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International audience; International collaboration between research institutes and universities is a promising way to reach consensus on hydrological model development. Although model comparison studies are very valuable for international cooperation, they do often not lead to very clear new insights regarding the relevance of the modelled processes. We hypothesise that this is partly caused by model complexity and the comparison methods used, which focus too much on a good overall performance instead of focusing on a variety of specific events. In this study, we use an approach that focuses on the evaluation of specific events and characteristics. Eight international research groups calibrated their hourly model on the Ourthe catchment in Belgium and carried out a validation in time for the Ourthe catchment and a validation in space for nested and neighbouring catchments. The same protocol was followed for each model and an ensemble of best-performing parameter sets was selected. Although the models showed similar performances based on general metrics (i.e. the Nash-Sutcliffe efficiency), clear differences could be observed for specific events. We analysed the hydrographs of these specific events and conducted three types of statistical analyses on the entire time series: cumulative discharges, empirical extreme value distribution of the peak flows and flow duration curves for low flows. The results illustrate the relevance of including a very quick flow reservoir preceding the root zone storage to model peaks during low flows and including a slow reservoir in parallel with the fast reservoir to model the recession for the studied catchments. This intercomparison enhanced the understanding of the hydrological functioning of the catchment, in particular for low flows, and enabled to identify present knowledge gaps for other parts of the hydrograph. Above all, it helped to evaluate each model against a set of alternative models.

International audience; International collaboration between institutes and universities is a promising way to reach consensus on hydrological model development. Education, experience and expert knowledge of the hydrological community have resulted in the development of a great variety of model concepts, calibration methods and analysis techniques. Although comparison studies are very valuable for international cooperation, they do often not lead to very clear new insights regarding the relevance of the modelled processes.We hypothesise that this is partly caused by model complexity and the used comparison methods, which focus on a good overall performance instead of focusing on specific events. We propose an approach that focuses on the evaluation of specific events. Eight international research groups calibrated their model for the Ourthe catchment in Belgium (1607 km2) and carried out a validation in time for the Ourthe (i.e. on two different periods, one of them on a blind mode for the modellers) and a validation in space for nested and neighbouring catchments of the Meuse in a completely blind mode. For each model, the same protocol was followed and an ensemble of best performing parameter sets was selected. Signatures were first used to assess model performances in the different catchments during validation. Comparison of the models was then followed by evaluation of selected events, which include: low flows, high flows and the transition from low to high flows. While the models show rather similar performances based on general metrics (i.e. Nash-Sutcliffe Efficiency), clear differences can be observed for specific events. While most models are able to simulate high flows well, large differences are observed during low flows and in the ability to capture the first peaks after drier months. The transferability of model parameters to neighbouring and nested catchments is assessed as an additional measure in the model evaluation. This suggested approach helps to select, among competing model alternatives, the most suitable model for a specific purpose.

International audience

Dans le but de mettre en évidence l’impact des modifications paysagères et la mécanisation des plages sur la faune carcinologique semi-terrestre, une campagne de terrain a été effectuée en février 2004 au niveau de deux sites de la province d’Alicante (Sud-Est de l’Espagne). La plage de Santa Pola, partiellement épargnée de l’accès des machines de nettoyage et celle d’El Pinet où la mécanisation est très intense. Les résultats obtenus ont montré que, malgré une faible densité des arthropodes récoltés, la biodiversité de la plage de Santa Pola est plus élevée que celle de la plage d’EL Pinet caractérisée par la quasi absence des amphipodes semi-terrestres. Seule l’espèce Tylos europaeus est commune dans les 2 sites. Ce résultat s’expliquerait par l’impact de l’activité anthropique, essentiellement le nettoyage mécanique des plages étant donné la proximité des 2 sites et la concomitance de la campagne d’échantillonnage qui excluent l’impact des facteurs climatiques et biotiques. A survey has been conducted in February 2004 on two sites located at the Alicante province (South East of Spain). It aims the evaluation of the impact induced by the modification of the landscapes as well as the mechanical cleaning of beaches on some hemi-terrestrial arthropods diversity and density. The first site, a small beach at Santa Pola is characterised by a rocky barrier with minor anthropic pressures while, the second one, a larger beach situated at El Pinet with a large touristic frequentation and a high level periodic mechanic cleaning. Despite a weak density of collected arthropods, this study showed that the biodiversity of the Santa Pola beach is more important than the one observed at El Pinet. This latter is characterised by a quasi absence of hemiterrestrial amphipods. This result could be explained by the human activities that affect the El Pinet beach while Santa Pola one is prevented from it.The concomitant sampling period as well as the vicinity of the 2 sites exclude the impact of climate conditions and biotic factors. Only Tylos europaeus is commun in the 2 localities. Published Hemi-terrestrial crustaceans Human disturbance Mechanical cleaning