References of "Orban, Philippe"
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See detailComparison of temperature from DTS and ERT with direct measurements during heat tracer experiments in heterogeneous aquifers
Nguyen, Frédéric ULg; Hermans, Thomas ULg; Jamin, Pierre ULg et al

Conference (2016, September 27)

Geothermal field characterization and heat tracer experiments often rely on scarce temperature data collected in boreholes. Electrical resistivity tomography (ERT) and distributed temperature sensing (DTS ... [more ▼]

Geothermal field characterization and heat tracer experiments often rely on scarce temperature data collected in boreholes. Electrical resistivity tomography (ERT) and distributed temperature sensing (DTS) have the potential to provide spatial information on temperature changes in the subsurface. In this contribution, we show how DTS and ERT have been used to investigate the heterogeneity of a heterogeneous aquifer during a heat tracing experiment under forced gradient conditions. Optic fibers were installed in the heat injection well and in two piezometers intersecting the main flow directions at 8 m from the injection well. These piezometers were also equipped with ERT. The DTS measurement in the injection well clearly shows the two-layer nature of the aquifer. After the end of injection, the temperature in the bottom part of the well decreases faster than in the upper part due to the higher water fluxes. Those results are confirmed by DTS measurements in natural flow conditions during a heating wire test. DTS and ERT in the cross-panel both show the vertical and lateral heterogeneity of the aquifer. Temperatures only increase significantly in the bottom part of the aquifer where advection is predominant. However, strong differences are observed laterally. ERT additionally shows that the hot plume is divided in two main flow paths, which is confirmed by direct temperature measurements. The comparison of DTS and ERT shows that one of the well is suffering from water mixing. Indeed, temperature from DTS are homogeneous over the whole tichkness of the aquifer, whereas ERT temperature, less affected by local variations, are varying. Our study demonstrate the value of spatially distributed measurements for the monitoring of heat tracer experiment and highligths the issue of multilevel sampling. The detailed temperature measurements can be subsequently used in hydrogeological model to better estimates heat flow and transport parameters. [less ▲]

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See detailHow groundwater interactions can influence UPSH (Underground Pumping Storage Hydroelectricity) operations
Bodeux, Sarah ULg; Pujades, Estanislao ULg; Orban, Philippe ULg et al

Conference (2016, July 28)

In the current energy grid, renewable energy has an increasing role to play. However, their intermittence cannot afford to regulate the produced electricity according to the irregular demand (Evans et al ... [more ▼]

In the current energy grid, renewable energy has an increasing role to play. However, their intermittence cannot afford to regulate the produced electricity according to the irregular demand (Evans et al., 2012). Pumped Storage Hydroelectricity (PSH) is a well-known efficient technology to store and release electricity according to the demand needs but appropriate potential new sites are getting scarce (Steffen, 2012). An innovative alternative consists in using abandoned mines as lower reservoir of an Underground Pumping Storage Hydroelectricity (UPSH) plant. In such configuration, large amount of water will be pumped or injected in underground cavities, creating subsequently head oscillations in the surrounding aquifers. Consequently, this seepage occurring between the considered cavity and the varying groundwater heads in the surrounding geological medium may influence the efficiency of the UPSH plant but also the magnitude of the potential impacts on the groundwater resources. A hybrid 3D finite element mixing cell method (Brouyère et al., 2009) is used to simulate numerically the use of a representative UPSH cavity and calculate the induced changes in groundwater heads in the surrounding geological medium. Different scenarios are computed varying parameter values (hydrogeological and lower reservoir characteristics), boundary conditions, and pumping/injection time-sequences. By analyzing the computed piezometric heads at different distances from the underground reservoir, the magnitude of the aquifer response to pumping storage operations is assessed. The most expected and noticeable effect is the oscillation of groundwater levels. The existence a mean pseudo/ dynamic steady-state and the required time to reach it are also determined. The head difference and its time evolution between the cavity and the surrounding medium is triggering the leakage of groundwater into the cavity or the contrary. The resulting effects on the UPSH plant efficiency can be estimated. Combining these outcomes, some feasibility criteria of this type of projects are identified. Going into practice, further models should include more in de-tails local and specific geometrical and hydrogeolog-ical data of the considered old mine cavities used as lower reservoir. This kind of modelling approach can be used as a first approach for determining how the aquifer will response to short and long term changes in UPSH pumping/injection schemes. [less ▲]

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See detailGroundwater flow and transport modelling at regional scale: lessons learned from different applications in the Walloon Meuse basin
Dassargues, Alain ULg; Goderniaux, Pascal; Orban, Philippe ULg et al

