5-Minute Water Level Retrieval and Dynamic Responses to Water-Sediment Regulation from GNSS-IR in the Yellow River

Accurate and continuous high-frequency water level monitoring is essential for flood control, water resource regulation, and hydrological studies in the Yellow River. However, traditional methods are often limited in complex inland river environments with insufficient temporal resolution, poor continuity, and weak robustness. In this study, high-frequency water level changes and their dynamic responses to water-sediment regulation were estimated at Huayuankou and Xiaolangdi stations based on a sliding window, variational mode decomposition (VMD), and multi-GNSS interferometric reflectometry (GNSS-IR). The results show that high-temporal-resolution water level series with a 5-minute interval were achieved at Huayuankou and Xiaolangdi. When compared with in situ gauge measurements, the GNSS-IR estimated water level has a root mean square error (RMSE) of 0.09 and 0.14 m, and coefficient of determination (R2) values with 0.92 and 0.96, respectively. These results demonstrated strong effects by reservoir regulation in both wide-and-shallow wandering reaches and canyon-controlled reaches. Water level responses to the 2025 water-sediment regulation operation showed that Xiaolangdi responded rapidly to upstream reservoir releases, whereas Huayuankou exhibited a delayed response, with the flood peak arriving about 21 h later and attenuating during downstream propagation. The proposed method shows strong potential for high-frequency water level monitoring and dynamic response analysis from GNSS-IR in complex inland rivers.