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Garonne River Behavior Under Climate Change and the Potential Adaptation Strategies
No full textInternational audienceAccording to the IPCC reports, the effects of climate change are well present from several decades ago, and it is expected to become even more pronounced during the remainder of the twenty-first century. The river basin system is defined as a complex of interaction between aquatic and terrestrial ecosystems. The interface between these ecosystems results in different responses of the river regime ranging from floods to low flow. The instability of alluvial valley due to geomorphological and fluvial dynamics, represents an additional challenge for the riparian societies face to climate changes. The Garonne River, the third largest French Atlantic River in terms of discharge, flows down in the Garonne Valley, the largest occupied and cultivated alluvial plain in France. This area is influenced by a wide range of Oceanic, Mediterranean, and mountainous climates. Hence, the complex Garonne River regime is influenced by the precipitation generated over the Massif Central and the French and Spanish Pyrenees Mountains. The surrounding alluvial aquifer, which forms an important part of this system, maintains a strong hydraulic connection with the river and sustains its low flow. Consequently, this aquifer is extremely sensitive to meteorological changes and hence to recharge system variation. The inhabitants in this area are strongly depending to the river and its alluvial aquifer. However, the impact of climate changes on socio-economic activities could be significant in this area. The adaptation to these changes creates additional challenges for decision-makers and becomes a major objective of the watershed policy. The trends assessment of the Garonne River's discharge over the last fifty years has shown a decrease in average annual discharges and substantial decrease in low flows. The dry periods are starting earlier and becoming more severe and longer. Upstream, the snow cover shows a decrease in thickness and duration, which has a negative impact on the river’s discharge and consequently on the groundwater recharge ratio. Groundwater measurements show a general decrease in water level. The observations show that most of the wells located close to the river have dried up during the dry periods since the alluvial aquifer drains into the river during these periods. The groundwater level reduction could have a negative impact on agriculture, wetlands, and river ecosystems. Thus, the implementation of adaptation measures has been initiated. The artificial recharge of the alluvial aquifer is considered as an adaptation strategy to address the effect of climate change and sustains the low flow of the river. In addition, this strategy will help to buffer the river temperature during the low flow periods. Several pilot sites in the Garonne Valley are under investigation for testing the artificial recharges. The first site, where artificial recharge has been tested since 2019, is located near the city of Agen, where the runoff is collected in a retention basin and is used to recharge the alluvial aquifer. Groundwater level in the wells near the retention basin have increased by about 1 m following rainfall events. The results of the groundwater modeling show (1) a similar magnitude aquifer response to the induced infiltration and (2) that the infiltrated water would take about 4 months to reach the Garonne River, which is an appropriate time to maintain the river's low flow, since recharge takes place in spring. Another site that has been tested is located near the city of Marmande, where the surface water from the Lateral Canal of the Garonne River has been used as a source to recharge the alluvial aquifer in May 2023. The infiltrated water has created a piezometric dome and the groundwater level has increased by 15 and 33 cm into two boreholes located about 40 m upstream and downstream of the infiltration site respectively. This experiment will be carried out on a larger scale, and further groundwater measurements and modeling will be carried out for this and other selected sites in the near futur
OGC Water Quality Interoperability Experiment Engineering
No full textThis document reports on an exercise involving several government organizations, private companies, and academics, trying to harmonize water quality data exchange. Water quality encompasses several notions that needed to be clarified and prioritized so that clear work could be undertaken. Building on the identified use cases, a clarification of the information elements (concepts) that are necessary for water quality data exchange was carried out. All that work builds on the OGC Baseline for its semantic part, leveraging “Observations, Measurements and Samples” (OGC 20-082r4), “OGC® WaterML 2: Part 3 – Surface Hydrology Features (HY_Features) – Conceptual Model 1.0” (OGC 14-111r6), and “OGC WaterML 2: Part 4 – GroundWaterML 2 (GWML2) 2.2” (OGC 16-032r2). As those standards already covered the need, most of the effort was to illustrate and document how to use the standards in combination to achieve the target goals.The next step involved technical assessment of the OGC Baseline so that the most relevant OGC APIs are identified for implementation. “OGC SensorThings API Part 1: Sensing Version 1.1” (OGC 18-088) was the obvious choice as the core focus was on observation exchange. Its model was enhanced including evolutions brought by the “Observations, Measurements, and Samples” revision to meet the conceptual exercise requirements (thus paving the way for the V2 of SensorThings API Part 1).All the necessary framework was then available for the Interoperability Experiment members to implement the approach on top of their respective systems opening allowing for various testing environments across countries, organizations, and tools. This testing validated the proposed solutions in concrete environments. Future work was identified to settle the approach for the community to build on. This work includes some standing issues but mainly targets evolution in relevant identified standards as described in section 1.4 “Future work”.This report includes several illustrations from the modelling exercise that are available from the online OGC Enterprise Architect tool (https://umltool.ogc.org/ ), as well as from the data exchange testing. It also contains references to content that is publicly available on the Water Quality IE (WQ IE) GitHub repository (https://github.com/opengeospatial/WaterQualityIE
