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Multi-scale aquifer characterization and groundwater flow model parameterization using direct push technologies |
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| Authors: | Bart Rogiers Thomas Vienken Matej Gedeon Okke Batelaan Dirk Mallants Marijke Huysmans Alain Dassargues |
| Institution: | 1. Institute for Environment, Health and Safety, Belgian Nuclear Research Centre (SCK·CEN), Boeretang 200, 2400, Mol, Belgium 2. Department Monitoring and Exploration Technologies, UFZ-Helmholtz Centre for Environmental Research, Permoserstr. 15, 04318, Leipzig, Germany 3. Department of Earth and Environmental Sciences, KU Leuven, Celestijnenlaan 200e-bus 2410, 3001, Heverlee, Belgium 4. Department of Hydrology and Hydraulic Engineering, Vrije Universiteit Brussel, Pleinlaan 2, 1050, Brussels, Belgium 5. School of the Environment, Flinders University, GPO Box 2100, Adelaide, SA, 5001, Australia 6. Groundwater Hydrology Program, CSIRO Land and Water, Waite Road-Gate 4, Glen Osmond, SA, 5064, Australia 7. Hydrogeology and Environmental Geology, Department of Architecture, Geology, Environment and Civil Engineering (ArGEnCo) and Aquapole, Université de Liège, B.52/3 Sart-Tilman, 4000, Liège, Belgium |
| Abstract: | Direct push (DP) technologies are typically used for cost-effective geotechnical characterization of unconsolidated soils and sediments. In more recent developments, DP technologies have been used for efficient hydraulic conductivity (K) characterization along vertical profiles with sampling resolutions of up to a few centimetres. Until date, however, only a limited number of studies document high-resolution in situ DP data for three-dimensional conceptual hydrogeological model development and groundwater flow model parameterization. This study demonstrates how DP technologies improve building of a conceptual hydrogeological model. We further evaluate the degree to which the DP-derived hydrogeological parameter K, measured across different spatial scales, improves performance of a regional groundwater flow model. The study area covers an area of ~60 km2 with two overlying, mainly unconsolidated sand aquifers separated by a 5–7 m thick highly heterogeneous clay layer (in north-eastern Belgium). The hydrostratigraphy was obtained from an analysis of cored boreholes and about 265 cone penetration tests (CPTs). The hydrogeological parameter K was derived from a combined analysis of core and CPT data and also from hydraulic direct push tests. A total of 50 three-dimensional realizations of K were generated using a non-stationary multivariate geostatistical approach. To preserve the measured K values in the stochastic realizations, the groundwater model K realizations were conditioned on the borehole and direct push data. Optimization was performed to select the best performing model parameterization out of the 50 realizations. This model outperformed a previously developed reference model with homogeneous K fields for all hydrogeological layers. Comparison of particle tracking simulations, based either on the optimal heterogeneous or reference homogeneous groundwater model flow fields, demonstrate the impact DP-derived subsurface heterogeneity in K can have on groundwater flow and solute transport. We demonstrated that DP technologies, especially when calibrated with site-specific data, provide high-resolution 3D subsurface data for building more reliable conceptual models and increasing groundwater flow model performance. |
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