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See detailHydrogeological conditions required for Underground Pumping Storage Hydroelectricity (UPSH) in old mines
Bodeux, Sarah ULg; Pujades, Estanislao ULg; Orban, Philippe ULg et al

in Abstract book (2016, January 26)

Renewable energy sources, because of their intermittence, could not afford a stable production and an adequate variability according to the energy demand. Underground Pumped Storage Hydroelectricity (UPSH ... [more ▼]

Renewable energy sources, because of their intermittence, could not afford a stable production and an adequate variability according to the energy demand. Underground Pumped Storage Hydroelectricity (UPSH) using abandoned mine works is an interesting alternative, in flat regions, to store energy during low demand periods by pumping water from an underground mine to an upper reservoir. From the hydrogeological point of view, two considerations can arise for studying the feasibility before constructing an UPSH plant: 1) the alteration of the natural conditions of surrounding aquifers, and (2) the efficiency of the plant depending on possible leakage in the cavities from the hydrogeological environment. A potential old slate mine was selected through a multi-criterion method and its geometrical and hydrogeological characteristics are used to build a simple but typical model. With the help of the HFEMC approach implemented in the code SUFT3D (HEG-ULg), the groundwater flows are modelled for a representative cavity. Simulations of groundwater flow induced by a UPSH system are performed and the main variables are identified. Piezometric heads around the reservoir oscillate, the magnitude of the oscillations and the time to achieve a pseudo-steady state (magnitude and head reached during oscillations not varying anymore with time) depend on the boundaries, the parameters of the aquifer and the characteristics of the underground reservoir. The required hydrogeological conditions are deduced and a screening methodology can be proposed to assess the main impacts caused in aquifers by UPSH plants. Their efficiency regarding the water level evolution inside the reservoir is also considered accommodating the cyclic pumped storage schemes. [less ▲]

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See detailHow heterogeneity of the K-field influences a heat plume in a shallow alluvial aquifer: responses from a heat tracer test
Klepikova, Maria; Jamin, Pierre ULg; Orban, Philippe ULg et al

in Abstract book (2016, January 26)

Simultaneous solute and heat tracer test provides essential information for a reliable assessment of low temperature geothermal systems. The actual efficiency of ‘open systems’, including heat storage ... [more ▼]

Simultaneous solute and heat tracer test provides essential information for a reliable assessment of low temperature geothermal systems. The actual efficiency of ‘open systems’, including heat storage projects, is strongly affected by the heterogeneity of the hydraulic conductivity field (K-field). It could be also useful for assessing the cumulative impacts of numerous projects in urban areas on the groundwater resources. Using field data from a solute and heat tracer test conducted in the alluvial aquifer of the Meuse River (Belgium), an inverse problem of parameter estimation is solved. 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 plume, an arrangement of three transects 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 transport is a thermal diffusion dominated process. For conditions corresponding to high Peclet numbers, the hydraulic conductivity is the primary calibration parameter for predicting heat plume distribution. 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. [less ▲]

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See detailHeat tracer and solute tests in an alluvial aquifer: field experiment and inverse modelling
Dassargues, Alain ULg; Klepikova, Maria; Jamin, Pierre ULg 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 detailUnderground Pumped Storage Hydroelectricity using abandoned works (open pits and deep mines)
Pujades, Estanislao ULg; Willems, Thibault ULg; Bodeux, Sarah ULg et al

Conference (2015, December 15)

Pumped Storage Hydroelectricity (PSH) is a good alternative to increase the efficiency of power plants, which cannot regulate the amount of electricity generated according to the demand (wind, solar or ... [more ▼]

Pumped Storage Hydroelectricity (PSH) is a good alternative to increase the efficiency of power plants, which cannot regulate the amount of electricity generated according to the demand (wind, solar or even nuclear power plants). PSH plants, which consist in two reservoirs located at different heights (upper and lower), can store energy during low demand periods (pumping water from the lower to the upper reservoir) and generate electricity during the high demand peaks (falling water from the upper to the lower reservoir). Given that the two reservoirs must be located at different heights, PSH plants cannot be constructed in flat regions. Nevertheless, in these regions, an alternative could be to use abandoned underground works (open pits or deep mines) as lower reservoirs to construct Underground Pumped Storage Hydroelectricity (UPSH) plants. To select the best place to construct a plant, two considerations must be taken into account regarding the interaction between UPSH plants and groundwater: 1) the alteration of the natural conditions of aquifers and 2), the efficiency of the plant since the electricity generated depends on the hydraulic head inside the underground reservoir. Obviously, a detailed numerical model must be necessary before to select a location. However, a screening methodology to reject the most disadvantageous sites in a short period of time would be useful. Groundwater flow impacts caused by UPSH plants are analyzed numerically and the main variables involved in the groundwater evolution are identified. 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 “dynamic steady state” depend on the boundaries, the parameters of the aquifer and the characteristics of the underground reservoir. A screening methodology is proposed to assess the main impacts caused in aquifers by UPSH plants. Finally, the efficiency regarding the groundwater evolution inside the reservoir is determined. [less ▲]

