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Variation in turbidity with precipitation and flow in a regulated river system - river Gota Alv, SW Sweden

Göransson, Gunnel LU ; Larson, Magnus LU and Bendz, D. (2013) In Hydrology and Earth System Sciences 17(7). p.2529-2542
Abstract
The turbidity variation in time and space is investigated in the downstream stretch of the river Gota Alv in Sweden. The river is heavily regulated and carries the discharge from the largest fresh water lake in Sweden, Lake Vanern, to the outflow point in Goteborg 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... (More)
The turbidity variation in time and space is investigated in the downstream stretch of the river Gota Alv in Sweden. The river is heavily regulated and carries the discharge from the largest fresh water lake in Sweden, Lake Vanern, to the outflow point in Goteborg 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 Vanern and its large catchment area. For the river Gota Alv, 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 Vanern 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. (Less)
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publishing date
type
Contribution to journal
publication status
published
subject
in
Hydrology and Earth System Sciences
volume
17
issue
7
pages
2529 - 2542
publisher
European Geophysical Society
external identifiers
  • wos:000322376000011
  • scopus:84880130280
ISSN
1607-7938
DOI
10.5194/hess-17-2529-2013
language
English
LU publication?
yes
id
0f876f71-d91c-41b3-ba6e-ae1eba4231d5 (old id 4050258)
date added to LUP
2016-04-01 10:34:18
date last changed
2020-11-22 06:16:35
@article{0f876f71-d91c-41b3-ba6e-ae1eba4231d5,
  abstract     = {The turbidity variation in time and space is investigated in the downstream stretch of the river Gota Alv in Sweden. The river is heavily regulated and carries the discharge from the largest fresh water lake in Sweden, Lake Vanern, to the outflow point in Goteborg 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 Vanern and its large catchment area. For the river Gota Alv, 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 Vanern 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.},
  author       = {Göransson, Gunnel and Larson, Magnus and Bendz, D.},
  issn         = {1607-7938},
  language     = {eng},
  number       = {7},
  pages        = {2529--2542},
  publisher    = {European Geophysical Society},
  series       = {Hydrology and Earth System Sciences},
  title        = {Variation in turbidity with precipitation and flow in a regulated river system - river Gota Alv, SW Sweden},
  url          = {http://dx.doi.org/10.5194/hess-17-2529-2013},
  doi          = {10.5194/hess-17-2529-2013},
  volume       = {17},
  year         = {2013},
}