scholarly journals NUMERICAL MODEL FOR DENSITY CURRENTS IN ESTUARIES

1976 ◽  
Vol 1 (15) ◽  
pp. 188 ◽  
Author(s):  
Karsten Fischer
Keyword(s):  
Fresh Water ◽  
Numerical Models ◽  
Salt Water ◽  
Water Discharge ◽  
Physical Models ◽  
Stream Velocity ◽  
Density Currents ◽  
Salt Intrusion ◽  
Salt Wedge ◽  
Flow Models

In the estuarine mixing areas of salt water and fresh water the vertical stream velocity profile generally is strongly affected by the baroclinic forces, giving rise to upstream currents near the bottom. Such reverse currents occur not only in stratified estuaries, but also in estuaries of the well-mixed type |1|, and they may cause problems like strong shoaling areas, salt intrusion, or difficulties when disposing wastes or dredged material |3|. The contributions of the salinity variations to the tidal motion are comparable to the contributions from the fresh water upland discharge |1|. For well-mixed estuaries with negligible fresh water discharge, the tidal velocities and water elevations may be obtained from numerical vertically averaged models or from physical homogeneous-flow models, but for all other conditions or desired results one has to use numerical vertically discretized models or physical inhomogeneous-flow models. As numerical and physical models have different properties and deficiencies, they may be used complementarily rather than concurrently |4|, the farfield regime apparently becoming the domain of numerical models. The increased public and scientific interest in water quality problems led to the development and application of baroclinic numerical tidal models |5, 6| . The present paper is concerned with the question, how well the action of baroclinic forces can be represented by numerical techniques. As a test example, the salt wedge problems is tackled. Studies on salt wedges by means of physical models have been very sucessful |1, 7|, but mathematical approches were confined to analytical solutions for the stationary salt wedge |8 - 10| and simple geometric boundaries only. The numerical approach is free from these restrictions, giving a solution of the complete equations of motion, continuity, and convection-diffusion simultaneously.

scholarly journals Salt intrusion in the Pungue estuary, Mozambique: effect of sand banks as a natural temporary salt intrusion barrier

2008 ◽  
Vol 5 (4) ◽  
pp. 2523-2542 ◽  
Author(s):  
S. Graas ◽  
H. H. G. Savenije
Keyword(s):  
Water Supply ◽  
Water Intake ◽  
Salt Water ◽  
Water Discharge ◽  
Dry Season ◽  
Salt Water Intrusion ◽  
Salt Intrusion ◽  
Water Intrusion ◽  
Salinity Levels ◽  
Monthly Discharge

Abstract. This paper presents a salt intrusion model for the Pungue estuary with the aim to determine the minimum discharge required to prevent the salt intrusion from reaching the water intake situated 82 km from the estuary mouth. The Pungue river is shared between Zimbabwe and Mozambique and has a large variation in precipitation and runoff. The mean monthly discharge can be as low as 8 m3/s and as high as 893 m3/s. The second largest city of Mozambique, Beira, relies on the Pungue for its water supply. In the dry season it frequently occurs that the water intake has to be ceased because the salinity of the Pungue is too high. The salt intrusion model used in this paper is based on a fully analytical and predictive theory which is confronted with measurements of salt intrusion and estuary topography. The paper presents the collection of estuary characteristics and the salt water intrusion measurements that were obtained by field measurements in 1993 and 2002. Using these data the salt intrusion model has successfully been applied. During salinity intrusion measurements in the dry season of 1993 it was observed that sand banks in the middle zone of the estuary prevented the salt water from intruding further upstream, resulting in lower salinity levels upstream than the theoretical salt water intrusion model predicts. This effect occurs during ebb of neap and average tides and can reduce the salt water intrusion by 10 km. The model indicates that in a natural situation a minimum monthly discharge of 12 m3/s is required to maintain acceptable salinity levels during high water and spring tide near the water intake. The actual water discharge upstream of the water intake has to be higher, since this minimum discharge does not take into account the water abstracted for irrigation and/or urban water supply. Current water abstractions lead to salt water intrusion near the water intake at approximately 10% of the time. The model indicates that an additional water abstraction of 5 m3/s will lead to an increase in salt water reaching the intake at 10% of the time. During neap tide the sand banks act as a temporary natural salt intrusion barrier reducing the chance of salt water reaching the water intake.

