The Response of Salinity in Dry Season to Vertical Circulation in the Modaomen Estuary of the Pearl River, China

In recent years, salt intrusion in estuaries of the Pearl River has become a serious problem for local water supply in dry season. Water level, circulation and salinity around mouth of the Modaomen estuary in spring and neap were examined respectively through field measurements. The results indicated that mild water level process reinforced baroclinic action to cause notable circulation downstream, which was more durable in neap. And, the current in lower layer was generally faster than that in upper layer during the neap circulation. These two probably resulted in higher bottom salinity in neap than in spring within the upper mouth, which was on the contrary to the lower mouth as well as the open coastal sea nearby. The activity of observed salt wedge by tidal force within the lower mouth contributed to local salinity variation. Thus, the saline processes and distributions in the estuary mouth depended on cooperation of estuarine circulation and tidal driving in the absence of river flow and wind.

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Study on the Transport of Terrestrial Dissolved Substances in the Pearl River Estuary Using Passive Tracers

Water ◽

10.3390/w12051235 ◽

2020 ◽

Vol 12 (5) ◽

pp. 1235

Author(s):

Bo Hong ◽

Guangyu Wang ◽

Hongzhou Xu ◽

Dongxiao Wang

Keyword(s):

Water Resource Management ◽

River Flow ◽

River Estuary ◽

Pearl River Estuary ◽

Dry Season ◽

Pearl River ◽

Transport Time ◽

The Pearl River Estuary ◽

Passive Tracers ◽

The Pearl River

Highly populated river deltas are experiencing marine environment degradation resulting from the tremendous input of terrestrial dissolved substances (TeDS). The Pearl River Delta is one of the deltas with degradation of the water quality and ecological condition. The Pearl River Estuary (PRE) was investigated to reveal the fate and transport timescales of TeDS in order to provide guidance on water resource management and pollutant transport prediction. By using passive tracers in a calibrated 3D numerical model, the TeDS transports from five different outlet groups were investigated systematically. The TeDS transport time was computed by using the concept of water age, which is a measure of the time that has elapsed since the tracer was transported from the upstream boundary to the downstream concerned area. The tracer impacted area was defined by the area with tracer concentrations > 0.2 (arbitrary unit). The domains that were impacted by the tracer coming from each outlet group were identified separately. In the wet season, the impacted area was larger than in other seasons. The most prominent variations appeared in the Jiaomen–Hengmen–Hongqili (JHH) and Modaomen (MD) outlets. The hydrodynamic conditions controlled the offshore spreading of the TeDS. Assuming the TeDS were conservative, it took approximately 10–20 days for the TeDS to be transported from the head water to the entrance of the outlet. For the TeDS coming from the head water of the Humen outlet, it took approximately 40 (80) days for the TeDS to be transported out of the mouth of the Lingding Bay during the wet (dry) season. For the case of the TeDS coming from the head water of the JHH outlets, it took approximately 20 (40) days for the TeDS to be transported out of the Lingding Bay during the wet (dry) season. For the MD, Jiti and Yamen–Hutiao outlets, it usually took approximately 10 days for the TeDS to be transported from the head water to the inner shelf. The correlation coefficient between the river flow and tracer concentrations was 0.78, and between the river flow and transport time it was −0.70 at a station in the lower Lingding Bay. At the estuary mouth, the impacts of other forcing fields got stronger.

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Effect of winds and waves on salt intrusion in the Pearl River Estuary

10.5194/os-2017-73 ◽

2017 ◽

Author(s):

Wenping Gong ◽

Zhongyuan Lin ◽

Yunzhen Chen ◽

Zhaoyun Chen ◽

Heng Zhang

Keyword(s):

Water Level ◽

River Estuary ◽

Pearl River Estuary ◽

Ekman Transport ◽

Pearl River ◽

Salt Intrusion ◽

Water Mixing ◽

The Pearl River Estuary ◽

Transport Enhancement ◽

The Pearl River

Abstract. Salt intrusion in the Pearl River Estuary (PRE) is a dynamic process that is influenced by a range of factors and to date, few studies have examined the effects of winds and waves on salt intrusion in the PRE. We investigate these effects using the Coupled-Ocean-Atmosphere-Wave-Sediment Transport (COAWST) modeling system applied to the PRE. After careful validation, the model is used for a series of diagnostic simulations. It is revealed that the local wind considerably strengthens the salt intrusion by lowering the water level in the eastern part of the estuary and increasing the bottom landward flow. The remote wind increases the water mixing on the continental shelf, elevates the water level on the shelf and in the PRE, and pumps saltier shelf water into the estuary by Ekman transport. Enhancement of the salt intrusion is comparable between the remote and local winds. Waves decrease the salt intrusion by increasing the water mixing. Sensitivity analysis shows that the axial down-estuary wind, is most efficient in driving increases in salt intrusion via wind straining effect.

