Modelling the water budget and the riverflows of the Maritsa basin in Bulgaria

International audienceA soil-vegetation-atmosphere transfer model coupled with a macroscale distributed hydrological model was used to simulate the water cycle for a large region in Bulgaria. To do so, an atmospheric forcing was built for two hydrological years (1 October 1995 to 30 September 1997), at an eight km resolution. The impact of the human activities on the rivers (especially hydropower or irrigation) was taken into account. An improvement of the hydrometeorological model was made: for better simulation of summer riverflow, two additional reservoirs were added to simulate the slow component of the runoff. Those reservoirs were calibrated using the observed data of the 1st year, while the 2nd year was used for validation. 56 hydrologic stations and 12 dams were used for the model calibration while 41 river gauges were used for the validation of the model. The results compare well with the daily-observed discharges, with good results obtained over more than 25% of the river gauges. The simulated snow depth was compared to daily measurements at 174 stations and the evolution of the snow water equivalent was validated at 5 sites. The process of melting and refreezing of snow was found to be important in this region. The comparison of the normalized values of simulated versus measured soil moisture showed good correlation. The surface water budget shows large spatial variations due to the elevation influence on the precipitation, soil properties and vegetation variability. An inter-annual difference was observed in the water cycle as the first year was more influenced by Mediterranean climate, while the second year was characterised by continental influence. The energy budget shows a dominating sensible heat component in summer, due to the fact that the water stress limits the evaporation. This study is a first step for the implementation of an operational hydrometeorological model that could be used for real time monitoring and forecasting of water budget components and river flow in Bulgaria

The SAFRAN-ISBA-MODCOU hydrometeorological model applied over France

An edited version of this paper was published by AGU. Copyright (2008) American Geophysical UnionThe hydrometeorological model SIM consists in a meterological analysis system (SAFRAN), a land surface model (ISBA) and a hydrogeological model (MODCOU). It generates atmospheric forcing at an hourly time step, and it computes water and surface energy budgets, the river ow at more than 900 rivergauging stations, and the level of several aquifers. SIM was extended over all of France in order to have a homogeneous nation-wide monitoring of the water resources: it can therefore be used to forecast flood risk and to monitor drought risk over the entire nation. The hydrometeorologival model was applied over a 10-year period from 1995 to 2005. In this paper the databases used by the SIM model are presented, then the 10-year simulation is assessed by using the observations of daily stream-flow, piezometric head, and snow depth. This assessment shows that SIM is able to reproduce the spatial and temporal variabilities of the water fluxes. The efficiency is above 0.55 (reasonable results) for 66 % of the simulated rivergages, and above 0.65 (rather good results) for 36 % of them. However, the SIM system produces worse results during the driest years, which is more likely due to the fact that only few aquifers are simulated explicitly. The annual evolution of the snow depth is well reproduced, with a square correlation coeficient around 0.9 over the large altitude range in the domain. The stream ow observations were used to estimate the overall error of the simulated latent heat ux, which was estimated to be less than 4 %

Quelques aspects du cycle continental de l'eau

Quelques aspects de la modélisation du cycle continental de Veau à l'échelle régionale sont évoqués. Après avoir résumé les bases physiques de la modélisation des échanges d'énergie et de masse à l'interface sol-plante-atmosphère , l'article présente quelques exemples de validation d'un schéma à partir de données réelles. L'apport de la modélisation atmosphérique à mésoéchelle du cycle de l'eau est évoqué à travers la simulation appliquée aux données issues de grandes campagnes de mesures expérimentales. Enfin, l'article dessine les perspectives de couplage entre modélisation atmosphérique et hydrologique permettant une meilleure description du cycle annuel de l'eau à l'échelle régionale.Noilhan Joël. Quelques aspects du cycle continental de l'eau. In: L'eau, l'homme et la nature. 24èmes journées de l'hydraulique. Congrès de la Société Hydrotechnique de France. Paris, 18-19-20 septembre 1996. 1996

Modélisation des processus de surface et de la couche limite en milieu urbain

TOULOUSE3-BU Sciences (315552104) / SudocSudocFranceF

Le programme d'intercomparaison de schémas de surface PILPS : Description des résultats obtenus avec ISBA

