Correction of upstream flow and hydraulic state with data assimilation in the context of flood forecasting

The present study describes the assimilation of river water level observations and the resulting improvement in flood forecasting. The Kalman Filter algorithm was built on top of a one-dimensional hydraulic model which describes the Saint-Venant equations. The assimilation algorithm folds in two steps: the first one was based on the assumption that the upstream flow can be adjusted using a three-parameter correction; the second one consisted of directly correcting the hydraulic state. This procedure was applied using a four- day sliding window over the flood event. The background error covariances for water level and discharge were repre- sented with anisotropic correlation functions where the cor- relation length upstream of the observation points is larger than the correlation length downstream of the observation points. This approach was motivated by the implementation of a Kalman Filter algorithm on top of a diffusive flood wave propagation model. The study was carried out on the Adour and the Marne Vallage (France) catchments. The correction of the upstream flow as well as the control of the hydraulic state during the flood event leads to a significant improve- ment in the water level and discharge in both analysis and forecast modes

Influence of Hydrocarbons Exposure on Survival, Growth and Condition of Juvenile Flatfish

Juveniles of numerous commercial marine flatfish species use coastal and estuarine habitats as nurseries. Hence, they are likely to be exposed to a number of anthropogenic stressors such as accidental and chronic exposure to chemical contaminants. Little is known about their response to such pollutants at the individual level and about the consequences on their population dynamics. Mesocosm experiments were conducted to determine whether short (24 h) but high exposure to petroleum hydrocarbons (1/1000 v: v water: fuel), similar to what happened after an oil spill on coastal areas, af fects survival and biological (growth, body condition and lipid reserve) performances of juvenile common sole, which live on near shore and estuarine nursery grounds. Results demonstrated that this type of exposure significantly reduce survival, growth (size, recent otolith increment and body condition), and especially ener gy storage (triacylglycerol to free sterol ratio) of the juvenile fish on the medium-term (three months after the exposure).These medium-term consequences affect future recruitment of this long- lived species

Ensemble-based data assimilation for operational flood forecasting – On the merits of state estimation for 1D hydrodynamic forecasting through the example of the “Adour Maritime” river

This study presents the implementation and the merits of an Ensemble Kalman Filter (EnKF) algorithm with an inflation procedure on the 1D shallow water model MASCARET in the framework of operational flood forecasting on the “Adour Maritime” river (South West France). In situ water level observations are sequentially assimilated to correct both water level and discharge. The stochastic estimation of the background error statistics is achieved over an ensemble of MASCARET integrations with perturbed hydrological boundary conditions. It is shown that the geometric characteristics of the network as well as the hydrological forcings and their temporal variability have a significant impact on the shape of the univariate (water level) and multivariate (water level and discharge) background error covariance functions and thus on the EnKF analysis. The performance of the EnKF algorithm is examined for observing system simulation experiments as well as for a set of eight real flood events (2009–2014). The quality of the ensemble is deemed satisfactory as long as the forecast lead time remains under the transfer time of the network, when perfect hydrological forcings are considered. Results demonstrate that the simulated hydraulic state variables can be improved over the entire network, even where no data are available, with a limited ensemble size and thus a computational cost compatible with operational constraints. The improvement in the water level Root-Mean-Square Error obtained with the EnKF reaches up to 88% at the analysis time and 40% at a 4-h forecast lead time compared to the standalone model

Zones fonctionnelles pour les ressources halieutiques dans les eaux sous souveraineté française: Deuxième partie : Inventaire. Rapport d'étude. Les publications du Pôle halieutique AGROCAMPUS OUEST n°46

