U.S. Department of the Interior

U.S. Geological Survey

Scientific Investigations Report 2015–5157

National Water Census

Estimation of Daily Mean Streamflow for Ungaged 

Stream Locations in the Delaware River Basin, 

Water Years 1960–2010

0

1959 1963 1967 1971 1975 1979 1983 1987 1991 1995 1999 2003 2007

1,000

500

1,500

2,000

2,500

3,000

3,500

Estimated mean daily streamflow,

in cubic feet per second

Altered streamflow

Baseline streamflow

Altered streamflow

10,000

1,000

100

10

Exceedance probability

1

0

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

Estimated mean daily streamflow,

in cubic feet per second

Baseline streamflow
Cover. Little Neshaminy Creek near Neshaminy, Pennsylvania, looking upstream. Photograph courtesy of U.S. Geological 

Survey Pennsylvania Water Science Center Hydrologic Surveillance Program staff, Exton office. 

(Top graph) Flow-duration curve, in cubic feet per second, for ungaged site under baseline and altered flow conditions. 

(Bottom graph) Baseline and altered hydrograph, in cubic feet per second, for ungaged site.
Estimation of Daily Mean Streamflow 

for Ungaged Stream Locations in the 

Delaware River Basin, Water Years 

1960–2010

By Marla H. Stuckey

Scientific Investigations Report 2015–5157

U.S. Department of the Interior

U.S. Geological Survey

National Water Census
U.S. Department of the Interior

SALLY JEWELL, Secretary

U.S. Geological Survey

Suzette M. Kimball, Director

U.S. Geological Survey, Reston, Virginia: 2016

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Suggested citation:

Stuckey, M.H., 2016, Estimation of daily mean streamflow for ungaged stream locations in the Delaware River Basin, 

water years 1960–2010: U.S. Geological Survey Scientific Investigations Report 2015–5157, 42 p., 

http://dx.doi.org/10.3133/sir20155157.

ISSN 2328-0328 (online)
iii

Contents

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

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

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

Study Area..............................................................................................................................................2

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

Estimation of Baseline Daily Mean Streamflow .......................................................................................4

Reference Streamgages in the Delaware River Basin...................................................................6

Reference Streamgage Criteria ................................................................................................6

Record Extension.........................................................................................................................6

Regression Equations for Estimating Streamflow at Flow-Duration 

Exceedance Probabilities ....................................................................................................10

Flow-Duration Exceedance Probabilities and Basin Characteristics 

for Reference Streamgages .......................................................................................11

Regression Analysis and Resulting Flow-Duration Exceedance 

Probability Regression Equations..............................................................................11

Selection of Reference Streamgages for Estimating Daily Mean Streamflow........................16

Closest Streamgage ..................................................................................................................16

Map Correlation .........................................................................................................................16

Estimation of Altered Daily Mean Streamflow........................................................................................19

Use of DRB-SET for Estimating Baseline and Altered Daily Mean Streamflow at 

Ungaged Stream Locations ..........................................................................................................19

Accuracy and Limitations of Estimated Streamflow..............................................................................19

Summary........................................................................................................................................................26

Acknowledgments.......................................................................................................................................26

References Cited..........................................................................................................................................26

Appendix 1. Reference streamgages with record extension techniques applied ........................30

Appendix 2. Basin characteristics used in the development of flow-duration 

exceedance probability regression equations for the Delaware River Basin.....................34

Appendix 3. Observed and predicted flow-duration exceedance probability 

discharges for streamgages used in regression analysis ......................................................37
iv

Figures

1. Map showing physiographic provinces of the Delaware River Basin.........................................3

2. Graphical representation of the QPPQ methodology, 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 stream location, and D, estimated 

daily mean streamflow at the ungaged stream location................................................................4

3. Map showing location of U.S. Geological Survey reference streamgages 

in or near the Delaware River Basin .................................................................................................5

4. Histogram showing percent impervious area in the reference streamgage 

subbasins within the Delaware River Basin ..................................................................................10

5. Histogram showing the number of reference streamgages requiring 

record extension and the number of years of record extension, 

Delaware River Basin ........................................................................................................................10

6. Example streamflow correlation map for U.S. Geological Survey 

streamgage 01559000, Juniata River at Huntingdon, Pa. .............................................................17

7. Box plot and map showing the distribution of root mean square error 

between the observed and estimated streamflow correlations, 

resulting from map correlation, for 109 streamgages in and near the 

Delaware River Basin ........................................................................................................................18

8. Screen capture of an example report generated by the Delaware River 

Basin Streamflow Estimator Tool showing water use, a flow-duration 

curve, and a hydrograph ...................................................................................................................20

9. Graph showing Nash-Sutcliffe efficiency values determined using the 

closest streamgage and map correlation in the Delaware River Basin 

Streamflow Estimator Tool ................................................................................................................22

10. Graph showing distribution of Nash-Sutcliffe efficiency values between 

observed and estimated daily mean streamflows in the Upper and Lower 

Delaware River Basin ........................................................................................................................23

11. Map showing spatial distribution of Nash-Sutcliffe efficiency values 

for reference streamgage basins in the Delaware River Basin .................................................24

12. Hydrographs and flow-duration curves showing estimated and observed daily 

mean streamflows for U.S. Geological Survey streamgages A, 01420500, 

Beaver Kill at Cooks Falls, New York, water years 1999–2002, and B, 01464500, 

Crosswicks Creek at Extonville, New Jersey, water years 1999–2002 ......................................25

Tables

1. U.S. Geological Survey reference streamgages in and near the Delaware 

River Basin.............................................................................................................................................7

2. Basin characteristics used in the development of regression equations 

for flow-duration exceedance probabilities for streams in the Delaware 

River Basin...........................................................................................................................................12

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

regression equations for streams in the Delaware River Basin.................................................15

4. Range of basin characteristics used in the development of regression 

equations to estimate flow-duration exceedance probability discharges 

for ungaged stream locations within the Delaware River Basin................................................21

5. Nash-Sutcliffe efficiency values between observed and estimated 

daily mean streamflows in the Delaware River Basin..................................................................23
v

Conversion Factors and Datums

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) 

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 hectometers (hm3

) 

inch per hour (in/h) 0.0254 meter per hour (m/h)

inch per year (in/yr) 25.4 millimeter per year (mm/yr)

Hydraulic conductivity

foot per day (ft/d) 0.3048 meter per day (m/d)

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).

Estimation of Daily Mean Streamflow for Ungaged 

Stream Locations in the Delaware River Basin, 

Water Years 1960–2010

By Marla H. Stuckey

Abstract

The ability to characterize baseline streamflow 

conditions, compare them with current 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. The U.S. Geological Survey, through 

the National Water Census, has developed the Delaware River 

Basin Streamflow Estimator Tool (DRB-SET) to estimate 

baseline (minimally altered) and altered (affected by regulation, diversion, mining, or other anthropogenic activities) and 

altered streamflow at a daily time step for ungaged stream 

locations in the Delaware River Basin for water years 1960–

2010. Daily mean baseline streamflow is estimated by using 

the QPPQ method to equate streamflow expressed as a percentile from the flow-duration curve (FDC) for a particular day at 

an ungaged stream location with the percentile from a FDC for 

the same day at a hydrologically similar gaged location where 

streamflow is measured. Parameter-based regression equations 

were developed for 22 exceedance probabilities from the 

FDC for ungaged stream locations in the Delaware River 

Basin. Water use data from 2010 is used to adjust the baseline 

daily mean streamflow generated from the QPPQ method 

at ungaged stream locations in the Delaware River Basin to 

reflect current, or altered, conditions. To evaluate the effectiveness of the overall QPPQ method contained within DRB-SET, 

a comparison of observed and estimated daily mean streamflows was performed for 109 reference streamgages in and 

near the Delaware River Basin. The Nash-Sutcliffe efficiency 

(NSE) values were computed as a measure of goodness of fit. 

The NSE values (using log10 streamflow values) ranged from 

0.22 to 0.98 (median of 0.90) for 45 streamgages in the Upper 

Delaware River Basin and from -0.37 to 0.98 (median of 0.79) 

for 41 streamgages in the Lower Delaware River Basin.

Introduction

The National Water Census is a U.S. Geological Survey 

(USGS) research program, funded through WaterSMART, for 

national water availability and use that develops new water 

accounting tools and assesses water availability at regional 

and national scales. WaterSMART, which stands for Water 

Sustain and Manage America’s Resources for Tomorrow, is 

an initiative launched by the U.S. Department of the Interior 

in February 2010. Through the National Water Census, the 

USGS is integrating diverse research on water availability 

and use and enhancing the understanding of the connection 

between water quality and water availability (Alley and others, 

2013). The research is designed to build the decision support 

capacity for water-management agencies and other naturalresource managers. The National Water Census identified 

three geographic Focus Areas that would benefit from cutting 

edge approaches to assessing water availability while also 

serving as pilot studies where multiple lines of research could 

be integrated and designed to meet stakeholders’ information 

needs. Each Focus Area offers unique challenges that the 

USGS could investigate at the scale of a large river basin. 

The Delaware River Basin was selected as one of these Focus 

Areas.

The Delaware River Basin covers more than 13,500 

square miles (mi2

) in parts of four states, including New York, 

New Jersey, Pennsylvania, and Delaware. The population 

in the basin is approximately 8.3 million people. The basin 

has the largest inter-basin withdrawals of water east of the 

Mississippi River and provides drinking water to more than 

15 million people (Delaware River Basin Commission, 2013). 

After a history of litigation, many of the water-management 

decisions regarding the Delaware River system are now coordinated through an interstate river basin commission known 

as the Delaware River Basin Commission (DRBC). In the 

upper parts of the basin, concerns over the effects of proposed 

unconventional shale gas development and the freshwater 
2 Estimation of Daily Mean Streamflow for Ungaged Stream Locations in the Delaware River Basin, Water Years 1960–2010

requirements for a recently discovered endangered mussel 

species (Lellis, 2001) have added new complexities to water 

management. One of the needs identified by stakeholders 

in the basin was the need for a scientific approach to define 

relations between streamflow processes and the responses of 

aquatic organisms in tributary streams.

Hydrologic and ecological data can be directly related to 

provide the basis for understanding the flow needs of aquatic 

species found in the tributaries in the Delaware River Basin. 

Because the aquatic species living in tributaries are often 

susceptible to minor changes in streamflow, proactive management measures incorporating the principles of ecological flow 

science can be implemented to promote the long-term ecological sustainability of these waters. Providing the data and tools 

to understand and define flow-alteration ecological-response 

relations will assist water-resource managers and policy makers in making water use decisions that meet the ecological 

flow needs of aquatic species in the Delaware River Basin. 

Maintenance of 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, and assess the effects of human activities 

on streamflow is fundamental to water-management programs 

addressing water allocation, human-health issues, recreation 

needs, and the establishment of ecological flow criteria. Waterresource managers undertaking an in-depth evaluation of flow 

regimes to promote instream ecological health often require 

daily mean streamflow information to determine streamflow 

statistics that fulfill their individual needs. Typically, this 

information is obtainable only from a time series hydrograph. 

The USGS, through the National Water Census, has developed 

a tool to estimate streamflow at a daily time step for ungaged 

stream locations in the Delaware River Basin. The hydrologic 

information provided by this tool can be used to provide a 

foundation for ecological flow science in the basin.

Previous Studies

Fennessey (1994) introduced a method, termed the 

“QPPQ method,” to estimate streamflow statistics for an 

ungaged stream location. This method was used by Hughes 

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

(2000), Mohamoud (2008), Archfield and others (2010), Shu 

and Ourda (2012), Stuckey and others (2014), and Gazoorian 

(2015). Archfield and Vogel (2010) developed a method for 

selecting an appropriate streamgage for an ungaged stream 

location on the basis of streamflow correlation (termed the 

“map correlation method”). These two methods have been 

successfully applied in Massachusetts (Archfield and others, 

2010), the Connecticut River Basin (Archfield and others, 

2012), Pennsylvania (Stuckey and others, 2014), and New 

York (Gazoorian, 2015) to generate daily mean streamflows 

for ungaged stream locations. Regression equations for 

estimating streamflow at 17 flow-duration exceedance 

probabilities from the flow-duration curve were developed for 

Pennsylvania in conjunction with the Baseline Streamflow 

Estimator Tool (Stuckey and others, 2014). Water use, including reported and estimated withdrawals and returns, for the 

Delaware River Basin is documented in Hutson and others, 

in press.

Study Area

The Delaware River Basin encompasses 13,539 mi2, 

draining parts of Pennsylvania (6,422 mi2, or 50.3 percent of 

the basin’s total land area), New Jersey (2,969 mi2, or 

23.3 percent), New York (2,362 mi2, or 18.5 percent), and 

Delaware (1,004 mi2, or 7.9 percent). Some subbasins within 

the Delaware River Basin drain directly into Delaware Bay 

(782 mi2). A total of 216 tributary streams enter the Delaware 

River, making a total of approximately 23,700 linear stream 

miles in the river system (http://www.state.nj.us/drbc/basin/). 

The largest tributaries are the Schuylkill River and the Lehigh 

River in Pennsylvania, which together drain 3,281 mi2.

Five major physiographic provinces compose the 

Delaware River Basin (fig. 1) (Fischer and others, 2004). 

The northern third of the basin is covered by the Appalachian 

Plateaus Physiographic Province, which is composed of gently 

folded sandstones, shales, and conglomerates. The Valley and 

Ridge Physiographic Province is adjacent and south of the 

Appalachian Plateau Physiographic Province and consists primarily of sandstones and shales that form ridges and valleys. 

Glaciation during the Pleistocene Epoch covered the upper 

half of the basin, extending to the New England Physiographic 

Province, which is an upland ridge of metamorphosed shales 

and carbonate rocks. The Piedmont Physiographic Province 

is the most highly socioeconomically developed province in 

the basin and is separated geographically into two sections—

the Uplands Section which is composed of metamorphic and 

igneous rocks, and the Lowlands Section, which is primarily 

composed of clastic rocks. The most southern physiographic 

province is the Coastal Plain, which is composed of unconsolidated sediment. 

The climate in the Delaware River Basin varies 

depending on the topography and latitude. Average annual 

temperature ranges from about 45 degrees Fahrenheit (°F) in 

the northern part of the basin to 56 °F in the southern part. 

Average annual precipitation ranges from about 50 inches (in.) 

in the north to 42 in. in the south (Jenner and Lins, 1991).

Purpose and Scope

This report presents the data and methodology used to 

estimate daily mean streamflow for water years1 1960–2010 

for ungaged locations on streams in the Delaware River Basin. 

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.
Introduction 3

Delaware 

Bay Chesapeake Bay

Atlantic Ocean

Lower 

Delaware 

River 

Basin

Upper Delaware 

River Basin

Delaware River

Base modified from U.S. Geological Survey 1:100,000-scale 

and 1:250,000-scale digital data

77° 76° 75° 74° 73°

43°

42°

41°

40°

39°

EXPLANATION

Major rivers and streams

State boundary

Delaware River Basin boundary

Physiographic Province

0 9 18 27 36 MILES

0 25 50 KILOMETERS

APPALACHIAN PLATEAUS

COASTAL PLAIN

NEW ENGLAND

PIEDMONT

VALLEY AND RIDGE

NEW YORK

PENNSYLVANIA

MARYLAND

DELAWARE

NEW JERSEY

DISTRICT OF

COLUMBIA

VIRGINIA

MASSACHUSETTS

VERMONT

CONNECTICUT

Figure 1. Physiographic provinces of the Delaware River Basin.
4 Estimation of Daily Mean Streamflow for Ungaged Stream Locations in the Delaware River Basin, Water Years 1960–2010

Parameter-based regression equations used to predict streamflows at 22 exceedance probabilities from the flow-duration 

curve (FDC) for ungaged stream locations in the Delaware 

River Basin are presented. Flow-duration exceedance probabilities for 109 streamgages are presented. Streamflow data 

from continuous-record streamgages were used to develop 

correlation maps of the predicted correlation of streamflow between an ungaged stream location and a reference 

streamgage. A brief description of the Delaware River Basin 

Streamflow Estimator Tool (DRB-SET), a tool for estimating baseline and altered daily mean streamflow for ungaged 

stream locations in the Delaware River Basin, is presented.

Estimation of Baseline Daily Mean 

Streamflow

Daily mean streamflow can be estimated using the 

QPPQ method (Fennessey, 1994), which equates streamflow 

expressed as a percentile from the FDC for a particular day 

at an ungaged stream location with that from the FDC for 

the same day at a hydrologically similar gaged location 

where streamflow is measured (referred to as a “reference 

streamgage”). Streamflow corresponding to the flow-duration 

exceedance probability for the ungaged stream location are 

selected from a daily FDC constructed from points determined 

by regression equations. Geospatial correlation of streamflow, 

termed map correlation, (Archfield and others, 2010) is used to 

select a reference streamgage for the ungaged stream location. 

A graphical depiction of the QPPQ methodology is shown in 

figure 2.

For this study, observed streamflow and basin characteristics from 109 reference streamgages (fig. 3) with unaltered 

streamflow were used to develop regression equations to predict streamflow corresponding to 22 exceedance probabilities 

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

specified streamflows are equaled or exceeded (Searcy, 1960). 

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 term “exceedance 

probability” refers to the percentage of time that each streamflow value in the record is equaled or exceeded and is used 

when discussing statistics; the term “percentile” refers to an 

Reference gage streamflow

Reference gage streamflow

Ungaged streamflow

Ungaged streamflow

Date

Date

Exceedance probability

Exceedance probability

A B

D C

Flow-duration curve

Flow-duration curve

Figure 2. Graphical representation of the QPPQ methodology, showing A, observed daily mean streamflow 

at a reference streamgage, B, flow-duration curve at the reference streamgage, C, constructed flowduration curve at the ungaged stream location, and D, estimated daily mean streamflow at the ungaged 

stream location. (Modified from Archfield and others, 2010; Stuckey and others, 2014.)
Estimation of Baseline Daily Mean Streamflow 5

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# Delaware River

43°

42°

41°

40°

39°

77° 76° 75° 74° 73°

EXPLANATION

# U.S. Geological Survey streamgage location

Major rivers and streams

Delaware River Basin boundary

U.S. Geological Survey streamgage basin

0 9 18 27 36 MILES

0 25 50 KILOMETERS

Delaware 

Bay Chesapeake Bay

Atlantic Ocean

NEW YORK

PENNSYLVANIA

MARYLAND

DELAWARE

NEW JERSEY

DISTRICT OF

COLUMBIA

VIRGINIA

MASSACHUSETTS

VERMONT

CONNECTICUT

Base modified from U.S. Geological Survey 1:100,000-scale 

and 1:250,000-scale digital data

Lower 

Delaware 

River 

Basin

Upper Delaware 

River Basin

Figure 3. Location of U.S. Geological Survey reference streamgages in or near the Delaware River Basin.
6 Estimation of Daily Mean Streamflow for Ungaged Stream Locations in the Delaware River Basin, Water Years 1960–2010

individual exceedance probability and is used when discussing 

methodology associated with a generic FDC.

The FDC for an ungaged stream location is constructed 

from estimates of streamflow. Streamflow at the ungaged 

stream location is estimated using the equivalent exceedance 

probabilities (22 percentiles for this study) from regression 

equations developed using basin characteristics and streamflow data from reference streamgages. Interpolation between 

exceedance probabilities of the 22 regression equations is used 

to determine all other streamflow percentiles. The conjunction 

of interpolation and regression equations yields a continuous 

daily hydrograph consisting of 18,628 streamflow values (one 

value for each day in water years 1960–2010) for the ungaged 

stream 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 stream location. Selection of a reference streamgage 

is performed in DRB-SET by default using map correlation 

(Archfield and others, 2010; Archfield and Vogel, 2010), 

although selection of the closest streamgage and selection by 

the user of a streamgage are also supported. Map correlation is 

a geostatistical procedure for determining the streamgage with 

streamflow that exhibits the strongest correlation with streamflow at an ungaged stream location.

