The effect of geological formations on the quality and quantity of groundwater (case study: Imamzadeh Jafar Gachsaran plain)

Groundwater has a fundamental role and is a key factor in economic development and environmental protection in our country. In recent years, due to droughtinduced rainfall, the extraction of groundwater has increased at a widespread level that could have environmental and geological hazards. Imamzadeh Jafar plain with an area of more than 60 km2 located in the northeast of Gachsaran city has a very good and prone position for agriculture. Abundant use and abandonment of the aquifer by more than 40 wells has led to the criticality of water resources and the loss of static levels, especially during the droughts in this plain. Boolean logic has been used to investigate the impact of watershed geological formations on the quantity and quality of wells. In this study, in order to investigate the spatial relationship between these wells and existing geological formations in the studied watershed, 4 buffers with distances of 1, 3, 5 and 10 km were created around each well. The results of these buffers showed that at 1, 3, and 5 km distances, Quaternary formations (Qft) with an area of 80.82, 47.13, and 35.19 percent had the greatest impact on the water quality of the wells, respectively, while at a distance of 10 km. The impact of the Fars Group formations, especially the Gachsaran Formation (Mgs), had the greatest impact on the water quality with an area of 26.92%.