References of "Dassargues, Alain"
     in
Bookmark and Share    
Full Text
Peer Reviewed
See detailQuantitative temperature monitoring of a heat tracing experiment using cross-borehole ERT
Hermans, Thomas ULg; Wildemeersch, Samuel ULg; Jamin, Pierre ULg et al

in Geothermics (2015), 53

The growing demand for renewable energy leads to an increase in the development of geothermal energy projects and heat has become a common tracer in hydrology and hydrogeology. Designing geothermal ... [more ▼]

The growing demand for renewable energy leads to an increase in the development of geothermal energy projects and heat has become a common tracer in hydrology and hydrogeology. Designing geothermal systems requires a multidisciplinary approach including geological and hydrogeological aspects. In this context, electrical resistivity tomography (ERT) can bring relevant, qualitative and quantitative information on the temperature distribution in operating shallow geothermal systems or during heat tracing experiments. We followed a heat tracing experiment in an alluvial aquifer using cross-borehole time-lapse ERT. Heated water was injected in a well while water of the aquifer was extracted at another well. An ERT section was set up across the main flow direction. The results of ERT were transformed into temperature using calibrated petrophysical relationships. These ERT-derived temperatures were then compared to direct temperature measurements in control piezometers collected with distributed temperature sensing (DTS) and groundwater temperature loggers. Spatially, it enabled to map the horizontal and vertical extent of the heated water plume, as well as the zones where maximum temperatures occurred. Quantitatively, the temperatures and breakthrough curves estimated from ERT were in good agreement with the ones observed directly during the rise and maximum of the curve. An overestimation, likely related to 3D effects, was observed for the tail of the heat breakthrough curve. The error made on temperature can be estimated to be between 10 to 20 %, which is a fair value for indirect measurements. From our data, we estimated a quantification threshold for temperature variation of 1.2°C. These results suggest that ERT should be considered when designing heat tracing experiments or geothermal systems. It could help also to assess the geometrical complexity of the concerned reservoirs. It also appears that ERT could be a useful tool to monitor and control geothermal systems once they are in operation. [less ▲]

Detailed reference viewed: 109 (38 ULg)
Full Text
See detailLanduse change and future flood risk: the influence of micro-scale spatial patterns (FloodLand) - 2nd progress report
Dewals, Benjamin ULg; Bruwier, Martin ULg; El Saeid Mustafa, Ahmed Mohamed ULg et al

Report (2014)

The goal of the project FloodLand is to investigate the complex interactions between landuse change and future flood risk. Landuse change is assumed to be mainly driven by population growth and socio ... [more ▼]

The goal of the project FloodLand is to investigate the complex interactions between landuse change and future flood risk. Landuse change is assumed to be mainly driven by population growth and socio-economic factors. It affects future flood risk by altering catchment hydrology as well as vulnerability in the floodplains; but the feedback effect of (the perception of) changes in flood hazard on landuse evolution is also considered. The research is based on a chain of modelling tools, which represent parts of the natural and human systems, including: landuse change modelling, transportation modelling as an onset for the estimation of indirect flood damage, continuous hydrological modelling (forced by precipitation and temperature data disturbed according to climate change scenarios), as well as efficient hydraulic modelling of inundation flow in the floodplains. Besides reproducing a broad spectrum of processes, the modelling approach spans over multiple scales, from the regional or catchment level down to the floodplain and building levels. This distinctive feature is reflected both within the individual models and through their combination involving fine-scale detailed analyses (or data) embedded within coarser models at a broader level. [less ▲]

Detailed reference viewed: 33 (19 ULg)
Full Text
Peer Reviewed
See detailIntegrated modelling and uncertainty analysis for assessment of climate change effects on groundwater resource
Goderniaux, Pascal; Wildemeersch, Samuel ULg; Dassargues, Alain ULg

Conference (2014, September 15)

Climate change will bring new pressure on surface and groundwater resources (e.g. Allen et al., 2004; Goderniaux et al., 2009; Van Roosmalen et al., 2009) in many parts of the world. Additional work is ... [more ▼]

