U.S. Department of the Interior

U.S. Geological Survey

Scientific Investigations Report 2012–5142

Prepared in cooperation with the Pennsylvania Department of Environmental Protection, 

the Susquehanna River Basin Commission, and The Nature Conservancy

Estimation of Baseline Daily Mean Streamflows for Ungaged 

Locations on Pennsylvania Streams, Water Years 1960–2008 Streamflow, in cubic feet per second

1

10

100

1,000

10,000

100,000

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

Exceedance probability

Streamflow, in cubic feet per square mile

0.01

0.1

1

10

100

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

Exceedance probability

Streamflow, in cubic feet per second

0

2,000

4,000

6,000

8,000

10,000

12,000

1959196119631965

1967

1969

19711973

1975197719791981198319851987

19891991

19931995

199719992001200320052007

Streamflow, in cubic feet per square mile

1959196119631965

1967

1969

19711973

1975197719791981198319851987

1989199119931995199719992001200320052007

0

10

20

30

40

50

60

70
Cover. Estimated flow-duration curves and hydrographs generated by the Baseline Streamflow Estimator.
Estimation of Baseline Daily Mean 

Streamflows for Ungaged Locations 

on Pennsylvania Streams, 

Water Years 1960–2008

By Marla Stuckey, Edward Koerkle, James Ulrich

Prepared in cooperation with 

the Pennsylvania Department of Environmental Protection, the Susquehanna 

River Basin Commission, and The Nature Conservancy

Scientific Investigations Report 2012–5142

U.S. Department of the Interior

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

KEN SALAZAR, Secretary

U.S. Geological Survey

Marcia K. McNutt, Director

U.S. Geological Survey, Reston, Virginia: 2012

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://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:

Stuckey, M.H., Koerkle, E.H., and Ulrich, J.E., 2012, Estimation of baseline daily mean streamflows for ungaged 

locations on Pennsylvania streams, water years 1960–2008: U.S. Geological Survey Scientific Investigations Report 

2012–5142, 61 p.
iii

Acknowledgments

The authors thank Stacey Archfield of the U.S. Geological Survey for providing technical 

expertise and support on the use of the QPPQ and map correlation method. The authors also 

thank Brandon Fleming, Chris Gazoorian, and Curtis Schreffler of the U.S. Geological Survey 

for their technical reviews of both the report and BaSE; Hoss Liaghat and Mike Hill of the 

Pennsylvania Department of Environmental Protection, Greg Cavallo of the Delaware River 

Basin Commission, and Michele DePhilip and Tara Moberg of The Nature Conservancy for 

their reviews and testing of Baseline Streamflow Estimator; Scott Hoffman of the U.S. Geological Survey for his GIS support; and the Hydrologic Surveillance Program staffs in the U.S. 

Geological Survey Pennsylvania, Maryland, New York, Ohio, and West Virginia Water Science 

Centers for their compilation and review of streamgage data.
iv

Contents

Acknowledgments........................................................................................................................................iii

Abstract...........................................................................................................................................................1

Introduction.....................................................................................................................................................1

Previous Studies ...................................................................................................................................2

Purpose and Scope ..............................................................................................................................2

Estimation of Baseline Daily Mean Streamflow .......................................................................................2

Reference Streamgages in Pennsylvania and Surrounding States.............................................3

Criteria ..........................................................................................................................................4

Record Extension.........................................................................................................................4

Regression Equations for Estimating Flow-Duration Exceedance Probabilities .......................7

Streamgages and Basin Characteristics Used in Regression Analysis.............................7

Regression Analysis and Resulting Flow-Duration Exceedance Probability 

Regression Equations....................................................................................................7

Selection of Reference Streamgages for Estimating Baseline Daily Mean Streamflow .......12

Map Correlation .........................................................................................................................12

Application of Map Correlation in Two Pilot Basins ...................................................12

Correlation Metrics ................................................................................................12

Distance Metrics .....................................................................................................16

Anisotropy.................................................................................................................16

Analysis and Results of Map Correlation in Two Pilot Basins...................................17

Statewide Map Correlation Development .............................................................................18

Use of BaSE for Estimating Baseline Daily Mean Streamflow for Ungaged Locations...................20

Accuracy and Limitations of Estimated Baseline Streamflows...........................................................20

Summary........................................................................................................................................................24

References Cited..........................................................................................................................................25

Appendix 1. Description of reference streamgages used in the development of BaSE 

for Pennsylvania with period of record and use of data......................................................28

Appendix 2. Reference streamgages with record extension techniques applied ........................34

Appendix 3. Basin characteristics used in the development of flow-duration 

regression equations .................................................................................................................43

Appendix 4. Flow-duration exceedance probabilities, observed and computed 

from streamflow data, and regression equations for streamgages used 

in regression analysis ................................................................................................................47

Appendix 5. User’s Guide for the Baseline Streamflow Estimator (BaSE)......................................57

.
v

Figures

1. Schematic design of the QPPQ method used in the Baseline Streamflow Estimator 

(BaSE) showing, A, observed daily mean streamflow at a reference streamgage, 

B, flow duration curve at the reference streamgage, C, constructed flow duration 

curve at the ungaged location, and, D, estimated daily mean streamflow at the 

ungaged location ..........................................................................................................................3

2. Map showing location of U.S. Geological Survey reference streamgages in and 

near Pennsylvania ........................................................................................................................5

3. Map showing normalized net water use in selected U.S. Geological Survey 

streamgage basins in Pennsylvania, 2003................................................................................6

4. Example correlation map for U.S. Geological Survey streamgage 01559000, 

Juniata River at Huntingdon, Pa...............................................................................................13

5. Map showing location of pilot test basins in Pennsylvania and reference 

streamgages for the map correlation method.......................................................................14

6. Boxplots showing distribution of Nash-Sutcliffe efficiency values computed from 

observed and estimated correlations of daily mean streamflows at selected 

U.S. Geological Survey streamgages in, A, the Lower Susquehanna River Basin 

and, B, the Upper Delaware River Basin in Pennsylvania...................................................17

7. Graph showing success rate for selection of the best correlated streamgage 

by using distance and map correlation methods applied in the pilot basins ...................18

8. Screen capture of report generated by the BaSE tool showing flow duration 

curves and a hydrograph ..........................................................................................................21

9. Graphs showing observed and estimated daily mean streamflow for U.S. Geological 

Survey streamgage 01548500 Pine Creek at Cedar Run, Pa., using, A, log-linear 

interpolation and, B, log-log interpolation..............................................................................22

10. Boxplots showing distribution of, A, Nash-Sutcliffe efficiency values and, B, root 

mean square error obtained from comparison between observed and estimated 

daily mean streamflows in the two pilot basins in Pennsylvania.......................................23

11. Hydrographs and flow duration curves showing estimated and observed daily 

mean flows for U.S. Geological Survey streamgages, A, 01556000, Frankstown 

Branch Juniata River at Williamsburg, Pa., and, B, 01452500, Monocacy Creek 

at Bethlehem, Pa.........................................................................................................................23

Tables

1. Basin characteristics used in the development of regression equations for 

flow-duration exceedance probabilities for Pennsylvania streams. ...................................8

2. Regression coefficients for use with flow-duration exceedance probability 

regression equations for Pennsylvania streams...................................................................11

3. Description of selected U.S. Geological Survey reference streamgages in the Upper 

Delaware River Basin and the Lower Susquehanna River Basin in Pennsylvania.........15

4. Summary of map correlation application in two pilot basins in Pennsylvania ................19

5. Mean streamflow correlations for reference streamgages used in the map 

correlation method for Pennsylvania streams, by drainage area and major basin ........20

6. Basin characteristics with minimum, maximum, and mean values used 

in development of regression equations to estimate flow-duration exceedance 

probabilities with BaSE for basins in Pennsylvania..............................................................24
vi

Conversion Factors

Inch/Pound to SI

Multiply By To obtain

Length

inch (in.) 2.54 centimeter (cm)

foot (ft) 0.3048 meter (m)

mile (mi) 1.609 kilometer (km)

Area

acre 4,047 square meter (m2)

square mile (mi2) 259.0 hectare (ha)

square mile (mi2) 2.590 square kilometer (km2) 

Volume

gallon (gal) 0.003785 cubic meter (m3) 

gallon (gal) 3.785 cubic decimeter (dm3) 

million gallons (Mgal) 3,785 cubic meter (m3)

acre-foot (acre-ft) 1,233 cubic decimeter (dm3)

acre-foot (acre-ft) 0.001233 cubic meter (m3)

Flow rate

cubic foot per second (ft3/s) 0.02832 cubic meter per second (m3/s)

cubic foot per second per square mile 

[(ft3/s)/mi2]

0.01093 cubic meter per second per square 

kilometer [(m3/s)/km2]

cubic foot per day (ft3/d) 0.02832 cubic meter per second (m3/s)

gallon per day (gal/d) 0.003785 cubic meter per day (m3/d)

gallon per day per square mile [(gal/d)/mi2] 1,233 cubic meter (m3)

million gallons per day (Mgal/d) 0.001233 cubic hectometer (hm3) 

Temperature in degrees Fahrenheit (°F) may be converted to degrees Celsius (°C) as follows:

°C = (°F – 32) / 1.8

Vertical coordinate information is referenced to the North American Vertical Datum of 1988 

(NAVD 88).

Horizontal coordinate information is referenced to the North American Datum of 1983 (NAD 83).

Altitude, as used in this report, refers to distance above the vertical datum.
vii

Acronyms

BaSE Baseline Streamflow Estimator

FDC Flow duration curve

GIS Geographic Information System

GNWISQ Get NWIS WEB Streamflow Data Files

HUC Hydrologic Accounting Unit Code

LOC Line of organic correlation

MASYE Massachusetts Safe Yield Estimator

MkPP Make Plotting Position File

MOVE Maintenance of variance

NS Nash-Sutcliffe efficiency value

NWIS National Water Information System

OLS Ordinary least squares regression

Pn nth percentile from flow duration curve

QPPQ Methodology equating the streamflow as a percentile from a flow duration curve for 

a particular day at an ungaged location to the streamflow as a percentile from the 

flow duration curve for the same day at a reference streamgage

RMSE Root mean square error

SREF Streamflow Record Extension Facilitator

WLS Weighted least squares regression

WY Water year
viii
Estimation of Baseline Daily Mean Streamflows for 

Ungaged Locations on Pennsylvania Streams, 

Water Years 1960–2008 

By Marla H. Stuckey, Edward H. Koerkle, and James E. Ulrich

Abstract

Water-resource managers use daily mean streamflows to 

generate streamflow statistics and analyze streamflow conditions. An in-depth evaluation of flow regimes to promote 

instream ecological health often requires streamflow information obtainable only from a time series hydrograph. Historically, it has been difficult to estimate daily mean streamflow 

for an ungaged location. The U.S. Geological Survey, in cooperation with the Pennsylvania Department of Environmental 

Protection, Susquehanna River Basin Commission, and The 

Nature Conservancy, has developed the Baseline Streamflow 

Estimator (BaSE) to estimate baseline streamflow at a daily 

time scale for ungaged streams in Pennsylvania using data 

collected during water years 1960–2008. Baseline streamflow is minimally altered by regulation, diversion, or mining, 

and other anthropogenic activities. Daily mean streamflow is 

estimated in BaSE using a methodology that equates streamflow as a percentile from a flow duration curve for a particular 

day at an ungaged location with streamflow as a percentile 

from the flow duration curve for the same day at a reference 

streamgage that is considered to be hydrologically similar to 

the ungaged location. An appropriate reference streamgage is 

selected using map correlation, in which variogram models 

are developed that correlate streamflow at one streamgage 

with streamflows at all other streamgages. The percentiles 

from a flow duration curve for the ungaged location are 

converted to streamflow through the use of regression equations. Regression equations used to predict 17 flow-duration 

exceedance probabilities were developed for Pennsylvania 

using geographic information system-derived basin characteristics. The standard error of prediction for the regression 

equations ranged from 11 percent to 92 percent with the mean 

of 31 percent.

The map correlation method for estimating streamflow 

was tested at locations within two pilot basins, the Upper 

Delaware River Basin and the Lower Susquehanna River 

Basin, before being applied statewide. Reference streamgages 

within the pilot basins were used as ungaged locations for analyzing the map correlation method. Correlation using Spearman’s rho and centroid distance performed as well as, or better 

than, the method using the closest streamgage as a reference 

streamgage. Map correlation using the correlation metrics 

identified in the pilot basins was applied to 156 streamgages in 

and near Pennsylvania. 

BaSE uses the map correlation method and flow-duration 

exceedance probability regression equations to estimate 

baseline daily mean streamflow for an ungaged location. 

The output from BaSE is a Microsoft Excel® report file that 

summarizes the reference streamgage and ungaged location 

information, including basin characteristics, percent difference in basin characteristics between the two locations, any 

warning associated with the basin characteristics, mean and 

median streamflow for the ungaged location, and a daily 

hydrograph of streamflow for water years 1960–2008 for the 

ungaged location. The daily mean streamflow for the ungaged 

location can be exported as a text file to be used as input into 

other statistical software packages. BaSE estimates daily mean 

streamflow for baseline conditions only, and any alterations 

to streamflow from regulation, large water use, or substantial 

mining are not reflected in the estimated streamflow. 

Introduction

The natural flow regime of a stream or river is vital to 

the sustainability and health of aquatic freshwater ecosystems. 

The ability to characterize baseline, or minimally altered, 

streamflow conditions, compare them with current conditions, project future conditions, and assess effects of human 

activities on streamflow is fundamental to water-management 

programs addressing water allocation, human-health issues, 

recreation needs, and establishment of ecological flow criteria. 

Water-resource managers undertaking an in-depth evaluation 

of flow regimes to promote instream ecological health often 

require daily mean streamflow information obtainable only 
2 Estimation of Baseline Daily Mean Streamflows for Ungaged Locations on Pennsylvania Streams, WY 1960–2008

from a time series hydrograph. Daily mean streamflow allow 

water-resource managers to assess streamflow and determine 

streamflow statistics that fulfill their individual needs. 

State, Federal, and local agencies have been working 

collaboratively on aquatic instream flow needs and developing environmental flow criteria for water management in 

Pennsylvania (DePhilip and Moberg, 2010). To assist in this 

effort, the U.S. Geological Survey (USGS), in cooperation 

with the Pennsylvania Department of Environmental Protection (PaDEP), Susquehanna River Basin Commission (SRBC), 

and The Nature Conservancy (TNC), has developed a tool to 

estimate minimally altered, or baseline, streamflow at a daily 

time scale for ungaged streams in Pennsylvania. The Baseline Streamflow Estimator (BaSE) will provide hydrologists, 

ecologists, and water managers streamflow information to 

effectively assess baseline streamflow conditions as related 

to water allocation, aquatic instream-flow needs, and water 

availability. A range of ecologically relevant flow statistics 

can be computed from estimated daily mean streamflow using 

statistical software packages, such as Indicators of Hydrologic 

Alteration (IHA) (The Nature Conservancy, 2009) and Hydroecological Integrity Assessment Tool (HAT) (Henriksen and 

others, 2006). 

Previous Studies

Fennessey (1994) introduced a method to estimate 

streamflow statistics for an ungaged location (termed “QPPQ” 

method). This method was used by Hughes and Smakhtin 

(1996), Smakhtin (1999), Smakhtin and Masse (2000), 

Mohamoud (2008), Archfield and others (2010), and Shu and 

Ourda (2012). Archfield and Vogel (2010) developed a method 

for selecting reference streamgages for an ungaged location on 

the basis of streamflow correlation (termed the “map correlation method”). This method has been successfully applied in 

Massachusetts (Archfield and others, 2010) and the Connecticut River Basin (Stacey Archfield, U.S. Geological Survey, 

written commun., 2012). The combination of the QPPQ 

method and map correlation method for selecting an appropriate reference streamgage was incorporated into the Massachusetts Sustainable-Yield Estimator (MASYE) by Archfield and 

others (2010). The combination of methods, or parts thereof, is 

being developed for applications in New York and Maryland 

(Ward Freeman, U.S. Geological Survey, oral commun., 2011, 

and Brandon Fleming, U.S. Geological Survey, oral commun., 2011). A report from The Nature Conservancy (TNC; 

Apse and others, 2008) for the Pennsylvania Instream Flow 

Technical Advisory Committee describes studies conducted to 

assess instream flow needs, presents methods, and describes 

the Ecological Limits of Hydrologic Alteration (Poff and 

others, 2010). 

Regression equations are used to estimate streamflow 

characteristics where streamgage data are not available. 

Regression equations have not been developed for flowduration exceedance probabilities in Pennsylvania; however, 

regression equations have been developed for estimating 

low-flow, mean-flow, and base-flow statistics (Stuckey, 2006), 

as well as flood-frequency statistics (Roland and Stuckey, 

2008). Flow-duration statistics for more than 500 streamgages 

in and near Pennsylvania are presented by Stuckey and Roland 

(2011). Regression estimates and streamflow statistics can 

be found for gaged and ungaged streams in Pennsylvania at 

the StreamStats web application (http://water.usgs.gov/osw/

streamstats/pennsylvania.html) (Stuckey and Hoffman, 2010).

Purpose and Scope

This report presents the data and methodology used to 

estimate minimally altered (baseline) daily mean streamflow for water years1

 1960 to 2008 for ungaged locations on 

streams in Pennsylvania. Parameter-based regression equations used to predict 17 exceedance probabilities from the flow 

duration curve (FDC) for ungaged streams in Pennsylvania 

are presented. Flow-duration exceedance probabilities for 

162 streamgages are presented. Streamflow data from continuous-record streamgages were used to develop correlation maps 

of the predicted correlation of streamflow between an ungaged 

location and a reference streamgage. A description and instructions for the use of BaSE, a tool for estimating baseline daily 

mean streamflow for Pennsylvania streams, are presented.

Estimation of Baseline Daily Mean 

Streamflow

The BaSE tool for estimating baseline daily mean 

streamflow for ungaged locations on Pennsylvania streams 

is based on the QPPQ method (Fennessey, 1994; Hughes 

and Smakhtin, 1996; Smakhtin, 1999; Smakhtin and Masse, 

2000; Mohamoud, 2008; Archfield and others, 2010; and Shu 

and Ourda, 2012), which equates streamflow expressed as a 

percentile from the FDC for a particular day at an ungaged 

location with the percentile from a FDC for the same day at a 

hydrologically similar location where streamflow is measured 

(referred to as “reference streamgage”). A graphical depiction 

of the QPPQ methodology is shown in figure 1. Geospatial 

correlation of streamflow (Archfield and others, 2010) is used 

to select a reference streamgage for the ungaged location. 

Streamflows corresponding to the flow-duration exceedance probability for the ungaged location are selected from a 

daily FDC constructed from points determined by regression 

equations. This method was successfully applied in Massachusetts and incorporated into the MASYE (Archfield and 

others, 2010).

The FDC for the reference streamgage is a cumulative frequency curve that shows the percentage of time that 

1

 Water year (WY) is defined as a 12-month period beginning October 1 and 

ending September 30. The water year is designated by the calendar year in 

which it ends.
Estimation of Baseline Daily Mean Streamflow 3

Reference gage streamflow

Reference gage streamflow

Unagaged streamflow

Unagaged streamflow

Date

Date

Exceedance probability

Exceedance probability

A B

D C

Flow duration curve

Flow duration curve

Figure 1. The QPPQ method used in the Baseline Streamflow Estimator (BaSE) showing, A, observed 

daily mean streamflow at a reference streamgage, B, flow duration curve at the reference streamgage, 

C, constructed flow duration curve at the ungaged location, and, D, estimated daily mean streamflow at 

the ungaged location. (Modified from Archfield and others, 2010)

specified streamflows are equaled or exceeded (Searcy, 1959). 

It is constructed by arranging observed streamflow values for a 

given period of time by magnitude and the percentage of time 

observed daily streamflow values equaled or exceeded a specific streamflow. For this report, the percentage of time that the 

streamflow is equaled or exceeded is “exceedance probability” 

and is used when discussing statistics. An individual exceedance probability is “percentile” for this report and is used 

when discussing methodology associated with a generic FDC. 

The FDC for an ungaged location is constructed from 

estimates of streamflow for 17 percentiles. Streamflow is 

estimated for each of the 17 percentiles by use of regression 

equations developed using basin characteristics and streamflow data from a subset of reference streamgages. Streamflow for all other percentiles is determined by interpolation. 

Interpolation of streamflow between exceedance probabilities 

determined from the 17 regression equations yields a continuous daily hydrograph consisting of 17,898 streamflow values 

(one value for each day in water years 1960–2008) for the 

ungaged location.

A critical consideration in estimating baseline daily mean 

streamflow is the selection of the reference streamgage that 

results in the best estimate of daily streamflow at the ungaged 

location. Selection of a reference streamgage is performed 

using map correlation (Archfield and others, 2010; Archfield and Vogel, 2010). Map correlation is a geostatistical 

procedure for determining the streamgage with streamflow 

that exhibits the strongest correlation with streamflow at an 

ungaged location.

Reference Streamgages in Pennsylvania and 

Surrounding States

A reference streamgage constitutes a composite of the 

upstream land cover, geology, and hydrologic characteristics 

and can be used to represent ungaged basins with similar characteristics. Reference streamgages are used by water-resource 

managers for a variety of purposes, including regulatory decisions, drought and flood forecasting, and long-term baseline 
4 Estimation of Baseline Daily Mean Streamflows for Ungaged Locations on Pennsylvania Streams, WY 1960–2008

data collection. Data on observed streamflows at reference 

streamgages are used in this analysis to develop regression 

equations for estimating exceedance probabilities and for 

development of correlation maps.

Criteria

Reference streamgages selected for this baseline analysis had streamflow that was minimally altered by regulation, 

diversion, or mining, and other anthropogenic activities, and 

had at least 10 years of continuous record; however, one 

streamgage with 8 years of record was included to increase 

spatial coverage. Most of the streamgages (152) had 15 or 

more years of record; the average number of years of record 

is 46 years. Substantial regulation for this analysis is represented by upstream reservoir impoundments that control 

at least 10 percent of the contributing drainage area at the 

streamgage. Streamgages with questionable regulation were 

further evaluated graphically by comparing the range and 

median of the streamflows before and after construction of 

the impoundment and were evaluated statistically by using a 

two-sample Kolmogorov-Smirnov goodness of fit test (TIBCO 

Software Inc., 2008). For streamgages with at least 10 years of 

unregulated flow data recorded before the impoundment was 

constructed, only the period prior to the start of regulation was 

used in the analysis. Information on diversions and mining 

affects were obtained from USGS Annual Water Data Reports, 

available on-line only since 2006 at http://wdr.water.usgs.gov/

and in paper format prior to 2006 on file at the USGS Pennsylvania Water Science Center. There were 168 streamgages that 

potentially met the above criteria—143 in Pennsylvania, 10 in 

New York, 6 in Maryland, 2 in West Virginia, and 7 in Ohio 

(fig. 2). A complete listing of streamgages used in the analysis 

is presented in appendix 1.

The percentage of impervious area within a basin was 

used to limit the number of streamgages with potential 

anthropogenic effects on streamflow. However, in large urban/

suburban areas, such as in the southeastern part of the State, 

some streamgages with a high percentage of impervious area 

were retained for improved spatial coverage. The average 

percentage of impervious area for the streamgages selected for 

the analysis is 2.5; with a maximum of 29 percent allowed in 

southeastern Pennsylvania. 

Water use in Pennsylvania, including registered 

withdrawals, estimated withdrawals, and discharges for 

2003 (Stuckey, 2008), were used to evaluate the selected 

streamgages. Because of uncertainties associated with the 

water-use data, including lack of verification or adjustment for 

storage, pass-by flows, or other drought-specific requirements, 

the data were not used independently to exclude streamgages 

but rather as a check of streamgages that exhibited unusual 

streamflow characteristics. The net water use (total discharges 

– total withdrawals) normalized to the drainage area associated 

with the selected streamgages within Pennsylvania is shown 

in figure 3. Positive values in the normalized net water use 

indicate more water is being returned to the basin than is being 

withdrawn, either through discharges, such as wastewatersewage-treatment plants, or importation of water from outside 

the basin. Negative values indicate more water is being withdrawn for multiple purposes or being exported out of the basin 

than is being returned. Streamgages in the combined Upper 

and Lower Delaware River Basins had the highest normalized water use per square mile overall with more water being 

consumed or exported in the Upper Delaware River Basin 

and more water being discharged or imported in the Lower 

Delaware (fig. 3).

Record Extension

Estimation of daily mean streamflow using the QPPQ 

method for WY 1960 to 2008 for any ungaged stream location 

requires that all reference streamgages have a complete daily 

streamflow record for the same period. Of the selected reference streamgages, 67 had a complete record with unregulated 

flow for WY 1960 to 2008. The remaining streamgages had 

record lengths of 8 to 48 years. Streamflow records shorter 

than 49 years were extended to complete the 1960–2008 WY 

period using the Streamflow Record Extension Facilitator 

(SREF) (Granato, 2009). The average number of incomplete 

years of record during WY 1960–2008 that required record 

extension was 25 years, with a range of 1 year to 44 years. No 

estimated streamflow data from the record extension analysis 

were used in the development of regression equations or correlation maps.

The methodology used for the SREF relies on the 

assumption that long-term streamflow records from hydrologically similar streamgages can be used to estimate a missing 

record at a streamgage of interest (Granato, 2009). The SREF 

program produces estimated daily mean streamflow for the 

purpose of extending or augmenting the streamflow record 

at streamgages with limited data (Granato, 2009). Record 

extension in SREF uses the line of organic correlation (LOC) 

regression as part of a maintenance of variance (MOVE) 

method. A valuable characteristic of the LOC for streamflow 

record extension is the prediction of flows with variance and 

probability distribution that can closely estimate those of the 

observed record (Helsel and Hirsch, 1992, p. 276–278). The 

MOVE.1 method (Hirsch, 1982, Vogel and Stedinger, 1985) 

was used for this analysis.

The streamflows were log transformed prior to LOC 

regression. This transformation resulted in undefined logarithms when zero-flow values were present. SREF offers 

four options to address zero flows in the streamflow record. 

Three of the options substitute constants for zero-flow days. 

The fourth option, and the one selected for this application, 

applies a streamflow-recession constant beginning with the 

last nonzero streamflow value prior to the zero-flow sequence. 

This procedure creates a series of streamflow values that 

decrease with each successive zero-flow day. This option was 

chosen to avoid imposing an arbitrary constant flow value 

over a potentially substantial period of low-flow values that 

would result in a flatline hydrograph for streamgages at their 
Estimation of Baseline Daily Mean Streamflow 

5

Figure 2. Location of U.S. Geological Survey reference streamgages in and near Pennsylvania.