Reference Streamgages in the Delaware River 

Basin

The streamflow at a reference streamgage constitutes a 

composite of the upstream land cover, geology, and hydrologic 

characteristics that 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 data collection. Data on observed streamflows at reference streamgages are used in this analysis to 

develop regression equations for estimating streamflows at 22 

exceedance probabilities and for development of correlation 

maps.

Reference Streamgage Criteria

Reference streamgages selected for this analysis had 

streamflow that was minimally altered by regulation, diversion, mining, or other anthropogenic activities and had at 

least 10 years of continuous record. Substantial regulation for 

this analysis is defined by upstream reservoir impoundments 

that control at least 10 percent of the contributing drainage 

area at the streamgage. Information on diversions and mining 

effects were obtained from USGS Annual Water Data Reports, 

available online from 2006 through 2014 at http://wdr.water.

usgs.gov/ and in paper format prior to 2006. Streamgages 

with questionable regulation in Pennsylvania 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). If the results of this evaluation indicated that the 

streamflow at the streamgage was affected by regulation, the 

streamflow data were excluded from the overall analysis. The 

unaltered part of the record at streamgages that yield flow 

records altered by upstream regulation was included in the 

study if there was at least 10 years of unaltered flow before 

the impoundment was constructed. Streamgages outside of 

Pennsylvania were also reviewed for suitability as a reference 

streamgage by personnel in the respective USGS Water 

Science Center. There were 109 streamgages in or near the 

Delaware River Basin that met the above criteria—44 in 

Pennsylvania, 33 in New York, 17 in New Jersey, and 15 in 

Delaware (fig. 3). Of the 109 streamgages, 24 were outside the 

Delaware River Basin but were included for a more regional 

spatial coverage. The average number of years of record is 47 

years for the 109 reference streamgages selected for use in this 

study. A complete listing of streamgages used in the analysis is 

presented in table 1.

The percentage of impervious area within a basin was 

used to identify streamgages with potential anthropogenic 

effects on streamflow (Fry and others, 2011). In most of 

the study area, baseline conditions were defined using data 

from reference streamgages with less than 10 percent of the 

upstream area covered by impervious surfaces. However, 

in large urban/suburban areas, such as in and around the 

Philadelphia/Camden, New Jersey area, some streamgages 

with a high percentage of impervious area were retained for 

improved spatial coverage. Historical maps indicate that 

much of the Philadelphia area has not undergone significant 

change in impervious area since the early 1900s (http://www.

philageohistory.org/tiles/viewer/). The percent impervious area 

upstream from streamgages used in the analysis ranged from 

0.0 to 32 percent, with 11 reference streamgages having more 

than 10 percent impervious area (fig. 4). 

Record Extension

Estimation of daily mean streamflow using the QPPQ 

method for WY 1960–2010 for any ungaged stream location 

requires that all reference streamgages have a complete daily 

mean streamflow record for the same period. Of the 109 reference streamgages, 36 had a complete daily mean streamflow 

record with unaltered flow for the study period. The remaining streamgages had record lengths of 9–50 years during the 

study period. Streamflow records that were incomplete over 

the study period were extended to the complete period using 

the Streamflow Record Extension Facilitator (SREF) (Granato, 

2009). The average number of years of record during the study 

period that required record extension was 24 years, with a 

range of 1–42 years (fig. 5). Estimated streamflow data from 

the record extension analysis were not used in the development of regression equations or correlation maps.
Estimation of Baseline Daily Mean Streamflow 7

Table 1. U.S. Geological Survey reference streamgages in and near the Delaware River Basin.—Continued

[USGS, U.S. Geological Survey; HUC8, 8-digit hydrologic unit code; water year, the 12-month period starting October 1, and ending September 30 of the 

following year]

USGS 

streamgage 

number

Latitude 

(decimal 

degrees)

Longitude 

(decimal 

degrees)

Hydrologic 

Unit Code 

(HUC8)

Period of record 

used in analysis 

(water year)

Station name

01350000 42.319444 -74.436667 2020005 1904–2010 Schoharie Creek at Prattsville, N.Y.

01362200 42.116944 -74.380278 2020006 1964–2010 Esopus Creek at Allaben, N.Y.

01365000 41.866389 -74.487222 2020007 1937–2010 Rondout Creek near Lowes Corners, N.Y.

01365500 41.845000 -74.539444 2020007 1939–1987; 

1999–2010 Chestnut Creek at Grahamsville, N.Y.

01366650 41.714167 -74.389167 2020007 1957–1977 Sandburg Creek at Ellenville, N.Y.

01368500 41.344444 -74.487778 2020007 1944–1968 Rutgers Creek at Gardnerville, N.Y.

01369000 41.275556 -74.471667 2020007 1938–1979 Pochuck Creek near Pine Island, N.Y.

01401000 40.333056 -74.681944 2030105 1954–2010 Stony Brook at Princeton, N.J.

01401650 40.468056 -74.648889 2030105 1980–2010 Pike Run at Belle Mead, N.J.

01403540 40.636389 -74.451389 2030105 1975–2010 Stony Brook at Watchung, N.J.

01411000 39.594722 -74.851667 2040302 1926–2010 Great Egg Harbor River at Folsom, N.J.

01411300 39.306944 -74.820556 2040302 1970–2010 Tuckahoe River at Head of River, N.J.

01411500 39.495556 -75.076944 2040206 1933–2010 Maurice River at Norma, N.J.

01413500 42.144722 -74.653611 2040102 1937–2010 East Branch Delaware River at Margaretville, N.Y.

01414500 42.106111 -74.730556 2040102 1937–2010 Mill Brook near Dunraven, N.Y.

01415000 42.120000 -74.818611 2040102 1937–2010 Tremper Kill near Andes, N.Y.

01418500 41.963056 -74.866944 2040102 1937–1970 Beaver Kill at Craigie Clair, N.Y.

01419500 41.903333 -74.812778 2040102 1938–1970 Willowemoc Creek near Livingston Manor, N.Y.

01420000 41.872778 -74.797222 2040102 1925–1981 Little Beaver Kill near Livingston Manor, N.Y.

01420500 41.946389 -74.979722 2040102 1914–2010 Beaver Kill at Cooks Falls, N.Y.

01421614 42.349444 -74.611111 2040101 1999–2009 Town Brook Tributary Southeast of Hobart, N.Y.

01421618 42.361111 -74.662222 2040101 1998–2010 Town Brook Southeast of Hobart, N.Y.

01421900 42.280278 -74.907222 2040101 1937–1970; 

1997–2010 West Branch Delaware River upstream from Delhi, N.Y.

01422389 42.238611 -74.736111 2040101 1998–2009 Coulter Brook near Bovina Center, N.Y.

01422500 42.252222 -74.901667 2040101 1938–1970; 

1997–2010 Little Delaware River near Delhi, N.Y.

01422738 42.259444 -75.041944 2040101 1999–2009 Wolf Creek at Mundale, N.Y.

01422747 42.172778 -75.121389 2040101 1999–2010 East Brook East of Walton, N.Y.

01423000 42.166111 -75.140000 2040101 1951–2010 West Branch Delaware River at Walton, N.Y.

01423500 42.121944 -75.246944 2040101 1953–1968 Dryden Brook near Granton, N.Y.

0142400103 42.173611 -75.279444 2040101 1953–1967; 

1997–2010 Trout Creek near Trout Creek, N.Y.

01424108 42.187778 -75.315556 2040101 1998–2007 Sherruck Brook Tributary near Trout Creek, N.Y.

01425500 42.161111 -75.392778 2040101 1935–1968 Cold Spring Brook at China, N.Y.

01425675 42.174444 -75.440000 2040101 1970–1981 Oquaga Creek near North Sanford, N.Y.

01426000 42.058611 -75.428056 2040101 1941–1973 Oquaga Creek at Deposit, N.Y.

01427500 41.760833 -75.048333 2040101 1941–1982 Callicoon Creek at Callicoon, N.Y.

01428000 41.563889 -75.014444 2040101 1946–1973 Tenmile River at Tusten, N.Y.

01428750 41.674530 -75.376013 2040103 1987–2010 West Branch Lackawaxen River near Aldenville, Pa.

01431000 41.484811 -75.221842 2040103 1946–1960 Middle Creek near Hawley, Pa.
8 Estimation of Daily Mean Streamflow for Ungaged Stream Locations in the Delaware River Basin, Water Years 1960–2010

Table 1. U.S. Geological Survey reference streamgages in and near the Delaware River Basin.—Continued

[USGS, U.S. Geological Survey; HUC8, 8-digit hydrologic unit code; water year, the 12-month period starting October 1, and ending September 30 of the 

following year]

USGS 

streamgage 

number

Latitude 

(decimal 

degrees)

Longitude 

(decimal 

degrees)

Hydrologic 

Unit Code 

(HUC8)

Period of record 

used in analysis 

(water year)

Station name

01435000 41.890000 -74.590000 2040104 1938–2010 Neversink River near Claryville, N.Y.

01439500 41.088151 -75.037675 2040104 1909–2010 Bush Kill at Shoemakers, Pa.

01440000 41.106111 -74.952500 2040104 1924–2010 Flat Brook near Flatbrookville, N.J.

01440400 41.084815 -75.214625 2040104 1958–2010 Brodhead Creek near Analomink, Pa.

01442500 40.998706 -75.142679 2040104 1951–2010 Brodhead Creek at Minisink Hills, Pa.

01443500 40.980833 -74.953333 2040105 1922–2010 Paulins Kill at Blairstown, N.J.

01445000 40.980833 -74.776389 2040105 1940–2010 Pequest River at Huntsville, N.J.

01445500 40.830556 -74.977778 2040105 1922–2010 Pequest River at Pequest, N.J.

01446000 40.843333 -75.046389 2040105 1923–2010 Beaver Brook near Belvidere, N.J.

01447500 41.130363 -75.625467 2040106 1944–2010 Lehigh River at Stoddartsville, Pa.

01447720 41.084808 -75.605467 2040106 1962–1984 Tobyhanna Creek near Blakeslee, Pa.

01448500 41.035643 -75.543243 2040106 1949–1996 Dilldown Creek near Long Pond, Pa.

01449360 40.897592 -75.502408 2040106 1967–2010 Pohopoco Creek at Kresgeville, Pa.

01450500 40.806205 -75.597964 2040106 1940–2010 Aquashicola Creek at Palmerton, Pa.

01451500 40.582320 -75.482961 2040106 1946–2010 Little Lehigh Creek near Allentown, Pa.

01451800 40.661762 -75.626854 2040106 1967–2010 Jordan Creek near Schnecksville, Pa.

01452000 40.623153 -75.482405 2040106 1945–2010 Jordan Creek at Allentown, Pa.

01452500 40.641209 -75.379347 2040106 1949–2010 Monocacy Creek at Bethlehem, Pa.

01459500 40.433715 -75.116561 2040105 1936–1973 Tohickon Creek near Pipersville, Pa.

01464500 40.137222 -74.600000 2040201 1938–2010 Crosswicks Creek at Extonville, N.J.

01464907 40.229275 -75.119616 2040201 1999–2010 Little Neshaminy Creek at Valley Road, Pa.

01465798 40.057056 -74.985169 2040202 1966–2010 Poquessing Creek at Grant Ave. at Philadelphia, Pa.

01466500 39.885000 -74.505278 2040202 1954–2010 McDonalds Branch in Byrne State Forest, N.J.

01467048 40.050111 -75.032671 2040202 1966–2010 Pennypack Creek at Lower Rhawn St. Bdg., Phila., Pa.

01467086 40.046500 -75.110730 2040202 1966–2010 Tacony Creek at County Line, Philadelphia, Pa.

01467150 39.903056 -75.021389 2040202 1964–2010 Cooper River at Haddonfield, N.J.

01468500 40.629258 -76.124662 2040203

1948–1953; 

1964–1965; 

1974–2010

Schuylkill River at Landingville, Pa.

01470500 40.522593 -75.998268 2040203 1948–2008 Schuylkill River at Berne, Pa.

01470756 40.514261 -75.882982 2040203 1974–1995 Maiden Creek at Virginville, Pa.

01470779 40.413426 -76.171613 2040203 1975–2008 Tulpehocken Creek near Bernville, Pa.

01471000 40.368982 -75.979102 2040203 1951–1978 Tulpehocken Creek near Reading, Pa.

01471980 40.272873 -75.679910 2040203 1975–2004 Manatawny Creek near Pottstown, Pa.

01472000 40.241763 -75.651575 2040203 1928–1978 Schuylkill River at Pottstown, Pa.

01472157 40.151491 -75.601305 2040203 1969–2008 French Creek near Phoenixville, Pa.

01472174 40.089548 -75.630203 2040203 1967–1983 Pickering Creek near Chester Springs, Pa.

01472198 40.393988 -75.515459 2040203 1982–2008 Perkiomen Creek at East Greenville, Pa.

01472199 40.373988 -75.522403 2040203 1982–2008 West Branch Perkiomen Creek at Hillegass, Pa.

01473120 40.164550 -75.433239 2040203 1967–1994 Skippack Creek near Collegeville, Pa.
Estimation of Baseline Daily Mean Streamflow 9

Table 1. U.S. Geological Survey reference streamgages in and near the Delaware River Basin.—Continued

[USGS, U.S. Geological Survey; HUC8, 8-digit hydrologic unit code; water year, the 12-month period starting October 1, and ending September 30 of the 

following year]

USGS 

streamgage 

number

Latitude 

(decimal 

degrees)

Longitude 

(decimal 

degrees)

Hydrologic 

Unit Code 

(HUC8)

Period of record 

used in analysis 

(water year)

Station name

01475510 39.929002 -75.272406 2040202 1965–1990 Darby Creek near Darby, Pa.

01475530 39.974835 -75.279907 2040202 1965–2008 Cobbs Creek at U.S. Highway No. 1 at Philadelphia, Pa.

01475850 39.976499 -75.436586 2040202 1982–2008 Crum Creek near Newtown Square, Pa.

01477120 39.740556 -75.259167 2040202 1967–2010 Raccoon Creek near Swedesboro, N.J.

01477800 39.760972 -75.518694 2040205 1945–2010 Shellpot Creek at Wilmington, Del.

01478000 39.637389 -75.727889 2040205 1943–2010 Christina River at Coochs Bridge, Del.

01479000 39.699222 -75.675028 2040205 1932–2010 White Clay Creek near Newark, Del.

01479820 39.816777 -75.691601 2040205 1988–2008 Red Clay Creek near Kennett Square, Pa.

01480000 39.762806 -75.636500 2040205 1943–2010 Red Clay Creek at Wooddale, Del.

01480015 39.715750 -75.639944 2040205 1989–2010 Red Clay Creek near Stanton, Del.

01480100 39.734835 -75.586869 2040205 1964–1981 Little Mill Creek at Elsmere, Del.

01480300 40.072879 -75.860774 2040205 1961–2008 West Branch Brandywine Creek near Honey Brook, Pa.

01480675 40.097879 -75.741599 2040205 1967–2008 Marsh Creek near Glenmoore, Pa.

01481000 39.869833 -75.593262 2040205 1912–1953; 

1963–1973 Brandywine Creek at Chadds Ford, Pa.

01482500 39.643889 -75.330278 2040206 1941–1984; 

2002–2010 Salem River at Woodstown, N.J.

01483000 39.565556 -75.360556 2040206 1953–1972 Alloway Creek at Alloway, N.J.

01483500 39.232889 -75.632150 2040207 1943–1975 Leipsic River near Cheswold, Del.

01484000 38.975947 -75.567147 2040207 1932–2009 Murderkill River near Felton, Del.

01484100 38.905778 -75.512750 2040207 1958–2010 Beaverdam Branch at Houston, Del.

01484270 38.761501 -75.267134 2040207 1971–2005 Beaverdam Creek near Milton, Del.

01484300 38.814279 -75.327137 2040207 1957–1978 Sowbridge Branch near Milton, Del.

01484500 38.638861 -75.341972 2060010 1943–2004 Stockley Branch at Stockley, Del.

01487000 38.728333 -75.561861 2060008 1935–2010 Nanticoke River near Bridgeville, Del.

01488500 38.849694 -75.673111 2060008 1935–2003; 

2005–2010 Marshyhope Creek near Adamsville, Del.

01498500 42.445000 -74.963611 2050101 1938–1975 Charlotte Creek at West Davenport, N.Y.

01499000 42.450833 -75.114722 2050101 1941–1968 Otego Creek near Oneonta, N.Y.

01503000 42.035278 -75.803056 2050101 1913–2010 Susquehanna River at Conklin, N.Y.

01533950 41.574802 -75.641855 2050106 1961–1978 South Branch Tunkhannock Creek near Montdale, Pa.

01534000 41.558410 -75.894642 2050106 1914–2010 Tunkhannock Creek near Tunkhannock, Pa.

01538000 41.059250 -76.093540 2050107 1920–2010 Wapwallopen Creek near Wapwallopen, Pa.

01539000 41.078141 -76.431056 2050107 1936–2010 Fishing Creek near Bloomsburg, Pa.

01576754 39.946489 -76.367739 2050306 1985–2010 Conestoga River at Conestoga, Pa.

01578400 39.894826 -76.113564 2050306 1963–1981 Bowery Run near Quarryville, Pa.
10 Estimation of Daily Mean Streamflow for Ungaged Stream Locations in the Delaware River Basin, Water Years 1960–2010

The methodology used for the SREF relies on the 

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

record for 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 the 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, 2002). The MOVE.1 

method (Hirsch, 1982) was used for this analysis.

The daily mean 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 applies a streamflow-recession constant 

beginning with the last nonzero streamflow value prior to the 

zero-flow sequence. This option was selected for the analysis 

of the reference streamgages to avoid imposing an arbitrary 

constant flow value over a potentially substantial period of 

low-flow values that would result in a flat line hydrograph for 

streamgages at their zero-flow threshold. A recession constant 

of 0.9 was selected on the basis of prior sampling of low-flow 

recession rates in Pennsylvania (Stuckey and others, 2014). 

The streamgages used to extend the record of a 

streamgage with an incomplete period of record during 

WY 1960–2010 are termed “index streamgages.” Ten years 

was considered the minimum streamflow record length for 

an acceptable application of MOVE.1. A maximum of three 

streamgages was used for record extension to cover the 

incomplete study period (Appendix 1). Selection of index 

streamgages was based on period of available concurrent 

record, strength of correlation, and distribution of LOC residuals (Granato, 2009). Record prior to 1960 was used when 

necessary to establish the relation between streamgages with 

an incomplete period of record and the index streamgage. The 

concurrent records were evaluated graphically and statistically 

using correlation to ensure a good fit between the index 

streamgage and a streamgage with an incomplete period of 

record. Record extension correlations ranged from 0.742 to 

0.988, with a mean of 0.894. A maximum correlation of 1.0 

indicates a perfect linear relation. A listing of streamgages 

with record extension techniques applied is provided in 

Appendix 1.

Regression Equations for Estimating Streamflow 

at Flow-Duration Exceedance Probabilities

Regression equations were developed for 22 percentiles 

along the FDC using observed streamflow data from reference streamgages in and near the Delaware River Basin from 

0

20

40

60

80

100

0 5 10 15 20 25 30 35

Percent impervious area

Number of reference streamgages

1 7 13 19 25 31 37 43

Years of record extension

0

5

10

15

20

Number of refernce streamgages

requiring record extension

Figure 4. Histogram showing percent impervious area in the 

reference streamgage subbasins within the Delaware River Basin.

Figure 5. Histogram showing the number of reference 

streamgages requiring record extension and the number of years 

of record extension, Delaware River Basin.
Estimation of Baseline Daily Mean Streamflow 11

the beginning of observed record through WY 2010. Values 

for basin characteristics with possible effects on a range of 

streamflows, 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 

unaltered flow. The observed exceedance probability discharges (dependent variable) were related to the basin characteristics (independent or explanatory variables) using regression techniques.

