scholarly journals A Numerical Study of Salt Fluxes in Delaware Bay Estuary

2013 ◽  
Vol 43 (8) ◽  
pp. 1572-1588 ◽  
Author(s):  
María Aristizábal ◽  
Robert Chant
Keyword(s):  
River Discharge ◽  
Neap Tide ◽  
Numerical Study ◽  
Spring Tide ◽  
Delaware Bay ◽  
Salt Flux ◽  
Exchange Flow ◽  
Regional Ocean Modeling System ◽  
Salinity Field ◽  
Estuarine Exchange

Abstract The results of a numerical study of Delaware Bay using the Regional Ocean Modeling System (ROMS) are presented. The simulations are run over a range of steady river inputs and used M2 and S2 tidal components to capture the spring–neap variability. Results provide a description of the spatial and temporal structure of the estuarine exchange flow and the salinity field, as well the along-channel salt flux in the estuary. The along-channel salt flux is decomposed into an advective term associated with the river flow, a steady shear dispersion Fe associated with the estuarine exchange flow, and a tidal oscillatory salt flux Ft. Time series of Fe and Ft show that both are larger during neap tide than during spring. This time variability of Ft, which is contrary to existing scalings, is caused by the lateral flows that bring velocity and salinity out of quadrature and the stronger stratification during neap tide, which causes Ft to be enhanced relative to spring tide. A fit for the salt intrusion length L with river discharge Q for a number of isohalines is performed. The functional dependences of L with Q are significantly weaker than Q−1/3 scaling. It is concluded that the response of the salt field with river discharge is due to the dependence of Fe and Ft with Q and the relative importance of Ft to the total upstream salt flux: as river discharge increases, Fe becomes the dominant mechanism. Once Fe dominates, the salt field stiffens because of a reduction of the vertical eddy viscosity with increasing Q.

Salt Flux in a Partially Mixed Estuary with Varying River Discharge over a Spring-Neap Tide Cycle

2011 ◽  
Vol 137 ◽  
pp. 237-242 ◽  
Author(s):  
Li Rong Yuan ◽  
Rong Li Chen ◽  
Cheng Lu
Keyword(s):  
River Discharge ◽  
Neap Tide ◽  
Measurement Data ◽  
Salt Flux ◽  
Vertical Shear ◽  
Exchange Flow ◽  
Modaomen Estuary ◽  
Shear Dispersion ◽  
Order Of Magnitude ◽  
Estuarine Exchange

The mechanisms driving the salt flux in the Modaomen estuary were investigated using measurements from along-channel shipboard surveys over a spring-neap tide cycle. During the investigation, river discharge was controlled to increase sharply and then decrease gently. The measurement data were analyzed with composition method. The results show that exchange flow varied significantly over the spring–neap cycle, being weakest during middle tides and strongest during neap tides. It could be concluded that sub-tidal vertical shear dispersion, resulting from the estuarine exchange flow, is the dominant mechanism driving the salt flux since the salt flux resulting from vertical shear dispersion varies in amplitude by over an order of magnitude, which is close to two times as large as the variation of advective salt flux.

scholarly journals Circulation and salt balance in the São Francisco river Estuary (NE/Brazil)

RBRH ◽  
2017 ◽  
Vol 22 (0) ◽  
Author(s):  
Geórgenes Cavalcante ◽  
Luiz Bruner de Miranda ◽  
Paulo Ricardo Petter Medeiros
Keyword(s):  
River Discharge ◽  
Neap Tide ◽  
Spring Tide ◽  
River Estuary ◽  
Salt Transport ◽  
Salt Flux ◽  
Sao Francisco River ◽  
Tidal Cycles ◽  
São Francisco River ◽  
And Diffusion

ABSTRACT In order to evaluate how river discharge and tidal currents forcing influence the circulation and salt transport within the São Francisco River-Estuary, a two 25 hour surveys campaigns and along-channel profiles were performed in the estuary main channel (18/19 and 25/26 February 2014). The current intensity showed higher asymmetry between flood (v<0) and ebb (v>0) currents in spring tide (-0.6 and 1.1 m/s), as compared to neap tide (-0.4 and 1.0 m/s), which was attributed to the intense buoyancy energy enhanced by the stronger discharge in spring. Overall, salinity presented high stratified conditions and varied between 0.0<S<36.6, and 0.5<S<36.1 from surface to bottom, during spring and neap, respectively. Although river discharge reduced from spring to neap tide partially mixed-highly stratified conditions (type 2b) remained in both periods, with advection and diffusion contributing with 34% and 66% to the net upstream salt flux in spring, respectively, and 56% and 44% in neap tide, respectively, which was attributed to the balance of tidal and baroclinic forcing and river discharge. The dominant downstream advective salt transport in both spring (12.5 kg.m-1s-1) and neap (15.2 kg.m-1s-1) tidal cycles suggests that there is little salt accumulation inside the São Francisco estuary.

