References of "Environmental Geology"
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See detailA framework for an optimised groundwater monitoring network and aggregated indicators
Rentier, Céline; Delloye, Francis; Brouyère, Serge ULg et al

in Environmental Geology (2006), 50(2), 194-201

The implementation of the Water Framework Directive (EU 2000) requires a groundwater quality monitoring. It is used for characterisation of the 'good' chemical status of each groundwater body and for the ... [more ▼]

The implementation of the Water Framework Directive (EU 2000) requires a groundwater quality monitoring. It is used for characterisation of the 'good' chemical status of each groundwater body and for the restoration or protection purposes of those bodies already at 'good' status. Interpretative aspects are lying in the design of monitoring network and in the way of building global indicators. Attention is given here to the global chemical status of the groundwater bodies and to the role of diffuse pollution, much of which is brought via groundwater to surface water. Monitoring 'local' pollution associated with individual sites is not addressed. Groundwater bodies with different contrasted hydrogeology conditions, land use and topography have been considered to establish an approach for choosing an optimised monitoring network. Then, a quality assessment system has been developed and applied for qualifying the general status of each groundwater body. The use of non-dimensional indexes allows us to process with all kinds of chemical parameters in a normalised way and, by means of adequate aggregation rules, to qualify the general quality status of a groundwater body. The obtained diagnostic, even if not fully validated, is closely linked to the pragmatic objectives contained in the EU Water Directive. [less ▲]

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See detailHydrogeological modeling of radionuclide transport in low permeability media: a comparison between Boom Clay and Ypresian Clay
Huysmans, Marijke; Dassargues, Alain ULg

in Environmental Geology (2006), 50(1), 122-131

Deep low-permeability clay layers are considered as suitable environments for disposal of high-level radioactive waste. In Belgium, the Boom Clay is the reference host formation and the Ypresian Clay an ... [more ▼]

Deep low-permeability clay layers are considered as suitable environments for disposal of high-level radioactive waste. In Belgium, the Boom Clay is the reference host formation and the Ypresian Clay an alternative host formation for research and safety and feasibility assessment of deep disposal of nuclear waste. In this study, two hydrogeological models are built to calculate the radionuclide fluxes that would migrate from a potential repository through these two clay formations. Transport parameter heterogeneity is incorporated in the models using geostatistical co-simulations of hydraulic conductivity, diffusion coefficient and diffusion accessible porosity. The calculated radionuclide fluxes in the two clay formations are compared. The results show that in the Ypresian Clay larger differences between the fluxes through the lower and the upper clay boundary occur, larger total output radionuclide amounts are calculated and a larger effect of parameter heterogeneity on the calculated fluxes is observed, compared to the Boom Clay. [less ▲]

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See detailRisk assessment of groundwater pollution using sensitivity analysis and a worst-case scenario analysis
Huysmans, Marijke; Madarasz, Tamas; Dassargues, Alain ULg

in Environmental Geology (2006), 50(2), 180-193

This paper illustrates how sensitivity analysis and a worst-case scenario analysis can be useful tools in risk assessment of groundwater pollution. The approach is applied to a study area in Hungary with ... [more ▼]

This paper illustrates how sensitivity analysis and a worst-case scenario analysis can be useful tools in risk assessment of groundwater pollution. The approach is applied to a study area in Hungary with several known groundwater pollution sources and nearby drinking water production wells. The main concern is whether the contamination sources threaten the drinking water wells of the area. A groundwater flow and transport model is set up to answer this question. Due to limited data availability, the results of this model are associated with large uncertainty. Sensitivity analysis and a worst-case scenario analysis are applied to estimate this uncertainty and build confidence in the model results. [less ▲]

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See detailStochastic analysis of the effect of heterogeneity and fractures on radionuclide transport in a low-permeability clay layer
Huysmans, Marijke; Dassargues, Alain ULg

in Environmental Geology (2005), 48(7), 920-930

Deep low-permeability clay layers are considered as safe environments for disposal of high-level radioactive waste. In Belgium, the Boom Clay is a candidate host rock for deep geological disposal. In this ... [more ▼]

