ATLA

NTI

C O

CEA

N

NORTH CAROLINATENNESSEE

KENT

UCKY

WES

T VI

RGIN

IA

MARYLAND

WASHINGTON, D.C.

Culpeper Basin

U.S. Department of the InteriorU.S. Geological Survey

Scientific Investigations Report 20115143

Prepared in cooperation with the Virginia Department of Environmental Quality

Low-Flow Characteristics of Virginia Streams

Cover art. See figure 1 (map showing low-flow study sites in Virginia).

Low-Flow Characteristics of Virginia Streams

By Samuel H. Austin, Jennifer L. Krstolic, and Ute Wiegand

Prepared in cooperation with the Virginia Department of Environmental Quality

Scientific Investigations Report 20115143

U.S. Department of the InteriorU.S. Geological Survey

U.S. Department of the InteriorKEN SALAZAR, Secretary

U.S. Geological SurveyMarcia K. McNutt, Director

U.S. Geological Survey, Reston, Virginia: 2011

For more information on the USGSthe Federal source for science about the Earth, its natural and living resources, natural hazards, and the environment, visit http://www.usgs.gov or call 1888ASKUSGS.

For an overview of USGS information products, including maps, imagery, and publications, visit http://www.usgs.gov/pubprod

To order this and other USGS information products, visit http://store.usgs.gov

Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government.

Although this report is in the public domain, permission must be secured from the individual copyright owners to reproduce any copyrighted materials contained within this report.

Suggested citation:Austin, S.H., Krstolic, J.L., and Wiegand, Ute, 2011, Low-flow characteristics of Virginia streams: U.S. Geological Survey Scientific Investigations Report 20115143, 122 p. + 9 tables on CD.

(Also available online at http://pubs.usgs.gov/sir/2011/5143/.)

ISBN 978 1 4113 3287 4

http://www.usgs.govhttp://www.usgs.gov/pubprodhttp://store.usgs.gov

iii

ContentsAbstract ...........................................................................................................................................................1Introduction.....................................................................................................................................................1

Purpose and Scope ..............................................................................................................................1Background............................................................................................................................................2Physical Setting.....................................................................................................................................2

Coastal Plain .................................................................................................................................2Piedmont........................................................................................................................................2Blue Ridge .....................................................................................................................................4Valley and Ridge ...........................................................................................................................4Appalachian Plateaus .................................................................................................................4

Previous Studies ...................................................................................................................................4Approach .........................................................................................................................................................5

Site Selection.........................................................................................................................................5Data Evaluation .....................................................................................................................................5Monthly Streamflow Statistics ...........................................................................................................6Flow-Duration Curves...........................................................................................................................6Low-Flow Frequency Analysis ............................................................................................................6

Conditional-Probability Adjustment ..........................................................................................7MOVE.1 Regression Equations for Short-Term, Continuous-Record and Partial-Record

Streamgaging Stations ...........................................................................................................8MOVE.1 Analyses for Short-Term, Continuous-Record Streamgaging Stations ...............8MOVE.1 Analyses for Partial-Record Streamgaging Stations .............................................8

Basin Characteristics ...........................................................................................................................9Regionalization ...............................................................................................................................................9

Definition of Regions ............................................................................................................................9Model Development ...........................................................................................................................12Model Verification and Diagnostics ................................................................................................12

Weighting Multiple Estimates ....................................................................................................................19Weighting of Independent Estimates ..............................................................................................19

Low-Flow Characteristics...........................................................................................................................20Other Methods for Estimation at Ungaged Sites ....................................................................................20Example Applications ..................................................................................................................................20

Use of Regression Equations ............................................................................................................21Drainage-Area Ratio Method ...........................................................................................................21Ungaged Site with Nearby Gage ......................................................................................................21Gaged Site ............................................................................................................................................22

Summary........................................................................................................................................................22Acknowledgments .......................................................................................................................................22References ....................................................................................................................................................23Glossary .........................................................................................................................................................26

iv

Figures 1. Map showing selected low-flow study sites and physiographic provinces

for application of low-flow regional estimating equations. ...................................................3 2. Example leverage plots showing significant explanatory power, insignificant

explanatory power, and evidence of collinearity ..................................................................13

Tables 1. Study sites and their identifying information ......................................................CD in pocket 2. Monthly streamflow statistics for selected continuous-record

streamgaging stations ............................................................................................CD in pocket 3. Flow-duration statistics and flow variability indices for selected

streamgaging stations ............................................................................................CD in pocket 4. Low-flow characteristics of streamgaging stations in Virginia ..........................................27 5. Low-flow MOVE.1 equations for selected short-term,

continuous-record streamgaging stations ..........................................................CD in pocket 6. Low-flow MOVE.1 equations for selected partial-record

streamgaging stations ............................................................................................CD in pocket 7. Statistics summarizing basin characteristics selected for regional

regression of low flows in Virginia .......................................................................CD in pocket 8. Selected basin characteristics, their definitions, and datasources ..................................10 9. Basin characteristics of low-flow streamgaging stations in Virginia .............CD in pocket 10. Regional regression equations for estimating low flows

of streams in Virginia ..........................................................................................................