Aquifer vulnerability based on classical methods and GIS-based fuzzy optimization method (case study: Chahardoli plain in Kurdistan province, Iran)

The development of an integrated method for assessing the vulnerability of aquifers can be effective in their optimal management and protection. Chahardoli plain is located in the east of Kurdistan province (W. Iran). This plain has productive agricultural lands for its fertile soil. Also, it is constantly at risk of pollution because of agricultural expansion and inappropriate use of the only water source in the region, as well as the use of chemical fertilizers and pesticides. Groundwater pollution at the regional scale is a multifaceted indeterminate procedure. One of the best ways to inhibit groundwater pollution is the identification of areas likely to be polluted. Hence, the modified DRASTIC method was applied to determine the aquifer vulnerability, and the optimal fuzzy logic model was used to develop the DRASTIC method in this study. Then, validation was measured through the nitrate values. In order to study the hydrogeochemical characteristics of groundwater resources in this plain, 18 water samples were collected from designated points in different periods of the 2018–2019 water year. The analysis of water samples was accomplished in the soil and water laboratory of Kurdistan province. The map of aquifer vulnerability to pollution was prepared by distributing it into low, medium, and high vulnerability zones. Moreover, the modified DRASTIC index was calculated between 96 and 159. The correlation index (CI) between the modified DRASTIC index and the nitrate concentration was 41. The intelligent model map used for the application of the fuzzy method is able to enhance the results of the initial DRASTIC method as it revealed better function compared to high-risk areas in this model with high nitrate levels. The final map indicated that the central, northwestern, and eastern regions have the highest level of potential pollution.