References of "Brouyère, Serge"
     in
Bookmark and Share    
Full Text
Peer Reviewed
See detailDirect measurement of groundwater flux in aquifers within the discontinuous permafrost zone: an application of the finite volume point dilution method near Umiujaq (Nunavik, Canada)
Jamin, Pierre ULiege; Cochand, Marion; Dagenais, Sophie et al

in Hydrogeology Journal (in press)

Permafrost thaw is a complex process resulting from interactions between the atmosphere, soil, water and vegetation. Although advective heat transport by groundwater at depth likely plays a significant ... [more ▼]

Permafrost thaw is a complex process resulting from interactions between the atmosphere, soil, water and vegetation. Although advective heat transport by groundwater at depth likely plays a significant role in permafrost dynamics at many sites, there is lack of direct measurements of groundwater flow patterns and fluxes in such cold-region environments. Here, the finite volume point dilution method (FVPDM) is used to measure in-situ groundwater fluxes in two sandy aquifers in the discontinuous permafrost zone, within a small watershed near Umiujaq, Nunavik (Quebec), Canada. The FVPDM theory is first reviewed, then results from four FVPDM tests are presented: one test in a shallow supra-permafrost aquifer, and three in a deeper sub-permafrost aquifer. Apparent Darcy fluxes derived from the FVPDM tests varied from 0.5×10-5 to 1.0×10-5 m/s, implying that advective heat transport from groundwater flow could be contributing to rapid permafrost thaw at this site. In providing estimates of the Darcy fluxes at the local scale of the well screens, the approach offers more accurate and direct measurements over indirect estimates using Darcy’s law. The tests show that this method can be successfully used in remote areas and with limited resources. Recommendations for optimizing the test protocol are proposed. [less ▲]

Detailed reference viewed: 53 (12 ULiège)
Full Text
See detailDegradation mechanisms of chlorinated solvents in groundwater - Application in fractured chalk formation
Boudjana, Youcef ULiege; Brouyère, Serge ULiege; Dassargues, Alain ULiege

Poster (2019, February 18)

At an abandoned industrial site in Belgium, groundwater quality in a chalky aquifer had been impacted by a mixture of chlorinated aliphatic hydrocarbons inducing a significant change in hydrochemistry ... [more ▼]

At an abandoned industrial site in Belgium, groundwater quality in a chalky aquifer had been impacted by a mixture of chlorinated aliphatic hydrocarbons inducing a significant change in hydrochemistry.Based on this case study, the aim of the thesis is to study transport and attenuation mechanisms of chlorinated solvents in the subsurface, considering their effects on the chemistry of the groundwater. The first part is devoted to analyze and interpret the collected data on the contaminated site. It allows to improve our understanding of the processes governing the reactive transport and especially the degradation of aliphatic organochlorines as observed on the site. The influence on the hydrochemistry of groundwater in the vicinity of the study area is studied. In a second part of the research, the use of a numerical model simulating groundwater flow and reactive transport for chlorinated solvents will improve our understanding and clarify the main attenuation mechanisms and their impact on the groundwater chemical composition. [less ▲]

Detailed reference viewed: 21 (5 ULiège)
Full Text
Peer Reviewed
See detailDynamics of greenhouse gases in groundwater: hydrogeological and hydrogeochemical controls
Nikolenko, Olha ULiege; Orban, Philippe ULiege; Jurado, Anna et al

in Applied Geochemistry (2019), 105

In this study the variability of greenhouse gases (GHGs) concentrations along lateral and vertical dimensions of the chalk aquifer located in the eastern part of Belgium was examined in order to ... [more ▼]

