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Comparison of Turbidity Sensors at U.S. Geological Survey Supergages in Indiana From November 2018 To December 2021

Scientific Investigations Report 2023-5077
Prepared in cooperation with the Indiana Department of Environmental Management, Iroquois River Conservancy District, Kankakee River Basin and Yellow River Basin Development Commission, and the Town of Zionsville
By: , , and 
https://doi.org/10.3133/sir20235077

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Abstract

Beginning in September 2010, the U.S. Geological Survey installed continuous water-quality monitors at several streamgages across Indiana as part of a network of supergages to meet cooperator information needs. Two types (or models) of water-quality monitors deployed at each site measured and recorded water temperature, dissolved oxygen, specific conductance, pH, and turbidity every 15 minutes during the study period. Associated discrete water samples were collected at regular intervals and analyzed for concentrations of suspended sediment and total phosphorus. Surrogate regression models were developed between the continuously measured turbidity values and turbidity values in the associated samples to compute continuous concentrations and loads of suspended sediment and total phosphorus. Starting in November 2018, the original extended deployment system monitors were replaced with the newest model of multiparameter water-quality monitors and were equipped with turbidity smart sensors because the older monitors were phased out of production. The updated monitor and smart sensor yield different but relatable turbidity values.

Turbidity data collected concurrently by the two sensors from November 2018 to December 2021 were compared and analyzed to quantify the relation between them at six supergage sites in northwestern Indiana and one site in the town of Zionsville in central Indiana. Ordinary least squares regression was used to calculate site-specific conversion factors so that turbidity data from the newer monitors can be used in published surrogate models based on the older monitor data. Regression analyses explained approximately 98 percent of the variation in turbidity readings between the two sensors. From these analyses, conversion factors were developed that may be applied to older turbidity readings to calculate near real-time concentrations of phosphorus and suspended sediment.

Suggested Citation

Messner, M.L., Perkins, M.K., and Bunch, A.R., 2023, Comparison of turbidity sensors at U.S. Geological Survey supergages in Indiana from November 2018 to December 2021: U.S. Geological Survey Scientific Investigations Report 2023–5077, 13 p., https://doi.org/10.3133/sir20235077.

ISSN: 2328-0328 (online)

Study Area

Table of Contents

  • Abstract
  • Introduction
  • Purpose and Scope
  • Study Area
  • Study Methods
  • Continuous Water-Quality Monitoring
  • Comparison of Turbidity-Sensor Measurements
  • Results of Regression Analyses
  • Summary
  • Acknowledgments
  • References Cited
Publication type Report
Publication Subtype USGS Numbered Series
Title Comparison of turbidity sensors at U.S. Geological Survey supergages in Indiana from November 2018 to December 2021
Series title Scientific Investigations Report
Series number 2023-5077
DOI 10.3133/sir20235077
Year Published 2023
Language English
Publisher U.S. Geological Survey
Publisher location Reston, VA
Contributing office(s) Ohio-Kentucky-Indiana Water Science Center
Description Report: iv, 13 p.; Dataset
Country United States
State Indiana
Other Geospatial Kankakee River basin
Online Only (Y/N) Y
Additional Online Files (Y/N) N
Google Analytic Metrics Metrics page
Additional publication details