Conference (2016, July 28)

An overview is proposed of the recent groundwater modelling works, at the groundwater body scale, performed by the Hydrogeology & Environmental Geology team of the University of Liège. The developed ... [more ▼]

An overview is proposed of the recent groundwater modelling works, at the groundwater body scale, performed by the Hydrogeology & Environmental Geology team of the University of Liège. The developed modelling tools are built in the general objective of improving our understanding and management, at short, middle and long terms, of the groundwater bodies. The general strategy to be followed implies that conceptualization, parameterization and calibration must be adapted to the actual objectives of each model (Wildemeersch et al., 2014). 3 specific applications are illustrated involving two main groundwater bodies: - application of the HFEMC method (Wildemeersch et al., 2010) within the SUFT3D code for groundwater flow modelling of the ‘Synclinorium of Dinant’ (Orban et al., 2010 and Brouyère et al., 2011); - application of the HFEMC method and the SUFT3D code for the nitrate trends (Batlle-Aguilar et al., 2007) simulations in the Geer basin (Orban et al., 2010) for different scenarios of nitrate inputs; - application of the HGS integrated model for assessing the impact of climate change on the groundwater reserves in the Geer basin (Brouyère et al., 2004, Goderniaux et al., 2009 and 2011) with quantification and comparison of the different uncertainty sources (Goderniaux et al., 2015) Lessons and perspectives are learned and proposed from these modelling experiences at the scale of the groundwater body. [less ▲]

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See detailNitrate dynamic and pathways in fractured limestone aquifers : From soil leaching to groundwater discharge in surface water
Briers, Pierre ULg; Schmit, Flore; Orban, Philippe ULg et al

Conference (2016, July 27)

Fractured – karstified limestone aquifers constitute important, but vulnerable groundwater reservoirs in many areas across the World. Such carbonate systems are highly heterogeneous leading to a high ... [more ▼]

Fractured – karstified limestone aquifers constitute important, but vulnerable groundwater reservoirs in many areas across the World. Such carbonate systems are highly heterogeneous leading to a high spatial and temporal variability of fluxes across the soil – vadose zone – groundwater – surface water continuum. One of the main challenges worldwide is to protect such groundwater bodies from diffuse pollutions, in particular agricultural chemicals such as nitrate. To face such problems and to propose adequate pollution mitigation scenarios, the objective here was to better understand and quantify nitrate dynamics and pathways in the subsurface and at the groundwater – surface water interface. The transfer of nitrate was investigated in different ways such as monitoring of concentrations in both groundwater and surface water, tracer experiments in the unsaturated – saturated continuum and regional investigations on groundwater chemistry including stable isotopes of nitrate and other compounds. Results show that nitrate concentrations are relatively stable both in groundwater and surface water during the low flow period (i.e. from spring to autumn). A temporary but significant increase in nitrate concentration is observed in groundwater and rivers during the winter, related to release of residual nitrate from agricultural soils driven by infiltration water. In period of high precipitations and runoff, dilution is measured in the river. Monitoring and tracer test results also highlight the fact that the migration of dissolved contaminants across the unsaturated zone of limestone rocks is very fast and governed by gravitational flows. In the rivers, macroinvertebrates and benthic diatoms were sampled at several sites to assess ecological status and structural and functional response to alteration of water quality (nutrient enrichment) and quantity (current velocity and stream habitats). Diatom indices and community structure indicated good to very good status in both studied streams, indicating that elevated nitrate concentration have no detectable effect on biological quality of the surface waters. The combination of all these results allows developing a detailed conceptual model of the dynamics of nitrate (and other agricultural contaminants) in fractured / karstified limestone aquifers, with improved estimates of nitrate trends and dynamics in both groundwater and rivers. [less ▲]

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See detailFactors controlling spatial patterns and time trends of multiple pesticides in groundwater (Hesbaye chalk aquifer, Belgium)
Hakoun, Vivien ULg; Orban, Philippe ULg; Dassargues, Alain ULg et al

Conference (2016, July 25)

Groundwater contamination by pesticides compounds (parent and degradation by-products) is a well identified environmental issue, however factors influencing their spatial patterns and time trends remain ... [more ▼]

