References of "Orban, Philippe"
     in
Bookmark and Share    
Full Text
Peer Reviewed
See detailUsing multiple point geostatistics for tracer test modeling in a clay-drape environment with spatially variable conductivity and sorption coefficient
Huysmans, Marijke; Orban, Philippe ULg; Cochet, Elke et al

in Mathematical Geosciences (2013), 46(5), 519-537

This study investigates the effect of fine-scale clay drapes on tracer transport. A tracer test was performed in a sandbar deposit consisting of cross-bedded sandy units intercalated with many fine-scale ... [more ▼]

This study investigates the effect of fine-scale clay drapes on tracer transport. A tracer test was performed in a sandbar deposit consisting of cross-bedded sandy units intercalated with many fine-scale clay drapes. The heterogeneous spatial distribution of the clay drapes causes a spatially variable hydraulic conductivity and sorption coefficient. A fluorescent tracer (sodium naphthionate) was injected in two injection wells and groundwater was sampled and analyzed from five pumping wells. To determine (1) whether the fine-scale clay drapes have a significant effect on the measured concentrations and (2) whether application of multiple-point geostatistics can improve interpretation of tracer tests in media with complex geological heterogeneity, this tracer test is analyzed with a local 3D groundwater flow and transport model in which fine-scale sedimentary heterogeneity is modeled using multiple-point geostatistics. To reduce memory needs and calculation time for the multiple-point geostatistical simulation step, this study uses the technique of "direct multiple-point geostatistical simulation of edge properties". Instead of simulating pixel values, model cell edge properties indicating the presence of irregularly-shaped surfaces are simulated using multiple point geostatistical simulations. Results of a sensitivity analysis show under which conditions clay drapes have a significant effect on the concentration distribution. Calibration of the model against measured concentrations from the tracer tests reduces the uncertainty on the clay drape parameters. The calibrated model shows which features of the breakthrough curves can be attributed to the geological heterogeneity of the aquifer and which features are caused by other processes. [less ▲]

Detailed reference viewed: 62 (11 ULg)
Full Text
See detailConception et utilisation de « seepage-meters » artisanaux pour l'étude des interactions «rivière – eaux souterraines » au Burkina Faso
Sauret, Elie ULg; Nitcheu, Martial; Orban, Philippe ULg et al

Conference (2013, September 25)

Situé à l'ouest du Burkina Faso dans la région de Bobo Dioulasso, le bassin du Kou présente un contexte climatique et hydro(géo)logique, favorables à l'accumulation et à la mobilisation d’importantes ... [more ▼]

Situé à l'ouest du Burkina Faso dans la région de Bobo Dioulasso, le bassin du Kou présente un contexte climatique et hydro(géo)logique, favorables à l'accumulation et à la mobilisation d’importantes ressources en eaux souterraines et de surface, en témoigne, les sources de Nasso/guinguette au centre de bassin qui ont un débit d'environ 6000 m3/h. D'un point de vue hydrogéologique, les sources qui constituent les points d’émergences des formations aquifères profonds du bassin se déchargent dans la rivière (Kou) et assurent ainsi sa pérennité tout au long de l’année. D’amont en aval du bassin, le Kou est largement exploité par les agriculteurs installés ça et là de part et d’autre de ses rives. Malheureusement, au cours des vingt dernières années un afflux important de nouveaux agriculteurs a constitué une pression sur les ressources en terres et en eau du bassin, occasionnant une concurrence aigue à tendance conflictuelle entre les différents exploitants agricoles autour de la rivière. Pour mieux caractériser et, quantifier l'évolution dans le temps des ressources en eau du Kou , une série de tests et études hydrogéologiques prenant en compte les deux autres réservoirs : les aquifères sédimentaires profonds et la plaine alluviale déployé tout au long de la rivière, ont été réalisées. Les techniques de mesure directe par seepage meters des volumes d’eau échangés à l’interface «rivière - nappe» ont permis de quantifier localement les transferts d’eau et déceler les directions et sens des échanges entre les différents réservoirs. Les résultats obtenus ont montré qu’il existe des sections où le Kou gagne (1.5 m3/s) ou perd (-0.10 m3/s) de l’eau au profit ou au détriment des eaux souterraines (aquifères sédimentaires profonds et plaine alluviale). Ces résultats ont été validés par des analyses hydrochimiques des échantillons d’eau prélevés. [less ▲]

Detailed reference viewed: 31 (3 ULg)
Full Text
Peer Reviewed
See detailA heat injection and pumping experiment in a gravel aquifer monitored with crosshole electrical resistivity tomography
Hermans, Thomas ULg; Wildemeersch, Samuel ULg; Jamin, Pierre ULg et al

in EarthDoc - Near Surface Geosciences 2013 - 19th European Meeting of Environmental and Engineering Geophysics (2013, September)