Lake Erie

81° 80° 79° 78° 77° 76° 75°

42°

41°

40°

39°

Base from U.S. Geological Survey 1:2,000,000 and 1:100,000 digital data

NEW JERSEY

NEW YORK

PENNSYLVANIA

VIRGINIA

MARYLAND

DISTRICT OF

COLUMBIA

DELAWARE

WEST VIRGINIA

OHIO

EXPLANATION

U.S. Geological Survey streamgage watershedState boundaryMajor streamU.S. Geological Survey streamgage

0 10 20 30 40 50 MILES

0 10 20 30 40 50 KILOMETERS
6 Estimation of Baseline Daily Mean Streamflows for Ungaged Locations on Pennsylvania Streams, WY 1960–2008 Lake Erie 80° 79° 78° 77° 76° 75° 42° 41° 40° NEW JERSEY NEW YORK PENNSYLVANIA VIRGINIA WEST VIRGINIA MARYLAND DELAWARE

OHIO

Base from U.S. Geological Survey 1:2,000,000 and 1:100,000 digital data

EXPLANATION

Major basins

AlleghenyGreat Lakes

Lower DelawareLower Susquehanna

Upper DelawareWest Branch Susquehanna

Monogahela

North Branch SusquehannaOhioPotomac

Normalized net water use, in million gallons per day per square mile

-0.13 – -0.10>-0.10 – -0.01>-0.01 – 0.01

>0.01 – 0.10>0.10 – 0.16

State boundaryMajor stream

0 10 20 30 40 50 MILES0 10 20 30 40 50 KILOMETERS

Figure 3. Normalized net water use in selected U.S. Geological Survey streamgage basins in Pennsylvania, 2003. (>, greater than)
Estimation of Baseline Daily Mean Streamflow 7

zero-flow threshold. For example, in an upstream-downstream 

pairing, streamflow at the downstream streamgage, although 

strongly correlated with the upstream streamgage, does not 

recede to zero flow as quickly or as often owing to a larger 

drainage area. The daily rate of decrease is determined by the 

streamflow-recession constant and ranges from 0 to 1. On the 

basis of a sampling of low-flow recession rates for the reference streamgages, a recession constant of 0.9 was selected. 

The streamgages used to extend the record of a 

streamgage with an incomplete period of record during 

WY 1960–2008 are termed “index streamgages.” Ten years 

was considered the minimum streamflow record length for 

an acceptable application of MOVE.1. Eleven reference 

streamgages had 10-year periods of record of observed streamflows or less during WY 1960–2008. For those streamgages, 

a period of record from 1950 to 2008 was used to obtain the 

requisite 10 years of concurrent observed streamflows. After 

the streamflow record extensions were completed, records 

were trimmed back to the 1960 to 2008 period. A maximum of 

three streamgages was used for record extension (appendix 2). 

Selection of index streamgages was based on period of available concurrent record, strength of correlation, and distribution of LOC residuals. The concurrent records were evaluated 

graphically and statistically using correlations and the R2

statistic to ensure a good fit between the index streamgage 

and a streamgage with an incomplete period of record. Record 

extension correlations ranged from 0.75 to 0.98, with a mean 

of 0.92. A listing of streamgages with record extension techniques applied is provided in appendix 2.

Regression Equations for Estimating FlowDuration Exceedance Probabilities

Regression equations were developed for 17 percentiles 

along the FDC using observed streamflow data from 162 of 

the 168 reference streamgages in Pennsylvania and surrounding states from the beginning of observed record through the 

2008 WY (appendix 1). Values for basin characteristics with 

possible effects on a range of streamflow, such as land cover 

and soil properties, were determined for the streamgages, and 

exceedance probabilities were computed for the streamgages 

using the entire period of unregulated flow. The observed 

exceedance probabilities (dependent variable) were related to 

the basin characteristics (independent or explanatory variables) using regression techniques.

Streamgages and Basin Characteristics Used in 

Regression Analysis

Daily streamflow values for the selected streamgages 

were retrieved from the National Water Information System (NWIS) web application (http://waterdata.usgs.gov/

nwis) using the program Get NWIS WEB Streamflow Files 

(GNWISQ) (Granato, 2009). This program allows for batch 

downloads from NWISweb and formats the retrieved files for 

further analysis. After the downloaded data were reviewed 

for completeness and accuracy, the data were entered into 

the Make Plotting Position File (MkPP) (Granato, 2009) to 

compute the flow-duration exceedance probabilities. The 

Weibull plotting position option was used. Only the period of 

record for observed unregulated flow at the streamgage was 

used to compute the exceedance probabilities for use in the 

regression analysis. 

A list of 28 climatologic, geologic, hydrologic, and 

physiographic basin characteristics with possible effects on a 

range of streamflows was compiled from various geographic 

information system (GIS) sources (table 1). Only basin characteristics derived using GIS methods were evaluated during the 

regression analysis. The use of GIS-derived basin characteristics improves the consistency, reproducibility, and ease-of-use 

of the resulting regression equations. Many of the basin characteristics evaluated were used in previous regression analyses 

(Stuckey, 2006; Roland and Stuckey, 2008; Risser and others, 

2008) and can be determined using the StreamStats web application for Pennsylvania (Stuckey and Hoffman, 2010).

Regression Analysis and Resulting FlowDuration Exceedance Probability Regression 

Equations

The exceedance probabilities for observed streamflows 

were related to basin characteristics using exploratory ordinary 

least squares (OLS) and weighted least squares (WLS) regression techniques. The exceedance probabilities were weighted 

using the following expression for the WLS regression 

techniques to account for different periods of record: (number 

of years of record at streamgage × number of streamgages) / 

sum of years of record of all streamgages. Regression iterations were performed using the statistical package Spotfire S+ 

(TIBCO Software Inc., 2008). Regression diagnostics used to 

evaluate the resulting regressions include graphical relations, 

multicollinearity, prediction error sum of squares (PRESS) 

statistic, standard error, and coefficient of determination (R2) 

(Helsel and Hirsch, 1992, p. 245–253; p. 300–315).

Data from 162 streamgages in and near Pennsylvania 

were used to develop regression equations for estimating the 

1-, 5-, 10-, 15-, 20-, 30-, 40-, 50-, 60-, 70-, 80-, 85-, 90-, 95-, 

and 99-percent exceedance probabilities (P1, P5, P10, P15, 

P20, P30, P40, P50, P60, P70, P80, P90, P95, and P99, respectively). Two additional regression equations were developed 

for the 0.0056- and 99.9944-percent flow-duration exceedances (P0.0056 and P99.9944, respectively) to represent the 

ends of the FDC for the period from 1960 to 2008 (49 years). 

Because only observed data were used in the regression analysis, the streamgages used to develop the regression equations 

for the lower and upper ends of the FDC were limited to those 

with at least 49 years of record. As a result, 67 streamgages 
8 Estimation of Baseline Daily Mean Streamflows for Ungaged Locations on Pennsylvania Streams, WY 1960–2008

Table 1. Basin characteristics used in the development of regression equations for flow-duration exceedance probabilities for 

Pennsylvania streams.—Continued

Basin characteristic Source Reference

Basin slope (degrees) Digital Elevation Model (DEM) U.S. Geological Survey (2000a)

Mean basin elevation (feet) Digital Elevation Model (DEM) U.S. Geological Survey (2000a)

Forested (percent of basin area) National Land Cover Dataset (NLCD); and 

enhanced version (NLCDe) 

Homer and others (2004); Price and others 

(2003)

Glaciated (percent of basin area) From modified geology maps 

Pennsylvania Dept. of Conservation and 

Natural Resources (1997); Environmental 

Resources Research Institute (1996)

Lakes and open water (percent of basin 

area) 

National Land Cover Dataset (NLCD); and 

enhanced version (NLCDe); digitized from 

USGS quadrangle maps 1:24000 scale

Homer and others (2004); Price and others 

(2003) 

Longest drainage path (mile) National Hydrography Dataset (NHD), 

1:24000 scale U.S. Geological Survey (2000b)

Stream density (length mile/basin area 

square miles)

National Hydrography Dataset (NHD), 

1:24000 scale U.S. Geological Survey (2000b)

Channel slope (feet per mile) Digital Elevation Model (DEM) U.S. Geological Survey (2000a)

Soil infiltration index (unit less 1=well to 

4=poor) State Soil Geographic (STATSGO) database U.S. Department of Agriculture (1994)

Mean annual precipitation, 1971–2000 

(inches)

Parameter-elevation Regressions on 

Independent Slopes Model (PRISM) Daly (1996)

Drainage area (square mile) Digital Elevation Model (DEM) U.S. Geological Survey (2000a)

Soil depth to bedrock (feet) State Soil Geographic (STATSGO) database U.S. Department of Agriculture (1994)

Drainage runoff number (unit less 1=well 

to 7=poor) State Soil Geographic (STATSGO) database U.S. Department of Agriculture (1994)

Soil available water content (percent) State Soil Geographic (STATSGO) database U.S. Department of Agriculture (1994)

Soil permeability (inches per hour) State Soil Geographic (STATSGO) database U.S. Department of Agriculture (1994)
Estimation of Baseline Daily Mean Streamflow 9

Table 1. Basin characteristics used in the development of regression equations for flow-duration exceedance probabilities for 

Pennsylvania streams.—Continued

Basin characteristic Source Reference

Urbanized area (percent of basin area) National Land Cover Dataset (NLCD); and 

enhanced version (NLCDe)

Homer and others (2004); Price and others 

(2003)

Residential area (percent of basin area) National Land Cover Dataset enhanced 

version (NLCDe) Price and others (2003)

Mined area (percent of basin area) National Land Cover Dataset enhanced 

version (NLCDe) Price and others (2003)

Commercial, industrial, and transportation 

area (percent of basin area)

National Land Cover Dataset enhanced 

version (NLCDe) Price and others (2003)

Wetlands (percent of basin area) National Land Cover Dataset (NLCD); and 

enhanced version (NLCDe) 

Homer and others (2004); Price and others 

(2003)

Mean basin elevation minus minimum 

elevation (feet) Digital Elevation Model (DEM) U.S. Geological Survey (2000a) 

Shape factor (unitless) is a measure of the 

shape of a basin computed as the ratio of 

length of the basin to its computed area

Digital Elevation Model (DEM) U.S. Geological Survey (2000a)

Carbonate bedrock (percent of basin area) From modified geology maps

Pennsylvania Dept. of Conservation and 

Natural Resources (1997); Environmental 

Resources Research Institute (1996)

Impervious surface area (percent of basin 

area) National Land Cover Dataset (NLCD) Homer and others (2004)

Mean maximum daily temperature, 1971-

2000 (degrees Fahrenheit)

Parameter-elevation Regressions on 

Independent Slopes Model (PRISM) Daly (1996)

Longitude and latitude of basin outlet 

(decimal degrees)

Latitude and latitude of basin centroid 

(decimal degrees)

Percentage of sand in soil State Soil Geographic (STATSGO) database U.S. Department of Agriculture (1994)

1

Referred to as soil thickness in report by Stuckey (2006)
10 Estimation of Baseline Daily Mean Streamflows for Ungaged Locations on Pennsylvania Streams, WY 1960–2008

with sufficient period of record were used to develop regression equations for estimating the P0.0056 and P99.9944 

exceedance probabilities. Outliers and streamgages with high 

leverage and (or) influence were removed from individual 

regression analysis only if sufficient data or information was 

found to support the removal of the streamgages, such as high 

water use in the basin (including withdrawals and discharges), 

abnormal basin characteristics or streamflow, or poor or 

estimated daily streamflow computations during low- or 

high-flow periods.

The possibility of dividing the State into regions was 

evaluated during exploratory regression analysis using OLS 

and WLS. Basic statewide regression equations were initially developed, and residual standard errors were mapped 

to determine if regionalization was appropriate. Although 

no pattern was observed in the residuals, previously defined 

low-flow and peak-flow regions (Stuckey, 2006; Roland and 

Stuckey, 2008) were used to regionalize the State during the 

exploratory regression analysis to possibly improve regression diagnostics. The resulting standard errors, coefficient 

of determination (R2), residuals, PRESS statistic, and other 

regression diagnostics were compared to the statewide initial 

regression equations. The exploratory regressions resulting 

from using previously defined low-flow regions lowered the 

standard error of prediction for the lower exceedance probabilities but increased the standard error of prediction for the 

higher exceedance probabilities. There was no noticeable 

improvement in error when using the previously defined peakflow regions. The statewide regression equations consistently 

produced a range of the exceedance probabilities with more 

accuracy than regression equations using either set of regions. 

Also an attempt was made to create new regions on the basis 

of the statewide residuals, hydrologic unit code (HUC) 8 

boundaries, physiographic provinces, and (or) major basins, 

but no overall improvement was noted. As a result, regression 

equations for the suite of exceedance probabilities were developed on a statewide scale. WLS was used to generate the final 

statewide regression equations.

The following independent variables were found to be 

significant at the 95-percent confidence level for one or more 

regression equations: longitude at the outlet, drainage area, 

mean annual precipitation, mean maximum daily temperature, 

depth to bedrock, drainage runoff number, and percentages of 

carbonate bedrock and impervious surface area (table 2). The 

basin characteristics values associated with the streamgages 

used in the analysis are listed in appendix 3. To form a nearlinear relation between the flow-duration exceedance probabilities and basin characteristics, all independent and dependent 

variables were log-transformed (base 10) prior to regression 

analysis. Because percentages can have a value of zero, 1.0 

was added to the decimal form of the percentages of carbonate 

bedrock and impervious surface area.

The regression model took the following form, in 

log units:

logQp = A + blog Long + c log DA + d logPpt +

elog MaxT + f logThk + glog Drn +

hlog(1+ 0.01× Carb)+ ilog(1+ 0.01× Imp)

or in arithmetic space:

Qp = A b c d e f g +

× h + × i 0.01 Carb) (1 0.01 Imp) ,

10 (Long) (DA) (Ppt) (MaxT ) (Thk) (Drn) (1

where

 Log = log to base 10;

 = flow-duration exceedance probability, 

in cubic feet per second;

 A = the intercept;

 Long = longitude of the outlet of the basin, 

in decimal degrees;

 DA = drainage area, in square miles;

 Ppt = mean annual precipitation, in inches;

 MaxT = mean maximum daily temperature, 

in degrees Fahrenheit;

 Thk = soil depth to bedrock, in feet;

 Drn = drainage runoff number, unitless;

 Carb = basin underlain by carbonate bedrock, 

in percent; 

 Imp = impervious surface area in basin, 

in percent; and

 b, c, d, e, f, g, h, and i = independent variable coefficients 

of regression estimated by WLS.

Qp

Standard errors of prediction for the regression equations 

provide an estimate of reliability of the predicted exceedance 

probabilities (table 2) (Helsel and Hirsch, 1992, p.35). The 

standard error of prediction for the flow-duration exceedance 

probability regression equation ranged from 0.05 to 0.34 in log 

units (11 percent to 92 percent; table 2); mean standard error 

over the entire suite of flow-duration equations equals 31 percent. The regression equations used to estimate the lower ends 

of the FDC have the highest errors; the extreme low-flow 

exceedance probability of P99.9944 has an error of 92 percent, 

and P99 and P95 have errors of 64 percent and 47 percent, 

respectively. For comparison, the most recent regression equations developed for estimating the 7-day, 10-year low flow for 

streams in Pennsylvania have errors ranging from 51 percent 

to 66 percent (Stuckey, 2006). The coefficient of determination (R2

) provides a way of estimating the uncertainty associated with the regression. For example, the R2

 for P60 is 0.97, 

indicating the basin characteristics selected for use in the P60 

regression equation describe about 97 percent of the influence 

that all basin characteristics have on predicting the 60-percent 
Estimation of Baseline Daily Mean Streamflow 11

Table 2. Regression coefficients for use with flow-duration exceedance probability regression equations for Pennsylvania streams.[--, basin characteristic not significant]

Flow duration 

exceedance Intercept

Basin characteristic coefficients

Coefficient of 

determination 

(R2)

Standard error 

of prediction

Longitude Drainage area Mean annual precipitation

Mean 

maximum 

daily 

temperature

Depth to 

bedrock

Drainage 

runoff 

number

Percent 

carbonate 

bedrock

Percent 

Impervious 

Area

Log units Percent

P0.0056 19.4870 -9.2666 0.9467 -- -- -- -- -1.0541 -- 0.93 0.12 29P1 1.3859 -- 0.9790 0.8532 -0.9410 -- -- -1.1890 -- 0.98 0.07 16P5 2.3635 -- 1.0174 1.2290 -2.0862 -- -- -0.8718 -- 0.99 0.05 12P10 3.0648 -- 1.0320 1.5437 -2.9012 -- -- -0.5003 -- 0.99 0.05 11P15 3.1570 -- 1.0351 1.7714 -3.2373 -- -- -0.2491 -- 0.99 0.05 11P20 3.7262 -- 1.0348 2.0031 -3.7308 -- -0.3174 -- -- 0.99 0.05 12P30 2.9371 -- 1.0288 2.3264 -3.6074 -- -0.4800 -- -- 0.99 0.06 13P40 4.4846 -2.2014 1.0289 2.5671 -2.5667 -- -- -- -- 0.99 0.07 17P50 6.4550 -3.8133 1.0312 2.8468 -2.2881 -- -- -- -- 0.98 0.09 21P60 4.3767 -5.0540 1.0339 2.8911 -- 0.7184 -0.5143 -- -0.4900 0.97 0.11 25P70 8.5970 -7.5624 1.0578 3.0510 -- 1.2641 -1.0775 -- 0.4131 0.96 0.13 31P80 11.8916 -9.4846 1.0773 3.0311 -- 1.9057 -1.5886 -- 1.6540 0.94 0.15 37P85 12.5831 -9.8562 1.0783 2.8778 -- 2.2722 -1.7499 -- 2.4188 0.93 0.17 40P90 12.8246 -10.2618 1.0927 3.0113 -- 2.6396 -1.9053 -- 3.0786 0.92 0.19 46P95 14.8563 -11.1128 1.0950 2.6659 -- 3.0603 -2.4097 -- 3.3086 0.92 0.19 47P99 16.5197 -12.3238 1.1478 2.6429 -- 4.2131 -3.2166 -- 5.1089 0.88 0.25 64P99.9944 16.5036 -12.9899 1.1441 3.1975 -- 5.8935 -5.0895 -- -- 0.75 0.34 92
12 Estimation of Baseline Daily Mean Streamflows for Ungaged Locations on Pennsylvania Streams, WY 1960–2008

exceedance value (table 2). A lower R2 for P99.9944 (0.75) 

indicates that additional variables may help to better define 

this extreme low-flow prediction. Flow-duration exceedance 

probabilities computed from streamflow data (observed) and 

regression equations (predicted) for streamgages used in the 

regression analysis can be found in appendix 4. 

Selection of Reference Streamgages for 

Estimating Baseline Daily Mean Streamflow

An important consideration in applying the QPPQ 

method is the selection of a reference streamgage. A typical 

approach has been to select the closest reference streamgage 

to the ungaged location as the preferred reference gage. 

Choosing the closest streamgage as the most appropriate 

(best) reference streamgage is based on the assumption that 

similarity in the conditions determining streamflow increases 

with decreasing distance between two locations. However, 

there are many instances where conditions at the closest 

streamgage are neither physically or hydrologically similar 

to those at the ungaged location. Archfield and Vogel (2010) 

showed that the closest reference streamgage is not always the 

best choice and introduced the map correlation method as an 

alternative.

Map Correlation

Map correlation is a geostatistical approach to selecting 

a reference streamgage where streamflow exhibits the strongest correlation with that at an ungaged location. First, each 

reference streamgage is assigned a unique map of correlation 

estimate developed from a model of the spatial correlation 

structure, or variogram, between it and all other available 

reference streamgages in Pennsylvania and surrounding states 

(fig. 4). Ordinary kriging (Isaaks and Srivastava, 1989) is used 

to estimate the expected correlation at the ungaged location.

Selecting the most appropriate (best) reference 

streamgage is accomplished by choosing the streamgage 

whose map has the highest correlation coefficient at the 

coordinates of the ungaged location. Map correlation may be a 

unique application of geostatistical models in that many models need to be compared as part of the reference streamgage 

selection process. Selecting the best model is, therefore, 

dependent in part on all models being fit in a consistent manner to avoid biasing one or more models. Variogram model fitting can involve a substantial amount of trial and error (Isaaks 

and Srivastava, 1989; Archfield and Vogel, 2010) and subjectivity as well. When the models are fit interactively, it is likely 

to result in many parameters having few similarities. One 

model may perform better than another simply because more 

time was given to finding the best parameters. Considering 

the small differences in correlation coefficients among many 

reference streamgages, minimization of subjectivity in model 

fitting is an important consideration. In an attempt to minimize subjectivity, the variogram models were developed in 

the Geostatistical Analyst extension in ArcMAP 9.3 (Environmental Systems Research Institute, Inc., 2009) using default 

automated parameter estimation. 

Application of Map Correlation in Two Pilot Basins

The map correlation method was originally developed 

using streamflow data from streamgages in and near Massachusetts and had not been previously tested for use in Pennsylvania. Because of this, the map correlation method was 

applied and evaluated for two pilot basins situated primarily in 

Pennsylvania (fig. 5) in anticipation of extending map correlation to the entire State and as a means of exploring possible 

improvements to the method. The objective of the pilot basin 

analysis was to compare the relative efficiency of the widely 

used closest streamgage method to the map correlation method 

as used by Archfield and others (2010) and to determine if 

modifications could improve the method’s use in Pennsylvania. Pennsylvania is hydrologically diverse, in large part, 

because of its varied geology and topography. The first pilot 

basin, Lower Susquehanna River Basin, is located in southcentral Pennsylvania and northern Maryland and is bounded 

by HUC 020503. The Lower Susquehanna River Basin covers 

approximately 9,200 square miles (mi2)in the Susquehanna 

River Basin. Twenty USGS streamgages within HUC 020503 

were selected as reference gages (table 3). The second pilot 

basin, the Upper Delaware River Basin, is bounded by HUC 

020401 and drains approximately 6,900 mi2 of the Delaware 

River Basin in parts of New York, New Jersey, and Pennsylvania. Eighteen reference streamgages were selected within 

HUC 020401 (table 3). The reference streamgages selected 

had minimally altered hydrology from human activities. The 

period of available daily streamflow record ranged from 13 to 

59 years.

The modifications to Archfield and others (2010) method, 

applied for the pilot basins in Pennsylvania, include (1) using 

Spearman’s rho in place of Pearson’s r for streamflow correlations, (2) using basin centroid locations in place of basin outlet 

locations when defining correlation models, and (3) adding 

anisotropy parameters to the correlation models. For this 

analysis, anisotropy is measured by observing the directional 

orientation in the shape of stream basins and stream channels.

Correlation Metrics 

The map correlation method defines a spatial correlation structure of daily streamflow among a set of reference 

streamgages. Archfield and others (2010) chose Pearson’s r of 

the logarithms of daily streamflow at reference streamgages 

as the correlation metric. Pearson’s r is a parametric measure of the linear association between two variables (Helsel 

and Hirsch, 1992, p.218–219). It assumes a bivariate normal 

distribution, is sensitive to outliers, and is insensitive to strong 

associations that are nonlinear. Daily streamflow data generally follow a lognormal distribution, and taking the logarithms 

prior to computing Pearson’s r improves the results as Archfield and others (2010) noted. 
Estimation of Baseline Daily Mean Streamflow 13

Lake Erie

80° 79° 78° 77° 76° 75°

42°

41°

40°

NEW

JERSEY

NEW YORK

PENNSYLVANIA

VIRGINIA

MARYLAND DELAWARE

OHIO

Base from U.S. Geological Survey 1:2,000,000 and 1:100,000 digital data

01560000

01562000

01564500

01550000

01559000

01557500

01556500 01558000

01565000 01565700

01566000

01567500 01568000

01570000 01571500

01555500

01574500

EXPLANATION

Correlation coefficient

0.65 – 0.70

>0.70 – 0.75

>0.75 – 0.80

>0.80 – 0.85

>0.85 – 0.90

>0.90 – 0.95

>0.95 – 1.00

01568000 U.S. Geological Survey

streamgage and number

0 10 20 30 40 50 MILES

0 10 203040 50 KILOMETERS

Figure 4. Example correlation map for U.S. Geological Survey streamgage 01559000, Juniata River at Huntingdon, Pa. (>, greater than)
14 Estimation of Baseline Daily Mean Streamflows for Ungaged Locations on Pennsylvania Streams, WY 1960–2008 Lake Erie 80° 79° 78° 77° 76° 75° 74° 42° 41° 40° NEW JERSEY NEW YORK PENNSYLVANIA VIRGINIA WEST VIRGINIA MARYLAND DELAWARE

OHIO

01559700

01560000

01562000

01564500

01556000 01559000

01558000 01556500

01557500

01555000

01555500 01565700

01566000

01567500 01568000

01570000 01571500

01576754

01574500

01459500

01452500

01439500

01440400

01442500

01447500

01447720

01448500

01449360

01450500

01452000

01451800

01451500

01439500

01428750

01424001

01423000

01426000

01420500

Base from U.S. Geological Survey 1:2,000,000 and 1:100,000 digital data

0

0 5

Upper Delaware River Basin

EXPLANATION

Lower Susquehana River BasinMajor streamCounty boundary

U.S. Geological Survey streamgageand number

01571500

State boundary

0 10 20 30 40 50 MILES

0 10 20 30 40 50 KILOMETERS

Figure 5. Location of pilot test basins in Pennsylvania and reference streamgages for the map correlation method.
Estimation of Baseline Daily Mean Streamflow 15

Table 3. Description of selected U.S. Geological Survey reference streamgages in the Upper Delaware River Basin and the Lower 

Susquehanna River Basin in Pennsylvania.

