PREMHYCE : an operational tool for low-flow forecasting ; PREMHYCE : un outil opérationnel pour la prévision des étiages

International audience ; In many countries, rivers are the primary supply of water. A number of uses (drinking water, irrigation, hydropower…) can be strongly affected by water shortages. Therefore, there is a need for the early anticipation of low-flow periods to improve water management. This is strengthened by the perspective of having more severe low flows in the context of climate change. Several French institutions have been collaborating over the last years to develop an operational tool for low-flow forecasting, called PREMHYCE. It was tested in real time on more than one hundred catchments in continental France since 2017. PREMHYCE includes five hydrological models, which are calibrated on gauged catchments and which assimilate flow observations. Low-flow forecasts can be issued up to 90 days ahead, based on Ensemble Streamflow Prediction (ESP) using historical climatic data as ensembles of future input scenarios. The performance of the forecasting tool is analysed on the 2017–2018 low flows on 38 catchments for which forecasts are available for all the models. The capacity to anticipate low-flow events shows an average anticipation of 40 days. The short-term forecast (7 days ahead) is good for most of the models. ; De nombreux usages de l'eau peuvent être fortement impactés par les pénuries d'eau (eau potable, irrigation, hydroéléctricité.). Il est donc nécessaire d'anticiper les périodes d'étiage afin d'améliorer la gestion de l'eau. Ceci est renforcé par la perspective d'étiages futurs plus sévères dans le contexte du changement climatique. Cinq institutions françaises ont développé un outil opérationnel de prévision des bas débits, PREMHYCE. Il est testé en temps réel sur une centaine de bassins versants de France métropolitaine depuis 2017. PREMHYCE comprend cinq modèles hydrologiques qui peuvent être calés sur des bassins versants jaugés et assimilent les dernières observations de débit. Les prévisions de débits sont émises jusqu'à un horizon de 90 jours selon l'approche Ensemble Streamflow ...