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Scientific Investigations Report 2012–5138

Prepared in cooperation with the Ohio Water Development Authority

Methods for Estimating Selected Low-Flow Statistics and Development of Annual Flow-Duration Statistics for Ohio

By G.F. Koltun and Stephanie P. Kula

Thumbnail of and link to report PDF (10.3 MB)Abstract

This report presents the results of a study to develop methods for estimating selected low-flow statistics and for determining annual flow-duration statistics for Ohio streams. Regression techniques were used to develop equations for estimating 10-year recurrence-interval (10-percent annual-nonexceedance probability) low-flow yields, in cubic feet per second per square mile, with averaging periods of 1, 7, 30, and 90-day(s), and for estimating the yield corresponding to the long-term 80-percent duration flow. These equations, which estimate low-flow yields as a function of a streamflow-variability index, are based on previously published low-flow statistics for 79 long-term continuous-record streamgages with at least 10 years of data collected through water year 1997. When applied to the calibration dataset, average absolute percent errors for the regression equations ranged from 15.8 to 42.0 percent. The regression results have been incorporated into the U.S. Geological Survey (USGS) StreamStats application for Ohio ( in the form of a yield grid to facilitate estimation of the corresponding streamflow statistics in cubic feet per second. Logistic-regression equations also were developed and incorporated into the USGS StreamStats application for Ohio for selected low-flow statistics to help identify occurrences of zero-valued statistics.

Quantiles of daily and 7-day mean streamflows were determined for annual and annual-seasonal (September–November) periods for each complete climatic year of streamflow-gaging station record for 110 selected streamflow-gaging stations with 20 or more years of record. The quantiles determined for each climatic year were the 99-, 98-, 95-, 90-, 80-, 75-, 70-, 60-, 50-, 40-, 30-, 25-, 20-, 10-, 5-, 2-, and 1-percent exceedance streamflows. Selected exceedance percentiles of the annual-exceedance percentiles were subsequently computed and tabulated to help facilitate consideration of the annual risk of exceedance or nonexceedance of annual and annual-seasonal-period flow-duration values. The quantiles are based on streamflow data collected through climatic year 2008.

First posted January 30, 2013

For additional information contact:
Director, Ohio Water Science Center
U.S. Geological Survey
6480 Doubletree Avenue
Columbus, OH 43229-1111

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Suggested citation:

Koltun, G.F., and Kula, S.P., 2013, Methods for estimating selected low-flow statistics and development of annual flow-duration statistics for Ohio: U.S. Geological Survey Scientific Investigations Report 2012–5138, 195 p.,




Purpose and Scope

Previous Studies

Sources of Low-Flow Statistics and Flow-Duration Data

Methods for Estimating Low-Flow Statistics

Methods for Annual Flow-Duration Analyses

Results and Discussion of Annual Flow-Duration Analyses


References Cited

Appendix 1. Miscellaneous Supporting Data

Appendix 2. Basin Characteristics Tested for Use in Low-Flow Regression Analyses in Ohio

Appendix 3. Annual 1-Day and 7-Day Mean Flow-Duration Results for Sites with Streamflows that have No or Minimal Regulation

Appendix 4. Annual Seasonal-Period Flow-Duration Results for Sites with Streamflows that have No or Minimal Regulation

Appendix 5. Annual 1-Day and 7-Day Mean Flow-Duration Results for Sites with Streamflows that are Subject to Regulation

Appendix 6. Annual Seasonal-Period Flow-Duration Results for Sites with Streamflows that are Subject to Regulation

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