HAL-BRGM, les publications scientifiques en libre accès du BRGM
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A regionally based method to identify lithology-specific hydraulic conductivity distributions in shallow aquifers using catchment-scale effective values
No full textInternational audienceWe present a novel method for estimating lithology-specific hydraulic conductivities from catchment-scale effective values, each interpreted as a linear combination of the conductivities of the underlying lithologies. The method particularly applies to discharge-derived estimates of effective conductivity, where river networks integrate the influence of predominantly shallow groundwater flows from adjacent hillslopes. Lithological area fractions are used as weights to formulate an overdetermined linear system, which is solved using a modified method of moments under the assumption of lognormally distributed conductivities to account for spatial variability.The method was validated on synthetic cases and applied to 113 catchments in the Armorican Massif (France). It shows good convergence properties and achieves high predictive accuracy: in 85% of cases, the modeled conductivities fall within a 90% confidence interval of the observed values. Convergence analysis indicates that using five catchments per lithology is sufficient to reach 75% predictive success, with mean and standard deviation parameters estimated within 6% and 30%, respectively. With 80 catchments, prediction accuracy increases to 80%, and parameter estimation errors are reduced to 3% and 15%.The method is computationally efficient and generalizable, offering a powerful tool to explore lithology-specific conductivity datasets at regional scales. It may also be adapted to other variables, such as porosity, where linear averaging applies, enabling broader applications in hydrogeological modeling
Elimination du manganèse par une lagune construite pour le traitement passif d'une eau de mine : Facteurs environnementaux et communautés microbiennes
No full textInternational audienceManganese (Mn) removal in passive mine water treatment remains a challenge due to its slow oxidation kinetics,requiring specific biogeochemical conditions. Constructed wetlands are often the key functional units enablingMn removal in full-scale passive treatment plants. This study examines the key biogeochemical factors influencing Mn removal in a full-scale passive mine water treatment plant located in Al`es (South-East France). Overone year, monitoring of physicochemical parameters, microbial communities, and Mn speciation in solid phaseswas conducted every two months. Results highlight temporal variations in Mn removal efficiency, with two mainmechanisms identified: (1) Mn carbonate (MnCO₃) precipitation, likely influenced by high carbonate concentrations in mine water, and (2) Mn oxide (δ-MnO₂) formation, mainly associated with reed rhizosphere, where itaccumulates as mineral plaque. In mine water, Mn removal correlates with Fe particle concentrations, suggestinga catalytic effect, as well as with alkalinity and the abundance of microorganisms affiliated to Alteromonadaceae,suggesting a microbial influence. Mn removal appears to be primarily abiotic, driven by favourable pH andalkaline conditions that promote Mn carbonate precipitation, by autocatalytic oxidation reactions occurring onrhizosphere surfaces and by plant’s design including surface area and hydrological conditions. Microbial communities may facilitate certain Mn removal processes depending on environmental conditions.L'élimination du manganèse (Mn) dans le traitement passif des eaux de mine reste un défi en raison de sa cinétique d'oxydation lente, nécessitant des conditions biogéochimiques spécifiques pour atteindre une élimination efficace. Cette étude examine les principaux facteurs biogéochimiques influençant l'élimination du Mn dans une station de traitement passif des eaux de mine à grande échelle située à Alès (Sud-Est de la France). Pendant un an, le suivi des paramètres physico-chimiques, des communautés microbiennes et de la spéciation du Mn dans les phases solides a été effectué tous les deux mois. Les résultats mettent en évidence des variations saisonnières de l'efficacité d'élimination du Mn, avec l'identification de deux principaux mécanismes : (1) la précipitation du carbonate de Mn (MnCO3), probablement influencée par la forte concentration en carbonates dans les eaux de mine, et (2) la formation d'oxyde de Mn (δ-MnO2), principalement associée au rhizosphère des roseaux, où il s'accumule sous forme de plaque minérale. Dans les eaux de mine, l'élimination du Mn est corrélée avec les concentrations de particules de Fe, suggérant un effet catalytique, ainsi qu'avec l'alcalinité et l'abondance de micro-organismes affiliés à Alteromonadaceae, ce qui suggère une influence microbienne. L'élimination du Mn semble être principalement abiotique, entraînée par un pH favorable et des conditions alcalines qui favorisent la précipitation du carbonate de Mn ainsi que par des réactions d'oxydation autocatalytiques se produisant à la surface de la rhizosphère. Cependant, les communautés microbiennes peuvent faciliter certains processus d'élimination du Mn selon les conditions environnementales. La dynamique saisonnière des communautés microbiennes en réponse aux changements environnementaux peut influencer les mécanismes d'élimination du Mn
