Impact des épisodes de sécheresse sur les eaux souterraines : mise en contexte, état des lieux et perspectives

L'objectif de l'exposé était de revenir sur les conséquences des épisodes de sécheresse sur les ressources en eau souterraine de Wallonie, en illustrant cela par quelques exemples et observations récentes et en tirer des perspectives pour la gestion à venir des eaux souterraines vis-à-vis de cette problématique.6. Clean water and sanitatio

Applied tracer techniques in contaminant hydrogeology

6. Clean water and sanitatio

Stress factors and associated physically based criteria and conclusions on the directions to be followed for developing a physically based vulnerability assessment method

The specific results and outcomes of this deliverable is the proposition of a methodological framework for groundwater vulnerability assessment to any kind of stress factors, from a physically-based point of view. This methodology is in addition compatible with the well-known EU DPSIR framework for analysis from a physical and socio-economical perspective, environmental problems. From a more generic perspective, this deliverable provides a very convenient and rigorous framework for integrating the various research components developed within the project, into a decision support system, integrating environmental problems, data, processes and models, and socio-economical aspects.GABARDINE Groundwater artificial recharge based on alternative sources of water: advanced integrated technologies and management (FP6 STREP Thematic Priority: Global change and Ecosystems

Migration of contaminants through the unsaturated zone overlying the Hesbaye chalky aquifer in Belgium: a field investigation

peer reviewedThis 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.Etude phénoménologique de la propagation d'une susbtance miscible en milieu non saturé et application au transfert des nitrates vers la nappe aquifère de Hesbay

Caractérisation hydrogéologique et support à la mise en oeuvre de la Directive Européenne 2000/60 sur les masses d’eau souterraine en Région Wallonne - Délivrable 6.0 - Note méthodologique relative à la modélisation hydrogéologique des masses d'eau souterraine RWM011, RWM012 et RWM021 (aspects quantitatifs et qualitatifs)

Synclin'Eau : Caractérisation hydrogéologique et support à la mise en oeuvre de la Directive Européenne 2000/60 sur les masses d’eau souterraine en Région Wallonn

Deliverable D2.5: Decision grid for best approach in terms of modelling concepts/contaminants

FRAC-WECO : Flux-based risk assessment of contaminants on water resources and ecosystems (projet SD/TE/02A

Contribution au guide explicatif des fiches par masse d’eau et aux fiches de caractérisation des masses d’eau souterraines (Tâche TV1)

Convention relative à la valorisation et au développement du module SIG de cartographie de la vulnérabilité des eaux souterraines et de risques – APSÛ-GIS

Modeling the impact of the nitrate contamination on groundwater at the groundwater body scale : The Geer basin case study

In the next decades, groundwater managers will have to face regional degradation of the quantity and quality of groundwater under pressure of land-use and socio-economic changes. In this context, the objectives of the European Water Framework Directive require that groundwater be managed at the scale of the groundwater body, taking into account not only all components of the water cycle but also the socio-economic impact of these changes. One of the main challenges remains to develop robust and efficient numerical modeling applications at such a scale and to couple them with economic models, as a support for decision support in groundwater management. An integrated approach between hydrogeologists and economists has been developed by coupling the hydrogeological model SUFT3D and a cost-benefit economic analysis to study the impact of agricultural practices on groundwater quality and to design cost-effective mitigation measures to decrease nitrate pressure on groundwater so as to ensure the highest benefit to the society. A new modeling technique, the ‘Hybrid Finite Element Mixing Cell’ approach has been developed for large scale modeling purposes. The principle of this method is to fully couple different mathematical and numerical approaches to solve groundwater flow and solute transport problems. The mathematical and numerical approaches proposed allows an an adaptation to the level of local hydrogeological knowledge and the amount of available data. In combination with long time series of nitrate concentrations and tritium data, the regional scale modelling approach has been used to develop a 3D spatially distributed groundwater flow and solute transport model for the Geer basin (Belgium) of about 480 km2. The model is able to reproduce the spatial patterns of nitrate concentrations together nitrate trends with time. The model has then been used to predict the future evolution of nitrate trends for two types of scenarios: (i) a “business as usual scenario” where current polluting pressures remain the same and (ii) two contrasted scenarios that simulate the implementation of programs of measures aiming at reaching good chemical status. The results of the hydrogeological model under the “business as usual scenario” have been used to assess the cost for the society of the continuous degradation of the groundwater quality. The results of the hydrogeological model under the two contrasted scenarios have been used to assess the economical benefit as avoided damage resulting from the decrease in the nitrate load. A cost-benefit analysis has been thus performed to assess the programme of mitigation measures which provides the largest benefits at the lowest cost.FP6 AQUATERRA Integrated Project no. 505428 (GOCE). Integrated modelling of the river-sediment-soil-groundwater system; advanced tools for the management of catchment areas and river basins in the context of global chang

Heat transfer characterization in a shallow aquifer using heat and dye tracer tests

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