Some Aspects of the Ecology of Lake Macquarie, N.S.W., with Regard to an Alleged Depletion of Fish. II. Hydrology

1959 ◽  
Vol 10 (3) ◽  
pp. 279 ◽  
Author(s):  
RS Spencer
Keyword(s):  
Sea Level ◽  
Fresh Water ◽  
Oxygen Tension ◽  
Heavy Rainfall ◽  
Salt Water ◽  
Water Discharge ◽  
Narrow Channel ◽  
Mean Sea Level ◽  
Lake Temperature ◽  
Fresh Water Discharge

Lake Macquarie is a marine-dominated drowned valley connected to the sea by a shallow narrow channel which damps tidal oscillations from 5 ft on the coast outside to about 3 in. in the like. Superimposed on the semi-diurnal tides are changes in level in response to changes both in the external daily mean sea-level and in the volume of fresh water discharge into the lake. Temperature and chlorinity cycles are closely linked. Discharge from the creeks supplies phosphate but little nitrate for the lake. Prolonged heavy rainfall in both 1955 and 1956 produced stratification of the water associated with lowered oxygen tension in the underlying salt water. There is evidence of a wind-generated circulation within the lake.

scholarly journals Investigation of Salt Intrusion Condition in the Belat Estuary

2018 ◽  
Vol 150 ◽  
pp. 03005
Author(s):  
Jacqueline Isabella Gisen ◽  
Siti Syuhaida Adnan ◽  
Ahmad Amirul Ahmad Tajudin ◽  
Tian Xian Chan
Keyword(s):  
Fresh Water ◽  
Water Intake ◽  
Sea Water ◽  
Water Discharge ◽  
Spring Tide ◽  
Salinity Distribution ◽  
Salt Intrusion ◽  
Conducting Salt ◽  
High Precipitation ◽  
Fresh Water Discharge

Awareness on salt intrusion problem is still lacking in Malaysia due to high precipitation in the region. However, the El-Nino phenomenon that occurred recently has caused extremely low fresh water discharge in the Kuantan River which allowed the sea water to intrude further into its water intake region. Consequently, the Belat River may become potential water resources alternative to build new water intake station for the water supply in the Kuantan River Basin. The aims of this study are to: 1) investigate the salinity distribution in the Belat Estuary; 2) evaluate the applicability of the 1-D analytical salt intrusion solution; 3) determine the calibration parameters in the salt intrusion model. Salt intrusion measurements was conducted during the dry season at spring tide when the fresh water discharge is the minimum. Collection of data such as hydrological data, river cross section and salinity were collected to be used in the salt intrusion analysis. The results obtained show good agreement between the simulated and observed salinity distribution in the estuary with low RMSE and high NSE values. This indicates that the model is reliable and can become an important tool for water manager in conducting salt intrusion study for this area.

scholarly journals ESTUARINE CURRENTS AND TIDAL STREAMS

2011 ◽  
Vol 1 (7) ◽  
pp. 28
Author(s):  
Roderick Agnew
Keyword(s):  
Fresh Water ◽  
River Flow ◽  
Salt Water ◽  
Three Dimensional ◽  
Vertical Plane ◽  
Water Layer ◽  
Wave Theory ◽  
Constant Density ◽  
Salt Wedge ◽  
Tidal Streams

