Salt wedge

Ibanez C, Saldana J, Prat N (1999) A model to determine the advective circulation in a three layer, salt wedge estuary Application to the Ebre River estuary. Estuar Coast Shelf Sci 48 271-279... 

Sierra JP, Sanchez-Arcilla A, Figueras PA, Del Rio JG, Rassmussen EK, Mosso C (2004) Effects of discharge reductions on salt wedge dynamics of the Ebro River. River Res Appl 20 61-77... 

Groundwater level shift (ex-, infiltration), salt (wedge) intrusions near estuaries... 

Cantwell, M.G., J.W. King, R.M. Burgess, and P.G. Appleby. 2007. Reconstruction of contaminant trends in a salt wedge estuary with sediment cores dated using a multiple proxy approach. Mar. Environ, Res. 64 225-246. 

Figure 3.7 The general categories of estuarine circulation identified as Type A, well-mixed estuaries, where there is minimal vertical stratification in salinity Type B, partially mixed estuaries, where the vertical mixing is inhibited to some degree Type C, highly stratified with lower freshwater discharge than the salt wedge system and Type D, salt wedge estuary and many fjords. (Modified from Bowden, 1980.)...

Figure 3.9 Stratification-circulation diagrams used to describe a spectrum of circulation and geomorphometric types of estuaries that can be defined by stratification. Estuarine types are as follows Type 1 estuaries are those without upstream flow requiring tidal transport for salt balance Type 2 estuaries are partially mixed (e.g., Marrows of the Mersey (NM) (UK), James River (J) (USA), Columbia River estuary (C) (USA) Type 3 estuaries are representative of fjords [e.g., Siver Bay (S), Strait of Juan de Fuca (JF) (USA)] and Type 4 estuaries indicative of salt wedge estuaries [e.g., Mississippi River (M) (USA)]. The basic classification parameters are as follows the stratification is defined by SS/Sq where SS is the difference in the salinity between surface and bottom water and So is the mean-depth salinity, both averaged over a tidal cycle and Us/Uf, where U is the surface velocity (averaged over a tidal cycle) and Uf is the vertically averaged net outflow. The subdivisions a and b represent values where SS/Sq <0.1 and SS/Sq >0.1, respectively subscripts h and 1 refer to high and low river flow. The curved line at the top represents the limit of surface freshwater outflow. (From Hansen and Rattray, 1966, as modified by Jay et al., 2000, with permission.)...

Hansen and Rattray (1966) introduced a general classification scheme for estuaries based on stratification/circulation that is divided into the following four estuarine types Type 1 estuaries well-mixed estuaries with mean flow in the seaward direction and the salt balance being maintained by diffusive processes—via tidal transport Type 2 estuaries partially mixed estuaries where the net flow reverses at depth and the salt flux is maintained by both diffusive and advective processes Type 3 estuaries these estuaries include fjords with two distinct layers and advection accounting for the majority of the salt flux Type 4 estuaries these are salt-wedge estuaries where freshwater flows out over a stable more dense bottom layer. 

Figure 6.7 Illustration of particle trapping as it relates to resuspension in the mud reach and the location of the salt wedge over a tidal cycle. (Modified from Geyer, 1993.)...

Salt-wedge estuaries river-dominated estuaries where the freshwater flow is high enough to create a sharp wedge-like stratification in the water column. 

Type 4 estuary salt-wedge estuaries where freshwater flow is out over stable denser bottom layer. 

Thompson, P.A. (1998) Spatial and temporal patterns of factors influencing phytoplankton in a salt wedge estuary, the Swan River, Western Australia. Estuaries 21, 801-817. 

During the low-flow periods and under the influence of the eastern winds, seawater can penetrate into the deep delta channels [8]. The maximum length of seawater intrusion recorded during recent decades was 16.5 km in the Sulina branch [29] and 14.0 km in the Ochakovskiy branch [8]. As a rule, seawater penetrates into the delta branches in the form of salt wedge . 

The northern portion of Chesapeake Bay was studied. This upper section of the bay can be classified as a classic salt-wedge type estuary (15). The humic materials used in this study were extracted from several cores of sediments. Two one-meter cores gravity corer. The cores of sediments were then divided into sections and squeezed under nitrogen to remove most of the interstitial water. The squeezed sediments were then dried, weighed and washed with distilled water. The sediments were then washed with 0.5N KCl to remove iron hydroxides, carbonates and exchangeable cations from the clays. Some of the fulvic acids are lost in this acid wash procedure. The humic materials were then extracted from the remaining solids by a O.IN NaOH solution. 

Estuaries are usually classified in terms of the characteristics of their circulation, broadly speaking, as salt wedge, and partially mixed. Estuaries differ in many other ways—for example, in the nature and amount of sediment they transport and the composition and diversity of the biological communities they support. No two estuaries, no matter how close in affinity they may be according to hydrologic classification, are ever identical. 

Figure 9.16 Basic circulation and salinity distribution in salt wedge, partially mixed, well-mixed and fjord-type estuaries. Numbers and shading show salinity values [34]...

When well-developed vertical stratification is established, an estuary is sometimes said to have a salt wedge, in reference to the underlying saltwater layer whose thickness tapers from the depth of the downstream saltwater body to zero in the upstream freshwater direction (Fig. 2.9). Interestingly, near the bottom of a salt wedge, water velocity can be upstream This can be demonstrated by considering the mass balance of salt upstream advection of salt in the saline layer is required to balance the outflow of salt that becomes mixed into the seaward-flowing freshwater layer via upward diffusion from the salt wedge. 

FIGURE 2.9 (a) An idealized estuary in cross section. In this well-stratified estuary, a distinct salt wedge extends upstream beneath fresher water at the surface. The freshwater/saltwater interface moves upriver at high tide and seaward at low tide. Data from Silver Bay, Alaska, USA show (b) a steep average salinity gradient (salinity is shown in parts per thousand) and (c) upstream advection of saltwater at depth. More strongly mixed estuaries exhibit weaker vertical stratification. Data from Rattray (1967). 

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