Suite à l’adoption de la loi pour la reconquête de la biodiversité, de la nature et des paysages, une nouvelle catégorie d’Aire Marine Protégée, appelée "zone de conservation halieutique" (ZCH) a été créée, leur vocation étant de préserver ou de restaurer des zones fonctionnelles importantes pour le cycle de vie des ressources halieutiques. Le Ministère de l’Environnement, de l’Energie et de la Mer a donc souhaité faire répertorier les zones fonctionnelles halieutiques d’ores et déjà connues dans les eaux territoriales françaises. Pour chaque façade maritime métropolitaine, la seconde partie de ce travail, présentée dans ce rapport, s’est organisée en 4 étapes :•Dresser la liste des zones fonctionnelles halieutiques identifiées de manière quantitative et les présenter sous forme d’atlas cartographique ;•Réaliser un inventaire des campagnes scientifiques halieutiques de poursuivre ce travail d’identification des zones fonctionnelles halieutiques ;•Présenter une synthèse des méthodes permettant d’identifier les zones fonctionnelles halieutiques à partir des données de suivi de la pêche professionnelle ;•Compléter cet inventaire de cartes, de données et de méthodes avec les connaissances cartographiques non quantitatives issues de l’expertise des scientifiques, des gestionnaires et des professionnels de la pêche

La démarche de développement d’indicateurs basés sur l’ichtyofaune pour évaluer la qualité écologique des eaux de transition françaises dans le cadre de la DCE : une marche forcée pour des résultats positifs

Cet article se propose d’expliquer, sur l’exemple de l’ichtyofaune des masses d’eau de transition, la démarche adoptée par la France pour répondre aux objectifs de la DCE et les défis qu’elle présentait dans des délais contraints. Nous présentons le vide de connaissances et de données qui régnait au début des années 2000 et les actions mises en œuvre au pas de charge pour répondre aux objectifs ambitieux de la DCE, disposer d’un réseau de surveillance en 2007, puis d’indicateurs normés décrivant l’état écologique afin de présenter un bilan six ans plus tard, en 2013, à l’issue du premier plan de gestion. Il reste désormais à poursuivre la démarche en milieu marin dans le cadre de la DCSMM.In this paper, we propose to study fish in transition waters to illustrate the challenge of meeting the goals of the European Union Water Framework Directive (EWFD) in France in restricted delays. We present the lack of knowledge and data in early 2000s and the actions led then to achieve the ambitious objectives of the EWFD: the creation of a standardized monitoring network in 2007 and the definition of ecological indicators based on the fish community. In 2013, at the end of the first management plan, an assessment of the ecological status was presented. These actions have now to be continued towards marine waters in relation with the EU Marine Strategy Framework Directive

Crecimiento y condición de juveniles de lenguado (Solea solea L.) como indicadores de calidad de hábitat en áreas de cría costeras y estuáricas del Golfo de Vizcaya con énfasis en zonas expuestas al vertido del Erika

Indicators of growth and condition were used to compare the habitat quality of nurseries of juvenile sole (Solea solea L.) in the Bay of Biscay, based on one survey in 2000. The four biological indicators are poorly correlated with each other, suggesting that no single measure may give an adequate description of fish health and of its habitat’s quality. Growth indicators showed significant differences between northern and southern areas. Juveniles from the two southernmost nurseries, the Gironde estuary and the Pertuis Antioche, displayed significant lower otolith increment widths and mean sizes. These differences were inversely related to water temperature and unrelated to genetic or age differences, and are unlikely to be due to limiting trophic conditions in the nurseries. Hence, they may be considered in terms of differences in habitat quality and potential anthropogenic impacts. Condition indices do not show this north-south pattern but highlight low condition values in the Pertuis Antioche. Short-term and fluctuating biochemical indicators such as RNA/DNA ratios appeared to be unreliable over a long-term study, while morphometric indices seemed to be relevant, complementary indicators as they integrate the whole juvenile life-history of sole in the nurseries. The growth and condition indices of juveniles in September 2000 from nursery grounds exposed to the Erika oil spill in December 1999 were relatively high. These results lead us to suggest that there was no obvious impact of this event on the health of juvenile sole and on the quality of the exposed nursery grounds a few months after the event.Se usaron indicadores de crecimiento y condición de lenguados juveniles (Solea solea L.) para comparar la calidad del hábitat de áreas de cría en el Golfo de Vizcaya basados en un muestreo de 2000. Los cuatro indicadores biológicos mostraron bajas correlaciones entre sí, lo que sugiere que no existe una medida única para describir adecuadamente el estado de los peces y la calidad de su hábitat. Los indicadores de crecimiento mostraron diferencias significativas entre las áreas septentrionales y meridionales. Los juveniles de las áreas situadas más al sur: el estuario del Garona y Pertuis Antioche mostraron incrementos de otolitos y tamaños medios significativamente inferiores. Estas diferencias están inversamente relacionadas con la temperatura del agua, pero no con diferencias genéticas o de edad, y no es probable que se deba a una condición trófica limitante en las áreas de cría. Por tanto, pueden considerarse en términos de calidad del hábitat y el potencial impacto antropogénico. Los índices de condición no muestras este patrón norte-sur sino que destacan los bajos valores de condición en Pertuis Antioche. Los indicadores bioquímicos variables de corto término como las relaciones RNA/DNA no parecieron fiables para estudios de mayor escala, mientras que los índices morfométricos parecen ser relevantes y complementarios ya que integran toda el período juvenil de la vida de los lenguados en sus áreas de cría. Los valores de crecimiento y condición de juveniles en septiembre de 2000 en áreas de cría expuestas al vertido de crudo del Erika en diciembre de 1999 fueron relativamente elevadas. Estos resultados sugieren que no hubo un impacto obvio de este evento sobre la salud de los juveniles de lenguado ni en la calidad de las áreas de cría expuestas transcurridos unos pocos meses después del vertido

