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See detailInfluence of natural attenuation and river fluctuations on benzene dispersion in an alluvial aquifer subject to strong interactions with surface water
Batlle-Aguilar, Jordi; Brouyère, Serge ULg; Dassargues, Alain ULg et al

in Schirmer, M.; Hoehn, E.; Vogt, T. (Eds.) Groundwater Quality Management in a Rapidly Changing World (GQ'2010) (2010, June)

A contaminated alluvial aquifer, in a former gasworks factory, discharging to an adjacent river was the object of field and laboratory investigations to assess pollutant attenuation and dispersion ... [more ▼]

A contaminated alluvial aquifer, in a former gasworks factory, discharging to an adjacent river was the object of field and laboratory investigations to assess pollutant attenuation and dispersion. Various organic and inorganic compounds were found in the aquifer in concentrations exceeding regulatory values, among them, benzene, which was presenting the major worry for off-site dispersion, mainly due to its mobility and high concentration, i.e. up to 750 mg L-1 in the source zone. However, benzene could never be detected near the river which is about 160 m downgradient the main source. Due to redox conditions of the aquifer, heavy metals were almost immobile, thus not posing a major risk of dispersion off-site the brownfield. Benzene concentrations together with redox conditions in the aquifer, suggested that benzene degradation was mainly occurring within 100 m distance from the contaminant source under anoxic conditions, and most probably with sulphate as main oxidant. A numerical groundwater flow and transport model, calibrated under transient conditions, was used to simulate benzene attenuation in the alluvial aquifer towards the Meuse River. The mean benzene degradation rate used in the model was quantified in situ along the groundwater flow path using compound-specific carbon isotope analysis (CSIA). The results of the solute transport simulations confirmed that benzene concentrations decreased almost five orders of magnitude 70 m downgradient the source. Simulated benzene concentrations were found to be below the detection limit in the zone adjacent to the river and consistent with the absence of benzene in downgradient piezometers located close to the river. In a transient model scenario including groundwater-surface water dynamics, benzene concentrations were observed to be inversely correlated to the river water levels, leading to the hypothesis that benzene dispersion is mainly controlled by natural attenuation and river fluctuations. [less ▲]

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See detailA regional flux-based risk assessment approach of contaminated sites on groundwater bodies
Brouyère, Serge ULg; Jamin, Pierre ULg; Dollé, Fabien ULg et al

Poster (2010, April 22)

In the context of the water framework directive, management plans have to be set up about water quality in surface and groundwater bodies in the EU. One of the first steps is to evaluate the risk of ... [more ▼]

In the context of the water framework directive, management plans have to be set up about water quality in surface and groundwater bodies in the EU. One of the first steps is to evaluate the risk of contamination of these water resources, and particularly the risk posed by contaminated industrial sites. From the perspective of water resource management, each of these sites taken individually does not necessary constitute a major threat. However, in heavily industrialised and urbanised areas, the cumulative effect of multiple contaminant sources is likely to present a risk. In order to propose adequate but still economically reliable measures, the calculated risk should be based on a so-called megasite approaches using criteria reflecting the water quality deterioration, in a cumulative way, at the scale of the whole surface water or groundwater body. A GIS-based regional risk assessment approach is developed here for groundwater bodies using the SEQ-ESO currently used within the Walloon Region as indicator to reflect the quality status of the groundwater body. The approach is applied on the groundwater body RWM073 “Gravels and alluvial deposits of the Meuse river between Engis and Herstal”, identified at risk of not reaching a good quality status by 2015. The different steps of this methodology consist of an inventory of proved or potential contaminating industrial sites, a numerical modelling of pollutants behaviour at the scale of the groundwater body and the application of the SEQ-ESO that finally gives a global quality status of the whole groundwater body. This analysis also serves as basis for a socio-economic approach intending to provide indications on costs and benefits generated by total or partial remediation of the contaminated groundwater bodies according to the different management scenarios. [less ▲]

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See detailPhysically-based groundwater vulnerability assessment for groundwater protection and land-use management
Popescu, Ileana-Cristina; Brouyère, Serge ULg; Derouane, Johan et al

