References of "Brouyère, Serge"
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See detailHydrogéologie du bassin du Hoyoux
Briers, Pierre ULiege; Jamin, Pierre ULiege; Ruthy, Ingrid ULiege et al

in Atlas du Karst Wallon - Bassins versants du Hoyoux et de la Solières (2016)

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See detailDélivrable D3.3 Bilans hydrogéologiques
Schmit, Flore; Hallet, Vincent; Briers, Pierre ULiege et al

Report (2016)

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See detailHeat tracer and solute tests in an alluvial aquifer: field experiment and inverse modelling
Dassargues, Alain ULiege; Klepikova, Maria; Jamin, Pierre ULiege et al

Poster (2015, December 18)

Using heat as an active tracer in different types of aquifers is a topic of increasing interest. In this study, we investigate the potential interest of using heat tracer tests for characterization of a ... [more ▼]

Using heat as an active tracer in different types of aquifers is a topic of increasing interest. In this study, we investigate the potential interest of using heat tracer tests for characterization of a shallow alluvial aquifer. A thermal tracer test was conducted in the alluvial aquifer of the Meuse River, Belgium. The tracing experiment consisted in simultaneously injecting heated water and a dye tracer in a piezometer and monitoring the evolution of groundwater temperature and tracer concentration in the recovery well and in monitoring wells. To get insights in the 3D characteristics of the heat transport mechanisms the space-filling arrangement of observation wells was used. The breakthrough curves measured in the recovery well showed that heat transfer in the alluvial aquifer is slower and more dispersive than solute transport. Recovery is very low for heat while in the same time it is measured as relatively high for the solute tracer. This is due to the fact that heat diffusion is larger than molecular diffusion, implying that exchange between groundwater and the porous medium matrix is far more significant for heat than for solute tracers. Temperature breakthrough curves in other piezometers are contrasted with what would be expected in an ideal layered aquifer. They reveal strongly unequal lateral and vertical components of the transport mechanisms. The observed complex behavior of the heat plume was explained by the groundwater flow gradient on the site and heterogeneities of hydraulic conductivity field. By using numerical model of heat and flow coupled with pilot points inverse approach main preferential paths were characterized. [less ▲]

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See detailCase study 2: Groundwater – surface water interaction in limestone areas of the GWB BE_Meuse_RWM021 (Belgium)
Brouyère, Serge ULiege; Briers, Pierre ULiege; Schmit, Flore et al

in Hinsby, Klaus; Schutten, Johan; Craig, Matt (Eds.) et al Technical Report on Groundwater Associated Aquatic Ecosystems (2015)

The achievement of good status in groundwater bodies involves meeting a series of conditions, which are defined in the Water Framework Directive (WFD) and, in the case of good chemical status, are given ... [more ▼]

The achievement of good status in groundwater bodies involves meeting a series of conditions, which are defined in the Water Framework Directive (WFD) and, in the case of good chemical status, are given further detail in the Groundwater Directive (GWD). One of these conditions is to ensure that groundwater inputs to associated surface waters do not result in failure to meet the environmental objectives of those waters or result in significant diminution in status/ecological or chemical quality of those waters. GWAAE (Groundwater Associated Aquatic Ecosystems) are those surface water bodies (SWBs), including rivers, standing waters and transitional waters where the surface water ecology and hydrology is dependent on contributions from groundwater in order to meet their environmental objectives under the WFD. These environmental objectives may vary, and therefore the associated environmental quality standards (EQS) or flow/level requirements of GWAAEs may differ between high status and good status SWBs. As noted in the Blueprint for Water, analysis of the first River Basin Management Plans has shown that Member States (MS) have experienced difficulties in understanding the interactions between groundwater and surface water and undertaking the necessary status assessments. This was highlighted in a survey carried out by Working Group Groundwater (WGGW) in 2014/15, which indicated that only half of the MS had assessed quantitative interactions and very few had addressed chemical pressures, including the derivation of threshold values (TVs) that were appropriate to the WFD objectives for GWAAEs. This report aims to further knowledge on what GWAAE are, how they are aligned to WFD processes, and support Member States to properly include the needs of these ecosystems in river basin management planning. The report clarifies the categories of GWAAE and their relative dependence on groundwater and collates current available knowledge and experience via a number of examples and case studies. Terminology and status assessment procedures are explained and pragmatic approaches are proposed which leave some flexibility for MS to adapt to their own specific needs. This technical report, which is not a "guidance document", makes use of and complements existing CIS documents, including existing technical reports on groundwater dependent terrestrial ecosystems (GWDTEs) and Guidance Document 18 (Guidance on Groundwater Status and Trend Assessment). A number of recommendations for technical users of the report are highlighted in boxes in each Chapter. The common themes from these recommendations are collated in Chapter 8, as issues and questions to WGGW and MS in general. The key message from this is the need for closer interaction between scientific disciplines, practitioners and Working Groups in developing conceptual understanding for GWAAEs and implementation of WFD requirements, including identification of GWAAEs, their characterisation and monitoring, and adopting appropriate status assessment methodologies. [less ▲]

