Saltwater Intrusion in the Changjiang Estuary

Zhu, Jianrong; Wu, Hui; Li, Lu; Qiu, Cheng

doi:10.5772/intechopen.80903

Cited by 13 publications

(22 citation statements)

References 21 publications

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“…Previous studies have investigated changes in SWI in several estuaries and deltas worldwide. River discharge variability and SLR have been found to be the main factors enhancing salinity intrusion in the Yangtze, Pearl, Changjiang, Mekong, Ganges, Brahmaputra, Meghna, and Nandu rivers (Akter et al, 2019;Bricheno & Wolf, 2018;Chen et al, 2016;He et al, 2018;Hong et al, 2020;Liu et al, 2019;Smajgl et al, 2015;Zhu et al, 2018). The results of this study confirm such general behavior.…”

Section: Discussionsupporting

confidence: 80%

Saltwater Intrusion in a Mediterranean Delta Under a Changing Climate

et al. 2021

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Coastal zones are dynamic and sensitive to changing forcing conditions related to climate variability, such as flooding and droughts, storm surges, and sea-level changes. Among coastal systems, deltas and estuaries are characterized by complex dynamics between fresh water of continental origin and salt waters (Horner-Devine et al., 2015; Valle-Levinson, 2010). Moreover, deltas are impacted by human activities and in some cases the anthropic control on the natural environment can override the climatic signal, forcing deltas toward a man-made river-dominated system (Maselli & Trincardi, 2013). One of the major problems affecting deltas and estuaries, especially during drought conditions, is the upstream extent of the mixing zone between freshwater and saltwater. This would lead to a consequent increase of the salt content in aquifers and surface waters. Saltwater intrusion (SWI) in rivers can hinder the use of surface water for irrigation or drinking purposes and can threaten the livelihood of coastal communities that rely on fresh water supplies for their livelihood. Furthermore, when there is contact between the channel bed and the underlying coastal aquifer, saltwater can intrude and lead to salinization of soils (Werner et al., 2013; White & Kaplan, 2017). A variety of factors drives SWI on different spatial and temporal scales. These can be natural (sea level, storm surges, hurricanes, climate fluctuations, and subsidence) or anthropogenic (land drainage, exploitation of coastal aquifers, reduction in freshwater discharge from hydropower production and irrigation, interbasin diversions and other hydraulic infrastructures, changes in land-use within the drainage basin and channel deepening), as well as combinations of both (White & Kaplan, 2017). Therefore, understanding the processes controlling SWI and their effects under climate change is crucial for defining proper coastal mitigation and management strategies.

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Section: Discussionsupporting

confidence: 80%

Saltwater Intrusion in a Mediterranean Delta Under a Changing Climate

et al. 2021

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“…In many estuaries, such as the CRE and northern San Francisco Bay, the salinity intrusion is greater, and MTZ is found further upstream during neap tides due to strong reduction in vertical mixing and higher stratification, which produces a large estuarine circulation (Hudson, Talke, & Jay, ; Jay & Smith, ; Schoellhamer, ; Talke et al, ). In other estuaries, such as Yangtze River and Sebou estuary, the salt intrusion is further landward in spring tides than in neap tides due to higher current velocity (Haddout et al, ; Zhu et al, ).…”

Section: Methodsmentioning

confidence: 99%

Correlation of Remotely Sensed Surface Reflectance With Forcing Variables in Six Different Estuaries

Tao

Hill

2019

JGR Oceans

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This study examines the links between estuarine dynamics and longitudinal distributions of remotely sensed reflectance in estuaries. Reflectance at 655 nm from Landsat-8 correlates with in situ measurements of surface turbidity. Images collected from 2013 to 2018 are used to investigate the spatial and temporal characteristics of reflectance distribution in six selected estuaries with different dynamics. The results show that the maximum magnitude (C max ) and location (X max ) of the reflectance are functions of two major forcing variables, the freshwater discharge and tidal stage. Salt wedge estuaries (i.e., the Fraser River, Connecticut River, and Columbia River estuary) are affected strongly by river discharge and are relatively less affected by tidal forcing. In salt wedge estuaries, the C max values along the river channel are correlated with river discharge, while the X max values generally are not. In partially mixed to strain-induced periodic stratification (SIPS) estuaries (i.e., Delaware River) and SIPS-to-well-mixed estuaries (i.e., Gironde estuary), the X max values are correlated with river discharge, but the C max values are not. SIPS-to-well-mixed estuaries (i.e., Gironde estuary) and highly time-dependent salt wedge to well-mixed estuaries (i.e., Merrimack River estuary) are affected by tidal forcing. In these estuaries, the C max values are correlated with tidal stage. The C max values tend to be lower around high tide than low tide. Overall, the results demonstrate that remote sensing observations of ocean color can be utilized to infer subsurface estuarine processes. Satellite ocean color is a potential tool to monitor river discharge and to classify estuaries. Plain Language SummaryEstuaries are dynamic environments where river freshwater mixes with seawater. The relative strength of river flow relative to flow caused by ocean tides determines how and where freshwater and seawater mix in estuaries, which in turn affects various processes important to humans, like biological productivity and diversity, harbor siltation, and transport of pollutants. It is a challenge to classify estuaries on a global scale due to limited in situ observations. However, satellite remote sensing observations are able to provide repeated, snapshot views of surface water color over large spatial scale. In this study, we examine the links between estuarine dynamics and remote sensing observations in six different estuaries using satellite imagery. The observations demonstrate that satellite-derived maximum magnitude and position in surface reflectance, which is related to particle concentration, are correlated with river flow and tidal forcing, which can be used to infer different types of estuaries. Remotely sensed observations can also be useful for inferring the subsurface water mixing and sediment resuspension in estuaries. In addition, the responses of maximum in surface particle concentration and its location to river discharge can be used for satellite-based estimation of river discharge.

