Vulnerability of Lahijan-Chaboksar aquifer using comparative assessment of three indices of GALDIT, SINTACS, and AVI

Many countries throughout the world have a large population in coastal areas. Therefore, appropriate water supply in these areas is an important task. The increasing development of human societies has a major contributor to environmental pollution, especially in the water sector. Groundwater vulnerability mapping is used to conserve the quality of groundwater resources. In this study, a comparative evaluation of the vulnerability was performed using three GALDIT, SINTACS and AVI indices to determine vulnerable areas in the Lahijan - Chaboksar coastal aquifer. The GALDIT index offers better results than groundwater vulnerability to the intrusion of seawater in the coastal aquifer, especially in the flat areas, which cannot be identified by SINTACS and AVI. The results of AVI indicate a larger area that is highly vulnerable compared to the SINTACS index, but both methods show high vulnerability of groundwater in Lahijan - Chaboksar aquifer due to pollution from ground surface sources. In general, this aquifer has higher vulnerability to pollution in the coasts and the near zones to the Caspian Sea, particularly at the northern parts of the study area. It is needed to special attentions considered for the aquifer control and protection. The AVI and SINTACS indices can be applied to assess the vulnerability of no coastal aquifers and, in combination with GALDIT, is a useful tool for assessing the vulnerability of groundwater against any pollution at ground surface sources and the intrusion of seawater into the groundwater of coastal aquifers.