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[hal-03673906] Evaluation des incertitudes et de l’homogénéité de longues séries de débits de crue sur le Rhin à Bâle (1225–2017) et Maxau (1815–2018)
Un diagnostic sur la sécurité aux inondations des digues du Rhin en aval de Strasbourg a été réalisé par INRAE de 2018 à 2020, pour le compte de la DREAL GrandEst , avec des échanges au sein de la Commission Permanente internationale pour l'aménagement du Rhin supérieur. Un travail spécifique d'analyse des incertitudes est présenté à l'aide du modèle BaRatin sur la reconstitution des débits de crue des séries de Bâle (1225-2017) et Maxau (1815-2018). La largeur de l'intervalle d'incertitude à 95% varie à Bâle de ± 7% sur la période récente (1994-2017) à ± 48% sur la période la plus ancienne (1225-1713), et à Maxau de ± 5% sur la période récente (1977-2018) à ± 45% sur la période la plus ancienne (1815-1839). L'application de tests statistiques fait apparaître des hétérogénéités pour les deux séries de crues, qui proviennent pour partie des aménagements hydrauliques sur le Rhin au cours des deux derniers siècles. Les séries corrigées de ces effets sont de meilleure qualité, avec toutefois une rupture vers 1966-1976 à Bâle et Maxau, qui pourrait provenir d'un changement constaté en Europe centrale en termes de régime de circulation climatique depuis les années 1970.
ano.nymous@ccsd.cnrs.fr.invalid (Michel Lang) 20 May 2022
https://hal.science/hal-03673906v1
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[hal-02605328] Performance weighting of global climate models
[...]
ano.nymous@ccsd.cnrs.fr.invalid (Benjamin Renard) 16 May 2020
https://hal.inrae.fr/hal-02605328v1
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[hal-00453882] An application of Bayesian analysis and Markov chain Monte Carlo methods to the estimation of a regional trend in annual maxima
L'analyse bayésienne est de plus en plus utilisée en hydrologie, car elle offre un cadre méthodologique permettant d'intégrer des connaissances physiques et statistiques dans des modèles complexes. Cet article en présente une application dédiée à l'analyse régionale fréquentielle de valeurs extrêmes, dans un contexte non stationnaire. Les méthodes MCMC sont utilisées pour résoudre numériquement un problème multidimensionnel sur un ensemble de séries hydrométriques. L'article montre l'intérêt d'une analyse régionale vis à vis d'une estimation locale site par site. Le cadre bayésien d'analyse permet d'intégrer les incertitudes de modélisation, ce qui est particulièrement utile lorsque le diagnostic sur la stationnarité des séries ne peut être totalement accepté ou rejeté. / Bayesian analysis is becoming increasingly popular in a number of fields, including hydrology. It appears to be a convenient framework for deriving complex models in agreement with both physical reality and statistical requirements. The aim of this paper is to present an application to the regional frequency analysis of extremes in a nonstationary context. A nonstationary regional model is thus proposed, together with the related hypotheses. The Bayesian inference of this model is then described. Markov chain Monte Carlo (MCMC) methods are needed for this purpose because of the dimensionality of the model and are described in this paper. The usefulness of such a model is then illustrated on a hydrological case study concerning annual maximum discharges of several sites. The advantage of regional analysis compared to at-site estimation is thus highlighted. Moreover, the Bayesian framework allows for a direct and comprehensive inference based on the posterior distribution and is able to take into account modelling uncertainties, which is particularly useful when the stationarity of a series can neither be ensured nor be totally rejected.
