GIS-supported hydrogeological assessment for territorial management: The GOD–T index for aquifer vulnerability in the Moniquirá–Sutamarchán River basin, Boyacá (Colombia)

Study region The Moniquirá–Sutamarchán River basin (19.69 km²) is located in the upper Suárez River system, Boyacá, Colombia, within a tropical inter-Andean Mountain environment characterized by fractured Mesozoic sedimentary formations and bimodal rainfall patterns. Study focus This study integrates the conceptual Thomas (ABCD) hydrological model with the classical GOD method to develop a composite GOD–Thomas (GOD–T) index for intrinsic aquifer vulnerability assessment. Groundwater recharge was simulated using hydrometeorological series (2000–2025) and spatially distributed at 12.5 m resolution within a GIS environment. Model calibration yielded satisfactory performance (NSE = 0.8363; R² = 0.8363; r = 0.956), supporting the reliability of simulated recharge as a dynamic vulnerability parameter. New hydrological insights for the region Results reveal that recharge is strongly controlled by lithological fracturing and topographic gradients, with the highest infiltration rates occurring in the Ritoque, Arcabuco, and Paja formations. Incorporating simulated recharge significantly improves the spatial discrimination of vulnerability classes compared to static approaches. Moderate vulnerability predominates (77%), while high and very high vulnerability zones (≈17%) coincide with shallow water tables and permeable fractured units. The GOD–T framework demonstrates that integrating dynamic recharge processes improves the hydrogeological understanding of tropical Andean basins and provides a reproducible approach for groundwater protection and territorial planning in data-scarce mountain regions.