References of "Hallet, Vincent"
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See detailValorisation de la Carte des Sols dans un cadre inattendu - Le tourisme à caractère scientifique
Rekk, Samantha; Legrain, Xavier ULg; Bock, Laurent ULg et al

Poster (2010, November 24)

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See detailDetailed study on groundwater pollution by bentazone in the Walloon Region, Belgium
Limbourg, Quentin; Mattern, Samuel; Hallet, Vincent et al

Report (2010)

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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 detailCRA-W's Committee of Intervention : analyse of catchments polluted with pesticide
Noel, Stephanie; Bah, Boubacar Billo ULg; Colinet, Gilles ULg et al

in 10th International Congress on Mechanization and Energy in Agriculture, 14-17 October 2008, Antalya-Türkiye - Prodeedings (2008)

In the Walloon Region of Belgium, a commlttee of Intervention has been created to Investigate problems of pesticide contamination of various catchments use for drinking water production. This commlttee ... [more ▼]

In the Walloon Region of Belgium, a commlttee of Intervention has been created to Investigate problems of pesticide contamination of various catchments use for drinking water production. This commlttee Involves the Agricultural Research centre - Wallonla (CRA-W, project coordinator) and sorne University experts. It ls funded by the Société Publique de Gestion des Eaux (SPGE). The diagnosis method, base on the AQUAPLAlNE method (Arvalis - France), conslsts of 4 steps. The first step Is the preparation of diagnosls (at the office) that takes into account the paper r1sk of active ingredients. and thelr uses, the identification of the agrtcultural parcels, the collection of cartographie and numeric data, the description of the hydrogeological and pedological contexts and the study of the meteorologlcal data ln relation with the period of pollution. The second step conslsts of maklng a plot diagnosls (on the field) ta Identify the way of transfer inside the plot and collecting data. At the thlrd step, the people who can apply ppp treatment close to the catchment are met (farmers and city services). Information are coJ!ected on treatments applied and on the state of parcels. Based on the hypathesls of pollution cause, the committee proposes solution to solve the problem. One of the catchment that has been investigated by the commlttee is located at Biesmerée, (Namur province, ln Belglum). A temporally contamination was caused by 4 pesticides: chlortoluron, isoproturon, trifluralln and diflufenlcan. After Investigations, it seems that the pollution was probably due ta the hydrogeologlcal context . As the river Is locally perched over the aqulfer, the presence of Poly-aromatic hydrocarbons (PAHs) could be due ta the Infiltration of surface water inside the catchment or/and to the presence of a sinkhole temparaHy activated durlng river flood period. Infiltration rate has ta be assessed and river bank Impermeabilization Is recommended [less ▲]

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See detailMigration of contaminants through the unsaturated zone overlying the Hesbaye chalky aquifer in Belgium: a field investigation
Brouyère, Serge ULg; Dassargues, Alain ULg; Hallet, Vincent

in Journal of Contaminant Hydrology (2004), 72(1-4), 135-164

This paper presents the results of a detailed field investigation that was performed for studying groundwater recharge processes and solute downward migration mechanisms prevailing in the unsaturated zone ... [more ▼]

This paper presents the results of a detailed field investigation that was performed for studying groundwater recharge processes and solute downward migration mechanisms prevailing in the unsaturated zone overlying a chalk aquifer in Belgium. Various laboratory measurements were performed on core samples collected during the drilling of boreholes in the experimental site. In the field, experiments consisted of well logging, infiltration tests in the unsaturated zone, pumping tests in the saturated zone and tracer tests in both the saturated and unsaturated zones. Results show that gravitational flows govern groundwater recharge and solute migration mechanisms in the unsaturated zone. In the variably saturated chalk, the migration and retardation of solutes is strongly influenced by recharge conditions. Under intense injection conditions, solutes migrate at high speed along the partially saturated fissures, downward to the saturated zone. At the same time, they are temporarily retarded in the almost immobile water located in the chalk matrix. Under normal recharge conditions, fissures are inactive and solutes migrate slowly through the chalk matrix. Results also show that concentration dynamics in the saturated zone are related to fluctuations of groundwater levels in the aquifer. A conceptual model is proposed to explain the hydrodispersive behaviour of the variably saturated chalk. Finally, the vulnerability of the chalk to contamination issues occurring at the land surface is discussed. (C) 2003 Elsevier B.V. All rights reserved. [less ▲]

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See detailComparison of aquifer vulnerability assessment techniques. Application to the Neblon river basin (Belgium)
Gogu, Radu Constantin; Hallet, Vincent; Dassargues, Alain ULg

in Environmental Geology (2003), 44(8), 881-892

Five different methods for assessing intrinsic aquifer vulnerability were tested in a case study and their results compared. The test area was a slightly karstified district in the Condroz region of ... [more ▼]

Five different methods for assessing intrinsic aquifer vulnerability were tested in a case study and their results compared. The test area was a slightly karstified district in the Condroz region of Belgium. The basin covers about 65 km(2) and the karst aquifer provides a water-supply of about 28,000 m(3)d(-1). The methods tested were: EPIK (Doerfliger et al. 1999), DRASTIC (Aller et al.1987), 'German method' (von Hoyer and Sofner 1998), GOD (Foster 1987) and ISIS (Civita and De Regibus 1995). The results are compared and critically examined. From the analysis, it seems that reducing the number of parameters is unsatisfactory, due to the variety of geological conditions. The various methods produce very different results at any given site. As only physically-based methods can be checked for their reliability, it is clear that future vulnerability mapping techniques must incorporate such methods. [less ▲]

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