Evaluating the Performance of a Daily Hydrological Model for Simulating Streamflow in Northern Algeria

In the Mediterranean basin, a region highly susceptible to climate change, understanding hydrological responses is critical for water security. This research addresses the challenge of declining water resources in Northern Algeria by evaluating the GR4J hydrological model's capacity to simulate daily streamflow in the 2500 km² Sebaou watershed. The model was calibrated and validated using observed rainfall, potential evapotranspiration, and streamflow data from four representative sub-basins. The model demonstrated strong performance, achieving Nash-Sutcliffe Efficiency (NSE) values up to 96.6% in calibration and 65.5% in validation. The resulting hydrographs accurately captured both low-flow periods and flood events, confirming the model's robustness. The findings validate the GR4J model as a reliable tool for decision support, offering significant implications for managing water resources and mitigating the risks of extreme events in a changing climate.