scholarly journals Water and Salt Transports in the Hengsha Channel of Changjiang Estuary

2022 ◽  
Vol 10 (1) ◽  
pp. 72
Author(s):  
Rui Ma ◽  
Jianrong Zhu
Keyword(s):  
Water Transport ◽  
Neap Tide ◽  
Spring Tide ◽  
Dry Season ◽  
Changjiang Estuary ◽  
Dynamic Mechanism ◽  
Gradient Force ◽  
Residual Water ◽  
Wet Season ◽  
The North

In a multilevel bifurcated estuary, the channels between the bifurcated branches play important roles in the exchanges of water and salt. In the Changjiang Estuary, the Hengsha Channel (HC) connects the North Channel (NC) and the North Passage (NP). In this paper, based on a two-way nesting unstructured quadrilateral grid, finite-differencing, three-dimensional estuarine and coastal ocean model, the tidal and seasonal variations in the water and salt transports in the HC were simulated, and their dynamic mechanism was analyzed. The residual water and salt transports in the HC both flow southward from the NC to the NP. In wet season, the residual water transport in the HC is 677 m3/s during neap tide and 245 m3/s during spring tide, and the residual salt transport is 0. In dry season, the residual water and salt transports in the HC are 1278 m3/s and 0.38 t/s during neap tide, respectively, and 1328 m3/s and 12.61 t/s during spring tide. Affected by the northerly wind and the southeastward baroclinic gradient force, the water and salt fluxes in dry season are much larger than those in wet season. The dynamic mechanism responsible for the water transport in the HC was numerically simulated and analyzed.

scholarly journals Impacts of the Qingcaosha Reservoir on saltwater intrusion in the Changjiang Estuary

2021 ◽  
Vol 4 (1) ◽  
pp. 17-35
Author(s):  
Zhangliang Ding ◽  
Jianrong Zhu ◽  
Hanghang Lyu
Keyword(s):  
Saltwater Intrusion ◽  
Neap Tide ◽  
Spring Tide ◽  
Changjiang Estuary ◽  
Water Diversion ◽  
The Changjiang Estuary ◽  
The North ◽  
Salinity Increase ◽  
Hydrodynamic Processes ◽  
Changxing Island

The massive Qingcaosha Reservoir (QCSR) is located in the Changjiang Estuary along the northwest coast of Changxing Island. The reservoir significantly narrowed the upper reaches of the North Channel and deepened the channel near the reservoir. These topographical changes inevitably influenced hydrodynamic processes and saltwater intrusion in the estuary. A well-validated model was employed to investigate the influence of the QCSR on saltwater intrusion in the Changjiang Estuary. The model results showed that the narrowed upper reaches of the North Channel decreased the water diversion ratio and thus increased salinity in the North Channel. During the moderate tide after neap tide, the salinity decreased at the water intake of the QCSR because saltwater intrusion was obstructed at flood slack at the surface, while the salinity increase during the moderate tide after spring tide was mainly due to the intensified saltwater intrusion during spring tide. The deepening of the channel near the QCSR resulted in an increased water diversion ratio, and the salinity in the Eastern Chongming Shoal decreased by more than 0.5 psu during spring tide; however, the saltwater intrusion was enhanced due to the strengthened baroclinic force, which is proportional to the water depth. During neap tide, the salinity in the entire North Channel decreased because of a 1.4% increase in the water diversion ratio of the North Channel and the relatively weak tide.

scholarly journals TUTORIAL PENGGUNAAN SOFTWARE SMS 11.1 MODUL RMA2 UNTUK MENGANALISA POLA PERGERAKAN ARUS DI PELABUHAN BELAWAN

2017 ◽  
Vol 3 (1) ◽  
Author(s):  
Rizky Franchitika
Keyword(s):  
Surface Water ◽  
Flow Velocity ◽  
Flow Pattern ◽  
Neap Tide ◽  
Spring Tide ◽  
Dry Season ◽  
Wind Pressure ◽  
Wet Season ◽  
Water Modeling ◽  
Surface Water Modeling

