Estimated Total Phosphorus Loads for Selected Sites on Great Lakes Tributaries, Water Years 2014–2018

Open-File Report 2020-1145
Prepared in cooperation with the Great Lakes Restoration Initiative
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  • Document: Report (1.69 MB pdf)
  • Appendixes:
    • Appendix 1 (16.4 kB xlsx) — Estimated annual total phosphorus loads and flow-weighted mean concentrations at selected U.S. Geological Survey gage sites on Great Lakes tributaries
    • Appendix 1 (8.45 kB csv) — Estimated annual total phosphorus loads and flow-weighted mean concentrations at selected U.S. Geological Survey gage sites on Great Lakes tributaries
    • Appendix 2 (66.0 kB xlsx) — Estimated monthly total phosphorus loads at selected U.S. Geological Survey gage sites on Great Lakes tributaries
    • Appendix 2 (64.8 kB csv) — Estimated monthly total phosphorus loads at selected U.S. Geological Survey gage sites on Great Lakes tributaries
  • Data Release: USGS data release — Model archive—Estimated total phosphorus loads for selected sites on Great Lakes tributaries, water years 2014–2018
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Abstract

Monthly and annual total phosphorus loads were estimated for water years 2014 through 2018 for 23 streamgaged (gaged) sites on tributaries to the Great Lakes. Processing and regression methods described by Robertson and others (2018) were used with discrete and continuous data collected during water years 2011 and 2018 to update regression models for estimating instantaneous flux with the same form of equations as published by Robertson and others (2018). Monthly and water year average fluxes for all but two of the 23 gage sites were estimated using a weighted combination of results from surrogate models (which have streamflow, turbidity, and seasonal indicators as explanatory variables) and unit-value (UV)-flow models which have only UV streamflow and seasonal indicators as explanatory variables. Two of the gage sites had extensive periods of missing turbidity records, so average flux estimates for those stations were based solely on results from UV-flow models.

For most sites, estimated loads of total phosphorus were computed and summed for water years 2014–2018. The cumulative loads were used to compute yields and flow-weighted mean concentrations for water years 2014–2018. The estimated cumulative total phosphorus loads for water years 2014–2018 ranged from 112 to 11,500 metric tons. The Maumee River site (U.S. Geological Survey gage number 04193500) had the largest estimated cumulative load for water years 2014–2018 and the third largest estimated flow-weighted mean concentration. In fact, the estimated cumulative load at the Maumee River site was more than three times larger than the second largest estimated cumulative load.

Estimated average annual total phosphorus yields and flow-weighted mean concentrations for water years 2014–2018 ranged from 0.016 metric tons per square kilometer to 0.771 metric tons per square kilometer and 0.033 milligram per liter to 0.466 milligram per liter, respectively. The Cattaraugus Creek gage site (U.S. Geological Survey gage number 04213500) had the highest estimated average annual total phosphorus yield and flow-weighted mean concentration. The average annual total phosphorus yield at the Cattaraugus Creek gage site was almost twice as large as the second largest estimated yield.

Suggested Citation

Koltun, G.F., 2021, Estimated total phosphorus loads for selected sites on Great Lakes tributaries, water years 2014–2018: U.S. Geological Survey Open-File Report 2020–1145, 13 p., https://doi.org/10.3133/ofr20201145.

ISSN: 2331-1258 (online)

Study Area

Table of Contents

  • Abstract
  • Introduction
  • Study Methods
  • Regression Equations and Estimated Total Phosphorus Loads
  • Summary
  • Acknowledgments
  • References Cited
Publication type Report
Publication Subtype USGS Numbered Series
Title Estimated total phosphorus loads for selected sites on Great Lakes tributaries, water years 2014–2018
Series title Open-File Report
Series number 2020-1145
DOI 10.3133/ofr20201145
Year Published 2021
Language English
Publisher U.S. Geological Survey
Publisher location Reston, VA
Contributing office(s) Ohio-Kentucky-Indiana Water Science Center
Description Report: v, 13 p.; 2 Appendixes; Data Release
Country United States
State Illinois, Indiana, Michigan, Minnesota, New York, Ohio, Wisconsin
Online Only (Y/N) Y
Additional Online Files (Y/N) Y
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