In this study the variability of greenhouse gases (GHGs) concentrations along lateral and vertical dimensions of the chalk aquifer located in the eastern part of Belgium was examined in order to understand its dependence on hydrogeological and hydrogeochemical conditions. Groundwater samples from 29 wells/piezometers were analyzed for concentrations of nitrous oxide (N2O), carbon dioxide (CO2), methane (CH4), major and minor elements and stable isotopes of nitrate (NO3−), nitrous oxide (N2O), sulfate (SO42−) and boron (B). For lateral investigations, four zones with different environmental settings were identified (southern, central, north-eastern and northern). Groundwater was oversaturated with GHGs with respect to its equilibrium concentrations with the atmosphere in all zones, except the northern one, undersaturated in N2O (0.07 ± 0.08 μgN/L vs. 0.3 μgN/L). Vertical dimension studies showed the decrease in CO2 concentration and significant changes in both isotope signatures and concentration of N2O with depth. The production of N2O could be attributed to a combination of nitrification and denitrification processes occurring at different depths. CO2 concentration is controlled by the process of dissolution of carbonate minerals which constitute aquifer geology. CH4 is produced due to methanogenesis in deeper parts of the aquifer, though its thermogenic origin is also possible. Differences in hydrogeochemical settings and changing intensity of biogeochemical processes across the area and with depth have considerable effect on GHGs concentrations. Thus, before estimating GHGs fluxes at the groundwater–river interface insights obtained from larger-scale investigations are required in order to identify the representative spatial zones which govern GHGs emissions. [less ▲]

Detailed reference viewed: 28 (13 ULiège)
Full Text
Peer Reviewed
See detailAkvaGIS: An open source tool for water quantity and quality management
Criollo, Rotman; Velasco, Violeta; Nardi, Albert et al

in Computers & Geosciences (2019), 127

AkvaGIS is a novel, free and open source module included in the FREEWAT plugin for QGIS that supplies a standardized and easy-to-use workflow for the storage, management, visualization and analysis of ... [more ▼]

AkvaGIS is a novel, free and open source module included in the FREEWAT plugin for QGIS that supplies a standardized and easy-to-use workflow for the storage, management, visualization and analysis of hydrochemical and hydrogeological data. The main application is devised to simplify the characterization of groundwater bodies for the purpose of building rigorous and data-based environmental conceptual models (as required in Europe by the Water Framework Directive). For data-based groundwater management, AkvaGIS can be used to prepare input files for most groundwater flow numerical models in all of the available formats in QGIS. AkvaGIS is applied in the Walloon Region (Belgium) to demonstrate its functionalities. The results support a better understanding of the hydrochemical relationship among aquifers in the region and can be used as a baseline for the development of new analyses, e.g., further delineation of nitrate vulnerable zones and management of the monitoring network to control chemical spatial and temporal evolution. AkvaGIS can be expanded and adapted for further environmental applications as the FREEWAT community grows. [less ▲]

Detailed reference viewed: 22 (3 ULiège)
Full Text
Peer Reviewed
See detailTowards a subsurface predictive-model environment to simulate aquifer thermal energy storage for demand-side management applications
Robert, Tanguy ULiege; Hermans, Thomas ULiege; Lesparre, Nolwenn et al

in Proceedings of SSB 2018, 10th International Conference on System Simulation in Buildings (2018, December 12)

Detailed reference viewed: 27 (6 ULiège)
Full Text
Peer Reviewed
See detailMonitoring transient groundwater fluxes using the Finite Volume Point Dilution Method
Jamin, Pierre ULiege; Brouyère, Serge ULiege

in Journal of Contaminant Hydrology (2018), 218

Classic estimates of groundwater fluxes are usually based on the application of Darcy's law, which can lead to large imprecisions in transient groundwater flow cases. There is a need for direct, in situ ... [more ▼]

