Modeling an arrested salt-wedge estuary subjected to variable river flow

2021 ◽  
Vol 47 ◽  
pp. 101993
Author(s):  
Mariana Afonso Abade Couceiro ◽  
Carlos Augusto França Schettini ◽  
Eduardo Siegle
Keyword(s):  
River Flow ◽  
Salt Wedge

scholarly journals Hydrodynamic controls on oxygen dynamics in a riverine salt wedge estuary, the Yarra River estuary, Australia

2014 ◽  
Vol 18 (4) ◽  
pp. 1397-1411 ◽  
Author(s):  
L. C. Bruce ◽  
P. L. M. Cook ◽  
I. Teakle ◽  
M. R. Hipsey
Keyword(s):  
River Flow ◽  
River Estuary ◽  
Oxygen Depletion ◽  
Effect Of Temperature ◽  
Biogeochemical Model ◽  
Salt Wedge ◽  
Antecedent Conditions ◽  
Biogeochemical Models ◽  
Seasonal Hypoxia ◽  
Yarra River

Abstract. Oxygen depletion in coastal and estuarine waters has been increasing rapidly around the globe over the past several decades, leading to decline in water quality and ecological health. In this study we apply a numerical model to understand how salt wedge dynamics, changes in river flow and temperature together control oxygen depletion in a micro-tidal riverine estuary, the Yarra River estuary, Australia. Coupled physical–biogeochemical models have been previously applied to study how hydrodynamics impact upon seasonal hypoxia; however, their application to relatively shallow, narrow riverine estuaries with highly transient patterns of river inputs and sporadic periods of oxygen depletion has remained challenging, largely due to difficulty in accurately simulating salt wedge dynamics in morphologically complex areas. In this study we overcome this issue through application of a flexible mesh 3-D hydrodynamic–biogeochemical model in order to predict the extent of salt wedge intrusion and consequent patterns of oxygen depletion. The extent of the salt wedge responded quickly to the sporadic riverine flows, with the strength of stratification and vertical density gradients heavily influenced by morphological features corresponding to shallow points in regions of tight curvature ("horseshoe" bends). The spatiotemporal patterns of stratification led to the emergence of two "hot spots" of anoxia, the first downstream of a shallow region of tight curvature and the second downstream of a sill. Whilst these areas corresponded to regions of intense stratification, it was found that antecedent conditions related to the placement of the salt wedge played a major role in the recovery of anoxic regions following episodic high flow events. Furthermore, whilst a threshold salt wedge intrusion was a requirement for oxygen depletion, analysis of the results allowed us to quantify the effect of temperature in determining the overall severity and extent of hypoxia and anoxia. Climate warming scenarios highlighted that oxygen depletion is likely to be exacerbated through changes in flow regimes and warming temperatures; however, the increasing risk of hypoxia and anoxia can be mitigated through management of minimum flow allocations and targeted reductions in organic matter loading. A simple statistical model (R2 > 0.65) is suggested to relate riverine flow and temperature to the extent of estuary-wide anoxia.

scholarly journals Seasonal stratification and property distributions in a tropical estuary (Cochin estuary, west coast, India)

2013 ◽  
Vol 17 (1) ◽  
pp. 187-199 ◽  
Author(s):  
A. Shivaprasad ◽  
J. Vinita ◽  
C. Revichandran ◽  
P. D. Reny ◽  
M. P. Deepak ◽  
...  
Keyword(s):  
Chlorophyll A ◽  
River Discharge ◽  
River Flow ◽  
Ecological Impact ◽  
Cochin Estuary ◽  
Salt Intrusion ◽  
Salinity Field ◽  
Salt Wedge ◽  
Water Column Stability ◽  
Upwelled Water

Abstract. The intratidal, spring–neap and seasonal variations in stratification were examined in the Cochin estuary. The observations established a strong connection with the distribution of chemical and biological properties. The influence of tides and river discharge forcing in water column stability was quantified using potential energy anomaly (PEA) and stratification parameter. Partially mixed (neap) and well-mixed (spring) conditions during low river discharge (dry) period were altered in monsoon by the salt wedge intrusions. The ecological impact of salt wedge propagation on high tides bringing upwelled water to the system was evident from the bottom hypoxic, high chlorophyll a and nutrient-rich conditions. Phosphate and nitrite concentrations were higher at the bottom saline conditions but silicate and nitrate were clearly supplied by river water. However, during ebb tide this front was driven out of the estuary. The periodic advance and retreat of the salt wedge was inevitable in making the system immune from extended hypoxia/anoxia and maintaining the health of the Cochin estuary. For the seasonally varying river flow in the estuary, salt intrusion receded with increasing river flow in monsoon and rebounded with decreasing river flow in dry season. During monsoon, the intense flushing and reduction in salinity field expansion seemed to be responsible for the limited chlorophyll a levels along the surface of the Cochin estuary.