Groundwater contamination by pesticides compounds (parent and degradation by-products) is a well identified environmental issue, however factors influencing their spatial patterns and time trends remain unclear. In this context, 18 years long time series (1996-2013) of 3 banned (atrazine, diuron, simazine), 2 metabolites (deethyaltrazine –DEA, and 2,6-dichlorobenzamide –BAM) and one regulated (bentazone) pesticides compounds are explored, taking into account concentrations below detection limits. Using a bivariate and multivariate (PCA and hierarchical clustering) statistical framework, these time series are related to nitrate (NO3-) and the fraction of young water recharged since 50 years, land use, to aquifer settings (i.e. confining conditions, thickness of the unsaturated zone) and to groundwater table fluctuations. Results show that pesticides compounds are always below detection limits in the confined area where old groundwater lies. However these compounds are detected every year in the unconfined zone with maximal concentrations exceeding the current European water drinking standard of 100 ng.L-1 every year since 2007 for atrazine. We find the greatest significant (p-value < 0.05) positive correlations between the trio atrazine-DEA (tau=0.62), atrazine-NO3- (tau=0.48) and DEA-NO3- (tau=0.49). We identify positive correlations between most compounds, atrazine (tau=0.44), bentazone (tau=0.36), simazine (tau=0.71); DEA (tau=0.58) and BAM (tau=0.44), and water table fluctuations with periods spanning several years. We determine two groups (6 and 9 sites each) of site which relate to the discharge and recharge areas. Sites from the recharge area where higher diuron, simazine and BAM concentrations occurs correlate with a dense localized urban area. Atrazine and bentazone relates to sites with thin unsaturated zones and high mixing in the wells. Our analysis reveals critical factors affecting 7 pesticides compounds. It improves our understanding of the interplay between land use, aquifer settings and transient processes (water fluctuations) on controlling pesticides concentrations in groundwater. [less ▲]

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See detailHeat tracer test in an alluvial aquifer: field experiment and inverse modelling
Klepikova, Maria; Wildemeersch, Samuel; Hermans, Thomas ULg et al

in Journal of Hydrology (2016), 540

Using heat as an active tracer for aquifer characterization is a topic of increasing interest. In this study, we investigate the potential of using heat tracer tests for characterization of a shallow ... [more ▼]

Using heat as an active tracer for aquifer characterization is a topic of increasing interest. In this study, we investigate the potential of using heat tracer tests for characterization of a shallow alluvial aquifer. A thermal tracer test was conducted in the alluvial aquifer of the Meuse River, Belgium. The tracing experiment consisted in simultaneously injecting heated water and a dye tracer in an injection well and monitoring the evolution of groundwater temperature and tracer concentration in the pumping well and in measurement intervals. To get insights in the 3D characteristics of the heat transport mechanisms, temperature data from a large number of observation wells closely spaced along three transects were used. Temperature breakthrough curves in observation wells are contrasted with what would be expected in an ideal layered aquifer. They reveal strongly unequal lateral and vertical components of the transport mechanisms. The observed complex behavior of the heat plume is explained by the groundwater flow gradient on the site and heterogeneities in the hydraulic conductivity field. Moreover, due to high injection temperatures during the field experiment a temperature-induced fluid density effect on heat transport occurred. By using a flow and heat transport numerical model with variable density coupled with a pilot point approach for inversion of the hydraulic conductivity field, the main preferential flow paths were delineated. The successful application of a field heat tracer test at this site suggests that heat tracer tests is a promising approach to image hydraulic conductivity field. This methodology could be applied in aquifer thermal energy storage (ATES) projects for assessing future efficiency that is strongly linked to the hydraulic conductivity variability in the considered aquifer. [less ▲]

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See detailUnderground pumped storage hydroelectricity using abandoned works (deep mines or open pits) and the impact on groundwater flow
Pujades, Estanislao ULg; Willems, Thibault ULg; Bodeux, Sarah ULg et al

in Hydrogeology Journal (2016)

Underground pumped storage hydroelectricity (UPSH) plants using open-pit or deep mines can be used in flat regions to store the excess of electricity produced during low-demand energy periods. It is ... [more ▼]

Underground pumped storage hydroelectricity (UPSH) plants using open-pit or deep mines can be used in flat regions to store the excess of electricity produced during low-demand energy periods. It is essential to consider the interaction between UPSH plants and the surrounding geological media. There has been little work on the assessment of associated groundwater flow impacts. The impacts on groundwater flow are determined numerically using a simplified numerical model which is assumed to be representative of open-pit and deep mines. The main impact consists of oscillation of the piezometric head, and its magnitude depends on the characteristics of the aquifer/geological medium, the mine and the pumping and injection intervals. If an average piezometric head is considered, it drops at early times after the start of the UPSH plant activity and then recovers progressively. The most favorable hydrogeological conditions to minimize impacts are evaluated by comparing several scenarios. The impact magnitude will be lower in geological media with low hydraulic diffusivity; however, the parameter that plays the more important role is the volume of water stored in the mine. Its variation modifies considerably the groundwater flow impacts. Finally, the problem is studied analytically and some solutions are proposed to approximate the impacts, allowing a quick screening of favorable locations for future UPSH plants. [less ▲]