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See detailMéthodologie de diagnostic environnemental autour de captages d’eau potabilisable sensibles qualitativement du point de vue nitrate
Vandenberghe, Christophe ULiege; Bah, Boubacar Billo ULiege; Orban, Philippe ULiege et al

Report (2015)

Le projet s’inscrit dans le cadre des « contrats de captages » dont la mise en oeuvre est assurée par la SPGE (Société Publique de Gestion de l’Eau) et ce, conformément au contrat de gestion qui lie cette ... [more ▼]

Le projet s’inscrit dans le cadre des « contrats de captages » dont la mise en oeuvre est assurée par la SPGE (Société Publique de Gestion de l’Eau) et ce, conformément au contrat de gestion qui lie cette dernière avec le Gouvernement wallon. L’objectif se décline en trois phases : 1. établir une méthodologie commune de détermination et priorisation des actions à entreprendre autour de captages en vue d’y préserver ou de restaurer la qualité de l’eau ; 2. tester la méthodologie (définition des actions à entreprendre) sur six situations jugées représentatives sur des captages de la SWDE (Société Wallonne des Eaux) ; 3. proposer et coordonner des actions à mettre en oeuvre sur deux ou trois des six sites pilotes. La méthodologie est traduite en logigrammes d’actions qui proposent des démarches communes de diagnostic et d’actions à entreprendre autour de captages en vue d’y préserver ou de restaurer la qualité de l’eau. [less ▲]

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See detailUse of dual carbon-chlorine isotope analysis to identify degradation pathways of 1,1,1-trichloroethane in groundwater
Palau, Jordi; Jamin, Pierre ULiege; Badin, Alice et al

Conference (2015, September 17)

The high susceptibility of chlorinated aliphatic hydrocarbons (CAHs) like 1,1,1-trichloroethane (1,1,1-TCA) to be transformed via different competing pathways (biotic and abiotic) complicates the ... [more ▼]

The high susceptibility of chlorinated aliphatic hydrocarbons (CAHs) like 1,1,1-trichloroethane (1,1,1-TCA) to be transformed via different competing pathways (biotic and abiotic) complicates the assessment of their fate in groundwater. This knowledge is necessary to evaluate contaminant degradation and potential formation of toxic intermediates. Identifying pathways is further complicated in sites contaminated by mixed CAHs because some degradation products of 1,1,1-TCA can be formed from different precursors. Here, identification of pathways based solely on substrate-product concentration relationships may lead to ambiguous interpretations. This study investigates, for the first time, dual C−Cl isotope fractionation as a means of identifying and assessing degradation pathways of 1,1,1-TCA in groundwater. Distinctly different dual isotope trends (L = Δδ13C/Δδ37Cl) were observed for 1,1,1-TCA transformation via oxidation with heat-activated persulfate (L = ∞), reduction with zerovalent iron (L = 1.5 ± 0.1), hydrolysis and dehydrohalogenation (HY/DH, L = 0.33 ± 0.04) in laboratory experiments, illustrating the potential of a dual isotope approach. This approach was evaluated in an aerobic aquifer impacted by 1,1,1-TCA and trichloroethylene (TCE) with concentrations of up to 20 mg/L and 3.4 mg/L, respectively. For 1,1,1-TCA, the dual isotope slope determined from field samples (L = 0.6 ± 0.2, r2 = 0.75) was close to the slope observed for HY/DH in the laboratory (L = 0.33 ± 0.04), indicating that HY/DH was the predominant degradation pathway of 1,1,1-TCA in the aquifer. The observed deviation could be explained by a minor contribution of additional degradation processes. This result, along with the little degradation of TCE determined from isotope measurements, confirmed that 1,1,1-TCA was the main source of the 1,1-dichlorethylene (1,1-DCE) detected in the aquifer with concentrations of up to 10 mg/L. This study demonstrates that a dual C-Cl isotope approach can strongly improve the qualitative and quantitative assessment of 1,1,1-TCA degradation processes in the field. [less ▲]

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See detailTowards processes-based groundwater vulnerability assessments
Dassargues, Alain ULiege; Popescu, Cristina; Brouyère, Serge ULiege

Conference (2015, September 15)

Various groundwater vulnerability methods have recently been developed. Considering groundwater quality issues, the most common techniques are based on calculation of an index expressing the protective ... [more ▼]

