Long-Term Water-Level Forecasting and Real-Time Correction Models in the Tidal Reach of the Yangtze River

Abstract

In this research, considering the importance and complexity of the water-level forecast in tidal reach, a case study was done in the tidal reach of the Yangtze River. Through the analysis of the characteristics of water-level variations, tidal harmonic analysis was introduced into tidal reach, which was commonly applied in oceanic water-level forecast. An automatic partial tide selection and optimization pattern was used to calibrate harmonic constants, long-term water-level forecast models were developed for Yanglin, Xuliujing, Tianshenggang, and Jiangyin stage stations, and then the long-term forecast models were used to hindcast historical water-level events at the aforementioned stations. Most of the results were highly accurate, but there were also some occasional significant errors, which could be attributed to the effects of upstream runoff and downstream storm surge. Based on these findings, response functions of water-level forecast error to the variation of upstream runoff and the variation of storm surge were developed, which were used in the real-time correction of the simulation results obtained from the long-term forecast model. The forecast accuracy was evidently improved. These models have already been used in water-level forecast in the tidal reach of the Yangtze River for the construction of two large bridges, and they also have the potential to contribute to water-level forecast in similar tidal reaches of other rivers.