References of "Brouyère, Serge"
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See detailAssessment of climate change effects on groundwater resource in transient conditions
Goderniaux, Pascal; Wildemeersch, Samuel; Brouyère, Serge ULg et al

Conference (2015, June 27)

A sophisticated transient weather generator (WG) in combination with an integrated surface-subsurface hydrological model (HydroGeoSphere) are used for producing a stochastic generation of large numbers of ... [more ▼]

A sophisticated transient weather generator (WG) in combination with an integrated surface-subsurface hydrological model (HydroGeoSphere) are used for producing a stochastic generation of large numbers of equiprobable climatic time series, representing transient climate change, and assess impacts on groundwater resources in a probabilistic way. The modelling approach, involving the catchment-scale fully integrated surface-subsurface model, is described in Goderniaux et al. [2009]. Biased-corrected climate change scenarios are applied as input of the hydrological model to quantify their impact on groundwater resources. In Goderniaux et al. [2011], the integrated model is used in combination with a stochastic daily weather generator (WG). This WG allowed generating a large number of equiprobable climate change scenarios representative of a full transient climate between 2010 and 2085. These scenarios enabled to account for the transient nature of the future climate change, and to assess the uncertainty related to the weather natural variability. The downscaling method considers changes in the climatic means, but also in the distribution of wet and dry days. This new methodology is applied for the unconfined chalky aquifer of the Geer catchment in Belgium. A general decrease of the mean groundwater piezometric heads, has been calculated. The approach allowed also to assess different uncertainty sources: (1) the uncertainty linked to the calibration of the hydrological model, using 'UCODE_2005'; (2) the uncertainty linked to the global and regional climatic models (GCMs and RCMs), by using a multi-model ensemble; (3) the uncertainty linked to the natural variability of the weather, by using stochastic climate change scenarios. 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. The WG ability to simulate transient climate change enabled the assessment of the likely timescale and associated uncertainty of a specific impact. This methodology constitutes a real improvement in the field of groundwater projections under transient climate change conditions as it enables water managers to analyse risks and take decisions with full knowledge of projected impact and their degree of confidence. [less ▲]

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See detailUncertainty of climate change impact on groundwater reserves – Application to a chalk aquifer
Goderniaux, Pascal; Brouyère, Serge ULg; Wildemeersch, Samuel et al

in Journal of Hydrology (2015), 528

Recent studies have evaluated the impact of climate change on groundwater resources for different geographical and climatic contexts. However, most studies have either not estimated the uncertainty around ... [more ▼]

Recent studies have evaluated the impact of climate change on groundwater resources for different geographical and climatic contexts. However, most studies have either not estimated the uncertainty around projected impacts or have limited the analysis to the uncertainty related to climate models. In this study, the uncertainties around impact projections from several sources (climate models, natural variability of the weather, hydrological model calibration) are calculated and compared for the Geer catchment (465 km2) in Belgium. We use a surface–subsurface integrated model implemented using the finite element code HydroGeoSphere, coupled with climate change scenarios (2010–2085) and the UCODE_2005 inverse model, to assess the uncertainty related to the calibration of the hydrological model. This integrated model provides a more realistic representation of the water exchanges between surface and subsurface domains and constrains more the calibration with the use of both surface and subsurface observed data. Sensitivity and uncertainty analyses were performed on predictions. The linear uncertainty analysis is approximate for this nonlinear system, but it provides some measure of uncertainty for computationally demanding models. Results show that, for the Geer catchment, the most important uncertainty is related to calibration of the hydrological model. The total uncertainty associated with the prediction of groundwater levels remains large. By the end of the century, however, the uncertainty becomes smaller than the predicted decline in groundwater levels. [less ▲]

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See detailUse and utility of combined solute and heat tracer tests for characterizing hydrogeothermal properties of an alluvial aquifer
Klepikova, Maria; Wildemeersch, Samuel; Jamin, Pierre ULg et al

Conference (2015, June 05)

Using heat as a tracer together with a solute tracer is interesting for characterizing hydrogeothermal properties of the underground. These properties are particularly needed to dimension any low ... [more ▼]