Climate change will bring new pressure on surface and groundwater resources (e.g. Allen et al., 2004; Goderniaux et al., 2009; Van Roosmalen et al., 2009) in many parts of the world. Additional work is required to help water managers to plan for future changes. For example, most of studies provide projections for a stationary climate representative of the end of the century, although information is demanded for the near-future. A sophisticated transient weather generator (WG) in combination with an integrated surface-subsurface hydrological model (HydroGeoSphere) are used for producing a stochastic generation of large numbers of equiprobable climatic time series, representing transient climate change, and assess impacts on groundwater resources in a probabilistic way. This new methodology is applied for the unconfined chalky aquifer of Hesbaye (Geer basin in Belgium). The following uncertainty sources are studied : (1) the uncertainty linked to the calibration of the hydrological model, using 'UCODE_2005' (Poeter et al., 2005); (2) the uncertainty linked to the global and regional climatic models (GCMs and RCMs), by using a multi-model ensemble; (3) the uncertainty linked to the natural variability of the weather, by using stochastic climate change scenarios. 30 equiprobable climate change scenarios from 2010 to 2085 have been generated for each of 6 different RCMs. Results show that although the 95% confidence intervals calculated around projected groundwater levels remain large, the climate change signal becomes stronger than that of natural climate variability by 2085. Additionally, the WG ability to simulate transient climate change enabled the assessment of the likely timescale and associated uncertainty of a specific impact. This methodology constitutes a real improvement in the field of groundwater projections under climate change conditions as it enables water managers to analyse risks and take decisions with full knowledge of projected impact and their degree of confidence. [less ▲]

Detailed reference viewed: 24 (3 ULg)
Full Text
Peer Reviewed
See detailDevelopping a physically based groundwater vulnerability concept in a DPSIR framework
Beaujean, Jean ULg; Brouyère, Serge ULg; Lemieux, Jean-Michel et al

Conference (2014, September 15)

A general physically based method is presented to assess vulnerability of groundwater to external pressures with respect to quality and/or quantity issues. In the vulnerability assessments, many ... [more ▼]

A general physically based method is presented to assess vulnerability of groundwater to external pressures with respect to quality and/or quantity issues. In the vulnerability assessments, many scientific authors agree nowadays that ‘physically based’ methods must be preferred to traditional approaches based on empirical overlay and index methods where physical attributes are often mixed with implicitly embedded conventional priorities. Results from one or another of these last methods can consequently be very dissimilar for a given case study and decision makers are losing confidence in these tools. A methodology is proposed to reframe the groundwater vulnerability assessment in a Pressure-State-Impact causal chain that is familiar to decision makers. The DPSIR framework, for describing interactions between society and the environment, defines a chain of Drivers that exert Pressures on the State of a given resource, such as water, which then generates an Impact that will require an appropriate Response (Kristensen, 2004). The concept of groundwater vulnerability assessment considered here is based on the calculation of sensitivity coefficients for a user-defined groundwater state for which several physically-based indicators are proposed. These sensitivity coefficients reflect the easiness with which the groundwater state transmits pressures into impacts. They are grouped into a vulnerability matrix of pressures and impacts that quantify vulnerability for every combination of causal links identified in the DPSIR chain. For that reason, the sensitivity coefficients are converted to vulnerability, using the concept of ‘falling below a given threshold’, which is commonly used in socioeconomic sciences (Luers et al. 2003). Outside the careful selection of the sensitivity analysis method that can significantly influence the computational effort (Beaujean et al., 2013), emphasis will be given to the illustration of the general methodology on a simple case (of an alluvial aquifer with concerns related to water supply) demonstrating the potential use of this general and physically based vulnerability assessment method. While the methodology is general, the choice of causal chains has to be made prior to the calculation. The vulnerability is also related to a damaged state and is related to the ‘distance’ between the current state and a given threshold. This choice is arbitrary such that the vulnerability is sensitive to the choice of the threshold. The framework is general and, when applied to water, can include states that are not limited to quality such as, for example, water quantity and availability. [less ▲]

Detailed reference viewed: 30 (4 ULg)
Full Text
See detailLarge-scale stochastic optimization using non-stationary geostatistics for uncertainty assessment of groundwater flow and solute transport, in the framework of a near surface radioactive waste disposal
Rogiers, Bart; Laloy, E.; Gedeon, Matej et al

Poster (2014, July 09)

Uncertainty quantification is very much needed to support decision making related to e.g. environmental impact assessment for waste disposal sites. A probabilistic result provides a much stronger basis ... [more ▼]

Uncertainty quantification is very much needed to support decision making related to e.g. environmental impact assessment for waste disposal sites. A probabilistic result provides a much stronger basis for decision making compared to a single deterministic outcome. Accurate posterior exploration of high-dimensional and CPU-intensive models, which are often used for environmental impact assessment, is however a challenging task. To quantify the uncertainty associated with solute transport in the framework of a near surface radioactive waste disposal in Mol/Dessel, Belgium, we investigate combining the adaptive Metropolis (AM) McMC algorithm for updating the global model parameters, and adaptive spatial resampling (ASR) for updating of the spatially distributed model parameters, by block sampling. The forward model used is a groundwater flow model conditioned on borehole and direct push data, that accounts for non-stationary heterogeneity in hydraulic conductivity. The obtained flow solutions are used for solute transport simulations, and the results are compared with a different groundwater flow model parameterization, that makes use of homogeneous hydrogeological layers. Moreover, a number of simulations is performed to assess the effect of realistic dispersivity, which is derived from outcrop investigations. The obtained results indicate that the combination of AM and ASR using block sampling seems not to be very efficient for McMC sampling with the forward model used in this study. However, using the algorithm in optimization mode seems to work fine, and provides an alternate way for exploring the parameter space and the prediction uncertainty. [less ▲]