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See detailMines as lower reservoir of an UPSH (Underground Pumped Storage Hydroelectricity): groundwater impacts and feasibility
Bodeux, Sarah ULg; Pujades, Estanislao ULg; Orban, Philippe ULg et al

Poster (2016, April 20)

The energy framework is currently characterized by an expanding use of renewable sources. However, their inter- mittence could not afford a stable production according to the energy demand. Pumped Storage ... [more ▼]

The energy framework is currently characterized by an expanding use of renewable sources. However, their inter- mittence could not afford a stable production according to the energy demand. Pumped Storage Hydroelectricity (PSH) is an efficient possibility to store and release electricity according to the demand needs. Because of the topographic and environmental constraints of classical PSH, new potential suitable sites are rare in countries whose topography is weak or with a high population density. Nevertheless, an innovative alternative is to construct Underground Pumped Storage Hydroelectricity (UPSH) plants by using old underground mine works as lower reservoir. In that configuration, large amount of pumped or injected water in the underground cavities would impact the groundwater system. A representative UPSH facility is used to numerically determine the interactions with surrounding aquifers Different scenarios with varying parameters (hydrogeological and lower reservoir char- acteristics, boundaries conditions and pumping/injection time-sequence) are computed. Analysis of the computed piezometric heads around the reservoir allows assessing the magnitude of aquifer response and the required time to achieve a mean pseudo-steady state under cyclic solicitations. The efficiency of the plant is also evaluated taking the leakage into the cavity into account. Combining these two outcomes, some criterions are identified to assess the feasibility of this type of projects within potential old mine sites from a hydrogeological point of view. [less ▲]

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See detailHeat tracer test in an alluvial aquifer: field experiment and inverse modelling
Klepikova, Maria; Wildemeersch, Samuel; Jamin, Pierre ULg et al

Poster (2016, April 20)

Using heat as an active tracer for aquifer characterization is a topic of increasing interest. In this study, we investigate the potential of using heat tracer tests for characterization of a shallow ... [more ▼]

Using heat as an active tracer for aquifer characterization is a topic of increasing interest. In this study, we investigate the potential of using heat tracer tests for characterization of a shallow alluvial aquifer. A thermal tracer test was conducted in the alluvial aquifer of the Meuse River, Belgium. The tracing experiment consisted in simultaneously injecting heated water and a dye tracer in a piezometer and monitoring the evolution of groundwater temperature and tracer concentration in the recovery well and in monitoring wells. To get insights in the 3D characteristics of the heat transport mechanisms, temperature data from a large number of observation wells distributed throughout the field site (space-filling arrangement) were used. Temperature breakthrough curves in observation wells are contrasted with what would be expected in an ideal layered aquifer. They reveal strongly unequal lateral and vertical components of the transport mechanisms. The observed complex behavior of the heat plume was explained by the groundwater flow gradient on the site and heterogeneity of hydraulic conductivity field. Moreover, due to high injection temperatures during the field experiment a temperature-induced fluid density effect on heat transport occurred. By using a flow and heat transport numerical model with variable density coupled with the pilot point inverse approach, main preferential flow paths were delineated. [less ▲]

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See detailUnderground Pumped Storage Hydropower using abandoned open pit mines: influence of groundwater seepage on the system efficiency
Pujades, Estanislao ULg; Bodeux, Sarah ULg; Orban, Philippe ULg et al

Poster (2016, April)

Pumped Storage Hydropower (PSH) plants can be used to manage the production of electrical energy according to the demand. These plants allow storing and generating electricity during low and high demand ... [more ▼]

