Scientific Investigations Report 2010–5217

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SIR 2010–5217

## AbstractThis report provides estimates of, and presents methods for estimating, selected low-flow frequency statistics for unregulated streams in Kentucky including the 30-day mean low flows for recurrence intervals of 2 and 5 years (30Q Logistic-regression equations are presented for estimating the annual probability of the selected low-flow frequency statistics being equal to zero. Weighted-least-squares regression equations were developed for estimating the magnitude of the nonzero 30Q The explicit explanatory variables in the regression equations include total drainage area and the mapped streamflow-variability index measured from a revised statewide coverage of this characteristic. The percentage of the station low-flow statistics correctly classified as zero or nonzero by use of the logistic-regression equations ranged from 87.5 to 93.8 percent. The average standard errors of prediction of the weighted-least-squares regression equations ranged from 108 to 226 percent. The 30Q The regression equations are applicable only to stream sites with low flows unaffected by regulation from reservoirs and local diversions of flow and to drainage basins in specified ranges of basin characteristics. Caution is advised when applying the equations for basins with characteristics near the applicable limits and for basins with karst drainage features. |
Posted December 21, 2010
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Martin, G.R., and Arihood, L.D., 2010, Methods for estimating selected low-flow frequency statistics for unregulated streams in Kentucky: U.S. Geological Survey Scientific Investigations Report 2010–5217, 83 p., plus 2 pl.

Abstract

Introduction

Methods for Data-Collection Stations

Methods for Ungaged Stream Sites

Summary

References Cited

Glossary

Appendix 1. Trend Tests of Long-Term Climate Data for Kentucky During 1895–2004

Appendix 2. Trend-Test Screening of Annual 7-Day Low Flows for Selected Long-Term Continuous-Record Streamflow-Gaging Stations in Kentucky for Various Periods of Record

Appendix 3. Double-Mass Curves Showing Relations of Cumulative Annual 7-Day Low Flows among Selected Hydro-Climate Data Network, Hydrologic Benchmark Network, and

Reference Streamflow-Gaging Stations in and surrounding Kentucky

Appendix 4. A Procedure for Detrending Annual Low-Flow Data for Frequency Analysis

Appendix 5. Classification Tables for Logistic-Regression Equations for Estimating the Probability of Zero Flow For Selected Low-Flow Frequencies in Kentucky