The research, led by Yan Lévesque of the Institut National de La Recherche Scientifique and Université du Québec à Chicoutimi, together with Romain Chesnaux, Julien Walter and Lamine Boumaiza, tackles one of the most persistent problems in hydrogeology: calibrating a numerical model when direct measurements of groundwater levels are sparse. Groundwater models are the workhorses of water resource management, used to predict how aquifers will respond to pumping, drought and climate change. Yet a model is only as good as the data used to constrain it, and in many regions of the world, observation wells are few and far between.

To build their model, the team assembled an unusually rich geological picture of the moraine system. They drew on 94 boreholes drilled through the glacial deposits, five stratigraphic cross-sections that traced the layering of sediments across the landscape, and three complementary geophysical techniques: 20 transient electromagnetic surveys, 6 electrical resistivity tomography surveys, and 6 ground-penetrating radar surveys. Each method probes the subsurface in a different way. Transient electromagnetic surveys induce currents in the ground and measure how they decay, revealing contrasts in electrical conductivity that distinguish saturated from unsaturated materials. Electrical resistivity tomography injects current through electrodes and maps resistivity variations in two-dimensional slices, while ground-penetrating radar uses high-frequency radio waves to image shallow stratigraphy with centimeter-scale resolution.

From this combined dataset, the researchers constructed an integrated three-dimensional geological framework capturing the complex, heterogeneous and anisotropic character of the aquifer system. Glacial deposits such as moraines are notoriously difficult to model because they were deposited by ice in chaotic, laterally discontinuous layers. A single borehole may reveal coarse sand at one location while a neighboring hole, only a few hundred meters away, encounters dense till. Geophysics helps bridge those gaps by interpolating between the hard constraints of the boreholes with continuous geophysical profiles.

With the geological architecture in place, the team turned to numerical simulation. They used FEFLOW, a widely applied finite element software package for modeling groundwater flow, mass and heat transport in porous media, to run flow simulations and define initial estimates of hydraulic parameters such as hydraulic conductivity, which describes how easily water moves through the subsurface. These initial values were then refined through calibration, the process of adjusting model parameters until simulated groundwater levels match observed ones as closely as possible.

The crucial innovation lay in what the researchers used as calibration targets. Instead of relying solely on water levels measured in wells, they employed groundwater levels derived from the geophysical data themselves. Because the electrical resistivity of sediments changes sharply at the water table, where dry unsaturated material gives way to saturated material, geophysical surveys can be inverted to estimate the depth of the saturated zone. The team used the FePEST module, an interface between FEFLOW and the PEST parameter estimation software, to automatically adjust hydraulic parameters until the model reproduced these geophysics-derived water levels.

The real test came afterward. The researchers evaluated the calibrated model against an entirely independent dataset: piezometric measurements from 26 observation wells distributed across the study area. These wells had not been used in the calibration, so they provided an unbiased measure of the model’s predictive skill. The comparison between calibrated and observed groundwater levels yielded a root mean square error of 3.69 meters, a relatively low value for a regional-scale model of heterogeneous glacial terrain, indicating good agreement with field observations.

That result carries weight beyond one moraine in Quebec. In many parts of the world, including remote northern communities, agricultural regions with sparse monitoring networks, and developing countries investing in groundwater resources for the first time, the cost of drilling observation wells limits how well aquifers can be understood. Geophysical surveys are faster and often cheaper per unit of spatial coverage than drilling, and this study demonstrates that their output can serve not merely as a qualitative check on a model but as quantitative calibration data that actively refines hydraulic parameters.

The approach also reframes the traditional division of labor between geophysics and hydrogeology. Conventionally, geophysical data have been used to build geological models, delineating aquifer boundaries and layer thicknesses, while calibration has depended on hydraulic measurements. The new work shows that geophysically derived groundwater levels can play both roles, supporting the geological framework and simultaneously constraining the flow model. This dual use of a single dataset maximizes the value of every field campaign and reduces the uncertainty that accumulates when models are calibrated against too few points.

The findings arrive at a moment when pressure on groundwater is intensifying worldwide. Aquifers feed rivers, sustain ecosystems and supply roughly half of the world’s drinking water, yet many are being depleted faster than they recharge. Reliable regional models are essential for managing this invisible resource, and the Quebec study offers a practical template: combine boreholes, multiple geophysical methods and automated calibration to extract the maximum information from limited field data. As the authors note, integrating geophysical datasets with conventional hydrogeological observations improves parameter estimation and enhances the reliability of regional groundwater flow models, a step toward water management decisions grounded in a clearer picture of what lies beneath.

Subject of Research: Calibration of a 3D regional groundwater flow model using groundwater levels derived from geophysical surveys in Quebec

Article Title: Calibration of a 3D regional groundwater model using geophysics-derived groundwater levels

Article References: Lévesque, Y., Chesnaux, R., Walter, J., & Boumaiza, L. (2026). Calibration of a 3D regional groundwater model using geophysics-derived groundwater levels. Hydrogeology Journal. https://doi.org/10.1007/s10040-026-03144-w

Image Credits: AI Generated

DOI: 10.1007/s10040-026-03144-w

Keywords: groundwater modeling, geophysics, hydrogeology, aquifer calibration, transient electromagnetics, electrical resistivity tomography, ground-penetrating radar, FEFLOW, Saint-Narcisse Moraine, Quebec, hydraulic conductivity, water table