Document Type : Research Paper
Author
Assistant Professor, Soil Conservation and Watershed Management Research Institute, Agricultural Research, Education and Extension Organization (AREEO), Tehran, Iran
Abstract
Introduction
Water collection and storage with minimal losses are among the most effective measures for water resource development in dry and semi-arid regions. Underground dam technology is a suitable solution for managing water resources in such areas. These subterranean structures influence hydraulic flow in porous environments and are constructed to block, divert, or reduce groundwater movement. Underground dams serve various purposes, including water resource control, management, protection, and development. The success and sustainability of these structures largely depend on selecting the most appropriate location, considering project goals, operational efficiency, and intended use. One of the primary reasons for failure in dam projects is the lack of comprehensive studies on site selection.
Materials and methods
The study area is located in the western sub-basins of Semnan Province, geographically positioned between 53°15' to 54°20' East longitude and 35°20' to 36° North latitude. Geologically, it lies within the Alborz and Central Iran zones. The basin spans 104.91 square kilometers, with elevations ranging from 1,643 meters to 1,413 meters. The region has a semi-arid Mediterranean climate, receiving approximately 100 millimeters of annual rainfall. The current geomorphology and topography of the basin are shaped by geological structures, rock types, and erosion susceptibility. Due to the mountainous terrain, the area lacks significant alluvial groundwater aquifers, with water resources being limited to subsurface flow in alluvial deposits along streambeds or within hard rock formations. Consequently, underground dams present a viable solution for water supply in such conditions. This study assesses the feasibility of constructing underground dams in the western sub-basins of Semnan Province using a hierarchical analysis approach within a Geographic Information System (GIS). Relevant resources were reviewed to determine the essential criteria and conditions for selecting suitable locations for underground dam construction. Informational layers were generated and integrated in a GIS environment, employing a hierarchical approach to facilitate decision-making.
Results and discussion
Controlling and blocking subsurface flows in alluvial deposits of streambeds through underground dams can create reservoirs within the porous environment, enhancing water resource development. This strategy is particularly relevant for dry and semi-arid regions, including the northwestern and western sub-basins of Semnan Province. To identify suitable locations for these structures, key factors such as geology, hydrology, water resources, topography, and stream geometry were analyzed. Areas that failed to meet the required standards were deemed unsuitable and excluded from consideration. Most of the necessary criteria were derived from satellite imagery, topographic and geological maps, and expert knowledge. The site selection criteria were classified into two groups: absolute criteria and decision-making criteria. Absolute criteria provided a binary assessment (favorable/unfavorable), whereas decision-making criteria were prioritized within a suitability range, from highly suitable to relatively suitable. These factors were incorporated into the site selection process using a hierarchical methodology in GIS. The application of GIS tools for overlay analysis, function execution, and weighted scoring significantly improved the speed, accuracy, and efficiency of the process.
Conclusion
The findings indicate that using a step-by-step hierarchical methodology within modern techniques, such as GIS, enhances the accuracy and efficiency of regional-scale site selection studies. This approach improves reliability by refining criteria determination, weighting, and scoring. The hierarchical methodology systematically eliminates unsuitable areas, progressively narrowing the study region to the most viable locations. The results showed that approximately 20% of the streambeds in the western sub-basins of Semnan Province have the potential for underground dam construction, providing effective water storage and management solutions. The most suitable locations are found in streambeds of categories 4 and 5, particularly on sandstone, limestone, and marl formations.
Keywords
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