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Open-File Report 2011–1070

Prepared in cooperation with the Pennsylvania Department of Environmental Protection

Selected Streamflow Statistics for Streamgage Locations in and near Pennsylvania

By Marla H. Stuckey and Mark A. Roland

ABSTRACT

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Streamflow statistics are used routinely by watershed planners, regulators, engineers, and managers for water-resource projects. Streamflow statistics for a streamgage can change over time as more flow data become available and (or) land use or climate in the watershed changes; consequently, streamflow statistics should be updated periodically. This report, done in cooperation with the Pennsylvania Department of Environmental Protection, presents updated streamflow statistics for 526 U.S. Geological Survey (USGS) continuous-record streamgages in Pennsylvania, New York, New Jersey, Delaware, Maryland, West Virginia, and Ohio using data collected through 2008. The following statistics are presented: low flows (1-day, 10-year; 7-day, 10-year; 7-day, 2-year; 30-day, 10-year; 30-day, 2-year; and 90-day, 10-year low flows), base flows (10-year, 25-year, and 50-year base flows), peak flows (50-, 20-, 10-, 4-, 2-, 1-, and 0.2-percent annual exceedance flood), mean flows (mean annual flow and harmonic mean flow), and flow durations (99-, 95-, 90-, 85-, 80-, 70-, 60-, 50-, 40-, 30-, 20-, 15-, 10-, 5-, and 1-percent exceedance). Streamflow statistics (7-day, 10-year and 30-day, 10-year low flows; harmonic mean; and 95-, 50-, and 5-percent flow duration exceedances) for 72 streamgage locations in Pennsylvania were compared using a Wilcoxon signed-rank test to previously reported statistics. A statistically significant difference was found between the data sets for the 30-day, 10-year low-flow; harmonic mean; 50-percent flow-duration exceedance; and 5-percent flow-duration exceedance statistics. No significant difference was found between the data sets for the 7-day, 10-year low-flow and 95-percent flow-duration exceedance statistics. The lower flow statistics show a decrease since 1996, and the mid- to higher flows show an increase since 1996.

First posted May 3, 2011

For additional information contact:
Director, Pennsylvania Water Science Center
U.S. Geological Survey
215 Limekiln Road
New Cumberland, PA 17070
http://pa.water.usgs.gov/

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Suggested citation:

Stuckey, M.H., and Roland, M.A., 2011, Selected streamflow statistics for streamgage locations in and near Pennsylvania: U.S. Geological Survey Open-File Report 2011–1070, 88 p.



Contents

Abstract

Introduction

Purpose and Scope

Previous Investigations

Data Collection and Analysis

Comparison with Previously Reported Streamflow Statistics for Streamgage Locations in Pennsylvania

Summary

Acknowledgments

References Cited


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