Detailed reference viewed: 19 (0 ULg)
Full Text
See detailApplication of multiple-point geostatistics on groundwater flow and transport in media with complex geological heterogeneity: lessons learnt and remaining challenges
Huysmans, Marijke; Dassargues, Alain ULg

in Proceedings (2014, July 09)

Multiple-point geostatistics has been increasingly applied on groundwater problems in the last ten years. Several case studies have been published indicating simulating realistic geological heterogeneity ... [more ▼]

Multiple-point geostatistics has been increasingly applied on groundwater problems in the last ten years. Several case studies have been published indicating simulating realistic geological heterogeneity using multiple-point geostatistics can significantly improve groundwater flow and solute transport predictions. There are however several remaining challenges when applying multiple-point geostatistics to groundwater problems often suffering from data scarcity. These challenges might be the reason why multiple-point has been used to a much lesser extent by practitioners than by researchers. This paper gives an overview of the current challenges and discusses new advancements to overcome them. The following questions will be discussed: How to obtain 3D training images? Can the representativity of the used training image be validated ? How sensitive are groundwater calculations to the selection of the training image? Is it worth incorporating fine scale geological heterogeneity in groundwater problems or are other features (boundary conditions, data uncertainty/quality, …) more important for improving predictions? How can multiple-point geostatistics be used without suffering from very long computation times for the numerical models? Is overparametrization of groundwater models an issue ? What are the practical obstacles to apply multiple-point geostatistics by groundwater practitioners? [less ▲]

Detailed reference viewed: 16 (2 ULg)
Full Text
Peer Reviewed
See detailGéothermie de très basse température
Dassargues, Alain ULg; Wildemeersch, Samuel ULg

in Dassargues, Alain; Walraevens, Kristine (Eds.) Watervoerende lagen & grondwater in België - Aquifères & eaux souterraines en Belgique (2014)

Detailed reference viewed: 30 (6 ULg)
Full Text
Peer Reviewed
See detailHydrogéologie et grands travaux du Génie Civil - Hydrogeologie en grote civieltechnische werken
Schroeder, Christian; Huysmans, Marijke; Dassargues, Alain ULg

in Dassargues, Alain; Walraevens, Kristine (Eds.) Watervoerende lagen & grondwater in België - Aquifères & eaux souterraines en Belgique (2014)

Detailed reference viewed: 22 (6 ULg)
See detailAquifères et Eaux Souterraines en Belgique - Watervoerende Lagen en Grondwater in Belgïe
Dassargues, Alain ULg; Walraevens, Kristine

Book published by Academia Press (2014)

Detailed reference viewed: 29 (12 ULg)
Full Text
Peer Reviewed
See detailAquifère crayeux de Hesbaye
Orban, Philippe ULg; Brouyère, Serge ULg; Compère, Jean-michel et al

in Dassargues, Alain; Walraevens, Kristine (Eds.) Watervoerende lagen en grondwater in Belgïe - Aquifères et eaux souterraines en Belgique (2014)

Detailed reference viewed: 24 (13 ULg)
Full Text
Peer Reviewed
See detailRemontées des nappes dans les anciens travaux miniers et activités de démergement - Modélisation hydrogéologique spécifique et exemple de la zone minière de Cheratte
Dassargues, Alain ULg; Wildemeersch, Samuel ULg; Orban, Philippe ULg et al

in Dassargues, Alain; Walraevens, Kristine (Eds.) Watervoerende lagen & grondwater in Belgïe – Aquifères & eaux souterraines en Belgique (2014)

Detailed reference viewed: 18 (2 ULg)
Full Text
Peer Reviewed
See detailGraviers de la Meuse (alluvions modernes et anciennes) en Wallonie
Dassargues, Alain ULg; Wildemeersch, Samuel ULg; Rentier, Céline

in Dassargues, Alain; Walraevens, Kristine (Eds.) Watervoerende lagen & grondwater in België - Aquifères & eaux souterraines en Belgique (2014)

Detailed reference viewed: 19 (5 ULg)
Full Text
Peer Reviewed
See detailIntroduction générale et description du contexte hydrogéologique en Belgique - Algemene inleiding en beschrijving van de hydrogeologische context in Belgïe
Walraevens, Kristine; Biron, Jean-Paul; Dassargues, Alain ULg

in Dassargues, Alain; Walraevens, Kristine (Eds.) Watervoerende lagen & grondwater in België - Aquifères & eaux souterraines en Belgique (2014)