Various groundwater vulnerability methods have recently been developed. Considering groundwater quality issues, the most common techniques are based on calculation of an index expressing the protective effect (i.e. in terms of solute contaminant transport) of underground formations overlying the groundwater resource (Gogu & Dassargues, 2000, Gogu et al., 2003)). However, there is a strong need for new methods giving more emphasis on the processes-based calculation of vulnerability indicators. As a first alternative, a method is proposed based on three factors describing a pollution event (Brouyère et al., 2001): (1) the transit time from the source to the target, (2) the duration of the contamination breakthrough at the target, (3) the ratio between the maximum concentration at the target to the released concentration at the contamination source. The method can feature the impact of surface runoff to preferential infiltration points. Practically, the assessment can then be based on the simulated breakthrough curves at the ‘target’ corresponding to Dirac-type solicitations (Popescu et al., 2008). Different vulnerability maps can be built according to the relative importance conventionally given to each of the three factors. This concept allows a clear distinction between conventional aspects and processes-based results in the building of a final vulnerability indicator. A second proposal consists in reframing the groundwater vulnerability assessment in a Pressure-State-Impact causal chain that is familiar to decision makers (Beaujean et al., 2013). The method is here based on the calculation of sensitivity coefficients for a user-defined groundwater state for which several physically-based indicators are proposed. The sensitivity coefficients reflect the easiness with which the groundwater state transmits pressures into impacts. They are converted to vulnerability, using the concept of ‘transgressing a given threshold’ (Luers et al., 2003). While the methodology is general and can be applied in quantity as quality issues, the choice of causal chains has to be made prior to the calculation. The vulnerability is also related to a damaged state and is related to the ‘distance’ between the current state and a given threshold. Here also, the method allows a clear distinction between conventional choices (threshold) and scientific work (Dassargues et al., 2009). [less ▲]

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See detailA new hybrid approach for modelling groundwater flow in karst aquifers
Willems, Thibault ULiege; Hakoun, Vivien ULiege; Renard, Philippe et al

Conference (2015, September)

Groundwater flow modelling in karst aquifers represents a real challenge that requires adapted methods. The applicability of an innovative hybrid approach for modelling groundwater flow in karst aquifers ... [more ▼]

Groundwater flow modelling in karst aquifers represents a real challenge that requires adapted methods. The applicability of an innovative hybrid approach for modelling groundwater flow in karst aquifers, namely the Hybrid Finite Element Mixing Cell (HFEMC) method, is evaluated. The hybrid approach consists in combining a classical finite element (FE) model, to model slow flow in the rock matrix, with spatially distributed lumped reservoirs, to model fast flow in the karst conduits network. Water exchanges between the rock matrix and the conduits network are accounted for by means of an internal Fourier boundary conditions (BC). This BC (1st order exchange relation) allows to control the magnitude of water transfers between fast and slow flow domains. We tested the applicability of the HFEMC method on a schematic synthetic domain and on a real karst system. In the synthetic case analysis, we discussed dynamic processes of groundwater storage occurring in the karst system during a recharge pulse. The study focuses on the influence of selected parameters on representative variables such as the discharge curve of the karst system or pressure and mass transfers between conduits and rock matrix sub-domains. In this way, an inversion of the hydraulic gradient between karst conduits and the surrounding rock matrix is shown to occur during the recharge pulse. This phenomenon results in a temporary storage of water from conduits to the rock matrix, which impacts the modelled discharge curve. The first test performed on a real study site, the Noiraigue spring karst system (Jura mountains, Switzerland), exemplify the use of two separated lumped reservoirs for describing the conduits network, which allows to consider two base levels in the karst system. It also points out the challenges to face when modelling a complex natural karst system with the HFEMC approach. The results obtained show that the HFEMC approach is a good candidate to model groundwater flow in karst aquifers. [less ▲]

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See detailControlling factors and occurrence of inorganic and organic compounds in groundwater of urban and industrial areas
Gesels, Julie ULiege; Dollé, Fabien ULiege; Leclercq, Julie et al

Conference (2015, September)

A relatively extensive survey of groundwater contaminants is performed in urban and industrial contexts, at the regional scale (Walloon Region of Belgium), outside spots of contamination related to ... [more ▼]