Reconciling critical and engaged approaches environmental justice at the heart of floodplain management
No full textPhnom Penh lies at the junction of four rivers and marks the beginning of the Mekong delta. The Cambodian delta plains are characterised by earthen canals that result from both hydrological processes and human interventions dating backto the mid-nineteenth century. These preks shape the landscape and serve a variety of purposes: communication routes, irrigation for agriculture, fishing areas, etc. For about two decades now, the Cambodian government together with its technical and finan-cial partners has viewed preks as a means of intensifying regional agricultural systems. Ambitious programmes aimed at greater control of water flows have been implemented and are characterised by a low level of attention to environmental justice issues
Trouvez les sept différences. Une approche multidisciplinaire pour la reconstruction du procédé de multiplication dans la sculpture de la fin du Moyen Âge
No full textInternational audienceVormoderne Artefakte, die einen großen Ähnlichkeitsgrad vorweisen, sind nicht aus schließlich als Folge der mechanischen Verfahren wie Druck oder Abformung entstanden. Auch unter den geschnitzten Bildwerken finden sich Exemplare, die beinahe identisch er scheinen: Sie haben die Abmessungen, Konstruktion, Komposition und oft auch die Ober flächengestaltung gemeinsam. - - - Eine solche auffallende Ähnlichkeit weisen relativ oft Alabasterbildwerke auf, die in verschiedenen Epochen an mehreren Produktionszentren als Ergebnis serieller Produktion hergestellt worden waren. Dies lässt sich sowohl für die englischen Alabasterreliefs und -figuren des 14.–15. Jahrhunderts, Reliefs der südniederländischen Werkstätten des 16.– 17. Jahrhunderts als auch für die Marienfiguren der sizilianischen Trapani-Ateliers des 17.–18. Jahrhunderts feststellen.1 Vieles spricht also dafür, dass es die relative Leichtigkeit der Alabasterbearbeitung ist,2 gefördert durch die Weichheit und (bei qualitätvollen Blö cken) die Homogenität des Materials, die den Einsatz von Alabaster in seriellen und repro duktiven Kunstproduktionsverfahren begünstigt hat. Darüber hinaus ist für einige dieser Produktionszentren Arbeitsteilung belegt, die eine Standardisierung (z.B. der Maße) ebenso forderte wie förderte.3 Konkrete Schritte und Werkzeuge des bildhauerischen Ver fahrens, das zur Entstehung beinahe identischer Skulpturen geführt hat, sind jedoch bis her nicht bekannt.4 Weil die Kunstgeschichte allein diese Wissenslücke nicht schließen konnte, unternahm das interdisziplinäre Forschungsteam des Projektes Materi-A-Net,5 zusammengesetzt aus Vertreter:innen der Kunstgeschichte, Geochemie, Bildhauerei und Restaurierung, gemeinsame Untersuchungen, um sich mit einem multidisziplinären An satz einer Antwort zu näher
Analyse des séries temporelles Sentinel-2 pour l'estimation des cycles de maraîchage en saison sèche
No full textSource Agritrop Cirad (https://agritrop.cirad.fr/615863/)International audienceEn Afrique, l'agriculture, pilier économique, est de plus en plus exposée aux baisses et à l'irrégularité des précipitations, ainsi qu'au raccourcissement des saisons pluvieuses. Dans ce contexte, les cultures irriguées de contre-saison, majoritairement maraîchères, revêtent une importance stratégique pour la sécurité alimentaire. Localisé surtout en zones périurbaines, le maraîchage connaît une expansion rapide grâce à une forte demande et à une rentabilité élevée. Cependant, son essor reste limité par la disponibilité en eau, ressource critique en saison sèche. C'est dans ce cadre qu'intervient le projet IRRINN, porté par le Cirad au Burkina Faso. Il vise la co-conception de solutions locales et durables pour la petite irrigation en réunissant producteurs, techniciens, fournisseurs de matériel, financiers et chercheurs au sein de plateformes d'innovation. Le projet s'intéresse particulièrement aux effets de la multiplication des puits individuels et à l'usage croissant des pompes solaires sur l'extension spatiale du maraîchage et sur le nombre de cycles réalisés entre décembre et mai dans la périphérie de Ouagadougou L'analyse de ces dynamiques spatio-temporelles requiert des outils capables de détecter les surfaces cultivées et de quantifier les cycles de culture. L'imagerie satellitaire constitue ici une ressource privilégiée, permettant un suivi régulier des pratiques agricoles. L'étude propose ainsi une méthodologie pour estimer le nombre de cycles de maraîchage durant la saison sèche, à partir d'images Sentinel-2 (revisite de 5 jours, résolution de 10 m) sur 3 années consécutives, desquelles sont extraites analysées des séries temporelles d'indice de végétation (NDVI). Trois algorithmes adaptés aux séries temporelles ont été comparés : KNeighborsTimeSeriesClassifier (basé sur la distance Dynamic Time Warping), MiniRocketClassifier (convolution rapide) et TimeSeriesForestClassifier (forêts aléatoires). Les résultats montrent que la classification des cultures maraîchères est fiable (f-score = 0,81). En revanche, l'identification du nombre de cycles demeure plus délicate : les performances sont correctes pour un cycle (f-score = 0,78), mais limitées pour deux cycles (f-score = 0,60). Des perspectives d'amélioration sont envisagées, notamment via l'intégration de données radar (SAR), insensibles à la couverture nuageuse