Using heat as a tracer together with a solute tracer is interesting for characterizing hydrogeothermal properties of the underground. These properties are particularly needed to dimension any low temperature geothermal project using an open doublet system (pumping-reinjection) in a shallow aquifer. The tracing experiment, conducted in the alluvial aquifer of the River Meuse (Hermalle near Liège), consisted in injecting simultaneously heated water at 40°C and a dye tracer in a piezometer and monitoring the evolution of temperature and tracer concentration in the recovery well and in nine monitoring piezometers located in three transects with regards to the main groundwater flow direction. The breakthrough curves measured in the recovery well showed that heat transfer in the alluvial aquifer is slower. All measured results show also that the heat diffusivity is larger than the solute dispersion. These contrasted behaviours are stressed in the lower permeability zones of the aquifer. Inverse modelling is applied for calibrating the numerical simulation of the groundwater flow, heat and solute transport. First results are presented showing that the density effect must be taken into account and that, as expected, the most important parameter to be calibrated accurately is the hydraulic conductivity. [less ▲]

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See detailModélisation de la remontée des eaux dans les anciennes mines de charbon : un outil pour détecter les seuils de risques d’inondation en plaine alluviale de la Meuse près de Liège (Belgique)
Dassargues, Alain ULg; Wildemeersch, Samuel; Orban, Philippe ULg et al

in Des villes et des territoires sobres et sûrs, Synthèse des interventions (2015, June 03)

La plaine alluviale de la Meuse occupe la partie centrale du bassin charbonnier de Liège. Durant les exploitations minières, les niveaux d’eau des aquifères avaient été rabattus par des pompages d’exhaure ... [more ▼]

La plaine alluviale de la Meuse occupe la partie centrale du bassin charbonnier de Liège. Durant les exploitations minières, les niveaux d’eau des aquifères avaient été rabattus par des pompages d’exhaure. Des galeries d’exhaure creusées à partir des pieds de versant dans la vallée de la Meuse contribuaient également à dénoyer le gisement. La fermeture des dernières exploitations minières durant les années 70 et 80 a été le plus souvent assortie d’un arrêt des opérations de pompage qui y sont associées. Ceci a induit une remontée significative des eaux souterraines avec des conséquences indésirables possibles. Les modèles hydrogéologiques peuvent grandement aider à simuler les écoulements des eaux souterraines dans le contexte particulier des travaux miniers. Cependant, les techniques de modélisation classiques ne sont pas adaptées à ce contexte car le milieu est fortement perturbé par les anciens travaux et les réseaux de galeries. Par conséquent, des techniques de modélisation spécifiques ont été développées. Il s'agit d'une combinaison de modèles de boîte (ne nécessitant que quelques paramètres) pour calculer les niveaux d'eau moyens dans les zones exploitées, avec une modélisation physiquement basée et spatialement distribuée représentant explicitement les zones inexploitées et prenant en compte les interactions entre ces deux sous-domaines. Grâce à ce couplage, les échanges d'eau entre les zones exploitées et inexploitées sont explicitement pris en compte. La méthode permet de simuler la remontée des eaux souterraines après la fermeture des mines et des phénomènes associés tels que les 'coups d'eau' produits par les galeries drainantes. Les concepts et équations de la méthode sont présentés et illustrés sur des cas synthétiques, puis sur l'application de la zone de Cheratte-Blégny. [less ▲]

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See detailSensitivity and vulnerability to groundwater overexploitation by a ‘pressure state impact’ and process based approach
Beaujean, Jean; Lemieux, Jean-Michel; Therrien, René et al

Conference (2015, May 26)

A methodology is developed for proposing a groundwater vulnerability assessment in a Pressure-State-Impact causal chain that is familiar to decision makers. The ‘Driver Pressure State Impact Response’ ... [more ▼]

A methodology is developed for proposing a groundwater vulnerability assessment in a Pressure-State-Impact causal chain that is familiar to decision makers. The ‘Driver Pressure State Impact Response’ (DPSIR) framework, for describing interactions between society and the environment, defines a chain of Drivers that exert Pressures on the State of a given resource, such as groundwater, which then generates an Impact that will require an appropriate Response (Kristensen, 2004). 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. These sensitivity coefficients reflect the easiness with which the groundwater state transmits pressures into impacts. They are grouped into a vulnerability matrix of pressures and impacts that quantify vulnerability for every combination of causal links identified in the DPSIR chain. For that reason, the sensitivity coefficients are converted to vulnerability, using the concept of ‘transgressing a given threshold’, which is commonly used in socioeconomic sciences (Luers et al. 2003). The concept of ‘rising above a given concentration threshold’ can be used for groundwater quality issues. The concept of ‘falling below a given piezometric head threshold’ can be used for groundwater quantity issues as aquifer overexploitation problems. Outside the careful selection of the sensitivity analysis method that can significantly influence the computational effort (Beaujean et al., 2013), emphasis is given to the illustration of the general methodology on a simple groundwater quantity case (of an alluvial aquifer with concerns related to water supply) demonstrating the potential use of this general and physically based vulnerability assessment method. While the methodology is general, 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. This choice is arbitrary such that the vulnerability is sensitive to the choice of the threshold. [less ▲]