[ddmmss, degrees, minutes, seconds; mi2, square miles]

U.S. Geological 

Survey streamgage 

number

Name Latitude 

(ddmmss)

Longitude 

(ddmmss)

Drainage 

area 

(mi2)

Period of record 

Upper Delaware River Basin

0142400103 Trout Creek near Trout Creek, NY 421025 751647 20.2 1952–67, 1996–1999

01420500 Beaver Kill at Cooks Falls, NY 415647 745848 241 1913–2008

01423000 West Branch Delaware River at Walton, NY 420958 750825 332 1950–2008

01426000 Oquaga Creek at Deposit NY 420331 752542 67.6 1941–73, 2004–2005

01428750 West Branch Lackawaxen River near Aldenville, PA 414028 752235 40.6 1987–2002

01439500 Bush Kill at Shoemakers, PA 410517 750217 117 1909–2008

01440400 Brodhead Creek near Analomink, PA 410505 751254 65.9 1958–2008

01442500 Brodhead Creek at Minisink Hills, PA 405955 750835 259 1950–2008

01447500 Lehigh River at Stoddartsville, PA 410749 753733 91.7 1944–2008

01447720 Tobyhanna Creek near Blakeslee, PA 410505 753621 118 1961–1984

01448500 Dilldown Creek near Long Pond, PA 410208 753237 2.39 1949–1996

01449360 Pohopoco Creek at Kresgeville, PA 405351 753010 49.9 1966–2008

01450500 Aquashicola Creek at Palmerton, PA 404822 753554 76.7 1939–2008

01451500 Little Lehigh Creek near Allentown, PA 403456 752900 80.8 1946–2008

01451800 Jordan Creek near Schnecksville, PA 403942 753738 53.0 1966–2008

01452000 Jordan Creek at Allentown, PA 403723 752858 75.8 1945–2008

01452500 Monocacy Creek at Bethlehem, PA 403828 752247 44.5 1948–2008

01459500 Tohickon Creek near Pipersville, PA 402601 750701 97.4 1937–1973

Lower Susquehanna River Basin

01555000 Penns Creek at Penns Creek, PA 405200 770255 301 1930–2008

01555500 East Mahantango Creek near Dalmatia, PA 403640 765444 162 1930–2008

01556000 Frankstown Br Juniata River at Williamsburg, PA 402747 781200 291 1917–2008

01556500 Little Juniata River at Tipton, PA 403740 781738 93.7 1946–1962

01557500 Bald Eagle Creek at Tyrone, PA 404101 781402 44.1 1953–2008

01558000 Little Juniata River at Spruce Creek, PA 403645 780827 220 1939–2008

01559000 Juniata River at Huntingdon, PA 402905 780109 816 1942–2008

01559700 Sulphur Springs Creek near Manns Choice, PA 395840 783708 5.28 1962–1978

01560000 Dunning Creek at Belden, PA 400418 782934 172 1939–2008

01562000 Raystown Branch Juniata River at Saxton, PA 401257 781556 756 1912–2008

01564500 Aughwick Creek near Three Springs, PA 401245 775532 205 1938–2008

01565000 Kishacoquillas Creek at Reedsville, PA 403917 773500 164 1940–70, 1984–85, 2001–2008

01565700 Little Lost Creek at Oakland Mills, PA 403619 771842 6.52 1964–1981

01566000 Tuscarora Creek near Port Royal, PA 403055 772510 214 1913–58, 2002–2008

01567500 Bixler Run near Loysville, PA 402215 772409 15.0 1954–2008

01568000 Sherman Creek at Shermans Dale, PA 401924 771009 207 1930–2008

01570000 Conodoguinet Creek near Hogestown, PA 401508 770117 470 1930–58, 1967–2008

01571500 Yellow Breeches Creek near Camp Hill, PA 401329 765354 216 1954–2008

01574500 Codorus Creek at Spring Grove, PA 395243 765113 75.5 1929–1964

01576754 Conestoga River at Conestoga, PA 395647 762205 470 1985–2002
16 Estimation of Baseline Daily Mean Streamflows for Ungaged Locations on Pennsylvania Streams, WY 1960–2008

Although it is straightforward to compute Pearson’s 

r of the logarithm of streamflow, Pearson’s r for several 

reasons may not be an optimal choice when the map correlation method is used in conjunction with the QPPQ method. 

First, measuring the correlation of FDC percentiles directly 

may improve the results. When applied as part of the QPPQ 

method, the Pearson’s r correlation of log transformed 

streamflow functions acts as a surrogate for the correlation 

of FDC percentiles between the ungaged and reference gage 

locations. The QPPQ method relies on the assumption of 

equivalence of percentiles between an ungaged location and 

a reference streamgage (Waldron and Archfield, 2006) and 

measures equivalence in the relation between streamflows. 

Second, Pearson’s r is a measure of a linear association 

(Helsel and Hirsh, 1992, p. 218–219) and daily mean streamflow seldom fit a log normal distribution exactly. Records 

from different streamgages often yield non-linear correlations 

with a poor Pearson’s r. The relation between streamflow 

at different streamgages does not need to be linear, but can 

have a strong rank-based correlation. FDCs are typically built 

around rank-based quantiles (Vogel and Fennessey, 1994; 

Helsel and Hirsch, 1992). In many instances FDC exceedance values are calculated using a formula derived from the 

general form

p = (i – a) / (n + 1 – 2a) ,

where 

p = flow-duration exceedance probability,

i = rank of an observation, 

a = constant, and 

n = number of observations.

Given that a and n are constants for a specific FDC, p

will retain the rank order of the observations. As a result, the 

association between FDCs is equivalent to a streamflow rankorder correlation. 

A third issue is the occurrence of undefined logarithms 

when zero streamflow values are present. A common but 

less than desirable work-around is replacing the undefined 

logarithms with a small value. For the pilot basin analyses, 

0.001 cubic feet per second was substituted for zero streamflow values when computing logarithms. Archfield and Vogel 

(2010) reported that Kendall’s tau, a non-parametric rankbased correlation coefficient, could be used as alternative to 

Pearson’s r in areas with zero streamflow values, therefore, 

eliminating undefined logarithims. Although Kendall’s tau

is widely applied in hydrology, Spearman’s rho is another 

non-parametric measure of correlation that can be used. 

Spearman’s rho is similar in derivation and scale to Pearson’s r, whereas Kendall’s tau yields a smaller coefficient 

for most correlations (Helsel and Hirsch, 1992, p. 212–218). 

Although both Kendall’s tau and Spearman’s rho handle zero 

streamflow values and monotonic associations, they present 

different fits to the data. During exploratory analysis, it was 

found that Spearman’s rho exhibits a more linear association 

with distance than Kendall’s tau when the value is greater 

than about 0.7. A linear correlation to distance relation is 

advantageous when fitting a variogram model of the spatial 

correlation. 

Distance Metrics

Archfield and Vogel (2010) applied ordinary kriging with 

a spherical variogram model to estimate cross-correlations 

of daily streamflows between a reference streamgage and 

ungaged locations anywhere within a study area. Those estimates are based on Euclidean distances between basin outlets 

(streamgage locations) at the reference and ungaged locations. 

Huang and Yang (1998) and Skoien and Blöschl (2007) use 

the centroid of the basin area for distance measures. They 

note that streamflow at a basin outlet actually represents local 

streamflows integrated over the entire basin area and imply 

that the centroid location better represents the basin area. 

Centroid distances were examined and compared for their 

performance in identifying the best reference gage in the map 

correlation method.

Anisotropy

The directional orientation observed in the shape of 

stream basins and stream channels is “anisotropy” and can 

be mirrored in the correlation of streamflow at streamgages 

located in the basin. Streamgages located along the same 

reach share the same directional orientation and exhibit higher 

magnitudes of correlation between streamflow and persistence of correlation with distance than streamgages located 

on different reaches. Streamgages on tributaries intersecting 

the mainstem in an orthogonal orientation are more likely 

to include independent tributary streamflow or streamflow 

similar to that of an adjacent basin. To determine if anisotropy 

information would improve selection of the best correlated 

reference streamgage, an anisotropy component was added to 

the spatial correlation models. Spatial correlation models with 

and without anisotropy were compared to determine whether 

the inclusion of anisotropy improved map correlation in the 

pilot basins. 

Anisotropy parameters were used to define a set of 

orthogonal major and minor axes whose orientation and magnitudes were best fit to corresponding orientation-dependent 

variations in the correlation variograms. The Upper Delaware 

River and Lower Susquehanna River pilot basins trend north 

to south and west to east, respectively. Moreover, the length 

to width ratio and streamflow patterns are quite different. 

For example, the Upper Delaware River pilot basin is four 

times longer than wide, and the mainstem and major tributaries have prominent north to south components (fig. 5). The 

Lower Susquehanna River pilot basin is approximately two 

times longer than wide. Although there is an overall west to 

east orientation, there is great variation in reach orientation, 

and many of the tributaries flow in opposing directions. These 

characteristics indicate stronger anisotropy in the Upper Delaware River pilot basin than in the Lower Susquehanna River 

pilot basin. 
Estimation of Baseline Daily Mean Streamflow 17

Analysis and Results of Map Correlation in Two Pilot 

Basins

The process of selecting the best reference streamgage 

using map correlation in the pilot basins treated each reference streamgage as an ungaged location using a leave-oneout cross-validation procedure. Each reference streamgage 

was removed, in turn, from each variogram dataset, and the 

correlation was estimated for that location. In this way, each 

reference streamgage location represents a sample ungaged 

location. The variogram model whose origin was the sample 

ungaged location was dropped from consideration. Thus, each 

reference streamgage location yielded n – 1 correlation estimates, where n is the number of reference streamgages. 

The pilot basin analysis was intended to answer two 

questions. First, how well did the various map correlation 

models reproduce the correlation coefficients for the reference 

streamgages? Second, how successful was map correlation in 

picking the most correlated reference streamgage? These questions were examined during the multiple trials of map correlation and modifications for the pilot basins.

Direct comparison of the correlation coefficients among 

the trials was not feasible because of computational differences in r and rho. Therefore, the Nash-Sutcliffe (NS) 

efficiency value, suitable for comparisons across the different correlation coefficient types, was used. The NS efficiency 

value ranges from negative infinity to 1. A perfect prediction 

of the observed data yields an efficiency of 1. An efficiency of 

0 indicates predictions no better than the mean of the data. A 

negative efficiency implies the data mean is a better predictor 

than the modeled data because of lower variance. Considering 

that all correlation maps need to perform similarly if the best 

reference streamgage is to be selected consistently, it follows 

that the trial with the highest average and lowest range in 

efficiencies is preferred. 

NS efficiencies for the Lower Susquehanna River pilot 

basin correlation maps were not markedly different among 

the various trials (fig. 6). Median NS efficiencies ranged from 

0.57 to 0.63. Higher efficiencies were observed when the basin 

centroids rather than basin outlets were used to identify reference streamgage locations. Neither Pearson’s r nor Spearman’s 

rho correlations performed consistently better. Map correlation using Spearman’s correlation, in combination with basin 

centroid locations and anisotropy, had the highest median and 

smallest range in efficiency, except for a single outlier. 

NS efficiencies for the Upper Delaware River pilot basin 

were generally lower than those for the Lower Susquehanna 

River pilot basin (fig. 6). Median NS efficiencies ranged from 

0.27 to 0.69. An efficiency advantage was not observed for 

either basin outlet or basin centroid locations. Pearson’s and 

Spearman’s correlations performed similarly well. Anisotropy, 

however, when used with basin centroids resulted in a substantial improvement in efficiencies. Both Pearson’s r and Spearman’s rho correlations with basin centroid distance yielded 

nearly identical median efficiencies of 0.69 and 0.67 when 

combined with anisotropy.

The other question associated with the pilot basin analysis is: How successfully did the map correlation method select 

the most highly correlated streamgage? An initial assumption was that higher NS efficiencies would indicate improved 

chances of selecting the best correlated reference streamgage. 

Higher efficiencies indicate correlation map estimates are 

closer to the observed data. The best correlated reference 

streamgage was determined for each ungaged location by 

-0.5

-1.0

0.0

0.5

1.0

Nash-Sutcliffe efficiency value

Correlation

r rho r rho r rho

Basin outlet Basin centroid

Correlation

r rho r rho r rho

B. Upper Delaware River Basin

Basin outlet Basin centroid Basin centroid with

anisotropy

Basin centroid with

anisotropy

A. Lower Susquehanna River Basin

75th percentile

Outside value—Values are more than

 1.0 times the interquartile range

 from the top to bottom of the box

50th percentile

(median)

25th percentile

Interquartile

range

EXPLANATION

Figure 6. Distribution of Nash-Sutcliffe efficiency values computed from observed and estimated correlations of daily mean 

streamflows at selected U.S. Geological Survey streamgages in, A, the Lower Susquehanna River Basin and, B, the Upper Delaware 

River Basin in Pennsylvania. (r, Pearson’s correlation; rho, Spearman’s correlation)
18 Estimation of Baseline Daily Mean Streamflows for Ungaged Locations on Pennsylvania Streams, WY 1960–2008

selecting the highest correlation value from among all crossvalidation estimates for a selected ungaged location. The 

percentage of time during the map correlation method trials 

that the best correlated streamgage was selected is presented 

in figure 7 along with two closest reference streamgage 

selection methods.

Success rates for selection of the best correlated reference streamgage in the Lower Susquehanna River pilot 

basin ranged from 25 to 60 percent (fig. 7). Map correlation 

performed better than other selection methods when basin 

centroids, Spearman’s correlation, and anisotropy were used. 

Selection of the closest reference streamgage by basin outlet 

was the least successful, but substituting closest basin centroids for basin outlet locations improved the outcome by 

almost double. This trial essentially matched the success rate 

of map correlation using basin centroids. Basin centroids 

consistently improved selection results, whereas the choice of 

Pearson’s r or Spearman’s rho did not. The addition of anisotropy for centroid-based correlation maps increased the success 

rate for selecting the best correlated reference streamgage 

when using Spearman’s rho, whereas use of Pearson’s r led 

to a decrease in success rate. In general, the success rate for 

selecting the best correlated streamgage increased with an 

increase in the NS efficiency. 

The Upper Delaware River pilot basin trials showed minimal differences in the success rates for selection of the best 

correlated reference streamgage. Success rates ranged from 50 

to 61 percent across all trials (fig. 7). Selection of the closest 

reference streamgage by basin outlet location and map correlation selection using centroid location performed best, with a 

success rate of 61 percent. Using the basin centroid distance 

metric improved the map correlation selection outcome, but 

the rate of successful selection decreased when basin centroid 

was substituted for outlet location in the closest streamgage 

selection method. In only one trial (map correlation selection 

using basin outlet locations) did the choice of Pearson’s r or 

Spearman’s rho have an effect on the success rates. Anisotropy reduced the success rate of map correlation using basin 

centroids from 61 to 50 percent. For the Lower Susquehanna 

River pilot basin, there was no clear association between the 

NS efficiencies and success rates for selecting the best correlated streamgage. This can be seen in the map correlation 

with anisotropy trials where NS efficiencies have the highest 

values of all trials (fig. 6), yet have the lowest success rates in 

selection of the best correlated reference streamgage. 

The pilot basin trials demonstrate that modifications to 

the map correlation method of Archfield and others (2010) can 

improve the probability of selecting the most highly correlated 

streamgage as a reference streamgage for an ungaged location. 

The results from the trials in the two basins are summarized 

in table 4. The modified map correlation method performed as 

well as, or better than, the commonly used method of selecting 

the closest streamgage as a reference. The most useful modification is use of the basin centroid in place of basin outlet when 

determining distances in the correlation models, which consistently improved selection outcomes. Although the inclusion of 

anisotropy in map correlation improved selection outcomes in 

only one of the trials in the Lower Susquehanna River Basin, 

this may be an area for exploration in the future. 

Statewide Map Correlation Development

Variogram models were developed for 156 reference 

streamgages in and near Pennsylvania with minimally altered 

streamflow and at least 10 years of continuous record during 

1960–2008 water years and for 1 reference streamgage with 8 

years of record that was selected to improve spatial coverage. 

The streamgages used in the map correlation development 

are listed in appendix 1 and labeled MAP. From the complete 

list of reference streamgages found in appendix 1, 12 of the 

streamgages were not included in the map correlation development because of insufficient unregulated streamflow record, 

insufficient streamflow record during 1960–2008, or invalid 

correlations related to limited concurrent years of record.

The spherical variogram model was selected to describe 

the spatial structure within the correlation of daily streamflow for several reasons. First, out of several model forms, it 

produced the best fit to the data. Additional trial fitting using 

exponential and Bessel function models was also explored. 

The trials confirmed that the spherical form produced the best 

fits averaged for all reference streamgages. Second, the spherical model exhibited a good match to the correlation to separation distance relation of the observed data at distances near the 

Success rate for selection of the best correlated

streamgage, in percent

0

10

20

30

40

50

60

70 Lower Susquehanna River pilot basin Upper Delaware River pilot basin

Pearson’s r

Spearman’s rho

COUTL MOUTL CCTRD MCTRD MANIS COUTL CCTRD MOUTL MCTRD MANIS

EXPLANATION

Figure 7. Success rate for selection of the best correlated 

streamgage by using distance and map correlation methods 

applied in the pilot basins. (COUTL, closest streamgage using 

outlet distance; CCTRD, closest streamgage using centroid 

distance; MOUTL, map correlation using outlet distance; MCTRD, 

map correlation using centroid distance; MANIS, map correlation 

with anisotropy using centroid distance)
Estimation of Baseline Daily Mean Streamflow 19

Table 4. Summary of map correlation application in two pilot basins in Pennsylvania.

[--, not applicable]

Trial

Lower Susquehanna River Basin Upper Delaware River Basin

Median 

Nash-Sutcliffe 

efficiency value

Selection of 

best correlated 

streamgage 

(percent)

Median 

Nash-Sutcliffe 

efficiency value

Selection of 

best correlated 

streamgage 

(percent)

Closest streamgage using outlet 

distance with Pearson correlation -- 30 -- 61

Closest streamgage using outlet 

distance with Spearman’s correlation -- 25 -- 60

Closest streamgage using centroid 

distance with Pearson correlation -- 50 -- 56

Closest streamgage using centroid 

distance with Spearman’s correlation -- 55 -- 56

Map correlation with Pearson 

correlation using outlet distance 0.58 40 0.28 50

Map correlation with Spearman’s 

correlation using outlet distance 0.57 40 0.29 56

Map correlation with Pearson 

correlation using centroid distance 0.63 55 0.35 61

Map correlation with Spearman’s 

correlation using centroid distance 0.62 50 0.27 61

Map correlation with anisotropy and Pearson 

correlation using centroid distance 0.61 45 0.69 50

Map correlation with anisotropy and Spearman’s 

correlation using centroid distance 0.62 60 0.67 50

origin. Although not strictly equivalent, the variogram and the 

correlation to separation distance relation of the observed data 

in this application are similar in their representation of spatial 

continuity. Model fit is improved where there is similarity 

between the linear form of the spherical model near the origin 

and the correlation to distance relation of the observed data. 

The near origin behavior is an important consideration in the 

choice of model (Isaaks and Srivastava, 1989), and Pearson’s 

r and Spearman’s rho for the reference streamgages have reasonably linear relations with distance, critically in the region 

nearest the origin. Lastly, the spherical model is perhaps the 

most broadly applied variogram function.

It is desirable that the period of streamflow record common to the reference streamgages be sufficiently long to represent as broad a range of streamflow values as possible. Short 

common periods of record can produce misleading correlation 

coefficients which may affect the spatial correlation relation 

and the choice of reference streamgage. Streamflow records of 

short duration often exhibit a restricted range of streamflows 

and are candidates for deletion from the dataset owing to limited usefulness for estimating a representative hydrograph for 

20 years or more. As a practical matter, retaining these short 

period of record correlation pairs was deemed useful because 

the performance of map correlation (kriging) is contingent on 

data density (Archfield and Vogel, 2010; Skoien and Blöschl, 

2007), and data obtained from short common periods of record 

have value for defining the spatial correlation structure. All 

reference streamgage correlations used in the variogram development were significant at the 0.05 level.

The mean correlation resulting from the map correlation method for the reference streamgages statewide is 0.93 

(table 5). Mean correlations are shown in table 5 by drainage 

area and major basin. As the drainage area of the gaged basins 

increases, the mean correlation increases as well. Basins with 

small drainage areas tend to have unique hydrologic characteristics that can be more difficult to correlate with other basins. 

Lake Erie/Genesee River Basin had the lowest mean correlation, most likely because of the limited number of streamgages 

and lower density of streamgages than in other parts of the 

State. The Lower Susquehanna and Upper Delaware River 

Basins, in which the pilot analyses were conducted, had mean 

correlations of 0.94 and 0.95, respectively.
20 Estimation of Baseline Daily Mean Streamflows for Ungaged Locations on Pennsylvania Streams, WY 1960–2008

Table 5. Mean streamflow correlations for reference 

streamgages used in the map correlation method for 

Pennsylvania streams, by drainage area and major basin.

Area/basin

Number of 

reference 

streamgages

Mean 

streamflow 

correlation

By drainage area (in square miles)

Less than 15 29 0.91

15–49 23 0.93

50–149 39 0.94

150–499 49 0.95

Greater than or equal to 500 16 0.96

By major basin

Upper Delaware 18 0.95

Lower Delaware 20 0.94

Upper Susquehanna 15 0.93

West Branch Susquehanna 23 0.96

Lower Susquehanna 20 0.94

Potomac 7 0.92

Lake Erie/Genesee 2 0.88

Allegheny 28 0.94

Monongahela 11 0.93

Upper Ohio 12 0.92

Statewide 156 0.93

Use of BaSE for Estimating Baseline 

Daily Mean Streamflow for Ungaged 

Locations

The Baseline Streamflow Estimator (BaSE) is a tool for 

simulating minimally altered streamflow at a daily time step 

for an ungaged location in Pennsylvania for WY 1960 to 2008. 

BaSE is a user-friendly and time-saving tool used to assist 

water-resource managers in determining water-allocation, 

ecological-flow, and human-health needs. BaSE is modeled 

after the MASYE (Archfield and others, 2010), but parts of the 

MASYE code have been modified for use in this application 

and written as a stand-alone application on a visual basic.net 

(VB.NET) platform with the use of Microsoft Excel®. Output 

from the program consists of reference streamgage information, baseline daily mean streamflow, mean and median 

streamflow, FDCs, and hydrographs.

Basin characteristic information for the ungaged location is manually entered by the user or obtained in StreamStats (http://water.usgs.gov/osw/streamstats/pennsylvania.

html). BaSE can read in the geodatabase file downloaded from 

StreamStats and auto-populate the opening screen with the 

required information. BaSE selects an appropriate reference 

streamgage for a user-entered ungaged location by default; 

the default is based on maximizing the estimated streamflow 

correlation. The user has the option of manually selecting a 

different reference streamgage. After the initial information is 

entered into BaSE, the Compute Baseline Daily Streamflows 

function computes the baseline daily mean streamflows for the 

ungaged location for WY 1960 to 2008.

A report output file, a Microsoft Excel® spreadsheet, 

is generated and summarizes the reference streamgage and 

ungaged location information, including basin characteristics, 

percent difference in basin characteristics between the two 

locations, and any warnings associated with the basin characteristics (fig. 8). Mean and median streamflows are computed 

for the ungaged location. FDCs and hydrographs are presented 

for the ungaged location in cubic feet per second and cubic 

feet per second per square mile. The estimated daily flows 

for the ungaged location can be easily exported to a text file 

that can be used as input into a statistical software package to 

determine additional streamflow statistics, such as low-flow 

frequencies or monthly flow-duration exceedance probabilities. More detailed information, instructions for use, and all 

related links to files for the BaSE tool are in appendix 5. 

Accuracy and Limitations of Estimated 

Baseline Streamflows

Accuracy of estimated baseline daily streamflows for 

ungaged locations is dependent on the uncertainties associated 

with the multiple steps which compose the overall process. 

These steps include (1) measurement of streamflow at reference streamgages, (2) streamflow record extension at reference 

streamgages, (3) selection of a reference streamgage using 

the map correlation method, (4) transfer of exceedance probabilities from reference streamgage to the ungaged location, 

and (5) estimation of the flow duration curve for an ungaged 

location on the basis of regression equations and basin 

characteristics. 

The accuracy of measured streamflow data is documented 

for each reference streamgage in annual data reports. In Pennsylvania, most of the published streamflow records are rated as 

fair to good. These ratings specify that 95 percent of the data 

are within 10 (good) to 15 (fair) percent of their true values. 

Streamflow record extension introduces uncertainty to 

baseline streamflow estimates, which is difficult to quantify. 

Because the length of record requiring extension varied by 

streamgage from none to 75 percent of the record, the uncertainty introduced to the overall record also varies. A general 

sense of the accuracy of these estimates can be obtained by 

observing the correlation coefficients, which range from 0.75 

to 0.98 (with a perfect correlation equal to 1). Factoring in the 

part of the record that required no extension will decrease the 

overall uncertainty. When the relation between the logarithm 

of streamflow at a streamgage requiring record extension and 
Accuracy and Limitations of Estimated Baseline Streamflows 21

Figure 8. Screen capture of report generated by the BaSE tool showing flow duration curves and a hydrograph.

the logarithm of streamflow at the reference streamgage is 

non-linear, the correlations, and associated uncertainties, are 

less likely to agree. Thus, the overall uncertainty introduced 

by record extension is a combination of the length of extension 

period, strength of reference streamgage correlation, and quality of the relation between daily streamflow and daily exceedance probabilities when streamflow is used as a surrogate for 

exceedance probability 

The selection of a reference streamgage by map correlation affects the uncertainty in the baseline streamflow 

estimates by way of the accuracy with which the best correlated reference streamgage is selected. Even when the best 

correlated reference streamgage is selected, uncertainty is 

introduced into the daily exceedance probabilities for the 

ungaged location because the reference streamgage would 

still not be perfectly correlated. Additional uncertainty would 

be introduced if map correlation did not select the best correlated reference streamgage. In the pilot basin trials, crossvalidation experiments permitted comparison of the accuracy 

between the map correlation methods and alternate means in 

the selection of the best reference streamgage. The pilot basin 

trials showed that 50 to 60 percent of the time, map correlation selected the best correlated streamgage. However, the 

accuracy of map correlation when extrapolated to ungaged 

locations across Pennsylvania remains unknown.

The transfer of streamflow exceedance probabilities from 

reference streamgage to an ungaged location relies on the 

assumption that both locations experience identical exceedance probabilities at identical times. Although this assumption is more likely to be true for locations in proximity to the 

reference streamgage, its validity for ungaged locations at the 

distances common statewide is unknown. Other than in the 

pilot basin trials presented in this report, this assumption is 

untested in Pennsylvania. 

Uncertainties in the constructed FDC for the ungaged 

locations consist of errors in the regression estimates of 

the 17 specified exceedance probabilities and uncertainties 

introduced through interpolation of the remaining unspecified 

exceedance probabilities of the FDC. Prediction errors for the 

regression estimates range from 11 to 92 percent (table 2). 