Poster (2010, April 22)

Numerous groundwater vulnerability and risk mapping techniques have been developed taking into consideration a variable number of factors. Most common techniques produce maps of indexes based on a ... [more ▼]

Numerous groundwater vulnerability and risk mapping techniques have been developed taking into consideration a variable number of factors. Most common techniques produce maps of indexes based on a relatively empirical combination of weighted factors reflecting the protective effect of underground formations overlying the groundwater resource. The limitation of such 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 physically-based point of view and definition of the vulnerability is proposed and based on three factors describing a pollution event, which are the contaminant transfer time from the hazard location to the 'target', the contamination duration at the 'target' and the level of contaminant concentration reached at the 'target'. This concept allows a clear distinction between conventional aspects and physically-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, such as karstic features. Practically, this method needs to describe and simulate the pollutant migration in the unsaturated zone and possibly in the saturated zone in order to assess the breakthrough curve at the 'target'. Preliminary application is illustrated on a case-study located in a Néblon limestone basin in Belgium, one of the main groundwater resources for the city of Liège in the Meuse basin. Perspectives are proposed towards a generalisation of the vulnerability concept for risk assessment within a pressure - state - impact framework. [less ▲]

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See detailDélivrable 16 (A) : Rapport intermédiaire global présentant les travaux réalisés et les résultats acquis à la date du 5 février 2010
Pereira, Benoît; Schneider, Arnaud; Titeux, Hugues et al

Report (2010)

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See detailMethodology and setup of the adopted groundwater vulnerability assessment method
Beaujean, Jean ULg; Lemieux, Jean-Michel; Brouyère, Serge ULg

Scientific conference (2010, February 04)

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See detailRegional transport modelling for nitrate trend assessment and forecasting in a chalk aquifer
Orban, Philippe ULg; Brouyère, Serge ULg; Batlle-Aguilar, Jordi et al

in Journal of Contaminant Hydrology (2010), 118

Regional degradation of groundwater resources by nitrate has become one of the main challenges for water managers worldwide. Regulations have been defined to reverse observed nitrate trends in groundwater ... [more ▼]

Regional degradation of groundwater resources by nitrate has become one of the main challenges for water managers worldwide. Regulations have been defined to reverse observed nitrate trends in groundwater bodies, such as the Water Framework Directive and the Groundwater Daughter Directive in the European Union. In such a context, one of the main challenges remains to develop efficient approaches for groundwater quality assessment at regional scale, including quantitative numerical modelling, as a decision support for groundwater management. A new approach combining the use of environmental tracers and the innovative ‘Hybrid Finite Element Mixing Cell’ (HFEMC) modelling technique is developed to study and forecast the groundwater quality at the regional scale, with an application to a regional chalk aquifer in the Geer basin in Belgium. Tritium data and nitrate time series are used to produce a conceptual model for regional groundwater flow and contaminant transport in the combined unsaturated and saturated zones of the chalk aquifer. This shows that the spatial distribution of the contamination in the Geer basin is essentially linked to the hydrodynamic conditions prevailing in the basin, more precisely to groundwater age and mixing and not to the spatial patterns of land use or local hydrodispersive processes. A three-dimensional regional scale groundwater flow and solute transport model is developed. It is able to reproduce the spatial patterns of tritium and nitrate and the observed nitrate trends in the chalk aquifer and it is used to predict the evolution of nitrate concentrations in the basin. The modelling application shows that the global inertia of groundwater quality is strong in the basin and trend reversal is not expected to occur before the 2015 deadline fixed by the European Water Framework Directive. The expected time required for trend reversal ranges between 5 and more than 50 years, depending on the location in the basin and the expected reduction in nitrate application. To reach a good chemical status, nitrate concentrations in the infiltrating water should be reduced as soon as possible below 50mg/l; however, even in that case, more than 50 years is needed to fully reverse upward trends. [less ▲]

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See detailHydroCube: a new entity-relationship hydrogeological data model
Wojda, Piotr; Brouyère, Serge ULg; Derouane, Johan et al

in Hydrogeology Journal (2010), 18(8), 1953-1962

Managing, handling, and accessing hydrogeological information depend mainly on the applied hydrogeological data models, which differ between institutions and across countries. Growing interest in ... [more ▼]