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See detailProcess-based method for groundwater resource vulnerability mapping with regards to solute contamination at the surface
Popescu, Cristina; Brouyère, Serge ULg; Orban, Philippe ULg et al

Conference (2015, May 26)

Numerous groundwater vulnerability methods have been developed taking into consideration a variable number of factors. The most common techniques are based on calculation of an index expressing the ... [more ▼]

Numerous groundwater vulnerability methods have been developed taking into consideration a variable number of factors. The most common techniques are based on calculation of an index expressing the protective effect of underground formations overlying the groundwater resource. However, it has been shown that different overlay and index methods applied to the same system can yield dramatically dissimilar results (among others, Gogu et al., 2003). The limitation of most of these methods is related to their use of a qualitative definition of groundwater vulnerability, as opposed to a definition based on a quantitative description of contaminant migration. A process-based point of view is proposed and 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 assessment can then be based on the impulse response at the ‘target’ to a Dirac-type solicitation (point, unit mass, instantaneous source of pollution), considering only physical hydrodispersive processes for intrinsic vulnerability and both physical and biochemical processes for specific vulnerability. The breakthrough curve obtained after a vertical transfer through the overlying layers can be computed pixel by pixel. Automatically processing the columns with identical characteristics, 1D partially saturated flow and solute transport computations are performed. Different maps are obtained for the three above mentioned factors. On the basis of these results, different vulnerability maps can be built according to the weighting coefficients agreed by the local community or decision makers. This concept allows a clear distinction between conventional aspects and process-based results in the building of a final vulnerability indicator. This methodology has the further advantage to consider the possible impact of runoff conditions occurring at the land surface and possibly leading to lateral contamination of groundwater through downstream preferential infiltration features. To solve this problem, Popescu et al. (2004 & 2008) and Dassargues et al. (2009) proposed a method for quantifying a lateral “dangerosity” coefficient using runoff coefficients based on land use, slopes, and soil properties. A test application is illustrated on a case-study located in a limestone basin in Belgium. [less ▲]

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See detailQuantitative temperature monitoring of a heat tracing experiment using cross-borehole ERT
Hermans, Thomas ULg; Wildemeersch, Samuel ULg; Jamin, Pierre ULg et al

in Geothermics (2015), 53

The growing demand for renewable energy leads to an increase in the development of geothermal energy projects and heat has become a common tracer in hydrology and hydrogeology. Designing geothermal ... [more ▼]

The growing demand for renewable energy leads to an increase in the development of geothermal energy projects and heat has become a common tracer in hydrology and hydrogeology. Designing geothermal systems requires a multidisciplinary approach including geological and hydrogeological aspects. In this context, electrical resistivity tomography (ERT) can bring relevant, qualitative and quantitative information on the temperature distribution in operating shallow geothermal systems or during heat tracing experiments. We followed a heat tracing experiment in an alluvial aquifer using cross-borehole time-lapse ERT. Heated water was injected in a well while water of the aquifer was extracted at another well. An ERT section was set up across the main flow direction. The results of ERT were transformed into temperature using calibrated petrophysical relationships. These ERT-derived temperatures were then compared to direct temperature measurements in control piezometers collected with distributed temperature sensing (DTS) and groundwater temperature loggers. Spatially, it enabled to map the horizontal and vertical extent of the heated water plume, as well as the zones where maximum temperatures occurred. Quantitatively, the temperatures and breakthrough curves estimated from ERT were in good agreement with the ones observed directly during the rise and maximum of the curve. An overestimation, likely related to 3D effects, was observed for the tail of the heat breakthrough curve. The error made on temperature can be estimated to be between 10 to 20 %, which is a fair value for indirect measurements. From our data, we estimated a quantification threshold for temperature variation of 1.2°C. These results suggest that ERT should be considered when designing heat tracing experiments or geothermal systems. It could help also to assess the geometrical complexity of the concerned reservoirs. It also appears that ERT could be a useful tool to monitor and control geothermal systems once they are in operation. [less ▲]

