Comparing in situ turbidity sensor measurements as a proxy for suspended sediments in North-Western European streams

Eva Skarbøvik, Sofie Gyritia Madsen van't Veen, Emma E. Lannergård, Hannah Wenng, Marc Stutter, Magdalena Bieroza, Kevin Atcheson, Philip Jordan, Jens Fölster, Per-Erik Mellander, Brian Kronvang, Hannu Marttila, Øyvind Kaste, Ahti Lepistö, Maria Kämäri

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Abstract

Climate change in combination with land use alterations may lead to significant changes in soil erosion and sediment fluxes in streams. Optical turbidity sensors can monitor with high frequency and can be used as a proxy for suspended sediment concentration (SSC) provided there is an acceptable calibration curve for turbidity measured by sensors and SSC from water samples. This study used such calibration data from 31 streams in 11 different research projects or monitoring programmes in six Northern European countries. The aim was to find patterns in the turbidity-SSC correlations based on stream characteristics such as mean and maximum turbidity and SSC, catchment area, land use, hydrology, soil type, topography, and the number and representativeness of the data that are used for the calibration. There were large variations, but the best correlations between turbidity and SSC were found in streams with a mean and maximum SSC of >30–200 mg/l, and a mean and maximum turbidity above 60–200 NTU/FNU, respectively. Streams draining agricultural areas with fine-grained soils had better correlations than forested streams draining more coarse-grained soils. However, the study also revealed considerable differences in methodological approaches, including analytical methods to determine SSC, water sampling strategies, quality control procedures, and the use of sensors based on different measuring principles. Relatively few national monitoring programmes in the six countries involved in the study included optical turbidity sensors, which may partly explain this lack of methodological harmonisation. Given the risk of future changes in soil erosion and sediment fluxes, increased harmonisation is highly recommended, so that turbidity data from optical sensors can be better evaluated and intercalibrated across streams in comparable geographical regions.
Original languageEnglish
Article number107006
Number of pages11
JournalCatena
Volume225
Early online date24 Feb 2023
DOIs
Publication statusPublished (in print/issue) - 15 May 2023

Bibliographical note

Funding Information:
We thank the Nordic Centre of Excellence BIOWATER, funded by NordForsk under Project No. 82263, The Norwegian Institute of Bioeconomy Research/The Research Council of Norway under Contract No. 342631/L10; FORMAS grant 2018-00890; Swedish Farmers’ Foundation for Agricultural Research SLF O-16-23-640, Academy of Finland projects (337523, 346163, 347704), the Freshwater Competence Centre (FWCC) Finland; and the Danish Innovation Foundation Industrial PhD project ‘SenTem’; grant 0153-00078B.

The monitoring programmes/projects have been funded by the Research Council of Norway No. 342631/L10 and 243967/E50, the Norwegian Environment Agency, the Morsa River Basin Sub-District (NO), the Swedish Research Council, the Swedish Agency of Marine and Water Management, the LifeIP-Rich Waters (SE); the Danish EPA Pesticide research project ‘SurfPest’, the MaaMet monitoring program funded by the Ministry of Agriculture and Forestry (FI), Southwest Finland ELY Centre, the Teagasc Agricultural Catchments Programme funded by the Irish Department of Agriculture, Food and the Marine (DAFM), the Source to Tap (IVA5018) project in Northern Ireland and Ireland supported by the European Union’s INTERREG VA Programme, managed by the Special EU Programmes Body (SEUPB).

Publisher Copyright:
© 2023 The Author(s)

Keywords

  • Turbidity
  • Optical sensor
  • Suspended sediments
  • Streams
  • Monitoring

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