References of "Orban, Philippe"
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See detailHow tracer tests simulations strongly constrain flow and solute transport models in fractured chalk aquifers
Goderniaux, Pascal ULg; Daoudi, Moubarak; Orban, Philippe ULg et al

Conference (2012, May)

Flow and solute transport in the saturated zone of a micro-fissured and fractured chalk aquifer (Geer basin, Belgium) has been studied by more than 35 tracer tests in 11 sites. The tracer tests campaign ... [more ▼]

Flow and solute transport in the saturated zone of a micro-fissured and fractured chalk aquifer (Geer basin, Belgium) has been studied by more than 35 tracer tests in 11 sites. The tracer tests campaign was preceded by a morphostructural study associated to a geophysical survey including electrical resistivity and refraction seismic measurements. Results provided information on the main expected fracturation axis where a series of injection and monitoring wells were drilled. In each of the 11 sites, multi-tracer tests have been performed in groundwater convergent flow conditions to pumping wells or draining galleries (used for drinking water production). The analysis of the detailed quantitative breakthrough curves allowed identifying various transport behaviours, from rapid advective to dominant dispersive processes with immobile water effects. Groundwater flow and solute transport in such a fractured chalk can be simulated using different conceptual approaches. Using HYDROGEOSPHERE (Therrien and Sudicky, 1996), a comparison is made between two ways for representing the fracture zones: (1) high contrasted hydraulic conductivity zones with a classical REV approach and (2) the explicit representation of discrete fractures interacting with a porous medium. Promising results are found using the discrete approach for representing the fractures. In this last case, an aperture of the order of the millimetre is enough for creating, where it is needed, a fast advective peak combined with a long highly dispersive component due to the chalk matrix. The discrete fracture approach prevents the modeller from introducing unrealistic parameters values in the fracture zones as it is generally the case in the classical REV-based method where the fractured zones are simply represented by elongated REV. However, it is shown that the availability of field data, as multi-tracers test results, creates very high constraints to be taken into account in the calibration processes (i.e calibration on the measured groundwater flow and transport conditions). The detailed calibration on the different breakthrough curves is not an easy task and automatic calibration is not easy to organize. Results are particularly illustrative to show that a detailed parameterization and calibration of such a local situation remain difficult. Perspectives will be discussed about the potential use of automatic calibration tools as UCODE_2005 or PEST for solving such local situation models and the needed further steps for ‘upscaling’ local situation models at the scale of the whole aquifer or groundwater body. [less ▲]

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See detailA regional flux-based risk assessment approach for multiple contaminated sites on groundwater bodies
Jamin, Pierre ULg; Dollé, Fabien ULg; Chisala, Brenda et al

in Journal of Contaminant Hydrology (2012), 127(1-4), 65-75

In the context of the Water Framework Directive (EP and CEU, 2000), management plans have to be set up to monitor and to maintain water quality in groundwater bodies in the EU. In heavily industrialized ... [more ▼]

In the context of the Water Framework Directive (EP and CEU, 2000), management plans have to be set up to monitor and to maintain water quality in groundwater bodies in the EU. In heavily industrialized and urbanized areas, the cumulative effect of multiple contaminant sources is likely and has to be evaluated. In order to propose adequate measures, the calculated risk should be based on criteria reflecting the risk of groundwater quality deterioration, in a cumulative manner and at the scale of the entire groundwater body. An integrated GIS- and flux-based risk assessment approach for groundwater bodies is described, with a regional scale indicator for evaluating the quality status of the groundwater body. It is based on the SEQ-ESO currently used in the Walloon Region of Belgium which defines, for different water uses and for a detailed list of groundwater contaminants, a set of threshold values reflecting the levels of water quality and degradation with respect to each contaminant. The methodology is illustrated with first results at a regional scale on a groundwater body-scale application to a contaminated alluvial aquifer which has been classified to be at risk of not reaching a good quality status by 2015. These first results show that contaminants resulting from old industrial activities in that area are likely to contribute significantly to the degradation of groundwater quality. However, further investigations are required on the evaluation of the actual polluting pressures before any definitive conclusion be established. [less ▲]

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See detailFlux-based Risk Assessement of the impact of Contaminants on Water resources and ECOsystems
Jamin, Pierre ULg; Dujardin, Juliette; Crèvecoeur, Sophie et al

Report (2012)

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See detailFlux-based risk assessment of the impact of contamnants on water ressources and ecosystems - FRAC-WECO.
Jamin, Pierre ULg; Dujardin, J.; Crévecoeur, Sophie et al

Report (2012)

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See detailModeling climate change impacts on groundwater resources using transient stochastic climatic scenarios
Goderniaux, Pascal ULg; Brouyère, Serge ULg; Blenkinsop, Stephen et al

in Water Resources Research (2011), 47

Several studies have highlighted the potential negative impact of climate change on groundwater reserves but additional work is required to help water managers to plan for future changes. In particular ... [more ▼]

Several studies have highlighted the potential negative impact of climate change on groundwater reserves but additional work is required to help water managers to plan for future changes. In particular, existing studies provide projections for a stationary climate representative of the end of the century, although information is demanded for the near-future. Such time-slice experiments fail to account for the transient nature of climatic changes over the century. Moreover, uncertainty linked to natural climate variability is not explicitly considered in previous studies. In this study, we substantially improve upon the state-of-the-art by using a sophisticated transient weather generator (WG) in combination with an integrated surface-subsurface hydrological model (Geer basin, Belgium) developed with the finite element modelling software 'HydroGeoSphere'. This version of the WG enables the stochastic generation of large numbers of equiprobable climatic time series, representing transient climate change, and used to assess impacts in a probabilistic way. For the Geer basin, 30 equiprobable climate change scenarios from 2010 to 2085 have been generated for each of 6 different RCMs. Results show that although the 95% confidence intervals calculated around projected groundwater levels remain large, the climate change signal becomes stronger than that of natural climate variability by 2085. Additionally, the WG ability to simulate transient climate change enabled the assessment of the likely timescale and associated uncertainty of a specific impact, providing managers with additional information when planning further investment. This methodology constitutes a real improvement in the field of groundwater projections under climate change conditions. [less ▲]

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