Prepared in cooperation with the Indiana Department of Environmental Management Estimating Selected Low-Flow Frequency Statistics and Harmonic-Mean Flows for Ungaged, Unregulated Streams in Indiana Scientific Investigations Report 2016–5102 Version 1.1, October 2016 U.S. Department of the Interior U.S. Geological Survey Cover. Bridge over Little Otter Creek in Jefferson County, Indiana. The photograph is courtesy of the U.S. Fish and Wildlife Service, Big Oaks National Wildlife Refuge. Estimating Selected Low-Flow Frequency Statistics and Harmonic-Mean Flows for Ungaged, Unregulated Streams in Indiana By Gary R. Martin, Kathleen K. Fowler, and Leslie D. Arihood Prepared in cooperation with the Indiana Department of Environmental Management Scientific Investigations Report 2016–5102 Version 1.1, October 2016 U.S. Department of the Interior U.S. Geological Survey U.S. Department of the Interior SALLY JEWELL, Secretary U.S. Geological Survey Suzette M. Kimball, Director U.S. Geological Survey, Reston, Virginia: 2016 First release: 2016 Revised: October 2016 (ver. 1.1) For more information on the USGS—the Federal source for science about the Earth, its natural and living resources, natural hazards, and the environment—visit http://www.usgs.gov or call 1–888–ASK–USGS. For an overview of USGS information products, including maps, imagery, and publications, visit http://store.usgs.gov/. Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the U.S. Government. Although this information product, for the most part, is in the public domain, it also may contain copyrighted materials as noted in the text. Permission to reproduce copyrighted items must be secured from the copyright owner. Suggested citation: Martin, G.R., Fowler, K.K., and Arihood, L.D., 2016, Estimating selected low-flow frequency statistics and harmonic-mean flows for ungaged, unregulated streams in Indiana (ver 1.1, October 2016): U.S. Geological Survey Scientific Investigations Report 2016 –5102, 45 p., http://dx.doi.org/10.3133/sir20165102. ISSN 2329-132X (online) iii Contents Acknowledgments ......................................................................................................................................vii Abstract ...........................................................................................................................................................1 Introduction ....................................................................................................................................................2 Purpose and Scope ..............................................................................................................................2 Previous Studies ..................................................................................................................................2 Description of Study Area ...................................................................................................................2 Physiography and Geology .................................................................................................................4 Climate ....................................................................................................................................................5 Development of Datasets for Streamgages ..............................................................................................5 Source of Low-Flow Frequency and Harmonic-Mean Flow Statistics ........................................5 Sources of Basin Characteristics ....................................................................................................12 Development of Equations for Estimating Selected Low-Flow Frequency Statistics and Harmonic-Mean Flows at Ungaged, Unregulated Stream Sites ....................................17 Logistic-Regression Analysis............................................................................................................17 Multiple-Linear-Regression Analyses .............................................................................................18 Limitations and Accuracy of the Estimating Equations ................................................................21 Prediction Intervals ...................................................................................................................27 Example Applications of the Estimating Equations .......................................................................28 Example 1 ....................................................................................................................................28 Example 2 ....................................................................................................................................28 Example 3 ....................................................................................................................................29 Results and Discussion of Regression Analyses ...................................................................................30 Summary........................................................................................................................................................30 References Cited..........................................................................................................................................31 Glossary .........................................................................................................................................................34 Appendix 1. Classification Tables for Logistic-Regression Equations for Estimating the Probability of Zero Flow for Selected Low-Flow Frequencies in Indiana .............................35 Appendix 2. Values Needed to Determine 90-Percent Prediction Intervals for Multiple-Linear-Regression Estimates of Low-Flow Statistics in Indiana ............................38 Appendix 3. Values of Basin Characteristics That Were Significant Explanatory Variables in the Regression Equations .......................................................................................40 iv Figures 1. Map showing major rivers and river basins in Indiana ..........................................................3 2. Map showing physiographic regions of Indiana and streamgages used in regression analyses .................................................................................................................4 3. Map showing grid of texture-based average horizontal hydraulic conductivity of the first 70 feet below land surface of unconsolidated deposits in Indiana ................13 4. Map showing residuals of a 7-day 10-year recurrence interval streamflow regression equation for the entire study area ......................................................................20 5. Screenshot of the weighted-multiple-linear regression program smoothing function for generalized-least squares correlation of the time series of annual minimum 7-day mean flows as a function of distance between 78 streamgages with 30 years of concurrent flow in Indiana ...........................................................................21 6. Graphs showing comparison of selected low-flow frequencies estimated from measured streamflow and from regression equations for unregulated streams in Indiana, observed and predicted values for annual minimum 1-day mean, 10-year low flows; annual minimum 7-day mean, 10-year low flows; and annual minimum 30-day mean, 10-year low flows .............................................................................23 7. Graphs showing comparison of harmonic-mean flows estimated from measured streamflow and from regression equations for unregulated streams in three low-flow regions of Indiana ........................................................................25 Tables 1. Description of U.S. Geological Survey streamgages and low-flow frequency statistics, harmonic-mean flows, and probability of zero flows used in the development of regional regression equations for Indiana ..................................................6 2. Description of basin characteristics evaluated as potential explanatory variables in regression equations for estimating selected low-flow statistics in Indiana ..............14 3. Logistic-regression equations for estimating the annual probability of zero flow for selected low-flow frequencies for ungaged, unregulated streams statewide in Indiana ......................................................................................................................................18 4. Generalized-least-squares regression equations for estimating selected nonzero low-flow frequencies for ungaged, unregulated streams statewide in Indiana ..............20 5. Weighted-least-squares regression equations for estimating harmonic-mean flow for ungaged, unregulated streams in each low-flow region in Indiana ...................22 6. Basin-characteristic ranges for the logistic-regression equations for estimating the annual probability of zero flow for selected low-flow frequencies and generalized-least-squares regression equations for estimating selected nonzero low-flow frequencies for ungaged, unregulated streams statewide in Indiana ..............22 7. Basin-characteristic ranges for the weighted-least-squares regression equations for estimating harmonic-mean flows for ungaged, unregulated streams in each low-flow region in Indiana ........................................................................................................22