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“…The Dongfengxisha salinity data are the daily mean chlorinity, values obtained from November to April in each year of 2009-2014, totally 1,113 days. In addition to the Dongfengxisha chlorinity data, other data about saltwater intrusion duration are collected from previous studies (Xu and Yuan, 1994;Shen et al, 2002;Gu et al, 2003;He et al, 2006;Zhu et al, 2010;Chen et al, 2011;Wang, 2016). On the basis of the collected data, the daily changes of chlorinity, discharge, and tidal range in dry seasons of 2009-2014 are shown in Figure 3.…”

Section: Datamentioning

confidence: 99%

“…Thus, once the daily discharge is close to or lower than 15,000 m³/s, the probability of saltwater intrusion is large. For example, in October 2006, the saltwater intrusion was three months earlier than normal because the river discharge was significantly lower than normal (Zhu et al, 2010). (2) When the saltwater intrusion duration is close to or exceeds a tidal period of 15 days (e.g., the events in 1978-1979, 1987, and 1999), the daily discharge is generally less than 10,000 m³/s.…”

Section: Characteristics Of Salt Intrusion In the Upper Sbmentioning

confidence: 99%

“…With the regulation of TGR, increasing the river discharge and reducing the duration and frequency of saltwater intrusion in dry seasons are possible, thereby increasing the guarantee rate of the freshwater supply (An et al, 2009). However, many studies have suggested different values to the critical discharge for saltwater intrusion control (Gu et al, 2003;Chen and He, 2009;Zhu et al, 2010;Chen et al, 2011;Chen et al, 2014;Wang, 2016;Xu et al, 2018). Shen et al (2002) revealed that when the river discharge is less than 25,000 m 3 /s and the tidal range of Qinglonggang station (in the North Branch (NB) of the YRE) is more than 3 m, notable saltwater intrusion can occur in the South Branch (SB).…”

Section: Introductionmentioning

confidence: 99%

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Analysis of critical river discharge for saltwater intrusion control in the upper South Branch of the Yangtze River Estuary

et al. 2020

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Saltwater intrusion in the estuary area threatens the use of freshwater resources. If river discharge increases to a critical value, then saltwater intrusion frequency and salinity level decreases. In this study, long-term river discharge and tidal range data in the Yangtze River Estuary (YRE) and salinity data obtained in the upper South Branch of the YRE were used to analyze the characteristics of different variables and the basic law of their interactions. Two methods, namely, the material analysis method and empirical models, were applied to determine the critical river discharge for saltwater intrusion control. Results are as follows: (1) the salinity might exceed the drinking water standard of China when the river discharge was less than 30,000 m³/s. Approximately 69% of salinity excessive days occurred when the river discharge was less than 15,000 m³/s; (2) the tidal range in the YRE roughly varied in sinusoidal pattern with a 15-day cycle length. Exponential relationship existed between daily salinity (chlorinity) and daily mean tidal range. Combining these two features with the cumulative frequency statistics of tidal ranges, it was showed that notable saltwater intrusion occurred when the tidal range was more than 2.7 m at Qinglonggang station. Moreover, the critical discharge was found to be slightly higher than 11,000 m³/s; (3) various of empirical models for salinity prediction could be chosen to calculate the critical discharge. The values obtained by different models were in the range of 11,000-12,000 m³/s; (4) the proposed critical discharge to reduce notable saltwater intrusion was 11,500 m³/s. After the Three Gorges Reservoir operation, the minimum river discharge into the YRE in 2008-2017 was below the critical discharge, thereby suggesting an increase in the minimum river discharge by reservoir regulation in drought periods.

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Saltwater Intrusion in the Changjiang Estuary

Cited by 13 publications

References 21 publications

Saltwater Intrusion in a Mediterranean Delta Under a Changing Climate

Saltwater Intrusion in a Mediterranean Delta Under a Changing Climate

Correlation of Remotely Sensed Surface Reflectance With Forcing Variables in Six Different Estuaries

Analysis of critical river discharge for saltwater intrusion control in the upper South Branch of the Yangtze River Estuary

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