ano.nymous@ccsd.cnrs.fr.invalid (Benjamin Renard) 05 Feb 2010
https://hal.science/hal-00453882v1
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[hal-02603422] A GCM weighting procedure based on explicit probabilistic models and accounting for observation uncertainty
In recent years, the climate modeling community has put a lot of effort into releasing the outputs of multimodel experiments for use by the wider scientific community. In such experiments, several structurally distinct GCMs are run using the same observed forcings (for the historical period) or the same projected forcings (for the future period). In addition, several members are produced for a single given model structure, by running each GCM with slightly different initial conditions. This multiplicity of GCM outputs offers many opportunities in terms of uncertainty quantification or GCM comparisons. In this presentation, we propose a new procedure to weight GCMs according to their ability to reproduce the observed climate. Such weights can be used to combine the outputs of several models in a way that rewards good-performing models and discards poorly-performing ones. The proposed procedure has the following main properties: 1. It is based on explicit probabilistic models describing the time series produced by the GCMs and the corresponding historical observations; 2. It can use several members whenever available; 3. It accounts for the uncertainty in observations; 4. It assigns a weight to each GCM (all weights summing up to one); 5. It can also assign a weight to the 'H0 hypothesis' that all GCMs in the multimodel ensemble are wrong. The application of the weighting procedure is illustrated with several case studies including synthetic experiments, simple cases where the target GCM output is a simple univariate variable and more realistic cases where the target GCM output is a multivariate and/or a spatial variable. These case studies illustrate the generality of the procedure which can be applied in a wide range of situations, as long as the analyst is prepared to make an explicit probabilistic assumption on the target variable. Moreover, these case studies highlight several interesting properties of the weighting procedure. In particular, they suggest that observation uncertainty plays a key role in the assignment of performance weights to competing GCMs. Roughly speaking, the weights move from 'weight =1 for a single model' to 'same weight for all models' with increasing observation uncertainty. This behavior is consistent with intuition (highly uncertain observations make it more difficult to distinguish good- and poorly-performing GCMs), and emphasizes the importance of reliably quantifying the uncertainty in the observed historical climate. This work has been carried out within the EU FP7 COMPLEX project (Knowledge Based Climate Mitigation Systems for a Low Carbon Economy, http://owsgip.itc.utwente.nl/projects/complex/)
ano.nymous@ccsd.cnrs.fr.invalid (Benjamin Renard) 16 May 2020
https://hal.inrae.fr/hal-02603422v1
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[hal-02590813] Monitoring Mediterranean flash-floods using an image-based method : a case study on the Ardèche watershed, France
Conventional stream gauging techniques are not adapted to flashflood measurement because: They are intrusive : high flow velocities and floating debris endanger the operators and the equipment. They are time consuming: the river level and discharge can significantly change during the measurement. They are expensive and labor intensive : they can not be included in a densely distributed hydrometry strategy We present a nonintrusive, imagebased method for monitoring rivers continuously and in realtime. The capability of LSPIV for measuring discharge during a flashflood on the Ardèche River is demonstrated.
ano.nymous@ccsd.cnrs.fr.invalid (A. Hauet) 15 May 2020
https://hal.inrae.fr/hal-02590813v1
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[hal-02601545] Recueil des données des annuaires hydrologiques 1939-1969 de la Société Hydrotechnique de France - Contribution au projet « Modélisation hydrologique distribuée du Rhône »
La Société Hydrotechnique de France a publié entre 1939 et 1969 une série d’annuaires hydrologiques incluant, entre autres, des observations de débits sur un ensemble de stations hydrométriques françaises et des contributions techniques ouvertes sur des sujets relatifs à l’hydrologie. Longtemps disponible sur support papier uniquement, le contenu de ces annuaires a été numérisé afin d’être porté à la connaissance de la communauté hydrologique. Les objectifs de ce rapport sont de partager l’expérience d’extraction des séries numériques et d’identifier les données complémentaires qui pourraient venir enrichir les connaissances apportées par la banque HYDRO.
ano.nymous@ccsd.cnrs.fr.invalid (C. Le Gros) 16 May 2020
https://hal.inrae.fr/hal-02601545v1
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[hal-02914572] A catalogue of European intermittent rivers and ephemeral streams
SMIRES is a COST Action addressing the Science and Management of Intermittent Rivers & Ephemeral Streams (coord. T. Datry, INRAE, and G. Singer, University of Innsbruck; http://www.smires.eu). This COST Action had brought together scientists from various research field and stakeholders to develop a European multidisciplinary network for synthesising the fragmented and recent knowledge on temporary water courses, improving our understanding of Intermittent Rivers and Ephemeral Streams (IRES) and translating this into a science-based, sustainable management of river networks. The working group “Prevalence, distribution and trends of IRES” (WG1) has the central role to provide the physical basis of the SMIRES Action. One of the tasks of WG1 was to compile flow gauging data at the European scale. As part of this work, examples of intermittent rivers and ephemeral streams were collected across Europe, including gauged catchments with both natural and highly influenced river flow regimes. A total of 40 examples have been put together in this catalogue to provide an overview of the variety of IRES in Europe. The selected IRES are not meant to be representative of all intermittent water courses in Europe but rather highlight the variety in these water courses. Introductory pages describe the procedures used to create the catalogue including definitions of the statistical measures reported for the individual intermittent rivers and ephemeral streams, and provide an overview of the catalogued water courses. Information on the selected gauged intermittent rivers and ephemeral streams is summarised in a two-page document: The first standardized page describes the main characteristics of the catchments (land-use, geology, climate, etc.) and the river flow regime. Two panels display the hydrographs and flow durations curves, and a table gives metrics specific to river flow intermittence relevant for ecology. The second page is dedicated to the description and reasons for intermittence. A short description about the spatio-temporal pattern of zero-flow events. This section may describe the seasonal behaviour of the stream, observed long-term trends, locations with frequently observed zero-flow events along the river network, etc. The monitoring network, including gauging stations and other types of observations (e.g. visual inspection of the flow states at different locations along the river) in the catchment, are also described.