Classic estimates of groundwater fluxes are usually based on the application of Darcy's law, which can lead to large imprecisions in transient groundwater flow cases. There is a need for direct, in situ measurement techniques able to monitor time-variable groundwater fluxes. The investigation presented here demonstrates that the Finite Volume Point Dilution Method (FVPDM) is a promising technique for the continuous monitoring of groundwater fluxes. The experimental configuration consisted of monitoring transient groundwater fluxes generated by a multiple step pumping test, which was undertaken in the alluvial aquifer of the River Meuse, Liège (Belgium). Additionally, two FVPDM tests were simultaneously performed in two piezometers screened at two different depths in the alluvial aquifer. Tracer concentration changes during the FVPDM tests were interpreted as the consequences of Darcy flux changes in the alluvial aquifer, which was related to changes in the applied pumping rate. Piezometric levels were also monitored in piezometers located around the pumping well. The pumping test was interpreted using classical analytical solutions, and the FVPDM tests were interpreted using a new mathematical solution, which allows for calculating changes in Darcy fluxes based on the FVPDM tracer concentration evolution during transient groundwater flow conditions. The experiment demonstrated the FVPDM's ability to monitor, as well as be sensitive to changes in transient groundwater fluxes. The FVPDM interpretation also showed contrasting results between the upper part of the aquifer, which is made of loam and sand and slow groundwater flows prevail, and the lower part of the aquifer, which is made of gravels and pebbles and intense groundwater flows prevail. [less ▲]

Detailed reference viewed: 65 (18 ULiège)
See detailCaractérisation des eaux souterraines par des approches centrées sur les flux : concepts et applications
Brouyère, Serge ULiege; Jamin, Pierre ULiege

Conference (2018, September 20)

Les procédures les plus courantes visant à définir l’état pollué des eaux souterraines reposent sur des mesures de concentrations en polluants en différents points d’accès à la nappe. Cette manière de ... [more ▼]

Les procédures les plus courantes visant à définir l’état pollué des eaux souterraines reposent sur des mesures de concentrations en polluants en différents points d’accès à la nappe. Cette manière de procéder est relativement simple et, si le réseau d’échantillonnage est suffisamment dense, elle permet assez rapidement de cartographier l’étendue de la pollution et de comparer cet état pollué aux normes sanitaires et environnementales en vigueur. Cependant, les polluants se déplacent dans et avec l’eau souterraine. Mettre en évidence et quantifier ces flux de polluants est essentiel pour établir le diagnostic de l’état pollué, tant dans sa compréhension générale que pour évaluer les risques potentiels pour les récepteurs exposés et pour dimensionner correctement le plan d’assainissement. Dans ce contexte, l’objectif de l’exposé est dans un premier temp de revenir sur les concepts de base des approches de caractérisation de l’eau souterraine centrées sur les flux de polluants et comment elles s’articulent et complètent celles qui sont centrées sur les concentrations en polluants, aux différents stades des études de pollution des eaux souterraines (caractérisation, étude de risque et plan d’assainissement). Dans un deuxième temps, différentes techniques d’investigation et de mesure des flux de polluants dans les eaux souterraines seront décrites et illustrées par des exemples pour en tirer quelques perspectives en matière de caractérisation de l’état pollué des eaux souterraines. [less ▲]

Detailed reference viewed: 48 (2 ULiège)
Full Text
See detailGeothermal use of old mines: hydrogeological challenges for predicting efficiency and impacts
Vopat, Olivier; Orban, Philippe ULiege; Brouyère, Serge ULiege et al

Conference (2018, September 14)

Groundwater in flooded abandoned mines could be used for geothermal purposes using heat-pumps and an open loop involving pumping and re-injection. Logically, warm water is usually expected to be pumped ... [more ▼]

Groundwater in flooded abandoned mines could be used for geothermal purposes using heat-pumps and an open loop involving pumping and re-injection. Logically, warm water is usually expected to be pumped (or injected) in the deep parts of the open network, and cold water is expected to be re-injected (or pumped) in the shallower parts. However, the feasibility and the durability of future ‘Ground Source Heat Pump system’ (GSHP) must be studied through a deep characterization of the subsoil but also using numerical models able to simulate groundwater flow and heat transfer in these complex geological environments. Depending on the type of abandoned mine, the true geometry of the interconnected network of open galleries and shafts can indeed be highly complex. A high-velocity water flow is expected in this type of network, while low-velocity groundwater flow occurs in less permeable fractured and porous rock massif. The SUFT3D code that allows combining in a single model, and in a fully interacting way, linear or distributed reservoirs to model groundwater flows in mine galleries and classical groundwater flow in the variably saturated equivalent porous surrounding media is developed to model heat transfer using the similarities existing between solute and heat transfer equations. The code is then used to test on simple and synthetic case studies, the impact of the hydrogeological conditions and of technical choices on the feasibility and the durability of these geothermal systems. [less ▲]