Thermal tracing experiments are becoming common in hydrogeology to estimate parameters governing heat transport processes and to study geothermal reservoirs. Electrical resistivity tomography (ERT) has ... [more ▼]

Thermal tracing experiments are becoming common in hydrogeology to estimate parameters governing heat transport processes and to study geothermal reservoirs. Electrical resistivity tomography (ERT) has proven its ability to monitor salt tracer tests, but few studies have investigated its performances in thermal tracing experiments. In this study, we monitor the injection and pumping of heated water using crosshole ERT in a panel crossing the main flow direction. Difference inversion time-lapse images clearly show the heterogeneous pattern of resistivity changes, and thus temperature changes, highlighting the existence of preferential flow paths in the aquifer. Comparison of temperature estimates from ERT and direct measurements in boreholes show the ability of ERT to quantify the temperatures in the aquifer and to draw the breakthrough curves of the thermal tracer with a relative accuracy. Such resistivity data may provide important information to improve hydrogeological models. Our study proves that ERT, especially crosshole ERT, is a reliable tool to follow thermal tracing experiments. It also confirms that ERT should be included to in situ techniques to characterize heat transfer in the subsurface and to monitor geothermal resources exploitation. [less ▲]

Detailed reference viewed: 44 (21 ULg)
Full Text
See detailHeat transfer characterization in a shallow aquifer using heat and dye tracer tests
Wildemeersch, Samuel ULg; Orban, Philippe ULg; Hermans, Thomas ULg et al

Conference (2013, July 22)

Very low enthalpy geothermal systems (open or closed) are increasingly considered for heating or cooling houses and offices using groundwater energy combined with heat pumps. However, the design and the ... [more ▼]

Very low enthalpy geothermal systems (open or closed) are increasingly considered for heating or cooling houses and offices using groundwater energy combined with heat pumps. However, the design and the impact of current shallow geothermal systems are often set up and assessed in a semi-empirical way. In our country, this situation seems accepted by most of the private partners but not by the authorities and responsible administrations evaluating the impact on groundwater with a mid- to long-term perspective. A rigorous methodology is needed based on a physically based estimation of heat transfer parameters. In this study, the simultaneous use of heat and dye tracers allows estimating simultaneously heat transfer and solute transport parameters in an alluvial aquifer. The experimental field site, located near Liege (Belgium), is equipped with 21 piezometers drilled in the alluvial deposits of the Meuse River. These alluvial deposits are composed of a loam layer (3 m) overlying a sand and gravel layer which constitutes the alluvial aquifer (7 m). The tracing experiment consisted in injecting simultaneously heated water and a dye tracer in a piezometer and monitoring the evolution of groundwater temperature and tracer concentration in a series of control panels set perpendicularly to the main groundwater flow. Results showed drastic differences between heat transfer and solute transport due to the main influence of thermal capacity of the saturated porous medium. The tracing experiment was then simulated using a numerical model and the best estimation of heat transfer and solute transport parameters is obtained by calibrating this numerical model using inversion tools. The developed concepts and tests may lead to real projects of various extents that can be now optimized by the use of a rigorous and efficient methodology at the field scale. [less ▲]

Detailed reference viewed: 22 (7 ULg)
Full Text
See detailCoupling heat and salt tracer experiment for the estimation of heat transfer and solute transport parameters
Wildemeersch, Samuel ULg; Jamin, Pierre ULg; Orban, Philippe ULg et al

Conference (2013, April 22)

Geothermal energy is a promising source of energy in the context of sustainable development. Therefore, very low enthalpy geothermal systems (open or closed) are increasingly considered for heating or ... [more ▼]

Geothermal energy is a promising source of energy in the context of sustainable development. Therefore, very low enthalpy geothermal systems (open or closed) are increasingly considered for heating or cooling houses and offices using groundwater energy. However, prior to the development of such systems, a feasibility study and an impact study of the system on groundwater ressources are required. Thereliability of such studies is highly dependent on the quality of the estimation of heat transfer parameters. This highlights the necessity of estimating properly such parameters. The objective of this study is to combine the use of heat and salt tracers to estimate simultaneously heat transfer and solute transport parameters in an alluvial aquifer. Additionally, coupling heat and salt tracing experiments is particularly useful for comparing heat transfer and solute transport processes occurring in the subsurface. An experimental field site, located near Liege (Belgium), is equipped with 21 piezometers drilled in the alluvial deposits of the Meuse River. These alluvial deposits are composed of a loess layer (3 m) overlying a sand and gravel layer which constitutes the alluvial aquifer (7 m). The coupled tracing experiment consists in injecting simultaneously heated water and salt in a piezometer and monitoring the evolution of groundwater temperature and salt concentration in a series of control panels set perpendicularly to groundwater flow. This coupled tracing experiment is then simulated using a numerical model. The estimation of heat transfer and solute transport parameters is obtained by calibrating this numerical model using inversion tools. The present study proposes a methodology coupling heat and salt tracing experiment for estimating heat transfer parameters at the field scale. Furthermore, this coupled tracing experiment shows that the comportment of heat and solute in the subsurface presents key differences. [less ▲]

