Journal of Tropical Oceanography ›› 2023, Vol. 42 ›› Issue (4): 77-90.doi: 10.11978/2022160CSTR: 32234.14.2022160

• Marine Hydrology • Previous Articles     Next Articles

Spatial-temporal variations in tide-river dynamics of typical transverse channel in the Pearl River channel networks——Taking the ‘Nansha-Nanhua’ transverse channel as an example

QIU Xiufang1,2,3,4(), LI Bo1,2,3,4, WANG Bozhi1,2,3,4, GU Junhao1,2,3,4, WANG Jisi1,2,3,4, SU Yanan1,2,3,4, CAI Huayang1,2,3,4()   

  1. 1. Institute of Estuarine and Coastal Research, School of Ocean Engineering and Technology, Sun Yat-sen University, Guangzhou 510275, China
    2. State and Local Joint Engineering Laboratory of Estuarine Hydraulic Technology, Guangzhou 510275, China
    3. Guangdong Provincial Engineering Research Center of Coasts, Islands and Reefs, Guangzhou 510275, China
    4. Southern Laboratory of Ocean Science and Engineering (Zhuhai), Zhuhai 519000, China
  • Received:2022-07-20 Revised:2022-08-23 Online:2023-07-10 Published:2022-08-30
  • Supported by:
    National Natural Science Foundation of China(51979296); National Natural Science Foundation of China(52279080); Science and Technology Plan Project of Guangzhou, China(202002030452)

Abstract:

The transverse channel plays an indispensable role in the maintenance of dynamic equilibrium of the Pearl River channel networks. Therefore, studying the spatial-temporal variations in river-tide dynamics has important implications for flood control, water supply and navigation in the Guangdong-Hong Kong-Macao Greater Bay Area. Based on the high and low water level series observed at tidal gauging stations along the typical transverse channel (i.e., ‘Nansha-Nanhua’ reach) and the daily averaged river discharge series observed at Makou and Sanshui hydrological stations from 1966 to 2016, the double cumulative curve method and the T_TIDE tidal harmonic analysis model were adopted to quantify the spatial-temporal variations in tide-river dynamics in the transverse channel. The results show that the tide-river dynamics in the transverse channel changed considerably in 1993, the annual mean absolute value of the tidal amplitude gradient and the annual mean value of the residual water level slope decrease by 25% and 38%, respectively; the tidal dynamics in the Nansha station at the estuary mouth weakens (the amplitudes of M2 and K1 constituent decreased by 0.01 m and 0.02 m on average, respectively), while the tidal dynamics at other stations enhanced after 1993. Meanwhile, the tidal damping effect slightly increased in the central reach, but decreased in both the upstream and downstream reaches, in which the alteration is more significant in summer than that in winter. This suggests that the dependence of the tidal amplitude gradients of two main constituents on the river discharge is significantly decreased. The phenomenon mentioned above can be mainly attributed to the nonlinear cumulative influence of natural changes and human activities. On the one hand, the combined influences of intensive reclamation and waterway regulation near the estuary mouth lead the rapid extension of the estuary mouth, which can result in an increase in the friction for tidal wave propagation. On the other hand, the intensive sand excavation in the upper reaches of the transverse channel results in a substantial deepening of the river bed, reducing the friction for tidal wave propagation. In addition, the seasonal dynamics can be primarily attributed to the seasonal variations in river discharge and sea water level. Moreover, it is expected that the fundamental regime of river flow debouching and tidal discharge storage of the transverse channel system change, leading to a reduced flood risk together with an enhanced tidal hydrodynamics.

Key words: river discharge, tidal amplitude gradient, residual water level slope, tide-river interaction