All other exceedance probabilities are interpolated. Archfield and others (2010) noted “hook” features when plotting 

observed and estimated daily mean streamflows at the highest 

and lowest streamflows and attributed that to an artifact of 

the log-linear interpolation between the exceedance probabilities that were used in Massachusetts. This hook feature 
22 Estimation of Baseline Daily Mean Streamflows for Ungaged Locations on Pennsylvania Streams, WY 1960–2008

was also prevalent in plots of observed and estimated streamflow for streamgages in Pennsylvania. A FDC for streamgage 

01548500 using log-linear interpolation is shown in figure 9A; 

hook features are circled in red. Use of log-log interpolation 

smoothed out the hook features in the higher flows (fig. 9B). 

Other interpolations were examined to smooth the lower hook 

features, but without consistent results. The remaining hook 

features affect mainly the extreme low streamflows (well 

below P99) observed over the 49-year period, typically resulting in underprediction of extreme low flows.

 To evaluate the effectiveness of the overall QPPQ 

method contained within BaSE, a comparison of observed and 

estimated daily mean streamflows was performed for all the 

streamgages in the pilot basins. Estimated streamflows were 

produced using the BaSE tool and the best correlated reference streamgage within the same pilot basin. Only periods 

with observed daily mean streamflows were compared. The 

comparison is intended to show how the BaSE tool can be 

expected to perform over the range of basin characteristics 

found across the State. Overall, the pilot basin streamgages 

are representative of the range of basin characteristics used 

in the development of the regression equations. With the 

exception of impervious land cover, more than 50 percent of 

the range of basin characteristics is represented by the pilot 

basin streamgages. NS efficiency values and percent rootmean-square-error (RMSE) were computed as a measure of 

goodness of fit. Median NS efficiencies ranged from 0.54 to 

0.96 (median of 0.82) for the Lower Susquehanna River pilot 

basin and from 0.47 to 0.91 (median of 0.79) for the Upper 

Delaware River pilot basin (fig. 10A). RMSE ranged from 27 

to 256 percent (median of 93 percent) for the Lower Susquehanna River pilot basin and from 43 to 228 percent (median 

of 65 percent) for the Upper Delaware River pilot basin 

(fig. 10B). 

Hydrographs and FDCs generated in BaSE for 

streamgages 01556000, Frankstown Branch Juniata River at 

Williamsburg, Pa., and 01452500, Monocacy Creek at Bethlehem, Pa., are shown in figures 11A and 11B, respectively. 

These streamgages represent the best (01556000) and worst 

(01452500) correlations for streamgages in the pilot basins 

with observed streamflow for WY 1960 to 2008. Streamgage 

01556000 was associated with reference streamgage 01559000 

with a correlation of 0.97, and streamgage 01452500 was associated with reference streamgage 01451500 with a correlation 

of 0.90 for estimates of daily mean flow. The low-flow period 

from 1998 to 2002 is shown in the hydrographs in figure 11. 

Although both hydrographs show good general fit between 

the estimated and observed streamflow, the hydrograph for 

Estimated daily mean streamflow,

in cubic feet per second

Observed daily mean stream flow, in cubic feet per second

1

Nash-Sutcliffe efficiency

value = 0.27

1

10

10

100

100

1,000

1,000

10,000 100,000

A

100,000

10,000

Estimated daily mean streamflow,

in cubic feet per second

Observed daily mean stream flow, in cubic feet per second

1

Nash-Sutcliffe efficiency

value = 0.96

1

10

10

100

100

1,000

1,000

10,000 100,000

B

100,000

10,000

Figure 9. Observed and estimated daily mean 

streamflow for U.S. Geological Survey streamgage 

01548500 Pine Creek at Cedar Run, Pa., using, A, 

log-linear interpolation and, B, log-log interpolation.
Accuracy and Limitations of Estimated Baseline Streamflows 23

Nash-Sutcliffe efficiency value

0.4

0.5

0.6

0.7

0.8

0.8

1.0

Upper Delaware

River Basin

Lower Susquehanna

River Basin

A

Root mean square error

0

50

100

150

200

250

300

Upper Delaware

River Basin

Lower Susquehanna

River Basin

B

75th percentile

50th percentile

(median)

25th percentile

Interquartile

range

EXPLANATION

Figure 10. Distribution of, A, Nash-Sutcliffe efficiency values and, B, root mean square error obtained from comparison between 

observed and estimated daily mean streamflows in the two pilot basins in Pennsylvania. Streamflow, in cubic feet per second

1

10

100

1,000

10,000

100,000

0 0.1 0.30.2 0.4 0.5 0.6 0.7 0.8 0.9 1

Flow duration exceedance probability

Streamflow, in cubic feet per second

1

10

100

1,000

10,000

0 0.1 0.30.2 0.4 0.5 0.6 0.7 0.8 0.9 1

Flow duration exceedance probability

Estimated streamflow

EXPLANATION

Observed streamflow

Estimated streamflow

EXPLANATION

Observed streamflow

Streamflow, in cubic feet per second

1

10

100

1,000

10,000

100,000

1998 1999 2000 2001 2002

Nash-Sutcliffe efficiency

value = 0.92

Estimated streamflow

EXPLANATION

Observed streamflow

A. 01556000

Streamflow, in cubic feet per second

1

10

100

1,000

10,000

1998 1999 2000 2001 2002

Nash-Sutcliffe efficiency

value = 0.69

Estimated streamflow

EXPLANATION

Observed streamflow

B. 01452500

Figure 11. Hydrographs and flow duration curves showing estimated and observed daily mean flows for U.S. 

Geological Survey streamgages, A, 01556000, Frankstown Branch Juniata River at Williamsburg, Pa., and, B, 

01452500, Monocacy Creek at Bethlehem, Pa.
24 Estimation of Baseline Daily Mean Streamflows for Ungaged Locations on Pennsylvania Streams, WY 1960–2008

01452500 shows more variance, which is reflected in the 

lower NS value of 0.69. 

BaSE relies on estimates of streamflow derived from 

regression equations, and as such, it is not to be used for 

streams with basin characteristics outside the range used to 

develop the equations. Estimates of streamflow for streams 

with basin characteristics outside this range may not be valid. 

The range of basin characteristics used in the development 

of the regression equations is shown in table 6. Alterations to 

streamflow by regulation, mining, or other large water uses are 

not reflected in the estimated streamflows generated by BaSE, 

which are estimates of unaffected streamflows under baseline 

conditions. If groundwater and surface-water divides are not 

coincident, which can occur in areas with karst topography or 

mining, results from the regression equations and BaSE also 

may not be valid. 

location with the streamflow as a percentile for the same day 

at a reference streamgage. Correlation of streamflow is used 

to select an appropriate reference streamgage for the ungaged 

location. Streamflows corresponding to the percentile for 

the ungaged location are selected from a daily FDC constructed from points determined by regression equations using 

basin characteristics. 

Flow-duration exceedance probability regression equations were developed for 17 percentiles along the FDC using 

data from 162 streamgages from the 1960 water year through 

the 2008 water year. The standard errors of prediction for the 

flow-duration regression equations range from 11 percent to 

92 percent, with the average standard error over the entire 

suite of equations equal to 31 percent. 

The map correlation method was tested in two pilot 

basins—the Lower Susquehanna River Basin and the Upper 

Delaware River Basin—to confirm applicability for use in 

Pennsylvania. The map correlation method performed as well 

as, or better than, the closest centroid method for selecting reference sites in the basins and offers consistency and reliability 

in the approach. Therefore, variogram models were developed 

for a subset of the reference streamgage dataset with minimally altered streamflow in and near Pennsylvania using a 

spherical distribution model. 

The BaSE tool estimates the daily mean streamflow for 

an ungaged location by first selecting a reference streamgage 

using the map correlation method as a default. An option is 

available for a manual choice by the user. After selecting a 

reference streamgage, BaSE then equates the percentiles at the 

gaged site for a particular day with percentiles at the ungaged 

location for the same day. The percentiles are converted to 

streamflow at the ungaged location using regression equations and interpolation. BaSE outputs a report file in Microsoft 

Excel® summarizing the reference streamgage and ungaged 

location information, including basin characteristics, percent 

difference in basin characteristics between the two sites, any 

warning associated with the basin characteristics, mean and 

Summary

The ability to generate daily mean streamflow for any 

location on a stream in Pennsylvania is critical for waterresource managers. Water-allocation decisions, recreation 

resource decisions, and in-depth evaluation of flow regimes to 

promote instream ecological health often require streamflow 

information obtainable only from a time series hydrograph. 

Daily mean streamflow is not readily available for ungaged 

streams in Pennsylvania. The U.S. Geological Survey, in cooperation with the Pennsylvania Department of Environmental 

Protection, Susquehanna River Basin Commission, and The 

Nature Conservancy, has developed the Baseline Streamflow 

Estimator (BaSE) to estimate minimally altered or “baseline” 

daily mean streamflow for ungaged streams in Pennsylvania 

for water years 1960 to 2008. BaSE uses a modified QPPQ 

approach that equates the streamflow as a percentile from the 

flow duration curve (FDC) for a particular day at an ungaged 

Table 6. Basin characteristics with minimum, maximum, and mean values used in development of regression 

equations to estimate flow-duration exceedance probabilities with BaSE for basins in Pennsylvania.

Basin characteristic Minimum Maximum Mean

Longitude (decimal degrees) 74.9856 80.9953 77.6276

Drainage area (square mile) 2.39 1,462 171

Percent impervious area 0.02 29.2 2.5

Percent carbonate bedrock 0 83.2 6.9

Mean annual precipitation (inches) 32.4 48.9 42

Mean maximum daily temperature (degrees Fahrenheit) 52.3 62.0 57.3

Soil depth to bedrock (feet) 3.18 6.12 4.64

Drainage runoff number1 2.80 5.44 3.57

1

Unit less 1 = well to 7 = poor
References Cited 25

median streamflows, and hydrographs for the ungaged location. The daily mean streamflow for the ungaged location 

can be exported as a text file to be used as input into separate 

statistical software for further analysis.

Accuracy of estimated baseline daily mean streamflow for 

ungaged locations is affected by the uncertainties introduced 

by the multiple steps involved in the process. Uncertainty is 

introduced during the selection of the reference streamgage, 

estimation of exceedance probabilities for the ungaged location, and the QPPQ process. It is difficult to quantify the 

overall uncertainty associated with the estimated daily mean 

flows at the ungaged location because of the number of potential sources. Observed and estimated daily mean flows for 

reference streamgages in the two pilot basins were examined 

for accuracy. Median Nash-Sutcliffe efficiency values ranged 

from 0.47 to 0.96, and root mean square errors ranged from 27 

to 256 percent for the streamgages in the pilot basins. BaSE 

is not to be used to estimate daily mean streamflow in basins 

with basin characteristics outside the range used to develop 

the equations. Alterations to streamflow by regulation, mining, 

or other large water uses are not reflected in the estimated 

streamflow values generated by BaSE. If the groundwater and 

surface-water divides are not coincident, which can occur in 

areas with karst topography or mining, results from the regression equations and BaSE may not be valid. 

References Cited

Apse, C., Dephilip, M., Zimmerman, J., and Smith, M.P., 

2008, Developing instream flow criteria to support ecologically sustainable water resource planning and management: 

Harrisburg, Pa: The Nature Conservancy, p. 195

Archfield, S.A., Vogel, R.M., Steeves, P.A., Brandt, S.L., 

Weiskel, P.K., and Garabedian, S.P., 2010, The Massachusetts Sustainable-Yield Estimator: A decision-support tool 

to assess water availability at ungaged stream locations in 

Massachusetts: U.S. Geological Survey Scientific Investigations Report 2009–5227, 41 p., plus CD-ROM.

Archfield, S. A., and R. M. Vogel, 2010, Map correlation 

method: Selection of a reference streamgage to estimate 

daily streamflow at ungaged catchments: Water Resources 

Research, no. 46, W10513, doi:10.1029/2009WR008481. 

Daly, Christopher, 1996, Overview of the PRISM Model, 

accessed December 7, 2011, at http://www.ocs.orst.edu/

prism/overview.html.

DePhilip, M., and Moberg, T., 2010, Ecosystem Flow Recommendations for the Susquehanna River Basin: The Nature 

Conservancy, 96 p.

Environmental Resources Research Institute, 1996, Areas of 

carbonate lithology: Pennsylvania Department of Environmental Protection, accessed December 7, 2011, at http://

www.pasda.psu.edu/.

Environmental Systems Research Institute, Inc., 2009, 

accessed August 4, 2009, at http://www.esri.com/.

Fennessey, N.M., 1994, A hydro-climatological model of daily 

streamflow for the northeast United States: Medford, Mass., 

Tufts University, Ph.D. dissertation [variously paged].

Granato, G.E., 2009, Computer programs for obtaining and 

analyzing daily mean streamflow data from the U.S. Geological Survey National Water Information System Web 

Site: U.S. Geological Survey Open-File Report 2008–1362, 

123 p. on CD-ROM, 5 append.

Helsel, D.R., and Hirsch, R.M., 1992, Studies in environmental science 49—Statistical methods in water resources: 

Amsterdam, Elsevier, 522 p.

Henriksen, J.A, Heasley, J., Kennen, J.G., and Nieswand, S., 

2006, Users’ manual for the Hydroecological Integrity 

Assessment Process software (including the New Jersey 

Assessment Tools): U.S. Geological Survey Open-File 

Report 2006–1093, 72 p.

Hirsch, R.M., 1982, A comparison of four streamflow record 

extension techniques: Water Resources Research, v. 18, 

no. 4, p. 1081–1088.

Homer, C., Huang, C., Yang, L., Wylie, B., and Coan, M., 

2004, Development of a 2001 National Landcover Database for the United States: Photogrammetric Engineering 

and Remote Sensing, v. 70, no. 7, July 2004, p. 829–840, 

accessed December 7, 2011, at http://www.mrlc.gov/

mrlc2k_publications.asp.

Huang, W-C., and Yang, F-T., 1998, Streamflow estimation 

using kriging: Water Resources Research, v. 34, no. 6, 

p. 1599–1608.

Hughes, D.A., and Smakhtin, V.U., 1996, Daily flow time 

series patching or extension: a spatial interpolation 

approach based on flow duration curves: Journal of 

Hydrological Sciences, v. 41, no. 6, p. 851–871.

Isaaks, E.H., and Srivastava, R.M., 1989, An Introduction to 

Applied Geostatistics: New York and Oxford, Oxford 

University Press, 561 p.

Mohamoud, Y. M., 2008, Prediction of daily flow duration 

curves and streamflow for ungauged catchments using 

regional flow duration curves: Journal of Hydrological 

Sciences, v. 53, no. 4, p. 706–724. 
26 Estimation of Baseline Daily Mean Streamflows for Ungaged Locations on Pennsylvania Streams, WY 1960–2008

Pennsylvania Department of Conservation and Natural 

Resources, 1997, Glacial deposits of Pennsylvania: Bureau 

of Topographic and Geologic Survey, accessed December 7, 

2011, at http://www.dcnr.state.pa.us/topogeo/field/glacial.

aspx.

Poff, N.L., Richter, B., Arthington, A.H., Bunn, S.E., Naiman, 

R.J., Kendy, E., Acreman, M., Apse, C., Bledsoe, B.P., Freeman, M., Henriksen, J., Jacobson, R.B., Kennen, J., Merritt, 

D.M., O’Keeffe, J., Olden, J.D., Rogers, K., Tharme, R.E., 

and Warner, A., 2010, The Ecological Limits of Hydrologic 

Alteration (ELOHA): a new framework for developing 

regional environmental flow standards: Freshwater Biology, 

no. 55, p. 147–170.

Price, C., Nakagaki, N., Hitt, K., and Clawges, R., 2003, Mining GIRAS: Improving on a national treasure of land use 

data: ESRI International User Conference 2003 Proceedings, accessed December 7, 2011, at http://gis.esri.com/

library/userconf/proc03/p0904.pdf.

Risser, D.W., Thompson, R.E., and Stuckey, M.H., 2008, 

Regression method for estimating long-term mean annual 

ground-water recharge rates from base flow in Pennsylvania: U.S. Geological Survey Scientific Investigations Report 

2008–5185, 23 p.

Roland, M.A., and Stuckey, M.H., 2008, Regression equations 

for estimating magnitude and frequency of peak flows for 

ungaged streams in Pennsylvania: U.S. Geological Survey 

Scientific Investigations Report 2008–5102, 76 p.

Searcy, J. K., 1959, Flow-duration curves: U.S. Geological 

Survey Water-Supply Paper 1542-A, p. 1–33. 

Searcy, J.K., 1960, Graphical correlation of gaging-station 

records: U.S. Geological Survey Water-Supply Paper 

1541–C, p. 67–100. 

Shu, C., and Ourda, T.B.M.J., 2012, Improved methods for daily streamflow estimates at ungaused 

sites: Water Resources Research, v. 48, W02523, 

doi:10.1029/2011WR011501.

Skøien, J.O., and Blöschl, G., 2007, Spatiotemporal topological kriging of runoff time series: Water Resources 

Research, 43, W09419, doi:10.1029/2006WR005760. 

Smakhtin, V.U., 1999, Generation of natural daily flow time 

series in regulated rivers using nonlinear spatial interpolation technique: Regulated Rivers Research and Management 

v. 15, 12 p.

Smakhtin, V.U., and Masse, B., 2000, Continuous daily hydrograph simulation using duration curves of a precipitation 

index: Hydrological Processes, v. 14, p. 1,083–1,100. 

Stuckey, M.H., 2006, Low-flow, base-flow, and mean-flow 

regression equations for Pennsylvania streams: U.S. Geological Survey Scientific Investigations Report 2006–5130, 

84 p.

Stuckey, M.H., 2008, Development of the Water-Analysis 

Screening Tool used in the initial screening for the Pennsylvania State Water Plan update of 2008: U.S. Geological 

Survey Open-File Report 2008–1106, 9 p.

Stuckey, M.H., and Hoffman, S.A., 2010, Pennsylvania 

StreamStats: A web-based application for obtaining waterresource-related information: U.S. Geological Survey Fact 

Sheet 2010–3086, 2 p.

Stuckey, M.H., and Roland, M.A., 2011, Selected streamflow 

statistics for streamgage locations in and near Pennsylvania: 

U.S. Geological Survey Scientific Investigations Report 

2011–1070, 88 p.

The Nature Conservancy, 2009, Indicators of Hydrologic 

Alteration Version 7.1 User’s Manual: The Nature Conservancy, April 2009, 76 p.

TIBCO Software Inc., 2008, TIBCO Spotfire S+ 8.1 Guide to 

Packages: Palo Alto, Calif., 77 p.

U.S. Department of Agriculture, 1994, State Soil Geographic 

(STATSGO) Data Base: Washington D.C.: Miscellaneous 

Publication Number 1492, 33 p., accessed June 19, 2012, at 

http://dbwww.essc.psu.edu/dbtop/doc/statsgo/statsgo_info.

html. 

U.S. Geological Survey, 2000a, U.S. GeoData Digital Elevation Models: U.S. Geological Survey Fact Sheet 040–00, 

3 p., accessed December 7, 2011, at http://erg.usgs.gov/isb/

pubs/factsheets/fs04000.html.

U.S. Geological Survey, 2000b, NHD User Guide, accessed 

December 7, 2011, at http://nhd.usgs.gov/userguide.html.

Vogel, R.M., and Fennessey, N.M., 1994, Flow-duration 

curves I: A new interpretation and confidence intervals: 

ASCE Journal of Water Resources Planning and Management, v. 120, no. 4, p. 485–504.

Vogel, R.M., and Stedinger, J.R., 1985, Minimum variance streamflow record augmentation procedures: Water 

Resources Research, v. 21, no. 5, p. 715–723.

Waldron, M.C., and Archfield, S.A., 2006, Factors affecting 

firm yield and the estimation of firm yield for streamflowdominated drinking-water-supply reservoirs in Massachusetts: U.S. Geological Survey Scientific Investigations 

Report 2006–5044, 39 p.
Appendixes 1–4
28 Estimation of Baseline Daily Mean Streamflows for Ungaged Locations on Pennsylvania Streams, WY 1960–2008 Appendix 1. Description of reference streamgages used in the development of BaSE for Pennsylvania with period of record and use of data.—Continued [ddmmss, degrees, minutes, seconds; mi2, square miles] U.S. Geological Survey streamgage number Name Latitude (ddmmss) Longitude (ddmmss) Drainage area (mi2

)

Period of record1 Use of daily streamflow data2

01420500 Beaver Kill at Cooks Falls, NY 415647 745848 242 1913–2008 MAP, PILOT01423000 West Branch Delaware River at Walton, NY 420958 750825 332 1950–2008 MAP, PILOT

0142400103 Trout Creek near Trout Creek, NY 421025 751647 20.2 1952–67, 1996–1999 REG, MAP, PILOT

01426000 Oquaga Creek at Deposit, NY 420331 752542 67.7 1941–73, 2004–2005 MAP, PILOT01428750 West Branch Lackawaxen River near Aldenville, PA 414028 752235 40.6 1987–2008 REG, MAP, PILOT01429000 West Branch Lackawaxen River at Prompton, PA 413514 751938 59.7 1945–2008 REG01431000 Middle Creek near Hawley, PA 412905 751320 78.4 1946–1960 REG01439500 Bush Kill at Shoemakers, PA 410517 750217 117 1909–2008 REG, MAP, PILOT01440400 Brodhead Creek near Analomink, PA 410505 751254 65.9 1958–2008 REG, MAP, PILOT01442500 Brodhead Creek at Minisink Hills, PA 405955 750835 259 1950–2008 REG, MAP, PILOT01447500 Lehigh River at Stoddartsville, PA 410749 753733 91.7 1944–2008 REG, MAP, PILOT01447720 Tobyhanna Creek near Blakeslee, PA 410505 753621 118 1961–1984 REG, MAP, PILOT01448500 Dilldown Creek near Long Pond, PA 410208 753237 2.39 1949–1996 REG, MAP, PILOT01449360 Pohopoco Creek at Kresgeville, PA 405351 753010 49.9 1966–2008 REG, MAP, PILOT01450500 Aquashicola Creek at Palmerton, PA 404822 753554 76.7 1939–2008 REG, MAP, PILOT01451500 Little Lehigh Creek near Allentown, PA 403456 752900 80.8 1946–2008 REG, MAP, PILOT01451800 Jordan Creek near Schnecksville, PA 403942 753738 53.0 1966–2008 REG, MAP, PILOT01452000 Jordan Creek at Allentown, PA 403723 752858 75.8 1945–2008 REG, MAP, PILOT01452500 Monocacy Creek at Bethlehem, PA 403828 752247 44.5 1948–2008 REG, MAP, PILOT01459500 Tohickon Creek near Pipersville, PA 402601 750701 97.4 1937–1973 REG, MAP, PILOT01464907 Little Neshaminy Creek at Valley Road near Neshaminy PA 401345 750712 26.8 1998–2008 REG, MAP01465798 Poquessing Creek at Grant Avenue at Philadelphia, PA 400325 745908 21.4 1966–2008 REG01467048 Pennypack Creek at Lower Rhawn Street Bridge, Philadelphia, PA 400300 750159 49.8 1965–2008 REG, MAP01467086 Tacony Creek above Adams Avenue, Philadelphia, PA 400247 750640 16.7 1966–70;1974–86;2006–08 REG01468500 Schuylkill River at Landingville, PA 403745 760730 133 1948–53;1963–65;1974–2008 REG, MAP01470500 Schuylkill River at Berne, PA 403121 755955 355 1949–2008 REG, MAP01470756 Maiden Creek at Virginville, PA 403051 755300 159 1973–1995 REG, MAP01470779 Tulpehocken Creek near Bernville, PA 402448 761019 66.5 1975–2002 REG, MAP01471000 Tulpehocken Creek near Reading, PA 402208 755846 211 1951–1979 REG, MAP01471980 Manatawny Creek near Pottstown, PA 401622 754049 85.5 1975–2004 REG, MAP
Appendix 1 29

Appendix 1. Description of reference streamgages used in the development of BaSE for Pennsylvania with period of record and use of data.—Continued[ddmmss, degrees, minutes, seconds; mi2, square miles]

U.S. Geological 

Survey streamgage 

number

Name Latitude (ddmmss) Longitude (ddmmss) Drainage area (mi2) Period of record1 Use of daily streamflow data2

01472000 Schuylkill River at Pottstown, PA 401430 753907 1147 1928–1979 REG, MAP01472157 French Creek near Phoenixville, PA 400905 753606 59.1 1969–2008 REG, MAP01472174 Pickering Creek near Chester Springs, PA 400522 753750 5.98 1967–1983 REG, MAP01472198 Perkiomen Creek at East Greenville, PA 402338 753057 38.0 1982–2008 REG, MAP01472199 West Branch Perkiomen Creek at Hillegass, PA 402226 753122 23.0 1982–2008 REG, MAP01473120 Skippack Creek near Collegeville, PA 400952 752601 53.7 1966–1994 REG, MAP01475510 Darby Creek near Darby, PA 395544 751622 37.4 1964–1990 REG, MAP01475530 Cobbs Creek at U.S. Highway No. 1 at Philadelphia, PA 395829 751649 4.78 1965–81;2005–08 REG01475850 Crum Creek near Newtown Square, PA 395835 752613 15.8 1981–2008 REG, MAP01479820 Red Clay Creek near Kennett Square, PA 394900 754131 28.3 1988–2008 REG, MAP01480300 West Branch Brandywine Creek near Honey Brook, PA 400422 755140 18.7 1961–2008 REG, MAP01480675 Marsh Creek near Glenmoore, PA 400552 754431 8.57 1967–2008 REG, MAP01481000 Brandywine Creek at Chadds Ford, PA 395211 753537 287 1912–1953;1962–1973 REG, MAP01514000 Owego Creek near Owego, NY 420745 761615 185 1930–1978 REG, MAP01516500 Corey Creek near Mainesburg, PA 414727 770054 12.2 1954–2008 REG, MAP01517000 Elk Run near Mainesburg, PA 414854 765755 10.2 1955–1978 REG, MAP01518500 Crooked Creek at Tioga, PA 415408 770855 122 1954–1974 REG, MAP01518862 Cowanesque River at Westfield, PA 415523 773156 90.6 1984–2008 REG, MAP01520000 Cowanesque River near Lawrenceville, PA 415948 770825 298 1952–1979 REG, MAP01525500 Canisteo River at West Cameron, NY 421320 772505 340 1931;1937–1970; REG, MAP01529500 Cohocton River near Campbell, NY 421509 771301 470 1919–2008 REG, MAP01530500 Newtown Creek at Elmira, NY 420616 764754 77.5 1938–1989 REG, MAP01532000 Towanda Creek near Monroeton, PA 414225 762906 215 1915–2008 REG, MAP01532850 Middle Branch Wyalusing Creek near Birchardville, PA 415145 760026 5.67 1965–1979 REG, MAP01533950 South Branch Tunkhannock Creek near Montdale, PA 413429 753832 12.6 1961–1978 REG, MAP01534000 Tunkhannock Creek near Tunkhannock, PA 413330 755342 383 1915–2008 REG, MAP01538000 Wapwallopen Creek near Wapwallopen, PA 410333 760538 43.8 1920–2008 REG, MAP01539000 Fishing Creek near Bloomsburg, PA 410441 762553 274 1939–2008 REG, MAP01541000 West Branch Susquehanna River at Bower, PA 405349 784038 315 1914–2008 REG, MAP01541308 Bradley Run near Ashville, PA 403033 783502 6.77 1967–1980 REG, MAP
30 Estimation of Baseline Daily Mean Streamflows for Ungaged Locations on Pennsylvania Streams, WY 1960–2008 Appendix 1. Description of reference streamgages used in the development of BaSE for Pennsylvania with period of record and use of data.—Continued [ddmmss, degrees, minutes, seconds; mi2, square miles] U.S. Geological Survey streamgage number Name Latitude (ddmmss) Longitude (ddmmss) Drainage area (mi2