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See detailUnderground Pumped Storage Hydroelectricity (UPSH) using abandoned works
Pujades, Estanislao ULg; Willems, Thibault ULg; Orban, Philippe ULg et al

Poster (2015, September 17)

Underground Pumped Storage Hydroelectricity (UPSH) using abandoned works is an interesting alternative to increase the efficiency of some power plants, which cannot regulate the amount of electricity ... [more ▼]

Underground Pumped Storage Hydroelectricity (UPSH) using abandoned works is an interesting alternative to increase the efficiency of some power plants, which cannot regulate the amount of electricity generated according to the demand. 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. Two considerations must be taken into account in order to construct an UPSH plant: 1) the alteration of the natural conditions of aquifers and 2), the efficiency of the plant, which depends on the hydraulic head inside the underground reservoir. Obviously, a detailed numerical model must be necessary to design a plant. However, a screening methodology to apply during the early stages of the design of a UPSH plant in order to reject the most disadvantageous sites in a short period of time would be useful. Groundwater flow impacts caused by UPSH plants are analyzed numerically and the main variables involved in the groundwater evolution are identified. 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. From the numerical study, a screening methodology, which is based on existing analytical procedures (solutions for large diameter wells, methodologies for cyclic pumpings and the image well theory), is proposed to assess the main impacts caused in aquifers by UPSH plants and their efficiency regarding the groundwater evolution inside the reservoir. The procedure can be applied in a relatively short period of time and is useful to select those appropriate sites to construct a UPSH plant. [less ▲]

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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 detailA hydrochemical - isotopic approach for assessing factors controlling the regional pollution of an urban aquifer
Gesels, Julie ULg; Orban, Philippe ULg; Popescu, Ileana-Cristina et al

Poster (2015, June 24)

The alluvial aquifer of the Meuse River is contaminated at regional scale in the urbanized and industrialized area of Liège in Belgium, in particular inorganics pollutants such as sulfate, nitrate and ... [more ▼]

The alluvial aquifer of the Meuse River is contaminated at regional scale in the urbanized and industrialized area of Liège in Belgium, in particular inorganics pollutants such as sulfate, nitrate and ammonium. The sources of those contaminants are numerous: brownfields, urban waste water, subsurface acid mine drainage from former coal mines, atmospheric deposits related to former pollutants emissions in the atmosphere ... Sulfate, nitrate and ammonium are both typical pollutants of the aquifer and tracers of the possible pollution sources. In the Water Framework Directive context, a detailed hydrogeochemical characterization of groundwater was performed. The aim is to determine the origin of the inorganic contaminations, the main processes contributing to poor groundwater quality and the spatial extent of the contaminations. A large hydrochemical sampling campaign was performed, based on 71 selected representative sampling locations, to better characterize the different vectors (end-members) of contamination of the alluvial aquifer and their respective contribution to groundwater contamination in the area. Groundwater samples were collected and analyzed for major and minor compounds and metallic trace elements. The analyses also include stable isotopes in water, sulfate, nitrate, ammonium, dissolved inorganic carbon, boron and strontium. Different hydrogeochemical approaches are combined to obtain a global understanding of the hydrogeochemical processes at regional scale. Hydrochemical interpretations are based on classical diagrams, spatial distribution maps, geochemical equations, multivariate statistics such as self-organizing maps and isotopic analyses. With this combined approach, the location of the contaminant sources and most contaminated sectors of the alluvial aquifer together with a better understanding of geochemical processes involved are obtained. Redox processes strongly influence the composition of groundwater, specifically for compounds degrading the quality of groundwater in the area (sulfate, nitrate and ammonium). The highest concentrations of sulfate can be associated with the post-mining stage in the acid mine drainage process. Various reactions involving nitrogen compounds have been identified and allow a better understanding of causes of high concentrations of ammonium and nitrate. Denitrification and sulphate reduction are also demonstrated based on isotopic ratios. [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 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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