Detailed reference viewed: 47 (5 ULiège)
Full Text
See detailInfluence of groundwater-surface interactions on groundwater salinity in the Senegal River Delta
Gning, Abdoul Aziz; Wheatherl, Robin; Orban, Philippe ULiege et al

Conference (2018, September 13)

The Senegal River Delta is a strategic region for the development of irrigated agriculture. However, the existence of a shallow saline aquifer, in conjunction with intensification of irrigated agriculture ... [more ▼]

The Senegal River Delta is a strategic region for the development of irrigated agriculture. However, the existence of a shallow saline aquifer, in conjunction with intensification of irrigated agriculture, has led to degradation of cultivated soils. At the end of the XXth Century, the construction of dams on the river has secured water availability throughout the year and induced a rise in surface water levels, inducing a lateral recharge of groundwater in the alluvial aquifer. Because of these major environmental changes, groundwater freshening was expected to occur. Using a combination of regional piezometric and hydrogeochemical surveys as well as local geophysical and hydrogeochemical surveys, groundwater–surface water interactions were characterized to identify the impact of artificial river management and agricultural intensification (among other rice cultivation) on the evolution of groundwater dynamics and chemistry. Results show that groundwater-surface water interactions are mainly visible near rivers where freshwater lenses have developed, with a groundwater salinity that is lower than seawater and groundwater mineralization that seems to evolve in the direction of softening through cationic exchanges related to permanent contact with fresh water. Groundwater far away from rivers and outside irrigated plots has evolved from marine water to brines under the influence of evapotranspiration. In the cultivated parcels, despite large volumes of water used for rice cultivation, groundwater does not show real softening trend. In general, mechanisms that contribute to repel salt water from the sediments correspond to a lateral flush near permanent surface water streams and not to vertical drainage and dilution with rainfall or irrigation water. It is however difficult to estimate the time required to return to more favorable conditions of groundwater salinity. [less ▲]

Detailed reference viewed: 25 (2 ULiège)
Full Text
See detailApsûGIS : a GIS-tool for groundwater vulnerability assessment using physical criteria
Dollé, Fabien ULiege; Thomas, Caroline ULiege; Orban, Philippe ULiege et al

Poster (2018, September 11)

The Apsû method has been developed since 2004 to produce groundwater intrinsic and specific vulnerability maps based on a quantitative description of contaminant transport processes in the subsurface. It ... [more ▼]

The Apsû method has been developed since 2004 to produce groundwater intrinsic and specific vulnerability maps based on a quantitative description of contaminant transport processes in the subsurface. It is based on the source-pathway-receptor approach, driven by two concepts: land surface dangerosity that accounts for lateral flow on land surface and infiltration and subsurface attenuation capacity. Vulnerability classes are based on physically-based criteria reflecting the sensitivity of groundwater to pollution events, namely contaminant travel time across the unsaturated zone, pollution duration, or contaminant concentration or mass recovery factors at the groundwater table. To facilitate the application of the Apsû method to case studies, GIS-based applications and interfaces have been developed to integrate geodatabases and user interfaces in the same environment software. The main geodatabase contains all the data required for the calculation of the vulnerability coefficient, such as spatial data (topography, land cover, hydrological network, meteorology, soil types…) and specific databases on contaminant properties (i.e. Koc values, degradation constants…), on hydrogeological properties of geological layers constituting the unsaturated zone flow path. Specific user interfaces have been developed to prepare and export spatial data required by the Apsû calculations. Once the groundwater vulnerability factors are calculated, another user interface is available to automatically create and customize different thematic layers related to groundwater vulnerability mapping. This integrated system makes it possible to automate numerous data formatting geoprocessing operations, and to ensure data integrity by minimizing user interactions with the data (spatial frame, data projection, link between spatial data and databases, etc.) and to focus work on the specificities of the areas studied and the interpretation of the vulnerability maps created. The objective of the communication is to describe the general organisation and operation of the GIS-based interface, illustrated with groundwater vulnerability case studies for aquifers of the Walloon Region of Belgium. [less ▲]

