Researchers at #UTokyo_IIS have developed a real-time data assimilation system that substantially improves streamflow and flood forecasting accuracy across Japan. This new data assimilation system outperforms Japan’s current early warning system. Compared with the previous early warning system, the new data assimilation system yields improved forecasts for 80% of the major river reaches in Japan and enables reliable flood prediction across more than 60% of the observation stations in Japan.