Sablière 'Tout Lui Faut': synthèse des données hydrogéologiques disponibles

Report (2009)

Impact of climate change on groundwater resources: the case of the Geer basin

Poster (2009, April)

Solute transport modelling at the groundwater body scale: Nitrate trends assessment in the Geer basin (Belgium)

Doctoral thesis (2009)

Water resources management is now recognized as a multidisciplinary task that has to be performed in an integrated way, within the natural boundaries of the hydrological basin or of the aquifers. Policy ... [more ▼]

Water resources management is now recognized as a multidisciplinary task that has to be performed in an integrated way, within the natural boundaries of the hydrological basin or of the aquifers. Policy makers and water managers express a need to have tools able at this regional scale to help in the management of the water resources. Until now, few methodologies and tools were available to assess and model the fate of diffuse contaminants in groundwater at the regional scale. In this context, the objective of this research was to develop a pragmatic tool to assess and to model groundwater flow and solute transport at the regional scale. A general methodology including the acquisition and the management of data and a new flexible numerical approach was developed. This numerical approach called Hybrid Finite Element Mixing Cell (HFEMC) was implemented in the SUFT3D simulator developed by the Hydrogeology Group of the University of Liège. A first application of this methodology was performed on the Geer basin. The chalk aquifer of the Geer basin is an important resource of groundwater for the city of Liège and its suburbs. The quality of this groundwater resource is threatened by diffuse nitrate contamination mostly resulting from agricultural practices. New field investigations were performed in the basin to better understand the spatial distribution of the nitrate contamination. Samples were taken for environmental tracers (tritium, CFC’s and SF6) analysis. The spatial distribution of environmental tracers concentrations is in concordance with the spatial distribution of nitrates. This allows proposing a coherent interpretative schema of the groundwater flow and solute transport at the regional scale. These new data and the results of a statistical nitrate trend analysis were used to calibrate the groundwater model developed with the HFEMC approach. This groundwater flow and solute transport model was used to forecast the evolution of nitrate concentrations in groundwater under a realistic scenario of nitrate input for the period 2008-2058. According to the modelling results, upward nitrate trends observed in the basin will not be reversed for 2015 as prescribed by the EU Water Framework Directive. The regional scale groundwater solute transport model was subsequently used to compute nitrate concentrations in groundwater under different scenarios of nitrate input to feed a socio-economic analysis performed by BRGM. These computed concentrations were used to assess the benefit, for the users, linked to the reduction of contamination resulting from the changes in nitrate input. These benefits were compared to the costs associated to the implementation of the considered agri-environmental schemes that allow reducing the nitrate input to groundwater. [less ▲]

Comparison of methods for the detection and extrapolation of trends in groundwater quality

in Journal of Environmental Monitoring (2009)

Land use changes and the intensification of agriculture since the 1950s have resulted in a deterioration of groundwater quality in many European countries. For the protection of groundwater quality, it is ... [more ▼]

Land use changes and the intensification of agriculture since the 1950s have resulted in a deterioration of groundwater quality in many European countries. For the protection of groundwater quality, it is necessary to (1) assess the current groundwater quality status, (2) detect changes or trends in groundwater quality, (3) assess the threat of deterioration and (4) predict future changes in groundwater quality. A variety of approaches and tools can be used to detect and extrapolate trends in groundwater quality, ranging from simple linear statistics to distributed 3D groundwater contaminant transport models. In this paper we report on a comparison of four methods for the detection and extrapolation of trends in groundwater quality: (1) statistical methods, (2) groundwater dating, (3) transfer functions, and (4) deterministic modeling. Our work shows that the selection of the method should firstly be made on the basis of the specific goals of the study (only trend detection or also extrapolation), the system under study, and the available resources. For trend detection in groundwater quality in relation to diffuse agricultural contamination, a very important aspect is whether the nature of the monitoring network and groundwater body allows the collection of samples with a distinct age or produces samples with a mixture of young and old groundwater. We conclude that there is no single optimal method to detect trends in groundwater quality across widely differing catchments. [less ▲]

Mobility, turnover and storage of pollutants in soils, sediments and waters: achievements and results of the EU project AquaTerra. A review

in Agronomy for Sustainable Development (2009), 29(1), 161-173

AquaTerra is one of the first environmental projects within the 6th Framework program by the European Commission. It began in June 2004 with a multidisciplinary team of 45 partner organizations from 13 EU ... [more ▼]

AquaTerra is one of the first environmental projects within the 6th Framework program by the European Commission. It began in June 2004 with a multidisciplinary team of 45 partner organizations from 13 EU countries, Switzerland, Serbia, Romania and Montenegro. Results from sampling and modeling in 4 large river basins (Ebro, Danube, Elbe and Meuse) and one catchment of the Brévilles Spring in France led to new evaluations of diffuse and hotspot input of persistent organic and metal pollutants including dynamics of pesticides and polycyclic aromatic hydrocarbons, as well as metal turnover and accumulation. While degradation of selected organic compounds could be demonstrated under controlled conditions in the laboratory, turnover of most persistent pollutants in the field seems to range from decades to centuries. First investigations of long-term cumulative and degradation effects, particularly in the context of climate change, have shown that it is also necessary to consider the predictions of more than one climate model when trying to assess future impacts. This is largely controlled by uncertainties in climate model responses. It is becoming evident, however, that changes to the climate will have important impacts on the diffusion and degradation of pollutants in space and time that are just at the start of their exploration. [less ▲]