Detailed reference viewed: 130 (6 ULiège)
Full Text
See detailUsing pharmaceutical compounds as tracers of urban sources of nitrate in groundwater
Neufcourt, Gilles ULiege; Jurado, Anna; Nott, Katherine et al

Conference (2018, September 11)

Nitrate is a natural compound part of the nitrogen cycle. It is widely used in agriculture but urban waste water produced by anthropogenic activities can also constitute non-agricultural sources of ... [more ▼]

Nitrate is a natural compound part of the nitrogen cycle. It is widely used in agriculture but urban waste water produced by anthropogenic activities can also constitute non-agricultural sources of nitrate. Nowadays, the significant increase of nitrate concentrations in groundwater presents a risk for human health. In order to set up adequate measures to protect water quality, it is necessary to determine the possible sources of nitrate such as fertilizers, manure or urban waste waters. Different approaches are available for such purpose based on hydrochemical and isotopic signatures but they remain relatively uncertain. Recent advances in the detection of pharmaceutical compounds at extremely low concentrations in groundwater (in the range of ng/L) offer the opportunity to use some of these substances as chemical tracers to differentiate among nitrate sources. In this context, groundwater samples were collected from public water supplies, natural sources, domestic wells and karstic springs in six different sites in the Walloon Region of Belgium. Classical inorganic chemicals, stable isotopes of nitrate and boron were measured. In addition, ten pharmaceuticals (e.g. diclofenac, carbamazepine, hydrochlorothiazide) among the most frequently detected in the region’s waters were also quantified. The use of pharmaceutical compounds as chemical markers of urban water is only in its early stages. However, the results allowed to identify the most likely sources of nitrate in cases where isotopic analyses were unable to do it. Results show that using pharmaceuticals to discriminate nitrate sources (urban or agricultural) offers interesting perspectives for the future. In particular, the use of certain substances such as carbamazepine is promising. [less ▲]

Detailed reference viewed: 32 (2 ULiège)
Full Text
See detailPredictive mapping of fluoride levels in groundwater in Central Benin (Western Africa) using a geostatistical approach
Tossou; Hermans, Thomas; Orban, Philippe ULiege et al

Conference (2018, September 11)

Groundwater of the crystalline aquifers of central Benin (Département des Collines) are characterized by elevated fluoride concentrations of up to 7 mg/L, whereas the standard recommended by WHO is 1.5 mg ... [more ▼]

Groundwater of the crystalline aquifers of central Benin (Département des Collines) are characterized by elevated fluoride concentrations of up to 7 mg/L, whereas the standard recommended by WHO is 1.5 mg/L. Consumption of these waters with high fluoride content impacts human health, the population of the region being effectively largely affected by dental fluorosis. Recent hydrogeochemical investigations on groundwater from the crystalline aquifers coupled to geochemical, petrological and mineralogical investigations on rock samples collected in the area of interest have revealed that the origin of these anomalous fluoride levels is geogenic with a strong contribution of ferromagnesian minerals, mainly biotite. Using the results obtained on collected samples, together with regional information on geology, a double cartography exercise was performed on the scale of the Department of the Hills in order to obtain (1) a map of estimation of fluoride concentrations in the groundwater by ordinary kriging and (ii) a probability map of exceeding the WHO guideline value (1.5 mg / L) of fluoride in water by Indicator Kriging. In addition to the cartography itself, the analysis of the spatial structure of the data (fluoride content of the groundwater) through the calculation of the variograms shows that there is a strong link between these and the dominant geological structures, confirming the geogenic origin of fluoride. The map produced using these geostatistical procedures will serve as a support for decision makers and resource managers to make the right choice of drinking water catchment areas to avoid, at least to minimize the risk of high levels of fluoride in abstracted groundwaters. [less ▲]