Deep low-permeability clay layers are considered as safe environments for disposal of high-level radioactive waste. In Belgium, the Boom Clay is a candidate host rock for deep geological disposal. In this study, we analyze the effects of fractures and spatially variable hydraulic conductivity on radionuclide migration through the clay. Fracture geometry and properties are simulated with Monte Carlo simulation. The heterogeneity of hydraulic conductivity is simulated by direct sequential co-simulation using measurements of hydraulic conductivity and four types of secondary variables. The hydraulic conductivity and fracture simulations are used as input for a transport model. Radionuclide fluxes computed with this heterogeneous model are compared with fluxes obtained with a homogeneous model. The output fluxes of the heterogeneous model differ at most 8% from the homogeneous model. The main safety function of the Boom Clay is thus not affected by the fractures and the spatial variability of hydraulic conductivity. [less ▲]

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See detailModelling seasonal variations in nitrate and sulphate concentrations in a vulnerable alluvial aquifer
Peeters, Luk; Haerens, Bruno; Van der Sluys, Jan et al

in Environmental Geology (2004), 46(6-7), 951-961

The Eisden-Meeswijk region in Belgium has been affected by mining subsidence due to the deep coal mining activities. Groundwater levels in the alluvial plain of the Meuse River are maintained below the ... [more ▼]

The Eisden-Meeswijk region in Belgium has been affected by mining subsidence due to the deep coal mining activities. Groundwater levels in the alluvial plain of the Meuse River are maintained below the ground surface by drainage installations and municipal well fields. A correlation between the water level in the Meuse River and the variation in nitrate and sulphate concentrations in the aquifer has been observed. A transient groundwater model is developed for the period May 1998-May 2002 and advective transport simulations have been carried out using this model. During dry periods, the major groundwater flow is directed towards the Meuse River, thereby feeding the river. During wet periods, however, groundwater flows in the opposite direction. Due to these variations in groundwater flow direction and to the extraction of groundwater, zones of higher solute concentration exist of which the position and extension vary both spatially and temporally. [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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See detailCurrent and future trends in groundwater vulnerability assessment
Gogu, Radu; Dassargues, Alain ULg

in Environmental Geology (2000), 39(6), 549-559

The concept of groundwater vulnerability is a useful tool for environmental planning and decision-making. Many different methods have been developed for assessing this vulnerability. Hydrogeologists have ... [more ▼]

The concept of groundwater vulnerability is a useful tool for environmental planning and decision-making. Many different methods have been developed for assessing this vulnerability. Hydrogeologists have failed to reach a consensus concerning the definitions of and reference terms for groundwater vulnerability assessment. Therefore, a review of vulnerability assessment and mapping methods providing a new classification system is necessary. This is focused on techniques that use the overlay and index class methods. New research challenges in vulnerability assessment are identified, especially the need for developing dynamic links between numerical models and overlay and index methods. [less ▲]

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See detailDelineation of groundwater protection zones based on tracer tests and transport modelling in alluvial sediments
Derouane, Johan; Dassargues, Alain ULg

in Environmental Geology (1998), 36(1-2), 27-36

Regulations aiming to protect exploitable groundwater resources were edicted in Belgium a few years ago. Therefore, prevention and protection zones are defined by law and must be determined practically ... [more ▼]

Regulations aiming to protect exploitable groundwater resources were edicted in Belgium a few years ago. Therefore, prevention and protection zones are defined by law and must be determined practically around each pumping well or spring, based on local hydrogeological conditions. The determination of hydrodynamic and hydrodispersive parameters, characterizing the local flow and transport properties of the aquifer, requires pumping and tracing tests. The interpretation of these field experiments, considering the heterogeneity of the geological layers, is performed through the use of numerical FEM simulations of the groundwater flow and pollutant transport conditions in a deterministic framework. After calibration of the model on experimental measurements, multiple simulations with contaminant injections at various points of the modeled domain allow the determination of the transfer time of the pollutant in the studied aquifer whilst taking the updated heterogeneity into account. On the basis of the computed transfer times in the saturated zone, the various prevention and protection areas can be assessed based on provisions of the law. [less ▲]

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