Gilles Drogue

The applicability of a parsimonious model for local and regional prediction of runoff

Abstract The Hydrological Recursive Model (HRM), a conceptual rainfall-runoff model, was applied for local and regional simulation of hourly discharges in the transnational Alzette River basin (Luxembourg-France-Belgium). The model was calibrated for a range of various sub-basins with a view to analysing its ability to reproduce the variability of basin responses during flood generation. The regionalization of the model parameters was obtained by fitting simultaneously the runoff series of calibration sub-basins after their spatial discretization in lithological contrasting isochronal zones. The runoff simulations of the model agreed well with the recorded runoff series. Significant correlations with some basin characteristics and, noticeably, the permeability of geological formations, could be found for two of the four free model parameters. The goodness of fit for runoff predictions using the derived regional parameter set was generally satisfactory, particularly for the statistical characteristics of streamflow. A more physically-based modelling approach, or at least an explicit treatment of quick surface runoff, is expected to give better results for high peak discharge.

How can a few streamflow measurements help to predict daily hydrographs at almost ungauged sites

Abstract Available data from nearby gauging stations can provide a great source of hydrometric information that is potentially transferable to an ungauged site. Furthermore, streamflow measurements may even be available for the ungauged site. This paper explores the potential of four distance-based regionalization methods to simulate daily hydrographs at almost ungauged pollution-control sites. Two methods use only the hydrological information provided by neighbouring catchments; the other two are new regionalization methods parameterized with a limited number of streamflow data available at the site of interest. Based on a network of 149 streamgauges and 21 pollution-control sites located in the Upper Rhine-Meuse area, the comparative assessment demonstrates the benefit of making available point streamflow measurements at the location of interest for improving quantitative streamflow prediction. The advantage is moderate for the prediction of flow types (stormflow, recession flow, baseflow) and pulse shape (duration of rising limb and falling limb). Editor Z.W. Kundzewicz; Associate editor A. Viglione

International assessment of future low flow regimes and their impact on three water related sectors in the Meuse basin – a collaborative approach

ABSTRACT There is a wide recognition of the watershed scale as the right scale for global water management, notably in the context of the water framework directive. Hence, it often refers to international management and therefore to various pre-existing regional management tools, models or even objectives. In this study, we aim at describing the collaborative assessment of climate changes effect on low-flow regime and the consequences on three water-related sectors: drinking water production, agriculture and electricity production. The paper highlights the choices that were made during the study that involved scientific teams, managers and stakeholders from the four main countries of the Meuse Basin. It shows that the methodological choices were operational and aimed at preserving existing methods and knowledge within each country. They led to hydrological scenarios comparable to the main available ensemble approaches and to methodologies well accepted within the concerned countries. The results of the project highlight and quantify the water scarcity that the three sectors will have to face by the end of the century mainly regarding the electricity production. They also show that common allocation rules are necessary to manage water demand during future low-flow periods.

Détection du changement régional par rééchantillonnage de séries chronologiques : application aux précipitations dans l’espace rhéno-mosan

Regional change detection through a boostrap resampling procedure: application to rainfall time series in the upper Rhine-Meuse area A boostrap resampling method has been applied to rainfall data (point times series and field values) to get the empirical distribution function of the number of significant tests. By preserving the cross-correlation structure of the network/field, this distribution shows the field significance. The region of interest is a mesoscale area with a semi-oceanic climate (90 000 km2, North-Eastern France and surrounding areas). Over the last decades winter westerly rainfall (seasonal amounts and maximum daily intensities) were subject to abrupt and gradual changes having a regional coherence. Topographical conditions are likely to modulate the spatial patterns and magnitude of changes. Statistical analysis of seasonal rainfall amounts downscaled on the French part of the Meuse basin for the end of the century yields a local and regional significant only for summer rainfall. Definitely, field significance and type of change vary according to the rainfall characteristics and their spatial persistency. Regional analysis of change in climate time series should be based on “early bird” sites or grid points poorly correlated in space and whose climate information is maximizing the signal to noise ratio.