Introduction

In many parts of Iran, excessive groundwater extraction and insufficient recharge have caused significant declines in groundwater levels. The Shahrekord Plain watershed is among the regions experiencing groundwater depletion and negative water balance conditions. Managed Aquifer Recharge (MAR) is widely recognized as an effective approach for improving groundwater resources. Among MAR techniques, underground dams are particularly suitable for dry regions because they store water below the ground surface, reducing evaporation losses and enhancing groundwater availability. Unlike surface dams, underground dams intercept subsurface flow and increase groundwater storage within alluvial deposits upstream of the dam axis. These structures can improve water security, support agricultural production, and increase resilience to drought. The effectiveness of underground dams strongly depends on appropriate site selection. Hydrological, hydrogeological, geological, geomorphological, environmental, and socio-economic factors must all be considered during the planning process. Geographic Information Systems (GIS) have become valuable tools for integrating spatial datasets and supporting water-resource management decisions. GIS-based approaches enable the simultaneous evaluation of multiple criteria and facilitate the identification of suitable sites. Therefore, this study aimed to identify suitable underground dam axes within the Shahrekord Plain watershed using GIS-based spatial analysis as the first stage of a broader groundwater recharge planning framework.



Materials and Methods

This study was conducted in the Shahrekord Plain watershed, southwestern Iran, where increasing groundwater exploitation and recurrent droughts have intensified the need for sustainable groundwater management. A GIS-based spatial analysis framework was developed to identify suitable locations for underground dam construction. Spatial datasets, including digital elevation models (DEM), topographic maps, drainage networks, geological and hydrogeological maps, land-use data, and groundwater information, were integrated within the GIS environment. In the first stage, drainage channels were extracted and analyzed to identify narrow valley sections capable of intercepting subsurface flow with minimum construction cost. This process identified 51 potential underground dam axes. Subsequently, a series of exclusion criteria was applied to remove unsuitable locations. Areas with reservoir slopes greater than 5%, inappropriate land use (urban areas, exposed bedrock, and infrastructure), and unfavorable geological conditions were excluded. Geological investigations focused on identifying impermeable foundations and stable abutments while eliminating zones with fractured formations or high seepage potential. Environmental and socio-economic constraints were also incorporated by mapping qanat systems and defining protective buffer zones to avoid adverse impacts on existing groundwater resources. Finally, reservoir characteristics, including alluvial thickness, potential storage capacity, and groundwater recharge potential, were evaluated using borehole records and available geophysical data. The integration of these spatial criteria within a GIS framework provided a systematic and reproducible procedure for screening and selecting the most suitable underground dam locations in the study area.



Results and Discussion

The GIS-based screening procedure effectively reduced the number of potential underground dam locations by integrating topographic, geological, hydrogeological, environmental, and socio-economic criteria. From the initial 51 candidate axes identified along drainage channels, only 12 sites satisfied all selection requirements. Topographic analysis excluded areas with reservoir slopes exceeding 5%, while land-use evaluation eliminated urban areas, exposed bedrock, and incompatible land-cover classes. Geological investigations further reduced the candidate sites by removing locations with fractured bedrock, unfavorable lithology, or high seepage potential. Hydrogeological evaluation showed that thicker alluvial deposits and higher groundwater storage capacity significantly improved site suitability by increasing recharge potential and subsurface water storage. Incorporating qanat protection buffers ensured that selected sites would not adversely affect traditional groundwater systems or downstream water users, thereby improving the environmental and social sustainability of the proposed framework. The final 12 locations exhibited favorable reservoir geometry, suitable impermeable foundations, adequate alluvial thickness, low leakage risk, and minimal conflicts with existing infrastructure. These findings demonstrate that GIS-based multi-criteria evaluation provides a reliable and reproducible approach for identifying suitable underground dam sites while substantially reducing the need for costly field investigations. The results also confirm that successful underground dam planning requires the simultaneous consideration of hydrogeological, geological, environmental, and socio-economic factors rather than relying solely on engineering criteria. Overall, the proposed methodology offers an effective decision-support framework for sustainable groundwater management in semi-arid regions.



Conclusion

This study applied a GIS-based spatial analysis framework to identify suitable underground dam axes within the Shahrekord Plain watershed. By integrating topographic, geological, hydrogeological, land-use, environmental, and socio-economic criteria, the methodology successfully reduced 51 preliminary candidate sites to 12 suitable locations. The results confirm that GIS is a reliable and efficient tool for underground dam site selection and can significantly improve decision-making in groundwater recharge projects. Geological suitability, leakage potential, reservoir slope, alluvial thickness, and protection of existing qanat systems were identified as the most important factors influencing site suitability. The selected sites provide promising opportunities for enhancing groundwater storage, increasing drought resilience, and supporting sustainable water-resource management in the Shahrekord Plain watershed. As the first phase of a broader research program, this study establishes a foundation for future investigations involving multi-criteria ranking, engineering feasibility analysis, economic evaluation, and detailed hydrogeological modeling of the selected underground dam sites.