ano.nymous@ccsd.cnrs.fr.invalid (Eric Sauquet) 12 Aug 2020
https://hal.science/hal-02914572v1
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[hal-01108400] Reconstitution des crues extrêmes du Gardon à partir d'une analyse paléohydrologique
Une étude paléo-hydrologique a été entreprise dans les Gorges du Gardon, où deux coupes sédimentaires ont été étudiées. La première provient d'une terrasse (coupe GE située à 10 m de hauteur au dessus de la rivière) et l'autre, d'une cavité (coupe GG localisée à 15 m au-dessus de la rivière). L'identification et la mise en évidence des différents paléo-événements de crue ont été établies grâce à l'inspection minutieuse de chaque dépôt sédimentaire et d'une étude géochronologique fine (137Cs, 210Pbex, 14C, métaux traces, objets archéologiques, historiques des crues). Nous avons souhaité évaluer la capacité des terrasses fluviatiles du Gardon à enregistrer des paléo-événements en comparant les coupes sédimentaires aux données historiques des hauteurs d'eau et aux résultats d'un modèle hydraulique 1D. Nous montrons que la terrasse GE enregistre la quasi-totalité des évènements du 20ème siècle et qu'à priori, ce type d'objet géomorphologique peut être utilisé pour toute étude paléo-hydrologique sur le Gardon. De plus, l'étude de la coupe GG (cavité perchée à 15 m) permet de reconstituer les évènements intenses au cours des 600 dernières années. Nous montrons une augmentation des crues extrêmes dans le Haut-Languedoc au cours du "Petit âge glaciaire".
ano.nymous@ccsd.cnrs.fr.invalid (L. Dezileau) 18 Feb 2015
https://hal.science/hal-01108400v1
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[hal-02593439] Extrapolation of rating curves by hydraulic modelling, with application to flood frequency analysis
This paper illustrates the importance of taking into account the potential errors in discharge estimation in the assessment of extreme floods. First, a summary of the main difficulties encountered in extrapolating rating curves for flood discharge is provided. Then a sensitivity analysis is carried out using a hydraulic modelling approach, applied to eight Mediterranean catchments, and yielding an envelope curve for the stagedischarge relationship, Q(H). To assess the influence of errors in the flood discharge on the uncertainty in estimating extreme floods, a Bayesian framework including a multiplicative error on the rating curve was applied. Its application on two catchments for which historical data are available for the period (17412004) shows that ignoring the rating curve errors may lead to an unduly optimistic reduction in the final uncertainty in estimation of flood discharge quantiles. Moreover, the quantile values are also affected by taking into account the rating curve errors.
ano.nymous@ccsd.cnrs.fr.invalid (M. Lang) 15 May 2020
https://hal.inrae.fr/hal-02593439v1
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[hal-02582964] Use of a statistical test based on Poisson process for the detection of changes in peak-over-threshold series
The great majority of statistical tests for detecting trends and other changes on extreme values deal with annual maximum or minimum series. This kind of tests cannot be used with historical series, where the requirement of continuity within the data records is not fulfilled year by year. A good alternative is to use peak over threshold series, which contain all the events larger than a threshold. Lang et al. (1999) provided some guidelines in order to choose an appropriate threshold. This includes a stationarity test based on the computation of the tolerance interval of the number of floods within a fixed interval. The null hypothesis is to assume that the flood process can be described by a homogeneous Poisson process. This paper presents a Monte Carlo experiment, which provides the statistical properties of this test (significance level and power), with the correspondence between two decision rules of rejection, at a fixed date or for the overall record period. The power of the Poisson test is compared with a set of classical statistical tests (Bois, Buishand, Kendall, Pettitt, Student), taking into account the position of the change within the series. An application of the Poisson test is presented on two long discharge series in France.
ano.nymous@ccsd.cnrs.fr.invalid (M. Lang) 15 May 2020
https://hal.inrae.fr/hal-02582964v1
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[hal-01743229] Retour sur l'étude prospective Garonne 2050
« Garonne 2050 » est une démarche prospective centrée sur l'eau : elle intègre le changement du climat et les évolutions possibles de la démographie, de l'énergie et de l'agriculture, ainsi que leurs impacts sur les ressources en eau. Elle répond
ano.nymous@ccsd.cnrs.fr.invalid (L. Lhuissier) 26 Mar 2018
https://hal.science/hal-01743229v1
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[hal-02579735] Discharge analysis and runoff mapping applied to the evaluation of model performance
Performance of hydrological models is usually assessed using the Nash critteria, based on differences between daily discharge time series. Two ways are investigated to extend the comparison tests. The firts one is based on other statistical analyses performed at the gauging stations. The second is based on interpolation procedures that are specific to discharge data. These approaches are used within Gewex-Rhône, a research project aiming to achieve a coupled modelling of continental and atmospheric water cycle components at mesoscale. Two versions of a distributed hydrological model (MODCOU and CIRSE) were applied to the French part of the Rhône basin (86200 km²) within this project. They provided a considerable amount of stimulated daily discharges to be objectively compared to observations.