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See detailCharacterization of stream - aquifer interaction in carbonate rocks
Briers, Pierre ULg; Sohier, Catherine ULg; Schmit, Flore et al

Poster (2014, September 30)

Groundwater - surface water interactions play a fundamental role in terms of quantity and quality of water and in terms of ecological quality of rivers. Despite many research efforts and the necessity to ... [more ▼]

Groundwater - surface water interactions play a fundamental role in terms of quantity and quality of water and in terms of ecological quality of rivers. Despite many research efforts and the necessity to better understand such interactions in order to reach effective management of water resources, stream-aquifer exchanges remain poorly understood, in particular in fractured carbonate environments. [less ▲]

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See detailA heat and dye tracer test for characterizing and modelling heat transfer in an alluvial aquifer
Klepikova, Maria ULg; Wildemeersch, Samuel; Jamin, Pierre ULg et al

Poster (2014, September 22)

Using heat as an active tracer is a topic of increasing interest with regards to characterizing shallow aquifers for ATES (Aquifer Thermal Energy Storage) systems. In this study, we investigate the ... [more ▼]

Using heat as an active tracer is a topic of increasing interest with regards to characterizing shallow aquifers for ATES (Aquifer Thermal Energy Storage) systems. In this study, we investigate the potential interest of coupling simultaneous heat and dye tracer injection tests for characterization of an alluvial aquifer. The study site is located near Liege 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 nine monitoring wells located according to three transects with regards to the main groundwater flow direction. 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 shows how 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. In a first step, temperature and concentrations in the recovery well are used for estimating the specific heat capacity with an energy balance calculation and the estimated value is found to be consistent with those found in the literature. Then, the measured temperature breakthrough curves in the piezometers are used for constraining the heat transport model. They are highly contrasted with what would be expected in an ideal layered aquifer. They reveal strongly unequal lateral and vertical components of the transport mechanisms. A preliminary interpretation of these temperature breakthrough curves is provided with first results from the model. Then it will allow for estimating the entire set of heat transfer parameters and their spatial distribution by inverse modelling. The developed concepts and tests may lead to real projects of various extents that can be now optimized by the use of a rigorous and efficient methodology at the field scale. [less ▲]

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See detailDevelopping a physically based groundwater vulnerability concept in a DPSIR framework
Beaujean, Jean ULg; Brouyère, Serge ULg; Lemieux, Jean-Michel et al

Conference (2014, September 15)

A general physically based method is presented to assess vulnerability of groundwater to external pressures with respect to quality and/or quantity issues. In the vulnerability assessments, many ... [more ▼]

A general physically based method is presented to assess vulnerability of groundwater to external pressures with respect to quality and/or quantity issues. In the vulnerability assessments, many scientific authors agree nowadays that ‘physically based’ methods must be preferred to traditional approaches based on empirical overlay and index methods where physical attributes are often mixed with implicitly embedded conventional priorities. Results from one or another of these last methods can consequently be very dissimilar for a given case study and decision makers are losing confidence in these tools. A methodology is proposed to reframe the groundwater vulnerability assessment in a Pressure-State-Impact causal chain that is familiar to decision makers. The DPSIR framework, for describing interactions between society and the environment, defines a chain of Drivers that exert Pressures on the State of a given resource, such as water, which then generates an Impact that will require an appropriate Response (Kristensen, 2004). The concept of groundwater vulnerability assessment considered here is based on the calculation of sensitivity coefficients for a user-defined groundwater state for which several physically-based indicators are proposed. These sensitivity coefficients reflect the easiness with which the groundwater state transmits pressures into impacts. They are grouped into a vulnerability matrix of pressures and impacts that quantify vulnerability for every combination of causal links identified in the DPSIR chain. For that reason, the sensitivity coefficients are converted to vulnerability, using the concept of ‘falling below a given threshold’, which is commonly used in socioeconomic sciences (Luers et al. 2003). Outside the careful selection of the sensitivity analysis method that can significantly influence the computational effort (Beaujean et al., 2013), emphasis will be given to the illustration of the general methodology on a simple case (of an alluvial aquifer with concerns related to water supply) demonstrating the potential use of this general and physically based vulnerability assessment method. While the methodology is general, 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. This choice is arbitrary such that the vulnerability is sensitive to the choice of the threshold. The framework is general and, when applied to water, can include states that are not limited to quality such as, for example, water quantity and availability. [less ▲]