Detailed reference viewed: 30 (5 ULiège)
Peer Reviewed
See detailExperimental assessment and prediction of short-term aquifer thermal energy storage for energy demand-side management applications
Robert, Tanguy ULiege; Hermans, Thomas; Lesparre, Nolwenn et al

Conference (2018, September 10)

Groundwater heat pump (GWHP) systems are now widely used for space heating and cooling and domestic hot water production. On one hand, GWHP systems are considered as a renewable energy and on the other ... [more ▼]

Groundwater heat pump (GWHP) systems are now widely used for space heating and cooling and domestic hot water production. On one hand, GWHP systems are considered as a renewable energy and on the other hand, their increasing use impacts electrical grid balancing. Since the coupling of electrically-driven heating, ventilation, and air-conditioning (HVAC) systems with thermal energy storage (TES) is seen as a promising tool for demand-side management (DSM) in the low-voltage grid, experimental validation of aquifer thermal energy storage (ATES) capabilities at demand side management (DSM) frequencies (real time, intraday, interday, and interseasonal) is needed for the sector to adopt it. We demonstrated here that hourly to daily ATES can be efficient in terms of energy recovery rate and exergy whereas weekly to seasonal ATES bears the risk of lower recovery rates and presents almost always low exergy. Moreover, energy recovery rates are improved with the increasing use of storage and recovery cycles. To formulate this demonstration, we emulated the operating conditions of GWHP systems with ATES in several well-characterized experimental pilot sites in Wallonia. The standardized experiment we used to estimate the different hydrodynamic parameters and energy recovery at the pilot sites was based on push/pull tests with the injection of heated water, its storage for different DSM periods, and finally its recovery. Fluxes were either measured in-situ by means of the finite volume point dilution method or estimated with the local hydraulic conductivity and gradient. We report here a direct relationship between the energy recovery rate and natural groundwater fluxes. [less ▲]

Detailed reference viewed: 68 (12 ULiège)
Full Text
See detailDirect single well measurement of groundwater flux in permafrost-impacted aquifers in Nunavik, Canada
Jamin, Pierre ULiege; Cochand, Marion; Dagenais, Sophie et al

Poster (2018, September 10)

Permafrost dynamics in high latitude territories is a complex process resulting from atmospheric, soil, water and vegetation interaction. Advective heat transport by groundwater has been identified as ... [more ▼]

Permafrost dynamics in high latitude territories is a complex process resulting from atmospheric, soil, water and vegetation interaction. Advective heat transport by groundwater has been identified as potentially playing a significant role in permafrost dynamics. However, there is a lack of direct measurements of groundwater parameters such as hydraulic head and hydraulic conductivity for determining flow patterns and groundwater fluxes in permafrost environments due to difficulties in accessing these remote territories and associated high costs of field work in such remote areas. Existing monitoring wells are often insufficient to allow the assessment of representative hydraulic gradients and realistic groundwater flow rates. Here, the Finite Volume Point Dilution Method (FVPDM) is applied to measure in-situ groundwater fluxes in a supra- and sub-permafrost sandy aquifer within a small watershed in Umiujaq, Nunavik, Canada. The advantage of the FVPDM method is to provide direct measurement of groundwater flux using a single well technique. The tests show that this method can be successfully applied in remote conditions and with limited resources. Darcy fluxes derived from the FVPDM tests varied from 0.577 to 0.840 m/d, implying that advective heat transport from groundwater flow could be contributing to permafrost thaw at this site. These data are important since very few estimates of groundwater fluxes are available in the discontinuous permafrost zone and that such a significant groundwater flux can have a major impact on heat exchange between groundwater and permafrost. Moreover, they are essential for building and calibrating realistic groundwater flow and heat transport models required for better understand permafrost dynamics and sustainable groundwater management in cold environments. [less ▲]