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Effect of winds and waves on salt intrusion in the Pearl River estuary

Ocean Science ◽

10.5194/os-14-139-2018 ◽

2018 ◽

Vol 14 (1) ◽

pp. 139-159 ◽

Cited By ~ 10

Author(s):

Wenping Gong ◽

Zhongyuan Lin ◽

Yunzhen Chen ◽

Zhaoyun Chen ◽

Heng Zhang

Keyword(s):

Water Level ◽

River Estuary ◽

Pearl River Estuary ◽

Ekman Transport ◽

Pearl River ◽

Salt Intrusion ◽

Water Mixing ◽

The Pearl River Estuary ◽

Transport Enhancement ◽

The Pearl River

Abstract. Salt intrusion in the Pearl River estuary (PRE) is a dynamic process that is influenced by a range of factors and to date, few studies have examined the effects of winds and waves on salt intrusion in the PRE. We investigate these effects using the Coupled Ocean-Atmosphere-Wave-Sediment Transport (COAWST) modeling system applied to the PRE. After careful validation, the model is used for a series of diagnostic simulations. It is revealed that the local wind considerably strengthens the salt intrusion by lowering the water level in the eastern part of the estuary and increasing the bottom landward flow. The remote wind increases the water mixing on the continental shelf, elevates the water level on the shelf and in the PRE and pumps saltier shelf water into the estuary by Ekman transport. Enhancement of the salt intrusion is comparable between the remote and local winds. Waves decrease the salt intrusion by increasing the water mixing. Sensitivity analysis shows that the axial down-estuary wind, is most efficient in driving increases in salt intrusion via wind straining effect.

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The nature, timescale, and efficiency of riverine export of terrestrial organic carbon in the (sub)tropics: Insights at the molecular level from the Pearl River and adjacent coastal sea

Earth and Planetary Science Letters ◽

10.1016/j.epsl.2021.116934 ◽

2021 ◽

Vol 565 ◽

pp. 116934

Author(s):

Bingbing Wei ◽

Gesine Mollenhauer ◽

Jens Hefter ◽

Stephanie Kusch ◽

Hendrik Grotheer ◽

...

Keyword(s):

Organic Carbon ◽

Molecular Level ◽

Pearl River ◽

Coastal Sea ◽

The Pearl River ◽

Riverine Export

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Variability and changes in Pearl River Delta water level: oceanic and atmospheric forcing perspectives

Journal of Hydrometeorology ◽

10.1175/jhm-d-21-0037.1 ◽

2021 ◽

Author(s):

Xiangbo Feng ◽

Wei Zhang ◽

Zhenglei Zhu ◽

Amulya Chevuturi ◽

Wenlong Chen

Keyword(s):

Water Level ◽

Pearl River Delta ◽

Southern China ◽

Northern South China Sea ◽

River Delta ◽

Pearl River ◽

Decadal Variations ◽

Oceanic Forcing ◽

The Pearl River

AbstractUnderstanding water level (WL) fluctuations in river deltas is of importance for managing water resources and minimizing the impacts of floods and droughts. Here, we demonstrate the competing effects of atmospheric and oceanic forcing on multi-timescale variability and changes in the Pearl River Delta (PRD) WLs in southern China, using 52 years (1961–2012) of in-situ observations at 13 hydrological stations. PRD WL presents significant seasonal to decadal variations, with large amplitudes upstream related to strong variability of southern China rainfall, and with relatively small amplitudes at the coastal stations determined by sea level (SL) fluctuations of the northern South China Sea. We find that the strengths of atmospheric and oceanic forcing in PRD are not mutually independent, leading to a distinct contrast of WL–forcing relationships at upstream and coastal stations. In the transition zone, because of counteracts of atmospheric and oceanic forcing, no robust relationships are identified between WL and either of the forcing. We further show that in the drought season of the warm ENSO and PDO epochs, the effect of atmospheric (oceanic) forcing on PRD WL is largely enhanced (weakened), due to increased southern China rainfall and negative SL anomalies. Over the observation period, WL significantly decreased at upstream stations, by up to 28–42 mm/year for flood season, contrasting with the upward trends of <4.3 mm/year at coastal stations across all seasons. Southern China rainfall explains little of the observed WL trends, whilst SL rise is mostly responsible for the WL trends at coastal stations.

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