Fresh water spreading out from the mouth of a river as it enters a salt sea may preserve its identity for a considerable distance on the surface if wind-generated waves, longshore currents and tidal streams are capable of producing only weak mixing. Fig. 1 shows the three dimensional shape of a fresh-water tongue overlying more dense salt water, derived by Takano (1954) on the assumption of constant eddy viscosity and constant density in the fresh water layer, below which the density increases according to an assumed law, making an asymptotic approach to the density of salt water. Takano's model is thus a water jet entraining salt from around and below it. Salt or brackish water may penetrate along the deep channels of an estuary in the shape of a wedge complementary to the fresh water tongue, the salt wedge retreating seawards as heavy rainfall increases the river discharge, and advancing in dry weather intervals. Tidal streams cause a regular oscillation of both fresh and braok water in flood and ebb directions but the seasonal movements of the sloping boundary between fresh and salt water may still be important in low-lying delta regions. Strong tidal streams lead to intense mixing, when neither a fresh water tongue nor a salt wedge can be distinguished, but the isohalines (salinity contours) preserve the general wedge pattern - see Figs. 3 to 6. In the upper reaches of an estuary it is possible to study the effect of the tidal motion by treating it as a simple harmonic perturbation of the uni-directional river flow. Even in the middle portion of the estuary where there is reversal of the horizontal motion, one may seek a "quasi steady" solution for the net effect (seaward movement of fresh water) while allowing for the increased turbulence due to the tidal action. At the seaward end of the estuary there is little deviation from the astronomical tidal rhythm, so the problem reduces to simple harmonic oscillations of salt water. Higher harmonics may be introduced as an extension of the simple solution. For a first approximation it is sufficient to consider flow in the longitudinal vertical plane, to assume that the pressure distribution is hydrostatic as in long wave theory, and even to neglect inertia terms when investigating net effects.

Seasonal salinity changes in the Fraser River Estuary

1976 ◽  
Vol 3 (2) ◽  
pp. 342-348 ◽  
Author(s):  
Peter R. B. Ward
Keyword(s):  
Fresh Water ◽  
Salt Water ◽  
Water Discharge ◽  
River Estuary ◽  
Surface Flow ◽  
Velocity Shear ◽  
Fraser River ◽  
Salinity Changes ◽  
Fresh Water Discharge ◽  
Fresh Surface

The Fraser Estuary in British Columbia is characterized by a salt water wedge, which underlies the fresh surface water. The stage of the tide and the fresh water discharge in the Fraser River are the two primary factors influencing the maximum intrusion of the salt water wedge.A systematic set of measurements are presented, documenting the change in the position of the tip of the salt water wedge as a function of fresh water discharge. Tidal conditions did not affect the measurements, since all measurements were made at times when the stage of the tide was the same. The tip of the salt water wedge is shown to be displaced a distance of 22 km (13.8 mi) seawards, as the fresh water discharge increased from 850 to 9000 m3/s (30 000 to 317 000 ft3/s).Vigorous surface to bottom mixing was observed during large ebb flows. The mixing was sufficiently strong to break up the wedge over a large part of the estuary. A calculation is presented showing that this was due to the existence of a strong velocity shear between the saline bottom water and the fresh water surface flow.

scholarly journals Controlling the Salt Wedge Intrusion in Shatt Al-Arab River by a Barrage

2021 ◽  
Vol 27 (12) ◽  
pp. 69-86
Author(s):  
Alaa Abdula Ali ◽  
Hayder A Al Thamiry
Keyword(s):  
Boundary Conditions ◽  
Water Discharge ◽  
Spring Tide ◽  
Water Levels ◽  
Salt Intrusion ◽  
Intrusion Prevention ◽  
Salt Wedge ◽  
Tigris River ◽  
Hydraulic Impact ◽  
Fresh Water Discharge

Shatt Al-Arab River in Al Basrah, Iraq, has recently recorded massive levels of TDS values (Total Dissolved Solids) in the water as a result of reduced fresh water discharge from sources, causing the river to become salinized due to salt wedge intrusion. Therefore, a block dam in the south reach is required to salt intrusion prevention. The main objective of this research is to simulate the hydraulic impact of a suggested barrage in Ras Al Besha on the Shatt Al-Arab River. The HEC-RAS (5.0.7) model was used to develop a one-dimensional unsteady model to gaining an understanding of the proposed barrage's influence on river behaviour. The daily discharges of the Tigris River provided as the upstream boundary conditions, while the hourly water levels of the Shatt Al-Arab River provided as the downstream boundary conditions. The model was initially run on the basis of daily discharges in Aug 2018 and March 2020 for the model's calibration and verification. Then, a model was run with a proposed barrage, Four cases of discharge were chosen which were the low and moderate discharge that equal to (20-50-100 and 250) m3/s with adopted spring tide cycle. The operation scenarios were examined under the influence of three cases of barrage gates (fully opened, 50% open and programmed opening). The results indicate that the investigated discharges will cause a significant problems in navigation depths, especially in the case of the programming of gates opening where the stages drop range between 2.01-3.3m comparing with the normal case. Furthermore, the velocity indicators show that the significant reduction in velocity upstream the barrage led to more sedimentation in the river reach.

