References of "Dassargues, Alain"
     in
Bookmark and Share    
See detailCarte hydrogéologique de Wallonie, Waremme-Momalle 41/3-4, Heers-Borgloon 33/7-8, 1/25.000 : [notice explicative]
Hallet, Vincent; Peters, Valérie; Ruthy, Ingrid ULg et al

Book published by Service Public de Wallonie, DGARNE - Actualisation partielle: juin 2012 - Première édition : mars 2000 (2012)

Detailed reference viewed: 7 (1 ULg)
See detailCarte hydrogéologique de Wallonie, Waremme-Momalle 41/3-4, Heers-Borgloon 33/7-8
Hallet, Vincent; Ruthy, Ingrid ULg; Peters, Valérie et al

Cartographic material (2012)

Detailed reference viewed: 5 (0 ULg)
Full Text
See detailAir permeametry on outcrop analogues: a composite image of the Neogene aquifer, Belgium
Rogiers, Bart; Beerten, K.; Smekens, T. et al

in Geophysical Research Abstracts, Vol. 14, EGU2012-1788-1 (2012, May)

Saturated hydraulic conductivity (Ks) is one of the most important parameters determining groundwater flow and contaminant transport in both unsaturated and saturated porous media. While several well ... [more ▼]

Saturated hydraulic conductivity (Ks) is one of the most important parameters determining groundwater flow and contaminant transport in both unsaturated and saturated porous media. While several well-established laboratory methods exist for determining Ks, in-situ measurements of this parameter remain very complex. Since the 50’s, and increasingly from the late 80’s, air permeameters are being used effectively as an indirect method to determine Ks on outcrop sediments. In this paper, the heterogeneity within outcrop sediments that are analogues for the Neogene aquifer hydrostratigraphic units in northern Belgium is studied with a hand-held air permeameter. This aquifer, representing a major groundwater source, consists of several sandy geological units from Miocene to Pleistocene age with a marine to continental origin. Moreover, it plays an important role in the Belgian deep geological radwaste disposal studies, and is the subject of a safety assessment for a future low-level radwaste surface repository. To characterise the variability between and within the different lithostratigraphical aquifer units, 804 air permeability measurements at cm-scale were performed on several outcrops that are analogues for the sandy aquifer sediments and a highly heterogeneous aquitard. Equivalent meter-scale Ks tensors were calculated numerically through the law of flow conservation to obtain the vertical anisotropy factor. The off-diagonal tensor components were shown to be negligible. To validate the air permeametry data, 18 additional constant head permeameter tests on 100 cm3 cores and 27 grain size analyses based Ks assessments were performed on outcrop material. The comparison indicates that hand-held air permeameters are very effective and useful tools to characterise the magnitude of hydraulic conductivity, as well as it’s small-scale variability and anisotropy, on a broad range of sediment types. However, a comparison with data from a previous borehole campaign on similar though not identical aquifer sediments reveals that the Ks values predicted at the outcrops are systematically higher by at least a factor of 10 than the corresponding Ks distributions determined from the borehole cores. One explanation is the weathering state of several-cm thick clay lenses, i.e. much less weathered in the aquitard than in the analogous outcrop with correspondingly lower conductivities for the aquitard. This shows that transferring outcrop data to the subsurface should be done with care because of different degrees of compaction, weathering states, etc. [less ▲]

Detailed reference viewed: 4 (0 ULg)
Full Text
See detailCentimeter-scale secondary information on hydraulic conductivity using a hand-held air permeameter on borehole cores
Rogiers, Bart; Winters, P.; Huysmans, Marijke et al

in Geophysical Research Abstracts, Vol. 14, EGU2012-1794-1 (2012, May)

Saturated hydraulic conductivity (Ks) is one of the most important parameters determining groundwater flow and contaminant transport in both unsaturated and saturated porous media. Determining the small ... [more ▼]