Managing, handling, and accessing hydrogeological information depend mainly on the applied hydrogeological data models, which differ between institutions and across countries. Growing interest in hydrogeological information diffusion, combined with a need for information availability, require the convergence of hydrogeological data models to make hydrogeological information accessible to multiple users such as universities, administrations, water suppliers, and research organisations. Furthermore, because hydrogeological studies are complex, they require a large variety of high-quality hydrogeological data with appropriate metadata in clearly designed and coherent structures. A need therefore exist to develop and implement hydrogeological data models that cover, as much as possible, the full hydrogeological domain. To respond to these requirements, a new data model, called HydroCube, has been developed for the Walloon Region in Belgium. The HydroCube model presents an innovative holistic “project-based” approach, which covers a full set of hydrogeological concepts and features, allowing for effective hydrogeological project management. This approach enables to store data about the project localisation, hydrogeological equipment, related observations and measurements. In particular, the model focuses on specialized hydrogeological field experiments, such as pumping and tracer tests. This logical data model uses entity-relationship diagrams and it has been implemented in the MS Access environment as the HydroCube database. It has been additionally enriched with a fully functional user-interface. [less ▲]

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See detailGeospatial Information in Hydrogeological Studies
Wojda, Piotr; Brouyère, Serge ULg; Dassargues, Alain ULg

in Anderson, M. G. (Ed.) Encyclopedia of Hydrological Sciences (2010)

The purpose of this article is to make a review of hydrogeological information modeling objectives, techniques, and problems, and finally to propose a solution for data integration and transfer ... [more ▼]

The purpose of this article is to make a review of hydrogeological information modeling objectives, techniques, and problems, and finally to propose a solution for data integration and transfer. Hydrogeological data and information management is crucial for efficient integrated water resources administration, protection, and exploitation. To assure an effective management of groundwater resources, a close cooperation and information exchange between different actors at different levels is necessary. The information flux must be optimized between local producers and potential users of hydrogeological data: regional and national institutions, as well as international and transboundary analysts and managers. The paper format of representation and exchange of hydrogeological information has already been replaced by different digital forms. However, an enormous diversity in applied formats and representations makes hydrogeological information extremely difficult to transfer in an automatic way. If this transition is not effective, misinterpretations of hydrogeological data may appear. The proposed solution consists in creating a domain-specific standard for the hydrogeological information exchange, using recent geomatics advances, taking into consideration appropriate ISO/TC211 and Open Geospatial Consortium (OGC) geographic information standards. Such a new electronic carrier of hydrogeological information facilitates a dialogue between interested parties using web services and inbuilt exchange mechanisms, interdisciplinary collaboration, and international harmonization of environmental sciences. [less ▲]

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See detailApplication of the Hybrid Finite Element Mixing Cell method to an abandoned coalfield in Belgium
Wildemeersch, Samuel ULg; Brouyère, Serge ULg; Orban, Philippe ULg et al

in Journal of Hydrology (2010), 392(3-4), 188-200

The Hybrid Finite Element Mixing Cell (HFEMC) method is a flexible modelling technique particularly suited to mining problems. The principle of this method is to subdivide the modelled zone into several ... [more ▼]

The Hybrid Finite Element Mixing Cell (HFEMC) method is a flexible modelling technique particularly suited to mining problems. The principle of this method is to subdivide the modelled zone into several subdomains and to select a specific equation, ranging from the simple linear reservoir equation to the groundwater flow in porous media equation, to model groundwater flow in each subdomain. The model can be run in transient conditions, which makes it a useful tool for managing mine closure post-issues such as groundwater rebound and water inrushes. The application of the HFEMC method to an abandoned underground coal mine near the city of Liege (Belgium) is presented. The case study zone has been discretized taking advantage of the flexibility of the method. Then, the model has been calibrated in transient conditions based on both hydraulic head and water discharge rate observation and an uncertainty analysis has been performed. Finally, the calibrated model has been used to run several scenarios in order to assess the impacts of possible future phenomena on the hydraulic heads and the water discharge rates. Among others, the simulation of an intense rainfall event shows a quick and strong increase in hydraulic heads in some zones coupled with an increase in associated water discharge rates. This could lead to stability problems in local hill slopes. These predictions will help managing and predicting mine water problems in this complex mining system. [less ▲]