ano.nymous@ccsd.cnrs.fr.invalid (Eric Sauquet) 14 May 2020
https://hal.inrae.fr/hal-02579735v1
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[hal-03286666] Identification de stations hydrométriques pour le diagnostic de modélisations hydrologiques à l’échelle nationale - Réflexions préparatoires au projet Explore2
Ce rapport présente l’analyse des données et des métadonnées disponibles dans la banque de données HYDRO (http://hydro.eaufrance.fr) dans le but de qualifier la pertinence des stations hydrométriques vis-à-vis d’un exercice de comparaison des débits observés à des sorties de modèles hydrologiques. Cet exercice s’inscrit dans le projet Explore 2 d’élaboration de projections hydro-climatiques pour le XXIe siècle. Les modèles hydrologiques qui simulent des débits en temps futur ont en effet besoin d’être contrôlés en comparant de la manière la plus objective les données simulées sous temps présent à des données d’observation aux stations hydrométriques. Le rapport mentionne les modalités de sélection des stations hydrométriques du précédent exercice Explore 2070, mais également d’autres jeux de stations établis par le Cemagref (devenu successivement Irstea et INRAE) en réponse à des besoins de recherche spécifiques. Des exemples de qualification de stations hydrométriques sont rappelés. Des critères de disponibilité, de représentativité et de qualité de données ont finalement été choisis et ont conditionné la constitution de deux jeux de données sur les périodes 1980-2009 et 1990-2019 de plus de 600 stations en France Métropolitaine. Ils répondent notamment aux exigences d’un régime naturel ou peu modifié par les actions humaines et d’une bonne qualité des mesures. Le croisement avec des bases de données recensant les influences (prélèvements en eau et présence d’ouvrages hydrauliques) apparait nécessaire pour confirmer les informations disponibles dans les métadonnées de la banque HYDRO. Ce rapport propose une première typologie de contextes hydrologiques où les modèles peuvent être pris à défaut (ex. les bassins transfrontaliers du fait d’un accès hypothétique à des données climatiques en dehors de la France ou ceux fortement influencés par le karst qui peut induire des discontinuités et des variabilités fortes dans les séries de débits). A chaque bassin versant qu’il soit jaugé ou non est attribuée une note qui reflète a priori la bonne aptitude d’un modèle hydrologique classique à simuler les débits à son exutoire. Le système de notation et le choix des stations où se fera le diagnostic des modèles hydrologiques, sera mis en débat dans le projet dans les prochaines étapes du projet Explore2 et si possible avec les gestionnaires des stations hydrométriques.
ano.nymous@ccsd.cnrs.fr.invalid (Théo Quenouillère) 15 Jul 2021
https://hal.science/hal-03286666v1
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[hal-02578018] Scénarios hydrologiques de référence : échelles spatiales et temporelles des probabilités de crue
L'analyse hydraulique des conséquences d'une crue repose sur l'utilisation d'un ou de plusieurs scénarios hydrologiques de référence. L'objectif des simulations est de caractériser le degré d'exposition d'une zone aux inondations, en terme de fréquence, hauteur, vitesse et durée de submersion. Ce dernier paramètre est pris explicitement en compte par les modèles Débit-durée-Fréquence (QdF) qui exploitent l'information disponible sur le volume des crues. La constitution des scénarios de référence fait intervenir des hydrogrammes d'apport qui doivent respecter certaines propriétés à l'échelle spatiale et temporelle. Le Cemagref a développé une technique de normalisation des modèles QdF et une technique d'assemblage de débits seuils de différentes durées, qui permet la construction d'hydrogrammes synthétiques, non événementiels, dont les volumes restent cohérents avec une période de retour de référence. Par ailleurs, le poids respectif des contributions des différents sous-bassins peut être estimé à partir de modèles de composition des distributions de crue sur une confluence.
ano.nymous@ccsd.cnrs.fr.invalid (M. Lang) 14 May 2020
https://hal.inrae.fr/hal-02578018v1
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[hal-02607381] 3rd European Conference on Flood Risk Management (FLOODrisk 2016)
[...]
