When does higher spatial resolution rainfall information improve streamflow simulation? An evaluation using 3620 flood events

Precipitation is the key factor controlling the high-frequency hydrological response in catchments, and streamflow simulation is thus dependent on the way rainfall is represented in a hydrological model. A characteristic that distinguishes distributed from lumped models is the ability to explicitly represent the spatial variability of precipitation. Although the literature on this topic is abundant, the results are contrasting and sometimes contradictory. This paper investigates the impact of spatial rainfall on runoff generation to better understand the conditions where higher-resolution rainfall information improves streamflow simulations. In this study, we used the rainfall reanalysis developed by Météo-France over the whole country of France at 1 km and 1 h resolution over a 10 yr period. A hydrological model was applied in the lumped mode (a single spatial unit) and in the semidistributed mode using three unit sizes of subcatchments. The model was evaluated against observed streamflow data using split-sample tests on a large set of French catchments (181) representing a variety of sizes and climate conditions. The results were analyzed by catchment classes and types of rainfall events based on the spatial variability of precipitation. The evaluation clearly showed different behaviors. The lumped model performed as well as the semidistributed model in western France, where catchments are under oceanic climate conditions with quite spatially uniform precipitation fields. By contrast, higher resolution in precipitation inputs significantly improved the simulated streamflow dynamics and accuracy in southern France (Cévennes and Mediterranean regions) for catchments in which precipitation fields were identified to be highly variable in space. In all regions, natural variability allows for contradictory examples to be found, showing that analyzing a large number of events over varied catchments is warranted

Description des caractéristiques morphologiques, climatiques et hydrologiques de 4436 bassins versants français. Guide d'utilisation de la base de données hydro-climatique

Cette note est la documentation d'un chantier entrepris depuis 2010 par l'équipe d'hydrologie du Cemagref d'Antony pour la constitution d'une vaste base de données hydro-climatique à l'échelle nationale. Réalisé en collaboration avec le SCHAPI et Météo-France, ce travail procure une ressource de qualité "clé en main" pour tous les acteurs de l'hydrologie. Près de 4500 bassins versants français sont décrits en termes de caractéristiques morphologiques, climatiques et hydrologiques. Ce travail s'est confronté à certaines difficultés et il convient ici de rappeler l'intérêt que le Cemagref porte à la refonte du référentiel hydrographique français (BD_CARTHAGE, BD_TOPO), outil indispensable pour les études hydrologiques à l'échelle nationale

The influence of conceptual model structure on model performance: A comparative study for 237 French catchments

Models with a fixed structure are widely used in hydrological studies and operational applications. For various reasons, these models do not always perform well. As an alternative, flexible modelling approaches allow the identification and refinement of the model structure as part of the modelling process. In this study, twelve different conceptual model structures from the SUPERFLEX framework are compared with the fixed model structure GR4H, using a large set of 237 French catchments and discharge-based performance metrics. The results show that, in general, the flexible approach performs better than the fixed approach. However, the flexible approach has a higher chance of inconsistent results when calibrated on two different periods. When analysing the subset of 116 catchments where the two approaches produce consistent performance over multiple time periods, their average performance relative to each other is almost equivalent. From the point of view of developing a well-performing fixed model structure, the findings favour models with parallel reservoirs and a power function to describe the reservoir outflow. In general, conceptual hydrological models perform better on larger and/or wetter catchments than on smaller and/or drier catchments. The model structures performed poorly when there were large climatic differences between the calibration and validation periods, in catchments with flashy flows, and in catchments with unexplained variations in low flow measurements.Water ManagementCivil Engineering and Geoscience