Flow-Duration Exceedance Probabilities 

and Basin Characteristics for Reference 

Streamgages

Daily streamflow values for the selected reference 

streamgages were retrieved from the National Water 

Information System web application (NWISWeb) (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 governing equations and statistical methods utilized in 

MkPP are documented by Granato (2009). The Weibull plotting position option was used. Only the period of record for 

observed unaltered flow at the reference streamgage was used 

to compute the exceedance probabilities for use in the regression analysis. No extended streamflow record was used to 

compute the exceedance probabilities.

A list of 43 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 2). 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. National datasets were 

emphasized and utilized whenever available to limit issues 

pertaining to State and local boundaries. 

Regression Analysis and Resulting FlowDuration Exceedance Probability Regression 

Equations

The exceedance probability discharges for observed 

streamflows were related to basin characteristics using exploratory ordinary least squares (OLS) and weighted least squares 

(WLS) regression techniques. The exceedance probabilities 

associated with each reference streamgage were weighted 

using the following expression for the WLS regression techniques to account for differing periods of record: (number of 

years of record at streamgage*number of streamgages)/sum of 

years of record of all streamgages. Regression analyses were 

performed using the statistical package Spotfire S+ (TIBCO 

Software Inc., 2008). Regression diagnostics used to evaluate 

the resulting regressions included graphical relations, multicollinearity, prediction error sum of squares (PRESS) statistic, 

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

and Hirsch, 2002).

Streamflow data from reference streamgages in and near 

the Delaware River Basin were used to develop regression 

equations for estimating the 1-, 2-, 5-, 10-, 15-, 20-, 25-, 30-, 

40-, 50-, 60-, 70-, 75-, 80-, 85-, 90-, 95-, 98-, and 99-percent 

exceedance probability discharges (designated as P1, P2, 

P5, P10, P15, P20, P25, P30, P40, P50, P60, P70, P75, P80, 

P85, P90, P95, P98, and P99, respectively). Two additional 

regression equations were developed for the 0.0054- and 

99.9946-percent flow-duration exceedances (P0.0054 and 

P99.9946, respectively) to represent the ends of the FDC for 

the period from 1960 to 2010 (51 years), and an equation was 

developed for the 99.95-percent flow-duration exceedance 

(P99.95) to further define the low end of the FDC. Because 

only observed data were used in the regression analysis and 

those extreme exceedances require additional years of record 

(data points) to compute, the streamgages used to develop 

the regression equations for the lower and upper ends of the 

FDC were limited to those with at least 51 years of record. 

As a result, 40 streamgages had a sufficient period of record, 

regardless of whether this period was contained within the 

study period, and were used to develop regression equations 

for estimating the P0.0054, P99.9946, and P99.95 exceedance 

probability discharges. 

Outliers and streamgages with high leverage and (or) 

influence were removed from an individual regression analysis 

only if sufficient data or information were found to support 

the removal of the streamgages, such as high water use in the 

basin (including withdrawals and discharges), basin characteristic or streamflow values well outside the normal or 

expected range for that variable, or poor or estimated daily 

streamflow computations during low- or high-flow periods. 

Three streamgages with a P99.9946 exceedance probability 

discharge equaling zero and one streamgage with a P99.95 

exceedance probability discharge equaling zero were excluded 

from the regression analysis for those particular exceedance 

probabilities. 

During exploratory regression analysis, regression 

models were developed for the entire basin using different 

regions that were based on physiographic province, hydrologic unit code (HUC) 8 boundaries, and residual standard 

errors. The results of these models were then compared to 

each other using standard errors, coefficient of determination 

(R2), residuals, PRESS statistic, and other regression diagnostics. Insufficient data were available, owing to the small 

number of streamgages in some physiographic provinces, to 

develop robust regression models by region that would have 

adequately predicted streamflows for all 22 exceedance probabilities, even when some physiographic provinces were combined to make larger regions. The basin-wide regression model 
12 Estimation of Daily Mean Streamflow for Ungaged Stream Locations in the Delaware River Basin, Water Years 1960–2010

Table 2. Basin characteristics used in the development of regression equations for flow-duration exceedance probabilities for 

streams in the Delaware River Basin.—Continued

[>, greater than]

Variable Source Reference Unit

Drainage area Digital Elevation Model (DEM) Gesch and others (2002) Square miles

Basin slope Digital Elevation Model (DEM) Gesch and others (2002) Degrees

Channel slope Digital Elevation Model (DEM) Gesch and others (2002) Feet/mile

Mean basin elevation Digital Elevation Model (DEM) Gesch and others (2002) Feet 

Maximum basin elevation Digital Elevation Model (DEM) Gesch and others (2002) Feet 

Shape factor Digital Elevation Model (DEM) Gesch and others (2002) Unitless

Percent of basin >1,200 Digital Elevation Model (DEM) Gesch and others (2002) Percent

Soil thickness Soil Survey Geographic dataset 

(SSURGO)

Soil Survey Staff, Natural Resources 

Conservation Service Feet

Sand in soil Soil Survey Geographic dataset 

(SSURGO)

Soil Survey Staff, Natural Resources 

Conservation Service Percent

Clay in soil Soil Survey Geographic dataset 

(SSURGO)

Soil Survey Staff, Natural Resources 

Conservation Service Percent

Hydrologic group A Soil Survey Geographic dataset 

(SSURGO)

Soil Survey Staff, Natural Resources 

Conservation Service Percent

Hydrologic group B Soil Survey Geographic dataset 

(SSURGO)

Soil Survey Staff, Natural Resources 

Conservation Service Percent

Hydrologic group C Soil Survey Geographic dataset 

(SSURGO)

Soil Survey Staff, Natural Resources 

Conservation Service Percent

Hydrologic group D Soil Survey Geographic dataset 

(SSURGO)

Soil Survey Staff, Natural Resources 

Conservation Service Percent

Percent coarse fragments Soil Survey Geographic dataset 

(SSURGO)

Soil Survey Staff, Natural Resources 

Conservation Service Percent

Poorly drained Soil Survey Geographic dataset 

(SSURGO)

Soil Survey Staff, Natural Resources 

Conservation Service Percent

Well drained Soil Survey Geographic dataset 

(SSURGO)

Soil Survey Staff, Natural Resources 

Conservation Service Percent

Saturated hydraulic conductivity Soil Survey Geographic dataset 

(SSURGO)

Soil Survey Staff, Natural Resources 

Conservation Service

Micrometers/

second

Till/glacial Soil Survey Geographic dataset 

(SSURGO)

Soil Survey Staff, Natural Resources 

Conservation Service Percent

Mean annual precipitation 

Parameter-elevation Regressions on 

Independent Slopes Model (PRISM) 

1981–2010

Daly and others (1994) Inches

Winter mean precipitation 

(Dec., Jan., Feb.)

Parameter-elevation Regressions on 

Independent Slopes Model (PRISM) 

1981–2010

Daly and others (1994) Inches

Spring mean precipitation 

(Mar., Apr., May)

Parameter-elevation Regressions on 

Independent Slopes Model (PRISM) 

1981–2010

Daly and others (1994) Inches

Summer mean precipitation 

(June, July, Aug.)

Parameter-elevation Regressions on 

Independent Slopes Model (PRISM) 

1981–2010

Daly and others (1994) Inches

Fall mean precipitation 

(Sep., Oct., Nov.)

Parameter-elevation Regressions on 

Independent Slopes Model (PRISM) 

1981–2010

Daly and others (1994) Inches
Estimation of Baseline Daily Mean Streamflow 13

Table 2. Basin characteristics used in the development of regression equations for flow-duration exceedance probabilities for 

streams in the Delaware River Basin.—Continued

[>, greater than]

Variable Source Reference Unit

Low-flow season precipitation 

(July, Aug., Sep.)

Mean annual temperature

Mean daily maximum temperature

Winter mean temperature 

(Dec., Jan., Feb.)

Spring mean temperature 

(Mar., Apr., May)

Summer mean temperature 

(June, July, Aug.)

Fall mean temperature 

(Sep., Oct., Nov.)

Low-flow season temperature 

(July, Aug., Sep.)

Imperviousness

Forested area (classes 41, 42, 43)

Evergreen (class 42)

Urban (classes 23, 24)

Developed (classes 21, 22, 23, 24)

Open water (class 11)

Storage (classes 11, 90, 95)

Longitude at outlet

Latitude at outlet

Longitude at centroid

Latitude at centroid

Parameter-elevation Regressions on 

Independent Slopes Model (PRISM) 

1981–2015

Parameter-elevation Regressions on 

Independent Slopes Model (PRISM) 

1981–2016

Parameter-elevation Regressions on 

Independent Slopes Model (PRISM) 

1981–2017

Parameter-elevation Regressions on 

Independent Slopes Model (PRISM) 

1981–2018

Parameter-elevation Regressions on 

Independent Slopes Model (PRISM) 

1981–2019

Parameter-elevation Regressions on 

Independent Slopes Model (PRISM) 

1981–2020

Parameter-elevation Regressions on 

Independent Slopes Model (PRISM) 

1981–2021

Parameter-elevation Regressions on 

Independent Slopes Model (PRISM) 

1981–2022

National Land Cover Dataset 2006 

(NLCD 2006)

National Land Cover Dataset 2006 

(NLCD 2006)

National Land Cover Dataset 2006 

(NLCD 2006)

National Land Cover Dataset 2006 

(NLCD 2006)

National Land Cover Dataset 2006 

(NLCD 2006)

National Land Cover Dataset 2006 

(NLCD 2006)

National Land Cover Dataset 2006 

(NLCD 2006)

Daly and others (1994)

Daly and others (1994)

Daly and others (1994)

Daly and others (1994)

Daly and others (1994)

Daly and others (1994)

Daly and others (1994)

Daly and others (1994)

Fry and others (2011)

Fry and others (2011)

Fry and others (2011)

Fry and others (2011)

Fry and others (2011)

Fry and others (2011)

Fry and others (2011)

Inches

Degrees Fahrenheit

Degrees Fahrenheit

Degrees Fahrenheit

Degrees Fahrenheit

Degrees Fahrenheit

Degrees Fahrenheit

Degrees Fahrenheit

Percent

Percent

Percent

Percent

Percent

Percent

Percent

Decimal degrees

Decimal degrees

Decimal degrees

Decimal degrees
14 Estimation of Daily Mean Streamflow for Ungaged Stream Locations in the Delaware River Basin, Water Years 1960–2010

performed as well as, if not better than, the other regionalization models generated during the exploratory analysis, and it 

was used to develop the suite of 22 exceedance probability 

regression equations. WLS was used to generate the final 

basin-wide regression equations.

The following independent variables were found to be 

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

regression equations: latitude at the outlet, drainage area, 

mean annual precipitation (1981–2010), mean winter precipitation (December–February; 1981–2010), saturated hydraulic 

conductivity, and percentages of poorly drained soil and sand 

in soil (table 3). The values for basin characteristics associated 

with the streamgages used in the analysis are listed in 

Appendix 2. To form a near-linear relation between the flowduration 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, a value of 1.0 was added to the decimal 

form of the percentages of poorly drained soil and sand in soil 

before the variables were log transformed.

The regression model took the following form, in log 

units:



( )

( ) ( )

1 01

1 01

.

. . *

. *

L p ogQ A bLogDA cLogLat dLogPPT ANN

eLogPPT WIN fLog POOR

gLog SAND hLog KSAT

= + + +

+ + +

+ + +

 (1)

or in arithmetic space:

 ( ) ( ) ( ) ( )

( ) ( ) ( )

10

1 01 1 01

. .

. * . *

A b c d e

p

f g h

Q DA Lat PPT ANN PPT WIN

POOR SAND KSAT

=

+ +

 (2)

where

Log = log to base 10;

 

Qp = discharge at flow-duration exceedance 

probability, in cubic feet per second (ft3/s);

A = the intercept, estimated by WLS;

DA = drainage area, in square miles;

Lat = latitude of the outlet of the basin, in decimal 

degrees;

PPT.ANN = mean annual precipitation, in inches;

PPT.WIN = mean winter precipitation, in inches;

POOR = poorly drained soil, in percent;

SAND = sand in soil, in percent;

KSAT = saturated hydraulic conductivity, in 

micrometers per second; and

b, c, d, e, f, 

g, and h = independent variable coefficients of 

regression estimated by WLS.

The coefficients for the resulting regression equations 

are listed in table 3. All basin characteristic coefficients were 

checked for continuity issues and expected effect on flow. 

Generally, the coefficients did not have any continuity issues, 

except where changes occurred to the suite of regressions or 

where exceedances were closer together than elsewhere along 

the FDC. These continuity issues did not appear to affect 

the performance of the regressions. All basin characteristic 

coefficients reflected expected signage, and resulting changes 

to streamflow were reasonable. For example, as the percentage of poorly drained soil increased, discharge decreased for 

low and medium flows; for high flows, as the percentage of 

poorly drained soil increased, discharge also increased. This is 

because for low and medium flows, water infiltrating through 

the poorly drained soils is hindered from entering the groundwater, which would result in a lower base-flow contribution to 

the stream. During high flows, the poorly drained soil acts as 

an impervious surface, increasing overland flow and runoff, 

which would result in higher streamflows. 

Flow-duration exceedance probability discharges 

computed from streamflow data (observed) and regression 

equations (predicted) for streamgages used in the regression 

analysis are listed in Appendix 3. The predicted exceedance 

probability discharges computed from the regression equations 

for the reference streamgages were checked for continuity, and 

no issues or problems were found.

Standard errors of prediction (Helsel and Hirsch, 2002) 

for regression equations provide an estimate of reliability of 

the predicted variable, in this case, streamflow at 22 exceedance probabilities (table 3). The standard error of prediction is 

a measure of the average accuracy of the regression equations 

when predicting values for ungaged stream locations; about 

two-thirds of the regression estimates for ungaged stream locations will have errors less than the average standard errors of 

prediction given for the equations (Ries, 2007). The standard 

error of prediction for the flow-duration exceedance probability regression equation ranges from 0.05 to 0.30 in log units 

(11 percent to 79 percent; table 3); median and mean standard 

error over the entire suite of flow-duration equations is 24 

and 32 percent, respectively. The regression equations used to 

estimate the lower ends of the FDC have the highest errors; 

the extreme low-flow exceedance probability of P99.9946 has 

an error of 79 percent, and P99.95 and P99 have errors of 69 

percent and 64 percent, respectively. Regressions to estimate 

extreme low-flow statistics typically have higher associated 

errors because low flows are dependent on multifaceted factors 

such as underlying geology and evapotranspiration, which can 

be difficult to capture as independent parameters in a regression model. 

The coefficient of determination (R2) provides a way to 

estimate the uncertainty associated with the regression. For 

example, the R2 for P60 is 0.98, indicating the basin characteristics selected for use in the P60 regression equation accounted 

for 98 percent of the variability in streamflow for the 60-percent exceedance value (table 3). A lower R2

 for P99.9946 

(0.81) indicates that other variables may help to better define 

this extreme low-flow prediction. Multicollinearity between 

the basin characteristics was evaluated for significance in each 

regression equation using variance inflation factor (VIF) and 

correlation. The maximum VIF between the independent variables is 1.5, and the maximum correlation is 0.5, indicating no 

issues with multicollinearity.
Estimation of Baseline Daily Mean Streamflow 15

Table 3. Regression coefficients for use with flow-duration exceedance probability regression equations for streams in the Delaware River Basin.[--, not applicable]

Flowduration 

exceedance 

probability

Intercept

Basin characteristic coefficients

Coefficient of 

determination 

(R2)

Standard error of 

prediction

Drainage 

area 

(square 

miles)

Latitude at 

outlet 

(decimal 

degrees)

Mean annual 

precipitation 

(inches)

Mean winter 

precipitation 

(inches)

Poorly 

drained soil 

(percent)

Sand in soil 

(percent)

Saturated 

hydraulic 

conductivity 

(micrometers/

second)

Log units Percent

P99.9946 -4.3959 1.1307 -- -- 4.5049 -4.3049 -- 0.5645 0.81 0.30 79

P99.95 -4.1035 1.1029 -- -- 4.1949 -4.0969 -- 0.5835 0.83 0.27 69

P99 33.2029 1.1222 -26.2694 4.6408 -- -5.0778 2.1644 -- 0.87 0.25 64P98 32.8459 1.1007 -25.6730 4.3760 -- -4.7792 1.8673 -- 0.89 0.23 57P95 28.7833 1.0832 -22.7789 4.1294 -- -4.0698 1.6034 -- 0.91 0.19 48P90 23.2624 1.0675 -18.9841 3.8737 -- -3.5848 1.4931 -- 0.93 0.17 41P85 18.3160 1.0608 -15.6972 3.7318 -- -3.1822 1.4620 -- 0.94 0.15 37P80 13.6808 1.0579 -12.5158 3.4956 -- -2.7438 1.3804 -- 0.95 0.14 33P75 9.4482 1.0524 -9.6371 3.3041 -- -2.4207 1.3624 -- 0.96 0.12 29P70 6.1189 1.0443 -7.2406 3.0352 -- -2.1952 1.3583 -- 0.97 0.11 27P60 2.3600 1.0313 -4.3327 2.5920 -- -1.8559 1.0845 -- 0.98 0.09 21P50 -1.7188 1.0295 -1.4696 2.3424 -- -1.4160 1.0029 -- 0.98 0.08 19P40 -5.4898 1.0312 1.1582 2.1301 -- -1.0043 0.9059 -- 0.99 0.07 17P30 -9.8871 1.0337 4.1007 1.9550 -- -0.6564 1.1918 -- 0.99 0.07 16P25 -11.3858 1.0326 5.1642 1.8740 -- -0.4601 1.0580 -- 0.99 0.06 15P20 -12.8310 1.0336 6.1718 1.8212 -- -0.2563 0.8658 -- 0.99 0.06 13P15 -14.0886 1.0277 7.0563 1.7975 -- -0.0051 0.5907 -- 0.99 0.05 12P10 -14.5510 1.0159 7.5043 1.7536 -- 0.2450 0.1710 -- 0.99 0.05 11

P5 -13.7837 0.9881 7.3916 1.6065 -- 0.5542 -0.6415 -- 0.99 0.05 13P2 -12.5259 0.9564 6.9088 1.5536 -- 0.9765 -1.5405 -- 0.98 0.08 18P1 -11.6455 0.9442 6.5207 1.5436 -- 1.2985 -2.0901 -- 0.98 0.09 21

P0.0054 -1.0797 0.9347 -- 2.0318 -- -- -2.3815 -- 0.92 0.15 37
16 Estimation of Daily Mean Streamflow for Ungaged Stream Locations in the Delaware River Basin, Water Years 1960–2010

Selection of Reference Streamgages for 

Estimating Daily Mean Streamflow 

An important consideration in applying the QPPQ 

method is the selection of a reference streamgage. A traditional 

approach has been to select the closest streamgage to the 

ungaged stream location as the representative reference gage. 

Choosing the closest streamgage as the most appropriate 

reference streamgage is based on the assumption that similarity in the conditions determining streamflow increases with 

decreasing distance between two locations (Stuckey and 

others, 2014). However, there are instances where conditions 

at the closest streamgage are neither physically nor hydrologically similar to those at the ungaged stream location. Map 

correlation based on kriging is an alternative to using the 

closest reference streamgage (Archfield and Vogel, 2010). 

These methods for selecting a reference streamgage were 

compared using observed streamflow correlations to indicate 

what the “best,” or most appropriate representative reference 

streamgage should be.

Closest Streamgage

The closest reference streamgage approach was evaluated 

to determine how successful the method was in selecting the 

reference streamgage with streamflows most highly correlated 

to those of the ungaged stream location. The closest reference 

streamgage was defined as the streamgage with the shortest 

distance from the centroid of the basin of the reference 

streamgage to the outlet of the ungaged stream location; this 

method was found to perform best in Pennsylvania by Stuckey 

and others (2014). Observed streamflow correlations using 

Spearman’s rho were calculated among the 86 streamgages 

within the Delaware River Basin to evaluate whether using 

the closest streamgage identifies the most appropriate, or 

best, streamgage. The reference streamgage with the highest 

observed correlations and shortest distance to the ungaged 

stream location was the same 48 percent of the time, and 94 

percent of the time, the closest streamgage was in the top five 

streamgages. 