ABSTRAKPelabuhan Belawan merupakan pelabuhan terbesar di Sumatera dan ketiga terbesar di Indonesia setelah Tanjung Priok dan Tanjung Perak. Pelabuhan Belawan berada didaratan semenanjung diantara Sungai Belawan dan Sungai Deli. Modelisasi pada pola arus di Pelabuhan Belawan akan menemui masalah yang sangat kompleks, karena geometri daerah pantai yang tidak beraturan adalah bagian sungai yang berhubungan langsung dengan laut. Pengaruh pasang surut terhadap sirkulasi kecepatan pola arus dan debit sungai yang masuk ke Pelabuhan Belawan sangat besar.  Salah satu model matematik untuk pemecahan masalah diatas adalah melakukan kajian dengan menggunakan software SMS (Surface-Water Modeling System) versi 11.1 pada modul RMA2, untuk mengetahui elevasi muka air pada titik di hulu dan hilir pelabuhan pada saat spring tide dan neap tide di musim basah (November) dan musim kering (Juli). Berdasarkan hasil yang didapatkan, kecepatan arus saat pasang tertinggi di musim basah adalah 0,04367 m/s - 0,4608 m/s, kecepatan arus saat pasang terendah di musim tersebut adalah berkisar antara 0,00028 m/s – 0,00287 m/s. Sedangkan kecepatan arus saat pasang tertinggi pada musim kering adalah 0,0229 m/s - 0,2744 m/s dan kecepatan arus saat pasang terendah adalah 0,0003 m/s – 0,0019 m/s. Kecepatan arus pada musim basah cenderung lebih besar daripada musim kering, disebabkan karena pengaruh pasang surut dan debit yang besar, meskipun pada simulasi angin dianggap konstan, tidak menutup kemungkinan bahwa pengaruh tekanan angin pada pelabuhan mempengaruhi kecepatan aliran.Kata Kunci : Eddy Viscosities, Pelabuhan Belawan, Pola Aliran, SMS v11.1 ABSTRACTBelawan Port is the largest port in Sumatra and the third largest in Indonesia's after the Tanjung Priok and Tanjung Perak. Belawan Port is located in mainland peninsula between Belawan and Deli river.The modeling of flow pattern in Belawan Port will encounter a very complex problem, because of the irregular geometry of coastal area which is directly connected to the sea. Tidal influence on flow circulation and the river discharge into Belawan Port is very significant. One of the mathematical models to solve the above problem is aimed to study the use of SMS software (Surface-Water Modeling System) version 11.1 on RMA2 module, to determine the water level at port including upstream and downstream during spring tide and neap tide on the wet season (November) and the dry season (July). Based on the obtained results, the flow velocity of the highest tide on the wet season is 0.04367 m/s - 0.4608 m/s, the flow velocity of the lowest tide on the dry season is between 0.00028 m/s  and 0.00287 m s. While the flow velocity of the highest tides on the dry season is 0.0229 m/s - 0.2744 m/s and low tide flow velocity is 0.0003 m/s - 0.0019 m/s. Flow velocity on the wet season tends to be larger than the dry season due to the influence of tide and large discharge. Although the wind is considered constant on this simulation, it is possible that the wind pressure against the port affects the flow velocity. Keywords: Belawan Port, Eddy Viscosities, Flow Pattern, SMS v11.1

Numerical Simulation of Tidal Waves Variation in the North Branch of the Changjiang Estuary

2013 ◽  
Vol 405-408 ◽  
pp. 1472-1475
Author(s):  
Jie Gu ◽  
Dan Qing Ma ◽  
Xin Qin ◽  
Xiao Li Wang ◽  
Ji Zhong Yang ◽  
...  
Keyword(s):  
Neap Tide ◽  
Spring Tide ◽  
Changjiang Estuary ◽  
Tidal Range ◽  
Level Curve ◽  
Middle Reach ◽  
Tidal Level ◽  
The Changjiang Estuary ◽  
The North ◽  
Set Up

A 2D numerical model about the Changjiang Estuary was set up with MIKE 21 in this study, which was well calibrated and verified with the observed tidal levels, flow velocities and flow directions, the computed results agree well with the measured data. Then the model has been applied to calculate the tidal level in the North Branch during spring and neap tide in flood season. The results show that, from the middle reach to the upper reach of the North Branch, the high tidal level is lower and lower and the low tidal level is upper and upper, so the tidal range is decreased, and tidal range during spring is greater than the one during neap. The tidal peak appearing time in the upper reach of the North Branch lags behind that of the middle reach, which is obviously during neap tide. The tidal level curve of the middle reach of the North Branch is smooth and close to the simple harmonic curve, while that of the upper reach of the North Branch deformities, the tidal level curve of ebb tide change fluctuant, much more obviously at spring tide.