scholarly journals Comparison of empirical models with intensively observed data for prediction salt intrusion in the Sumjin River estuary, Korea

2009 ◽  
Vol 6 (2) ◽  
pp. 1879-1905 ◽  
Author(s):  
D. C. Shaha ◽  
Y.-K. Cho
Keyword(s):  
River Discharge ◽  
Neap Tide ◽  
Spring Tide ◽  
River Estuary ◽  
High Water ◽  
Empirical Models ◽  
Length Scale ◽  
Salt Intrusion ◽  
Salinity Data ◽  
Comparative Results

Abstract. Intensive measurements of salt intrusion in the Sumjin River estuary were taken at high and low waters during both spring and neap tides in each season from August 2004 to April 2007. The estuary demonstrated partially- and well-mixed characteristics during the spring tide and stratified condition during the neap tide. The salt intrusion at high water varied from about 13.39 km in summer 2005 to 25.62 km in autumn 2006. The salt intrusion depended primarily on the freshwater discharges rather than those of spring-neap tidal oscillations. Analysis of three years of observed salinity data indicated that the salt intrusion length scale in the Sumjin River estuary was proportional to the river discharge to the −1/5 power. Five empirical models were applied to the Sumjin River estuary to explore the most suitable as an easy-to-use tool for prediction of the salt intrusion length as functions of the geometry, river discharge and tide. Comparative results showed that the Nguyen and Savenije (2006) model developed under both partially- and well-mixed estuaries yielded the most satisfactory results of all the models studied for computing the salt intrusion length in the Sumjin River estuary. Our study suggests that the model can generate reasonable results for stratified conditions also.

NUTRIENT RETENTION IN THE BIOREMEDIATION ZONE OF A SANDY BEACH

1995 ◽  
Vol 1995 (1) ◽  
pp. 896-897
Author(s):  
Brian A. Wrenn ◽  
Makram T. Suidan ◽  
Kevin L. Strohmeier ◽  
B. Loye Eberhardt ◽  
Gregory J. Wilson ◽  
...  
Keyword(s):  
Tidal Cycle ◽  
Sandy Beach ◽  
Neap Tide ◽  
High Tide ◽  
Spring Tide ◽  
Nutrient Retention ◽  
Delaware Bay ◽  
Low Energy ◽  
Washout Rate ◽  
Tracer Study

ABSTRACT A tracer study was conducted on a low-energy beach in Delaware Bay to determine how the nutrient washout rate is affected by the tidal cycle. When tracer was applied during spring tide, it was reduced to background levels following a single high tide; but when it was applied during neap tide, tracer persisted in the bioremediation zone for a much longer time. The washout rate was found to be related to the extent of water coverage during high tide.

scholarly journals Total Exchange Flow, Entrainment, and Diffusive Salt Flux in Estuaries

2017 ◽  
Vol 47 (5) ◽  
pp. 1205-1220 ◽  
Author(s):  
Tao Wang ◽  
W. Rockwell Geyer ◽  
Parker MacCready
Keyword(s):  
Temporal Variation ◽  
Cross Sections ◽  
Salt Content ◽  
Spring Tide ◽  
Salt Transport ◽  
Salt Flux ◽  
Exchange Flow ◽  
Important Relationship ◽  
Numerical Mixing ◽  
Total Exchange