Map Correlation

Map correlation is a geostatistical approach to selecting a 

reference streamgage where streamflow exhibits the strongest 

correlation with streamflow at an ungaged stream location. 

First, each reference streamgage is assigned a unique map of 

correlation estimates developed from a model of the spatial 

correlation structure, or variogram, between it and all other 

available reference streamgages in and near the Delaware 

River Basin (fig. 6). Ordinary kriging (Isaaks and Srivastava, 

1989) is used to estimate the predicted correlation at the 

ungaged stream location. 

Selection of the most appropriate representative reference 

streamgage is accomplished using the map correlation method 

by choosing the streamgage whose map has the highest 

estimated correlation coefficient at the coordinates of the 

ungaged stream 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 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. 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. 

Variogram models were developed for 109 reference 

streamgages in and near the Delaware River Basin with 

minimally altered streamflow and at least 10 years of continuous record during WY1960–2010. In an attempt to minimize 

subjectivity, the variogram models were developed in the Free 

R Software (http://www.r-project.org/) using default automated parameter estimation. The spherical variogram model 

was used to describe the spatial structure within the correlation 

of daily streamflow. Spearman’s rho, a non-parametric rankbased correlation coefficient, was used to define the correlation between the reference streamgages. Stuckey and others 

(2014) found that Spearman’s rho performed as well as if not 

better than Kendall’s tau in two pilot basins in Pennsylvania. 

All reference streamgage correlations used in the variogram 

development were significant at the 0.05 level.

Map correlation results were evaluated to determine 

how accurately map correlation reproduced the correlation 

coefficient for the reference streamgages and how often the 

streamgage with the highest estimated correlation was the 

same as the streamgage with the highest observed correlation. 

Observed and estimated correlations among streamgages were 

compared for goodness of fit to evaluate the effectiveness of 

the map correlation model. Root mean square error (RMSE) 

values between the observed and estimated streamflow correlations were computed for each of the streamgages using 

observed and estimated correlations. RMSE values ranged 

from 0.031 to 0.081 with a median value of 0.048 (fig. 7). 

When plotted spatially (fig. 7), the highest RMSE values 

(values within the upper quartile range) were generally in the 

northern and central parts of the basin, whereas the lowest 

RMSE values were found in south-central part of the basin. 

This does not necessarily dictate how map correlation overall 

will perform, but shows how well the correlation coefficient at 

each reference streamgage was reproduced. The correlations 

for the 86 streamgages within the Delaware River Basin were 

also evaluated to determine whether the same streamgage had 

the highest observed and estimated correlations. Streamgages 

had the highest observed and estimated correlations 30 percent 

of the time, and streamgages with the highest observed correlation were within the top five estimated correlations 80 

percent of the time. Although these percentages are lower than 

those found using the closest streamgage, variations of the 

correlation coefficients for many streamgages with the highest 

correlations were quite small, on the order of magnitude 0.001. 
Estimation of Baseline Daily Mean Streamflow 17

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

Estimated streamflow 

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 6. Example streamflow correlation map for U.S. Geological Survey streamgage 01559000, Juniata River at Huntingdon, Pa. 

(from Stuckey and others, 2014).
18 Estimation of Daily Mean Streamflow for Ungaged Stream Locations in the Delaware River Basin, Water Years 1960–2010

Delaware River Basin

Root mean square error

0.054

0.048

0.043

0.085

0.030

0.035

0.040

0.045

0.050

0.060

0.070

0.055

0.065

0.075

0.080

State boundary

Delaware River Basin boundary

Root mean square error

75th percentile

50th percentile

25th percentile

Interquartile

(median) range

0.055 – 0.081

0.049 – 0.054

0.044 – 0.048

0.031 – 0.043

EXPLANATION

NEW YORK

PENNSYLVANIA

MARYLAND

NEW JERSEY

DELAWARE

Delaware Bay

Atlantic Ocean

0 10 20 KILOMETERS

0 10 20 MILES

78° 76°

42°

40°

Base modified from U.S. Geological Survey 1:100,000-scale 

and 1:250,000-scale digital data

Figure 7. Distribution of root mean square error between the observed and estimated streamflow correlations, 

resulting from map correlation, for 109 streamgages in and near the Delaware River Basin.
Accuracy and Limitations of Estimated Streamflow 19

Estimation of Altered Daily Mean 

Streamflow

Streamflow is a source of drinking water supply for more 

than 15 million people in the Delaware River Basin. Other 

water uses also affect the amount of water flowing in the 

streams in the basin on any given day. Estimated baseline 

daily mean streamflow generated using the QPPQ method for 

the Delaware River Basin was adjusted using compiled water 

use information to reflect current, or altered, conditions. 

Withdrawals were compiled and reviewed for accuracy by 

water use category as part of the National Water Census 

(Susan Hutson, U.S. Geological Survey, oral commun., 2013). 

The categories of withdrawals are water supply, self-supplied 

domestic, industrial, irrigation, livestock, mining, power/

hydroelectric, remediation, sewage treatment, aquaculture, 

commercial, and thermoelectric. More information on the 

types of water use categories is presented in Hutson and 

others, in press. Return flows were not categorized by sector 

because of insufficient information. The water use data were 

compiled for all states within the Delaware River Basin for 

2010. In addition, water use data were compiled for each year 

from 2005 through 2010 for the parts of the Delaware River 

Basin within Pennsylvania and New Jersey. Estimated daily 

mean streamflows were adjusted to incorporate water use 

using average withdrawals and returns, by month rather than 

annually, to capture seasonal and monthly variation in water 

use.

Use of DRB-SET for Estimating 

Baseline and Altered Daily Mean 

Streamflow at Ungaged Stream 

Locations

DRB-SET is a tool for simulating streamflow at a daily 

time step for an ungaged stream location in the Delaware 

River Basin for WY 1960–2010. DRB-SET is a user friendly 

and time saving tool used to assist water-resource managers 

in determining water allocation, ecological flow, and water 

for human-health needs. DRB-SET is modeled after the BaSE 

(Stuckey and others, 2014) and MASYE (Archfield and others, 2010) and is 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 basin characteristic information, reference streamgage information, baseline 

and altered daily mean streamflow, mean and median streamflow statistics, FDCs, and hydrographs.

Within DRB-SET the user can utilize an interactive map 

to select a location of interest (the ungaged stream location). 

Basin characteristic information for the ungaged stream 

location can be obtained from the interactive map through 

StreamStats Web services (Ries and others, 2008) or entered 

manually. By default, DRB-SET selects an appropriate reference streamgage for a user-entered ungaged stream location 

by maximizing the estimated streamflow correlation (map 

correlation). The user has the option of manually selecting a 

different reference streamgage or using the closest reference 

streamgage to the ungaged stream location. After the initial 

information is entered into DRB-SET, the Compute Daily 

Streamflows function computes the baseline and altered (based 

on water use in the basin, if applicable) daily mean streamflows for the ungaged stream location for WY 1960–2010. 

Any altered streamflow incorporates compiled upstream water 

use into the baseline daily streamflow for the basin by subtracting any withdrawals and adding any return flows.

A report output file, in the form of a Microsoft Excel®

spreadsheet, is generated and summarizes the reference 

streamgage and ungaged stream location information, including basin characteristics and percent difference in basin 

characteristics between the two locations (fig. 8). Mean and 

median statistics are computed for the ungaged stream location. FDCs and hydrographs are presented for the ungaged 

stream location in cubic feet per second (ft3/s) and cubic feet 

per second per square mile [(ft3/s)/mi2]. The water use within 

the basin (if any) is summarized by category in the Water Use 

report. The estimated daily flows for the ungaged stream location, both baseline and altered, 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 information and detailed instructions on the use of 

DRB-SET can be found in Stuckey and Ulrich, in press.

Accuracy and Limitations of Estimated 

Streamflow

Accuracy of estimated daily streamflows for ungaged 

stream locations is dependent on the uncertainties associated 

with the multiple steps that compose the overall process. 

Stuckey and others (2014) outlined the following steps: measurement of streamflow at reference streamgages, streamflow 

record extension at reference streamgages, estimation of the 

streamflow for an ungaged stream location on the basis of 

regression equations, the use of basin characteristics outside 

the range used to develop the equations, selection of a reference streamgage using the map correlation method, and transfer of exceedance probabilities from the reference streamgage 

to the ungaged stream location.

The accuracy of measured streamflow data depends on 

several factors, including the stability of the stage-discharge 

relation, accuracy of measurements of discharge, and interpretation of streamflow records. Records are rated as excellent, 

good, fair, or poor. These ratings specify that 95 percent of the 

daily discharges are within 5 percent (excellent), 10 percent 

(good), or 15 percent (fair) of their true values. The accuracy 

of measured streamflow data is documented for each reference 
20 Estimation of Daily Mean Streamflow for Ungaged Stream Locations in the Delaware River Basin, Water Years 1960–2010 Annual Daily Average Return (Mgal/D) Annual Daily Average Withdrawal (Mgal/D) 31.0965 39.9230 -- 12.4694 -- 27.4536 WS DO IN IR LV MI PH RM ST TE AQ CO January 20.4322 36.01522 34.225 0 0.0549 0 0 1.5796 0 0 0 0 0 0.1554 February 22.412 36.84442 34.742 0 0.0578 0 0 1.8639 0 0 0 0 0 0.1804 March 42.8609 37.97462 35.059 0 0.0665 0 0 2.6815 0 0 0 0 0 0.1676 April 23.4734 38.45602 35.982 0 0.0531 0.0748 0 2.2044 0 0 0 0 0 0.142 May 39.4296 40.15662 38.725 0 0.0533 0.2803 0 0.9512 0 0 0 0 0 0.1472 June 42.7385 44.26495 42.774 0 0.0796 0.4658 0 0.8048 0 0 0 0 0 0.1404 July 41.9428 44.33392 42.863 0 0.0732 0.4701 0 0.7598 0 0 0 0 0 0.1678 August 34.9733 43.12852 41.617 0 0.071 0.6793 0 0.6198 0 0 0 0 0 0.1412 September 37.9796 42.47635 40.965 0 0.0553 0.6269 0 0.6636 0 0 0 0 0 0.166 October 22.8949 40.00652 35.488 0 0.0484 0.141 0 4.1933 0 0 0 0 0 0.1356 November 21.4032 37.65173 34.688 0 0.0528 0.0022 0 2.7534 0 0 0 0 0 0.1552 December 21.8164 37.57112 35.354 0 0.053 0 0 2.0335 0 0 0 0 0 0.1308 Mean daily streamflow 330.00 Median daily streamflow 178.22 *Altered conditions incorporate water use in the watershed Altered* Streamflow statistics for ungaged site (ft3/s) Withdrawal by Category (Mgal/D) Month Total Return (Mgal/D) Total Withdrawal (Mgal/D) USGS 

DRB Streamflow Estimator Tool Water Use Data: 2010 Groundwater Total Surface Water

0

5,000

25,00020,00015,00010,000

IN ESTIMATED MEAN DAILY STREAMFLOW,

CUBIC FEET PER SECOND

Baseline streamflowAltered streamflow

1.000.100.010.00

10.00

100.00

1,000.00

10,000.00

100,000.00

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

, IN ESTIMATED MEAN DAILY STREAMFLOW

CUBIC FEET PER SECOND

EXCEEDANCE PROBABILITY

Baseline streamflowAltered Streamflow

Figure 1. Flow-duration curve in cubic feet per second for ungaged site under baseline and altered flow conditions.

Figure 2. Baseline and altered hydrograph in cubic feet per second for ungaged site.

WS = Water SupplyDO = self-supplied DOmestic

IN = INdustrialIR = IRrigationLV = LiVestockMI = MIningPH = Power, HydroelectricRM = ReMediationST = Sewage TreatmentTE = ThermoElectricAQ = AQuacultureCO = COmmercial

Figure 8. Screen capture of an example report generated by the Delaware River Basin Streamflow Estimator Tool (DRB-SET) showing water use, a flow-duration curve, and a hydrograph.
Accuracy and Limitations of Estimated Streamflow 21

streamgage in annual data reports (http://wdr.water.usgs.gov/) 

through WY2013. Most of the published streamflow records 

for the Delaware River Basin are rated good to fair.

 Streamflow record extension introduces uncertainty to 

baseline streamflow estimates, which is difficult to quantify. 

Because the length of record requiring extension varied by 

streamgage (0 to 82 percent of the record), the uncertainty 

introduced into the overall record also varies. A general sense 

of the accuracy of these streamflow estimates can be obtained 

by observing the correlation coefficients. A maximum correlation of 1.0 indicates a perfect linear relation. In this study, 

correlation coefficients range from 0.742 to 0.988. The correlation coefficients are included in Appendix 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 the logarithm of streamflow at the reference streamgage 

is non-linear, the correlations are likely to decrease, and the 

associated uncertainties are likely to increase. 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.

Uncertainties in the constructed FDC for the ungaged 

stream locations consist of errors in the regression estimates 

of the streamflows at the 22 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 

79 percent. The median and mean predictive errors are 24 and 

32 percent, respectively. All other exceedance probabilities 

that are not predicted from regression equations are log-log 

interpolated. 

DRB-SET relies on estimates of streamflow derived from 

regression equations and is not meant 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 4. The maximum percent 

impervious for watersheds to be used in DRB-SET generally 

should be less than 10 percent. For watersheds with percent 

imperviousness greater than this value, results from DRB-SET 

need to be evaluated very carefully before use. 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 DRB-SET also may not be valid.

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

is introduced into the daily exceedance probabilities for the 

ungaged stream 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. A comparison between 

streamflow estimates resulting from DRB-SET using map 

correlation and the closest streamgage method to select a 

reference streamgage was performed using NSE with the logs 

(base10) of the streamflow. A perfect match of modeled to the 

Table 4. Range of basin characteristics used in the development of regression equations to estimate flow-duration exceedance 

probability discharges for ungaged stream locations within the Delaware River Basin.

Basin characteristic Mean Median Minimum Maximum

Latitude at outlet 

(decimal degrees) 40.760392 40.636665 38.638861 42.450968

Drainage area 

(square miles) 81.2 45.7 0.61 1,147

Mean annual precipitation 

(inches) 47.3 46.6 42.6 59.2

Mean winter precipitation 

(inches) 3.28 3.30 2.69 4.29

Poorly drained soil 

(percent) 7.06 4.26 0.00 47.8

Sand in soil (percent) 42.1 38.4 17.6 86.5

Saturated hydraulic conductivity 

(micrometers/second) 24.9 14.3 3.52 121
22 Estimation of Daily Mean Streamflow for Ungaged Stream Locations in the Delaware River Basin, Water Years 1960–2010

observed data would result in a NSE value of 1.0. The results 

are shown in figure 9. Both methods for selecting a reference 

streamgage produce streamflow estimates in good agreement 

with the observed streamflow; however, those resulting from 

map correlation perform slightly better, as indicated by more 

points falling below the line of equal NSE (fig. 9). Those 

points that fall on the line of equal NSE represent instances 

where both methods for selecting the best streamgage selected 

the same reference streamgage. 

The median NSE values resulting from the use of map 

correlation and the closest gage are 0.85 and 0.83, respectively. The greatest discrepancy between the two methods is 

shown by streamgage 01426000, Oquaga Creek at Deposit, 

N.Y., with a drainage area 67.6 mi2. The use of map correlation resulted in the selection of 01425675, Oquaga Creek near 

North Sanford, N.Y. (drainage area 4.69 mi2) as the most representative reference streamgage with a NSE value of 0.87; the 

use of the closest gage resulted in the selection of 01425500, 

Cold Spring Brook at China, N.Y. (drainage area 1.50 mi2) 

as the most representative reference streamgage with a NSE 

value of -0.27. In this example, the closest gage (01425500) is 

in a neighboring watershed, whereas the streamgage with the 

highest estimated correlation (01425675) is in the headwaters 

of the same watershed. Both streamgages are well outside the 

range of suggested drainage area ratios (Roland and Stuckey, 

2008), however, the other basin characteristics for 01426000 

and 01425675 are similar whereas some of the basin characteristics differ between 01426000 and 01425500 (Appendix 2). 

This difference in basin characteristics, especially percent of 

poorly drained soil, likely contributed to the lower NSE value 

seen with the use of the closest gage.

The transfer of streamflow exceedance probabilities from 

a reference streamgage to an ungaged stream location using 

the QPPQ method relies on the assumption that both locations experience identical exceedance probabilities at identical 

times. Isolated storm events frequently occur that affect one 

subbasin but not other nearby subbasins. This is especially 

true when the ungaged subbasin has a much smaller or larger 

drainage area than the reference streamgage subbasin.

To evaluate how well DRB-SET estimates daily mean 

streamflow, a comparison of observed and estimated daily 

mean streamflows was performed for all the reference 

streamgages within the Delaware River Basin. The reference 

streamgages were run through DRB-SET as ungaged stream 

locations, and the estimated streamflow was compared to the 

observed using NSE (log10) values as a measure of goodness 

of fit. Reference streamgages were selected using the default 

map correlation method. NSE (log10) values ranged from 

0.22 to 0.98 (median of 0.90) for the Upper Delaware River 

Basin and from -0.37 to 0.98 (median of 0.79) for the Lower 

Delaware River Basin (table 5 and fig. 10). The lowest NSE 

value (-0.37) is from 01466500, McDonalds Branch in Byrne 

State Forest, N.J., with a drainage area of 2.34 mi2; the percent 

sand in soil is 86.5 percent, which is the maximum used in the 

overall analysis. The spatial distribution of the NSE values 

determined for each reference streamgage within the Delaware 

River Basin is shown in figure 11. Two of the three remaining 

reference streamgages with NSE values less than or equal to 

zero are located to the west of the Delaware Bay in Delaware 

and have small drainage areas (fig. 11). The final reference 

streamgage with an NSE value less than or equal to zero is 

located in the western part of the basin on the Tulpehocken 

Creek (fig. 11).

Hydrographs and FDCs generated from DRB-SET for 

streamgages 01420500, Beaver Kill at Cooks Falls, N.Y., and 

01464500, Crosswicks Creek at Extonville, N.J., are shown 

in figures 12A and 12B, respectively. Streamgage 01420500 

was associated with reference streamgage 01418500 with an 

estimated streamflow correlation (using map correlation) of 

0.99, and streamgage 01464500 was associated with reference 

streamgage 01401000 with an estimated streamflow correlation (using map correlation) of 0.86 for estimates of daily 

mean flow. While both of these estimated streamflow correlations are fairly high, they represent the best (01420500) and 

worst (01464500) estimated streamflow correlations for reference streamgages with measured streamflow for WY 1960–

2010. The low-flow period from WY 1998 to 2002 is shown 

in the hydrographs in figure 12. Although both hydrographs 

show good general fit between the estimated and observed 

streamflows, the hydrograph for 01464500 shows more variance, which is reflected in the lower NSE (log10) value of 0.59 

in comparison to the NSE (log10) value of 0.98 associated with 

01420500. 

1.50

1.00

0.50

0.00

-0.50

-1.00

-1.00 -0.50 0.00 0.50 1.00 1.50

Closest gage

performs better

Map correlation

performs better

Line of equal

Nash-Sutcliffe

efficiency

Nash-Sutcliffe efficiency value (log )

using map correlation

10

Nash-Sutcliffe efficiency value (log )

using closest gage 10

Figure 9. Nash-Sutcliffe efficiency values determined using the 

closest streamgage and map correlation in the Delaware River 

Basin Streamflow Estimator Tool.
Accuracy and Limitations of Estimated Streamflow 23

Table 5. Nash-Sutcliffe efficiency values between observed and estimated daily mean streamflows in the Delaware River Basin.