Pumped Storage Hydropower (PSH) plants can be used to manage the production of electrical energy according to the demand. These plants allow storing and generating electricity during low and high demand energy periods, respectively. Nevertheless, PSH plants require a determined topography because two reservoirs located at different heights are needed. At sites where PSH plants cannot be constructed due to topography requirements (flat regions), Underground Pumped Storage Hydropower (UPSH) plants can be used to adjust the electricity production. These plants consist in two reservoirs, the upper one is located at the surface (or at shallow depth) while the lower one is underground (or deeper). Abandoned open pit mines can be used as lower reservoirs but these are rarely isolated. As a consequence, UPSH plants will interact with surrounding aquifers exchanging groundwater. Groundwater seepage will modify hydraulic head inside the underground reservoir affecting global efficiency of the UPSH plant. The influence on the plant efficiency caused by the interaction between UPSH plants and aquifers will depend on the aquifer parameters, underground reservoir properties and pumping and injection characteristics. The alteration of the efficiency produced by the groundwater exchanges, which has not been previously considered, is now studied numerically. A set of numerical simulations are performed to establish in terms of efficiency the effects of groundwater exchanges and the optimum conditions to locate an UPSH plant. [less ▲]

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See detailRessources en eau au Bénin: Problématique, enjeux et défis d’une gestion durable
Tossou, Yao ULg; Orban, Philippe ULg; Ruthy, Ingrid ULg et al

Scientific conference (2016, March 12)

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See detailHow heterogeneity of the K-field influences a heat plume in a shallow alluvial aquifer: responses from a heat tracer test
Klepikova, Maria; Jamin, Pierre ULg; Orban, Philippe ULg et al

in Abstract book (2016, January 26)

Simultaneous solute and heat tracer test provides essential information for a reliable assessment of low temperature geothermal systems. The actual efficiency of ‘open systems’, including heat storage ... [more ▼]

Simultaneous solute and heat tracer test provides essential information for a reliable assessment of low temperature geothermal systems. The actual efficiency of ‘open systems’, including heat storage projects, is strongly affected by the heterogeneity of the hydraulic conductivity field (K-field). It could be also useful for assessing the cumulative impacts of numerous projects in urban areas on the groundwater resources. Using field data from a solute and heat tracer test conducted in the alluvial aquifer of the Meuse River (Belgium), an inverse problem of parameter estimation is solved. The tracing experiment consisted in simultaneously injecting heated water and a dye tracer in a piezometer and monitoring the evolution of groundwater temperature and tracer concentration in the recovery well and in monitoring wells. To get insights in the 3D characteristics of the heat plume, an arrangement of three transects of observation wells was used. The breakthrough curves measured in the recovery well showed that heat transfer in the alluvial aquifer is slower and more dispersive than solute transport. Recovery is very low for heat while in the same time it is measured as relatively high for the solute tracer. This is due to the fact that heat transport is a thermal diffusion dominated process. For conditions corresponding to high Peclet numbers, the hydraulic conductivity is the primary calibration parameter for predicting heat plume distribution. Heat diffusion is larger than molecular diffusion, implying that exchange between groundwater and the porous medium matrix is far more significant for heat than for solute tracers. [less ▲]

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See detailHydrogeological conditions required for Underground Pumping Storage Hydroelectricity (UPSH) in old mines
Bodeux, Sarah ULg; Pujades, Estanislao ULg; Orban, Philippe ULg et al

in Abstract book (2016, January 26)

Renewable energy sources, because of their intermittence, could not afford a stable production and an adequate variability according to the energy demand. Underground Pumped Storage Hydroelectricity (UPSH ... [more ▼]

Renewable energy sources, because of their intermittence, could not afford a stable production and an adequate variability according to the energy demand. Underground Pumped Storage Hydroelectricity (UPSH) using abandoned mine works is an interesting alternative, in flat regions, to store energy during low demand periods by pumping water from an underground mine to an upper reservoir. From the hydrogeological point of view, two considerations can arise for studying the feasibility before constructing an UPSH plant: 1) the alteration of the natural conditions of surrounding aquifers, and (2) the efficiency of the plant depending on possible leakage in the cavities from the hydrogeological environment. A potential old slate mine was selected through a multi-criterion method and its geometrical and hydrogeological characteristics are used to build a simple but typical model. With the help of the HFEMC approach implemented in the code SUFT3D (HEG-ULg), the groundwater flows are modelled for a representative cavity. Simulations of groundwater flow induced by a UPSH system are performed and the main variables are identified. Piezometric heads around the reservoir oscillate, the magnitude of the oscillations and the time to achieve a pseudo-steady state (magnitude and head reached during oscillations not varying anymore with time) depend on the boundaries, the parameters of the aquifer and the characteristics of the underground reservoir. The required hydrogeological conditions are deduced and a screening methodology can be proposed to assess the main impacts caused in aquifers by UPSH plants. Their efficiency regarding the water level evolution inside the reservoir is also considered accommodating the cyclic pumped storage schemes. [less ▲]

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