Extended Abstract
Introduction: Severe rainfall reduction, rising temperatures, and excessive exploitation of surface and groundwater resources—especially in arid regions of Iran—have turned water scarcity into one of the country’s major challenges. Among available water sources, karst aquifers play a crucial role in meeting water demands due to their unique geological characteristics. These aquifers, with their fractures, joints, and secondary porosity, offer high storage and transmission capacities. Moreover, the limestone composition of these formations often ensures suitable water quality for drinking and agricultural uses. Approximately 11% of Iran’s surface area—particularly in the Zagros highlands—is composed of karstic formations. This underscores the necessity of proper evaluation, and sustainable exploitation of karst water resources. The Semirom region in southern Isfahan Province is considered a promising area for developing karstic water sources but has faced declining water tables and drinking water resources in recent years. The present study investigates the potential of groundwater resources in the Garmook area of Semirom County and identifies suitable locations for drilling wells and exploiting karst aquifers.
Materials and Methods: In this study, the geological structure of the region was first examined using existing geological maps, satellite imagery, and field surveys. The study area mainly includes zones developed in the Asmari and Shahbazan formations. Due to their hydraulic connectivity, these two formations were analyzed as a single hydrogeological unit. Data on precipitation, air temperature, topographic slope, vegetation cover, and soil characteristics were used to assess infiltration potential. The water balance method was then used to estimate inputs and outputs for each karstic zone. Inputs included effective precipitation, subsurface recharge from adjacent areas, and surface flows, while outputs comprised spring discharge, abstraction from wells, qanats, evapotranspiration from the epikarst zone, and subsurface discharge to adjacent plains. To delineate the recharge basins of the springs, empirical relationships were applied, considering mean annual precipitation, spring discharge, and infiltration rates. Additionally, water samples were collected from the identified sources, and the quality was assessed using laboratory results and plotted on Wilcox and Scholler diagrams.
Results and Discussion: Geological investigations of the region revealed that the widespread presence of carbonate formations—particularly the Asmari Formation—in the Garmook area has created favorable conditions for karst development and the formation of high-capacity aquifers. The presence of active faults, such as the Narmeh Fault and its subsidiary branches, not only increases fracturing and jointing in the rock mass but also facilitates the infiltration of rainwater into the limestone bodies, thereby enhancing the recharge of karst aquifers.
In this region, multiple water sources—including Khansar Spring, Khan-Ali Spring, Jaq-Jaq Spring, Semirom Waterfall, and several extraction wells within the Garmook area—have been identified, with a total discharge estimated at over 435 liters per second. This corresponds to approximately 13.7 million cubic meters per year, indicating the high yield potential of the area. In particular, the electrical conductivity of the regional waters is less than 450 µS/cm, further confirming their suitability for potable and irrigation use. On the other hand, results showed that in certain parts of the region (such as west of Narmeh), the infiltration rate decreases to about 30% due to the presence of thick soil cover and dense vegetation. However, in other parts—where karst development is more pronounced and open fractures and joints are prevalent—the infiltration rate can reach up to 50%. Water balance studies also indicated that part of the groundwater exits the area through transverse and longitudinal faults, flowing toward adjacent plains or distant springs such as Sandegan.
Conclusion: Based on the conducted analyses, the Garmook area possesses adequate capacity to supply drinking and irrigation water in the short and medium term. Considering the geological context, the positive groundwater balance, and acceptable water quality, four locations were proposed for drilling new wells. These points are situated in areas with high recharge probability, good permeability, and suitable discharge rates. Additionally, to better understand the aquifer’s hydrodynamic behavior, the installation of piezometers and implementation of water-level monitoring programs are recommended. Given the significant influence of regional faults on groundwater flow directions, further studies—including dye and isotope tracing—are essential for determining the precise flow paths to improve groundwater resource management. The findings of this study can serve as a foundation for water resource management in southern Isfahan Province and other similar regions.