Location Number of 

streamgages

Minimum NashSutcliffe 

efficiency value 

(log10)

Maximum NashSutcliffe 

efficiency value 

(log10)

Mean NashSutcliffe 

efficiency value 

(log10)

Median NashSutcliffe 

efficiency value 

(log10)

Upper Delaware River Basin 45 0.22 0.98 0.86 0.90

Lower Delaware River Basin 41 -0.37 0.98 0.72 0.79

Entire Delaware River Basin 86 -0.37 0.98 0.78 0.86

Outside Delaware River Basin 24 0.49 0.96 0.80 0.83

x

o

o

x

o

o

1.0

0.8

0.6

0.4

0.2

0.0

-0.2

-0.4

Nash-Sutcliffe efficiency values (log )

Upper Delaware

River Basin

Lower Delaware

River Basin

EXPLANATION

x

x

o

o

Upper adjacent

75th percentile

50th percentile

25th percentile

Lower adjacent

Lower outside

Lower detached

Upper detached

Upper outside

Interquartile

(median) range

10

Figure 10. Distribution of Nash-Sutcliffe efficiency values 

between observed and estimated daily mean streamflows in the 

Upper and Lower Delaware River Basin.
24 Estimation of Daily Mean Streamflow for Ungaged Stream Locations in the Delaware River Basin, Water Years 1960–2010

#

#

#

#

##

#

##

# # # #

##

#

####

#

#

#

#

#

#

# # #

# # #

##

#

#

#

#

#

#

# # #

#

#

#

#

#

##

#

#

# #

#

#

##

#

#

##

#

#

# #

# #

#

#

#

#

##

# #

#

#

#

#

#

#

#

#

Delaware River

77° 76° 75° 74°

42°

41°

40°

39°

EXPLANATION

# U.S. Geological Survey streamgage location

Major rivers and streams

Delaware River Basin boundary

Nash-Sutcliffe efficiency values (log10)

-0.371 – 0.000

0.001 – 0.500

0.501 – 0.799

0.800 – 0.897

0.898 – 0.984

0 10 20 MILES

0 10 20 KILOMETERS

NEW YORK

PENNSYLVANIA

MARYLAND

DELAWARE

NEW JERSEY

DISTRICT OF

COLUMBIA

MASSACHUSETTS CONNECTICUT

Delaware 

Bay Chesapeake Bay

Atlantic Ocean

Base modified from U.S. Geological Survey 1:100,000-scale 

and 1:250,000-scale digital data

Lower 

Delaware 

River 

Basin

Upper 

Delaware 

River Basin

Tulpehocken Creek

Figure 11. Spatial distribution of Nash-Sutcliffe efficiency values for reference streamgage basins in the 

Delaware River Basin.
Accuracy and Limitations of Estimated Streamflow 25

1

10

100

1,000

10,000

100,000

1998 1999 2000 2001 2002

Streamflow, in cubic feet per second

Year

Observed streamflow

Estimated streamflow

EXPLANATION

1

10

100

1,000

10,000

100,000

A. 1420500 Beaver Kill at Cooks Falls, N.Y.

B. 1464500 Crosswicks Creek at Extonville, N.J.

1 10 100

Estimated streamflow,

in cubic feet per second 

Nash-Sutcliffe

efficiency = 0.98 

1,000 10,000 100,000

1

10

100

1,000

10,000

1 10 100

Estimated streamflow,

in cubic feet per second 

1,000 10,000

1

10

100

1,000

10,000

1998

Streamflow, in cubic feet per second

1999 2000 2001 2002

Year

Nash-Sutcliffe

efficiency = 0.59

Observed streamflow

Estimated streamflow

EXPLANATION

Observed streamflow, in cubic feet per second

Observed streamflow, in cubic feet per second

Figure 12. Estimated and observed daily mean streamflows for U.S. Geological Survey streamgages A, 01420500, Beaver Kill at 

Cooks Falls, New York, water years 1999–2002, and B, 01464500, Crosswicks Creek at Extonville, New Jersey, water years 1999–2002.
26 Estimation of Daily Mean Streamflow for Ungaged Stream Locations in the Delaware River Basin, Water Years 1960–2010

Summary

The Delaware River Basin encompasses more than 

13,500 square miles in parts of four states—New York, New 

Jersey, Pennsylvania, and Delaware—and has a population 

of approximately 8.3 million. In the upper parts of the basin, 

concerns over the effects of new natural gas development and 

the freshwater requirements for a recently discovered endangered mussel species have added new complexities to water 

management in the basin. Hydrologic and ecological data can 

be directly related to provide the basis for understanding the 

flow needs of aquatic species found in the tributaries of the 

Delaware River Basin. Providing the data and tools to understand and define flow-alteration ecological-response relations 

will assist water-resource managers and policy makers in 

meeting the ecological flow needs of aquatic species in the 

Delaware River Basin. 

The U.S. Geological Survey, through the National Water 

Census, has developed a tool to estimate streamflow at a daily 

time step for ungaged stream locations in the Delaware River 

Basin. The Delaware River Basin Streamflow Estimator Tool 

(DRB-SET) is a tool for simulating streamflow at a daily time 

step for an ungaged stream location in the Delaware River 

Basin for water years (WY) 1960–2010. Daily mean streamflow is estimated using the QPPQ method, which equates 

streamflow expressed as a percentile from the flow-duration 

curve (FDC) for a particular day at an ungaged stream location with the percentile from a FDC for the same day at a 

hydrologically similar location where streamflow is observed. 

Parameter-based regression equations were developed for 22 

exceedance probabilities from the FDC for ungaged stream 

locations in the Delaware River Basin. Prediction errors for 

the 22 regression estimates ranged from 11 to 79 percent. 

Streamflow data from continuous-record streamgages were 

used to develop correlation maps of the predicted correlation 

of streamflow between an ungaged stream location and a 

reference streamgage. Water use data from 2010 were used to 

adjust the baseline daily mean streamflow generated from the 

QPPQ method at ungaged stream locations in the Delaware 

River Basin to reflect non-baseline conditions which may be 

affected by anthropogenic water usage. 

To evaluate the effectiveness of the overall QPPQ method 

contained within DRB-SET, a comparison of observed and 

estimated daily mean streamflows was performed for 109 

reference streamgages in and near the Delaware River Basin. 

The Nash-Sutcliffe efficiency (NSE) values were computed 

as a measure of goodness of fit; a maximum value of 1.0 

would indicate a perfect match of modeled and observed data. 

The NSE values (using log10 streamflow values) ranged from 

0.22 to 0.98 (median of 0.90) for the Upper Delaware River 

Basin and from -0.37 to 0.98 (median of 0.79) for the Lower 

Delaware River Basin.

The accuracy of estimated daily streamflows for 

ungaged stream locations is dependent on the uncertainties 

associated with the multiple steps that compose the overall 

process. These steps include measurement of streamflow 

at reference streamgages, streamflow record extension at 

reference streamgages, estimation of the FDC for an ungaged 

stream location on the basis of regression equations and 

basin characteristics, selection of a reference streamgage 

using the map correlation method, and transfer of exceedance 

probabilities from reference streamgage to the ungaged stream 

location.

Acknowledgments

The author thanks Martyn Smith of the U.S. Geological 

Survey (USGS) for providing assistance with the geographic 

information systems and StreamStats that was necessary for 

the completion of the project. The author also thanks Stacey 

Archfield, USGS, for her assistance in running the map 

correlations and her expertise in the QPPQ process. Other 

USGS colleagues also made substantive contributions: Jeffrey 

Fischer provided helpful feedback pertaining to the overall 

National Water Census and technical reviews were provided 

by Thomas Over and Mark Roland.

References Cited

Alley, W.M., Evenson, E.J., Barber, N.L., Bruce, B.W., 

Dennehy, K.F., Freeman, M.C., Freeman, W.O., Fischer, 

J.M., Hughes, W.B., Kennen, J.G., Kiang, J.E., Maloney, 

K.O., Musgrove, MaryLynn, Ralston, Barbara, Tessler, 

Steven, and Verdin J.P., 2013, Progress toward establishing 

a national assessment of water availability and use: U.S. 

Geological Survey Circular 1384, 34 p. [Also available at 

http://pubs.usgs.gov/circ/1384.]

Archfield, S.A., Steeves, P.A., Guthrie, J.D., and Ries III, 

K.G., 2012, A web-based software tool to estimate unaltered daily streamflow at ungauged rivers, Geoscience 

Model Development. Discussions, no. 5, p. 2,503–2,526, 

DOI:10.5194/gmdd-5-2503-2012, 2012.

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

method: Selection of a reference streamgage to 

estimate daily streamflow at ungaged catchments: 

Water Resources Research, no. 46, no. 10, W10513, 

DOI:10.1029/2009WR008481. 
References Cited 27

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, 

http://pubs.usgs.gov/sir/2009/5227/.

Daly, C., Neilson, R.P., and Phillips, D.L., 1994, A statisticaltopographic model for mapping climatological precipitation over mountainous terrain: Journal of Applied 

Meteorology, v. 33, no. 2, p. 140–158, DOI: http://dx.doi.

org/10.1175/1520-0450(1994)033%3C0140:ASTMFM%3E

2.0.CO;2.

Delaware River Basin Commission, 2013, Delaware River 

Basin Commission Annual Report, 28 p., http://www.

nj.gov/drbc/library/documents/2013AR.pdf. 

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].

Fischer, J.M., Riva-Murray, Karen, Hickman, R.E., Chichester, 

D.C., Brightbill, R.A., Romanok, K.M., and Bilger, 

M.D., 2004, Water quality in the Delaware River Basin, 

Pennsylvania, New Jersey, New York, and Delaware, 

1998–2001: U.S. Geological Survey Circular 1227, 39 p., 

http://pubs.usgs.gov/circ/2004/1227/pdf/circular1227.pdf.

Fry, J., Xian, G., Jin, S., Dewitz, J., Homer, C., Yang, L., 

Barnes, C., Herold, N., and Wickham, J., 2011, Completion 

of the 2006 National Land Cover Database for the 

Conterminous United States: Photogrammetric Engineering 

and Remote Sensing, v. 77, no. 9, p. 858–864, http://www.

mrlc.gov/nlcd2006.php. 

Gazoorian, C.L., 2015, Estimation of unaltered daily mean 

streamflow at ungaged streams of New York, excluding 

Long Island, water years 1961–2010: U.S. Geological 

Survey Scientific Investigations Report 2014–5220, 29 p., 

http://dx.doi.org/10.3133/sir20145220.

Gesch, Dean, Oimoen, Michael, Greenlee, Susan, Nelson, 

Charles, Steuck, Michael, and Tyler, Dean, 2002, The 

National Elevation Dataset: Photogrammetric Engineering 

and Remote Sensing, v. 68, no. 1, http://www.asprs.org/a/

publications/pers/2002journal/january/highlight.html.

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 appendixes, http://pubs.usgs.gov/

of/2008/1362/.

Helsel, D.R., and Hirsch, R.M., 2002, Statistical methods in 

water resources: U.S. Geological Survey Techniques of 

Water-Resources Investigations, book 4, chap. A3, 522 p. 

[Also available at http://pubs.usgs.gov/twri/twri4a3/.]

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

extension techniques: Water Resources Research, v. 18, 

no. 4, p. 1,081–1,088, DOI: 10.1029/WR018i004p01081.

Hughes, D.A., and Smakhtin, V.Y., 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, 

DOI:10.1080/02626669609491555.

Hutson, S.S., Linsey, K.S., Ludlow, R.A., Reyes, Betzaida, 

and Shourds, J.L., in press, Estimated use of water in the 

Delaware River Basin in Delaware, New Jersey, New York, 

Pennsylvania, 2010: U.S. Geological Survey Scientific 

Investigations Report 2015–5142. 

Isaaks, E.H., and Srivastava, R.M., 1989, An introduction 

to applied geostatistics: New York and Oxford, Oxford 

University Press, 561 p.

Jenner, C.B., and Lins, H.F., 1991, Climatic atlas of the 

Delaware River Basin: U.S. Geological Survey Professional 

Paper 1392, 127 p., https://pubs.er.usgs.gov/publication/

pp1392.

Lellis, W.A. 2001, Freshwater Mussel Survey of the Delaware 

Scenic and Recreational River, Qualitative Survey 2000: 

Report to the National Park Service, February 20, 2001, 6 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, DOI: 10.1623/

hysj.53.4.706. 

Ries, K.G., III, comp., 2007, The national streamflow statistics program: A computer program for estimating streamflow statistics for ungaged sites: U.S. Geological Survey 

Techniques and Methods 4-A6, 37 p., http://pubs.usgs.gov/

tm/2006/tm4a6/.

Ries, K.G., III, Guthrie, J.D., Rea, A.H., Steeves, P.A., and 

Stewart, D.W., 2008, StreamStats: A water resources web 

application: U.S. Geological Survey Fact Sheet 2008–3067, 

6 p., http://pubs.usgs.gov/fs/2008/3067/.

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

for estimating flood flows at selected recurrence intervals 

for ungaged streams in Pennsylvania: U.S. Geological 

Survey Scientific Investigations Report 2008–5102, 57 p., 

http://pubs.usgs.gov/sir/2008/5102/.
28 Estimation of Daily Mean Streamflow for Ungaged Stream Locations in the Delaware River Basin, Water Years 1960–2010

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

records: U.S. Geological Survey Water-Supply Paper 1541–

C, p. 67–100, http://pubs.usgs.gov/wsp/1541c/report.pdf. 

Shu, Chang, and Ourda, T.B.M.J., 2012, Improved 

methods for daily streamflow estimates at ungauged 

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

DOI:10.1029/2011WR011501.

Smakhtin, V.Y., 1999, Generation of natural daily flow 

time series in regulated rivers using a nonlinear spatial 

interpolation technique: Regulated Rivers Research and 

Management, v.15, 12 p., DOI:10.1002/(SICI)1099-

1646(199907/08)15:4<311::AID-RRR544>3.0.CO;2-W.

Smakhtin, V.Y. and Masse, B., 2000, Continuous daily 

hydrograph simulation using duration curves of a 

precipitation index: Hydrological Processes, v. 14, 

no. 6, p. 1,083–1,100, DOI: 10.1002/(SICI)1099-

1085(20000430)14:6<1083::AID-HYP998>3.0.CO;2-2. 

Soil Survey Staff, Natural Resources Conservation Service, 

United States Department of Agriculture, Web Soil Survey, 

accessed December 21, 2015, at http://websoilsurvey.nrcs.

usda.gov/.

Stuckey, M.H., Koerkle, E.H., and Ulrich, J.E., 2014, 

Estimation of baseline daily mean streamflows for ungaged 

locations on Pennsylvania streams, water years 1960–2008 

(ver 1.1, August 2014): U.S. Geological Survey Scientific 

Investigations Report 2012–5142, 61 p., http://pubs.usgs.

gov/sir/2012/5142.

Stuckey, M.H., and Ulrich, J.E., in press, User’s Guide for 

the Delaware River Basin Streamflow Estimator Tool 

(DRB-SET): U.S. Geological Survey Open-File Report 

2015–1192.

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

Packages: Palo Alto, Calif., 77 p.
Appendixes 1–3 29

Appendixes 1–3
30 Estimation of Daily Mean Streamflow for Ungaged Stream Locations in the Delaware River Basin, Water Years 1960–2010 Appendix 1. Reference streamgages with record extension techniques applied.—Continued [USGS, U.S. Geological Survey] USGS streamgage number Name Portion of record extended Index station 1 (station number) Corre- lation coef- ficient Index station 2 (station number) Corre- lation coef- ficient Index station 3 (station number) Corre- lation coef- ficient 01362200 Esopus Creek at Allaben, N.Y. Oct. 1959–Sep. 1963 East Branch Delaware River at Margaret- ville, N.Y. (01413500) 0.961 01365500 Chestnut Creek at Grahamsville, N.Y. Apr. 1987–Sep. 1998 Roundout Creek near Lowes Corners, N.Y. (01365000) 0.945 01366650 Sandburg Creek at Ellenville, N.Y. Oct. 1977–Sep. 2010 Roundout Creek near Lowes Corners, N.Y. (01365000) 0.919 01368500 Rutgers Creek at Gardnerville, N.Y. Oct. 1968–Sep. 2010 Flat Brook near Flatbrookville, N.J. (01440000) 0.941 01369000 Pochuck Creek near Pine Island, N.Y. Oct. 1977–Sep. 2010 Paulins Kill at Blairstown, N.J. (01443500) 0.924 01401650 Pike Run at Belle Mead, N.J. Oct. 1959–June 1980 Stony Brook at Princeton, N.J. (01401000) 0.897 01403540 Stony Brook at Watchung, N.J. Oct. 1959–Sep. 1974 Stony Brook at Princeton, N.J. (01401000) 0.873 01411300 Tuckahoe River at Head of River, N.J. Oct 1959-Dec 1969 Great Egg Harbor River at Folsom, N.J. (01411300) 0.880 01418500 Beaver Kill at Craigie Clair, N.Y. Oct. 1970–Sep. 2010 Beaver Kill at Cooks Falls, N.Y. (01420500) 0.985 01419500 Willowemoc Creek near Livingston Manor, N.Y. Oct. 1970–Sep. 2010 Beaver Kill at Cooks Falls, N.Y. (01420500) 0.984 01420000 Little Beaver Kill near Livingston Manor, N.Y. Oct. 1981–Sep. 2010 Beaver Kill at Cooks Falls, N.Y. (01420500) 0.964 01421614 Town Brook Tributary southeast of Hobart, N.Y. Oct. 1959–Sep. 1998; Nov. 2009–Sep. 2010 West Branch Delaware River at Walton, N.Y. (01423000) 0.915 01421618 Town Brook Tributary southeast of Hobart, N.Y. Oct. 1959–Sep. 1997 East Branch Delaware River at Margaret- ville, N.Y. (01413500) 0.942 01421900 West Branch Delaware River upstream from Delhi, N.Y. Sep. 1970–Dec. 1996 West Branch Delaware River at Walton, N.Y. (01423000) 0.988 01422389 Coulter Brook near Bovina Center, N.Y. Oct. 1959–Sep. 1997; Oct. 2009–Oct. 2010 West Branch Delaware River at Walton, N.Y. (01423000) 0.914 01422500 Little Delaware River near Delhi, N.Y. Oct. 1970–Jan. 1997 West Branch Delaware River at Walton, N.Y. (01423000) 0.977 01422738 Wolf Creek at Mundale, N.Y. Oct. 1959–Sep. 1998; June 2009–Oct. 2010 West Branch Delaware River at Walton, N.Y. (01423000) 0.931 01422747 East Brook east of Walton, N.Y. Oct. 1959–Sep. 1998 West Branch Delaware River at Walton, N.Y. (01423000) 0.966 01423500 Dryden Brook near Granton, N.Y. June 1967–Sep. 2010 West Branch Delaware River at Walton, N.Y. (01423000) 0.956 0142400103 Trout Creek near Trout Creek, N.Y. July 1967–Nov. 1996 West Branch Delaware River at Walton, N.Y. (01423000) 0.959

01424108 Sherruck Brook Tributary near Trout Creek, N.Y. Oct. 1959–Sep. 1997; Sep. 2007–Sep. 2010 West Branch Delaware River at Walton, N.Y. (01423000) 0.937
Appendixes 1–3 31

Appendix 1. Reference streamgages with record extension techniques applied.—Continued[USGS, U.S. Geological Survey]

USGS 

streamgage 

number

Name Portion of record extended Index station 1 (station number)

Correlation 

coefficient

Index station 2 

(station number)

Correlation 

coefficient

Index station 3 

(station number)