Prédictions de chroniques piézométriques de l'aquifère de la nappe de Beauce (Région Centre, France) par un modèle de réseau de neurones influencé par la physique (PINNs)
No full textInternational audienceFIG. 4 -MAE (couleur) de chaque modèle (axe y) pour chaque piézomètre (axe x). 4 Résultats et conclusion Comparaison du modèle physique et des modèles centrés sur les données. Dans cet article, nous choisissons de comparer notre modèle PIRNN à Gardénia, NHITS -un modèle de référence en machine learning -et un RNN classique. La figure 4 indique la Mean Average Error (MAE) du niveau d'eau en mètres pour chaque modèle et chaque série temporelle piézométrique. Parmi les douze piézomètres, Gardénia possède la meilleurs MAE sur quatre d'entre eux, NHITS sur trois d'entre eux et PIRNN sur cinq d'entre eux. Cependant, NHITS présente les meilleurs résultats en moyenne. Les puits 02923X0007_F, 02936X2005_PFAEP et 03983X0267_PZ3 semblent être les plus difficiles à modéliser pour Gardénia, alors que PIRNN arrive à réduire l'erreur absolue moyenne en dessous du mètre pour deux d'entre eux. Conclusion.Bien que Gardénia reste pertinent en thermes de performance et au vu de sa capacité à proposer différents scénarios, il est intéressant de noter que PIRNN -un modèle hybride apprenant la dynamique des données et un modèle physique -arrive à surpasser Gardénia sur les piézomètres les plus difficiles à modéliser.</div
Ground-WAG-Er: A serious game for co-designing groundwater management instruments in Tunisia
No full textSource Agritrop Cirad (https://agritrop.cirad.fr/616694/) * Autres projets (id;sigle;titre): ;ClimBeR Initiative;(FRA) Building Systemic Resilience against Climate Variability and Extremes//International audienceExisting groundwater management instruments often fail to address groundwater degradation and overexploitation. In this article, we present a role-playing game, Ground-WAG-Er, developed to support local stakeholders in co-designing alternative management instruments for the sustainable management of groundwater resources on their territory. The game was played six times in Tunisia involving a total of 31 participants. We analyse three aspects: (1) the combinations of management instruments selected by the players, (2) the minimum conditions participants consider necessary for these instruments to be acceptable, and (3) players' behavioural intentions regarding the adoption of these instruments in reality. Our results reveal the game's limitations in achieving transformative impact on its own, and emphasize the need to integrate it into a broader participatory process. We provide several concrete avenues to enhance the game's impact
Low input remediation techniques for contaminated site management
No full textInternational audienceRisk-based land management emphasises remediation to manage risks from land contamination, aiming to reduce human and environmental risks while enabling site reuse and redevelopment. Since the mid-2000s, sustainable remediation has gained prominence, driven by global sustainability agendas such as the United Nations 2030 Agenda and the European Green Deal. These frameworks encourage integrated approaches that maximise remediation benefits and minimise negative impacts. Low-input remediation techniques (LIRT) represent a family of approaches characterised by lower energy and resource demands, often leveraging natural processes, renewable resources, or energy sources. Examples include methods using biochar, photosynthesis, or renewable energy systems. LIRT overlap with concepts like gentle remediation options (GRO) and nature-based solutions (NBS), which employ natural processes to address contamination while delivering environmental and societal benefits. While LIRT are typically effective for pathway management rather than source control, they offer sustainable outcomes such as stabilisation, containment, and destruction of biodegradable contaminants. They also contribute to broader sustainability goals, such as reducing carbon footprints and preserving soil functionality, and can support site reuse for biofeedstocks, habitats, or amenity spaces. LIRT are particularly valuable for stalled or economically unviable sites, offering cost-effective