ano.nymous@ccsd.cnrs.fr.invalid (M. Lang) 16 May 2020
https://hal.inrae.fr/hal-02607381v1
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[hal-01059669] A multidating approach applied to historical slackwater flood deposits of the Gardon River, SE France
A multidating approach was carried out on slackwater flood deposits, preserved in valley side rock cave and terrace, of the Gardon River in Languedoc, southeast France. Lead-210, caesium-137, and geochemical analysis of mining-contaminated slackwater flood sediments have been used to reconstruct the history of these flood deposits. These age controls were combined with the continuous record of Gardon flow since 1890, and the combined records were then used to assign ages to slackwater deposits. The stratigraphic records of terrace GE and cave GG were excellent examples to illustrate the effects of erosion/preservation in a context of a progressively self-censoring, vertically accreting sequence. The sedimentary flood record of the terrace GE located at 10 m above the channel bed is complete for years post-1958 but incomplete before. During the 78-year period 1880-1958, 25 floods of a sufficient magnitude (> 1450 m3/s) have covered the terrace. Since 1958, however, the frequency of inundation of the deposits has been lower:only 5 or 6 floods in 52 years have been large enough to exceed the necessary threshold discharge (> 1700 m3/s). The progressive increase of threshold discharge and the reduced frequency of inundation at the terrace could allow stabilisation of the vegetation cover and improved protection against erosion from subsequent large magnitude flood events. The sedimentary flood record seems complete for cave GG located at 15 m above the channel bed. Here, the low frequency of events would have enabled a high degree of stabilisation of the sedimentary flood record, rendering the deposits less susceptible to erosion. Radiocarbon dating are used in this study and compared to the other dating techniques.Eighty percent of radiocarbon dates on charcoals were considerably older than those obtained by the other techniques in the terrace. On the other hand, radiocarbon dating on seeds provided better results. This discrepancy between radiocarbon dates on charcoal and seeds is explained by the nature of the dated material (permanent wood vs. annual production and resistance to degradation process). Finally, we showed in this study that although the most common dating technique used in paleoflood hydrology is radiocarbon dating, usually on charcoal preserved within slackwater flood sediments, this method did not permitus to define a coherent age model. Only the combined use of lead-210, caesium-137, and geochemical analysis of mining-contaminated sediments with the instrumental flood record can be applied to discriminate and date the recent slackwater deposits of the terrace GE and cave GG.
ano.nymous@ccsd.cnrs.fr.invalid (L. Dezileau) 01 Sep 2014
https://hal.science/hal-01059669v1
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[hal-01062751] Evénements extrêmes d’inondation : de l’étude de l’aléa à la gestion risques pour les ouvrages hydrauliques. Lyon, 13‑14 novembre 2013. Bilan du colloque
Principaux enseignements du colloque : limites de l'approche probabiliste classique et intérêt de mobiliser des sources d'information complémentaires pour l'estimation des crues extrêmes (régionalisation, crues anciennes, simulation d'averses). / Main recommendations from the conference : limits of the standard flood frequency methods and interest of using additional information for extreme flood assessment (regional information, historical and paleoflood information, rainfall-runoff methods).
ano.nymous@ccsd.cnrs.fr.invalid (M. Lang) 10 Sep 2014
https://hal.science/hal-01062751v1
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[hal-02601429] Garonne 2050. Un exercice de prospective participative sur la gestion de l’eau du bassin de la Garonne
Alors que se profile la prochaine conférence des parties à la Convention-cadre des Nations unies sur les changements climatiques (COP), prévue fin 2015 à Paris, les questions climatiques font l’objet de nombreux articles et débats, mais rares sont ceux qui les examinent à l’échelle « micro ». Pourtant, de nombreuses régions, en France notamment, ressentent d’ores et déjà les impacts de ces changements (sécheresses, pluies torrentielles à répétition...) et devraient se préoccuper davantage des conséquences à moyen-long terme de ces modifications climatiques. L’Agence de l’eau Adour-Garonne, en charge de la gestion des eaux du Grand Sud-Ouest, a fait cet effort et réalisé un exercice de prospective entre 2010 et 2013, en vue d’adapter la gestion de la ressource hydrique aux évolutions à venir d’ici 2050. Cet article revient sur cette démarche, intitulée « Garonne 2050 », résolument participative, qui montre bien l’ampleur des défis à venir dans cette région à la fois agricole et attractive, souffrant de manière récurrente d’un manque d’eau l’été. Après un rappel des scénarios exploratoires et des quantifications ayant servi de point de départ, les auteurs présentent les trois scénarios stratégiques retenus, orientés autour de deux déterminants clefs : le déficit d’eau lié au changement climatique et les prélèvements destinés à l’agriculture. Ils montrent ensuite quel compromis a été retenu et pourquoi, soulignant le courage politique nécessaire à un exercice d’anticipation dont l’horizon (2050) et les conclusions ont de quoi désarçonner les acteurs et populations concernés.
