scholarly journals Comment on "Seasonal behaviour of tidal damping and residual water level in the Yangtze River estuary: Identifying the critical position and river discharge for amximum tidal damping "

2019 ◽  
Author(s):  
Anonymous
Keyword(s):  
River Discharge ◽  
Yangtze River ◽  
River Estuary ◽  
Yangtze River Estuary ◽  
Residual Water ◽  
The Yangtze River ◽  
Critical Position ◽  
The Yangtze River Estuary ◽  
Seasonal Behaviour ◽  
Residual Water Level

scholarly journals Seasonal behaviour of tidal damping and residual water level slope in the Yangtze River estuary: identifying the critical position and river discharge for maximum tidal damping

2019 ◽  
Vol 23 (6) ◽  
pp. 2779-2794 ◽  
Author(s):  
Huayang Cai ◽  
Hubert H. G. Savenije ◽  
Erwan Garel ◽  
Xianyi Zhang ◽  
Leicheng Guo ◽  
...  
Keyword(s):  
Water Level ◽  
River Discharge ◽  
Yangtze River ◽  
River Estuary ◽  
Yangtze River Estuary ◽  
Residual Water ◽  
The Yangtze River ◽  
The Yangtze River Estuary ◽  
Seasonal Behaviour ◽  
Residual Water Level

Abstract. As a tide propagates into the estuary, river discharge affects tidal damping, primarily via a friction term, attenuating tidal motion by increasing the quadratic velocity in the numerator, while reducing the effective friction by increasing the water depth in the denominator. For the first time, we demonstrate a third effect of river discharge that may lead to the weakening of the channel convergence (i.e. landward reduction of channel width and/or depth). In this study, monthly averaged tidal water levels (2003–2014) at six gauging stations along the Yangtze River estuary are used to understand the seasonal behaviour of tidal damping and residual water level slope. Observations show that there is a critical value of river discharge, beyond which the tidal damping is reduced with increasing river discharge. This phenomenon is clearly observed in the upstream part of the Yangtze River estuary (between the Maanshan and Wuhu reaches), which suggests an important cumulative effect of residual water level on tide–river dynamics. To understand the underlying mechanism, an analytical model has been used to quantify the seasonal behaviour of tide–river dynamics and the corresponding residual water level slope under various external forcing conditions. It is shown that a critical position along the estuary is where there is maximum tidal damping (approximately corresponding to a maximum residual water level slope), upstream of which tidal damping is reduced in the landward direction. Moreover, contrary to the common assumption that larger river discharge leads to heavier damping, we demonstrate that beyond a critical value tidal damping is slightly reduced with increasing river discharge, owing to the cumulative effect of the residual water level on the effective friction and channel convergence. Our contribution describes the seasonal patterns of tide–river dynamics in detail, which will, hopefully, enhance our understanding of the nonlinear tide–river interplay and guide effective and sustainable water management in the Yangtze River estuary and other estuaries with substantial freshwater discharge.

scholarly journals Seasonal behaviour of tidal damping and residual water level slope in the Yangtze River estuary: identifying the critical position and river discharge for maximum tidal damping

2018 ◽  
Author(s):  
Huayang Cai ◽  
Hubert H. G. Savenije ◽  
Erwan Garel ◽  
Xianyi Zhang ◽  
Leicheng Guo ◽  
...  
Keyword(s):  
Water Level ◽  
River Discharge ◽  
Yangtze River ◽  
River Estuary ◽  
Yangtze River Estuary ◽  
Residual Water ◽  
The Yangtze River ◽  
The Yangtze River Estuary ◽  
Seasonal Behaviour ◽  
Residual Water Level

Abstract. As a tide propagates into the estuary, river discharge affects tidal damping primarily through a friction term, attenuating tidal motion by increasing the quadratic velocity in the numerator, while reducing the effective friction by increasing the water depth in the denominator. For the first time, we also demonstrate a third effect of river discharge that may lead to the weakening of the channel convergence (i.e., landward reduction of channel width and/or depth). In this study, monthly averaged tidal water levels (2003–2014) at six gauging stations along the Yangtze River estuary were used to understand the seasonal behaviour of tidal damping and residual water level slope. Observations show that there is a critical value of river discharge, beyond which the tidal damping is reduced with increasing river discharge. This phenomenon is clearly observed in the upstream part of the Yangtze River estuary (between the Maanshan and Wuhu reach), which suggests an important cumulative effect of residual water level on tide-river dynamics. To understand the underlying mechanism, an analytical model has been used to quantify the seasonal behaviour of tide-river dynamics and the corresponding residual water level slope under various external forcing conditions. It was shown that a critical position along the estuary is where there is maximum tidal damping (approximately corresponding to a maximum residual water level slope), upstream of which tidal damping is reduced in the landward direction. Moreover, contrary to the common assumption that larger river discharge leads to heavier damping, we demonstrate that beyond a critical value tidal damping is slightly reduced with increasing river discharge, owing to the cumulative effect of residual water level on the effective friction and channel convergence. Our contribution describes the seasonal patterns of tide-river dynamics in detail, which will, hopefully, enhance our understanding of the nonlinear tide-river interplay and guide effective and sustainable water management in the Yangtze River estuary and other estuaries with substantial freshwater discharge.