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See detailMulti-tracer tests to evaluate the hydraulic setting of a complex aquifer system (Brévilles spring catchment, France)
Goderniaux, Pascal ULg; Brouyère, Serge ULg; Gutierrez, Alexis et al

in Hydrogeology Journal (2010)

For good management of groundwater resources, and to comply with European and national regulations, a detailed understanding of an aquifer’s hydraulic setting is required. In order to better characterize ... [more ▼]

For good management of groundwater resources, and to comply with European and national regulations, a detailed understanding of an aquifer’s hydraulic setting is required. In order to better characterize a sandy aquifer that is affected by diffuse pollution (Brévilles spring catchment, Val d'Oise, France), and to quantify the transfer time in the saturated zone, a multi-tracer test involving a new technique, the ‘Finite Volume Point Dilution Method’, has been performed in natural flow conditions. In November 2005, injections of four different tracers took place in four piezometers involving different locations and depths in the aquifer. Recovery of the tracers was observed at two different places near the aquifer outlet. A particularly long and unusual monitoring exercise (27 months) demonstrated the existence of several different velocities within the sandy layer, which seems to be linked to the decrease of hydraulic conductivity with depth. The new insight and parameter quantification brought by interpretation of these tests contribute to a better characterization of the saturated zone. The particularly long-term monitoring exercise also gives new information to understand and forecast the trend and persistence of groundwater contamination by pesticides in the catchment. [less ▲]

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See detailForeseeing nitrate concentration in groundwater: A review of available modelling approaches
Orban, Philippe ULg; Brouyère, Serge ULg

Conference (2009, December 10)

In the scientific community, increasing concerns on groundwater quality and quantity have motivated the development of numerical models for groundwater management since the 1970’s. Mathematical and ... [more ▼]

In the scientific community, increasing concerns on groundwater quality and quantity have motivated the development of numerical models for groundwater management since the 1970’s. Mathematical and numerical models are, for example, promising tools for prediction of concentration and they can be used to make the dynamic link between nitrogen manure and the resulting evolution of nitrate concentration in groundwater. However, from a practical and managerial perspective, there have been very few real attempts of developing efficient calibrated and validated transport models in particular at the scale of the groundwater body, which is the management unit of groundwater resource in the European Union. Actually two main challenges remains, (1) performing numerical tools are not really available and (2) parametrisation of such transport models at the regional scale is difficult due to the large amount of data required. Generally speaking models can be grouped in different categories ranging from black box models to physically based distributed models. The black box models such as transfer function are simple but attractive because they require relatively less data but with the drawback that modelling result are not spatially distributed while the predictive capability of these models is questionable due to the semi-analytical nature of the process descriptions. On the contrary, physically based distributed model require more data but, due to a more advanced description of ongoing processes, such models are expected to have better predictive capabilities than the black box models. Black box model and physically based distributed model approaches have all proved their utilities and have all their justifications, advantages and disadvantages regarding the development of regional scale groundwater model. A new flexible methodology (the Hybrid Finite Element Mixing Cell method) has been developed that allows combining in a single model, and in a fully integrated way, different mathematical approaches of various complexities for groundwater in complex environment. This method has been implemented in the SUFTD, a finite element groundwater flow and solute transport numerical model. Combining on the one hand the use of a spatially distributed groundwater flow and solute transport model taking advantages of this Hybrid Finite Element Mixing Cell Approach method and on the other hand spatial datasets of tritium and nitrate contents, an illustration on the problem of nitrate trend assessment and forecasting for an important groundwater resource located in the Geer groundwater body (480 km²) in the Walloon Region of Belgium will be proposed. [less ▲]