ano.nymous@ccsd.cnrs.fr.invalid (Y Arama) 16 May 2020
https://hal.inrae.fr/hal-02601429v1
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[hal-04764953] Multi-objective calibration and evaluation of the ORCHIDEE land surface model over France at high resolution
Here we present a strategy to obtain a reliable hydrological simulation over France with the ORCHIDEE land surface model. The model is forced by the SAFRAN atmospheric reanalysis at 8 km resolution and hourly time steps from 1959 to 2020 and by a high-resolution DEM (around 1.3 km in France). Each SAFRAN grid cell is decomposed into a graph of hydrological transfer units (HTUs) based on the higher-resolution DEM to better describe lateral water movements. In particular, it is possible to accurately locate 3507 stations among the 4081 stations collected from the national hydrometric network HydroPortail (filtered to drain an upstream area larger than 64 km2). A simple trial-and-error calibration is conducted by modifying selected parameters of ORCHIDEE to reduce the biases of the simulated water budget compared to the evapotranspiration products (the GLEAM and FLUXCOM datasets) and the HydroPortail observations of river discharge. The simulation that is eventually preferred is extensively assessed with classic goodness-of-fit indicators complemented by trend analysis at 1785 stations (filtered to have records for at least 8 entire years) across France. For example, the median bias of evapotranspiration is −0.5 % against GLEAM (−4.3 % against FLUXCOM), the median bias of river discharge is 6.3 %, and the median Kling–Gupta efficiency (KGE) of square-rooted river discharge is 0.59. These indicators, however, exhibit a large spatial variability, with poor performance in the Alps and the Seine sedimentary basin. The spatial contrasts and temporal trends of river discharge across France are well represented with an accuracy of 76.4 % for the trend sign and an accuracy of 62.7 % for the trend significance. Although it does not yet integrate human impacts on river basins, the selected parameterization of ORCHIDEE offers a reliable historical overview of water resources and a robust configuration for climate change impact analysis at the nationwide scale of France.
ano.nymous@ccsd.cnrs.fr.invalid (Peng Huang) 04 Nov 2024
https://hal.science/hal-04764953v1
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[hal-02607519] Coupled modelling of macroinvertebrate communities and river hydraulic habitat under climate change scenarios for the Loire river basin, France
Human induced-physical habitat alterations are the main threat to aquatic ecosystems. In a context of climate change, these alterations could be exacerbated by changes in low flow regimes, inducing modifications of aquatic communities. Understanding the links between aquatic communities, their physical habitat and climate change is therefore a major but difficult challenge because climate change can interact with other anthropogenic pressures, thus confounding their effects. In this study, we simulate potential macroinvertebrate hydraulic habitat alterations due to predicted more extreme low flows on the Loire River watershed, regardless of other anthropogenic pressures. By coupling a species distribution model and a habitat model that combines a model of shear stress distribution with a macroinvertebrate preference model, we are able to point out changes in community structure in response to shifts in habitat availability. By isolating more extreme low flows effects on macroinvertebrate communities, we emphasize natural sensitivities to climate change and provide a frame to better understand how anthropogenic pressures could exacerbate them.
ano.nymous@ccsd.cnrs.fr.invalid (Marie-Line Merg) 16 May 2020
https://hal.inrae.fr/hal-02607519v1
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[hal-03369942] Classification and trends in intermittent river flow regimes in Australia, northwestern Europe and USA: A global perspective
This study examines the spatial and temporal variability of flow intermittence over the period 1970–2018 across four countries (Australia, France, UK and the conterminous USA). Intermittence (no-flow periods) in 471 un-regulated non-perennial rivers were analyzed using flow data collected from 1356 gauging stations distributed across the four countries. Climate data were also analyzed to place findings within a climate-change context. Intermittence of streamflow demonstrated high seasonality and showed regional differences. An aridity index was the most relevant explanatory factor of flow intermittence at the global scale; the more arid the climate, the higher the probability of non-perennial flow regimes. Flow intermittence was observed, however, in humid climate zones. A global classification of intermittent rivers was developed that included all the facets of the flow regime. This classification served as a basis for trend detection in annual frequency of no flows at the regional scale. Some, but not all, of the 14 examined regions in Australia and the US displayed significant trends and most of them displayed an upward trend in the occurrence of no-flow days.
ano.nymous@ccsd.cnrs.fr.invalid (Eric Sauquet) 07 Oct 2021
https://hal.inrae.fr/hal-03369942v1
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[hal-02607367] Ecologically relevant flow metrics for intermittent rivers and ephemeral streams
The COST-Action SMIRES brings together scientists from various disciplines to foster a common understanding of hydrology, hydrochemistry and ecology of intermittent rivers and ephemeral streams. Such rivers are characterized by episodes of stagnant waters or drying-off, occurring either annually during the drought season or exceptionally during extreme drought years. Since intermittency can be seen as a special case of low-flow regimes that reach zero-flow, relevant low flow characteristics exist but need to be adopted to characterise ecologically relevant features of the particular flow regime. In this paper we present a set of metrics for characterizing flow intermittency in an ecologically relevant way, stemming from interdisciplinary discussions among SMIRES experts of various disciplines. The indices are compatible with standard low flow indices of the WMO manual on low flow estimation and prediction (Gustard and Demuth, 2008) and the handbook Hydrological Drought (Tallaksen and Van Lanen, 2004), extending these indices to noflow conditions. The metrics characterise the statistical distribution including mean and variance of the proportion of no-flow years, the annual number of no-flow-days, the duration of no-flow spells and the timing of seasonality of onset and termination of no-flow spells. In addition, the dynamics of drying-off and rewetting are characterized. An R software package (Gauster and Laaha, 2017) has been compiled that enables uniform calculation of indices at the annual, seasonal and monthly scale, suitable for a broad range of hydrological regimes. The paper concludes with illustrating examples of how the metrics can be applied in eco-hydrological studies of rivers that cease to flow.
