scholarly journals Variation in turbidity with precipitation and flow in a regulated river system – river Göta Älv, SW Sweden

2013 ◽  
Vol 17 (7) ◽  
pp. 2529-2542 ◽  
Author(s):  
G. Göransson ◽  
M. Larson ◽  
D. Bendz
Keyword(s):  
Sediment Transport ◽  
Suspended Sediment ◽  
Fresh Water ◽  
Surface Runoff ◽  
River System ◽  
Regulated River ◽  
Suspended Sediment Transport ◽  
Simple Relationship ◽  
Main River ◽  
Lake Vänern

Abstract. The turbidity variation in time and space is investigated in the downstream stretch of the river Göta Älv in Sweden. The river is heavily regulated and carries the discharge from the largest fresh water lake in Sweden, Lake Vänern, to the outflow point in Göteborg Harbour on the Swedish west coast. The river is an important waterway and serves as a fresh-water supply for 700 000 users. Turbidity is utilised as a water quality indicator to ensure sufficient quality of the intake water to the treatment plant. The overall objective of the study was to investigate the influence of rainfall, surface runoff, and river water flow on the temporal and spatial variability of the turbidity in the regulated river system by employing statistical analysis of an extensive data set. A six year long time series of daily mean values on precipitation, discharge, and turbidity from six stations along the river were examined primarily through linear correlation and regression analysis, combined with nonparametric tests and analysis of variance. The analyses were performed on annual, monthly, and daily bases, establishing temporal patterns and dependences, including; seasonal changes, impacts from extreme events, influences from tributaries, and the spatial variation along the river. The results showed that there is no simple relationship between discharge, precipitation, and turbidity, mainly due to the complexity of the runoff process, the regulation of the river, and the effects of Lake Vänern and its large catchment area. For the river Göta Älv, significant, positive correlations between turbidity, discharge, and precipitation could only be found during periods with high flow combined with heavy rainfall. Local precipitation does not seem to have any significant impact on the discharge in the main river, which is primarily governed by precipitation at catchment scale. The discharge from Lake Vänern determines the base level for the turbidity in the river, whereas local surface runoff and tributary discharge induced by rainfall govern the temporal variability in turbidity. Autocorrelation analysis indicates a temporal persistence in turbidity of about 10 days. The results also show that erosion along the main river, from the river bed and banks, is not a dominant contributor to the suspended sediment transport in the river under normal conditions. Further studies on the correlation between turbidity and suspended sediment transport and its relation to erosion processes are suggested.

scholarly journals Variation in turbidity with precipitation and flow in a regulated river system – River Göta Älv, SW Sweden

2013 ◽  
Vol 10 (1) ◽  
pp. 255-293
Author(s):  
G. Göransson ◽  
M. Larson ◽  
D. Bendz
Keyword(s):  
Sediment Transport ◽  
Suspended Sediment ◽  
Fresh Water ◽  
Surface Runoff ◽  
River System ◽  
Regulated River ◽  
Suspended Sediment Transport ◽  
Simple Relationship ◽  
Main River ◽  
Lake Vänern

Abstract. The turbidity variation in time and space is investigated in the downstream stretch of the river Göta Älv in Sweden. The river is heavily regulated and carries the discharge from the largest fresh water lake in Sweden, lake Vänern, to the outflow point in Göteborg Harbour on the Swedish west coast. The river is an important waterway and serves as fresh-water supply for 700 000 users. Turbidity is utilised as an indicator to ensure sufficient quality of the intake water to the treatment plant. The overall objective of the study was to investigate the influence of rainfall, surface runoff, and river water flow on the temporal and spatial variability of the turbidity in the regulated river system by employing statistical analysis of an extensive data set. Six-year long time series of daily mean values on precipitation, discharge, and turbidity from six stations along the river were examined primarily through linear correlation and regression analysis, combined with nonparametric tests and analysis of variance. The analyses were performed on annual, monthly, and daily basis, establishing temporal patterns and dependences, including seasonal changes, impacts from extreme events, influences from tributaries, and the spatial variation along the river. The results showed that there is no simple relationship between discharge, precipitation, and turbidity, mainly due to the complexity of the runoff process, the regulation of the river, and the effects of lake Vänern and its large catchment area. For the river Göta Älv, significant, positive correlations between turbidity, discharge, and precipitation could only be found during periods with high flow combined with heavy rainfall. Local precipitation does not seem to have any significant impact on the discharge in the main river, which is primarily governed by the precipitation at catchment scale. The discharge from the lake Vänern determines the base level for the turbidity in the river, whereas local surface runoff and tributary discharge induced by rainfall govern the temporal variability in turbidity. Autocorrelation analysis indicates a temporal persistence in turbidity of about 10 days. The results also show that erosion in the main river, from the river bed and banks, is not a dominant contributor to the suspended sediment transport in the river. Further studies on the correlation between turbidity and suspended sediment transport and in relation to erosion processes are suggested.

