Investigation and Potential Identification of Karsts as Groundwater Resources with the Help of GIS Studies, a Case Study of Western Iran

Abstract

Improper use of alluvial aquifers and declining water levels in these aquifers have led to significant attention to the search for other groundwater sources in karst areas and hard formations. Iran is one of the countries that has a very high percentage of karst in the world and the study and tracing of karst are very important in this country. In this research, eight effective factors in karstification are identified and categorized into two groups and the relevant information layers are prepared. The first group includes average annual rainfall, type of geological formations, the density of fractures, and density of the fracture site. The second group, which is of secondary importance, includes the average annual temperature, the density of canals, slope, and type of vegetation. After preparing the information layers, quantitative parameters based on fuzzy logic and qualitative parameters were standardized by the rasterization method. The importance and weight of each of the effective factors were determined from two methods viz. Analytic Hierarchy Process (AHP) and the Fuzzy Hierarchical Analysis Process (FAHP). After multiplying the standard maps with their respective weights, they were overlaid, and finally, karst potential maps were generated. Maps were generated from the two weighting methods based on the subsurface and surface hydrogeological-geomorphological diagrams. Karst features such as Karen, dissolution cavities, depressions, caves, dry valleys, reservoir rocks of springs and water exploitation wells, and Calcareous limbs were ascertained, which indicates that the results of the FAHP method are more consistent with the existing conditions in the region. The final map was divided into five classes in terms of the karst potential, viz. very high, high, medium, low, and no potential.