ano.nymous@ccsd.cnrs.fr.invalid (G. Laaha) 16 May 2020
https://hal.inrae.fr/hal-02607367v1
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[hal-02597051] Floods in the Alpine areas of Europe
Within the European AdaptAlp initiative (http://www.adaptalp.org/), a specific focus was the detection of trends on river flow regimes in the Alps. The AdaptAlp dataset comprises 177 long series of daily runoff collected over the Alpine region (Austria, France, Germany, Italy, Slovenia and Switzerland). These series cover at least 40 years of daily record, are related to undisturbed catchments and have been thoroughly quality-checked by the partners of the project. A trend analysis was carried out on snowmelt flow indices occurring in spring and summer. Statistical analysis was applied at a local level, testing each site independently and checking its field significance, and secondly with a regional procedure was applied to test if all the stations belonging to the same homogeneous region behave in the same way. The main significant trends can be summarized as follows: 1/ higher spring snowmelt-related flows; 2/ an increase in the volume and peak of snowmelt flows for glacier regimes; 3/ an increase in the duration of the snowmelt season for snowmelt regimes, along with an earlier start to the beginning of the snowmelt season.
ano.nymous@ccsd.cnrs.fr.invalid (Antony Bard) 16 May 2020
https://hal.inrae.fr/hal-02597051v1
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[hal-03138300] Aqua temporaria incognita
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ano.nymous@ccsd.cnrs.fr.invalid (H. J. Ilja Meerveld) 24 Feb 2021
https://hal.science/hal-03138300v1
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[hal-00453855] Analyse régionale sur les extrêmes hydrométriques en France : détection de changements cohérents et recherche de causalité hydrologique
Cet article présente les résultats d'une étude nationale sur la détection de tendances dans les extrêmes hydrométriques en France (crues et étiages). Si un grand nombre d'évolutions ont été constatées, plus de la moitié peuvent être expliquées par des causes non climatiques, en particulier métrologiques. Une nouvelle analyse régionale sur un jeu critiqué de données ne montre aucun changement généralisé dans le régime des rivières en France. Des comportements spécifiques ont toutefois été mis en évidence, sur les bassins de montagne, en relation avec l'augmentation des températures, et sur le Nord-Est de la France, avec une augmentation du nombre de jours pluvieux et des pics de crue. / This paper presents a national study on the detection of climatic changes in hydrological extremes in France. A high number of changes have been detected but after an extensive criticism of data, half of these changes can be related to non-climatic factors, especially metrological issues. A regional analysis based on a reduced number of stations, whose quality can be insured, doesn't show a consistent and generalized change in French rivers. Specific behaviours have been explained in mountainous basins, related to the increasing of temperature, and in the North-East of France with an increasing of both rainfall and flood peaks.
ano.nymous@ccsd.cnrs.fr.invalid (M. Lang) 05 Feb 2010
https://hal.science/hal-00453855v1
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[hal-04644992] Assessing the impact of climate change on groundwater resources over France: results from the Explore 2 project.
Explore 2 is a multi-partner project supported by the French Ministry of the Environment aimed at assessing the impact of climate change on water resources by 2100 in France. The present study focuses on estimating this impact on groundwater resources. The climate change projections correspond to a selection of regional climate projections based on the EURO-CORDEX database and made available by Météo France on the DRIAS website (https://www.drias-climat.fr/). These regional climate projections were corrected biases in relation to the SAFRAN historical meteorological dataset using the adjustment method ADAMONT (Verfaillie et al., 2017). They rely on the three greenhouse emission scenarios RCP 2.6, RCP4.5 and RCP8.5 according to the CMIP5 exercise. Several modelling tools covering all or part of France provide hydrogeological projections according to those climate projections. A calculation method based on the soil water balance (Caballero et al., 2021) estimates variations in recharge across France. The AquiFR modelling platform (Vergnes et al. 2020) provides access to variations in piezometric levels over part of the sedimentary basins, including the Paris basin. The North-Aquitanian model (Satlel et al., 2019) provide changes in the deep aquifers in the Aquitanian region. Finally, a lumped-parameter hydrological model developed with the EROS computer code (Thiéry 2018) yields groundwater levels at a selection of piezometers across Brittany. Preliminary results based on the RCP8.5 scenario show that France will be wetter at the end of the century in the northern half of the country regarding the groundwater resources evolution, and drier in the southern half. However, a large dispersion characterizes the ensemble of hydrogeological projections. This dispersion involves contrasting evolution in seasonal trends and extreme events occurrence between the models. It reflects uncertainties in the regional climate projections and in the hydrogeological model structures.