scholarly journals TIDAL RESPONSE OF TWO-LAYER FLOW AT A RIVER MOUTH

1976 ◽  
Vol 1 (15) ◽  
pp. 182 ◽  
Author(s):  
Shizuo Yoshida ◽  
Masakazu Kashiwamura
Keyword(s):  
Fresh Water ◽  
Salt Water ◽  
River Mouth ◽  
Intermittent Flow ◽  
Mean Velocity ◽  
Tidal Period ◽  
Salt Wedge ◽  
Tidal Motion ◽  
Layer Flow ◽  
Theoretical Considerations

This paper describes various features of tidal effects on the behavior of a salt wedge and on the mechanism of mixing between the salt water and the fresh water in the vicinity of a river mouth. The studies have been performed through experiments, field observations and theoretical considerations. The condition upon which the fresh water begins to show an intermittent flow-pattern owing to an increase of the tidal action, and the criterion of a transition of the mixing type from negligible into intense, were obtained, with two dimensionless parameters X and 6. The former parameter X is given by A = A0/U0T0, in which T0 is the tidal period, A0 is the tidal amplitude of the sea level, and U0 is the temporal mean velocity of the fresh water at the river mouth. The latter parameter 9 is the so-called Keulegan number. Besides, it came evident that a tidal motion of the salt wedge couldn't be understood without a consideration of the internal wave inside the mouth, which were induced by the tide, in addition to a direct effect of the tide.

scholarly journals The modell ing study of flow in Vasishta Godavari estuary

MAUSAM ◽  
2022 ◽  
Vol 45 (1) ◽  
pp. 1-6
Author(s):  
A. D. RAO ◽  
S. CHAMARTHI ◽  
P. C. SINHA
Keyword(s):  
Fresh Water ◽  
Bay Of Bengal ◽  
Salt Water ◽  
Water Discharge ◽  
Post Monsoon ◽  
Godavari Estuary ◽  
Fresh Water Discharge

 The v as islua branch of the Godavari estuary open s into the Bay of Bengal at Antarvedi,Conditions in the estuary arccharacterized by a seasonally varying fresh water discharge and salt water intrusionfrom the Bay resul tingfrom the flow as~oc ia ted with the se.ni- diu rnal t ide. A numerica l model is applied to simulatethe flow and sali nity structures which have also been documented m the literature. The observations duringmonsoon and post-monsoon seasons arc used in a comparison with the theor etical results which are derived froma model in which turbulenceclosure scheme is used.

Identifying Physico-Chemical Laws from the Robotically Collected Data

2019 ◽  
Author(s):  
Liwei Cao ◽  
Danilo Russo ◽  
Vassilios S. Vassiliadis ◽  
Alexei Lapkin
Keyword(s):  
Experimental Data ◽  
Numerical Models ◽  
Predictor Variable ◽  
Physical Models ◽  
Training Data ◽  
Mixed Integer ◽  
Physico Chemical ◽  
Data Points ◽  
Future Work ◽  
The Relationship

<p>A mixed-integer nonlinear programming (MINLP) formulation for symbolic regression was proposed to identify physical models from noisy experimental data. The formulation was tested using numerical models and was found to be more efficient than the previous literature example with respect to the number of predictor variables and training data points. The globally optimal search was extended to identify physical models and to cope with noise in the experimental data predictor variable. The methodology was coupled with the collection of experimental data in an automated fashion, and was proven to be successful in identifying the correct physical models describing the relationship between the shear stress and shear rate for both Newtonian and non-Newtonian fluids, and simple kinetic laws of reactions. Future work will focus on addressing the limitations of the formulation presented in this work, by extending it to be able to address larger complex physical models.</p><p><br></p>

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