Fish under influence: a macroecological analysis of relations between fish species richness and environmental gradients among European tidal estuaries

Estuarine fish assemblages are subject to a great environmental variability that largely depends on both upstream fluvial and downstream marine influences. From this ecohydrological view, our study introduces a macroecological approach aiming to identify the main environmental factors that structure fish assemblages among European tidal estuaries. The present paper focuses on the influence of large scale environmental gradients on estuarine fish species richness. The environment of 135 North-eastern Atlantic estuaries from Portugal to Scotland was characterized by various descriptors especially related to hydromorphology. Major environmental trends among estuaries were underlined using multivariate techniques and cluster analyses applied to abiotic data. In particular, an integrative system size covariate was derived from a principal component analysis. Factors explaining patterns of species richness at different scales from local habitat to regional features were highlighted. Based on generalised linear models, the estuarine system size, and more particularly the entrance width, and also the continental shelf width were identified as the best explanatory variables of estuarine fish species richness at a large scale. Our approach provides a standardized method to estimate the relationship between fish assemblages and environmental factors. This constitutes a first step in assessing estuarine ecological status and studying the effects of additional factors such as anthropogenic disturbances

Data Assimilation And Multidimensional Model Coupling On The Adour Catchment, South-West Of France

This study focuses on the hydrodynamic modelling of the tidally influenced “Adour maritime” catchment located in South-West of France. The local SPC is in charge of operational flood-forecasting and for that purpose, the 1D hydraulic software MASCARET developed at EDF is used. Due to various sources of uncertainties on the hydraulic parameters and hydrological forcing, the free-run is imperfect and should be corrected for improved forecast of extreme events. An Ensemble Kalman Filter algorithm was implemented on top of the hydraulic model using the OpenPalm coupler to assimilate hourly water level in-situ data from observing stations. The water-level and discharge state is sequentially corrected thus providing and improved initial state for short to medium range forecast (3h-6h). The impact of the data assimilation analysis on the entire network and for the non-assimilated variables is investigated for several major flood events. It was also shown that the reliability of the forecast closely relates to the number of members used in the EnKF algorithm. In the present study, about 20 members are necessary. As these members can be run in parallel, the cost of the ensemble-based assimilation remains compatible with real-time flood-forecasting constraints. The corrected 1D simulation provides the boundary conditions for a limited-area 2D model. The TELEMAC software, developed at EDF, is used to represent the flow for the confluence between Nive and Adour rivers (in the center of the Bayonne city) as well as in the Plaine d\u27Ansot (located upstream of Bayonne) where the flow is no longer mono-dimensional. The 1D (with data assimilation) and the 2D model overlap, they are coupled in order to build a data-driven high-fidelity model for the Adour catchment for operational use in the framework of flood-forecasting