and flexible solutions. However, achieving sustainable outcomes depends on site-specific factors, and LIRT often work best when integrated into a broader remedial strategy combining intensive and low-input methods. This paper explores LIRT's potential applications, technical characteristics, and challenges, alongside their benefits for sustainable land management and the restoration of underutilised sites. Environmental signicanceRisk management that is also sustainable is global best practice for contaminated site remediation. While sustainability is always site-specic, some methods tend towards sustainability. Nature Based Solutions (NBS) and "Gentle Remediation Options" (GRO) encompass many of these. However, these categories overlook other promising approaches, such as in situ stabilisation. The paper proposes a broader umbrella term: Low Input Remediation Techniques (LIRT), i.e. methods that use fewer resources and less energy, may use or produce renewables, and can deliver added benets beyond risk reduction (e.g., biodiversity gains and social value). This review provides a framework for dening LIRT, surveys existing techniques, and outlines their wider value, aiming to broaden attention beyond biobased options and encourage wider uptake in practice.</div
French working group "geotechnics and climate change" -Carbon footprint of geotechnical structures: assessment and integration into design
No full textInternational audienceIPCC reports have demonstrated that greenhouse gas (GHG) emissions and climate change are strongly correlated. The infrastructure construction sector (public works activities only) accounts for about 3,5% of France's total carbon emissions. Considering that the total impact of this field is even greater when including the building sector and other related activities, geotechnics can and must play a significant role in reducing these emissions. Despite the multiple environmental impacts, the urgency of climate change necessitates a focus on GHG emissions, which can be identified and mitigated throughout project execution by prioritizing sustainable and durable technical choices. Ideally, carbon footprint and other environmental impact assessments should cover the entire lifecycle of structures, from site investigation to exploitation, including maintenance and end-of-life site restoration. Awareness of these issues and a thorough understanding of its consequences will enable the geotechnical domain to propose effective solutions. Within this framework, the French Committee of Soil Mechanics and Geotechnics (CFMS) and the French Committee of Engineering Geology (CFGI) are working on the establishment of recommendations to provide tools for evaluating, controlling, and reducing emissions related to geotechnical works considering the French context. This work seeks to provide geotechnical professionals with quantitative methods for assessing the carbon footprint of geotechnical structures, as well as essential tools and databases. It also provides best practices for reducing this footprint and qualitative assessments of other environmental impacts within a sustainable development framework. Therefore, it underscores the importance of incorporating environmental impact assessments in geotechnical engineering to mitigate climate change effects and promote sustainable development
Unsupervised Spatially Aware Gaussian Mixture Model via Implicit Deep Priors
No full textInternational audienceGaussian Mixture Modeling (GMM) is a well-established probabilistic clustering method. However, traditional GMMs ignore spatial relationships between data points, which limits their performance on structured data. Several extensions have been proposed to incorporate spatial context, but they typically rely on strong predefined spatial priors via kernels with fixed neighborhood sizes. These assumptions restrict the model's ability to adapt to varying spatial structures in real data. In this paper, we introduce an unsupervised spatially-aware GMM framework that leverages the Deep Image Prior (DIP) to impose spatial consistency without external supervision. Our method learns an implicit one through DIP-based denoising of GMM posterior probability maps, effectively capturing spatial dependencies directly from the data. To further improve robustness, we propose a strategy that accounts for the variability of DIP reconstructions by averaging multiple realizations, leading to more stable and coherent clustering results. We evaluate our method against spatial GMM variants, including isotropic and anisotropic formulations, as well as deep learning based alternatives. Experimental results demonstrate that our approach achieves superior performance while maintaining the unsupervised nature of the standard GMM. Moreover, our framework does not require any predefined spatial prior.</div