Assessing soil health at former thermal power plant sites
No full textInternational audienceSoils inherited from heavy industrial activities are often perceived as highly degraded.However, their health status is more diverse than commonly assumed, and appropriatemethods for evaluating the health of industrial soils remain largely underexplored.Former thermal power plants, in particular, present a wide variety of soil types due to thediversity of activities they once hosted, including: (i) areas with reinforced foundationsfor boilers (plant foundations); (ii) oil storage zones (oil deposits); (iii) coal storage areason concrete slabs (coal deposits); and (iv) ash disposal sites for bottom ash and fly ash(bottom-ash and ash deposits).This study aims to characterize the diversity of soil health states at former thermalpower stations by assessing their physical, chemical, and biological properties. Twodecommissioned thermal power plants with similar geological contexts were selected.Within each site, zones corresponding to different former industrial uses were identified.In total, twelve 100 m² plots of vegetation and soil, considered internally homogeneousbut distinct from one another, were selected. Across these plots, twelve soil profiles and68 soil samples (from surface layers and horizons) were collected and analysed for awide range of physical, chemical and biological parameters, including plant communities,nematodes, and microbial populations.Evaluation of the twelve profiles revealed that each soil exhibited unique characteristics.Even areas with similar historical uses displayed differences in the number of soilhorizons, rooting depth, and organic carbon stocks—some soils even holding nearlytwice the carbon stock compared to their control counterparts. Our results highlightthat soil degradation cannot be inferred solely from the type of past industrial activity.A functional, multi-parametric analysis is essential to accurately assess the potentialof these soils for future uses. Furthermore, the integration of biological indicatorsalongside physico-chemical properties proved crucial, especially for evaluating dynamicfunctions such as soil fertility and greenhouse gas storage and sequestration. Ultimately,considering entire soil profiles rather than focusing solely on the surface layer revealsthat the inherited vertical heterogeneity of highly anthropized soils has a major impacton their health status
Recherches pluridisciplinaires sur des îles de la basse vallée de la Seine. Les prospections autour de l'île aux Bœufs et de l'île Sainte-Catherine: Oissel-sur-Seine - Tourville-la-Rivière (Seine-Maritime)
No full textInternational audiencePluridisciplinary projet Oscellus, started in 2022, aims to specify the occupation and exploitation of the islands of Oissel, in the Seine river, in Normandy, through time, including a viking camp occupied between 857 and 861. The morphology of these islands has changed many times, documented at least since the 18th c., changes of natural or human origin. Their archaeological and historical potential is difficult to apprehend, but geophysical and geomorphological analysis bring new interpretations.Le projet de recherche pluridisciplinaire Oscellus, né en 2022, vise à caractériser l’occupation des îles du secteur de Oissel, en basse vallée de la Seine, dont la présence d’un camp d’hivernage viking (857-861). D’origines naturelles ou anthropiques, de nombreuses modifications ont été observées depuis le milieu du XVIIIe siècle. De fait, le potentiel archéologique et historique des îles aux Bœufs et Sainte-Catherine est complexe à aborder. Les analyses géophysiques et géomorphologiques apportent toutefois des précisions
Studying Diffusiophoresis-Driven Colloid Transport in Porous Media Using Microfluidics
No full textNational audienc
Signature hydrothermale post-collisionnelle à 340 Ma dans le Massif central oriental : exemple des indices minéralisés du Mont Beuvray
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Assessing atoll island future habitability in the context of climate change using Bayesian networks
No full textInternational audienceAtoll islands are threatened by multiple climate change impacts, such as sea-level rise, extreme sea-level events, ocean warming, and acidification. A recent approach to assessing climate change risk to these islands is to use multi-criteria expert judgment methods. These approaches can serve as a basis for the development of Bayesian Networks (BNs) integrating expert knowledge and uncertainties to perform climate risk assessments. Here, we use the multi-criteria expert-based assessment of Duvat et al. (2021), who assessed future risk to habitability for four Indian and Pacific Oceans' atoll islands, in order to discuss the advantages and limitations of the BN model. Advantages of the approach include the explicit treatment of uncertainties and the possibility to query expert knowledge in a non-trivial manner. For example, expert knowledge can be used to assess risks to habitability and future uncertainties and to explore inverse problems such as which drivers can exceed specific risk thresholds. Our work suggests that BN, though requiring a certain level of implementation expertise, could be used to assess climate change risk and support climate adaptation