ano.nymous@ccsd.cnrs.fr.invalid (Jean-Pierre Vergnes) 11 Jul 2024
https://brgm.hal.science/hal-04644992v1
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[hal-01141621] Multi-scale hydrometeorological observation and modelling for flash-flood understanding
This paper presents a coupled observation and modelling strategy aiming at improving the understanding of processes triggering flash floods. This strategy is illustrated for the Mediterranean area using two French catchments (Gard and Ardèche) larger than 2000 km2. The approach is based on the monitoring of nested spatial scales: (1) the hillslope scale, where processes influencing the runoff generation and its concentration can be tackled; (2) the small to medium catchment scale (1–100 km2), where the impact of the network structure and of the spatial variability of rainfall, landscape and initial soil moisture can be quantified; (3) the larger scale (100–1000 km2), where the river routing and flooding processes become important. These observations are part of the HyMeX (HYdrological cycle in the Mediterranean EXperiment) enhanced observation period (EOP), which will last 4 years (2012–2015). In terms of hydrological modelling, the objective is to set up regional-scale models, while addressing small and generally ungauged catchments, which represent the scale of interest for flood risk assessment. Topdown and bottom-up approaches are combined and the models are used as “hypothesis testing” tools by coupling model development with data analyses in order to incrementally evaluate the validity of model hypotheses. The paper first presents the rationale behind the experimental set-up and the instrumentation itself. Second, we discuss the associated modelling strategy. Results illustrate the potential of the approach in advancing our understanding of flash flood processes on various scales.
ano.nymous@ccsd.cnrs.fr.invalid (Isabelle Braud) 13 Apr 2015
https://hal.science/hal-01141621v1
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[hal-02608477] Real-time Bayesian estimation of stage-discharge rating curves during floods
Streamflow estimation in real time is required for data assimilation by flood forecasting systems. Streamflow time series are established using 'rating curves' that approximate the stage-discharge relationship. A major problem is that the river bed at many hydrometric stations can evolve due to morphogenic floods, leading to rating changes, or 'shifts'. The methods proposed in the literature for updating the rating curve are based on a retrospective statistical analysis of calibration data (or gaugings). The aim of the proposed method is the automatic detection of shifts and the estimation of their magnitude in real time, using both observational data and hydraulic knowledge of the site. It is built on an existing Bayesian framework for estimating probabilistic stage-discharge rating curves with quantitative uncertainties. Before starting a real-time application, a retrospective analysis is performed to detect past changes typically based on available gaugings. The retrospective results are then used to calibrate the methods for detecting and estimating shifts and their magnitudes in real-time. To this aim, the method uses different sources of information available in real time, e.g. stage records, estimates of the sediment transport that affects the bed evolution, changes in the shape of recession curves, changes in correlations with neighbouring hydrometric stations, etc. The proposed method was applied to the Ardèche River at Meyras, France, a river with a gravel-bed degrading during each flood. Both retrospective analysis and real-time estimation of the stage-discharge rating curves yielded encouraging results, with consistent detection of shifts and estimation of their magnitudes. Further research includes testing the method at more challenging sites and the use of other useful information available in real-time. The final goal is to provide real-time streamflow estimates with uncertainties that can be assimilated in models and decision making.
ano.nymous@ccsd.cnrs.fr.invalid (M. Darienzo) 16 May 2020
https://hal.inrae.fr/hal-02608477v1
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[hal-02593967] Comparison of catchments grouping methods for flow duration curve estimation at ungauged sites an application to France
Cette communication a pour objet les travaux de régionalisation des courbes des débits classés en France. Trois points sont évoqués : la construction d'un modèle synthétique décrivant les courbes à l'aide d'un nombre réduits de paramètres, la construction de régions hydrologiques, supports des formules empiriques reliant les paramètres à des caractéristiques de bassin. Plusieurs types de régions sont ici testés.
ano.nymous@ccsd.cnrs.fr.invalid (C. Catalogne) 15 May 2020
https://hal.inrae.fr/hal-02593967v1
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[hal-03295467] Design flood assessment on the upper Rhine using historical data and accounting for discharge uncertainty
Design floods on the upper Rhine River are a major issue for French-German agreements on flood embankments. As intense river training has modified the Rhine River morphology during the 19th century, with a significant rectification of the river course, some disagreement does exist on the interest and value of including information on historical floods. Some hydrological studies are using discharge series from the 20th century only, arguing that it is not possible to estimate flood discharge correctly during and before the river works of the 19th century. Other studies include a set of large historical floods during the 19th century. Unfortunately, design flood estimates with or without historical information are significantly different. We used two long discharge series in Basel-Switzerland (1808-2018, with a set of historical floods since 1268) and Maxau-Germany (1815-2018). A preliminary analysis allowed crossing different archive sources, correcting data to account for the main river corrections (1714 and 1890), checking the homogeneity of data and assessing the uncertainty of the stage-discharge relationship. We present a comparative study of design floods with several distributions and several series lengths (a few decades to several centuries). A statistical Bayesian framework allows comparing design floods and the corresponding uncertainties.
ano.nymous@ccsd.cnrs.fr.invalid (Lang Michel) 22 Jul 2021
https://hal.science/hal-03295467v1
