High-resolution mapping of shallow geothermal resources in Spain through multivariate spatial analysis

• A nationwide GIS-based multivariate analysis was conducted to assess shallow geothermal potential across Spain. • Key subsurface parameters, including thermal gradient, lithology, thermal conductivity, permeability, and heat capacity, were integrated into the model. • Geothermal favorability indices were generated through map algebra and spatial classification techniques. • The resulting geothermal potential map was validated using geological data and previous studies, confirming its reliability. • The approach provides a valuable preliminary tool for regional energy planning and sustainable land-use strategies. Identifying areas with potential for low-enthalpy geothermal energy exploitation is a key step toward sustainable and decentralized energy planning, particularly in countries like Spain, where seasonal high temperatures and marked thermal contrasts influence subsurface heat dynamics. This study presents a nationwide assessment of shallow geothermal potential using a multivariate spatial analysis approach. The methodology integrates key geological and thermal variables, including subsurface temperature gradients at different levels, lithological composition and other influential properties such as thermal conductivity, permeability, and volumetric heat capacity. These parameters were processed through normalization, thematic weighting, map algebra, and spatial classification methods within a GIS-based framework. As a result, geothermal favorability indices were generated, allowing for the identification and mapping of areas with varying levels of potential for low and very low-enthalpy applications. The resulting geothermal potential map was validated through comparison with existing geological information and previously published studies. The outcomes confirm the reliability and applicability of the multivariate approach as a preliminary tool for identifying shallow geothermal resources. This contributes not only to a better understanding of the geothermal landscape in Spain but also to supporting informed decision-making in regional energy planning and sustainable land management strategies.