Migratory Labour from North-Wester Nigeria

Africa ◽  
1957 ◽  
Vol 27 (3) ◽  
pp. 251-261 ◽  
Author(s):  
R. Mansell Prothero
Keyword(s):  
Large Scale ◽  
Source Area ◽  
Dry Season ◽  
Labour Migration ◽  
Agricultural Activity ◽  
Wet Season ◽  
The North ◽  
The People ◽  
Limited Scale ◽  
Opening Paragraph

Opening ParagraphReaders of Africa will be well aware of population migration as a characteristic feature of a continent where movement between one part and another is largely unrestricted as compared with the more settled parts of the world. There is much evidence of large-scale tribal migrations in the past, of the age-old seasonal wanderings of herders, and of recent labour migration to centres of mineral and industrial production, the last particularly in Central and South Africa. Information is more limited concerning the features of labour migration in West Africa at the present day. In general it is thought that migrants leave their home areas, after the harvest at the commencement of the dry season, to seek work elsewhere for a period of from three to six months and then return to take up farming with the commencement of the next rains. The major source area for these migrants is to the north of the tenth parallel where the wet season is concentrated into a period of about four months, thus severely restricting agricultural activity. Cultivation during the dry season is possible only on a very limited scale. There is thus a considerable period of the year when the primary economic activity of the people is not possible. It is logical that they should seek work elsewhere.

Numerical Analysis of Ebb Water Split Ratio of the South and North Branch in the Changjiang Estuary

2013 ◽  
Vol 807-809 ◽  
pp. 1624-1627
Author(s):  
Ji Zhong Yang ◽  
Jie Gu ◽  
Dan Qing Ma ◽  
Xiao Li Wang ◽  
Tian Hu ◽  
...  
Keyword(s):  
Spring Tide ◽  
Changjiang Estuary ◽  
The South ◽  
The Changjiang Estuary ◽  
Hydrodynamic Analysis ◽  
The North ◽  
Split Ratio ◽  
Calculation Results ◽  
Set Up ◽  
The One

The change of water split ratio has important impacts on the fluvial process, saltwater intrusion and navigation in estuary area. A 2D hydrodynamics numerical model of the Changjiang Estuary was set up using Delft3D-FLOW. The calculation results are consistent well with the real measured data, which indicates that the model can be used in hydrodynamic analysis. Simulation results show that the ebb water split ratio of the North Branch in the flood season is larger than that in the dry season, while the situation of the South Branch is opposite. Under the condition of different tidal types, the ebb water split ratio for the North Branch is maximum during the spring tide, and minimum during the neap tide, while the one during the middle tide takes the second place.

Occurrence of the grasshopper pest Zonocerus variegatus (L.) (Orthoptera: Pyrgomorphidae) in south-western Nigeria in relation to the wet and dry seasons

1980 ◽  
Vol 70 (4) ◽  
pp. 621-633 ◽  
Author(s):  
W. W. Page
Keyword(s):  
Dry Season ◽  
Seasonal Abundance ◽  
Secondary Peak ◽  
Rapid Decline ◽  
Arid Zones ◽  
Zonocerus Variegatus ◽  
Wet Season ◽  
The North ◽  
Dry Seasons ◽  
Peak Abundance

AbstractAn investigation into the seasonal abundance of Zonocerus variegatus (L.) around Ibadan, Nigeria, showed that hatching occurs between October and March and peak abundance is in late November. Adults occur almost throughout the year. Oviposition takes place between March and October or possibly November, with a peak in April. Eggs laid in March and April hatch in October and November after a diapause, while those laid from June onwards do not appear to enter diapause. Thus eggs laid in June and July hatch at the same time as those laid in March and April. Parasitism by the sargophagid fly Blaesoxipha filipjevi (Rod.) during March and April results in a rapid decline in adult numbers which may be followed by a secondary peak in adult numbers when nymphs, which are present at the same time and are rarely parasitised, reach adult stage. Oviposition resulting from such a peak does not produce a secondary peak in hatching as this coincides with hatching from earlier layings. The fungus Entomophthora grylli plays an important role in controlling the abundance of nymphs and adults during the dry season despite the intermittent nature of the attacks. During the wet season, the fungus is able to germinate and disperse more readily, thus keeping the numbers of the insects low. It is concluded that there is one generation of Z. variegatus a year, with a peak in population coinciding with the dry season (November-March). It is suggested from the results that the grasshopper may have originated in the semi-arid zones of the north.

scholarly journals Dynamic mechanism of an extremely severe saltwater intrusion in the Changjiang estuary in February 2014

2020 ◽  
Vol 24 (10) ◽  
pp. 5043-5056
Author(s):  
Jianrong Zhu ◽  
Xinyue Cheng ◽  
Linjiang Li ◽  
Hui Wu ◽  
Jinghua Gu ◽  
...  
Keyword(s):  
Water Level ◽  
Water Transport ◽  
River Discharge ◽  
Saltwater Intrusion ◽  
Changjiang Estuary ◽  
Maximum Speed ◽  
Residual Water ◽  
Northerly Wind ◽  
The Changjiang Estuary ◽  
Water Level Rise