)

Period of record1 Use of daily streamflow data2

01541500 Clearfield Creek at Dimeling, PA 405818 782422 371 1914–2008 REG01542500 West Branch Susquehanna River at Karthaus, PA 410703 780633 1462 1941–1964 REG, MAP01542810 Waldy Run near Emporium, PA 413444 781734 5.24 1965–2008 REG, MAP01543000 Driftwood Br Sinnemahoning Creek at Sterling Run, PA 412448 781150 272 1914–2008 REG, MAP01543500 Sinnemahoning Creek at Sinnemahoning, PA 411902 780612 685 1939–2008 REG, MAP01544500 Kettle Creek at Cross Fork, PA 412833 774934 136 1941–2008 REG, MAP01545600 Young Womans Creek near Renovo, PA 412322 774128 46.2 1965–2008 REG, MAP01546400 Spring Creek at Houserville, PA 405001 774940 58.5 1985–2008 REG, MAP01546500 Spring Creek near Axemann, PA 405323 774740 87.2 1941–2008 REG, MAP01547100 Spring Creek at Milesburg, PA 405554 774709 142 1968–2008 REG, MAP01547200 Bald Eagle Creek below Spring Creek at Milesburg, PA 405635 774712 265 1956–2008 REG, MAP01547700 Marsh Creek at Blanchard, PA 410334 773622 44.1 1956–2008 REG, MAP01547950 Beech Creek at Monument, PA 410642 774209 152 1969–2008 REG, MAP01548005 Bald Eagle Creek near Beech Creek Station, PA 410451 773259 562 1912–1970 REG, MAP01548500 Pine Creek at Cedar Run, PA 413118 772652 604 1919–2008 REG, MAP01549500 Blockhouse Creek near English Center, PA 412825 771352 37.7 1941–2008 REG, MAP01549700 Pine Creek below Little Pine Creek near Waterville, PA 411625 771928 944 1958–2008 REG, MAP01549780 Larrys Creek at Cogan House, PA 412504 770946 6.80 1961–1978 REG, MAP01550000 Lycoming Creek near Trout Run, PA 412506 770159 173 1914–2008 REG, MAP01552000 Loyalsock Creek at Loyalsockville, PA 411930 765446 435 1926–2008 REG, MAP01552500 Muncy Creek near Sonestown, PA 412125 763206 23.8 1941–2008 REG, MAP01553130 Sand Spring Run near White Deer, PA 410331 770437 4.93 1968–1980 REG, MAP01555000 Penns Creek at Penns Creek, PA 405200 770255 301 1930–2008 REG, MAP, PILOT01555500 East Mahantango Creek near Dalmatia, PA 403640 765444 162 1930–2008 REG, MAP, PILOT01556000 Frankstown Branch Juniata River at Williamsburg, PA 402747 781200 291 1917–2008 REG, MAP, PILOT01556500 Little Juniata River at Tipton, PA. 403740 781738 93.7 1946–1962 REG, PILOT01557500 Bald Eagle Creek at Tyrone, PA 404101 781402 44.1 1953–2008 REG, MAP, PILOT01558000 Little Juniata River at Spruce Creek, PA 403645 780827 220 1939–2008 REG, MAP, PILOT01559000 Juniata River at Huntingdon, PA 402905 780109 816 1942–2008 REG, MAP, PILOT01559700 Sulphur Springs Creek near Manns Choice, PA 395840 783708 5.28 1962–1978 REG, MAP, PILOT
Appendix 1 31

Appendix 1. Description of reference streamgages used in the development of BaSE for Pennsylvania with period of record and use of data.—Continued[ddmmss, degrees, minutes, seconds; mi2, square miles]

U.S. Geological 

Survey streamgage 

number

Name Latitude (ddmmss) Longitude (ddmmss) Drainage area (mi2) Period of record1 Use of daily streamflow data2

01560000 Dunning Creek at Belden, PA 400418 782934 172 1939–2008 REG, MAP, PILOT01562000 Raystown Branch Juniata River at Saxton, PA 401257 781556 756 1912–2008 REG, MAP, PILOT01564500 Aughwick Creek near Three Springs, PA 401245 775532 205 1938–2008 REG, MAP, PILOT01565000 Kishacoquillas Creek at Reedsville, PA 403917 773500 164 1940–70;1984–85;2001–08 REG, MAP, PILOT01565700 Little Lost Creek at Oakland Mills, PA 403619 771842 6.52 1964–1981 REG, MAP, PILOT01566000 Tuscarora Creek near Port Royal, PA 403055 772510 214 1913–58;2002–08 REG, MAP, PILOT01567500 Bixler Run near Loysville, PA 402215 772409 15.0 1954–2008 REG, MAP, PILOT01568000 Sherman Creek at Shermans Dale, PA 401924 771009 207 1930–2008 REG, MAP, PILOT01569000 Stony Creek near Dauphin, PA 402247 765427 33.2 1938–45;1967–74 REG01570000 Conodoguinet Creek near Hogestown, PA 401508 770116 470 1930–58;1967–2008 REG, MAP, PILOT01571500 Yellow Breeches Creek near Camp Hill, PA 401329 765354 216 1954–2008 REG, MAP, PILOT01572000 Lower Little Swatara Creek at Pine Grove, PA 403215 762240 34.3 1920–32;1981–84 REG01574500 Codorus Creek at Spring Grove, PA 395243 765113 75.5 1929–1964 REG, MAP, PILOT01576754 Conestoga River at Conestoga, PA 395647 762205 470 1985–2002 REG, MAP, PILOT01576787 Pequea Creek at Martic Forge, PA 395421 761943 148 1977–81;1993–95;2005–08 REG01577500 Muddy Creek at Castle Fin, PA 394621 761858 133 1929–38;1968–71 REG01578400 Bowery Run near Quarryville, PA 395341 760650 5.98 1964–1981 REG, MAP, PILOT01603500 Evitts Creek near Centerville, PA 394723 783848 30.2 1934–1982 REG, MAP01609000 Town Creek near Oldtown, MD 393312 783318 148 1967–81;2001–04;2007–2008 REG, MAP01610155 Sideling Hill Creek near Bellegrove, MD 393858 782039 102 1967–77;1999–2008 REG, MAP01612500 Little Tonoloway Creek near Hancock, MD 394245 781355 16.9 1948–1963 REG01613050 Tonoloway Creek near Needmore, PA 395354 780757 10.7 1966–2008 REG, MAP01614090 Conococheague Creek near Fayetteville, PA 395548 772623 5.05 1961–1981 REG, MAP01614500 Conococheague Creek at Fairview, MD 394259 774929 494 1930–2008 REG, MAP01639000 Monocacy River at Bridgeport, MD 394044 771404 173 1942–2008 REG, MAP03007800 Allegheny River at Port Allegany, PA 414907 781735 248 1975–2008 REG, MAP03009680 Potato Creek at Smethport, PA 414835 782550 160 1975–1995 REG, MAP03010500 Allegheny River at Eldred, PA 415748 782311 550 1939–2008 REG, MAP03010655 Oswayo Creek at Shinglehouse, PA 415742 781154 98.7 1975–2008 REG, MAP

03011020 Allegheny River at Salamanca, NY 420923 784256 1608 1904–2008 MAP
32 Estimation of Baseline Daily Mean Streamflows for Ungaged Locations on Pennsylvania Streams, WY 1960–2008 Appendix 1. Description of reference streamgages used in the development of BaSE for Pennsylvania with period of record and use of data.—Continued [ddmmss, degrees, minutes, seconds; mi2, square miles] U.S. Geological Survey streamgage number Name Latitude (ddmmss) Longitude (ddmmss) Drainage area (mi2

)

Period of record1 Use of daily streamflow data2

03011800 Kinzua Creek near Guffey, PA 414559 784308 38.8 1967–2008 REG, MAP

03013000 Conewango Creek at Waterboro, NY 421015 790410 290 1938–1993 REG, MAP03015280 Jackson Run near North Warren, PA 415410 791418 12.8 1963–1978 REG, MAP03015500 Brokenstraw Creek at Youngsville, PA 415109 791903 321 1911–2008 REG, MAP03017500 Tionesta Creek at Lynch, PA 413607 790301 233 1939–1979 REG, MAP03020500 Oil Creek at Rouseville, PA 412854 794144 300 1934–2008 REG, MAP03021350 French Creek near Wattsburg, PA 420055 794658 92.0 1975–2008 REG, MAP03021500 French Creek at Carters Corners, PA 415723 795238 208 1911–1971 REG, MAP03022540 Woodcock Creek at Blooming Valley, PA 414126 800254 31.1 1976–1995 REG, MAP03024000 French Creek at Utica, PA 412615 795722 1028 1934–1970 REG, MAP03025000 Sugar Creek at Sugarcreek, PA 412543 795248 166 1934–1979 REG, MAP03026500 Sevenmile Run near Rasselas, PA 413752 783437 7.84 1953–2008 REG, MAP03028000 West Branch Clarion River at Wilcox, PA 413431 784133 63.0 1955–2008 REG, MAP03029400 Toms Run at Cooksburg, PA 412016 791250 12.6 1961–1978 REG, MAP03031950 Big Run near Sprankle Mills, PA 405930 790526 7.38 1965–1981 REG, MAP03032500 Redbank Creek at St. Charles, PA 405940 792340 528 1920–2008 REG, MAP03038000 Crooked Creek at Idaho, PA 403917 792056 191 1939–1967 REG, MAP03039200 Clear Run near Buckstown, PA 400249 784958 3.68 1965–1978 REG, MAP03039925 North Fork Bens Creek at North Fork Reservoir, PA 401558 790101 3.45 1985;1988–1998 REG, MAP03041000 Little Conemaugh River at East Conemaugh, PA 402045 785258 186 1939–1995 MAP03042200 Little Yellow Creek near Strongstown, PA 403345 785644 7.36 1962–1988 REG, MAP03049000 Buffalo Creek near Freeport, PA 404257 794159 137 1942–2008 REG, MAP03049800 Little Pine Creek near Etna, PA 403113 795618 5.78 1963–2008 REG, MAP03062500 Deckers Creek at Morgantown, WV 393745 795710 63.2 1946–69; 2002–2008 REG, MAP03070500 Big Sandy Creek at Rockville, WV 393718 794216 200 1909–2008 MAP03072590 Georges Creek at Smithfield, PA 394744 794747 16.3 1964–1978 REG, MAP03072840 Tenmile Creek near Clarksville, PA 395951 800231 133 1969–1979 REG, MAP03073000 South Fork Tenmile Creek at Jefferson, PA 395523 800422 180 1932–1995 REG, MAP03074300 Lick Run at Hopwood, PA 395204 794140 3.80 1967–1978 REG, MAP03078000 Casselman River at Grantsville, MD 394208 790811 62.5 1947–2008 REG, MAP
Appendix 1 33

Appendix 1. Description of reference streamgages used in the development of BaSE for Pennsylvania with period of record and use of data.—Continued[ddmmss, degrees, minutes, seconds; mi2, square miles]

U.S. Geological 

Survey streamgage 

number

Name Latitude (ddmmss) Longitude (ddmmss) Drainage area (mi2) Period of record1 Use of daily streamflow data2

03079000 Casselman River at Markleton, PA 395135 791340 382 1922–2008 REG, MAP03080000 Laurel Hill Creek at Ursina, PA 394913 791918 121 1919–2008 REG, MAP03082200 Poplar Run near Normalville, PA 400059 792533 9.27 1963–1978 REG, MAP03084000 Abers Creek near Murrysville, PA 402701 794250 4.39 1949–1993 REG, MAP03085956 Montour Run at Scott Station near Imperial, PA 402723 801034 25.4 2000–2008 REG, MAP03092000 Kale Creek near Pricetown, OH 410823 805943 21.9 1941–1993 REG, MAP03093000 Eagle Creek at Phalanx Station, OH 411540 805716 97.6 1926–34, 1938–2008 REG, MAP03102500 Little Shenango River at Greenville, PA 412519 802235 104 1914–2008 REG, MAP03102950 Pymatuning Creek at Kinsman, OH 412634 803518 96.7 1966–1994 REG, MAP03103000 Pymatuning Creek near Orangeville, PA 411840 802840 169 1915–1963 REG, MAP03106000 Connoquenessing Creek near Zelienople, PA 404901 801433 356 1920–2008 REG, MAP03106500 Slippery Rock Creek at Wurtemburg, PA 405302 801402 398 1913–1969 REG, MAP03109500 Little Beaver Creek near East Liverpool, OH 404033 803227 496 1916–2008 REG, MAP

03110000 Yellow Creek near Hammondsville, OH 403216 804331 147 1941–2008 REG, MAP

03111150 Brush Run near Buffalo, PA 401154 802428 10.3 1961–78; 1983–85 REG, MAP

03111500 Short Creek near Dillonvale, OH 401136 804404 123 1942–2008 REG, MAP

04213000 Conneaut Creek at Conneaut ,OH 415537 803615 175 1922–36;1950–61;1962–2008 REG, MAP04213075 Brandy Run near Girard, PA 415931 801729 4.45 1986–2008 REG, MAP

1Period of record is in water years, defined as the 12-month period beginning October 1 and ending September 30. The water year is designated by the calendar year in which it ends.2REG, regression analysis; MAP, map correlation; PILOT, pilot basin streamgage.
34 Estimation of Baseline Daily Mean Streamflows for Ungaged Locations on Pennsylvania Streams, WY 1960–2008 Appendix 2. Reference streamgages with record extension techniques applied.—Continued U.S. Geological Survey streamgage number Name Portion of record extended Index streamgage(s) used to extend record Correlation coefficient between log-transformed flow records 0142400103 Trout Creek near Trout Creek, NY Jul 1967–Nov 1996 WBr Delaware River at Walton, NY (01423000) 0.96 01426000 Oquaga Creek at Deposit, NY Oct 1973–Sep 2008 WBr Delaware River at Walton, NY (01423000) 0.86 01428750 West Branch Lackawaxen River near Aldenville, PA Oct 1959–Sept 1987 Tunkhannock Creek near Tunkhannock, PA (01534000) 0.93 01447720 Tobyhanna Creek near Blakeslee, PA Oct 1959–Sept 1960 Oct 1985–Sept 2008 Lehigh River at Stoddartsville, PA (01447500) 0.95 01448500 Dilldown Creek near Long Pond, PA Oct 1996–Sept 2008 Brodhead Creek at Minisink Hills, PA (01442500) 0.93 Pohopoco Creek at Kresgeville, PA (01449360) 0.92 01449360 Pohopoco Creek at Kresgeville, PA Oct 1959–Sept 1966 Aquashicola Creek at Palmerton, PA (01450500) 0.96 01451800 Jordan Creek near Schnecksville, PA Oct 1959–Jan 1966 Jordan Creek at Allentown, PA (01452000) 0.98 01459500 Tohickon Creek near Pipersville, PA Dec 1973–Sep 2008 Skippack Creek near Collegeville, PA (01473120) 0.89 Jordan Creek near Schnecksville, PA (01451800) 0.87 01464907 Little Neshaminy Creek at Valley Rd, PA Oct 1959–Nov 1998 Pennypack Creek at Lower Rhawn St, Philadelphia, PA (01467048) 0.90 French Creek near Phoenixville, PA (01472157) 0.87 Jordan Creek at Allentown, PA (01452000) 0.78 01467048 Pennypack Creek at Lower Rhawn Street Bridge, Philadelphia, PA Oct 1959–Sep 1965 Tohickon Creek near Pipersville, PA (01459500) 0.75

01468500 Schuylkill River at Landingville, PA Oct 1959–Sep 1963 Oct 1965–Jul 1973 Schuylkill River at Berne, PA (01470500) 0.98
Appendix 2 35

Appendix 2. Reference streamgages with record extension techniques applied.—Continued

U.S. Geological 

Survey 

streamgage 

number

Name Portion of record extended Index streamgage(s) used to extend record

Correlation 

coefficient between 

log-transformed 

flow records

01470756 Maiden Creek at Virginville, PA Oct 1995–Sep 2008 Jordan Creek at Allentown, PA (01452000) 0.9601470779 Tulpehocken Creek near Bernville, PA Oct 1959–Nov 1974 Tulpehocken Creek near Reading, PA (01471000) 0.9201471000 Tulpehocken Creek near Reading, PA Apr 1979–Sep 2008 Schuylkill River at Berne, PA (01470500) 0.9201471980 Manatawny Creek near Pottstown, PA Oct 1959–Jul 1974 Oct 2004–Sep 2008 West Branch Perkiomen Creek at Hillegass, PA (01472199) 0.96 Jordan Creek at Allentown, PA (01452000) 0.8601472000 Schuylkill River at Pottstown, PA Apr 1979–Sep 2008 Schuylkill River at Berne, PA (01470500) 0.9701472157 French Creek near Phoenixville, PA Oct 1959–Sep 1968

Brandywine Creek at Chadds Ford, PA (01481000) 0.95Tohickon Creek near Pipersville, PA (01459500) 0.85

01472174 Pickering Creek near Chester Springs, PA Oct 1959–Dec 1966 Oct 1983–Sep 2008

Brandywine Creek at Chadds Ford, PA (01481000) 0.92French Creek near Phoenixville, PA (01472157) 0.91Little Lehigh Creek near Allentown, PA (01451500) 0.77

01472198 Perkiomen Creek at East Greenville, PA Oct 1959–Aug 1981

French Creek near Phoenixville, PA (01472157) 0.92Jordan Creek at Allentown, PA (01452000) 0.87

01472199 West Branch Perkiomen Creek at Hillegass, PA Oct 1959–Sep 1981

Manatawny Creek near Pottstown, PA (01471980) 0.96Jordan Creek at Allentown, PA (01452000) 0.87

01473120 Skippack Creek near Collegeville, PA Oct 1959–Apr 1966 Oct 1994–Sep 2008 French Creek near Phoenixville, PA (01472157) 0.86 Jordan Creek at Allentown, PA (01452000) 0.7901475510 Darby Creek near Darby, PA Oct 1959–Sep 1964 Oct 1990–Sep 2008 Crum Creek near Newtown Square, PA (01475850) 0.91 Tohickon Creek near Pipersville, PA (01459500) 0.75
36 Estimation of Baseline Daily Mean Streamflows for Ungaged Locations on Pennsylvania Streams, WY 1960–2008 Appendix 2. Reference streamgages with record extension techniques applied.—Continued U.S. Geological Survey streamgage number Name Portion of record extended Index streamgage(s) used to extend record Correlation coefficient between log-transformed flow records 01475850 Crum Creek near Newtown Square, PA Oct 1959–Sep 1981 Darby Creek near Darby, PA (01475510) 0.91 West Branch Brandywine Creek near Honey Brook, PA (01480300) 0.87 Little Lehigh Creek near Allentown, PA (01451500) 0.75 01479820 Red Clay Creek near Kennett Square, PA Oct 1959–Dec 1987 Darby Creek near Darby, PA (01475510) 0.88 Little Lehigh Creek near Allentown, PA (01451500) 0.76 01480300 West Branch Brandywine Creek near Honey Brook, PA Oct 1959–May 1960 Tohickon Creek near Pipersville, PA (01459500) 0.82 01480675 Marsh Creek near Glenmoore, PA Oct 1959–Jul 1966 Brandywine Creek at Chadds Ford, PA (01481000) 0.93 Tohickon Creek near Pipersville, PA (01459500) 0.86 01481000 Brandywine Creek at Chadds Ford, PA Oct 1959–Sep 1962 Nov 1973–Sep 2008 French Creek near Phoenixville, PA (01472157) 0.95 Schuylkill River at Pottstown, PA (01472000) 0.86 01514000 Owego Creek near Owego, NY Nov 1978–Sep 2008 Unadilla River at Rockdale, NY (01502500) 0.92 Pine Creek at Cedar Run, PA (01548500) 0.89 01517000 Elk Run near Mainesburg, PA Oct 1978–Sep 2008 Corey Creek near Mainesburg, PA (01516500) 0.97 01518500 Crooked Creek at Tioga, PA Oct 1974–Sep 2008 Pine Creek at Cedar Run, PA (01548500) 0.95 01518862 Cowanesque River at Westfield, PA Oct 1959–Jul 1983 Pine Creek at Cedar Run, PA (01548500) 0.94 01520000 Cowanesque River near Lawrenceville, PA Dec 1979–Sep 2008 Pine Creek at Cedar Run, PA (01548500) 0.95

01525500 Canisteo River at West Cameron, NY Oct 1970–Sep 2008 Cohocton River near Campbell, NY (01529500) 0.96
Appendix 2 37

Appendix 2. Reference streamgages with record extension techniques applied.—Continued

U.S. Geological 

Survey 

streamgage 

number

Name Portion of record extended Index streamgage(s) used to extend record

Correlation 

coefficient between 

log-transformed 

flow records

01530500 Newtown Creek at Elmira, NY Aug 1989–Sep 2008 Cohocton River near Campbell, NY (01529500) 0.8901532850 Middle Branch Wyalusing Creek near Birchardville, PA Oct 1959–Aug 1965 Oct 1979–Sep 2008 Tunkhannock Creek near Tunkhannock, PA (01534000) 0.8901533950 South Branch Tunkhannock Creek near Montdale, PA Oct 1959–Aug 1960 Oct 1978–Sep 2008 Tunkhannock Creek near Tunkhannock, PA (01534000) 0.9401541308 Bradley Run near Ashville, PA Oct 1959–Sep 1967 Feb 1980–Sep 2008 Frankstown Branch Juniata River at Williamsburg, PA (01556000) 0.9101542500 West Branch Susquehanna River at Karthaus, PA Nov 1965–Sep 2008 West Branch Susquehanna River at Bower, PA (01541000) 0.9601542810 Waldy Run near Emporium, PA Oct 1959–Aug 1964 Driftwood Branch Sinnemahoning Creek at Sterling Run, PA (01543000) 0.9601545600 Young Womans Creek near Renovo, PA Oct 1959–Nov 1964 Kettle Creek at Cross Fork, PA (01544500) 0.9601546400 Spring Creek at Houserville, PA Oct 1959–Aug 1984 Bald Eagle Creek below Spring Creek at Milesburg, PA (01547200) 0.9201547100 Spring Creek at Milesburg, PA Oct 1959–Sep 1967 Spring Creek near Axemann, PA (01546500) 0.9801547950 Beech Creek at Monument, PA Oct 1959–Sep 1968 Marsh Creek at Blanchard, PA (01547700) 0.9501548005 Bald Eagle Creek near Beech Creek Station, PA Mar 1971–Sep 2008 Little Juniata River at Spruce Creek, PA (01558000) 0.95
38 Estimation of Baseline Daily Mean Streamflows for Ungaged Locations on Pennsylvania Streams, WY 1960–2008 Appendix 2. Reference streamgages with record extension techniques applied.—Continued U.S. Geological Survey streamgage number Name Portion of record extended Index streamgage(s) used to extend record Correlation coefficient between log-transformed flow records 01549780 Larrys Creek at Cogan House, PA Oct 1959–Sep 1960 Oct 1978–Sep 2008 Lycoming Creek near Trout Run, PA (01550000) 0.94 01552000 Loyalsock Creek at Loyalsockville, PA Oct 1974–Sep 1975 Lycoming Creek near Trout Run, PA (01550000) 0.95 01553130 Sand Spring Run near White Deer, PA Oct 1959–Dec 1968 Apr 1981–Sep 2008 Penns Creek at Penns Creek, PA (01555000) 0.91 Beech Creek at Monument, PA (01547950) 0.89 01559700 Sulphur Springs Creek near Manns Choice, PA Oct 1959–Sep 1961 Oct 1978–Sep 2008 Dunning Creek at Belden, PA (01560000) 0.91 01565000 Kishacoquillas Creek at Reedsville, PA Oct 1970–Sep 1983 Oct 1985–Sep 2001 Penns Creek at Penns Creek, PA (01555000) 0.97 01565700 Little Lost Creek at Oakland Mills, PA Oct 1959–Aug 1963 Apr 1981–Sep 2008 Bixler Run near Loysville, PA (01567500) 0.89 01566000 Tuscarora Creek near Port Royal, PA Oct 1959–Sep 2001 Sherman Creek at Shermans Dale, PA (01568000) 0.97 01570000 Conodoguinet Creek near Hogestown, PA Oct 1959–Jun 1967 Conococheague Creek at Fairview, MD (01614500) 0.95 01574500 Codorus Creek at Spring Grove, PA Oct 1964–Oct 1965 Oct 1967–Sep 2008 Yellow Breeches Creek near Camp Hill, PA (01571500) 0.88 01576754 Conestoga River at Conestoga, PA Oct 1959–Sep 1984 French Creek near Phoenixville, PA (01472157) 0.90 Schuylkill River at Berne, PA (01470500) 0.86

01578400 Bowery Run near Quarryville, PA Oct 1959–Sep 1962 Apr 1981–Sep 2008 West Branch Brandywine Creek near Honey Brook, PA (01480300) 0.83 Codorus Creek at Spring Grove, PA (01574500) 0.75
Appendix 2 39

Appendix 2. Reference streamgages with record extension techniques applied.—Continued