Detailed reference viewed: 32 (1 ULiège)
Full Text
See detailDynamics of greenhouse gases in the aquifers of two agricultural catchments of Belgium
Jurado, Anna; Nikolenko, Olha ULiege; Orban, Philippe ULiege et al

Conference (2018, September 10)

Greenhouse gases (GHGs) are an environmental problem because their concentrations in the atmosphere are continuously increasing. Agricultural practices represented up to one third of anthropogenic ... [more ▼]

Greenhouse gases (GHGs) are an environmental problem because their concentrations in the atmosphere are continuously increasing. Agricultural practices represented up to one third of anthropogenic emissions of GHGs such as nitrous oxide (N2O), methane (CH4) and carbon dioxide (CO2), which all contribute to climate change and N2O to stratospheric ozone destruction. This study presents recent case studies in two different agricultural areas of the Walloon Region (Belgium). To this end, the dynamics of CO2, CH4 and N2O were studied in the aquifers of the Triffoy and Geer catchments. In order to get an insight into GHGs production/consumption processes, the results of the stable isotope analyses of NO3-, N2O, SO42-, B, DOC and 3H along with the hydrogeochemical data were used. Our study attempts to acquire additional evidence about (1) the processes that consume and produce GHGs in groundwater in these two catchments (2) the spatial variability of N2O along the lateral and vertical dimensions of the Geer aquifers and (3) the dynamics of GHGs in the river-groundwater interface in the Triffoy catchment. Results indicate that groundwater is oversaturated in N2O and CO2 with respect to atmospheric equilibrium but only marginally for CH4, suggesting that groundwater can be a source of these GHGs to the atmosphere. Nitrification and nitrifier-denitrification seems to be the main process for the accumulation of N2O in groundwater of the two catchments and the oxic conditions prevailing in the aquifers are not prone to the accumulation of CH4. Groundwater is probably an important source of N2O and CO2 into the river but when the measures are scaled at catchment scale, these fluxes are probably relatively modest. Nevertheless, their quantification would better constrain nitrogen and carbon budgets in natural systems. [less ▲]

Detailed reference viewed: 37 (5 ULiège)
Full Text
Peer Reviewed
See detailRecent advances for monitoring groundwater and pollutant fluxes using single-well applied tracer techniques
Jamin, Pierre ULiege; Orban, Philippe ULiege; Verreydt, Goedele et al

Conference (2018, September 10)

In many different hydrogeological investigations, quantifying groundwater fluxes is essential but often challenging due to the variability of hydraulic conditions in space and time. Traditional approaches ... [more ▼]

In many different hydrogeological investigations, quantifying groundwater fluxes is essential but often challenging due to the variability of hydraulic conditions in space and time. Traditional approaches used to estimate groundwater fluxes are based on hydraulic conductivity obtained from field pumping or slug tests that provide only order-of-magnitude estimates and hydraulic gradients that can also vary, especially in areas of active groundwater discharge or pumping. The Finite Volume Point Dilution Method (FVPDM) is a recently developed applied tracer technology able to measure accurately groundwater fluxes and to monitor continuously their changes with time. We report 10 years of application of the FVPDM in contrasted hydrogeological contexts, from porous alluvial to fractured-rock aquifers, including strong interactions with surface water and contrasting groundwater flow dynamics. The obtained results prove that the FVPDM is able to measure a wide range of groundwater fluxes from a few centimetres per day to hundreds of metres per day. These results also emphases the variability in groundwater fluxes, (1) with time in aquifers influenced by variable hydraulic conditions such as tidal effects and (2) in space where orders of magnitude difference in groundwater fluxes are observed between nearby monitoring wells at a given site. Preliminary results of continuing work have also shown the potential for the FVPDM approach to be coupled with contaminant specific sensors and with passive sampling technologies to quantify contaminant mass fluxes in the subsurface. Recent developments have also investigated the ability to assess groundwater flow directions at the well scale. [less ▲]