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.

scholarly journals Seasonal stratification and property distributions in a tropical estuary (Cochin estuary, west coast, India)

2012 ◽  
Vol 9 (7) ◽  
pp. 8979-9010
Author(s):  
A. Shivaprasad ◽  
J. Vinita ◽  
C. Revichandran ◽  
P. D. Reny ◽  
M. P. Deepak ◽  
...  
Keyword(s):  
Chlorophyll A ◽  
River Discharge ◽  
River Flow ◽  
Ecological Impact ◽  
Cochin Estuary ◽  
Salt Intrusion ◽  
Salinity Field ◽  
Salt Wedge ◽  
Water Column Stability ◽  
Upwelled Water

Abstract. The intratidal, spring-neap and seasonal variations in stratification were examined in Cochin estuary. The observations established a strong connection with the distribution of chemical and biological properties. The influence of tides and river discharge forcing in water column stability was quantified using potential energy anomaly (PEA) and stratification parameter. Partially mixed (neap) and well-mixed (spring) conditions during low river discharge (dry) period were altered in monsoon by the salt wedge intrusions. The ecological impact of salt wedge propagation on high tides bringing upwelled water to the system was evident from the bottom hypoxic, high chlorophyll a and nutrient-rich conditions. Phosphate and nitrite concentrations were higher at the bottom saline conditions but silicate and nitrate were clearly supplied by river water. However, during ebb tide this front was driven out of the estuary. The periodic advance and retreat of the salt wedge was inevitable in making the system immune from extended hypoxia/anoxia and maintaining the health of Cochin estuary. For the seasonally varying river flow in the estuary, salt intrusion receded with increasing river flow in monsoon and rebounded with decreasing river flow in dry season. During monsoon, the intense flushing and reduction in salinity field expansion seemed to be responsible for the limited chlorophyll a levels along the surface of Cochin estuary.

Effects of water transfers projected in the Spanish National Hydrological Plan on the ecology of the lower River Ebro (N.E. Spain) and its delta

1995 ◽  
Vol 31 (8) ◽  
pp. 79-86 ◽  
Author(s):  
Narcís Prat ◽  
Carles Ibañez
Keyword(s):  
River Flow ◽  
Management Strategies ◽  
River Mouth ◽  
Water Transfers ◽  
Salt Wedge ◽  
Water Abstraction ◽  
High Productivity ◽  
The Mean ◽  
Freshwater Inputs ◽  
Annual Discharge

This paper refers to the effects of projected water transfers, envisaged in the Spanish National Hydrological Plan, on the ecology of the lower River Ebro and its delta. Present management strategies, have resulted in highly eutrophic river water and a salt wedge which runs for more than 30 km upstream from the river mouth and its presence has been recorded during most of the year. Some parts of the delta coast are in regression as most of the inorganic sediments carried by the river are trapped in the dams. This is also leading to the sinking of the deltaic plain because subsidence and eustatic sea level rise are not compensated by new sediments. The high productivity of two bays and the coastal zone adjacent to the delta is related to influx of freshwater from irrigation channels, used in rice cultivation and the river. In the new National Hydrological Plan, a withdrawal of water upstream from the delta of 2012 hm3/year (15% of the mean annual discharge) is planned as well as the construction of 49 new reservoirs, mainly for irrigation purposes. A minimum river flow of 100 m3/s will be established by the Plan. If the plan is carried through, due to the water abstraction, forecasts based on ecological studies in the area predict: (1) increased presence of the salt wedge in the final 18 km of the river with detrimental effects on river fauna and flora; (2) serious threats to aquaculture and fisheries in the bays; (3) reduction of fish and crayfish production in the platform area; (4) further reductions in sediment and freshwater inputs to delta; (5) salinization of fields under cultivation; and (6) detrimental side effects on deltaic ecosystems.