Correlation 

coefficient

01425500 Cold Spring Brook at China, N.Y. Oct. 1968–Sep. 2010 Susquehanna River at Conklin, N.Y. (01503000) 0.917

01425675 Oquaga Creek near North Sanford, N.Y. Oct. 1959–Sep. 1969; Oct. 1981–Sep. 2010 Susquehanna River at Conklin, N.Y. (01503000) 0.86901426000 Oquaga Creek at Deposit, N.Y. Oct. 1973–Sep. 2010 West Branch Delaware River at Walton, N.Y. (01423000) 0.92401427500 Callicoon Creek at Callicoon, N.Y. Oct. 1982–Sep. 2010 Beaver Kill at Cooks Falls, N.Y. (0142500) 0.94301428000 Tenmile River at Tusten, N.Y. Oct. 1973–Sep. 2010 Bush Kill at Shoemakers, Pa. (01439500) 0.91301428750 West Branch Lackawaxen River near Aldenville, Pa. Oct. 1959–Sep. 1987 Tunkhannock Creek near Tunkhannock, Pa. (01534000) 0.92701431000 Middle Creek near Hawley, Pa. Sep. 1960–Sep. 2010 Lehigh River at Stoddartsville, Pa. (01447500) 0.92001445000 Pequest River at Huntsville, N.J. Oct. 1962–Sept. 2002 Flat Brook near Flatbrookville, N.J. (01440000) 0.92001447720 Tobyhanna Creek near Blakeslee, Pa. Oct. 1959–Sep. 1960; Oct. 1985–Sep. 2010 Lehigh River at Stoddartsville, Pa. (01447500) 0.95001448500 Dilldown Creek near Long Pond, Pa. Oct. 1996–Sep. 2010 Brodhead Creek at Minisink Hills, Pa. (01442500) 0.926 Pohopoco Creek at Kres- geville, Pa. (01449360) 0.924

01449360 Pohopoco Creek at Kresgeville, Pa. Oct. 1959–Sep. 1966 Aquashicola Creek at Palmerton, Pa. (01450500) 0.958

01451800 Jordan Creek near Schnecksville, Pa. Oct. 1959–Jan. 1966 Jordan Creek at Allentown, Pa. (01452000) 0.97501459500 Tohickon Creek near Pipersville, Pa. Dec. 1973–Sep. 2010 Skippack Creek near Collegeville, Pa. (01473120) 0.897 Jordan Creek near Schnecks- ville, Pa. (01451800) 0.872

01464907 Little Neshaminy Creek at Valley Road, Pa. Oct. 1959–Nov. 1998 Pennypack Creek at Lower Rhawn St, Philadelphia, Pa. (01467048) 0.902 French Creek near Phoenix- ville, Pa. (01472157) 0.87101465798 Poquessing Creek at Grant Ave. at Philadelphia, Pa. Oct. 1959–Jul. 1965 Shellpot Creek at Wilmington, Del. (01477800) 0.821

01467048 PennyPack Creek at Lower Rhawn Street Bridge, Philadelphia, Pa. Oct. 1959–Sep. 1965 Tohickon Creek near Pipersville, Pa. (01459500) 0.74801467086 Tacony Creek at County Line, Philadelphia, Pa. Oct. 1959–July 1965 Shellpot Creek at Wilmington, Del. (01477800) 0.82101467150 Cooper River at Haddonfield, N.J. Oct. 1959–Sep. 1963 Christina River at Coochs Bridge, Del. (01478000) 0.75301468500 Schuylkill River at Landingville, Pa. Oct. 1959–Sep. 1963; Oct. 1965–July 1973 Schuylkill River at Berne, Pa. (01470500) 0.97501470756 Maiden Creek at Virginville, Pa. Oct. 1960–Jan. 1973; Oct. 1995–Sep. 2010 Jordan Creek at Allentown, Pa. (01452000) 0.955
32 Estimation of Daily Mean Streamflow for Ungaged Stream Locations in the Delaware River Basin, Water Years 1960–2010 Appendix 1. Reference streamgages with record extension techniques applied.—Continued [USGS, U.S. Geological Survey] USGS streamgage number Name Portion of record extended Index station 1 (station number) Corre- lation coef- ficient Index station 2 (station number) Corre- lation coef- ficient Index station 3 (station number) Corre- lation coef- ficient 01470779 Tulpehocken Creek near Bernville, Pa. Oct. 1959–Nov. 1974 Tulpehocken Creek near Reading, Pa. (01471000) 0.849 01471000 Tulpehocken Creek near Reading, Pa. Apr. 1979–Sep. 2010 Schuylkill River at Berne, Pa. (01470500) 0.853 01471980 Manatawny Creek near Pottstown, Pa. Oct. 1959–July 1974; Oct. 2004–Sep. 2010 West Branch Perkiomen Creek at Hillegass, Pa. (01472199) 0.958 Jordan Creek at Allentown, Pa. (01452000) 0.863 01472000 Schuylkill River at Pottstown, Pa. Apr. 1979–Sep. 2010 Schuylkill River at Berne, Pa. (01470500) 0.964 01472157 French Creek near Phoenixville, Pa. Oct. 1959–Sep. 1968 Brandywine Creek at Chadds Ford, Pa. (01481000) 0.948 Tohickon Creek near Pipers- ville, Pa. (01459500) 0.846 01472174 Pickering Creek near Chester Springs, Pa. Oct. 1959–Dec. 1966; Oct. 1983–Sep. 2010 Little Lehigh Creek near Allentown, Pa. (01451500) 0.910 French Creek near Phoenix- ville, Pa. (01472157) 0.909 Brandywine Creek at Chadds Ford, Pa. (01481000) 0.771 01472198 Perkiomen Creek at East Greenville, Pa. Oct. 1959–Aug. 1981 Jordan Creek at Allentown, Pa. (01452000) 0.917 French Creek near Phoenix- ville, Pa. (01472157) 0.794 01472199 West Branch Perkiomen Creek at Hil- legass, Pa. Oct. 1959–Sep. 1981 Manatawny Creek near Pottstown, Pa. (01471980) 0.958 Jordan Creek at Allentown, Pa. (01452000) 0.874 01473120 Skippack Creek near Collegeville, Pa. Oct. 1959–Apr. 1966; Oct. 1994–Sep. 2010 French Creek near Phoenixville, Pa. (01472157) 0.855 Jordan Creek at Allentown, Pa. (01452000) 0.794 01475510 Darby Creek near Darby, Pa. Oct. 1959–Jan. 1964; Oct. 1990–Sep. 2010 Crum Creek near Newtown Square, Pa. (01475850) 0.906 Tohickon Creek near Pipers- ville, Pa. (01459500) 0.749 01475530 Cobbs Creek at U.S. Hghwy No. 1 at Philadelphia, Pa. Oct. 1959–Sep. 1964 Shellpot Creek at Wilmington, Del. (01477800) 0.841 01475850 Crum Creek near Newtown Square, Pa. Oct. 1959–Sep. 1981 Darby Creek near Darby, Pa. (01475510) 0.906 West Branch Brandywine Creek near Honey Brook, Pa. (01480300) 0.875 Little Lehigh Creek near Allentown, Pa. (01451500) 0.905 01477120 Raccoon Creek near Swedesboro, N.J. Oct. 1959–Mar. 1966 Red Clay Creek at Wooddale, Del. (01480000) 0.858 01479820 Red Clay Creek near Kennett Square, Pa. Oct. 1959–Dec. 1987 Red Clay Creek at Wooddale, Del. (01480000) 0.951 01480015 Red Clay Creek near Stanton, Del. Oct. 1959–Sep.1988 Red Clay Creek at Wooddale, Del. (01480000) 0.980 01480100 Little Mill Creek at Elsmere, Del. Oct. 1959–Sep.1963; Oct. 1980–Sep. 2010 Shellpot Creek at Wilmington, Del. (01477800) 0.893 01480300 West Branch Brandywine Creek near Honey Brook, Pa. Oct. 1959–May 1960 Tohickon Creek near Pipersville, Pa. (01459500) 0.818 01480675 Marsh Creek near Glenmoore, Pa. Oct. 1959–July 1966 Brandywine Creek at Chadds Ford, Pa. (01481000) 0.934 Tohickon Creek near Pipers- ville, Pa. (01459500) 0.855
Appendixes 1–3 33

Appendix 1. Reference streamgages with record extension techniques applied.—Continued[USGS, U.S. Geological Survey]

USGS 

streamgage 

number

Name Portion of record extended Index station 1 (station number)

Correlation 

coefficient

Index station 2 

(station number)

Correlation 

coefficient

Index station 3 

(station number)

Correlation 

coefficient

01481000 Brandywine Creek at Chadds Ford, Pa. Oct. 1959–Sep. 1962; Oct. 1974–Sep. 2010 Schuylkill River at Pottstown, Pa. (01472000) 0.945 French Creek near Phoenix- ville, Pa. (01472157) 0.85101482500 Salem River at Woodstown, N.J. Feb. 1985–June 1989; Oct. 1990–Sep. 2002 White Clay Creek near Newark, Del. (01479000) 0.808

01483000 Alloway Creek at Alloway, N.J. Oct. 1972–Sep. 2010 Crosswicks Creek at Extonville, N.J. (01464500) 0.81601483500 Leipsic River near Cheswold, Del. Oct. 1957–Sep. 2010 Codorus Creek at Spring Grove, Pa. (01574500) 0.76501484000 Murderkill River near Felton, Del. Jan. 2009–Sep. 2010 Nanticoke River near Bridgeville, Del. (01487000) 0.88401484270 Beaverdam Creek near Milton, Del. Oct. 1959–Apr.1971; Oct. 2005–Sep. 2010 Nanticoke River near Bridgeville, Del. (01487000) 0.84601484300 Sowbridge Branch near Milton, Del. Oct. 1978–Sep. 2010 Nanticoke River near Bridgeville, Del. (01487000) 0.86201484500 Stockley Branch at Stockley, Del. Oct. 2004–Sep. 2010 Nanticoke River near Bridgeville, Del. (01487000) 0.86101488500 Marshyhope Creek near Adamsville, Del. Jan. 2003–Sep. 2004 Nanticoke River near Bridgeville, Del. (01487000) 0.89701498500 Charlotte Creek at West Davenport, N.Y. Oct. 1975–Sep. 2010 West Branch Delaware River at Walton, N.Y. (01423000) 0.95801499000 Otego Creek near Oneonta, N.Y. Oct. 1968–Sep. 2010 Susquehanna River at Conklin, N.Y. (01503000) 0.96501533950 South Branch Tunkhannock Creek near Montdale, Pa. Oct. 1959–Aug. 1960; Oct. 1978–Sep. 2010 Tunkhannock Creek near Tunkhannock, Pa. (01534000) 0.94101576754 Conestoga River at Conestoga, Pa. Oct. 1959–Sep. 1984 French Creek near Phoenixville, Pa. (01472157) 0.901 Schuylkill River at Berne, Pa. (01470500) 0.859

01578400 Bowery Run near Quarryville, Pa. Oct. 1959–Sep. 1962; Apr. 1981–Sep. 2010 West Branch Brandywine Creek near Honey Brook, Pa. (01480300) 0.834 Codorus Creek at Spring Grove, Pa. (01574500) 0.742
34 Estimation of Daily Mean Streamflow for Ungaged Stream Locations in the Delaware River Basin, Water Years 1960–2010

Appendix 2. Basin characteristics used in the development of flow-duration exceedance probability regression equations for the 

Delaware River Basin.—Continued

[USGS, U.S. Geological Survey; mean annual precipitation, 1981–2010; mean winter precipitation, December–February, 1981–2010]

USGS

streamgage 

number

Latitude at 

outlet 

(decimal 

degrees)

Drainage area 

(square miles)

Mean annual 

precipitation 

(inches)

Mean winter 

precipitation 

(inches)

Poorly drained 

soil 

(percent)

Sand in soil 

(percent)

Saturated 

hydraulic 

conductivity 

(micrometers 

per second)

01350000 42.319502 237 49.8 3.32 1.58 42.5 9.58

01362200 42.117021 63.7 51.1 3.46 1.52 37.9 11.0

01365000 41.866263 38.3 58.1 3.99 0.67 36.7 8.68

01365500 41.845049 21.1 50.8 3.42 2.83 49.1 11.3

01366650 41.714287 52.8 49.2 3.41 4.09 44.7 15.4

01368500 41.343568 58.8 46.5 3.08 4.64 33.8 11.5

01369000 41.275675 98.0 48.0 3.30 3.69 48.0 29.8

01401000 40.333054 44.5 48.7 3.41 9.01 25.2 9.01

01401650 40.468048 5.29 48.0 3.36 8.21 27.3 13.8

01403540 40.636665 5.49 48.9 3.46 6.64 35.8 8.55

01411000 39.595005 57.0 46.6 3.42 14.6 81.3 64.9

01411300 39.306946 30.8 45.1 3.44 1.66 77.8 55.5

01411500 39.495552 111 46.2 3.38 5.12 76.5 53.2

01413500 42.144651 163 46.5 2.94 1.74 39.0 9.77

01414500 42.106310 25.1 48.5 3.14 1.15 37.6 9.14

01415000 42.119723 33.1 45.5 2.90 2.92 38.4 9.16

01418500 41.963074 82.0 51.5 3.48 0.92 40.9 9.54

01419500 41.903374 62.6 53.8 3.72 1.75 48.8 8.69

01420000 41.872815 20.4 52.1 3.57 1.71 48.0 8.52

01420500 41.946577 242 51.6 3.53 1.24 44.6 9.41

01421614 42.349527 0.76 45.9 2.88 0.00 37.0 6.22

01421618 42.361193 14.3 44.7 2.82 1.06 39.7 7.01

01421900 42.280412 134 43.6 2.74 3.17 40.3 11.6

01422389 42.238697 0.76 46.2 2.91 0.00 36.6 6.99

01422500 42.252488 49.8 45.0 2.88 2.44 38.9 7.98

01422738 42.259529 0.61 46.9 3.07 0.00 39.2 4.72

01422747 42.172863 24.7 47.7 3.13 1.77 38.2 8.60

01423000 42.166344 332 45.3 2.91 2.29 39.4 10.6

01423500 42.122030 8.12 48.3 3.20 3.03 35.4 7.53

0142400103 42.173611 20.2 46.2 3.01 1.40 36.5 8.23

01424108 42.187861 1.26 46.1 3.01 0.00 34.9 6.81

01425500 42.161164 1.50 46.1 3.01 0.90 34.9 5.66

01425675 42.174527 4.69 45.7 2.98 2.97 32.1 6.16

01426000 42.058816 67.6 45.3 2.98 3.19 31.7 7.16

01427500 41.760757 110 47.7 3.27 1.96 44.6 8.98

01428000 41.564229 45.7 45.1 3.07 1.97 44.8 8.27

01428750 41.674440 40.6 47.6 3.19 2.28 36.2 7.25

01431000 41.484720 78.8 45.3 3.07 3.26 35.5 7.01

01435000 41.890095 66.7 59.2 4.15 3.08 38.9 9.66

01439500 41.088060 117 48.5 3.35 3.38 53.1 10.8
Appendixes 1–3 35

Appendix 2. Basin characteristics used in the development of flow-duration exceedance probability regression equations for the 

Delaware River Basin.—Continued

[USGS, U.S. Geological Survey; mean annual precipitation, 1981–2010; mean winter precipitation, December–February, 1981–2010]

USGS

streamgage 

number

Latitude at 

outlet 

(decimal 

degrees)

Drainage area 

(square miles)

Mean annual 

precipitation 

(inches)

Mean winter 

precipitation 

(inches)

Poorly drained 

soil 

(percent)

Sand in soil 

(percent)

Saturated 

hydraulic 

conductivity 

(micrometers 

per second)

01440000 41.106667 65.1 47.4 3.21 0.10 57.0 34.5

01440400 41.084720 67.5 50.5 3.52 4.06 41.6 9.74

01442500 40.998610 261 51.5 3.64 4.42 40.4 13.0

01443500 40.980835 126 46.8 3.21 0.25 43.0 43.3

01445000 40.981113 31.0 46.7 3.22 0.00 42.8 39.0

01445500 40.830556 106 47.6 3.27 0.26 50.1 47.9

01446000 40.844444 36.6 47.7 3.26 2.79 41.0 43.2

01447500 41.130280 91.8 51.2 3.53 5.24 40.3 9.24

01447720 41.084720 119 54.0 3.85 12.8 40.2 9.44

01448500 41.035560 2.40 57.3 4.29 8.72 40.8 30.6

01449360 40.897500 49.8 51.6 3.69 6.46 36.9 24.9

01450500 40.806110 76.6 49.1 3.43 3.25 36.8 33.0

01451500 40.582220 81.9 46.3 3.23 4.70 27.0 16.5

01451800 40.661670 53.0 48.0 3.36 7.70 32.1 23.0

01452000 40.623060 76.2 47.5 3.33 6.25 31.1 22.0

01452500 40.641110 43.3 46.4 3.24 3.06 25.9 15.4

01459500 40.433610 97.8 48.6 3.47 29.9 24.6 7.85

01464500 40.137497 80.7 46.0 3.32 16.1 73.4 50.6

01464907 40.229170 27.0 47.2 3.33 13.9 17.6 19.0

01465798 40.056940 21.4 47.9 3.40 7.47 29.8 8.70

01466500 39.884724 2.34 45.7 3.37 7.97 86.5 78.1

01467048 40.050000 49.8 47.8 3.38 5.03 26.3 16.4

01467086 40.046390 16.2 47.4 3.38 1.70 17.9 3.52

01467150 39.903056 17.1 47.0 3.45 9.73 70.9 42.0

01468500 40.629170 137 49.7 3.39 2.28 38.4 39.9

01470500 40.522500 358 50.1 3.44 2.78 36.9 35.8

01470756 40.514170 158 47.1 3.26 6.69 31.1 22.6

01470779 40.413330 70.4 44.5 3.11 5.39 22.7 11.8

01471000 40.368890 215 44.8 3.13 7.49 27.6 17.8

01471980 40.272780 85.5 46.9 3.23 12.2 30.1 21.7

01472000 40.241670 1,147 46.9 3.25 5.53 31.8 24.0

01472157 40.151390 59.0 46.3 3.29 10.8 35.2 19.8

01472174 40.089440 5.98 47.6 3.42 9.70 35.5 24.4

01472198 40.393890 37.7 47.5 3.28 11.5 30.2 21.6

01472199 40.373890 23.1 48.2 3.30 19.4 30.2 19.2

01473120 40.164440 53.7 46.6 3.30 2.36 18.1 18.8

01475510 39.928890 37.5 46.4 3.34 4.24 28.3 8.41

01475530 39.974720 4.79 46.6 3.36 1.52 27.2 7.37

01475850 39.976390 15.8 46.6 3.35 10.2 34.9 17.2

01477120 39.740556 26.0 45.7 3.33 9.11 71.3 49.5
36 Estimation of Daily Mean Streamflow for Ungaged Stream Locations in the Delaware River Basin, Water Years 1960–2010

Appendix 2. Basin characteristics used in the development of flow-duration exceedance probability regression equations for the 

Delaware River Basin.—Continued

[USGS, U.S. Geological Survey; mean annual precipitation, 1981–2010; mean winter precipitation, December–February, 1981–2010]

USGS

streamgage 

number

Latitude at 

outlet 

(decimal 

degrees)

Drainage area 

(square miles)

Mean annual 

precipitation 

(inches)

Mean winter 

precipitation 

(inches)

Poorly drained 

soil 

(percent)

Sand in soil 

(percent)

Saturated 

hydraulic 

conductivity 

(micrometers 

per second)

