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Scientific Investigations Report 2015–5040

Prepared in cooperation with the Illinois Environmental Protection Agency

Continuous Monitoring of Sediment and Nutrients in the Illinois River at Florence, Illinois, 2012–13

By Paul J. Terrio, Timothy D. Straub, Marian M. Domanski, and Nicolas A. Siudyla

Thumbnail of and link to report PDF (4.56 MB)Abstract

The Illinois River is the largest river in Illinois and is the primary contributing watershed for nitrogen, phosphorus, and suspended-sediment loading to the upper Mississippi River from Illinois. In addition to streamflow, the following water-quality constituents were monitored at the Illinois River at Florence, Illinois (U.S. Geological Survey station number 05586300), during May 2012–October 2013: phosphate, nitrate, turbidity, temperature, specific conductance, pH, and dissolved oxygen. The objectives of this monitoring were to (1) determine performance capabilities of the in-situ instruments; (2) collect continuous data that would provide an improved understanding of constituent characteristics during normal, low-, and high-flow periods and during different climatic and land-use seasons; (3) evaluate the ability to use continuous turbidity as a surrogate constituent to determine suspended-sediment concentrations; and (4) evaluate the ability to develop a regression model for total phosphorus using phosphate, turbidity, and other measured parameters. Reliable data collection was achieved, following some initial periods of instrument and data-communication difficulties. The resulting regression models for suspended sediment had coefficient of determination (R2) values of about 0.9. Nitrate plus nitrite loads computed using continuous data were found to be approximately 8 percent larger than loads computed using traditional discrete-sampling based models. A regression model for total phosphorus was developed by using historic orthophosphate data (important during periods of low flow and low concentrations) and historic suspended-sediment data (important during periods of high flow and higher concentrations). The R2 of the total phosphorus regression model using orthophosphorus and suspended sediment was 0.8. Data collection and refinement of the regression models is ongoing.

First posted May 28, 2015

For additional information, contact:
Director, Illinois Water Science Center
U.S. Geological Survey
405 N Goodwin
Urbana, IL 61801

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Suggested citation:

Terrio, P.J., Straub, T.D., Domanski, M.M., and Siudyla, N.A., 2015, Continuous monitoring of sediment and nutrients in the Illinois River at Florence, Illinois, 2012–13: U.S. Geological Survey Scientific Investigations Report 2015–5040, 61 p.,

ISSN 2328-0328 (online)




Purpose and Scope

Study Area


Instrument Performance and Operational Considerations





References Cited

Appendix 1. SOLITAX Turbidity Formazin Backscatter Ratio Units (FBRU) Model Information and Data

Appendix 2. YSI Turbidity Formazin Nephelometric Units (FNU) Model Information and Data

Appendix 3. Streamflow Model Information and Data

Appendix 4. Total Phosphorus Model Information and Data

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