Saturated hydraulic conductivity (Ks) is one of the most important parameters determining groundwater flow and contaminant transport in both unsaturated and saturated porous media. Determining the small-scale variability of this parameter is key to evaluate implications on effective parameters at the larger scale. Moreover, for stochastic simulations of groundwater flow and contaminant transport, accurate models on the spatial variability of Ks are very much needed. While several well-established laboratory methods exist for determining Ks, investigating the small-scale variability remains a challenge. If several tens to hundreds of metres of borehole core has to be hydraulically characterised at the centimetre to decimetre scale, several hundreds to thousands of Ks measurements are required, which makes it very costly and time-consuming should traditional methods be used. With reliable air permeameters becoming increasingly available from the late 80’s, a fast and effective indirect method exists to determine Ks. Therefore, the use of hand-held air permeameter measurements for determining very accurate small-scale heterogeneity about Ks is very appealing. Very little is known, however, on its applicability for borehole cores that typically carry a small sediment volume. Therefore, the method was tested on several borehole cores of different size, originating from the Campine basin, Northern Belgium. The studied sediments are of Miocene to Pleistocene age, with a marine to continental origin, and consist of sand to clayey sand with distinct clay lenses, resulting in a Ks range of 7 orders of magnitude. During previous studies, two samples were taken from borehole cores each two meters for performing constant head lab permeameter tests. This data is now used as a reference for the air permeameter measurements that are performed with a resolution of 5 centimetres. Preliminary results indicate a very good correlation between the previously gathered constant head Ks data and the air permeability measurements, but a systematic bias seems to exist. A geostatistical analysis with cross-validation is performed to assess the predictive uncertainty on Ks, using both types of data. We conclude that performing hand-held air permeameter measurements on undisturbed borehole cores provides a very cost-effective way to obtain very detailed information in the framework of stochastic simulation and conditioning of heterogeneous hydraulic conductivity fields. [less ▲]

Detailed reference viewed: 8 (0 ULg)
Full Text
Peer Reviewed
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 ▲]

Detailed reference viewed: 80 (14 ULg)
Full Text
Peer Reviewed
See detailRelationship between sedimentary features and permeability at different scales in the Brussels Sands
Possemiers, Mathias; Huysmans, Marijke; Peeters, Luk et al

in Geologica Belgica (2012), 15(3), 156-164

The Brussels Sands display a complex three-dimensional subsurface architecture. This sedimentological heterogeneity induces a highly heterogeneous spatial distribution of hydrogeological parameters at ... [more ▼]

The Brussels Sands display a complex three-dimensional subsurface architecture. This sedimentological heterogeneity induces a highly heterogeneous spatial distribution of hydrogeological parameters at different scales and may consequently influence subsurface fluid flow and solute migration. This study aims at characterizing spatial variability of permeability at different scales in the Brussels Sands. Firstly, a literature review on the permeability distribution of the Brussels Sands was performed. Secondly, a field campaign was carried out consisting of field observations of the small-scale sedimentary structures and in situ measurements of air permeability. A total of 6550 cm-scale air permeability measurements were carried out in situ in three Brussels Sands quarries in the central part of Belgium: Bierbeek, Mont Saint Guibert and Chaumont Gistoux. On the large basin scale, substantial differences in permeability are observed. A literature data analysis shows that there is no clear correlation between hydraulic conductivity and sedimentary facies. At the small scale, results show that permeability heterogeneity and anisotropy are strongly influenced by sedimentary heterogeneity in all three quarries. Clay-rich sedimentary features such as bottomsets and distinct mud drapes exhibit a different statistical and geostatistical permeability distribution compared to the cross-bedded lithofacies, where the permeability anisotropy is dominated by the foreset lamination orientation. [less ▲]

Detailed reference viewed: 78 (7 ULg)
See detailCarte hydrogéologique de Wallonie, Louveigné-Spa, 49/3-4
Ruthy, Ingrid ULg; Dassargues, Alain ULg

Cartographic material (2012)

Detailed reference viewed: 5 (0 ULg)
See detailCarte hydrogéologique de Wallonie, Louveigné-Spa; 49/3-4, 1/25.000 : [notice explicative]
Ruthy, Ingrid ULg; Dassargues, Alain ULg

Book published by Service Public de Wallonie, DGARNE - Version provisoire : mars 2012 (2012)

Detailed reference viewed: 2 (0 ULg)
Full Text
Peer Reviewed
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 ▲]

Detailed reference viewed: 86 (34 ULg)
Full Text
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)

Detailed reference viewed: 35 (7 ULg)
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)

Detailed reference viewed: 40 (5 ULg)
Full Text
Peer Reviewed
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 ▲]

Detailed reference viewed: 73 (20 ULg)