References of "Orban, Philippe"
     in
Bookmark and Share    
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 (5 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: 14 (1 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: 53 (5 ULg)
Full Text
See detailEvaluation qualitative et quantitative des ressources en eau souterraine dasn le bassin de Dargol (Liptako – Niger)
Abdou Babaye, Maman Sani ULg; Boureimane, Ousmane; Orban, Philippe ULg et al

Conference (2012, November)

Située dans la partie Sud-Ouest du Niger, le bassin de Dargol appartient à la région de socle précambrien du Liptako. L’étude du chimisme des eaux souterraines révèle trois types de faciès dont le plus ... [more ▼]

Située dans la partie Sud-Ouest du Niger, le bassin de Dargol appartient à la région de socle précambrien du Liptako. L’étude du chimisme des eaux souterraines révèle trois types de faciès dont le plus dominant est le type bicarbonaté calcique à magnésien (65%). Environ 47% d’ouvrages ont des teneurs en nitrates dépassant largement les normes OMS (50 mg/l). Les teneurs en isotopes stables (δ18O, δ2H) de la nappe indiquent deux mécanismes de recharge: une recharge directe par les eaux des pluies peu ou pas évaporées, et une recharge indirecte par les eaux évaporées issues des lits de koris et des eaux de surface. L’analyse des teneurs en tritium de la nappe indique que la recharge est récente pour la majorité des points investigués. En revanche, dans le secteur à faibles teneurs en tritium, le taux de renouvellement semble être faible voire nul. [less ▲]

Detailed reference viewed: 114 (3 ULg)
Full Text
Peer Reviewed
See detailHow tracer tests simulations strongly constrain flow and solute transport models in fractured chalk aquifers
Goderniaux, Pascal ULg; Daoudi, Moubarak; Orban, Philippe ULg et al

Conference (2012, May)

Flow and solute transport in the saturated zone of a micro-fissured and fractured chalk aquifer (Geer basin, Belgium) has been studied by more than 35 tracer tests in 11 sites. The tracer tests campaign ... [more ▼]

Flow and solute transport in the saturated zone of a micro-fissured and fractured chalk aquifer (Geer basin, Belgium) has been studied by more than 35 tracer tests in 11 sites. The tracer tests campaign was preceded by a morphostructural study associated to a geophysical survey including electrical resistivity and refraction seismic measurements. Results provided information on the main expected fracturation axis where a series of injection and monitoring wells were drilled. In each of the 11 sites, multi-tracer tests have been performed in groundwater convergent flow conditions to pumping wells or draining galleries (used for drinking water production). The analysis of the detailed quantitative breakthrough curves allowed identifying various transport behaviours, from rapid advective to dominant dispersive processes with immobile water effects. Groundwater flow and solute transport in such a fractured chalk can be simulated using different conceptual approaches. Using HYDROGEOSPHERE (Therrien and Sudicky, 1996), a comparison is made between two ways for representing the fracture zones: (1) high contrasted hydraulic conductivity zones with a classical REV approach and (2) the explicit representation of discrete fractures interacting with a porous medium. Promising results are found using the discrete approach for representing the fractures. In this last case, an aperture of the order of the millimetre is enough for creating, where it is needed, a fast advective peak combined with a long highly dispersive component due to the chalk matrix. The discrete fracture approach prevents the modeller from introducing unrealistic parameters values in the fracture zones as it is generally the case in the classical REV-based method where the fractured zones are simply represented by elongated REV. However, it is shown that the availability of field data, as multi-tracers test results, creates very high constraints to be taken into account in the calibration processes (i.e calibration on the measured groundwater flow and transport conditions). The detailed calibration on the different breakthrough curves is not an easy task and automatic calibration is not easy to organize. Results are particularly illustrative to show that a detailed parameterization and calibration of such a local situation remain difficult. Perspectives will be discussed about the potential use of automatic calibration tools as UCODE_2005 or PEST for solving such local situation models and the needed further steps for ‘upscaling’ local situation models at the scale of the whole aquifer or groundwater body. [less ▲]

Detailed reference viewed: 88 (12 ULg)