This note presents the results of simulations carried out with the ISBA scheme (and its predecessor ASTEC) as part of the Project for Intercomparison of Land surface Parameterization Schemes (PILPS) initiated by the GEWEX program. These are point simulations in forced mode over an annual cycle using atmospheric parameters from the NCAR general circulation model over three contrasting areas: the Amazon rainforest, a prairie in Great Britain and a tundra in northern Canada. Despite the rather unrealistic forcing data, the results obtained with ISBA appear plausible. This scheme shows a better representation of water transfers than its predecessor ASTEC. A very simple snow scheme is also described and its behavior compared to a multi-layer model. This scheme was further improved by Douville et al (1995). The results of this first intercomparison were published by A. Pitman et al. in 1999 (https://doi.org/10.1007/s003820050309) and showed that the ISBA scheme behaved close to the average of the 16 schemes that took part in this first PILPS exercise.Cette note présente les résultats de simulations réalisées avec le schéma ISBA (et son prédécesseur ASTEC) dans le cadre du projet d'intercomparaison des schémas de surface (PILPS) à l'initiative du programme GEWEX. Il s'agit de simulations ponctuelles en mode forcé sur un cycle annuel avec des paramètres atmosphériques issus du modèle de circulation générale du NCAR sur trois zones contrastées : la forêt amazonienne, une prairie en Grande-Bretagne et une toundra au Nord du Canada. Malgré des données de forçage assez peu réalistes les résultats obtenus avec ISBA apparaissent vraisemblables. Ce schéma montre une meilleure représentation des transferts hydriques par rapport à son prédécesseur ASTEC. Un schéma de neige très simple est également décrit et son comportement comparé à un modèle multi-couches. Ce schéma fera l'objet d'améliorations par Douville et al. (1995). Les résultats de cette première intercomparaison seront publiés par A. Pitman et al. en 1999 (https://doi.org/10.1007/s003820050309) et montreront que le schéma ISBA à un comportement proche de la moyenne des 16 schémas ayant participé à ce premier exercice PILPS

Modélisation distribuée des flux d'eau et d'énergie et des débits à l'échelle régionale du bassin Adour-Garonne

TOULOUSE3-BU Sciences (315552104) / SudocPARIS-BIUSJ-Sci.Terre recherche (751052114) / SudocSudocFranceF

Typologie des sécheresses sur la France et outils de suivi de la ressource en eau utilisés à Météo-France

La France a subi des sécheresses en 2003, 2005, 2006, dont les conséquences, notamment sur les bâtiments ont mis en lumière l'importance de ce risque naturel. En raison de ses missions, Météo-France suit l'ensemble des phénomènes météorologiques, dont les sécheresses, via la quantification des déficits pluviométriques observés par un important réseau de mesure de précipitation et des systèmes d'analyse atmosphérique. Dans cet article, on présente les différents types de sécheresse et la comparaison des sécheresses récentes avec par raport avec celles connues dans le passé. De plus, Météo-France utilise des modèles de suivi du bilan en eau comme le modèle Safran-Isba-Modcou (SIM) pour mieux appréhender les conséquences des déficits pluviométriques et de la demande évaporative sur l'extension et l'intensité des sécheresses. SIM permet de calculer des bilans d'eau spatialisés et en particulier un indice d'humidité et un stock de neige sur les montagnes. Ces données sont utilisées dans le suivi hydrologique en France. Les caractéristiques et quelques résultats en terme de contenu en eau du sol de deux de ces modèles sont représentés

Calibration of the Interaction Soil Biosphere Atmosphere land-surface scheme on a small tropical high-mountain basin (Cordillera Real, Bolivia)

International audienceIn a continuing effort to test the behavior of Meteo France's land-surface scheme, Interaction Soil Biosphere Atmosphere (ISBA), under a wide range of hydrometeorological conditions, the scheme was applied to a small tropical high-mountain river basin of the Cordillera Real in Bolivia. The surface scheme simulates the key hydrological processes, such as evaporation, infiltration, surface runoff, and snow and soil ice freeze-thaw processes, which are essential for accurately simulating the hydrological behavior of the river basin in this type of location. The 12.5 km 2 nonglacierized subbasin has been divided into homogeneous surface units with irregular shapes, on the basis of their elevation and soil surface characteristics. The ISBA scheme was applied to each unit and the water fluxes were transferred from one unit to another using a system dynamics modeling approach. The method was applied step by step, improving its efficiency based on several hypotheses. This special application of the ISBA scheme, combining the high-mountain conditions and the tropical seasonality is discussed

Root-zone soil moisture analysis using microwave radiometry

International audienceThe SMOS project (CNES/ESA) aims at developing a L-band interferometric radiometer able to provide global estimates of surface soil moisture (ws) with a sampling time of 2-3 d. Several studies showed that the assimilation of ws time series enable one to retrieve the root-zone water content, provided the atmospheric forcing is available from ancillary information. Two real cases of variational assimilation of ws are presented. A simple iterative optimization of the direct model is applied to the ISBA (Interactions between Soil, Biosphere, and Atmosphere) surface scheme. The next step is the direct assimilation of brightness temperatures as likely to be observed from space. A first example of soil moisture and vegetation characteristics analysis using L-band radiometric measurements and the ISBA model is presented. A field campaign was set in Southwestern France in order to validate such an approach using a long enough data-set