References of "Dassargues, Alain"
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See detailOpen pits or deep mines used for Underground Pumped Storage Hydroelectricity (UPSH): impacts on groundwater exchanges
Pujades, Estanislao ULg; Willems, Thibault ULg; Orban, Philippe ULg et al

Poster (2015, July 08)

UPSH using abandoned works is an attractive alternative to improve the efficiency of power plants, which cannot regulate the amount of electricity generated according to the demand (wind, solar or nuclear ... [more ▼]

UPSH using abandoned works is an attractive alternative to improve the efficiency of power plants, which cannot regulate the amount of electricity generated according to the demand (wind, solar or nuclear). UPSH plants can store (pumping water from an underground to an upper reservoir) or produce energy (releasing water from an upper to an underground reservoir) during the low or high demand periods. However, it is mandatory to determine 1) the impacts caused on aquifers and 2) the role played by the aquifer characteristics in order to assess the suitability of UPSH plants. Numerical simulations are developed in order to ascertain the groundwater flow impacts and the variables involved in the process. Given the earlier stages of our study, results are obtained considering regular pumping-injection cycles and simplifying the shape of the mine/open pit. The most noticeable effect consists in an oscillation of the groundwater. The hydraulic head around which groundwater oscillates, the magnitude of the oscillations and the time to achieve a pseudo-steady state (magnitude and head reached during oscillations do not vary anymore with time) depend on the boundaries, the parameters of the aquifer and the characteristics of the underground reservoir. [less ▲]

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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 detailImpact des changements climatiques sur la principale réserve en eau souterraine alimentant la ville de Liège (Belgique)
Goderniaux, Pascal; Orban, Philippe ULg; Compère, Jean-Michel et al

in Des villes et des territoires sobres et sûrs, Synthèse des interventions (2015, June 02)

Le changement climatique amène de nouvelles 'pressions' sur les ressources en eaux de surface et souterraines dans de nombreuses zones du monde. Des travaux scientifiques sont nécessaires pour aider les ... [more ▼]

Le changement climatique amène de nouvelles 'pressions' sur les ressources en eaux de surface et souterraines dans de nombreuses zones du monde. Des travaux scientifiques sont nécessaires pour aider les gestionnaires de l'eau à planifier les changements futurs. Un générateur de climats transitoire sophistiqué est utilisé en combinaison avec une modélisation intégrée hydrologique (HydroGeoSphere) pour évaluer les impacts sur les ressources en eaux souterraines de façon probabiliste. Cette nouvelle méthodologie est appliquée pour l'aquifère crayeux de Hesbaye (bassin Geer en Belgique) qui est le principal réservoir d'eau souterraine pour l'alimentation de la ville de Liège. Les sources d'incertitude étudiées sont les suivantes: (1) l'incertitude liée à la calibration du modèle hydrologique, en utilisant 'UCODE_2005'; (2) l'incertitude liée aux modèles climatiques mondiaux et régionaux (GCM et RCM); (3) l'incertitude liée à la variabilité naturelle du climat, en utilisant des scénarios stochastiques de changement climatique locaux. 100 changements climatiques équiprobables scénarios ont été générés sur 2010-2085 pour chacun des six RMC différents. Les résultats montrent que bien que les intervalles de confiance à 95% calculés autour des niveaux piézométriques calculés restent importants, l'effet du changement climatique devient clair et plus prononcé que la variabilité naturelle du climat d'ici 2085. Cette méthodologie constitue une réelle amélioration dans le domaine des prévisions de l'évolution des réserves en eau souterraine dans des conditions de changement climatique car il permet aux gestionnaires d'analyser les risques et prendre des décisions en toute connaissance du degré de confiance des résultats. [less ▲]

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See detailLanduse change and future flood risk: an integrated and multi-scale approach
Dewals, Benjamin ULg; Bruwier, Martin ULg; Mohamed El Saeid Mustafa, Ahmed ULg et al

in E-proceedings of the 36th IAHR World Congress (2015, June)

The goal of this research is a better understanding of the complex interactions between landuse change and future flood risk. Landuse change is mainly driven by population growth and socio-economic ... [more ▼]

The goal of this research is a better understanding of the complex interactions between landuse change and future flood risk. Landuse change is mainly driven by population growth and socio-economic factors. It affects future flood risk by altering catchment hydrology and vulnerability in the floodplains, as well as through the feedback effect that changes in flood hazard may have on landuse evolution. The research is based on a chain of modelling tools, including: stochastic landuse change modelling, traffic modelling as well as Land-Use and Transport Interactions models, continuous hydrological modelling and efficient hydraulic modelling of floodplains inundation. The coupling of these modelling tools will allow assessing direct and indirect impacts of land use change on future flood risk, while considering the uncertainties related to each of these processes and their combinations at a 2100 time horizon. [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 detailFactors controlling Si export from soils: A soil column approach
Ronchi, Benedicta; Barao, Lucia; Clymans, Wim et al

in Catena (2015), 133

The release of dissolved silicon (DSi) from A and B horizons was investigated with leaching tests on unsaturated columns. As forest A horizons have larger biogenic Si (BSi) pools than arable lands, we ... [more ▼]

The release of dissolved silicon (DSi) from A and B horizons was investigated with leaching tests on unsaturated columns. As forest A horizons have larger biogenic Si (BSi) pools than arable lands, we compared the Si release from a forest and a cropland from the same geographical region developed on a Luvisol in Belgium and a Cambisol in Sweden. The A horizons released a quickly dissolving Si fraction in contrast to the B horizons, which did contain no or only little amounts of BSi and released lower Si concentrations. Our experiments show that Si export from forest soils is high because of the presence of a large reservoir of soluble BSi as well as due to the acidity of the soil (pH<4). Leaching at two different water fluxes revealed that export in forest soils was transport controlled while cropland soils were in equilibrium. [less ▲]

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See detailCarte hydrogéologique de Wallonie, Chastre - Gembloux 40/5-6
Ruthy, Ingrid ULg; Dassargues, Alain ULg

Cartographic material (2015)

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See detailCarte hydrogéologique de Wallonie, Reinartzhof – Hoscheit, 43/7-8
Gilson, Mylene; Briers, Pierre ULg; Ruthy, Ingrid ULg et al

Cartographic material (2015)

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See detailCarte hydrogéologique de Wallonie, Maffe - Grandhan 54/3-4
Ruthy, Ingrid ULg; Dassargues, Alain ULg

Cartographic material (2015)

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