River discharge contribution to sea-level rise in the Yangtze River Estuary, China

2017 ◽  
Vol 134 ◽  
pp. 63-75 ◽  
Author(s):  
Cuiping Kuang ◽  
Wei Chen ◽  
Jie Gu ◽  
Tsung-Chow Su ◽  
Hongling Song ◽  
...  
Keyword(s):  
Sea Level Rise ◽  
Sea Level ◽  
River Discharge ◽  
Yangtze River ◽  
River Estuary ◽  
Yangtze River Estuary ◽  
The Yangtze River ◽  
The Yangtze River Estuary

scholarly journals Influence of River Discharge on the Transport of the Saltwater Group from the North Branch in the Yangtze River Estuary

2020 ◽  
Vol 17 (24) ◽  
pp. 9156
Author(s):  
Zhi Xu ◽  
Jing Ma ◽  
Hao Wang ◽  
Jianshi Zhao
Keyword(s):  
River Discharge ◽  
Yangtze River ◽  
Quantitative Research ◽  
River Estuary ◽  
Yangtze River Estuary ◽  
The Yangtze River ◽  
The Core ◽  
The North ◽  
The Yangtze River Estuary ◽  
Group Migration

The Yangtze River Estuary (YRE) is the largest estuary in China. Recently, due to the increase of extent and frequency, saltwater intrusion has received more and more attention. In this paper, with the adoption of hydrodynamic and salinity transport mode, quantitative research of the influence of river discharge to the North Branch (NB) of the Yangtze River on the saltwater group migration law is conducted. Tide and salinity data are used to validate the model effectively. In different paths, the changes in flow and the movement of the saltwater group are similar. The saltwater group starts to move downward from the sixth day. In the staged downward movement, the larger the runoff volume, the further the distance of the core of the saltwater group, and converges to around 90 km gradually. At different flow rates, the relationship between the average location of each waterway saltwater group core tide cycle and time is consistent with the Gompertz model, and its parameters had a nonlinear relationship with the flow rate. A function is constructed to calculate the length and time of the saltwater group migration. As the flow rate increases, the faster the core of the saltwater group reaches the entrance. The downwards movement takes 3–8 days. Quantitative research on the influence of the saltwater spilling from NB to the three major reservoirs in the South Branch (SB)is conducted. The simulation results are consistent with the function calculation. River discharge has a direct impact on saltwater transport and diffusion in the YRE.

scholarly journals Saltwater Intrusion Function and Preliminary Application in the Yangtze River Estuary, China

2019 ◽  
Vol 16 (1) ◽  
pp. 118 ◽  
Author(s):  
Zhi Xu ◽  
Jing Ma ◽  
Yajie Hu
Keyword(s):  
River Discharge ◽  
Saltwater Intrusion ◽  
Yangtze River ◽  
Large Scale ◽  
Salt Water ◽  
River Estuary ◽  
Reference Value ◽  
Yangtze River Estuary ◽  
The Yangtze River ◽  
The Yangtze River Estuary

More attention has been paid to saltwater-intrusion-related problems in recent years. In this research study, a saltwater intrusion function in the Yangtze River Estuary (YRE) was constructed based on the theory of the interactions between energy accumulation and impedance. A MIKE21 model was used to simulate the hydrodynamics of the YRE. Then, through the analysis of the relationships between the river discharge conditions, tidal ranges, and saltwater intrusion, it was determined that, under certain river discharge conditions, the tidal ranges and salinity levels at the stations in the southern branch (SB) of the YRE conformed to S-shaped curve characteristics. Also, the tidal ranges and salinity excessive area rate (SEAR) displayed similar characteristics. Furthermore, the river discharge conditions were also found to match the S-curve characteristics between the two aforementioned relationship features. Therefore, the saltwater intrusion function of the YRE was constructed based on the previously mentioned development rules. Also, the applied quantification methods were elaborated, and the values of the parameters were determined. As a result, the critical river discharge (more than 10,000 m3/s) was obtained, which could withstand large-scale saltwater intrusions. When the river discharge was greater than 30,000 m3/s, the area was considered to be basically without salt water intrusions, and the estuarine ecology was in an optimal state. The saltwater intrusion losses from 2005 to 2015 are also calculated. These findings have important reference value for water dispatching of the YRE in the dry season.

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