U.S. Geological 

Survey 

streamgage 

number

Name Portion of record extended Index streamgage(s) used to extend record

Correlation 

coefficient between 

log-transformed 

flow records

01603500 Evitts Creek near Centerville, PA Oct 1982–Sep 2008

Town Creek near Oldtown, MD (01609000) 0.94Raystown Branch Juniata River at Saxton, PA (01562000) 0.92

01609000 Town Creek near Oldtown, MD Oct 1959–May 1967 Oct 1981–Apr 2001 Evitts Creek near Centerville, PA (01603500) 0.94 Raystown Branch Juniata River at Saxton, PA (01562000) 0.9301610155 Sideling Hill Creek at Bellegrove, MD Oct 1959–Jun 1967 Oct 1977–Mar 1999 Aughwick Creek near Three Springs, PA (01564500) 0.9001613050 Tonoloway Creek near Needmore, PA Oct 1959–Sep 1965 Aughwick Creek near Three Springs, PA (01564500) 0.9101614090 Conococheague Creek near Fayetteville, PA Oct 1959–Aug 1960 Apr 1981–Sep 2008 Aughwick Creek near Three Springs, PA (01564500) 0.8703007800 Allegheny River at Port Allegany, PA Oct 1959–Sep 1974 Allegheny River at Eldred, PA (03010500) 0.9803009680 Potato Creek at Smethport, PA Oct 1959–Sep 1974 Oct 1995–Sep 2008 Allegheny River at Eldred, PA (03010500) 0.96 Kinzua Creek near Guffey, PA (03011800) 0.9603010655 Oswayo Creek at Shinglehouse, PA Oct 1959–Sep 1974

Allegheny River at Eldred, PA (03010500) 0.95Allegheny River at Salamanca, NY (03011020) 0.94

03011800 Kinzua Creek near Guffey, PA Oct 1959–Sep 1965 West Branch Clarion River at Wilcox, PA (03028000) 0.95

03013000 Conewango Creek at Waterboro, NY Oct 1993–Sep 2008

French Creek at Carters Corners, PA (03021500) 0.93Allegheny River at Salamanca, NY (03011020) 0.91

03015280 Jackson Run near North Warren, PA Oct 1959–Sep 1962 Oct 1978–Sep 2008 Brokenstraw Creek at Youngsville, PA (03015500) 0.94
40 Estimation of Baseline Daily Mean Streamflows for Ungaged Locations on Pennsylvania Streams, WY 1960–2008 Appendix 2. Reference streamgages with record extension techniques applied.—Continued U.S. Geological Survey streamgage number Name Portion of record extended Index streamgage(s) used to extend record Correlation coefficient between log-transformed flow records 03017500 Tionesta Creek at Lynch, PA Oct 1979–Sep 2008 West Branch Clarion River at Wilcox, PA (03028000) 0.96 03021350 French Creek near Wattsburg, PA Oct 1959–Sep 1974 Oil Creek at Rouseville, PA (03020500) 0.89 03021500 French Creek at Carters Corners, PA Oct 1971–Sep 2008 Brokenstraw Creek at Youngsville, PA (03015500) 0.95 Conneaut Creek at Conneaut, OH (04213000) 0.92 03022540 Woodcock Creek at Blooming Valley, PA Oct 1959–Sep 1974 Oct 1995–Sep 2008 Oil Creek at Rouseville, PA (03020500) 0.91 03024000 French Creek at Utica, PA Jul 1970–Sep 2008 Brokenstraw Creek at Youngsville, PA (03015500) 0.96 Conneaut Creek at Conneaut, OH (04213000) 0.93 Conewango Creek at Waterboro, NY (03013000) 0.94 03025000 Sugar Creek at Sugarcreek, PA Nov 1979–Sep 2008 Oil Creek at Rouseville, PA (03020500) 0.96 03029400 Toms Run at Cooksburg, PA Dec 1978–Sep 2008 West Branch Clarion River at Wilcox, PA (3028000) 0.90 03031950 Big Run near Sprankle Mills, PA Oct 1959–Sep 1963 Apr 1981–Sep 2008 Redbank Creek at St. Charles, PA (03032500) 0.90 03038000 Crooked Creek at Idaho, PA Jul 1967–Sep 2008 Little Yellow Creek near Strongstown, PA (03042200) 0.94 Buffalo Creek near Freeport, PA (03049000) 0.92 03039200 Clear Run near Buckstown, PA Sep 1959–Aug 1964 Dec 1978–Sep 2008 Casselman River at Markleton, PA (03079000) 0.92 Casselman River at Grantsville, MD (03078000) 0.90

03039925 North Fork Bens Creek at North Fork Reservoir, PA Oct 1959–Sep 1984 Oct 1998–Sep 2008 Casselman River at Markleton, PA (03079000) 0.88
Appendix 2 41

Appendix 2. Reference streamgages with record extension techniques applied.—Continued

U.S. Geological 

Survey 

streamgage 

number

Name Portion of record extended Index streamgage(s) used to extend record

Correlation 

coefficient between 

log-transformed 

flow records

03041000 Little Conemaugh River at East Conemaugh, PA Oct 1995–Sep 2003 Jul 2004–Sep 2008 Casselman River at Markleton, PA (03079000) 0.8803042200 Little Yellow Creek near Strongstown, PA

Oct 1959–Aug 1960

Dec 1978–Sep 1986

Oct 1988–Sep 2008

West Branch Susquehanna River at Bower, PA (01541000) 0.91Laurel Hill Creek at Ursina, PA (03080000) 0.86

03049800 Little Pine Creek near Etna, PA Oct 1959–Sep 1962

Crooked Creek at Idaho, PA (03038000) 0.89Buffalo Creek near Freeport, PA (03049000) 0.84

03062500 Deckers Creek at Morgantown, WV Oct 1969–Sep 2002

Lick Run at Hopwood, PA (03074300) 0.935Casselman River at Grantsville, MD (03078000) 0.895

03072590 Georges Creek at Smithfield, PA Oct 1959–Sep 1963 Dec 1978–Sep 2008

Deckers Creek at Morgantown, WV (03062500) 0.92South Fork Tenmile Creek at Jefferson, PA (03073000) 0.90Laurel Hill Creek at Ursina, PA (03080000) 0.87

03072840 Tenmile Creek near Clarksville, PA Oct 1959–Nov 1968 Oct 1979–Sep 2008 South Fork Tenmile Creek at Jefferson, PA (03073000) 0.94 Yellow Creek near Hammondsville, OH (03110000) 0.8403073000 South Fork Tenmile Creek at Jefferson, PA Oct 1995–Sep 2008

Deckers Creek at Morgantown, WV (03062500) 0.89Laurel Hill Creek at Ursina, PA (03080000) 0.86

03074300 Lick Run at Hopwood, PA Oct 1959–Sep 1966 Dec 1978–Sep 2008 Deckers Creek at Morgantown, WV (03062500) 0.94 Laurel Hill Creek at Ursina, PA (03080000) 0.8803082200 Poplar Run near Normalville, PA Oct 1959–Aug 1961 Dec 1978–Sep 2008 Laurel Hill Creek at Ursina, PA (03080000) 0.9203084000 Abers Creek near Murrysville, PA Nov 1993–Sep 2008

Little Pine Creek near Etna, PA (03049800) 0.84Buffalo Creek near Freeport, PA (03049000) 0.81

03085956 Montour Run at Scott Station near Imperial, PA Oct 1959–Sep 2000

Little Pine Creek near Etna, PA (03049800) 0.87Short Creek near Dillonvale, OH (03111500) 0.83
42 Estimation of Baseline Daily Mean Streamflows for Ungaged Locations on Pennsylvania Streams, WY 1960–2008 Appendix 2. Reference streamgages with record extension techniques applied.—Continued U.S. Geological Survey streamgage number Name Portion of record extended Index streamgage(s) used to extend record Correlation coefficient between log-transformed flow records 03092000 Kale Creek near Pricetown, OH Oct 1993–Sep 2008 Little Shenango River at Greenville, PA (03102500) 0.85 03102950 Pymatuning Creek at Kinsman, OH Oct 1959–Sep 1965 Oct 1994–Sep 2008 Rock Creek near Rock Creek, OH (04211000) 0.90 Conneaut Creek at Conneaut, OH (04213000) 0.82 03103000 Pymatuning Creek near Orangeville, PA Oct 1964–Sep 2008 Little Shenango River at Greenville, PA (03102500) 0.94 Conneaut Creek at Conneaut, OH (04213000) 0.87 03106500 Slippery Rock Creek at Wurtemburg, PA May 1969–Sep 2008 Little Beaver Creek near East Liverpool, OH (03109500) 0.94 03111150 Brush Run near Buffalo, PA Oct 1959–Sep 1960 Dec 1978–Sep 1982 Oct 1985–Sep 2008 Yellow Creek near Hammondsville, OH (03110000) 0.85 South Fork Tenmile Creek at Jefferson, PA (03073000) 0.85 04213075 Brandy Run near Girard, PA Oct 1959–May 1986 Conneaut Creek at Conneaut, OH (04213000) 0.81
Appendix 3 43

Appendix 3. Basin characteristics used in the development of flow-duration regression equations.—Continued

U.S. Geological 

Survey 

streamgage 

number

Longitude 

(decimal 

degrees)

Drainage 

area 

(square 

miles)

Percent 

impervious 

area

Percent 

carbonate 

bedrock

Mean annual 

precipitation 

(inches)

Mean maximum 

daily temperature 

(degrees 

Fahrenheit)

Soil depth 

to bedrock 

(feet)

Drainage 

runoff 

number 

(unitless)

0142400103 75.280 20.2 0.38 0 43.2 53.2 4.76 3.63

01428750 75.376 40.6 0.28 0 45.4 52.3 4.46 4.06

01429000 75.327 59.7 0.29 0 44.8 52.8 4.57 4.04

01431000 75.222 78.4 0.48 0 42.9 54.7 4.65 3.96

01439500 75.038 117 0.35 0 43.4 55.1 5.05 3.95

01440400 75.215 65.9 0.39 0 44.5 54.3 4.66 3.97

01442500 75.143 259 2.71 0.06 46.3 56.2 4.81 3.93

01447500 75.626 91.7 0.59 0 46.0 53.1 4.88 3.97

01447720 75.606 118 1.67 0 47.6 52.9 5.07 4.10

01448500 75.544 2.39 0.27 0 48.9 53.1 4.75 3.80

01449360 75.503 49.9 2.49 0 47.4 57.2 4.55 3.26

01450500 75.598 76.7 1.70 4.91 45.8 58.5 4.51 3.24

01451500 75.483 80.8 8.24 63.7 45.2 59.9 5.11 3.22

01451800 75.627 53.0 1.62 0 45.6 59.8 3.38 3.10

01452000 75.483 75.8 3.56 11.3 45.4 59.9 3.65 3.11

01452500 75.380 44.5 8.55 62.8 44.6 59.7 4.50 3.19

01459500 75.117 97.4 2.91 0 45.0 60.3 4.43 4.32

01464907 75.120 26.8 13.8 0 45.0 61.7 4.20 4.48

01465798 74.986 21.4 29.2 1.03 47.0 62.0 4.18 4.15

01467048 75.033 49.8 22.7 1.43 45.6 61.9 4.79 3.64

01467086 75.111 16.2 24.5 0 45.0 62.0 5.12 3.29

01468500 76.125 133 4.16 0 48.7 57.2 4.45 3.15

01470500 75.999 355 2.83 0.12 48.7 57.7 4.47 3.13

01470756 75.883 159 1.51 10.8 46.8 59.8 3.84 3.13

01470779 76.172 66.5 4.12 83.2 43.3 60.0 5.16 3.23

01471000 75.979 211 3.29 41.3 44.7 59.8 4.40 3.20

01471980 75.680 85.5 0.94 26.1 46.0 60.3 5.13 3.33

01472000 75.652 1,147 3.85 18.7 46.5 58.6 4.43 3.22

01472157 75.602 59.1 0.47 0.62 44.9 60.2 4.90 3.39

01472174 75.631 5.98 3.65 0 45.0 60.3 5.09 3.30

01472198 75.516 38.0 1.72 3.35 45.3 60.3 4.83 3.44

01472199 75.523 23.0 1.01 4.76 46.2 60.3 4.85 3.47

01473120 75.434 53.7 9.60 0 43.1 61.8 4.13 3.93

01475510 75.273 37.4 15.7 0 44.7 61.6 4.85 3.57

01475530 75.280 4.78 22.8 0 45.0 61.9 5.03 3.36

01475850 75.437 15.8 3.62 0 45.0 60.7 4.93 3.71

01479820 75.692 28.3 3.73 11.1 45.0 60.8 5.13 3.29

01480300 75.861 18.7 1.37 3.36 45.0 59.8 5.08 3.28

01480675 75.742 8.57 0.64 0.39 45.0 60.0 5.09 3.30

01481000 75.594 287 3.40 7.63 45.0 60.5 5.11 3.36

01514000 76.271 185 0.35 0 37.0 53.8 4.44 3.78

01516500 77.015 12.2 0.39 0 34.8 54.2 4.64 4.05
44 Estimation of Baseline Daily Mean Streamflows for Ungaged Locations on Pennsylvania Streams, WY 1960–2008

Appendix 3. Basin characteristics used in the development of flow-duration regression equations.—Continued

U.S. Geological 

Survey 

streamgage 

number

Longitude 

(decimal 

degrees)

Drainage 

area 

(square 

miles)

Percent 

impervious 

area

Percent 

carbonate 

bedrock

Mean annual 

precipitation 

(inches)

Mean maximum 

daily temperature 

(degrees 

Fahrenheit)

Soil depth 

to bedrock 

(feet)

Drainage 

runoff 

number 

(unitless)

01517000 76.965 10.2 0.27 0 35.7 54.0 4.48 4.09

01518500 77.149 122 0.29 0 33.1 55.3 4.38 3.75

01518862 77.532 90.6 0.31 0 36.3 54.6 4.50 3.77

01520000 77.140 298 0.26 0 34.1 55.2 4.53 3.80

01525500 77.418 340 0.71 0 34.9 54.5 4.57 3.80

01529500 77.217 470 0.61 0 32.4 54.8 4.65 3.63

01530500 76.798 77.5 3.49 0 34.5 55.6 4.24 3.86

01532000 76.485 215 0.30 0 36.2 54.8 4.54 4.04

01532850 76.007 5.67 0.14 0 40.1 53.8 4.87 3.99

01533950 75.642 12.6 0.84 0 42.3 54.3 3.98 3.77

01534000 75.895 383 0.76 0 40.3 55.1 4.47 4.00

01538000 76.094 43.8 3.08 0 43.7 56.0 4.47 4.00

01539000 76.431 274 0.42 0 42.1 56.2 4.50 3.84

01541000 78.677 315 0.69 0 44.3 56.2 4.50 3.57

01541308 78.584 6.77 3.58 0 47.7 55.0 4.79 3.11

01541500 78.406 371 0.52 0 41.7 56.3 4.46 3.58

01542500 78.109 1,462 0.74 0 41.9 55.6 4.52 3.52

01542810 78.293 5.24 0.02 0 43.1 55.0 4.68 3.59

01543000 78.197 272 0.24 0 43.4 55.3 4.66 3.65

01543500 78.103 685 0.20 0 43.4 53.9 4.60 3.65

01544500 77.826 136 0.05 0 39.9 54.8 4.58 3.49

01545600 77.691 46.2 0.02 0 41.7 54.8 4.77 3.16

01546400 77.828 58.5 5.63 75.1 39.4 57.2 5.25 3.16

01546500 77.794 87.2 6.19 83.1 38.8 57.6 5.39 3.16

01547100 77.787 142 5.01 78.3 38.5 57.9 5.40 3.16

01547200 77.787 265 3.08 46.0 38.2 57.5 4.75 3.11

01547700 77.606 44.1 0.45 0.35 39.0 57.2 4.01 2.99

01547950 77.703 152 0.29 0 40.1 55.9 4.75 3.18

01548005 77.550 562 1.81 27.4 39.0 55.8 4.63 3.11

01548500 77.448 604 0.23 0 36.3 53.8 4.40 3.67

01549500 77.231 37.7 0.55 0 36.2 54.3 4.38 4.02

01549700 77.324 944 0.20 0 36.9 54.3 4.47 3.55

01549780 77.163 6.80 0.35 0 41.9 54.9 4.50 3.83

01550000 77.033 173 0.13 0 36.7 53.3 4.14 3.84

01552000 76.913 435 0.20 0 39.8 54.6 4.36 3.95

01552500 76.535 23.8 0.15 0 45.4 53.5 4.42 4.03

01553130 77.077 4.93 0.74 0 45.0 54.9 4.78 3.10

01555000 77.049 301 0.54 24.0 43.7 57.5 4.86 3.16

01555500 76.912 162 0.86 0 42.7 58.3 4.62 3.11

01556000 78.200 291 3.79 21.0 39.6 57.8 4.69 3.13

01556500 78.294 93.7 4.25 5.13 40.5 56.2 4.40 3.10

01557500 78.234 44.1 1.03 5.04 38.9 56.4 4.11 3.05
Appendix 3 45

Appendix 3. Basin characteristics used in the development of flow-duration regression equations.—Continued

U.S. Geological 

Survey 

streamgage 

number

Longitude 

(decimal 

degrees)

Drainage 

area 

(square 

miles)

Percent 

impervious 

area

Percent 

carbonate 

bedrock

Mean annual 

precipitation 

(inches)

Mean maximum 

daily temperature 

(degrees 

Fahrenheit)

Soil depth 

to bedrock 

(feet)

Drainage 

runoff 

number 

(unitless)

01558000 78.141 220 2.67 20.5 39.6 56.0 4.58 3.10

01559000 78.019 816 2.33 32.6 39.2 56.4 4.79 3.12

01559700 78.619 5.28 0.22 1.73 39.0 58.2 4.04 3.10

01560000 78.493 172 0.96 4.27 38.7 57.4 4.01 3.08

01562000 78.266 756 1.09 14.2 38.0 57.8 4.30 3.06

01564500 77.926 205 0.73 4.46 38.3 59.0 3.93 3.04

01565000 77.583 164 1.22 24.8 41.2 58.5 4.90 3.13

01565700 77.312 6.52 1.82 47.8 41.3 59.8 4.26 3.12

01566000 77.419 214 0.33 0 39.4 58.7 4.22 3.12

01567500 77.403 15.0 0.63 0 39.9 59.4 5.40 3.24

01568000 77.169 207 0.65 0 39.6 58.8 4.83 3.19

01569000 76.908 33.2 0.12 0 43.2 57.9 4.79 3.10

01570000 77.021 470 2.99 38.1 39.1 61.0 4.61 3.18

01571500 76.898 216 4.10 34.2 40.5 60.2 5.23 3.35

01572000 76.378 34.3 0.75 0 46.6 58.5 4.22 3.10

01574500 76.854 75.5 2.60 16.8 39.8 61.9 4.46 2.95

01576754 76.368 470 6.97 59.0 42.4 60.3 5.02 3.30

01576787 76.329 148 2.13 57.5 41.7 60.0 5.28 3.24

01577500 76.316 133 0.48 0.33 41.6 61.4 5.09 3.30

01578400 76.114 5.98 0.24 25.4 41.0 59.9 5.09 3.30

01603500 78.647 30.2 0.53 21.8 38.0 58.9 4.68 3.15

01609000 78.555 148 0.35 0 37.1 60.6 3.90 3.00

01610155 78.344 102 0.51 0 37.0 60.3 3.18 2.80

01612500 78.232 16.9 1.22 0 37.0 61.6 3.33 2.90

01613050 78.133 10.7 0.31 0 38.5 59.2 4.03 2.95

01614090 77.440 5.05 0.09 0 45.0 59.1 5.00 3.20

01614500 77.825 494 2.86 0 40.3 60.3 4.67 3.15

01639000 77.235 173 1.14 0 41.4 61.6 4.42 3.60

03007800 78.293 248 0.37 0 40.4 54.0 4.71 3.64

03009680 78.431 160 0.25 0 44.4 53.9 4.65 3.67

03010500 78.386 550 0.31 0 42.0 53.0 4.69 3.67

03010655 78.198 98.7 0.12 0 39.1 54.4 4.54 3.48

03011800 78.719 38.8 0.46 0 45.0 53.1 4.63 3.57

03013000 79.069 290 0.44 0 43.7 54.8 4.73 3.97

03015280 79.238 12.8 0.39 0 45.2 54.9 5.86 4.41

03015500 79.318 321 0.48 0 46.8 55.5 5.65 4.23

03017500 79.050 233 0.29 0 44.1 54.1 4.69 3.50

03020500 79.696 300 0.48 0 44.5 55.5 5.87 4.15

03021350 79.783 92.0 0.46 0 47.0 55.9 5.18 4.44

03021500 79.877 208 0.52 0 46.5 55.9 5.29 4.42

03022540 80.048 31.1 0.41 0 45.0 56.3 6.08 4.63

03024000 79.956 1,028 1.16 0 45.0 56.1 5.76 4.53
46 Estimation of Baseline Daily Mean Streamflows for Ungaged Locations on Pennsylvania Streams, WY 1960–2008

Appendix 3. Basin characteristics used in the development of flow-duration regression equations.—Continued

U.S. Geological 

Survey 

streamgage 

number

Longitude 

(decimal 

degrees)

Drainage 

area 

(square 

miles)

Percent 

impervious 

area

Percent 

carbonate 

bedrock

Mean annual 

precipitation 

(inches)

Mean maximum 

daily temperature 

(degrees 

Fahrenheit)

Soil depth 

to bedrock 

(feet)

Drainage 

runoff 

number 

(unitless)

03025000 79.880 166 0.45 0 43.8 56.3 5.94 4.04

03026500 78.577 7.84 0.14 0 45.0 53.1 4.63 3.56

03028000 78.693 63.0 0.32 0 45.0 53.4 4.63 3.62

03029400 79.214 12.6 0.15 0 45.0 55.9 4.72 3.93

03031950 79.091 7.38 0.56 0 45.0 57.0 4.61 4.01

03032500 79.394 528 1.31 0 43.2 55.9 4.31 3.78

03038000 79.349 191 1.08 0 44.3 58.8 3.40 3.14

03039200 78.833 3.68 0.29 0 42.7 54.5 4.69 3.21

03039925 79.017 3.45 0.03 0 45.9 54.6 4.69 3.21

03042200 78.946 7.36 0.27 0 46.3 55.8 4.66 3.26

03049000 79.700 137 0.85 0 41.0 59.4 3.71 3.21

03049800 79.938 5.78 4.56 0 39.0 60.0 3.95 3.45

03062500 79.953 63.2 3.28 0 47.9 60.0 3.72 3.20

03072590 79.796 16.3 4.94 0 44.1 60.0 4.29 3.34

03072840 80.042 133 0.59 0 39.0 59.8 4.78 3.62

03073000 80.073 180 0.97 0 39.5 60.0 4.78 3.64

03074300 79.694 3.80 1.35 0 46.8 56.9 4.53 3.06

03078000 79.136 62.5 0.42 0 42.2 55.6 3.67 3.37

03079000 79.228 382 0.92 0 41.7 55.7 4.22 3.40

03080000 79.322 121 0.40 0 46.2 55.5 4.47 3.33

03082200 79.426 9.27 0.71 0 45.0 56.6 4.60 3.33

03084000 79.714 4.39 23.7 0 39.0 60.1 3.69 3.29

03085956 80.176 25.4 17.9 0 37.0 59.8 3.93 3.35

03092000 80.990 21.9 1.08 0 37.0 59.0 4.86 4.83

03093000 80.950 97.6 1.62 0 38.4 58.9 4.61 4.52

03102500 80.376 104 1.06 0 40.5 58.0 6.12 4.56

03102950 80.590 96.7 0.82 0 39.6 58.4 5.27 4.69

03103000 80.478 169 0.79 0 39.4 58.5 5.61 4.47

03106000 80.243 356 3.70 0 39.1 59.3 4.33 3.58

03106500 80.234 398 1.42 0 40.7 58.8 5.51 3.96

03109500 80.540 496 1.83 0 37.0 59.9 5.05 3.69

03110000 80.730 147 0.34 0 38.0 59.8 3.81 3.16

03111150 80.408 10.3 0.47 0 39.0 60.0 4.82 3.60

03111500 80.730 123 1.09 0 38.9 60.0 4.80 3.63

04213000 80.600 175 1.25 0 42.1 56.5 5.34 5.13

04213075 80.291 4.45 3.09 0 42.9 56.5 5.04 5.44
Appendix 4 47

Appendix 4. Flow-duration exceedance probabilities, observed and computed from streamflow data, and regression equations for streamgages used in regression analysis.—Continued[--, no data; Pn, n probability exceedance]

U.S. Geological 

Survey 

streamgage 

number

Type

Flow-duration exceedance, in cubic feet per second

P99.9944 P99 P95 P90 P85 P80 P70 P60 P50 P40 P30 P20 P15 P10 P05 P01 P0.0056

0142400103 Observed -- 0.40 0.80 1.40 2.20 3.30 7.00 11.0 18.0 25.0 35.0 50.0 63.0 83.0 122 270 --

Predicted 0.98 1.88 3.31 4.41 5.80 7.24 10.7 14.7 22.4 29.1 38.8 54.3 65.5 84.8 126 272 2,150

01428750 Observed -- 5.80 8.00 10.0 13.0 16.0 24.0 33.0 45.0 59.0 77.0 108 136 181 292 664 --

Predicted 0.97 2.49 5.00 7.36 9.94 13.0 21.1 31.3 55.0 70.8 90.3 128 156 198 283 572 4,110

01429000 Observed -- 8.20 11.0 15.0 19.0 23.0 33.0 44.0 60.0 84.0 115 160 194 252 379 848 --

Predicted 1.73 4.25 8.09 11.7 15.6 20.2 31.7 45.9 77.4 100 126 179 221 282 404 818 5,960

01431000 Observed -- 3.61 6.70 9.80 13.0 17.0 29.0 42.0 60.0 86.0 125 180 224 299 452 1,127 --

Predicted 2.55 6.06 10.9 15.2 20.1 25.6 38.9 55.1 83.6 107 133 191 241 314 468 994 7,820

01439500 Observed 2.63 9.00 17.0 27.0 38.0 52.0 85.0 120 160 210 271 362 428 526 706 1,270 8,840

Predicted 7.17 14.6 23.2 31.3 39.8 49.1 70.0 92.9 130 165 202 288 364 473 703 1,475 11,680

01440400 Observed 5.11 7.60 12.0 17.0 23.0 30.0 48.0 66.0 87.0 111 143 196 237 301 435 918 6,040

Predicted 2.37 5.48 10.0 14.1 18.6 23.8 36.3 51.3 79.0 101 125 177 220 284 417 871 6,640

