Characterizing groundwater heat transport in a complex lowland aquifer using paleo-temperature reconstruction, satellite data, temperature–depth profiles, and numerical models

Abstract. Heat is a naturally occurring, widespread groundwater tracer that can be used to identify flow patterns in systems. Temperature measurements, being relatively inexpensive and effortless gather, represent valuable source of information which exploited reduce uncertainties on flow, and, for example, support performance assessment studies waste disposal sites. In lowland setting, however, hydraulic gradients are typically small, whether temperature measurements inform us about catchment-scale remains an open question. For the Neogene Aquifer Flanders, solute transport models have been developed framework safety feasibility underlying Boom Clay formation as potential host rock geological radioactive waste. However, simulated fluxes by these still subject large they constrained heads only. current study, we use state-of-the-art 3D steady-state model, calibrated against head build transient heat assessing additional state variable, setting at catchment scale. We therefore temperature–depth (TD) profiles variable observations inverse conditioning. Furthermore, Holocene paleo-temperature time curve was constructed based reconstructions Europe from several sources combination with land surface (LST) remotely sensed monthly data 2001 2019 (retrieved NASA's Moderate Resolution Imaging Spectroradiometer, MODIS). The aim research understand mechanisms characterize distribution dynamics Aquifer. simulation results clearly underline advection/convection conduction major mechanisms, reduced role zones where flux magnitudes low, suggests also useful indicator setting. performed scenarios highlight important roles (i) hydrological features withdrawals driving local systems (ii) inclusion subsurface like faults conceptualization development hydrogeological investigations. These findings serve proxy influence advective barrier/conduit faults, particularly Rauw fault this case, suggest solutes released might affected similar ways.