scholarly journals Appraising the Impact of Naraj Barrage on Sedimentation of Chilika Lagoon; the Soft Computing Model for Prediction

2020 ◽  
pp. 31-41
Author(s):  
Siba Prasad Mishra ◽  
Ananta Charan Ojha
Keyword(s):  
Sediment Transport ◽  
Suspended Sediment ◽  
Learning Algorithm ◽  
River System ◽  
Suspended Sediment Transport ◽  
Chilika Lagoon ◽  
Surrounding Environment ◽  
Ensemble Machine Learning ◽  
The Impact ◽  
Total Sediment

Estimation of suspended sediment transport in a catchment area is very important to manage water resources, construction of dam and barrage, as well as to protect the surrounding environment. The daily monsoon sediment and flow were observed physically and quantity of total sediment input by the two major rivers of the south Mahanadi deltaic rivers to Lagoon Chilika were calculated during pre Naraj barrage (FY 2000 to 2003) and post Naraj Barrage period (FY’s 2004, 2012, 2013) establishing an observatory in the rivers the Daya and the Bhargovi.[b] The non-linear complex relationship between quantity of suspended sediment transport and volume of river-discharge inflicts challenge to the estimation process. In this paper, two southern-most distributaries, the Daya and the Bhargovi of the Mahanadi River System which flow into Chilika lagoon are studied. Random Forest, an ensemble machine learning algorithm is used to estimate the transport of sediment by these two distributaries using predictive modeling. Predicted figures based on the gathered data from these distributaries during pre-barrage period 2000-2003 have been compared with the observed data gathered in post-barrage years 2004, 2012 and 2013. Comparative data suggests that the construction of Naraj barrage has significantly reduced the concentration of sediment influx into Chilika lagoon while controlling the discharge through effective barrage management.

2D and 3D CFD Investigations of Seabed Shear Stresses Around Subsea Pipelines

2013 ◽  
Author(s):  
Wenwen Shen ◽  
Terry Griffiths ◽  
Mengmeng Xu ◽  
Jeremy Leggoe
Keyword(s):  
Sediment Transport ◽  
Suspended Sediment ◽  
Interaction Model ◽  
Suspended Sediment Transport ◽  
Shear Stresses ◽  
Parametric Function ◽  
Ample Evidence ◽  
North West ◽  
Wide Range ◽  
Subsea Pipelines

For well over a decade it has been widely recognised that existing models and tools for subsea pipeline stability design fail to account for the fact that seabed soils tend to become mobile well before the onset of pipeline instability. Despite ample evidence obtained from both laboratory and field observations that sediment mobility has a key role to play in understanding pipeline/soil interaction, no models have been presented previously which account for the tripartite interaction between the fluid and the pipe, the fluid and the soil, and the pipe and the soil. There are numerous well developed and widely used theories available to model pipe-fluid and pipe-soil interactions. A challenge lies in the way to develop a satisfactory fluid-soil interaction algorithm that has the potential for broad implementation under both ambient and extreme sea conditions due to the complexity of flow in the vicinity of a seabed pipeline or cable. A widely used relationship by Shields [1] links the bedload and suspended sediment transport to the seabed shear stresses. This paper presents details of computational fluid dynamics (CFD) research which has been undertaken to investigate the variation of seabed shear stresses around subsea pipelines as a parametric function of pipeline spanning/embedment, trench configuration and wave/current properties using the commercial RANS-based software ANSYS Fluent. The modelling work has been undertaken for a wide range of seabed geometries, including cases in 3D to evaluate the effects of finite span length, span depth and flow attack angle on shear stresses. These seabed shear stresses have been analysed and used as the basis for predicting sediment transport within the Pipe-Soil-Fluid (PSF) Interaction Model [2] in determining the suspended sediment concentration and the advection velocity in the vicinity of pipelines. The model has significant potential to be of use to operators who struggle with conventional stabilisation techniques for the pipelines, such as those which cross Australia’s North West Shelf, where shallow water depths, highly variable calcareous soils and extreme metocean conditions driven by frequent tropical cyclones result in the requirement for expensive and logistically challenging secondary stabilisation measures.

Suspended sediment transport in a highly erodible catchment: The River Isábena (Southern Pyrenees)

Geomorphology ◽  
2009 ◽  
Vol 109 (3-4) ◽  
pp. 210-221 ◽  
Author(s):  
J.A. López-Tarazón ◽  
R.J. Batalla ◽  
D. Vericat ◽  
T. Francke
Keyword(s):  
Sediment Transport ◽  
Suspended Sediment ◽  
Suspended Sediment Transport ◽  
River Isábena
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