01477800 39.760972 7.32 45.7 3.33 5.06 23.6 5.48

01478000 39.637389 20.9 45.5 3.26 15.4 40.7 15.4

01479000 39.699222 89.1 46.2 3.31 7.82 42.6 14.6

01479820 39.816670 27.6 46.7 3.35 7.29 40.9 17.0

01480000 39.762806 47.3 46.5 3.35 6.61 42.8 15.6

01480015 39.715750 52.5 46.4 3.34 6.93 42.9 15.1

01480100 39.734835 6.74 45.6 3.33 6.64 37.5 11.6

01480300 40.072780 18.5 46.4 3.19 19.6 40.4 13.6

01480675 40.097780 8.54 47.2 3.38 21.8 38.6 23.8

01481000 39.869720 288 47.6 3.40 9.49 41.6 17.4

01482500 39.643333 14.6 45.0 3.26 16.2 50.8 30.0

01483000 39.565278 20.3 44.2 3.20 13.2 53.4 34.5

01483500 39.232889 9.50 43.8 3.19 15.1 65.2 83.4

01484000 38.975946 12.5 43.9 3.24 30.8 67.6 87.2

01484100 38.905778 3.51 44.8 3.35 44.0 71.2 116

01484270 38.761501 6.91 45.5 3.44 6.01 75.5 95.4

01484300 38.814279 7.11 45.1 3.39 2.89 73.4 89.1

01484500 38.638861 4.79 45.4 3.38 25.0 70.3 121

01487000 38.728333 72.3 44.3 3.34 30.0 72.8 113

01488500 38.849694 47.5 44.0 3.26 47.8 66.8 121

01498500 42.445075 167 42.6 2.69 6.31 37.0 11.0

01499000 42.450968 108 43.0 2.84 6.97 36.8 14.3

01503000 42.035553 2,234 43.5 2.84 4.81 35.5 11.8

01533950 41.574720 12.7 45.6 3.00 2.43 34.8 8.46

01534000 41.558330 393 44.0 2.87 2.28 35.9 7.53

01538000 41.059167 42.9 46.0 2.96 4.26 34.1 7.62

01539000 41.078056 272 46.8 3.02 2.60 35.6 15.1

01576754 39.946389 468 44.1 2.97 0.86 25.7 10.0

01578400 39.894722 6.04 45.6 3.19 1.39 32.8 10.2
 Appendixes 1–3 37 Appendix 3. Observed and predicted flow-duration exceedance probability discharges for streamgages used in regression analysis.—Continued [USGS, U.S. Geological Survey; --, flow-duration exceedance probability discharge could not be computed because of insufficient period of record; O, observed; P, predicted] USGS stream- gage number Type Flow-duration exceedance probability discharges (cubic feet per second) P99. 9946 P99. 95 P99 P98 P95 P90 P85 P80 P75 P70 P60 P50 P40 P30 P25 P20 P15 P10 P05 P02 P01 P0. 0054 01350000 O 4.90 5.80 11.0 14.0 21.0 32.0 45.0 61.0 80.0 103 160 230 320 440 520 634 795 1,060 1,660 2,850 4,120 17,460 P 14.5 17.6 20.7 24.2 34.2 50.1 69.3 91.8 119 147 207 286 390 543 618 768 936 1,181 1,651 2,454 3,241 16,705 01362200 O 0.00 3.50 5.50 6.90 10.0 15.0 20.0 27.0 35.0 44.0 62.0 83.0 110 150 173 206 253 328 499 809 1,170 -- P 4.26 5.32 5.63 6.79 9.67 14.2 19.4 25.4 32.4 39.9 56.1 76.4 102 138 159 195 240 311 462 738 1,010 5,560 01365000 O 3.70 4.40 6.60 7.50 10.0 14.0 19.0 24.0 30.0 35.0 47.0 62.0 81.0 104 120 140 170 217 313 505 712 3,450 P 4.13 4.97 6.91 8.11 11.1 15.4 20.4 25.2 30.9 36.4 47.8 61.8 79.2 102 115 139 171 221 329 534 737 4,578 01365500 O 1.80 2.40 3.20 3.60 4.60 6.20 7.70 9.50 11.0 14.0 18.0 24.0 31.0 41.0 47.0 56.0 68.0 86.0 127 205 290 1,695 P 1.12 1.45 2.09 2.52 3.56 5.18 7.02 9.01 11.4 14.0 19.3 25.9 34.0 46.2 52.7 63.0 76.4 97.1 140 218 292 1,624 01366650 O -- -- 7.20 8.20 11.0 15.0 18.0 22.0 27.0 32.0 44.0 56.0 72.0 99.0 120 142 177 232 342 520 665 -- P 3.53 4.50 4.84 5.84 8.23 11.9 16.0 20.6 25.9 31.8 44.1 59.4 78.7 106 121 147 178 228 331 519 702 3,864 01368500 O -- -- 0.60 0.90 1.40 2.40 3.70 5.20 7.40 11.0 19.0 30.0 45.0 70.0 87.0 113 148 210 353 565 772 -- P 2.07 2.71 4.35 5.42 7.73 11.0 14.6 18.7 23.3 28.3 40.2 54.0 71.4 92.9 106 130 161 212 332 560 794 4,575 01369000 O -- 1.63 4.60 5.60 8.30 13.0 21.0 28.0 37.0 47.0 71.0 98.0 132 182 218 260 313 390 540 762 934 -- P 9.02 11.6 12.2 14.4 19.4 26.7 34.6 43.1 52.8 63.0 84.5 111 143 189 211 254 303 378 533 806 1,072 6,199 01401000 O -- -- 0.30 0.62 1.20 2.20 3.40 4.80 6.60 8.90 15.0 23.0 34.0 50.0 61.0 76.0 100 145 268 547 852 5,348 P 1.77 2.26 5.33 6.72 9.27 12.3 15.2 18.2 21.3 24.4 32.7 41.4 51.9 62.0 70.2 85.3 106 144 241 448 676 4,541 01401650 O -- -- -- -- 0.08 0.27 0.47 0.69 0.92 1.20 1.90 2.70 3.80 5.30 6.40 8.00 11.0 16.0 33.0 77.0 125 -- P 0.19 0.27 0.45 0.59 0.85 1.18 1.50 1.82 2.17 2.56 3.56 4.56 5.75 6.93 7.98 9.55 12.0 16.6 29.1 56.7 86.7 580 01403540 O -- 0.09 0.46 0.63 0.89 1.20 1.50 1.70 2.10 2.50 3.50 4.70 6.20 8.20 9.70 11.0 14.0 20.0 35.0 67.0 104 -- P 0.19 0.25 0.57 0.73 1.03 1.42 1.80 2.18 2.61 3.08 4.20 5.36 6.72 8.28 9.45 11.2 13.8 18.5 30.5 55.5 81.3 534 01411000 O 12.3 15.0 23.0 25.0 30.0 36.0 41.0 45.0 50.0 54.0 64.0 73.0 84.0 97.0 105 114 128 148 186 242 288 1,270 P 5.80 7.73 16.0 18.2 22.6 27.7 32.7 36.9 41.6 46.6 55.3 66.6 79.2 102 109 123 138 161 203 277 348 2,166 01411300 O -- 1.79 8.40 10.0 12.0 14.0 16.0 18.0 20.0 22.0 26.0 31.0 38.0 46.0 51.0 58.0 66.0 80.0 106 145 181 -- P 4.57 6.01 14.8 16.6 19.0 21.7 24.1 25.5 27.4 29.7 34.0 38.5 43.1 52.1 54.5 59.6 65.0 74.4 94.1 127 157 1,194 01411500 O 20.0 23.0 40.0 46.0 56.0 67.0 77.0 86.0 95.0 103 122 143 166 192 207 225 248 280 338 419 493 4,270 P 15.3 19.6 51.2 56.6 65.3 75.5 85.2 92.2 100 109 125 144 165 204 214 239 262 299 370 489 602 4,251 01413500 O 6.10 7.50 12.0 15.0 21.0 31.0 44.0 59.0 75.0 91.0 130 180 241 325 383 456 556 709 1,030 1,640 2,260 14,770 P 5.56 7.10 10.3 12.5 18.0 26.7 36.9 49.2 63.8 80.2 116 162 223 308 353 439 539 691 1,007 1,559 2,102 10,854 01414500 O 1.20 1.50 2.50 3.00 4.20 6.20 8.60 11.0 14.0 17.0 24.0 33.0 44.0 58.0 68.0 80.0 96.0 122 176 285 410 2,000 P 0.88 1.16 1.59 1.98 2.89 4.35 6.04 7.98 10.3 13.0 18.9 26.0 35.2 47.7 55.2 67.6 83.9 110 169 279 386 2,106 01418500 O -- 6.30 11.0 13.0 18.0 24.0 33.0 42.0 51.0 61.0 84.0 110 145 195 228 265 323 409 585 961 1,370 -- P 5.52 6.80 9.23 10.9 15.2 21.7 29.2 37.4 47.0 57.1 78.3 105 138 185 210 256 312 398 575 893 1,204 6,808 01419500 O -- 7.60 11.0 12.0 16.0 22.0 27.0 33.0 40.0 47.0 63.0 81.0 106 140 165 196 237 308 449 729 1,020 -- P 5.03 6.11 9.32 10.8 14.7 20.8 27.7 35.0 43.6 52.4 69.6 91.7 119 161 181 217 261 326 453 676 889 5,063 01420000 O 1.10 1.40 2.20 2.60 3.70 5.10 6.50 8.10 10.0 12.0 17.0 22.0 30.0 40.0 48.0 58.0 74.0 100 158 261 270 1,772 P 1.18 1.49 2.31 2.77 3.87 5.58 7.53 9.59 12.1 14.7 20.1 26.8 34.9 47.0 53.4 63.8 77.4 98.3 142 221 296 1,686
38 Estimation of Daily Mean Streamflow for Ungaged Stream Locations in the Delaware River Basin, Water Years 1960–2010 Appendix 3. Observed and predicted flow-duration exceedance probability discharges for streamgages used in regression analysis.—Continued [USGS, U.S. Geological Survey; --, flow-duration exceedance probability discharge could not be computed because of insufficient period of record; O, observed; P, predicted] USGS stream- gage number Type Flow-duration exceedance probability discharges (cubic feet per second) P99. 9946 P99. 95 P99 P98 P95 P90 P85 P80 P75 P70 P60 P50 P40 P30 P25 P20 P15 P10 P05 P02 P01 P0. 0054 01420500 O 23.0 28.0 41.0 48.0 62.0 86.0 109 133 160 188 248 325 424 561 655 780 960 1,240 1,830 2,850 3,929 21,770

