Journal of East China Normal University(Natural Sc ›› 2012, Vol. 2012 ›› Issue (3): 111-119.

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Analysis of tidal characteristics of the tide gauges in the Changjiang Estuary

YANG Zheng-dong 1, ZHU Jian-rong 2, WANG Biao 2, LIN Tang-yu 2   

  1. 1. Hydrologic Station of Chongming County of Shanghai, Shanghai 202150, China;
    2. State Key Laboratory of Estuarine and Coastal Research, East China Normal University, Shanghai 200062, China
  • Received:2011-06-01 Revised:2011-09-01 Online:2012-05-25 Published:2012-05-22

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Abstract: Based on the measured water levels at Hengsha, Majiagang, Baozhen and Yonglongsha tide gauges in 2009, the tidal temporal and spatial variations, tidal constituents, tidal form and distortion at these gauges in the Changjiang Estuary were analyzed. There exist tidal daily inequalities that mainly occur during high tide levels, and are more significant during neap tides than spring tides in March and September while are more significant during spring tides than neap tides in June and December. The monthly maximum and minimum tidal ranges in each month at the tide gauges were given out statistically. The tidal range in the estuary varies monthly with two peaks: the maximum tidal range reaches the maximum values in March and September, and reaches the minimum values in June and December. The minimum tidal range reaches the maximum values in June and December, and reaches the minimum values in March and September. The tidal range in the South Branch reduced toward upstream due to the river discharge and friction. The tidal range at Yonglongsha tidal gauge is the largest among the 4 tidal gauges because the North Branch has small river discharge division ratio and funnel shape bathymetry. The tide is mainly composed by the 4 semi-diurnal tidal constituent (M 2、S 2、N 2、K 2), 4 diurnal tidal constituent (K 1、O 1、P 1、Q 1) and 3 shallow water tidal constituent (M 4、MS 4、M 6). The semi-diurnal tidal constituents M 2 and S 2 are the predominant ones, and the shallow water tidal constituents M 4 and MS 4 are apparent due to the shallow water in the estuary. The tidal form number in the South Branch is larger than 0.25, indicating where the tide is an irregular semi-diurnal tide type there, and is smaller than 0.25 in the North Branch, indicating where the tide is a regular semi-diurnal tide type. The tidal distortion coefficients in the 4 tidal gauges are all larger than 0.1, indicating that the tide at the tide gauges has significant distortion in the Changjiang Estuary, especially at Yonglongsha in the North Branch with tidal distortion coefficient 0.173.

Key words: the Changjiang Estuary, tidal level, tidal range, tidal constituents, tidal characteristics

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