Detailed reference viewed: 11 (4 ULg)
Full Text
Peer Reviewed
See detailAquifères de l'Ardenne
Debbaut, Vincent ULg; Cajot, Odette; Ruthy, Ingrid ULg et al

in Dassargues, Alain; Walraevens, Kristine (Eds.) Watervoerende lagen & grondwater in België - Aquifères & eaux souterraines en Belgique (2014)

Detailed reference viewed: 25 (11 ULg)
Full Text
Peer Reviewed
See detailCrétacé du Pays de Herve
Ruthy, Ingrid ULg; van Ellen, Tjaard; Dassargues, Alain ULg

in Dassargues, Alain; Walraevens, Kristine (Eds.) Watervoerende lagen & grondwater in België - Aquifères & eaux souterraines en Belgique (2014)

Detailed reference viewed: 30 (20 ULg)
Full Text
Peer Reviewed
See detailMulti-scale aquifer characterization and groundwater flow model parameterization using direct push technologies
Rogiers, Bart; Vienken, Thomas; Gedeon, Matej et al

in Environmental Earth Sciences (2014)

Direct push (DP) technologies are typically used for cost-effective geotechnical characterization of unconsolidated soils and sediments. In more recent developments, DP technologies have been used for ... [more ▼]

Direct push (DP) technologies are typically used for cost-effective geotechnical characterization of unconsolidated soils and sediments. In more recent developments, DP technologies have been used for efficient hydraulic conductivity (K) characterization along vertical profiles with sampling resolutions of up to a few centimetres. Until date, however, only a limited number of studies document high-resolution in situ DP data for three-dimensional conceptual hydrogeological model development and groundwater flow model parameterization. This study demonstrates how DP technologies improve building of a conceptual hydrogeological model. We further evaluate the degree to which the DP-derived hydrogeological parameter K, measured across different spatial scales, improves performance of a regional groundwater flow model. The study area covers an area of ~60 km² with two overlying, mainly unconsolidated sand, aquifers separated by a 5-7 m thick highly heterogeneous clay layer (in north-eastern Belgium). The hydrostratigraphy was obtained from an analysis of cored boreholes and about 265 cone penetration tests (CPTs). The hydrogeological parameter K was derived from a combined analysis of core and CPT data and also from hydraulic direct push tests. A total of 50 three-dimensional realizations of K were generated using a non-stationary multivariate geostatistical approach. To preserve the measured K values in the stochastic realizations, the groundwater model Krealizations were conditioned on the borehole and direct push data. Optimization was performed to select the best performing model parameterization out of the 50 realizations. This model outperformed a previously developed reference model with homogeneous K fields for all hydrogeological layers. Comparison of particle tracking simulations, based either on the optimal heterogeneous or reference homogeneous groundwater model flow fields, demonstrate the impact DP-derived subsurface heterogeneity in K can have on groundwater flow and solute transport. We demonstrated that DP technologies, especially when calibrated with site-specific data, provide high-resolution 3D subsurface data for building more reliable conceptual models and increasing groundwater flow model performance. [less ▲]

Detailed reference viewed: 11 (3 ULg)
Full Text
Peer Reviewed
See detailCalcaires et grès des bassins de la Vesdre et de la Gueule
Ruthy, Ingrid ULg; Biron, Jean-Paul; Dassargues, Alain ULg

in Dassargues, Alain; Walraevens, Kristine (Eds.) Watervoerende lagen & grondwater in België - Aquifères & eaux souterraines en Belgique (2014)

Detailed reference viewed: 12 (4 ULg)
Full Text
See detailLanduse change and future flood risk: the influence of micro-scale spatial patterns (FloodLand) - 1st progress report
Dewals, Benjamin ULg; Bruwier, Martin ULg; El Saeid Mustafa, Ahmed Mohamed ULg et al

Report (2014)

The goal of the project FloodLand is to investigate the complex interactions between landuse change and future flood risk. Landuse change is assumed to be mainly driven by population growth and socio ... [more ▼]

The goal of the project FloodLand is to investigate the complex interactions between landuse change and future flood risk. Landuse change is assumed to be mainly driven by population growth and socio-economic factors. It affects future flood risk by altering catchment hydrology as well as vulnerability in the floodplains; but the feedback effect of (the perception of) changes in flood hazard on landuse evolution is also considered. The research is based on a chain of modelling tools, which represent parts of the natural and human systems, including: landuse change modelling, transportation modelling as an onset for the estimation of indirect flood damage, continuous hydrological modelling (forced by precipitation and temperature data disturbed according to climate change scenarios), as well as efficient hydraulic modelling of inundation flow in the floodplains. Besides reproducing a broad spectrum of processes, the modelling approach spans over multiple scales, from the regional or catchment level down to the floodplain and building levels. This distinctive feature is reflected both within the individual models and through their combination involving fine-scale detailed analyses (or data) embedded within coarser models at a broader level. [less ▲]

Detailed reference viewed: 15 (11 ULg)