ECOLOGY AND SUSTAINABLE DEVELOPMENT IN LOCAL BUSINESS:SIMULATION OF LOW IMPACT DEVELOPMENT IN SURAKARTA REGENCY

2018 ◽  
Vol 4 (1) ◽  
pp. 32-38
Author(s):  
Bhimo Rizky Samudro ◽  
Yogi Pasca Pratama
Keyword(s):  
Water Resources ◽  
Water Resources Management ◽  
River Flow ◽  
Low Impact Development ◽  
Development Model ◽  
Business Activity ◽  
Resources Management ◽  
Central Java ◽  
Specific Culture ◽  
Central Java Province

This paper will describe the function of water resources to support business activities in Surakarta regency, Central Java province. Surakarta is a business city in Central Java province with small business enterprises and specific culture. This city has a famous river with the name is Bengawan Solo. Bengawan Solo is a River Flow Regional (RFR) to support business activities in Surakarta regency. Concious with the function, societies and local government in Surakarta must to manage the sustainability of River Flow Regional (RFR) Bengawan Solo. It is important to manage the sustainability of business activity in Surakarta regency.   According to the condition in Surakarta regency, this paper will explain how the simulation of Low Impact Development Model in Surakarta regency. Low Impact Development is a model that can manage and evaluate sustainability of water resources in River Flow Regional (RFR). Low Impact Development can analys goals, structures, and process water resources management. The system can also evaluate results and impacts of water resources management. From this study, we hope that Low Impact Development can manage water resources in River Flow Regional (RFR) Bengawan Solo.  

Perencanaan Sistem Pengurangan Sampah Permukiman Bantaran Sungai Cidurian Kota Bandung

2019 ◽  
Vol 4 (2) ◽  
Author(s):  
Raka Maulana ◽  
Yulianti Pratama ◽  
Lina Apriyanti
Keyword(s):  
Waste Management ◽  
River Basin ◽  
River Flow ◽  
Waste Reduction ◽  
Residential Areas ◽  
Community Based ◽  
Inorganic Waste ◽  
Waste Bank ◽  
The City

<p>Some areas in the city of Bandung is an area that dilitasi by the flow of the river, to prevent the introduction of garbage into the river basin is necessary to note the waste management systems in residential areas along the river. Cidurian river has a length of 24.86 Km along the river flow. Consists of the city of Bandung and Bandung regency. Administrative regions Cidurian River past eight (8) districts, from the region in the District Kiaracondong precisely Village Babakan Babakan Sari and Surabaya populous and the most densely populated. Thus, there should be community-based waste management in the form of a reduction in resources to prevent potential entry of waste into the river basin. Planning waste reduction will be divided into two, namely the reduction of inorganic waste with waste bank then the reduction of organic waste with absorption holes biopori, and bio reactor mini determination of the reduction is determined by the results of the analysis of the sampling covers the composition and garbage, then the result of the measurement characteristics test and analysis results questionnaire.</p>

Morphotectonic Analysis of Tanjung Bungo Area Based on Geological Structure Control, Central Sumatera Basin

2020 ◽  
Author(s):  
D., A., L., A. Putri
Keyword(s):  
Natural Resources ◽  
River Flow ◽  
Measurement Data ◽  
River System ◽  
Flow Patterns ◽  
Source Rocks ◽  
Aerial Photographs ◽  
Morphological Data ◽  
Tectonic Activity ◽  
Geological Structures

Tectonic activity in an area could result in various impacts such as changes in elevation, level of slope percentages, river flow patterns and systems, and the formation of geological structures both locally and regionally, which will form a new landscape. The tectonic activity also affects the stratigraphic sequences of the area. Therefore, it is necessary to study morphotectonic or landscape forms that are influenced by active tectonic activities, both those occur recently and in the past. These geological results help provide information of the potential of natural resources in and around Tanjung Bungo area. Morphological data are based on three main aspects including morphogenesis, morphometry, and morphography. The data are collected in two ways, the first is field survey by directly observing and taking field data such as measuring geological structures, rock positions, and outcrop profiles. The second way is to interpret them through Digital Elevation Model (DEM) and aerial photographs by analyzing river flow patterns and lineament analysis. The field measurement data are processed using WinTensor, Dips, and SedLog Software. The supporting data such as Topographic Maps, Morphological Elevation Maps, Slope Maps, Flow Pattern Maps, and Lineament Maps are based on DEM data and are processed using ArcGis Software 10.6.1 and PCI Geomatica. Morphotectonically, the Tanjung Bungo area is at a moderate to high-class level of tectonic activity taken place actively resulted in several joints, faults, and folds. The formation of geological structures has affected the morphological conditions of the area as seen from the development of steep slopes, structural flow patterns such as radial, rectangular, and dendritic, as well as illustrated by rough surface relief in Tanjung Bungo area. This area has the potential for oil and gas resources as indicated by the Telisa Formation, consisting of calcareous silts rich in planktonic and benthonic fossils, which may be source rocks and its contact with the Menggala Formation which is braided river system deposits that could be good reservoirs. Further research needs to be done since current research is only an interpretation of surface data. Current natural resources being exploited in Tanjung Bungo region are coals. The coals have thicknesses of 5-7 cm and are classified as bituminous coals.

Sign in / Sign up

Export Citation Format

Share Document