Abstract: According to measured daily data of Sanjiangying station which is located at the outlet of Jiangdu water conservancy project, we analyzed the long-range change rules of typical elements such as characteristic tide level, tidal range, tide duration, and period in 1957-2019 as well as their impacts on the project operation by means of Mann-Kendall trend test, cumulative anomaly and Morlet wavelet analysis. Results demonstrated that: 1) Tide level had been increasing significantly over years, maximum tidal range did not increase significantly, and the maximum duration of rising and falling tide did not reduce significantly, but the maximum tidal range and tide duration showed opposite trend to annual trend in summer and the same trend with annual trend in dry season. 2) The characteristic tide level, tidal range and tide duration all exhibited periodic changes, with the main cycles of characteristic tide level and maximum tidal range reaching about 28 years and the main cycles of maximum rising and falling tide about 22 years. 3) According to the characteristic time length of the main cycles, the characteristic tide level, tidal range and tide duration are currently in an increasing stage and will in 2020-2021 enter a decreasing period of about 7-9 years. This study is of practical significance for the sourcing of the East Route of the South-to-North Water Diversion and the safe discharge of the Huaihe River flood. It also provides a reference for better mastering the law of tidal current movement at the end of the tidal boundary of the Yangtze River Estuary.

Key words: characteristic tide level, maximum tidal range, main cycle, Sanjiangying station, maximum duration of rising and falling tide, evolution law