Comparison of high resolution XRF and downhole geophysical scanning of Nussloch loess records, Germany, with field observations
No full textInternational audienceNussloch (Germany) is a distinctive site of interest, particularly as a reference sequence for Late Pleistocene European loess, because it provides a comprehensive record of millennial climate variability. A notable feature of this site is its location within an active quarry. Consequently, the stratigraphic profiles documented constitute an ephemeral record, susceptible to rapid disappearance or brief accessibility, contingent on the operational status of the quarry. In order to guarantee the maintenance of a complete record of the sequence, three separate cores were collected and labelled S1, S2, and S3. The results of core S2, which is the most complete and thoroughly examined, are presented here. A comparison is drawn with the most recent P8 profile that is currently available. XRF measurements, conducted after the cores had been opened and described, are also presented. Borehole logging was carried out in the field after core retrieval, and the resulting measurements are also presented. The findings of this study demonstrate that a high degree of correlation can be established between the records from outcrop investigations and core studies, demonstrating the importance of preserving such archives for future research
A situated proposal for a grounded approach to socio-hydrology
No full textSource Agritrop Cirad (https://agritrop.cirad.fr/616193/)International audienceSocio-hydrology, a range of attempts to better account for 'the social' in hydrological processes, has made significant progress during the Panta Rhei scientific decade of the International Association of Hydrological Sciences. Yet, where socio-hydrological studies continue prioritizing hydrological dynamics in explanations and solutions, critical social science studies continue to remain reluctant to engage in helping solve water problems, especially when this involves quantification. This Special Issue gathers contributions that share the ambition to enhance methodological symmetry between hydrological and social science forms of knowledge-making. Realizing this ambition hinges on (1) revisiting hydrology's epistemological preference for detachment, distance and replicability, replacing it with more modest forms of situated engagement that explicitly (re-)connect socio-hydrological knowledge-making to (always specific and political) places, waters, experiences, people, concerns and actions, and (2) inviting critical social science to leave the comfort of moral high grounds to become engaged in the design and development of practical solutions. This grounding of socio-hydrology takes the form of situated engagement and makes resulting knowledge both more accurate and more actionable, better linking proposed solutions to the transformations towards sustainability and justice that are so urgently needed
A window on the amalgamation of Western Gondwana: Geological history of the Ouaddaï massif (E. Chad)
No full textInternational audienceThe Saharan metacraton was assembled during pre-Neoproterozoic to Neoproterozoic times and was strongly remobilised during the Pan African orogeny. The Ouaddaï massif in eastern Chad represents the core of the Saharan metacraton, yet its geological history remains poorly documented. In this study, we combine of field observations, petrological analysis of metamorphic rocks, and geochemical and geochronological constraints to reconstruct the tectono-metamorphic evolution of the Ouaddaï massif. The study area is dominated by collision-related plutonic rocks and migmatitic gneisses, within which inliers of older basement occur. Geochemical data indicate a transition from active-margin to collisional magmatism, with a compositional evolution from diorite to granite. This suite is cross-cut by syenogranites and alkaline granites with shoshonitic affinities, interpreted as post-collisional granitoids derived from tonalitic rocks to sedimentary protoliths. Geochronological data (U-Pb on zircon and monazite) point to a ca. 1000 Ma age for orthogneisses inliers. Granitoids of the Ouaddaï massif record emplacement ages from 620 to 590 Ma, coeval with high-temperature metamorphism characterized by peak pressure–temperature conditions of 1.2 GPa and 850 °C (mafic granulite) and around 0.8 GPa and 700 °C (sillimanite-garnet bearing migmatites). Integrating our new results with regional data, we discuss the existence and geodynamic evolution of the Saharan Metacraton. Our findings emphasize the significance of the Saharan Metacraton as a key region for understanding the extensive reworking of cratonic lithosphere during both a Tonian magmatic phase prior and the assembly of Gondwan