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See detailVADOSE ZONE STUDIES AT AN INDUSTRIAL CONTAMINATED SITE: THE VADOSE ZONE MONITORING SYSTEM AND CROSS-HOLE GEOPHYSICS
Fernandez de Vera, Natalia ULg; Beaujean, Jean ULg; Jamin, Pierre ULg et al

Conference (2014, September 03)

In situ vadose zone characterization is essential to improve risk characterization and remediation measures for soil and groundwater contamination. However, most available technologies have been developed ... [more ▼]

In situ vadose zone characterization is essential to improve risk characterization and remediation measures for soil and groundwater contamination. However, most available technologies have been developed in the context of agricultural soils. Most of these methodologies are not applicable at industrial sites, where soils and contamination differ in origin and composition. In addition, they are applicable only in the first meters of soils, leaving deeper vadose zones with lack of information, in particular on field scale heterogeneity. To overcome such difficulties, a vadose zone experiment has been setup at a former industrial site in Belgium. Industrial activities carried out on site left a legacy of soil and groundwater contamination in BTEX, PAH, cyanide and heavy metals. The experiment involves the combination of two techniques: the Vadose Zone Monitoring System (VMS) and cross-hole geophysics. The VMS allows continuous measurements of water content at different depths of the vadose zone (Dahan et al., 2009). In addition, it provides the possibility of pore water sampling at different depths. The system is formed by a flexible sleeve installed in a slanted borehole (Fig. 1) and containing monitoring units along its depth (Fig. 2). The flexible sleeve contains three types of monitoring units in the vadose zone: Time Domain Transmissometry (TDT), which allows water content measurements; Vadose Sampling Ports (VSP), used for collecting water samples coming from the matrix; and the Fracture Samplers (FS), which are used for retrieving water samples from the fractures. Cross-hole electrical tomography measurements are carried providing detailed spatial patterns about electrical properties of the subsurface. Such properties are related with subsurface heterogeneities, water content and solute concentrations. Two VMS were installed on site, together with four vertical boreholes containing electrodes for geophysical measurements. The site has been monitored under natural recharge conditions during the summer, autumn and winter. Results show reactions in the soil at depths up to 6m as a consequence of rainfall infiltration and groundwater level fluctuations. In addition, the chemistry of the soil water changes with depth and water infiltration. Background images obtained from geophysical measurements show a highly conductive subsurface due to the lithologies and the high mineralization of the water in the vadose zone. The combination of cross-hole geophysics with the VMS has provided an effective tool for characterizing the chemistry and the structure of the vadose zone. [less ▲]

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See detailAquifère crayeux de Hesbaye
Orban, Philippe ULg; Brouyère, Serge ULg; Compère, Jean-michel et al

in Dassargues, Alain; Walraevens, Kristine (Eds.) Watervoerende lagen en grondwater in Belgïe - Aquifères et eaux souterraines en Belgique (2014)

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See detailRemontées des nappes dans les anciens travaux miniers et activités de démergement - Modélisation hydrogéologique spécifique et exemple de la zone minière de Cheratte
Dassargues, Alain ULg; Wildemeersch, Samuel ULg; Orban, Philippe ULg et al

in Dassargues, Alain; Walraevens, Kristine (Eds.) Watervoerende lagen & grondwater in Belgïe – Aquifères & eaux souterraines en Belgique (2014)

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See detailCalcaires et grès du Synclinorium de Dinant
Gesels, Julie ULg; Nogarède, Pierre; Hallet, Vincent et al

in Dassargues, Alain; Walraevens, Kristine (Eds.) Watervoerende lagen en grondwater in Belgïe - Aquifères et eaux souterraines en Belgique (2014)

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See detailVadose zone studies at an industrial contaminated site: the vadose zone monitoring system and cross-hole geophysics
Fernandez de Vera, Natalia ULg; Beaujean, Jean ULg; Jamin, Pierre ULg et al

Poster (2014, April 29)

Poster presented at the European Geoscience Union General Assembly 2014. In this poster, the installation of the vadose zone experimental set up is presented along with first results

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