Nationwide sub-surface dam site selection in Iran: A multi-criteria decision support framework for water security in arid regions.

Subsurface dams (SSDs) offer a promising solution for reducing water loss through evaporation and pollution while recharging depleted aquifers. However, the extensive data requirements for SSD site selection often limit regional-scale studies. As a result, comprehensive nation-level assessments remain limited, leaving decision-makers without sufficient guidance on SSD implementation aligned with national priorities for securing water resources for both people and the environment. This study addresses this gap by analyzing extensive, large-scale datasets using the analytic hierarchy process (AHP) to identify suitable locations for SSD implementation across Iran, a water-stressed country situated in the world's (semi)arid belt. We employed an GIS-AHP weighting framework that incorporates multiple nested sensitivity analyses and aggregates the proportional representation of suitability index values across provinces at the national scale. This integrated approach provides a systematic basis for ranking provinces according to their overall suitability for SSD implementation. The identified potentially suitable areas were validated (i) using 182 randomly selected locations distributed across the country's provinces, verified through Google Earth imagery analysis, and (ii) comparing with the existing hydrogeological data for seven high-scoring locations. Our results identified Bushehr province as the most suitable and Ardabil province as the least suitable for SSD implementation in Iran. Overall, the findings revealed that western, southwestern, and southern regions offer more favorable conditions for SSD implementation compared to eastern, northwestern, and central regions. Among the factors examined, precipitation, permeability, and groundwater depth were the primary contributors to SSD site selection. The results emphasize the important role of considering multiple environmental factors in combination when selecting SSD sites, an approach that enhances the accuracy of regional-scale SSD site selection for decision-makers. Our findings support sustainable development and long-term conservation of Iran's water resources while providing useful insights for other countries, particularly those located in the world's (semi)arid regions.