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See detailStatistical description of hydrogeological parameters for the main aquifer contexts in Wallonia
Briers, Pierre ULiege; Dollé, Fabien ULiege; Orban, Philippe ULiege et al

Conference (2017, January 20)

The Walloon Region Soil decree proposes a series of guidance documents associated to the procedures for site remediation operations. Among others, one of these documents describes methodologies and tools ... [more ▼]

The Walloon Region Soil decree proposes a series of guidance documents associated to the procedures for site remediation operations. Among others, one of these documents describes methodologies and tools for risk assessment of pollutant leaching from soil to groundwater and for pollutant dispersion through groundwater. These tools require using estimates of hydrogeolocial parameters such as hydraulic conductivity, effective (transport) porosity etc. In this context, an inventory of hydrogeological studies (regional characterization studies, groundwater protection zones…) was performed to identify and collect available field-based measurements for a statistical description and analysis of such data. Complementary to that, a simple geodatabase has been developed to manage and process these data. As expected, these results show contrasted parameter distributions per geological contexts and regions. The objective of the presentation is to describe the methodology followed for the statistical treatment of hydrogeological data and to present the results and associated database. It is believed that such results can be very useful for different hydrogeological studies, in particular as a first referential for groundwater modelling applications and any other studies where statistical descriptions of hydrogeological data are relevant. [less ▲]

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See detailConvention Région wallonne et HGE-ULg Caractérisation complémentaire des masses d’eau dont le bon état dépend d’interactions entre les eaux de surface et les eaux souterraines - Délivrable D1.8 Rapport final
Brouyère, Serge ULiege; Briers, Pierre ULiege; Descy, Jean-Pierre et al

Report (2017)

Mechanisms of interactions between groundwater bodies and rivers whose status and anthropogenic use can be detrimental from a quantitative and qualitative point of view to one or the other of these two ... [more ▼]

Mechanisms of interactions between groundwater bodies and rivers whose status and anthropogenic use can be detrimental from a quantitative and qualitative point of view to one or the other of these two compartments of the water cycle. In addition, contamination of groundwater by nitrate remains relevant. Based on these observations, a study financed by the Public Service of Wallonia was carried out over a period of 39 months to investigate (1) the direction, importance and dynamics of water exchange between groundwater and rivers at the scale of a river section; (2) the impact of these interactions on river baseflows and the river ecological status as a function of groundwater withdrawal and recharge at the catchment scale; (3) mechanisms and timing of transfer and abatement of pollutants (nitrate) between groundwater and surface waters at the watershed scale. The consequences of these mechanisms on the medium- and long-term evolution of groundwater and surface water quality were to be determined. To achieve this, the project relied on the implementation of a series of field investigations essentially focused on the interfaces between surface water and groundwater compartments (soil and unsaturated zone and water-table interface), while acquiring additional information on groundwater. The investigations carried out in the watersheds of the upstream Hoyoux and Triffoy watershed in the Condroz region aimed to provide 6 specific responses to water quantity and quality issued associated with groundwater – surface water interactions in the selected basins and generic responses in the form of new knowledge concerning the mechanisms of recharge and groundwater - river exchanges, concerning the evolution of nitrate concentrations in watersheds, data and measurements for the parameterization of models, and water resources management tools in the form of quantitative and qualitative indicators for groundwater - surface water interactions. [less ▲]

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See detailStream-aquifer interactions: a combined field - methodological approach in fractured carbonate catchments
Brouyère, Serge ULiege; Briers, Pierre ULiege; Orban, Philippe ULiege et al

Conference (2016, December 16)

Stream-aquifer studies remain a challenge due to numerous factors impacting these interactions. They play a fundamental role in terms of quantity and quality of water, in particular on the ecological ... [more ▼]