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See detailEtude et modélisation des tendances en nitrate au sein de l’aquifère crayeux du bassin du Geer en support à la mise en œuvre de la directive cadre sur l’eau
Orban, Philippe ULg; Batlle-Aguilar, Jordi; Goderniaux, Pascal et al

Scientific conference (2009, October 22)

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See detailApplication of the HFEMC method to an abandoned coalfield in Belgium: From conceptualisation to scenario simulations
Wildemeersch, Samuel ULg; Brouyère, Serge ULg; Orban, Philippe ULg et al

Conference (2009, October 20)

The Hybrid Finite Element Mixing Cell (HFEMC) method is a flexible modelling technique particularly suited to mining context (Brouyère et al., 2009). The principle of this method is to subdivide the ... [more ▼]

The Hybrid Finite Element Mixing Cell (HFEMC) method is a flexible modelling technique particularly suited to mining context (Brouyère et al., 2009). The principle of this method is to subdivide the modelled zone into several subdomains and to select a specific equation, ranging from the simple linear reservoir equation to the groundwater flow in porous media equation, to model groundwater flow in each subdomain. The model can be run in transient conditions, which makes it a useful tool for managing mine closure post-issues such as groundwater rebound and water inrushes. An application of the HFEMC method to an abandoned underground coal mine near the city of Liège (Belgium) is presented. The case study zone has been discretized taking advantage of the flexibility of the method. Then, the model has been calibrated in both steady-state and transient flow regimes based on hydraulic head and water discharge rate observations. Finally, the calibrated model has been used to run several scenarios in order to assess the impacts of possible future phenomena on the hydraulic heads and the water discharge rates. Among others, the simulation of a strong rainfall event shows a quick and strong increase in hydraulic heads in some exploited zones coupled with a strong increase in associated water discharge rates. This could lead to stability problems in the hill slopes near the exploited zones. This kind of predictions can greatly help managing and predicting mine water problems in this particularly complex mining system. [less ▲]

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See detailUsing Electrical Resistivity Tomography and Self-potential Methods for Wells Implementations in Fractured Limestones
Robert, Tanguy ULg; Dassargues, Alain ULg; Brouyère, Serge ULg et al

in EarthDoc - Near Surface 2009 – 15th European Meeting of Environmental and Engineering Geophysics (2009, September 09)

Electrical resistivity tomography (ERT) and self-potential (SP) investigations were conducted in fractured limestones in Belgium. The aim of this study was to find suitable positions for high yield water ... [more ▼]

Electrical resistivity tomography (ERT) and self-potential (SP) investigations were conducted in fractured limestones in Belgium. The aim of this study was to find suitable positions for high yield water wells. Large ERT profiles (640 meters) allowed us to image the resistivity distribution of the first 60 meters of the subsurface and to detect and characterize (in terms of direction, width and depth) fractured zones expected to be less resistive. Data errors, DOI indexes and sensitivity models were analysed in order to calculate the depth of investigation of ERT and to avoid the misinterpretation of the resulting images. Self-potential measurements were performed along electrical profiles to narrow the possible locations given by the electrical images. Some negative anomalies possibly related to preferential flow were detected. ‘Ground truth’ geological data as well as pumping tests information gave us a way to assess the contribution of geophysics to a drilling programme. Wells implemented in low resistivity zones associated with SP anomalies have very high yields. Inversely, wells drilled in resistive zones or outside SP anomalies have poorer capacities. An apparent coupling coefficient between SP signals and differences in hydraulic heads was also estimated in order to image the water table. [less ▲]

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See detailHow can large scale integrated surface - subsurface hydrological model be used to evaluate long term climate change impact on groundwater reserves
Goderniaux, Pascal ULg; Brouyère, Serge ULg; Fowler, Hayley J. et al

in Proceeding of the 7th international conference on calibration and reliability in groundwater modeling (2009, September)

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See detailDélivrable 9/10/12 (A) : Plan d'échantillonnage pour les prélèvements de sols, de légumes et d'eaux souterraines
Pereira, Benoît; Schneider, Arnaud; Sonnet, Philippe et al

Report (2009)

Detailed reference viewed: 5 (1 ULg)