Hydrological performance of the ERA5 reanalysis for flood modeling in Tunisia with the LISFLOOD and GR4J models

Study region: This study is focused on 6 catchments in Tunisia, in North Africa, under a semi-arid climate where daily river discharge and precipitation observations are available between 1992 and 2006.Study focus: The distributed hydrological model LISFLOOD has been compared with a lumped model, GR4J, to reproduce river runoff and floods, using observed rainfall interpolated from rain gauges and from the ERA5 reanalysis.New hydrological insights for the region under study: LISFLOOD and GR4J with their default pa-rameters have little skill in Tunisia, but when calibrated, both hydrological models provide similar performance to reproduce river discharge,with a mean KGE of 0.65 for GR4J driven by observed rainfall, and 0.59 with ERA5, and similarly a mean KGE of 0.59 for LISFLOOD driven by observed rainfall and 0.48 with ERA5. All model simulations perform very similarly using either observed rainfall data from rain gauges inter-polated over the basins or ERA5 rainfall, indicating its value as an alternative to observations in data-scarce areas such as Tunisia. The development of regional databases of river discharge ob-servations in North Africa could allow the calibration of such hydrological models on a larger scale for operational flood modeling and forecasting.