01442500 Observed 30.0 50.0 73.0 95.0 119 145 207 274 356 454 590 805 966 1,220 1,750 3,500 29,040

Predicted 16.4 39.1 60.9 85.0 106 132 187 242 337 419 498 697 872 1,120 1,640 3,330 24,450

01447500 Observed 7.04 14.0 23.0 32.0 42.5 53.0 78.0 102 130 162 205 270 320 394 551 1,100 15,830

Predicted 4.71 10.1 17.1 24.1 31.0 39.2 58.3 80.2 126 162 206 290 355 449 639 1,270 8,630

01447720 Observed -- 30.0 42.0 54.0 67.0 81.0 110 141 179 220 275 360 436 545 783 1,580 --

Predicted 7.50 16.5 26.8 38.0 47.7 59.5 86.3 116 182 231 288 403 494 619 866 1,670 10,980

01448500 Observed 0.25 0.42 0.66 0.89 1.20 1.40 1.90 2.50 3.20 4.00 5.10 6.70 7.80 9.6 14.0 30.0 153

Predicted 0.09 0.18 0.38 0.54 0.74 0.95 1.51 2.23 3.52 4.46 5.71 7.64 9.08 11.5 16.9 37.6 276

01449360 Observed -- 15.0 22.0 28.0 32.0 38.0 49.0 61.0 76.0 93.0 113 144 168 204 278 520 --

Predicted 4.77 8.55 13.4 17.7 22.5 28.0 38.8 49.0 62.4 77.5 99.4 132 156 202 305 668 4,920

01450500 Observed 9.21 18.0 27.0 35.0 42.0 49.0 64.0 80.0 100 125 158 206 246 306 440 900 4,340

Predicted 6.70 11.8 18.6 24.3 31.0 38.7 54.0 68.8 83.4 104 132 178 211 274 415 914 6,950

01451500 Observed 23.0 28.0 35.0 41.0 45.0 50.0 60.0 70.0 82.0 95.0 112 136 151 175 224 420 4,540

Predicted 14.9 29.3 35.2 42.7 49.9 56.5 66.9 74.8 80.4 100 124 167 180 211 277 547 4,630

01451800 Observed -- 3.50 7.20 11.0 15.0 19.0 27.0 36.0 49.0 65.0 89.0 127 159 212 325 749 --

Predicted 0.99 2.61 5.62 8.12 11.5 15.8 26.2 38.6 53.5 66.6 84.6 112 135 179 283 658 5,130

01452000 Observed 0.00 3.70 7.70 12.0 17.0 22.0 33.0 45.0 62.0 83.0 112 157 194 253 389 937 6,640

Predicted 2.33 5.99 11.2 15.5 21.0 27.8 42.3 58.0 76.6 95.0 120 160 188 242 367 818 6,550

01452500 Observed 5.27 11.0 17.0 21.0 24.0 26.0 31.0 36.0 42.0 50.0 60.0 75.0 85.0 99.0 127 238 2,090

Predicted 3.64 8.86 12.5 15.9 19.6 23.1 29.7 35.7 42.3 52.7 66.0 88.7 95.7 113 150 304 2,680

01459500 Observed -- 0.90 2.10 3.80 5.40 7.40 14.0 24.0 37.0 56.0 87.0 145 204 325 610 1,790 --

Predicted 1.87 6.25 12.1 18.2 24.2 31.4 49.7 73.0 96.8 119 126 179 240 319 506 1,170 9,720
48 Estimation of Baseline Daily Mean Streamflows for Ungaged Locations on Pennsylvania Streams, WY 1960–2008 Appendix 4. Flow-duration exceedance probabilities, observed and computed from streamflow data, and regression equations for streamgages used in regression analysis.—Continued [--, no data; Pn, n probability exceedance] U.S. Geological Survey streamgage number Type Flow-duration exceedance, in cubic feet per second P99.9944 P99 P95 P90 P85 P80 P70 P60 P50 P40 P30 P20 P15 P10 P05 P01 P0.0056 01464907 Observed -- 1.60 2.60 4.40 6.20 7.90 11.0 14.0 19.0 25.0 34.0 49.0 65.0 97.0 196 668 -- Predicted 0.26 1.70 3.22 4.93 6.40 7.89 11.9 17.3 24.3 29.8 30.4 42.7 58.7 79.0 130 324 2,860 01465798 Observed -- 1.70 3.20 4.20 5.20 6.00 7.80 9.70 12.0 15.0 19.0 28.0 39.0 61.0 125 409 -- Predicted 0.34 3.58 5.16 7.51 8.85 9.87 12.3 15.3 21.6 26.1 27.0 37.0 49.1 65.4 107 265 2,330 01467048 Observed -- 13.0 17.0 21.0 24.0 27.0 34.0 42.0 50.0 61.0 75.0 99.0 121 169 285 810 -- Predicted 3.49 18.1 21.0 27.0 30.4 32.7 36.7 40.5 47.6 57.8 64.4 87.5 112 150 243 588 5,130 01467086 Observed -- 4.00 6.00 7.20 8.10 9.00 11.0 13.0 16.0 19.0 23.0 29.0 35.3 48.0 81.0 202 -- Predicted 2.27 9.38 9.61 11.4 12.4 12.7 13.0 13.3 14.3 17.5 20.6 27.5 34.3 46.3 77.1 197 1,780 01468500 Observed -- 46.0 62.0 75.0 89.0 102 129 160 197 242 303 391 455 557 756 1,500 -- Predicted 14.9 28.1 41.1 54.4 67.5 83.7 113 139 179 224 295 389 452 580 855 1,780 11,540 01470500 Observed 40.8 91.0 127 158 191 223 289 364 458 577 741 998 1,200 1,490 2,100 4,230 32,480 Predicted 49.9 86.6 121 160 196 245 326 392 487 604 789 1,040 1,220 1,560 2,280 4,620 29,650 01470756 Observed -- 17.0 30.0 42.0 52.0 64.0 88 115 150 190 250 348 434 570 856 2,050 -- Predicted 7.22 15.5 27.5 38.2 50.9 67.4 102 138 176 218 276 367 428 548 814 1,740 12,640 01470779 Observed -- 27.0 34.0 42.0 47.0 52.0 61.0 73.0 85.0 99.0 117 142 159 188 254 515 -- Predicted 9.65 15.8 20.6 25.0 30.2 35.1 44.3 52.8 56.0 71.4 91.2 124 132 152 195 381 3,140 01471000 Observed -- 50.0 65.0 85.0 98.0 113.0 140 171 212 265 335 430 501 607 833 1,700 -- Predicted 16.9 33.7 49.8 64.9 81.8 101.3 139 174 206 259 329 446 499 606 831 1,660 12,640 01471980 Observed -- 21.0 28.0 34.0 39.0 44.0 56.0 69.0 85.0 105 129 169 197 246 369 889 -- Predicted 14.1 20.3 28.2 35.6 43.6 52.5 69.1 83.8 87.2 108 131 177 206 257 372 795 6,280 01472000 Observed 175 260 367 457 545 636 820 1,030 1,300 1,630 2,070 2,690 3,160 3,850 5,200 9,830 70,260 Predicted 144 289 383 502 609 752 979 1,150 1,410 1,740 2,210 3,000 3,440 4,280 5,930 11,280 78,480 01472157 Observed -- 11.0 16.0 20.0 24.0 27.0 36.0 46.0 58.0 72.0 90.0 116 136 173 256 625 -- Predicted 6.06 9.62 14.7 19.0 24.0 29.4 40.6 51.8 56.3 70.1 85.0 115 143 190 303 712 5,670 01472174 Observed -- 1.60 2.40 2.80 3.20 3.6 4.40 5.40 6.60 8.00 9.50 12.0 13.0 17.0 26.0 93.6 -- Predicted 0.63 1.04 1.59 1.99 2.50 3.0 3.95 4.99 5.31 6.65 8.16 10.8 13.4 17.9 29.6 76.2 650 01472198 Observed -- 8.70 13.0 15.0 18.0 20.0 25.0 32.0 40.0 50.0 61.1 79.0 92.0 115 171 442 -- Predicted 3.25 5.75 9.04 11.8 15.0 18.4 25.6 33.0 36.6 45.4 54.3 73.3 90.8 120 190 450 3,670 01472199 Observed -- 4.80 6.70 8.00 9.40 11.0 14.0 19.0 25.0 31.0 38.0 49.0 58.0 74.0 111 281 -- Predicted 1.89 3.22 5.29 7.00 8.97 11.1 15.8 20.7 23.0 28.4 33.7 45.2 55.7 73.0 115 275 2,250 01473120 Observed -- 2.20 4.60 6.48 8.10 9.8 14.0 20.0 28.0 40.0 54.0 79.0 101 144 293 1,060 --

Predicted 0.84 3.74 6.72 9.68 12.7 15.7 23.4 33.0 43.0 53.6 59.2 82.9 111 150 248 614 5,320

01475510 Observed -- 12.0 17.0 20.0 23.0 26.0 31.0 37.0 45.0 52.0 61.0 75.0 86.0 107 172 443 --

Predicted 2.70 9.87 12.6 16.1 18.9 21.0 25.1 29.2 33.4 41.1 47.1 64.2 82.2 111 181 446 3,850
Appendix 4 49

Appendix 4. Flow-duration exceedance probabilities, observed and computed from streamflow data, and regression equations for streamgages used in regression analysis.—Continued[--, no data; Pn, n probability exceedance]

U.S. Geological 

Survey 

streamgage 

number

Type

Flow-duration exceedance, in cubic feet per second

P99.9944 P99 P95 P90 P85 P80 P70 P60 P50 P40 P30 P20 P15 P10 P05 P01 P0.0056

01475530 Observed -- 1.50 1.80 2.20 2.50 2.80 3.20 3.90 4.40 5.10 5.80 7.40 8.90 12.0 23.0 65.1 --

Predicted 0.44 1.81 2.12 2.57 2.91 3.04 3.34 3.66 4.03 4.98 5.84 7.75 9.74 13.2 22.3 59.6 549

01475850 Observed -- 2.70 4.50 5.90 7.10 8.40 11.0 13.0 15.0 18.0 22.0 27.0 32.0 40.0 62.9 182 --

Predicted 0.91 1.96 3.24 4.34 5.53 6.72 9.52 12.7 14.4 17.8 20.4 27.8 35.7 47.8 78.4 196 1,670

01479820 Observed -- 5.31 11.0 13.0 15.0 17.0 20.0 24.0 29.0 34.0 40.0 49.0 54.0 64.0 95.7 324 --

Predicted 3.94 6.43 8.94 11.1 13.6 15.9 20.6 24.9 25.8 32.2 39.2 52.6 63.4 82.6 129 305 2,520

01480300 Observed 1.00 3.20 5.60 6.80 7.80 8.80 11.0 13.0 15.0 18.0 22.0 27.0 32.0 42.0 77.0 257 1,620

Predicted 2.28 3.34 5.01 6.29 7.90 9.48 12.8 16.2 17.3 21.8 27.2 36.4 44.3 58.6 93.4 225 1,800

01480675 Observed -- 0.72 1.50 2.10 2.60 3.20 4.40 6.00 7.90 9.90 12.0 16.0 19.0 25.0 42.0 97.0 --

Predicted 0.94 1.33 2.11 2.65 3.38 4.08 5.65 7.29 7.75 9.73 12.0 16.1 19.7 26.4 43.1 108 898

01481000 Observed 41.4 69.0 100 118 138 158 193 231 274 325 393 498 575 700 985 2,240 9,540

Predicted 49.5 84.0 106 133 158 187 234 272 285 353 427 583 712 928 1,410 3,080 23,600

01514000 Observed 8.90 11.0 14.0 18.0 23.0 29.0 49.0 79.0 117 170 250 374 484 680 1,100 2,420 9,550

Predicted 3.43 8.83 15.7 20.9 28.3 35.6 55.0 80.8 131 180 249 374 476 636 969 2,060 15,500

01516500 Observed 0.00 0.06 0.26 0.50 0.74 1.00 1.80 2.90 4.60 6.90 10.0 16.0 21.0 28.0 47.0 123 1,910

Predicted 0.10 0.28 0.59 0.79 1.12 1.41 2.35 3.87 6.34 9.04 12.4 18.9 25.0 34.3 55.7 136 1,080

01517000 Observed -- 0.00 0.00 0.14 0.40 0.60 1.10 2.10 3.40 5.10 8.00 13.0 18.0 26.0 44.0 115 --

Predicted 0.07 0.21 0.46 0.64 0.91 1.16 2.00 3.37 5.75 8.14 11.1 16.8 22.1 30.1 48.4 117 917

01518500 Observed -- 2.60 4.30 6.10 8.00 10.0 14.0 22.0 34.0 54.0 88.0 145 191 266 442 1,110 --

Predicted 1.23 3.42 6.34 8.25 11.5 14.4 23.0 35.8 56.1 80.4 114 176 233 322 523 1,220 9,400

01518862 Observed -- 1.60 3.30 5.30 7.3 9.9 18.0 29.0 47.0 69.8 100 153 194 257 402 1,020 --

Predicted 1.27 3.23 5.96 7.96 10.9 13.7 22.0 34.0 53.9 76.2 108 162 209 282 443 994 6,770

01520000 Observed -- 3.00 6.20 10.0 15.0 21.0 36.0 60.0 95.0 150 230 370 490 694 1,200 3,000 --

Predicted 4.33 11.4 19.7 25.6 34.7 43.2 66.8 100 155 219 307 473 624 854 1,350 3,000 21,910

01525500 Observed -- 20.0 25.0 31.0 36.0 42.0 58.0 82.0 120 175 261 427 565 806 1,340 3,340 --

Predicted 5.42 14.3 24.1 31.6 42.4 52.7 81.0 121 191 272 387 593 774 1,050 1,630 3,520 24,010

01529500 Observed 8.48 27.0 39.0 51.0 64.0 76.0 110 155 218 302 424 640 820 1,120 1,700 3,610 21,910

Predicted 9.00 21.9 34.2 42.3 56.2 68.0 100 144 216 312 457 713 934 1,290 2,050 4,520 33,420

01530500 Observed 1.70 6.70 9.80 13.0 15.0 17.0 23.0 29.0 39.0 51.0 71.0 106 135 188 307 792 3,030

Predicted 0.64 2.24 4.26 5.73 7.94 9.9 15.8 24.6 39.8 55.9 76.3 116 154 212 343 805 6,380

01532000 Observed 0.78 3.60 8.90 14.0 21.0 30.0 52.0 80.0 120 170 246 377 482 662 1,080 2,670 24,620

Predicted 2.98 8.47 15.4 21.0 28.5 35.9 56.7 86.1 137 190 252 384 507 684 1,060 2,310 17,410

01532850 Observed -- 0.20 0.43 0.63 0.90 1.20 2.00 3.00 4.20 6.00 8.00 12.0 15.0 21.0 34.0 107 --

Predicted 0.11 0.26 0.52 0.70 0.96 1.20 1.92 2.95 4.62 6.22 8.15 11.8 15.0 19.8 30.9 73.0 591
50 Estimation of Baseline Daily Mean Streamflows for Ungaged Locations on Pennsylvania Streams, WY 1960–2008 Appendix 4. Flow-duration exceedance probabilities, observed and computed from streamflow data, and regression equations for streamgages used in regression analysis.—Continued [--, no data; Pn, n probability exceedance] U.S. Geological Survey streamgage number Type Flow-duration exceedance, in cubic feet per second P99.9944 P99 P95 P90 P85 P80 P70 P60 P50 P40 P30 P20 P15 P10 P05 P01 P0.0056 01533950 Observed -- 0.30 0.90 1.40 1.90 2.30 3.50 5.10 7.10 9.6 14.0 21.0 27.0 37.0 63.0 175 -- Predicted 0.14 0.41 0.95 1.38 1.97 2.63 4.50 7.14 12.2 16.0 20.9 29.4 36.5 47.8 73.0 165 1,320 01534000 Observed 7.10 21.0 35.0 51.0 66.0 85.0 132 191 270 370 520 767 957 1,270 1,930 4,330 25,730 Predicted 8.63 23.7 41.7 58.4 77.4 99.0 153 220 344 454 577 850 1,100 1,440 2,150 4,430 32,310 01538000 Observed 1.57 4.50 6.70 9.10 12.0 14.0 22.0 31.0 41.0 53.0 70.0 94.0 112 140 200 422 2,600 Predicted 0.90 2.65 5.03 7.26 9.68 12.4 19.4 28.8 44.0 57.0 70.3 99.5 127 166 253 559 4,050 01539000 Observed 8.40 19.0 35.0 54.0 76.0 100.0 150 208 278 369 498 692 846 1,080 1,570 3,210 25,580 Predicted 7.84 19.1 33.2 46.5 61.4 78.8 121 174 255 334 426 613 780 1,020 1,540 3,250 22,040 01541000 Observed 16.0 29.0 48.0 63.0 80.0 99.0 146 207 290 400 551 795 987 1,290 1,910 4,010 20,310 Predicted 10.9 23.1 38.9 54.7 71.4 92.0 144 210 305 413 574 803 986 1,280 1,900 3,890 19,230 01541308 Observed -- 1.40 2.00 2.50 3.00 3.60 4.80 6.20 7.70 9.8 13.0 17.0 21.0 26.0 40.0 89.0 -- Predicted 0.50 0.81 1.32 1.74 2.23 2.72 3.96 5.44 7.56 10.2 15.1 19.8 22.6 29.0 43.6 98.4 513 01541500 Observed -- 23.0 41.0 54.0 68.0 86.0 130 190 278 398 575 850 1,060 1,380 2,010 4,350 -- Predicted 10.6 23.6 39.7 54.7 72.0 92.3 144 211 308 421 588 841 1,050 1,380 2,080 4,330 23,180 01542500 Observed -- 147 200 250 310 400 620 916 1,260 1,800 2,588 3,740 4,560 5,770 8,100 15,000 -- Predicted 63.6 136 205 277 354 449 664 916 1,340 1,820 2,570 3,690 4,550 5,930 8,650 16,850 87,960 01542810 Observed -- 0.10 0.24 0.43 0.62 0.85 1.50 2.40 3.60 5.20 7.50 11.0 15.0 21.0 35.0 84.0 -- Predicted 0.12 0.23 0.47 0.65 0.89 1.13 1.87 2.95 4.42 6.08 8.58 11.9 14.5 19.1 29.7 70.2 416 01543000 Observed 0.46 6.80 17.0 26.0 38.0 52.0 92.0 142 210 294 430 652 815 1,100 1,680 3,660 17,550 Predicted 10.2 21.0 34.8 48.3 62.8 80.1 123 178 263 357 495 700 863 1,120 1,650 3,360 17,710 01543500 Observed 1.74 22.0 44.0 71.0 105.0 152.0 262 404 580 808 1,160 1,720 2,140 2,780 4,100 8,200 42,030 Predicted 27.9 58.6 93.8 130 168 215 326 462 728 989 1,400 2,000 2,440 3,130 4,450 8,508 42,940 01544500 Observed 1.20 6.60 11.0 17.0 23.0 32.0 53.0 80.0 111 159 223 330 411 543 812 1,730 9,670 Predicted 4.24 8.54 14.4 19.1 25.3 31.8 48.7 70.6 106 146 211 304 375 495 750 1,600 9,600 01545600 Observed -- 2.00 3.80 6.20 9.10 13.0 21.0 31.0 42.0 56.0 77.0 109 133 170 248 489 -- Predicted 3.09 4.66 7.32 9.21 12.0 14.7 21.2 28.8 39.6 54.0 80.7 112 132 173 264 578 3,510 01546400 Observed -- 16.0 19.0 22.0 25.0 28.0 34.0 41.0 50.0 60.0 73.0 92.0 108 132 178 375 -- Predicted 5.79 10.2 12.8 15.0 18.2 20.5 25.9 32.1 38.5 52.9 76.8 108 115 135 175 342 2,390 01546500 Observed 20.0 25.0 35.0 41.0 45.0 48.0 55.0 63.0 74.0 87.0 104 128 145 169 216 392 2,720 Predicted 10.2 17.8 21.0 24.1 28.8 32.0 39.2 47.2 54.9 75.5 109 155 164 191 245 470 3,340 01547100 Observed -- 104 120 129 137 143 155 172 192 215 248 290 322 370 471 793 --

Predicted 17.6 29.1 34.2 39.2 46.8 52.3 64.1 77.1 87.9 121 175 248 266 312 404 774 5,470

01547200 Observed 79.0 92.6 121 135 146 157 186 221 265 325 410 541 638 799 1,170 2,310 14,880

Predicted 17.9 32.6 43.8 52.5 65.9 77.9 104 133 166 229 335 479 536 660 909 1,800 12,180
Appendix 4 51

Appendix 4. Flow-duration exceedance probabilities, observed and computed from streamflow data, and regression equations for streamgages used in regression analysis.—Continued[--, no data; Pn, n probability exceedance]

U.S. Geological 

Survey 

streamgage 

number

Type

Flow-duration exceedance, in cubic feet per second

P99.9944 P99 P95 P90 P85 P80 P70 P60 P50 P40 P30 P20 P15 P10 P05 P01 P0.0056

01547700 Observed 0.00 0.82 2.10 3.40 4.80 6.60 11.0 18.0 26.0 38.0 56.0 86.0 107 142 223 500 4,460

Predicted 1.15 2.21 4.02 5.16 7.12 9.11 14.2 20.6 28.4 39.0 57.9 80.9 97.3 132 211 499 3,380

01547950 Observed -- 15.0 23.0 34.0 47.0 60.0 93.0 125 164 218 292 391 468 590 833 1,550 --

Predicted 10.0 16.0 23.8 29.5 37.9 46.3 65.3 87 116 158 233 330 398 528 811 1,760 10,830

01548005 Observed 80.0 117 142 160 181 201 252 324 430 575 784 1,100 1,350 1,700 2,440 4,980 18,440

Predicted 40.2 71.1 96.5 118 148 179 241 308 413 567 848 1,214 1,380 1,730 2,400 4,640 29,460

01548500 Observed 8.71 30.0 47.0 66.0 89.0 118.0 190 283 406 578 825 1,240 1,570 2,050 3,050 6,380 38,440

Predicted 11.3 28.5 47.9 63.5 85.1 107.5 166 244 400 564 821 1,240 1,580 2,100 3,160 6,480 41,220

01549500 Observed 0.02 1.10 2.40 3.70 5.50 7.70 13.0 19.0 28.0 39.0 54.0 81.0 101 133 205 495 3,110

Predicted 0.30 0.90 1.87 2.61 3.69 4.73 8.01 13.2 22.4 31.6 43.4 65.5 86.0 116 184 423 3,060

01549700 Observed 23.0 43.0 75.0 112 156 205 342 500 700 973 1,360 2,010 2,530 3,350 5,140 10,700 74,190

Predicted 26.4 60.1 94.2 122 161 201 298 420 650 908 1,320 1,980 2,480 3,310 4,970 10,060 63,840

01549780 Observed -- 0.30 0.60 1.00 1.50 1.80 2.70 3.80 5.20 7.00 10.0 15.0 19.0 24.0 38.0 87.0 --

Predicted 0.10 0.24 0.52 0.73 1.03 1.33 2.24 3.59 5.66 7.67 10.3 14.5 18.2 24.0 37.6 88.7 610

01550000 Observed 4.00 9.54 17.0 25.0 35.0 46.0 71.0 101 144 203 284 410 509 665 986 2,180 13,410

Predicted 1.67 4.97 9.88 13.8 19.3 25.1 41.8 66 118 166 235 354 452 603 915 1,940 13,260

01552000 Observed 11.3 26.0 44.6 70.0 103.0 137.0 210 300 411 555 750 1,070 1,300 1,680 2,530 5,680 42,280

Predicted 7.40 20.5 37.4 53.0 71.4 92.6 148 224 366 496 661 979 1,250 1,650 2,460 5,003 32,210

01552500 Observed 0.20 1.50 2.70 4.40 6.40 8.80 13.0 19.0 26.0 35.0 47.0 66.0 80.0 103 156 375 3,510

Predicted 0.42 1.09 2.31 3.46 4.75 6.29 10.6 16.7 28.5 37.4 48.3 67.7 83.8 107 157 332 2,150

01553130 Observed -- 1.10 1.60 2.00 2.20 2.50 3.50 4.80 6.40 8.00 9.80 13.0 15.0 18.0 25.0 56.2 --

Predicted 0.38 0.54 0.91 1.16 1.52 1.87 2.72 3.71 5.00 6.63 9.63 12.8 14.8 19.2 29.5 68.8 454

01555000 Observed 21.3 40.0 55.0 68.0 83.0 99.0 142 200 267 350 470 645 776 981 1,390 2,790 20,560

Predicted 38.3 56.0 76.5 95.8 118.5 144.4 194 242 290 378 522 717 814 1,010 1,410 2,790 17,820

01555500 Observed 1.53 7.60 15.0 23.0 32.0 41.0 63.0 90.0 121 162 220 308 382 497 760 1,710 31,140

Predicted 14.2 22.6 33.2 41.7 53.0 65.2 90.3 116 139 182 249 342 413 548 854 1,900 12,650

01556000 Observed 31.4 48.0 63.0 73.0 81.0 93.0 118 157 210 284 390 556 682 888 1,320 2,780 20,930

Predicted 18.6 35.8 48.6 59.7 74.7 89.0 120 156 196 269 393 556 650 833 1,220 2,540 15,450

01556500 Observed -- 12.0 14.0 16.0 19.0 23.0 35.0 55.0 80.5 116 164 227 272 342 473 960 --

Predicted 3.89 8.22 12.6 16.0 20.7 25.2 36.1 49.3 69.3 95.8 144 201 238 313 475 1,040 6,060

01557500 Observed 1.41 3.60 5.20 7.00 9.00 12.0 20.0 30.0 41.0 54.0 74.0 105 130 169 252 538 2,800

Predicted 1.06 2.12 3.81 4.91 6.73 8.55 13.3 19.7 28.2 39.4 60.1 84 100 134 208 478 2,990