Analyse chimique d’eau souterraine au droit de la carrière Marnebel

Report (2008)

Development of the Geer basin Hydrological model for climatic scenarios and first results about impacts evaluation

Report (2008)

A surface – subsurface flow numerical model of the Geer basin (465 km²) has been implemented to assess the possible impacts of climate change on the groundwater resources. This model is physically-based ... [more ▼]

A surface – subsurface flow numerical model of the Geer basin (465 km²) has been implemented to assess the possible impacts of climate change on the groundwater resources. This model is physically-based, spatially-distributed and it integrates totally the groundwater and surface water. Simulations were performed using 6 climate change scenarios generated by the University of Newcastle-Upon-Tyne. These scenarios simulate changes in the amplitude, but also in the frequency and persistence of some meteorological events. First results show that, according the implemented flow model and the used climatic scenarios, significant decreases are expected in the groundwater levels (up to 12 meters) and in the surface water flow rates (reduction between 16% and 32%) [less ▲]

Report on the development of the Geer Hydrological model. Final results about climate change impacts evaluation.

Report (2008)

In the framework of Workpackage BASIN R3 Meuse, the Hydrology Group of the University of Liège (Belgium) has developed a hydrological model of the Geer sub-catchment, in order to assess climate change ... [more ▼]

In the framework of Workpackage BASIN R3 Meuse, the Hydrology Group of the University of Liège (Belgium) has developed a hydrological model of the Geer sub-catchment, in order to assess climate change impacts on groundwater reserves. The water resource Systems Research Laboratory of the Newcastle University has produced the climate change scenarios applied on the hydrological model. This report describes the methodology used, the implementation of the hydrological model, the climate change scenarios and the results of the study. [less ▲]

The Hybrid Finite-Element Mixing-Cell method: a new flexible method for modelling mine water problems

in Rapantova, N.; Hrkal, Z. (Eds.) Mine Water and the Environment Proceedings of IWMA 2008 (2008)

Mine closure is often accompanied by a stop in dewatering operations. This generally induces groundwater rebound in the mined rock system with short and long term consequences that may be disastrous: soil ... [more ▼]

Mine closure is often accompanied by a stop in dewatering operations. This generally induces groundwater rebound in the mined rock system with short and long term consequences that may be disastrous: soil instabilities such as landslides and subsidence reactivation, flooding, flooded basement and acid mine drainage. Modelling tools can be very advantageous and efficient in helping understanding and managing such problems, however, classical modelling approaches have proved to be relatively unsuited to such contexts. Because of the former mining operations, the underground geological system is strongly disturbed (excavated, fractured and collapsed zones, galleries, large shafts, etc.). Using complex spatially distributed modelling approaches such as 3D finite elements usually lead to strong difficulties related to the lack of data, the complexity of geological and hydrogeological conditions (complex geometry, non Darcian fluxes…). On the other hand, using a simplified approach such as black-box models often leads to oversimplification of the reality: particularly when interactions between the mined system and its surrounding geological and hydrogeological environment are very important. A new modelling approach is developed for simulation of the groundwater flow in such complex environments. It combines, in a single fully integrated simulator, a representation of the unmined area by a classical finite element modelling technique, together with conceptualisation of the worked areas and galleries by a group of mixing cells connected by pipes. The whole assembled groundwater flow model allows an accurate estimation and representation of (a) water infiltration (precipitations, river losses …) through the unsaturated zone reaching the exploited area (recharge of boxes) and (b) water exchanges with adjacent aquifers. The model can estimate the flow of groundwater in and around the minefield and the mean water level in the boxes. It is also capable of considering water exchanges between different mined zones, through connection pathways such as old roadways galleries and shafts. Modelling concepts and equations are described and illustrated using basic and advances validation examples. A real case application corresponding to an abandoned coalfield in the region of Liège (Belgium) is used to illustrate the suitability and efficiency of the approach. [less ▲]

Selected groundwater studies of EU project AquaTerra leading to large-scale basin considerations

in Water Practice & Technology (2007), 2(3),

Several local groundwater studies within the EU project AquaTerra in the Basins of the Meuse, Elbe point at significant influences of groundwater on surface water, while the Brévilles Catchment shows a ... [more ▼]

Several local groundwater studies within the EU project AquaTerra in the Basins of the Meuse, Elbe point at significant influences of groundwater on surface water, while the Brévilles Catchment shows a distinct problematic of pesticide loading to groundwater. Further modeling studies are currently being developed. In the Danube Basin no specific groundwater studies were carried out in the framework of AquaTerra. However on larger scales geochemical proxies such as strontium isotope ratios can give an insight into groundwater contributions to the river that reflects an integral signal of the environmental status of the Basin. Future local groundwater studies should be further correlated to the environmental status of rivers nearby. [less ▲]