Abstract. Estuarine saltwater intrusions are mainly controlled by river discharge and tides. Unexpectedly, an extremely severe saltwater intrusion event occurred in February 2014 in the Changjiang estuary under normal river discharge conditions. This intrusion cut off the freshwater input for 23 d into the Qingcaosha reservoir, which is the largest estuarine reservoir in the world, creating a severe threat to water safety in Shanghai. No similar catastrophic saltwater intrusion has occurred since records of salinity in the estuary have been kept. During the event, a persistent and strong northerly wind existed, with a maximum speed of 17.6 m s−1, lasting 9 d and coinciding with a distinct water level rise. Our study demonstrates that the extremely severe saltwater intrusion was caused by this northerly wind, which drove substantial landward net water transport to form a horizontal estuarine circulation that flowed into the northern channel and out of the southern channel. This landward net water transport overpowered the seaward-flowing river runoff and transported a large volume of highly saline water into the northern channel. The mechanisms of this severe saltwater intrusion event, including the northerly wind, residual water level rise, landward water transport and resulting horizontal circulation, etc., were systematically investigated.

Growth Strategies of Eucalyptus camaldulensis Dehnh. At Three Sites in Northern Australia

1994 ◽  
Vol 21 (5) ◽  
pp. 653 ◽  
Author(s):  
A Gibson ◽  
EP Bachelard ◽  
KT Hubick
Keyword(s):  
Gas Exchange ◽  
Shoot Growth ◽  
Eucalyptus Camaldulensis ◽  
Dry Season ◽  
Growth Strategies ◽  
Wet Season ◽  
Wind Speeds ◽  
The North ◽  
Air Temperatures ◽  
Semi Arid

The morphology and physiology of trees of Eucalyptus camaldulensis growing in the field at two monsoonal and one semi-arid location were compared. In the wet season, shoot growth at the monsoonal locations was similar and larger than that at the semi-arid location. In the dry season, new shoot growth at the more humid monsoonal location (Petford) was similar to growth in the wet season while at the less humid (Katherine) and the semi-arid (Tennant Creek) locations, shoot growth was foreshortened and the leaves had larger dry weights per unit area. In the summer wet season, leaves on both the north and south sides of the trees were maintained at or below (by up to 5�C) air temperatures throughout the day except for north facing leaves at Petford which were consistently above (by up to 3�C) air temperatures. Midday gas exchange in the dry season at both monsoonal localities was restricted to trees at the water's edge, whereas most trees, including those at drier sites, at the semi-arid location exhibited significant rates of gas exchange. The results, which are discussed in relation to environmental variables (vapour pressure deficits, wind speeds) to which the trees are exposed, and to previous results obtained in the glasshouse, indicate that the differences in shoot growth and physiology are adaptations to the environment in which the trees have evolved.

Sensitivity of tides and net water transport in an estuarine network to river discharge, network geometry and sea level rise

2020 ◽  
Author(s):  
Jinyang Wang ◽  
Huib de Swart
Keyword(s):  
Sea Level Rise ◽  
Sea Level ◽  
Water Transport ◽  
River Discharge ◽  
Yangtze Estuary ◽  
Dry Season ◽  
Sea Level Changes ◽  
Wet Season ◽  
The Yangtze Estuary ◽  
And Sea Level

<div> <div> <div> <p>Quite a number of estuaries are characterised by a complex network of branching channels, in which the water motion is primarily driven by tides and river discharge. Examples are the Berau estuary (Indonesia), the Pearl estuary (China) and the Yangtze estuary (China). Knowledge about tides are required for construction of dikes/harbours, while knowledge about net water transport is important for agriculture, fresh water supply to cities and for quantifying transport of sediment, nutrients and etc.</p> <p>In this contribution, we present a generic, weakly nonlinear 2DV estuarine network model to study tides and net water transport and to understand the dependence of their along-channel and vertical structure on geometric characteristics and sea level changes. The model will be applied to the Yangtze Estuary for different situations, such as the wet and dry season, with and without a shortcut channel and sea level rise for scenarios for the coming 50 to 100 years.</p> <p>It will be demonstrated that, for the current conditions, the model results are in good agreement with observations. Both tidal amplitude and current are weaker during the wet season than that during the dry season and the reason for these changes will be explained in terms of river-tide interactions. Effects of local changes in geometry are investigated by creation of a shortcut channel between two main channels. Results show that changes in tides are merely local, but they can be rather strong. Sea level rise (up to 2 meters) causes tides to increase, mainly as a consequence of less friction resulting from larger water depth. Net water transport turns out to be less sensitive to geometry and sea level rise compared to tides.</p> </div> </div> </div>

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