Detailed reference viewed: 56 (23 ULg)
Full Text
See detailModélisation régionale et locale sur base des données de la carte géologique
Orban, Philippe ULg

in Renard, José (Ed.) La carte hydrogéologique de Wallonie : un outil au service de tous - Synthèse des exposés (2013, April)

Detailed reference viewed: 28 (3 ULg)
Full Text
Peer Reviewed
See detailIs it worth protecting groundwater from diffuse pollution with agri-environmental schemes? A hydro-economic modeling approach
Hérivaux, Cécile; Orban, Philippe ULg; Brouyère, Serge ULg

in Journal of Environmental Management (2013), 128

In Europe, 30% of groundwater bodies are considered to be at risk of not achieving the Water Framework Directive (WFD) ‘good status’ objective by 2015, and 45% are in doubt of doing so. Diffuse ... [more ▼]

In Europe, 30% of groundwater bodies are considered to be at risk of not achieving the Water Framework Directive (WFD) ‘good status’ objective by 2015, and 45% are in doubt of doing so. Diffuse agricultural pollution is one of the main pressures affecting groundwater bodies. To tackle this problem, the WFD requires Member States to design and implement cost-effective programs of measures to achieve the ‘good status’ objective by 2027 at the latest. Hitherto, action plans have mainly consisted of promoting the adoption of Agri- Environmental Schemes (AES). This raises a number of questions concerning the effectiveness of such schemes for improving groundwater status, and the economic implications of their implementation. We propose a hydro-economic model that combines a hydrogeological model to simulate groundwater quality evolution with agronomic and economic components to assess the expected costs, effectiveness, and benefits of AES implementation. This hydro-economic model can be used to identify cost-effective AES combinations at groundwater-body scale and to show the benefits to be expected from the resulting improvement in groundwater quality. The model is applied here to a rural area encompassing the Hesbaye aquifer, a large chalk aquifer which supplies about 230,000 inhabitants in the city of Liege (Belgium) and is severely contaminated by agricultural nitrates. We show that the time frame within which improvements in the Hesbaye groundwater quality can be expected may be much longer than that required by the WFD. Current WFD programs based on AES may be inappropriate for achieving the ‘good status’ objective in the most productive agricultural areas, in particular because these schemes are insufficiently attractive. Achieving ‘good status’ by 2027 would demand a substantial change in the design of AES, involving costs that may not be offset by benefits in the case of chalk aquifers with long renewal times. [less ▲]

Detailed reference viewed: 13 (8 ULg)
Full Text
See detailEtude hydrogéochimique des eaux de la nappe du Continental Terminal du Saloum : Relation eau de surface – eau souterraine
Dieng, Ndeye Maguette ULg; Orban, Philippe ULg; FAYE, Serigne et al

Conference (2012, November)

L’évaluation de l’état actuel de la qualité des eaux de la nappe du Continental Terminal et du fleuve Saloum a été réalisée grâce à l’analyse de 44 échantillons d’eau souterraine et 3 échantillons d’eau ... [more ▼]

L’évaluation de l’état actuel de la qualité des eaux de la nappe du Continental Terminal et du fleuve Saloum a été réalisée grâce à l’analyse de 44 échantillons d’eau souterraine et 3 échantillons d’eau de surface collectés en saison humide. Les analyses des ions majeurs et les mesures de la conductivité électrique (CE) ont démontré que les eaux de la nappe du CT du Saloum étaient largement contaminées par la salinisation (CE comprise entre à 750 et 2800 µS/cm) au niveau de la zone côtière à l’ouest et au nord sur une bande longeant le fleuve Saloum. Dans ces zones, les eaux ont désormais des faciès chimiques chlorurés sodiques venant de faciès au départ bicarbonatés calciques des eaux souterraines peu contaminées. Au niveau de certains points, la composition des eaux souterraines devient sensiblement la même que celle des eaux du fleuve Saloum. Les diagrammes binaires (Na versus Cl, Na/Cl versus Cl, [Ca + Mg] versus HCO3 et [(Ca+Mg) - (HCO3+SO4)] versus (Na-Cl)) ont permis de définir les processus géochimiques et les phénomènes de mélange impliqués dans la minéralisation des eaux. Suivant la répartition des valeurs de conductivité électrique et des types d’eaux, une zonation a été cartographiée [less ▲]

Detailed reference viewed: 45 (12 ULg)