The effect of geomorphic and anthropogenic factors on the karst spring occurrence (case studies of central Zagros Mountain Range, Iran)

Abstract

Karst groundwaters are vulnerable and essential resources that require comprehensive management for protection and preservation. For this purpose, awareness of effective factors are required for the development of karst water resources and their quality management. Identifying the spatial distribution of springs in karst settings is important for a better understanding of groundwater flow because springs are the terminal sites of karst flow networks which are understudied. This study aims to identify the location of karst spring occurrence with an emphasis on geomorphic factors using the Analytical Hierarchy Process (AHP) and Logistic Regression (LR) model. As the case studies in this research, the Lordegan and Shahrekord karst basins located in Iran’s Zagros Mountains were selected. Nine factors influencing spring occurrence are considered and classified into four major groups: geological layer (lithology and distance from fault), hydrology layer (distance from river and drainage density), geomorphological layer (slope, aspect, elevation, and plan curvature), and anthropogenic layer (land use/land cover). The potential map of karst groundwater spring weighed by AHP was classified into five classes (very low, low, moderate, high, and very high) and both basins were in very high to moderate class. The geological layer (i.e., lithology and distance from faults) was the most significant geomorphological factor in the Lordegan basin, with the weight of 56.3%, whereas the topographical layer (i.e., slope, aspect, elevation, and curvature) was in the Shahrekord basin, with the weight of 38.4%. Due to the high-altitude of the studied basins (1944 to 3297 m), the land use/land cover layer had the lowest weight. According to the AHP results, 76.9% of the springs in the Lordegan basin and 60% in the Shahrekord basin are in the very high class spring groundwater potential zone. The LR model was also used to simulate the appearance of springs. The Relative Operating Characteristics (ROC) of the LR model in the Lordegan and Shahrekord basins were 0.9 and 0.85, respectively. Also, the LR results show that 38.4% of the springs in the Lordegan basin and 60% of the springs in the Shahrekord basin are in the very high class spring groundwater potential zone.