PREMHYCE: an operational tool for low-flow forecasting

In many countries, rivers are the primary supply of water. A number of uses (drinking water, irrigation, hydropower horizontal ellipsis ) 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.