01558000 Observed 31.4 64.0 74.0 83.0 92.0 103 130 172 225 296 393 540 648 815 1170 2,260 18,830

Predicted 12.6 23.4 33.4 41.4 52.7 63.8 88.6 117 160 221 334 473 542 689 986 2,000 11,990
52 Estimation of Baseline Daily Mean Streamflows for Ungaged Locations on Pennsylvania Streams, WY 1960–2008 Appendix 4. Flow-duration exceedance probabilities, observed and computed from streamflow data, and regression equations for streamgages used in regression analysis.—Continued [--, no data; Pn, n probability exceedance] U.S. Geological Survey streamgage number Type Flow-duration exceedance, in cubic feet per second P99.9944 P99 P95 P90 P85 P80 P70 P60 P50 P40 P30 P20 P15 P10 P05 P01 P0.0056 01559000 Observed 43.6 173 228 266 297 330 414 520 668 866 1,150 1,580 1,880 2,380 3,410 6,500 45,950 Predicted 69.6 120 154 186 230 274 363 456 588 810 1,210 1,730 1,960 2,430 3,330 6,340 38,020 01559700 Observed -- 0.10 0.20 0.28 0.35 0.40 0.70 1.20 2.00 3.10 4.80 7.30 9.9 14.0 22.5 48.0 -- Predicted 0.07 0.15 0.32 0.42 0.60 0.78 1.31 2.12 2.91 4.08 6.04 8.35 10.2 13.9 23.2 60.5 396 01560000 Observed 6.40 11.0 16.0 20.0 25.0 31.0 46.0 68.0 100 142 209 320 413 572 900 1,970 9,000 Predicted 3.90 8.33 14.5 19.0 25.9 33.2 51.8 76.3 107 150 224 318 384 513 801 1,790 10,610 01562000 Observed 39.6 68.0 98.0 118 140 163 220 304 428 599 860 1,290 1,640 2,200 3,330 7,200 49,370 Predicted 32.4 62.0 91.2 114 148 184 264 358 467 648 967 1,390 1,650 2,160 3,220 6,690 40,200 01564500 Observed 0.83 5.40 9.80 14.0 19.0 24.0 40.0 64.0 100 147 216 330 428 593 953 2,160 17,640 Predicted 4.85 10.3 17.9 23.2 31.7 40.8 63.0 91.3 121 165 240 340 415 560 893 2,050 13,370 01565000 Observed -- 19.0 26.0 31.0 38.0 44.0 64.0 90.0 125 174 239 330 398 489 660 1,230 -- Predicted 15.8 24.0 33.2 40.6 50.8 60.9 82.4 105.3 122 163 228 317 366 465 676 1,430 9,350 01565700 Observed -- 0.40 0.73 1.10 1.30 1.60 2.20 2.80 3.90 5.20 6.90 9.8 12.0 16.0 23.0 63.9 -- Predicted 0.19 0.36 0.68 0.89 1.22 1.53 2.37 3.48 4.26 5.67 7.72 10.5 11.7 14.5 21.0 48.8 381 01566000 Observed 2.20 8.60 18.0 25.0 32.0 39.0 57.0 81.4 120 167 236 350 445 600 949 2,260 22,050 Predicted 8.02 15.3 25.0 32.0 42.7 54.0 80.3 112 142 191 269 380 469 635 1015 2,320 15,490 01567500 Observed 1.21 2.40 3.10 3.60 4.10 4.50 5.80 7.60 10.0 13.0 18.0 25.0 30.0 40.0 62.0 153 2,030 Predicted 1.41 1.91 2.77 3.29 4.16 4.85 6.58 8.65 9.2 12.4 16.9 23.5 29.4 40.2 67.3 172 1,250 01568000 Observed 9.93 17.0 25.0 31.0 38.0 47.0 69.0 103 145 200 280 400 500 653 978 2,370 16,750 Predicted 16.2 26.0 36.8 45.0 56.9 68.6 93.7 121 140 188 259 366 454 615 983 2,250 15,460 01569000 Observed -- 4.40 7.40 9.30 12.0 14.0 22.0 31.0 40.0 51.0 65.0 86.0 103 125 166 317 -- Predicted 3.03 4.29 6.64 8.28 10.7 13.1 18.4 24.1 28.5 37.3 51.5 69.8 84 111 175 409 2,820 01570000 Observed -- 63.0 96.0 115 137 159 207 267 336 428 563 777 949 1,190 1,720 35,404 -- Predicted 31.4 61.3 83.6 103 129 154 207 262 290 384 509 723 846 1,070 1,550 3,260 24,340 01571500 Observed 67.4 90.0 104 117 128 138 159 186 217 259 311 387 448 535 723 1,410 12,280 Predicted 23.8 42.8 53.7 64.9 78.3 90.2 114 139 150 197 256 360 425 536 778 1,650 12,200 01572000 Observed -- 2.00 3.90 5.60 7.40 9.20 14.0 21.0 30.0 41.0 56.0 80.0 100 133 200 453 -- Predicted 2.09 3.60 6.32 8.47 11.2 14.4 21.6 29.2 36.7 46.4 61.4 81.1 96 126 195 446 3,100 01574500 Observed -- 8.20 11.0 14.0 16.0 18.0 24.0 32.0 41.0 53.0 71.0 99.0 118 150 222 520 -- Predicted 5.10 8.82 13.0 15.7 20.3 24.5 33.4 43.0 45.2 59.3 79.7 110 131 174 277 665 5,250 01576754 Observed -- 94.0 141 180 215 249 313 386 470 565 694 884 1,020 1,250 1,780 4,250 --

Predicted 62.7 131 154 188 221 254 308 355 388 497 631 879 981 1,170 1,560 2,990 22,700

01576787 Observed -- 31.0 54.0 67.0 79.0 87.0 106 127 151 177 207 243 276 330 469 1,330 --

Predicted 23.6 34.7 43.8 52.3 63.2 73.4 92.4 110 114 147 191 264 294 354 480 967 7,720
Appendix 4 53

Appendix 4. Flow-duration exceedance probabilities, observed and computed from streamflow data, and regression equations for streamgages used in regression analysis.—Continued[--, no data; Pn, n probability exceedance]

U.S. Geological 

Survey 

streamgage 

number

Type

Flow-duration exceedance, in cubic feet per second

P99.9944 P99 P95 P90 P85 P80 P70 P60 P50 P40 P30 P20 P15 P10 P05 P01 P0.0056

01577500 Observed -- 28.0 38.6 47.0 56.0 69.0 86.0 105 122 140 160 193 219 267 354 846 --

Predicted 15.1 22.6 31.4 38.5 47.9 57.2 76.2 95.2 96.2 123 154 214 271 369 605 1,450 11,240

01578400 Observed -- 1.60 2.10 2.60 3.00 3.40 4.00 4.80 5.40 6.20 7.30 8.88 10.0 13.0 19.0 66.2 --

Predicted 0.43 0.63 1.03 1.27 1.65 1.98 2.79 3.75 4.03 5.24 6.71 9.20 10.9 14.1 22.0 54.0 483

01603500 Observed 1.00 2.00 2.70 3.40 4.00 4.80 7.00 11.0 15.0 22.0 31.0 45.0 56.0 73.0 110 259 1,980

Predicted 1.09 1.84 3.02 3.74 4.98 6.08 9.07 13.1 15.8 22.2 32.4 45.8 54.5 71.3 111 260 1,700

01609000 Observed -- 4.60 6.80 11.2 15.0 21.0 38.0 63.0 101 142 207 323 422 625 993 2,480 --

Predicted 2.78 5.85 10.5 13.5 18.7 24.1 38.2 57.2 71.5 100 145 206 258 359 604 1,490 9,540

01610155 Observed -- 0.02 0.40 1.50 2.70 4.80 11.0 22.0 36.0 57.0 88.5 141 191 269 450 1,080 --

Predicted 0.79 2.08 4.53 6.12 9.09 12.5 21.7 35.1 49.5 68.9 104 145 178 248 417 1,040 6,880

01612500 Observed -- 0.00 0.00 0.10 0.20 0.40 1.00 2.00 3.80 6.90 12.0 19.0 26.0 37.0 66.0 170 --

Predicted 0.11 0.30 0.70 0.94 1.41 1.90 3.36 5.57 7.41 10.27 14.8 20.6 25.8 36.3 64.0 174 1,270

01613050 Observed -- 0.00 0.11 0.30 0.55 0.88 1.80 3.30 5.00 7.50 12.0 18.0 24.0 33.0 53.0 121 --

Predicted 0.22 0.41 0.79 1.01 1.43 1.83 2.93 4.46 5.69 7.87 11.6 16.0 19.6 27.0 45.8 120 834

01614090 Observed -- 0.40 0.70 0.99 1.20 1.50 2.20 3.20 4.50 6.10 8.20 11.0 13.0 16.0 22.0 42 --

Predicted 0.40 0.55 0.92 1.18 1.53 1.88 2.75 3.79 4.26 5.58 7.48 9.9 12.0 16.0 26.0 66 445

01614500 Observed 25.3 56.0 84.0 103 120 140 187 252 338 450 602 843 1,030 1,320 1,930 4,220 24,260

Predicted 36.3 67.2 90.7 112 140 169 228 291 330 442 606 852 1,060 1,440 2,310 5,220 32,580

01639000 Observed 0.01 1.80 4.90 7.90 11.0 16.0 27.0 43.0 65.0 95.0 141 223 297 450 867 2,590 16,320

Predicted 4.85 11.3 19.5 26.7 35.3 45.0 69.1 100 118 154 190 268 350 477 784 1,870 12,950

03007800 Observed -- 18.0 32.0 48.0 66.0 86.0 130 185 250 334 450 643 801 1,030 1,590 3,360 --

Predicted 7.77 16.4 26.8 36.1 47.2 59.2 90.4 132 205 286 416 603 746 976 1,440 2,950 16,050

03009680 Observed -- 8.6 25.0 35.0 48.0 62.0 97.0 135 180 236 315 437 539 698 1,010 2,100 --

Predicted 5.56 11.4 19.7 27.8 36.4 46.7 73.3 108 171 233 332 466 565 724 1,040 2,090 10,430

03010500 Observed 16.5 37.0 59.0 87.0 122.0 164.0 263 380 535 728 1,020 1,440 1,760 2,290 3,330 5,810 53,800

Predicted 20.3 42.8 68.2 93.5 120.6 152.7 232 332 541 751 1,100 1,590 1,930 2,490 3,540 6,780 33,740

03010655 Observed -- 6.20 10.0 15.0 20.0 27.0 44.0 65.0 88.0 119 163 228 276 361 523 1,200 --

Predicted 2.51 5.18 8.98 11.9 15.9 20.1 31.3 46.5 71.6 101 149 215 265 352 536 1,160 6,780

03011800 Observed -- 5.10 8.40 12.0 15.0 19.0 28.0 39.0 51.0 65.2 85.0 113 136 171 240 458 --

Predicted 1.22 2.40 4.40 6.18 8.22 10.6 16.9 25.6 41.8 57.7 84.8 117 140 178 258 535 2,640

03013000 Observed 22.0 34.0 44.0 55.0 70.0 87.0 134 203 291 400 549 850 1,080 1,400 1,900 3,160 8,100

Predicted 6.93 16.5 29.0 42.2 55.3 71.4 116 178 282 389 535 766 963 1,240 1,810 3,640 16,980

03015280 Observed -- 1.10 1.70 2.30 3.00 3.70 5.70 8.30 12.0 16.0 23.0 32.0 40.0 52.0 78.0 181 --

Predicted 0.44 0.86 1.52 2.17 2.79 3.41 5.43 8.49 12.2 16.9 22.0 31.1 40.1 51.9 78.5 176 868
54 Estimation of Baseline Daily Mean Streamflows for Ungaged Locations on Pennsylvania Streams, WY 1960–2008 Appendix 4. Flow-duration exceedance probabilities, observed and computed from streamflow data, and regression equations for streamgages used in regression analysis.—Continued [--, no data; Pn, n probability exceedance] U.S. Geological Survey streamgage number Type Flow-duration exceedance, in cubic feet per second P99.9944 P99 P95 P90 P85 P80 P70 P60 P50 P40 P30 P20 P15 P10 P05 P01 P0.0056 03015500 Observed 21.2 36.0 52.0 68.0 86.0 107.0 160 227 310 420 589 852 1,080 1,440 2,170 4,200 13,650 Predicted 19.1 36.9 55.5 79.3 97.5 120.4 181 260 364 493 643 910 1,160 1,480 2,120 4,200 18,160 03017500 Observed -- 20.0 30.0 42.0 57.0 74.0 117 168 240 330 464 652 794 1,000 1,410 2,720 -- Predicted 10.1 19.0 30.9 42.4 54.9 69.7 107 155 237 327 483 677 811 1,040 1,500 2,990 13,840 03020500 Observed 23.0 34.0 47.0 63.0 81.0 102.0 155 220 300 397 536 750 924 1,220 1,880 3,930 15,420 Predicted 19.7 35.3 50.5 69.4 84.7 102.2 149 213 289 400 539 772 987 1,270 1,860 3,770 16,300 03021350 Observed -- 5.40 11.0 17.0 23.0 31.0 52.0 78.0 104 140 192 292 375 530 875 1,940 -- Predicted 2.03 4.92 9.2 14.0 18.3 23.6 39.8 64.4 97.8 134 171 242 313 401 591 1,230 5,270 03021500 Observed 4.38 11.0 18.0 26.0 35.0 46.0 77.0 125 188 270 390 585 752 1,020 1,580 3,300 13,830 Predicted 5.64 13.3 23.1 34.8 44.6 56.9 93.0 146 218 300 387 550 713 915 1,340 2,710 11,280 03022540 Observed -- 2.80 4.40 6.60 8.40 11.0 17.0 22.0 30.0 38.0 51.0 73.0 92.0 121 190 421 -- Predicted 1.01 2.07 3.53 5.11 6.48 7.90 12.6 20.0 27.3 38.1 48.3 69.1 91.8 120 183 408 1,830 03024000 Observed -- 73.0 104 141 185 233 387 600 898 1,270 1,840 2,690 3,360 4,360 6,180 11,000 -- Predicted 45.7 103 151 219 266 327 493 724 1,020 1,410 1,810 2,630 3,470 4,470 6,460 12,560 50,750 03025000 Observed -- 18.0 25.0 32.0 40.0 50.0 72.0 103 142 197 273 384 470 617 933 1,970 -- Predicted 11.4 19.1 27.3 36.8 45.0 53.8 78.2 111 144 201 272 388 497 648 973 2,060 9,110 03026500 Observed 0.07 0.27 0.64 1.10 1.60 2.20 3.90 5.90 8.20 11.0 15.0 21.0 25.0 32.0 48.0 104 456 Predicted 0.20 0.39 0.78 1.09 1.49 1.92 3.17 4.97 8.12 11.2 16.4 22.5 26.7 34.3 50.9 112 590 03028000 Observed 4.51 7.20 11.0 15.0 20.0 26.0 39.0 56.0 76.0 100 133 185 224 290 418 816 2,860 Predicted 1.99 4.00 7.23 10.2 13.5 17.4 27.9 42.1 68.3 94 136 189 227 290 419 856 4,180 03029400 Observed -- 0.70 1.10 1.40 1.80 2.40 4.00 6.00 9.00 14.0 21.0 29.0 36.0 47.0 70.0 140 -- Predicted 0.21 0.48 1.00 1.48 2.02 2.63 4.55 7.51 11.42 15.7 21.2 29.5 37.0 48.3 74.1 170 858 03031950 Observed -- 0.50 0.90 1.30 1.60 2.10 3.40 4.90 6.90 9.40 13.0 18.0 22.0 29.0 47.0 109 -- Predicted 0.09 0.23 0.51 0.77 1.06 1.40 2.49 4.23 6.33 8.65 11.3 15.6 20.0 26.2 41.3 99 524 03032500 Observed 20.7 40.0 62.0 85.0 112.0 143.0 229 335 470 660 920 1,330 1,630 2,130 3,090 5,990 27,030 Predicted 9.36 25.1 45.2 66.4 88.4 116.3 192 299 476 659 921 1,320 1,650 2,140 3,160 6,350 28,830 03038000 Observed -- 6.00 10.0 14.0 19.0 26.0 46.0 75.0 115 172 254 390 503 691 1,060 2,330 -- Predicted 2.01 5.52 11.9 17.8 25.5 35.7 63.8 104 159 216 311 422 508 671 1,040 2,280 11,070 03039200 Observed -- 0.10 0.20 0.38 0.55 0.79 1.40 2.40 3.30 4.40 6.00 8.50 11.0 14.0 23.0 52 -- Predicted 0.13 0.20 0.38 0.50 0.68 0.85 1.34 2.04 2.97 4.16 6.38 8.68 10.2 13.4 20.9 50 280 03039925 Observed -- 0.32 0.58 1.00 1.40 1.80 2.50 3.70 4.90 6.30 8.40 11.0 13.0 17.0 24.0 44 --

Predicted 0.14 0.22 0.42 0.56 0.76 0.96 1.54 2.34 3.39 4.66 7.05 9.36 10.8 14.0 21.4 50 257

03042200 Observed -- 0.30 0.60 0.90 1.30 1.80 3.10 4.60 6.50 9.00 12.0 18.0 23.0 30.0 46.0 104 --

Predicted 0.32 0.51 0.94 1.28 1.72 2.18 3.47 5.19 7.23 9.83 14.4 19.1 22.4 29.1 44.5 103 532
Appendix 4 55

Appendix 4. Flow-duration exceedance probabilities, observed and computed from streamflow data, and regression equations for streamgages used in regression analysis.—Continued[--, no data; Pn, n probability exceedance]

U.S. Geological 

Survey 

streamgage 

number

Type

Flow-duration exceedance, in cubic feet per second

P99.9944 P99 P95 P90 P85 P80 P70 P60 P50 P40 P30 P20 P15 P10 P05 P01 P0.0056

03049000 Observed 1.30 4.70 8.30 12.0 17.0 23.0 41.0 65.0 95.0 135 190 273 343 456 698 1,450 7,530

Predicted 1.53 3.90 7.94 11.3 16.0 21.6 37.5 61.0 87.1 121 176 245 304 410 659 1,530 7,760

03049800 Observed -- 0.04 0.20 0.35 0.53 0.71 1.20 1.80 2.70 4.00 5.90 8.60 11.0 15.0 24.0 55.0 --

Predicted 0.03 0.11 0.24 0.34 0.49 0.63 1.12 1.95 2.79 3.98 5.61 7.88 10.2 14.1 24.2 65.4 377

03062500 Observed -- 1.40 3.20 5.00 7.00 9.90 19.0 34.0 52.0 74.0 104 151 190 255 391 825 --

Predicted 1.02 2.68 5.46 8.17 11.3 15.3 26.3 41.9 58.8 78.8 110 144 174 227 355 810 3,620

03072590 Observed -- 0.13 0.37 0.67 1.10 1.80 3.70 5.60 8.3 12.0 17.0 27.0 34.0 45.0 70.0 159 --

Predicted 0.32 0.80 1.49 2.09 2.80 3.55 5.70 8.82 11.6 15.9 22.0 29.7 36.9 49.5 80.8 200 1,020

03072840 Observed -- 3.50 7.17 9.8 14.0 19.0 31.0 51.0 74.0 105 150 213 265 350 556 1,330 --

Predicted 2.87 6.09 10.3 13.9 18.4 23.0 36.5 56.6 71.1 101 140 202 265 362 594 1,420 7,250

03073000 Observed 0.10 0.59 1.60 3.20 6.00 9.80 20.0 38.0 66.0 105 163 260 346 490 819 2,040 8,710

Predicted 4.08 8.88 14.8 20.0 26.3 32.9 51.8 79.7 100 141 194 279 365 498 813 1,920 9,620

03074300 Observed -- 0.11 0.25 0.42 0.60 0.85 1.50 2.20 3.30 4.70 6.90 10.0 13.0 16.0 25.0 55.0 --

Predicted 0.16 0.25 0.47 0.63 0.85 1.08 1.72 2.60 3.48 4.77 7.16 9.3 10.8 14.1 22.1 53.3 261

03078000 Observed 0.04 1.90 4.80 8.2 12.0 16.0 30.0 46.0 68.0 93.0 127 176 219 282 420 854 3,400

Predicted 0.55 1.50 3.34 4.9 7.1 9.77 17.6 29.7 50.5 70.5 105 146 177 232 354 775 3,940

03079000 Observed 11.0 20.0 37.0 57.0 77.0 101.0 162 242 343 482 677 958 1,180 1,540 2,330 4,930 22,900

Predicted 9.03 20.5 35.4 49.1 65.5 85.0 136 203 313 437 648 918 1,120 1,470 2,190 4,500 21,630

03080000 Observed 2.35 6.30 12.0 20.0 30.0 40.0 69.0 102 148 200 278 393 485 639 938 1,840 6,400

Predicted 5.11 9.32 16.0 22.3 29.2 37.8 59.5 87.2 128 175 256 348 411 528 774 1,600 7,210

03082200 Observed -- 0.10 0.30 0.75 1.25 1.90 3.70 6.10 9.00 13.0 18.0 26.0 33.0 45.0 70.0 158 --

Predicted 0.29 0.52 0.97 1.34 1.81 2.31 3.74 5.76 8.02 11.0 16.1 21.6 25.9 33.9 52.9 124 626

03084000 Observed -- 0.00 0.20 0.39 0.57 0.76 1.20 1.80 2.50 3.50 5.00 7.30 9.20 13.0 20.0 44 --

Predicted 0.02 0.17 0.29 0.40 0.53 0.61 0.89 1.34 2.12 3.02 4.32 6.01 7.64 10.6 18.3 50 298

03085956 Observed -- 2.52 3.50 4.80 5.80 7.00 9.50 13.0 17.0 23.0 30.1 42.4 52.0 70.0 113 307 --

Predicted 0.17 0.98 1.61 2.14 2.81 3.28 4.82 7.28 11.0 16.0 23.4 33.5 43.3 60.3 103 267 1,490

03092000 Observed 0.00 0.04 0.10 0.24 0.40 0.60 1.20 2.10 3.90 6.60 11.0 20.0 30.0 50.0 105 353 1,780

Predicted 0.07 0.25 0.58 0.89 1.28 1.65 3.16 6.17 9.38 13.9 17.7 27.0 38.9 53.9 91 234 1,180

03093000 Observed 1.02 7.00 11.0 14.0 16.0 19.0 25.0 34.0 46.0 64.0 90.0 137 182 265 471 1,130 5,060

Predicted 0.43 1.57 3.36 5.13 7.18 9.37 17.3 32.0 48.9 71.4 93.2 140 196 268 438 1,050 4,870

03102500 Observed 2.91 5.80 9.40 13.0 16.0 21.0 32.0 48.0 69.0 96.0 133 196 246 336 551 1,210 5,550

Predicted 3.07 6.66 10.3 14.3 17.9 21.3 32.7 50.7 64.7 92.5 118 176 242 325 515 1,180 5,530

03102950 Observed -- 0.84 3.00 5.50 8.20 12.0 23.0 37.0 55.0 83.0 124 199 260 352 517 882 --

Predicted 0.91 2.67 5.10 7.57 10.1 12.8 22.1 38.4 54.8 79.1 101 151 211 285 459 1,070 5,030
56 Estimation of Baseline Daily Mean Streamflows for Ungaged Locations on Pennsylvania Streams, WY 1960–2008 Appendix 4. Flow-duration exceedance probabilities, observed and computed from streamflow data, and regression equations for streamgages used in regression analysis.—Continued [--, no data; Pn, n probability exceedance] U.S. Geological Survey streamgage number Type Flow-duration exceedance, in cubic feet per second P99.9944 P99 P95 P90 P85 P80 P70 P60 P50 P40 P30 P20 P15 P10 P05 P01 P0.0056 03103000 Observed -- 2.10 4.70 6.90 9.30 12.0 21.0 38.0 64.0 106 181 315 412 546 813 1,690 -- Predicted 3.17 7.71 12.8 18.0 23.1 28.3 45.3 72.8 96.1 138 179 267 369 500 801 1,840 8,650 03106000 Observed 6.54 13.0 22.0 33.0 44.0 58.0 94.0 146 216 310 448 659 831 1,100 1,700 3,830 21,170 Predicted 5.13 14.8 25.0 34.6 46.0 58.1 92.8 144 200 285 402 583 757 1,028 1,650 3,750 17,990 03106500 Observed 20.2 34.0 47.0 58.0 68.0 81.0 115 167 248 355 523 818 1,040 1,390 1,990 4,120 16,470 Predicted 16.4 33.2 47.8 64.1 79.8 96.0 142 207 256 362 487 709 938 1,260 1,980 4,360 20,015 03109500 Observed 12.0 25.0 39.0 53.0 68.0 85.0 125 182 258 361 503 730 920 1,240 1,890 4,160 17,910 Predicted 12.6 28.0 41.5 54.0 69.2 83.7 126 188 231 335 472 700 935 1,290 2,110 4,900 23,800 03110000 Observed 0.80 3.00 6.90 11.0 16.0 21.0 34.0 52.2 80.0 113 161 235 294 390 595 1,290 7,350 Predicted 1.38 3.37 6.71 9.25 13.2 17.5 30.5 50.9 70.8 103 156 222 280 385 636 1,530 7,360 03111150 Observed -- 0.00 0.00 0.20 0.40 0.61 1.40 2.40 3.90 6.00 9.00 13.0 17.0 22.0 35.0 87.0 -- Predicted 0.16 0.32 0.62 0.83 1.14 1.43 2.39 3.96 4.95 7.13 9.98 14.2 18.5 25.6 43.6 115 617 03111500 Observed 2.87 12.0 18.0 23.0 28.0 33.0 45.0 60.0 80.0 106 138 186 219 270 385 852 3,750 Predicted 2.34 5.13 8.72 11.8 15.7 19.5 31.3 49.5 62.4 90 126 182 240 328 542 1,300 6,220 04213000 Observed 0.30 3.10 6.80 11.0 15.0 21.0 39.0 66.0 100 150 221 353 480 700 1190 2,610 10,680 Predicted 1.49 5.02 9.77 15.4 20.4 26.1 46.2 81.5 130 185 230 345 483 636 969 2,080 8,820 04213075 Observed -- 0.36 0.73 1.00 1.20 1.40 2.00 2.60 3.50 4.60 6.10 8.60 11.0 14.0 23.0 58.6 -- Predicted 0.01 0.06 0.15 0.25 0.35 0.46 0.91 1.82 3.14 4.48 5.33 7.87 11.1 14.8 23.6 58.1 282
Prepared by the West Trenton Publishing Service Center

For additional information write to:

Director, Pennsylvania Water Science Center

U.S. Geological Survey

215 Limekiln Road

New Cumberland, PA 17070-2424

http://pa.water.usgs.gov/
Stuckey and others—Estimation of Baseline Daily Mean Streamflows for Ungaged Locations on Pennsylvania Streams, Water Years 1960–2008—Scientific Investigations Report 2012–5142