AbstractThe linkage among total exchange flow, entrainment, and diffusive salt flux in estuaries is derived analytically using salinity coordinates, revealing the simple but important relationship between total exchange flow and mixing. Mixing is defined and quantified in this paper as the dissipation of salinity variance. The method uses the conservation of volume and salt to quantify and distinguish the diahaline transport of volume (i.e., entrainment) and diahaline diffusive salt flux. A numerical model of the Hudson estuary is used as an example of the application of the method in a realistic estuary with a persistent but temporally variable exchange flow. A notable finding of this analysis is that the total exchange flow and diahaline salt flux are out of phase with respect to the spring–neap cycle. Total exchange flow reaches its maximum near minimum neap tide, but diahaline salt transport reaches its maximum during the maximum spring tide. This phase shift explains the strong temporal variation of stratification and estuarine salt content through the spring–neap cycle. In addition to quantifying temporal variation, the method reveals the spatial variation of total exchange flow, entrainment, and diffusive salt flux through the estuary. For instance, the analysis of the Hudson estuary indicates that diffusive salt flux is intensified in the wider cross sections. The method also provides a simple means of quantifying numerical mixing in ocean models because it provides an estimate of the total dissipation of salinity variance, which is the sum of mixing due to the turbulence closure and numerical mixing.

The Salt Flux in the Pearl River Delta, China

2012 ◽  
Author(s):  
Yuliang Zhu ◽  
Xiaoyan Wei ◽  
Chencheng Xu
Keyword(s):  
Pearl River Delta ◽  
Saltwater Intrusion ◽  
Neap Tide ◽  
Spring Tide ◽  
River Delta ◽  
Salt Flux ◽  
Pearl River ◽  
Tidal Period ◽  
The Pearl River Delta ◽  
The Pearl River

The increase of saltwater intrusion in recent years in the Pearl River Delta, has threatened the freshwater supply in the surrounding regions, especially the cities of Zhongshan, Zhuhai, Guangzhou in Guangdong Province and Macau. A numerical modeling system using nested grids was developed to simulate the salinity distribution in the Pearl River delta, and then to investigate the salt transport process and calculate the salt flux for each outlet in the Pearl River estuary. The model forcing functions consist of tidal elevations along the open boundaries and freshwater inflows from the major tributaries in the Pearl River system. The model simulation results are in qualitative agreement with the available field data. The salt flux of the Pearl River delta during the spring tide in dry season is up to 19.5×106ton/ tidal period, while the salt flux during neap tide is only 5.1×106ton/ tidal period, 26.18% of that during the spring tide. The salt flux in Dahu and Guanchong stations are the highest among the stations of the eight outlets, indicating that Humen and Yamen are the most important entries for saltwater intrusion in the Pearl River delta. The most important reason is that the ratio of stream flow to tide flow is different for each outlet. The ratios at Humen and Yamen are the smallest among the eight outlets (<1 for each month), while the ratio at Modaomen is the biggest (>1 for each month), which leads to the lowest salt flux at Modaomen. Salinity distribution in different time periods shows that saltwater intrusion during the spring tide is much more serious than neap tide, and water in many cities during this time period will be unavailable for drinking, irrigation or for ecological purpose.

scholarly journals Calculating Estuarine Exchange Flow Using Isohaline Coordinates*

2011 ◽  
Vol 41 (6) ◽  
pp. 1116-1124 ◽  
Author(s):  
Parker MacCready
Keyword(s):  
Residence Time ◽  
River Estuary ◽  
Columbia River ◽  
Time Dependent ◽  
Salt Flux ◽  
Exchange Flow ◽  
Exact Formulation ◽  
Volume Flux ◽  
Columbia River Estuary ◽  
Estuarine Exchange

Abstract A method for calculating subtidal estuarine exchange flow using an isohaline framework is described, and the results are compared with those of the more commonly used Eulerian method of salt flux decomposition. Concepts are explored using a realistic numerical simulation of the Columbia River estuary. The isohaline method is found to be advantageous because it intrinsically highlights the salinity classes in which subtidal volume flux occurs. The resulting expressions give rise to an exact formulation of the time-dependent Knudsen relation and may be used in calculation of the saltwater residence time. The volume flux of the landward transport, which can be calculated precisely using the isohaline framework, is of particular importance for problems in which the saltwater residence time is critical.

scholarly journals Fluvial modulation of hydrodynamics and salt transport in a highly stratified estuary

2010 ◽  
Vol 58 (2) ◽  
pp. 165-175 ◽  
Author(s):  
Carla de Abreu D'Aquino ◽  
Jurandir Pereira Filho ◽  
Carlos Augusto França Schettini
Keyword(s):  
Time Series ◽  
Water Level ◽  
River Discharge ◽  
Spring Tide ◽  
River Estuary ◽  
Salt Transport ◽  
Salt Flux ◽  
Rain Event ◽  
Stratified Estuary ◽  
A Site