A relatively extensive survey of groundwater contaminants is performed in urban and industrial contexts, at the regional scale (Walloon Region of Belgium), outside spots of contamination related to contaminated sites. More specifically, the most detected inorganic trace elements and organic contaminants are identified and their levels of occurrence are described statistically. Mechanisms that can explain their occurrence in groundwater are discussed. From a more pragmatic point of view, the data set has been also used to derive upper limits of pollutant background concentrations to be used in decision-making related to the management of contaminated groundwater in urban and industrial environments. The results presented are based on 243 samples from 8 sectors located in different geological contexts and different urban and industrial contexts. Each groundwater sample was analyzed for 19 inorganic trace elements, 61 organic micro-pollutants and 10 major and minor elements. Five physico-chemical parameters were measured in the field, at the time of sampling to determine the environmental conditions prevailing in groundwater. For comparison, existing groundwater analyses in natural context, available for the entire Walloon Region, were compiled from several databases. Cumulative distribution function plots allow comparing the distributions of inorganic trace elements in urban and industrial sectors to those obtained at the scale of the entire Walloon region. Cumulative distribution function plots are also used to compare the distribution of the inorganic trace elements in the different lithologies, in urban and industrial contexts. The composition of groundwater is altered in urban and industrial sectors with increased concentrations for most inorganic trace elements and organic contaminants. Anthropogenic influence is not limited to inputs of pollutants but also to alterations of subsurface environmental conditions, in particular redox conditions, resulting in the mobilization of pollutants. The influence of lithology is also marked in the data set. [less ▲]

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See detailThe use of the Vadose Zone Experimental Setup as an innovative in situ characterization method for the vadose zone: a case study at an industrial contaminated site in Belgium
Fernandez de Vera, Natalia ULiege; Beaujean, Jean ULiege; Jamin, Pierre ULiege et al

Conference (2015, September)

The development of protection and remediation plans for contaminated soil and groundwater require a detailed understanding of the transport of pollutants in the subsurface. However, such understanding is ... [more ▼]

The development of protection and remediation plans for contaminated soil and groundwater require a detailed understanding of the transport of pollutants in the subsurface. However, such understanding is affected by the lack of spatial and temporal coverage provided by the current in situ characterization technologies. A new system has been developed in order to overcome such limitations. The vadose zone experimental setup is a new development combining cross-hole geophysics and the Vadose Zone Monitoring System (VMS). In cross-hole geophysics, an injection of an electrical current using electrodes installed in vertical boreholes is triggered. From measured potential differences, spatial patterns related with subsurface heterogeneities, water content and solute concentrations are inferred. The VMS allows continuous measurements of water content at different depths of the vadose zone, as well as water sampling. The system is formed by a flexible sleeve containing monitoring units along its depth which is installed in a slanted borehole. The system was installed at a former industrial site in Belgium, where soil and groundwater are contaminated with BTEX, PAH, and heavy metals. Two VMS were installed in two slanted boreholes on site, together with four vertical boreholes containing electrodes for geophysical measurements. The site was initially monitored under natural recharge conditions. Water content sensors located along the VMS registered fast wetting and draining reactions to rainfall events followed by the activation of water transport through fractures. Results from soil water samples show continuous evolution of water chemistry with depth, due to disequilibrium between infiltrated water and the hydrochemical conditions in the unsaturated zone. Subsequently, a saline tracer was injected in the surface. The transport of the tracer in the subsurface was monitored via cross-hole and surface geophysics. Results from imaging reflect the evolution of a plume through vertical and lateral transport and dilution. [less ▲]

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See detailRegional occurence of greenhouses gases in groundwater: Initial results in shallow Belgian aquifers.
Hakoun, Vivien ULiege; Gesels, Julie ULiege; Tseng, Jean Hsiao-Chun et al

Poster (2015, September)

Currently, the lack of robust, context-distributed subsurface greenhouses gases (GHG) concentrations data is a key bottleneck to reduce the uncertainty range of GHG groundwater input to continental ... [more ▼]

Currently, the lack of robust, context-distributed subsurface greenhouses gases (GHG) concentrations data is a key bottleneck to reduce the uncertainty range of GHG groundwater input to continental surface water bodies such as rivers or lakes estimates. Carbon dioxyde (CO2), methane (CH4) and nitrous oxyde (N2O) are likely to be indirectly transferred to the atmosphere through groundwater discharge into continental surface water bodies. We aim to extend regional-scale estimates of indirect GHG emissions by screening, in numerous hydrogeological (such as alluvial, sandstone, chalk and limestone aquifers) and land use contexts (such as industrial and agricultural), the occurence of these gases. Here, we report and discuss CO2, CH4 and N2O concentrations from an initial survey conducted over selected sites (n= 40) within shallow (0-100 m depth) aquifers in Wallonia (Belgium) for the first time. The preliminary results obtained in this study show that the range of GHG concentrations varies between 5160 and 47544 ppm, 0 and 1064 nmol.L-1, as well as 1 and 5637 nmol.L-1 for the partial pressure of CO2, CH4 and N2O respectively. This new and unique regional dataset provides a first step in developping a refined understanding of favorable contexts for GHG occurence in groundwater which may be used to reduce the uncertainties related to indirect emissions of GHG through groundwater-surface water transfers. [less ▲]

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