Geophysical evidence of structural and topographic controls on the Tulancingo Valley aquifer system, Central Mexico

The Tulancingo Valley aquifer, located in southeastern Hidalgo state, central-eastern Mexico, is one of the most overexploited groundwater resources. To characterize its hydrogeological framework and the mechanisms driving deviations in the static water level, an integration of gravimetric data, transient electromagnetic (TEM) soundings and electrical resistivity tomography (ERT) was implemented. Residual gravity data delineate prominent NW-SE and NE-SW structural lineaments associated with the Acoculco caldera and regional normal faulting, while resistivity models identify two hydraulically connected systems separated by a faulted volcanic aquitard: a shallow aquifer (up to 20 m depth; ~2–15 Ω·m) and a heavily exploited deep regional aquifer (reaching depths of 130–250 m; ~2–20 Ω·m). The regional structural features exert a primary control on the hydrodynamics of the deep aquifer. These fault and fracture networks lead to hydraulic connectivity and partitioned groundwater flow, directly influencing the spatial distribution of static water level variations. Projections indicate that under this structurally controlled flow regime, current extraction trends will drive water deficits to 23.64 Mm³ and 31.64 Mm³ by 2030 and 2050, respectively. These findings provide a geophysical base for sustainable groundwater management in structurally complex aquifer systems.