An oceanographic campaign was conducted in the Araranguá river estuary during the period from May 11th to 13th of 2006 in order to produce a first hydrographic characterization of this system. The campaign was carried out during the spring tide period, and coincidentally after an intense rain event in the region which produced a peak in river discharge. Water level, currents and salinity time series were recorded hourly during a 50-hour period, at a site nearly 7 km upstream from the estuarine mouth. Two longitudinal distributions of salinity along the estuary were also recorded. The hydrographic data time-series were used to compute the advective salt flux in order to investigate the changes in the transport terms as a function of the change in discharge. The results showed that the estuarine structure was strongly modulated by the river discharge. The drop in water level of about 0.5 m during the first 24 hours was directly related to the ebb phase of the river flood. The water column was highly stratified throughout the period, therefore the stratification increased during the last 24 hours. The currents were stronger, ebbing and uni-directional at the beginning and became weaker and bidirectional as the water level went down, assuming a tidal pattern. The total salt transport in the first 25 hours was of -13.6 kg.m-1.s-1 (seawards), decreasing to 3 Kg.m-1.s-1 during the last 25 hours (landwards). It was also noticeable that the pH in the estuary, recorded together with the salinity, was around 5, showing that the water quality in the estuary is affected by the coal mining activity in the hydrographic basin.

scholarly journals Asymmetric Estuarine Responses to Changes in River Forcing: A Consequence of Nonlinear Salt Flux

2015 ◽  
Vol 45 (11) ◽  
pp. 2836-2847 ◽  
Author(s):  
Shih-Nan Chen
Keyword(s):  
Response Time ◽  
Linear Theory ◽  
Nonlinear Effect ◽  
Nonlinear Function ◽  
Power Laws ◽  
Salt Transport ◽  
Salt Flux ◽  
Exchange Flow ◽  
Salinity Field ◽  
The Asymmetry

AbstractA linear theory for estuarine adjustment to river forcing as put forth by MacCready is extended to allow for quantification of nonlinear salt flux induced by gravitational exchange flow. It has been shown that, under a steplike change of river forcing, the estuarine responses are asymmetric, with the salinity field adjusting faster during the rising discharge. The asymmetry arises because the up-estuary salt flux due to exchange flow is a nonlinear function of estuarine length ∝ L−3. During the rising discharge, the estuary is longer, and the salt flux is comparatively less sensitive to the length variations. As a result, the up-estuary salt transport cannot keep pace with the rate of discharge changes, leading to a larger net salt flux and thus a shorter response time. A simple theory accounting for the nonlinear effect is then applied to Hudson-like systems and shown to capture the asymmetric response. The asymmetry is generalizable to other estuarine regimes where up-estuary salt fluxes are expressed as nonlinear power laws.

scholarly journals The Response of Turbidity Maximum to Peak River Discharge in a Macrotidal Estuary

Water ◽  
2021 ◽  
Vol 13 (1) ◽  
pp. 106
Author(s):  
Yuhan Yan ◽  
Dehai Song ◽  
Xianwen Bao ◽  
Nan Wang
Keyword(s):  
River Discharge ◽  
Recovery Time ◽  
Morphological Evolution ◽  
Spring Tide ◽  
River Estuary ◽  
Sediment Concentration ◽  
Ocean Model ◽  
Turbidity Maximum ◽  
Sediment Supply ◽  
Three Dimensional Model

The Ou River, a medium-sized river in the southeastern China, is examined to study the estuarine turbidity maximum (ETM) response to rapidly varied river discharge, i.e., peak river discharge (PRD). This study analyzes the difference in ETM and sediment transport mechanisms between low-discharge and PRD during neap and spring tides by using the Finite-Volume Community Ocean Model. The three-dimensional model is validated by in-situ measurements from 23 April to 22 May 2007. In the Ou River Estuary (ORE), ETM is generally induced by the convergence between river runoff and density-driven flow. The position of ETM for neap and spring tides is similar, but the suspended sediment concentration during spring tide is stronger than that during neap tide. The sediment source of ETM is mainly derived from the resuspension of the seabed. PRD, compared with low-discharge, can dilute the ETM, but cause more sediment to be resuspended from the seabed. The ETM is more seaward during PRD. After PRD, the larger the peak discharge, the longer the recovery time will be. Moreover, the river sediment supply helps shorten ETM recovery time. Mechanisms for this ETM during a PRD can contribute to studies of morphological evolution and pollutant flushing.

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