Monitoring Significant Terrestrial Water Storage Increase From the “237” Extreme Flood Around the Haihe River Basin Using GRACE-FO and Precipitation Reconstruction

In recent years, frequent flood disasters have posed significant threats to human life and property. From July 28 to August 1, 2023, a basin-wide extreme flood occurred in the Haihe River Basin (“23·7” flood). The Gravity Recovery and Climate Experiment (GRACE) satellite can effectively detect the spatiotemporal characteristics of terrestrial water storage anomalies (TWSA) and has been widely used in flood disaster monitoring. However, flood events usually occur on a sub-monthly scale. This study first utilizes near-real-time precipitation data to illustrate the evolution of the “23·7” extreme flood. We then reconstruct daily TWSA to improve the issues of coarse temporal resolution and data latency and further calculate wetness index (WI) to explore its flood warning. Additionally, we analyze soil moisture storage anomalies (SMSA) to provide a comprehensive understanding of flood mechanisms. The study also compares the 2023 floods to a severe flood event in 2021. Results indicate that reconstructed daily TWSA increases by 143.43 mm in 6 days during the “23·7” flood, highlighting the high sensitivity of our approach to extreme events. Moreover, compared to daily runoff data, the WI consistently exceeds warning thresholds 2-3 days in advance, demonstrating the flood warning capability. The flood event 2021 is characterized by long duration and large precipitation extremes, whereas the 2023 flood affects a wider area. This study provides a reference for using daily TWSA to monitor short-term flood events and evaluate the flood warning potential of WI, aiming to enhance near-real-time flood monitoring and support flood prevention and damage mitigation efforts.