Investigation of temporal variation of groundwater salinity potential using AHP-based index

In this study, a Groundwater Salinity Index (GSI) was developed to monitor the salinity potential and water quality of freshwater aquifers adjacent to Lake Tuz, one of the world's hypersaline lakes. The hierarchical structure of the index was designed by using the Analytical Hierarchy Process and eight different parameters that cause groundwater salinity. In addition to the index, a classification system based on GSI scores is proposed that evaluates salinity potential in three different categories as "high," "medium," and "low." In order to evaluate the temporal variation of salinity potential, the GSI was applied to the results of the water chemistry analysis carried out in 2012 and 2019. Prediction maps showing the salinity potential were obtained using GSI scores and the Kriging interpolation process. According to the index scores and maps, it was determined that the salinity potential rose towards the inner parts of the region because of the increasing salinity rate of groundwater as approximately 15%. The fields with the highest salinity potential are concentrated in the western regions along the shore of Lake Tuz. The groundwater closer to the lake has the characteristics of NaCl facies. Due to the mixing of NaCl and CaHCO₃ water facies at various rates, different water types have emerged in the region. Freshwater aquifers located close to Lake Tuz were mainly contaminated by Lake Tuz and the groundwater that has a high salt content as a result of water-rock interaction.