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Scientific Investigations Report 2014–5145

Prepared in cooperation with the Virginia Department of Environmental Quality

Methods for Estimating Drought Streamflow Probabilities for Virginia Streams

By Samuel H. Austin

Thumbnail of and link to report PDF (2.47 MB)Abstract

Maximum likelihood logistic regression model equations used to estimate drought flow probabilities for Virginia streams are presented for 259 hydrologic basins in Virginia. Winter streamflows were used to estimate the likelihood of streamflows during the subsequent drought-prone summer months. The maximum likelihood logistic regression models identify probable streamflows from 5 to 8 months in advance. More than 5 million streamflow daily values collected over the period of record (January 1, 1900 through May 16, 2012) were compiled and analyzed over a minimum 10-year (maximum 112-year) period of record. The analysis yielded the 46,704 equations with statistically significant fit statistics and parameter ranges published in two tables in this report. These model equations produce summer month (July, August, and September) drought flow threshold probabilities as a function of streamflows during the previous winter months (November, December, January, and February). Example calculations are provided, demonstrating how to use the equations to estimate probable streamflows as much as 8 months in advance.

First posted December 2, 2014

For additional information, contact:
Director, Virginia Water Science Center
U.S. Geological Survey
1730 East Parham Road
Richmond, VA 23228
http://va.water.usgs.gov/

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Suggested citation:

Austin, S.H., 2014, Methods for estimating drought streamflow probabilities for Virginia streams: U.S. Geological Survey Scientific Investigations Report 2014–5145, 20 p., http://dx.doi.org/10.3133/sir20145145.

ISSN 2328–031X (print)

ISSN 2328–0328 (online)



Contents

Acknowledgments

Abstract

Introduction

Methods of Study

Drought Streamflow Probability Estimates

Selection of an Equation

Application of the Equations with Examples

Summary

Selected References


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