Detailed reference viewed: 43 (3 ULiège)
Full Text
See detailSimulation of groundwater and heat transfer for the geothermal use of flooded abandoned old-mines
Vopat, Olivier; Orban, Philippe ULiege; Brouyère, Serge ULiege et al

Conference (2018, September)

Groundwater in flooded abandoned mines could be used for geothermal purposes using heat-pumps and an open loop involving pumping and re-injection. Logically, warm water is usually expected to be pumped ... [more ▼]

Groundwater in flooded abandoned mines could be used for geothermal purposes using heat-pumps and an open loop involving pumping and re-injection. Logically, warm water is usually expected to be pumped (or injected) in the deep parts of the open network, and cold water is expected to be re-injected (or pumped) in the shallower parts. However, the feasibility and the durability of future ‘Ground Source Heat Pump system’ (GSHP) must be studied through a deep characterization of the subsoil but also using numerical models able to simulate groundwater flow and heat transfer in these complex geological environments. Depending on the type of abandoned mine, the true geometry of the interconnected network of open galleries and shafts can indeed be highly complex. A high-velocity water flow is expected in this type of network, while low-velocity groundwater flow occurs in less permeable fractured and porous rock massif. The SUFT3D code that allows combining in a single model, and in a fully interacting way, linear or distributed reservoirs to model groundwater flows in mine galleries and classical groundwater flow in the variably saturated equivalent porous surrounding media is developed to model heat transfer using the similarities existing between solute and heat transfer equations. The code is then used to test on a simplified case study based on the characteristics of the Werister coal mine (Belgium), the impact of the hydrogeological conditions and of technical choices on the feasibility and the durability of these geothermal systems. [less ▲]

Detailed reference viewed: 43 (10 ULiège)
Full Text
Peer Reviewed
See detailCharacterization of recharge mechanisms in a Precambrian basement aquifer in semi-arid south-west Niger
Abdou Babaye, Maman Sani; Orban, Philippe ULiege; Ousmane, Boureisma et al

in Hydrogeology Journal (2018)

In the central part of the semi-arid Dargol Basin of southwestern Niger, most of the groundwater resource is contained in the fractured aquifers of the Precambrian basement. The groundwater resource is ... [more ▼]

In the central part of the semi-arid Dargol Basin of southwestern Niger, most of the groundwater resource is contained in the fractured aquifers of the Precambrian basement. The groundwater resource is poorly characterized and this study is the first attempt to better describe the recharge mechanisms and hydrogeochemical behaviour of the aquifers. Hydrogeochemical and piezometric methods were combined to determine changes in recharge rate and origin of groundwaters for the shallow weathered aquifer and the deep fissured/fractured aquifer. At the basin scale, the groundwater fluxes towards the Niger River are influenced mainly by topography, with no visual long-term trend in groundwater levels (1980-2009). The hydro-geochemical signature is dominated by the calcic-bicarbonate to magnesian (70%) type. It shows evolution from an open environment with CO2 and low mineralized water (granitoids, alterites) towards a more confined environment with more mineralized waters (schists). Stable water isotopes (δ18O, δ2H) analysis suggests two main groundwater recharge mechanisms: (i) direct recharge with nearly no post-rainfall fractionation signature and (ii) indirect recharge from evaporated surface waters and/or stream-channel beds. Groundwater tritium content indicates that recharge is mostly recent, with an age less than 50 years (3H > 3 TU), with only 10% indicating low or even no recharge for the past decades. A median value of the groundwater renewal rate estimated from individual values of tritium is equivalent to 1.3% y-1, close to the one determined for groundwater samples dating to the early 1980s, thus indicating no measurable long-term change. [less ▲]

Detailed reference viewed: 32 (4 ULiège)