Stream-aquifer studies remain a challenge due to numerous factors impacting these interactions. They play a fundamental role in terms of quantity and quality of water, in particular on the ecological status of rivers. Field quantification of such interactions is a first step but it has to be in relation with the whole budgets of water and transported substances across the catchment in order to represent their importance on overall fluxes. Numerous complementary investigations have to be undertaken to achieve such understanding of catchment behavior, in particular to estimate specific indicators and to achieve representative data for modeling stream-aquifer interactions. From that situation, our study aims to characterize and quantify stream-aquifer interactions to assess reliability of diverse field experiments methodologies. A catchment has been studied for 3 years in quantitative and qualitative ways via a dense instrumentation and monitoring. Numerous complementary investigations (discharge measurements, hydrogeochemistry, distributed temperature sensing, base flow separation…) have been applied to reach the objectives. We achieved a large and diversified measurement dataset of groundwater-surface water interactions and whole water budget. This allowed reaching an improved understanding of the catchment behavior to quantify importance of the groundwater component on the dynamics and chemistry of the stream and on the consequences on river ecological status. The investigations on several subcatchments allows also to propose a general typology of stream catchment in terms of groundwater dependence based on the combination of various groundwater contexts and groundwater-stream interaction indicators. Methodologies applied in this study allow to emphasize strength and weakness of numerous investigations in a stream aquifer project and conclusions can be reproduced and generalized to other contexts. [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 ULiege; Schmit, Flore; Orban, Philippe ULiege 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 detailLe bassin du Triffoy et les eaux souterraines : Exemple de caractérisation des échanges entre nappe et rivière
Briers, Pierre ULiege; Descy, Jean-Pierre; Schmit, Flore et al

in Atlas du Karst Wallon - Bassins versants du Hoyoux et de la Solières (2016)

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See detailVégétation du ruisseau du Triffoy et du Hoyoux près du moulin de Roiseux
Bouxin, Guy; Briers, Pierre ULiege; Michel, Georges

in Atlas du Karst Wallon - Bassins versants du Hoyoux et de la Solières (2016)

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See detailHydrogéologie du bassin du Hoyoux
Briers, Pierre ULiege; Jamin, Pierre ULiege; Ruthy, Ingrid ULiege et al

in Atlas du Karst Wallon - Bassins versants du Hoyoux et de la Solières (2016)

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See detailDélivrable D3.3 Bilans hydrogéologiques
Schmit, Flore; Hallet, Vincent; Briers, Pierre ULiege et al

Report (2016)

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See detailCase study 2: Groundwater – surface water interaction in limestone areas of the GWB BE_Meuse_RWM021 (Belgium)
Brouyère, Serge ULiege; Briers, Pierre ULiege; Schmit, Flore et al

in Hinsby, Klaus; Schutten, Johan; Craig, Matt (Eds.) et al Technical Report on Groundwater Associated Aquatic Ecosystems (2015)

The achievement of good status in groundwater bodies involves meeting a series of conditions, which are defined in the Water Framework Directive (WFD) and, in the case of good chemical status, are given ... [more ▼]

The achievement of good status in groundwater bodies involves meeting a series of conditions, which are defined in the Water Framework Directive (WFD) and, in the case of good chemical status, are given further detail in the Groundwater Directive (GWD). One of these conditions is to ensure that groundwater inputs to associated surface waters do not result in failure to meet the environmental objectives of those waters or result in significant diminution in status/ecological or chemical quality of those waters. GWAAE (Groundwater Associated Aquatic Ecosystems) are those surface water bodies (SWBs), including rivers, standing waters and transitional waters where the surface water ecology and hydrology is dependent on contributions from groundwater in order to meet their environmental objectives under the WFD. These environmental objectives may vary, and therefore the associated environmental quality standards (EQS) or flow/level requirements of GWAAEs may differ between high status and good status SWBs. As noted in the Blueprint for Water, analysis of the first River Basin Management Plans has shown that Member States (MS) have experienced difficulties in understanding the interactions between groundwater and surface water and undertaking the necessary status assessments. This was highlighted in a survey carried out by Working Group Groundwater (WGGW) in 2014/15, which indicated that only half of the MS had assessed quantitative interactions and very few had addressed chemical pressures, including the derivation of threshold values (TVs) that were appropriate to the WFD objectives for GWAAEs. This report aims to further knowledge on what GWAAE are, how they are aligned to WFD processes, and support Member States to properly include the needs of these ecosystems in river basin management planning. The report clarifies the categories of GWAAE and their relative dependence on groundwater and collates current available knowledge and experience via a number of examples and case studies. Terminology and status assessment procedures are explained and pragmatic approaches are proposed which leave some flexibility for MS to adapt to their own specific needs. This technical report, which is not a "guidance document", makes use of and complements existing CIS documents, including existing technical reports on groundwater dependent terrestrial ecosystems (GWDTEs) and Guidance Document 18 (Guidance on Groundwater Status and Trend Assessment). A number of recommendations for technical users of the report are highlighted in boxes in each Chapter. The common themes from these recommendations are collated in Chapter 8, as issues and questions to WGGW and MS in general. The key message from this is the need for closer interaction between scientific disciplines, practitioners and Working Groups in developing conceptual understanding for GWAAEs and implementation of WFD requirements, including identification of GWAAEs, their characterisation and monitoring, and adopting appropriate status assessment methodologies. [less ▲]

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