P 19.6 23.4 33.1 38.1 51.5 72.1 96.2 123 153 184 247 329 434 586 657 805 968 1,206 1,656 2,429 3,189 17,716

01421614 O -- -- 0.05 0.06 0.10 0.18 0.27 0.36 0.44 0.53 0.74 0.98 1.30 1.60 1.90 2.40 3.10 4.10 6.00 10.0 13.0 --

P 0.01 0.01 0.02 0.03 0.05 0.08 0.11 0.15 0.21 0.28 0.44 0.62 0.86 1.18 1.41 1.70 2.16 2.96 5.05 9.31 13.4 72.1

01421618 O -- -- 0.62 0.77 1.20 2.20 3.50 4.70 6.33 8.10 12.0 16.0 22.0 29.0 34.0 41.0 52.0 68.1 109 180 250 --

P 0.25 0.34 0.51 0.66 1.00 1.59 2.28 3.13 4.20 5.50 8.47 12.1 16.9 23.7 27.8 34.2 42.7 56.4 87.8 146 201 1,016

01421900 O -- 3.40 8.40 10.0 14.0 21.0 30.0 41.0 52.0 67.0 96.0 135 184 250 296 354 440 566 827 1,300 1,830 --

P 3.36 4.43 5.41 6.71 9.99 15.4 21.9 30.1 40.1 51.8 78.4 113 159 226 262 328 405 523 770 1,198 1,617 7,779

01422389 O -- -- 0.02 0.03 0.05 0.13 0.22 0.31 0.42 0.52 0.75 0.97 1.30 1.70 1.90 2.30 2.90 4.00 6.04 8.90 12.00 --

P 0.01 0.02 0.02 0.03 0.05 0.08 0.12 0.16 0.22 0.29 0.45 0.64 0.87 1.18 1.41 1.69 2.15 2.95 5.04 9.31 13.46 73.9

01422500 O -- 0.90 2.40 3.10 4.30 6.60 10.0 14.0 19.0 25.0 36.0 50.0 69.0 94.0 111 134 166 216 321 513 705 --

P 1.13 1.50 2.12 2.67 3.99 6.17 8.74 11.9 15.8 20.4 30.7 43.7 60.9 85.2 99.3 123 153 200 303 490 671 3,366

01422738 O -- -- 0.02 0.02 0.04 0.07 0.10 0.17 0.25 0.33 0.50 0.68 0.90 1.10 1.30 1.50 1.90 2.50 3.90 6.65 9.05 --

P 0.01 0.01 0.02 0.03 0.04 0.07 0.10 0.14 0.19 0.24 0.38 0.53 0.72 0.99 1.18 1.40 1.78 2.43 4.10 7.49 10.7 58.9

01422747 O -- -- 1.70 1.90 2.70 4.30 6.00 8.80 12.00 15.0 23.0 29.0 38.0 48.0 55.0 64.0 78.0 101 145 237 320 --

P 0.80 1.06 1.35 1.70 2.51 3.83 5.36 7.16 9.36 11.9 17.5 24.4 33.3 45.7 53.1 65.1 81.1 106 164 270 374 1,983

01423000 O 13.0 14.0 24.0 29.0 40.0 59.0 83.0 109 137 169 246 340 461 627 741 880 1,070 1,380 2,000 3,070 4,280 21,300

P 12.0 15.1 19.7 23.6 33.9 50.2 69.7 93.7 122 154 224 315 437 611 699 876 1,073 1,367 1,960 2,968 3,970 19,884

01423500 O -- -- 0.50 0.58 0.60 0.97 1.20 1.60 2.20 2.80 4.50 6.60 9.70 14.0 17.0 20.0 24.0 32.0 47.0 76.0 112 --

P 0.22 0.30 0.38 0.49 0.75 1.17 1.64 2.20 2.89 3.69 5.53 7.73 10.5 14.3 16.8 20.5 25.9 34.9 56.3 98.4 140 755

0142400103 O -- 0.20 0.40 0.50 0.80 1.50 2.40 3.50 5.40 7.40 12.0 18.0 26.0 36.0 42.0 50.0 62.0 82.5 122 199 270 --

P 0.54 0.72 0.92 1.17 1.76 2.71 3.81 5.14 6.76 8.66 13.0 18.3 25.1 34.4 40.2 49.5 61.8 81.9 128 215 301 1,586

01424108 O -- -- 0.05 0.05 0.08 0.11 0.17 0.26 0.41 0.61 1.00 1.50 2.10 2.90 3.30 3.90 4.80 6.00 9.20 14.0 18.5 --

P 0.02 0.03 0.04 0.06 0.09 0.14 0.21 0.28 0.37 0.48 0.75 1.06 1.44 1.95 2.33 2.80 3.56 4.87 8.29 15.3 22.1 122

01425500 O -- -- 0.01 0.02 0.04 0.07 0.10 0.16 0.24 0.36 0.65 1.10 1.70 2.40 3.00 3.60 4.50 6.00 9.60 16.0 24.0 --

P 0.02 0.03 0.05 0.07 0.11 0.17 0.24 0.33 0.43 0.57 0.88 1.25 1.70 2.30 2.75 3.31 4.21 5.77 9.81 18.0 26.1 143

01425675 O -- -- 0.30 0.35 0.52 0.70 0.90 1.10 1.40 1.80 3.10 4.50 6.20 8.40 10.0 12.0 16.0 21.0 33.0 55.3 70.0 --

P 0.08 0.11 0.15 0.20 0.31 0.49 0.70 0.96 1.29 1.68 2.63 3.75 5.19 7.08 8.44 10.4 13.2 18.2 30.6 55.9 81.3 428

01426000 O -- 1.10 2.00 2.50 3.70 5.50 8.20 12.0 16.0 21.0 34.0 51.0 73.0 104 127 155 194 254 403 667 905 --

P 1.70 2.21 2.97 3.76 5.62 8.55 12.0 16.2 21.2 26.9 40.5 57.2 79.3 108 126 158 198 264 415 700 988 5,135

01427500 O -- 4.80 6.84 8.70 12.0 18.0 24.0 30.0 38.0 46.0 64.0 87.0 119 167 200 241 300 403 631 1,040 1,380 --

P 5.41 6.75 10.3 12.3 17.1 24.4 32.7 42.0 52.9 64.9 90.0 121 161 218 247 301 363 458 652 990 1,318 7,240

01428000 O -- -- 1.80 2.60 3.90 5.60 7.20 9.40 12.0 16.0 24.0 32.0 46.0 66.0 79.0 98.0 119 155 228 356 485 --

P 1.43 1.86 3.34 4.10 5.78 8.34 11.2 14.4 18.1 22.5 31.9 43.1 57.1 76.9 87.5 106 128 163 240 376 506 2,812

01428750 O -- -- 5.90 6.90 8.20 11.0 14.0 17.0 21.0 24.0 33.0 45.0 58.0 76.0 89.0 107 135 180 291 493 651 --

P 1.36 1.75 3.02 3.75 5.36 7.78 10.5 13.5 17.0 21.0 29.9 40.4 53.7 70.9 81.4 99.4 123 161 247 410 572 3,251
 Appendixes 1–3 39 Appendix 3. Observed and predicted flow-duration exceedance probability discharges for streamgages used in regression analysis.—Continued [USGS, U.S. Geological Survey; --, flow-duration exceedance probability discharge could not be computed because of insufficient period of record; O, observed; P, predicted] USGS stream- gage number Type Flow-duration exceedance probability discharges (cubic feet per second) P99. 9946 P99. 95 P99 P98 P95 P90 P85 P80 P75 P70 P60 P50 P40 P30 P25 P20 P15 P10 P05 P02 P01 P0. 0054 01431000 O -- -- 3.70 4.40 7.00 10.0 14.0 19.0 25.0 31.0 45.0 62.0 88.0 125 149 180 224 301 461 747 1,142 -- P 2.28 2.92 5.36 6.65 9.46 13.6 18.2 23.4 29.5 36.2 51.9 70.3 93.8 124 142 174 214 279 429 705 984 5,533 01435000 O 7.70 9.80 15.0 18.0 25.0 35.0 46.0 56.0 65.0 74.0 95.0 119 148 187 215 250 304 389 575 979 1,470 5,990 P 8.89 10.5 12.7 14.7 20.0 27.9 37.0 46.1 56.6 66.4 86.4 112 145 189 213 259 317 407 590 936 1,282 7,680 01439500 O 2.60 3.85 8.80 11.0 17.0 27.0 39.0 53.0 69.0 86.0 121 161 210 272 312 362 428 526 704 986 1,270 9,020 P 6.79 8.44 19.3 22.3 29.2 39.1 49.7 60.6 72.8 85.6 111 143 181 238 263 312 367 449 612 892 1,162 6,906 01440000 O 4.40 5.50 8.60 9.80 13.0 17.0 21.0 26.0 33.0 40.0 55.0 73.0 93.0 120 137 159 190 238 338 515 687 5,340 P 6.32 8.22 11.0 12.8 16.5 22.0 27.9 33.7 40.4 47.8 62.1 79.1 99.2 130 144 168 196 237 319 458 587 3,577 01440400 O 5.10 5.57 7.76 8.90 12.0 17.0 23.0 31.0 40.0 49.0 67.0 88.0 112 144 165 196 237 301 433 672 913 6,040 P 4.16 5.17 10.2 12.1 16.2 21.9 28.0 34.1 41.0 47.9 63.1 81.0 103 131 147 176 213 271 398 634 870 5,374 01442500 O 30.1 34.0 50.0 57.0 73.0 95.0 120 147 177 210 277 360 455 590 684 802 963 1,220 1,740 2,650 3,500 29,110 P 26.0 30.9 51.8 59.7 77.8 102 128 154 182 208 266 338 427 541 598 724 867 1,090 1,549 2,384 3,238 20,183 01443500 O 5.80 11.0 18.0 20.0 27.0 35.0 43.0 52.0 63.0 76.0 103 136 175 224 255 293 346 423 590 889 1,160 5,180 P 15.2 19.5 19.1 22.5 29.3 38.9 48.7 58.9 70.1 82.2 108 138 174 222 246 294 349 437 625 957 1,283 8,088 01445000 O -- 1.70 2.60 2.95 4.50 6.50 9.30 12.0 16.0 20.0 28.0 37.0 48.0 62.0 70.0 79.0 91.0 106 135 182 224 -- P 2.97 3.96 3.96 4.81 6.42 8.68 11.0 13.3 16.0 18.9 25.5 32.5 40.9 51.9 58.1 68.7 82.2 105 156 249 340 2,176 01445500 O 12.1 14.0 19.0 22.0 29.0 36.0 44.0 51.0 60.0 70.0 90.0 114 145 183 208 237 276 333 442 601 728 1,930 P 14.4 18.4 20.8 24.1 30.7 39.8 49.2 58.4 68.5 79.3 102 127 158 201 220 259 303 370 511 754 987 6,342 01446000 O -- 1.30 2.30 2.90 4.30 6.40 9.30 12.0 15.0 19.0 27.0 37.0 48.0 62.0 71.0 82.0 98.0 120 162 229 308 -- P 3.59 4.77 4.87 5.92 7.95 10.7 13.5 16.3 19.4 22.8 30.4 38.8 48.8 61.4 68.8 81.8 98.4 126 190 310 429 2,741 01447500 O 7.00 8.00 14.0 17.0 23.0 32.0 43.0 54.0 66.0 78.0 103 130 161 203 233 268 318 391 548 810 1,100 16,070 P 5.50 6.78 13.9 16.4 22.2 30.0 38.4 47.1 56.7 66.3 87.1 112 143 184 206 248 301 384 564 900 1,240 7,556 01447720 O -- -- 30.0 32.0 42.0 54.0 67.0 81.0 96.0 110 141 179 220 275 311 360 436 545 783 1,180 1,580 -- P 8.19 9.91 17.2 20.4 28.4 38.8 50.5 62.7 76.1 88.6 116 151 196 254 286 350 430 556 822 1,338 1,880 10,792 01448500 O -- 0.27 0.42 0.50 0.66 0.89 1.20 1.40 1.70 1.90 2.50 3.20 4.00 5.10 5.80 6.70 7.80 9.60 14.0 22.0 30.0 -- P 0.37 0.49 0.35 0.44 0.63 0.88 1.14 1.39 1.68 1.96 2.58 3.29 4.10 5.13 5.88 6.89 8.55 11.4 18.4 33.1 48.1 311 01449360 O -- 11.0 15.0 17.0 22.0 28.0 33.0 38.0 44.0 50.0 62.0 76.0 93.0 113 127 144 168 204 277 392 517 -- P 5.58 7.06 7.47 9.01 12.2 16.5 20.9 25.4 30.2 35.0 46.1 58.8 74.3 93.1 105 126 154 200 305 512 724 4,582 01450500 O 9.20 11.0 18.0 21.0 27.0 35.0 42.0 50.0 57.0 65.0 81.0 101 125 159 180 209 248 309 444 689 921 4,490 P 8.75 11.2 11.9 14.3 19.0 25.1 31.4 37.6 44.4 51.4 67.5 85.5 107 133 149 179 216 277 418 685 956 6,212 01451500 O 23.0 25.0 28.0 30.0 35.0 41.0 46.0 51.0 56.0 61.0 71.0 82.0 96.0 113 123 136 152 175 224 321 421 4,550 P 4.62 5.94 8.98 11.2 15.2 20.3 25.3 30.6 36.2 42.1 57.2 73.2 92.9 113 127 155 191 254 412 729 1,067 7,003 01451800 O -- 0.71 2.80 4.30 7.00 10.0 14.0 18.0 22.0 27.0 37.0 49.0 65.0 89.0 104 127 160 212 325 526 737 -- P 3.57 4.64 5.86 7.28 10.1 13.6 17.2 21.0 25.0 29.2 39.5 50.9 64.8 80.3 90.8 110 136 180 286 500 726 4,583 01452000 O 0.00 0.00 3.70 4.70 7.84 12.0 17.0 22.0 28.0 33.0 46.0 63.0 83.0 112 131 157 195 253 390 650 927 6,440 P 5.36 6.90 9.01 11.1 15.2 20.2 25.4 30.7 36.4 42.3 56.9 72.9 92.4 114 128 156 191 251 398 690 997 6,404
40 Estimation of Daily Mean Streamflow for Ungaged Stream Locations in the Delaware River Basin, Water Years 1960–2010 Appendix 3. Observed and predicted flow-duration exceedance probability discharges for streamgages used in regression analysis.—Continued [USGS, U.S. Geological Survey; --, flow-duration exceedance probability discharge could not be computed because of insufficient period of record; O, observed; P, predicted] USGS stream- gage number Type Flow-duration exceedance probability discharges (cubic feet per second) P99. 9946 P99. 95 P99 P98 P95 P90 P85 P80 P75 P70 P60 P50 P40 P30 P25 P20 P15 P10 P05 P02 P01 P0. 0054 01452500 O 5.30 6.40 11.0 14.0 17.0 21.0 24.0 27.0 29.0 31.0 37.0 43.0 50.0 61.0 68.0 75.0 85.0 99.0 128 180 238 2,093

P 2.34 3.04 4.54 5.72 7.85 10.5 13.2 15.9 18.9 22.1 30.2 38.6 48.8 59.0 66.9 81.1 100 134 222 401 591 3,963

01459500 O -- 0.39 0.90 1.20 2.10 3.80 5.40 7.40 10.0 14.0 24.0 37.0 56.0 87.0 110 145 204 325 610 1,050 1,790 --

P 2.02 2.61 4.84 6.34 9.87 14.2 18.9 24.7 30.6 36.5 51.9 71.5 97.3 125 146 185 241 339 589 1,153 1,827 9,539

01464500 O 7.00 9.70 21.0 26.0 32.0 39.0 46.0 52.0 59.0 65.0 78.0 92.0 108 129 144 163 193 248 380 602 817 3,770

P 6.19 8.23 13.4 15.6 20.4 26.5 33.0 39.3 46.3 53.8 67.5 85.5 107 143 156 180 207 247 322 452 579 3,254

01464907 O -- -- 1.20 1.70 2.40 3.70 5.60 7.70 9.50 11.0 15.0 19.0 25.0 33.0 40.0 49.0 64.0 95.1 194 396 695 --

P 1.14 1.52 1.96 2.60 3.80 5.21 6.57 8.06 9.58 11.2 15.7 20.4 26.2 31.0 35.9 44.3 56.9 80.5 147 299 478 3,106

01465798 O -- 0.40 1.60 2.20 3.20 4.20 5.10 6.00 6.80 7.70 9.60 12.0 15.0 19.0 23.0 28.0 39.0 61.0 124 259 408 --

P 0.79 1.03 3.01 3.80 5.13 6.65 8.06 9.40 10.8 12.3 16.1 20.0 24.5 28.8 32.3 38.5 47.3 63.2 105 193 287 2,031

01466500 O 0.50 0.61 0.83 0.86 0.98 1.10 1.20 1.20 1.30 1.40 1.60 1.80 2.00 2.30 2.50 2.80 3.10 3.50 4.30 5.60 6.80 29.5

P 0.21 0.30 0.48 0.58 0.74 0.96 1.16 1.32 1.52 1.76 2.18 2.64 3.11 4.02 4.38 4.78 5.37 6.34 8.41 12.1 15.2 98.5

01467048 O -- 8.90 13.0 14.0 17.0 21.0 24.0 27.0 30.0 34.0 41.0 50.0 60.0 75.0 85.0 99.2 123 169 282 541 814 --

P 3.14 4.04 8.22 10.2 13.4 17.1 20.4 23.5 26.7 30.0 39.0 47.8 58.2 67.6 75.4 90.4 111 147 242 440 654 4,764

01467086 O -- 2.10 3.90 4.60 5.90 7.20 8.10 9.00 10.0 11.0 13.0 16.0 19.0 23.0 25.0 29.0 36.0 49.0 81.0 150 204 --

P 0.43 0.54 2.26 2.92 3.91 5.02 5.98 6.89 7.81 8.81 11.8 14.4 17.4 19.5 22.0 26.4 32.8 45.3 80.7 159 247 1,926

01467150 O -- 3.46 5.60 6.50 8.00 9.90 12.0 13.0 14.0 16.0 18.0 21.0 24.0 28.0 31.0 35.0 43.0 58.0 98.0 175 247 --

P 1.46 1.97 3.88 4.58 5.82 7.35 8.82 10.1 11.5 13.1 16.1 19.6 23.4 29.7 32.3 36.4 41.6 49.9 67.3 98.5 128 825

01468500 O -- 23.0 47.0 53.0 62.0 76.0 90.0 103 116 130 160 198 242 303 342 389 453 553 750 1,100 1,480 --

P 18.6 23.5 29.2 34.2 43.8 56.0 68.2 80.0 92.5 105 133 165 203 250 275 328 391 495 724 1,150 1,583 10,676

01470500 O 40.8 61.0 92.0 106 128 160 194 226 258 292 369 461 580 746 856 1,000 1,200 1,500 2,110 3,170 4,256 32,430

P 54.2 66.2 90.8 104 131 163 196 228 260 291 363 446 547 666 726 874 1,038 1,303 1,874 2,923 4,008 27,264

01470756 O -- -- 17.0 21.0 31.0 42.0 53.0 65.0 76.0 89.0 116 151 192 250 293 349 435 572 862 1,392 2,050 --

P 11.1 14.1 20.8 25.3 33.9 44.5 55.1 66.3 77.9 89.7 119 152 192 236 263 321 392 512 796 1,351 1,940 12,476

01470779 O -- 16.5 27.0 30.0 35.0 42.0 48.0 52.0 57.0 62.0 74.0 86.0 100 118 130 143 160 188 253 368 508 --

P 2.63 3.41 6.31 8.05 11.1 14.9 18.5 22.4 26.5 30.9 42.8 55.0 70.0 84.0 95.3 117 145 196 332 612 918 6,089

01471000 O -- 34.0 50.0 55.0 65.0 85.0 98.0 113 127 140 171 212 265 335 380 430 501 607 833 1,240 1,700 --

P 11.1 14.1 23.2 28.6 38.8 50.9 62.9 76.0 89.3 103 140 179 228 278 312 384 471 621 989 1,716 2,504 16,015

01471980 O -- 12.0 21.0 23.0 28.0 34.0 39.0 44.0 50.0 56.0 69.0 85.0 105 129 145 168 197 245 368 617 887 --

P 4.19 5.48 9.00 11.3 15.6 20.8 25.9 31.4 37.0 42.8 57.5 73.9 94.0 115 130 159 196 262 424 758 1,122 7,064

01472000 O 175 201 260 298 367 457 545 636 730 820 1,030 1,300 1,630 2,070 2,330 2,690 3,160 3,850 5,200 7,564 9,834 71,200

P 111 134 240 278 350 432 514 600 681 759 959 1,189 1,477 1,784 1,944 2,383 2,845 3,602 5,270 8,346 11,658 77,707

01472157 O -- 7.57 11.0 13.0 17.0 20.0 24.0 28.0 32.0 36.0 47.0 58.0 72.0 90.0 102 116 137 173 257 438 633 --

P 3.03 3.96 7.06 8.79 12.0 15.7 19.3 23.1 27.0 31.0 41.2 52.2 65.4 79.9 89.6 108 131 172 273 475 689 4,441

01472174 O -- -- 1.60 1.90 2.40 2.90 3.30 3.60 4.00 4.50 5.40 6.50 7.84 9.40 10.0 11.0 13.0 17.0 26.0 55.3 93.0 --

P 0.32 0.44 0.68 0.87 1.21 1.62 2.00 2.37 2.76 3.20 4.28 5.36 6.60 7.93 8.99 10.6 13.0 17.4 29.2 54.2 80.7 550
 Appendixes 1–3 41 Appendix 3. Observed and predicted flow-duration exceedance probability discharges for streamgages used in regression analysis.—Continued [USGS, U.S. Geological Survey; --, flow-duration exceedance probability discharge could not be computed because of insufficient period of record; O, observed; P, predicted] USGS stream- gage number Type Flow-duration exceedance probability discharges (cubic feet per second) P99. 9946 P99. 95 P99 P98 P95 P90 P85 P80 P75 P70 P60 P50 P40 P30 P25 P20 P15 P10 P05 P02 P01 P0. 0054 01472198 O -- 4.40 8.70 9.90 13.0 15.0 18.0 20.0 23.0 25.0 33.0 40.0 50.0 61.0 69.0 79.0 93.0 116 171 298 446 -- 1.82 2.42 3.67 4.66 6.55 8.87 11.2 13.6 16.2 18.9 25.6 33.0 42.1 51.6 58.7 71.3 88.6 119 196 358 533 3,367 01472199 O -- 3.20 4.90 5.40 6.70 8.10 9.50 11.0 13.0 15.0 20.0 25.0 31.0 38.0 43.0 49.0 59.0 75.0 111 203 285 -- P 0.75 1.02 1.63 2.12 3.15 4.41 5.71 7.14 8.66 10.2 14.2 18.8 24.5 30.6 35.3 43.3 54.8 75.4 128 244 374 2,197 01473120 O -- 0.30 1.30 2.40 4.11 6.30 7.90 9.50 11.0 13.0 20.0 28.0 40.0 53.0 64.0 79.0 100 142 288 630 1,042 -- P 3.72 4.79 7.26 9.18 12.3 15.7 18.9 22.0 25.1 28.4 38.0 47.0 57.7 66.0 74.2 90.0 112 152 263 501 765 5,689 01475510 O -- -- 12.0 14.0 17.0 20.0 23.0 25.0 28.0 31.0 37.0 45.0 52.0 61.0 67.0 75.0 86.0 106 171 301 440 -- P 1.55 1.99 6.03 7.52 9.86 12.5 14.8 17.0 19.2 21.6 28.1 34.3 41.5 48.0 53.4 63.5 77.2 102 168 304 448 3,305 01475530 O -- -- 1.50 1.60 1.80 2.20 2.50 2.80 3.00 3.30 3.90 4.50 5.20 5.90 6.50 7.50 8.96 12.0 23.0 43.0 68.0 -- P 0.16 0.22 0.67 0.87 1.16 1.50 1.79 2.05 2.33 2.65 3.53 4.28 5.12 5.84 6.58 7.68 9.42 12.8 22.1 42.5 64.1 498 01475850 O -- 1.10 2.70 3.50 4.60 6.00 7.20 8.50 9.70 11.0 13.0 16.0 19.0 22.0 25.0 28.0 32.0 40.0 64.0 120 186 -- P 0.69 0.93 1.90 2.42 3.32 4.36 5.32 6.27 7.26 8.33 11.1 13.8 17.0 20.4 23.0 27.2 33.3 44.2 72.7 132 195 1,322 01477120 O -- 3.30 7.60 9.71 12.0 14.0 16.0 17.0 19.0 21.0 24.0 29.0 34.0 39.0 43.0 47.0 54.0 66.0 98.0 170 249 -- P 2.25 3.04 6.28 7.35 9.19 11.4 13.5 15.3 17.3 19.5 23.8 28.6 34.0 42.9 46.3 52.2 59.1 70.4 94.0 136 174 1,146 01477800 O 0.09 0.10 0.30 0.40 0.57 0.80 1.00 1.20 1.40 1.70 2.20 2.90 3.90 5.20 6.40 8.00 11.0 18.0 41.0 96.4 150 1,444 P 0.18 0.24 0.89 1.17 1.59 2.05 2.44 2.80 3.18 3.61 4.83 5.90 7.11 8.06 9.11 10.7 13.3 18.3 32.6 64.5 99.7 763 01478000 O 0.20 0.40 1.50 2.10 3.10 4.40 5.40 6.50 7.50 8.50 11.0 13.0 16.0 20.0 22.0 26.0 32.0 47.0 98.2 219 366 2,466 P 0.65 0.88 2.54 3.21 4.39 5.69 6.88 8.06 9.26 10.6 13.8 17.2 21.2 25.6 28.6 33.8 40.9 53.8 86.3 153 224 1,477 01479000 O 5.10 6.47 16.0 20.0 26.0 32.0 38.0 44.0 49.0 54.0 65.0 78.0 93.0 111 123 139 160 198 300 549 875 7,630 P 4.67 5.96 19.3 23.1 29.2 35.9 41.9 47.5 53.0 58.9 73.4 88.6 106 126 138 162 191 241 358 583 814 5,731 01479820 O -- -- 5.70 8.40 11.0 13.0 15.0 17.0 19.0 20.0 25.0 29.0 34.0 41.0 44.0 49.0 55.0 65.0 96.0 190 329 -- P 1.45 1.91 5.01 6.16 8.00 10.1 11.9 13.7 15.4 17.4 22.1 26.9 32.3 38.4 42.4 49.5 59.0 75.9 118 200 284 2,015 01480000 O 4.50 5.65 11.0 13.0 17.0 19.0 22.0 25.0 28.0 31.0 37.0 44.0 53.0 63.0 70.0 79.0 90.0 110 161 293 438 3,890 P 2.60 3.37 9.97 12.0 15.3 18.9 22.2 25.2 28.2 31.5 39.5 47.6 56.8 67.6 74.0 86.3 102 129 195 321 449 3,205 01480015 O -- -- 13.0 16.0 19.0 22.0 25.0 29.0 32.0 36.0 43.0 52.0 62.0 74.0 82.0 91.0 105 129 192 349 537 -- P 2.81 3.63 11.3 13.6 17.2 21.2 24.9 28.1 31.4 34.9 43.7 52.5 62.7 74.5 81.4 95.0 112 142 213 351 491 3,507 01480100 O -- -- 0.43 0.68 1.20 1.50 1.80 2.10 2.40 2.80 3.60 4.40 5.20 6.40 7.30 8.90 12.0 17.0 37.0 78.8 118 -- P 0.24 0.32 0.96 1.23 1.64 2.10 2.50 2.87 3.25 3.70 4.84 5.89 7.06 8.27 9.24 10.7 12.9 17.0 28.0 50.9 74.6 545 01480300 O 1.00 1.40 3.30 4.30 5.70 6.90 7.90 9.00 9.90 11.0 13.0 16.0 18.0 22.0 24.0 27.0 32.0 42.0 78.0 161 259 1,620 P 0.41 0.57 1.51 1.94 2.80 3.84 4.87 5.97 7.14 8.40 11.4 14.8 19.0 23.9 27.2 32.6 40.3 53.8 87.3 157 233 1,377 01480675 O -- 0.26 0.68 0.91 1.50 2.10 2.60 3.20 3.80 4.40 6.00 7.90 10.0 12.0 14.0 16.0 19.0 25.0 42.0 71.0 97.0 -- P 0.28 0.39 0.60 0.79 1.17 1.63 2.10 2.60 3.14 3.72 5.12 6.71 8.63 10.9 12.5 15.0 18.8 25.5 42.9 80.8 122 717 01481000 O 42.0 50.0 69.0 80.0 99.7 118 138 158 174 190 230 270 322 391 439 496 571 699 985 1,580 2,230 9,590 P 20.5 25.3 66.9 78.2 98.7 121 143 163 183 203 251 306 372 449 488 583 688 863 1,251 1,979 2,744 18,502 01482500 O 0.00 0.00 0.80 1.70 2.90 4.40 5.40 6.30 7.30 8.50 10.0 12.0 14.0 18.0 20.0 22.0 27.0 35.0 57.0 107 163 4,325 P 0.61 0.85 1.78 2.24 3.05 3.98 4.84 5.68 6.57 7.56 9.83 12.3 15.1 18.7 20.8 24.2 28.9 37.1 57.1 96.7 137 874
42 Estimation of Daily Mean Streamflow for Ungaged Stream Locations in the Delaware River Basin, Water Years 1960–2010 Appendix 3. Observed and predicted flow-duration exceedance probability discharges for streamgages used in regression analysis.—Continued [USGS, U.S. Geological Survey; --, flow-duration exceedance probability discharge could not be computed because of insufficient period of record; O, observed; P, predicted] USGS stream- gage number Type Flow-duration exceedance probability discharges (cubic feet per second) P99. 9946 P99. 95 P99 P98 P95 P90 P85 P80 P75 P70 P60 P50 P40 P30 P25 P20 P15 P10 P05 P02 P01 P0. 0054 01483000 O -- -- 0.00 0.00 2.50 3.90 5.10 6.50 7.30 8.90 12.0 15.0 19.0 24.0 27.0 31.0 36.0 47.0 70.0 117 167 --

P 0.99 1.36 2.98 3.69 4.88 6.21 7.42 8.57 9.78 11.2 14.3 17.6 21.3 26.2 28.9 33.3 39.3 49.6 74.1 121 169 1,106

01483500 O -- -- 2.20 2.50 2.90 3.40 3.80 4.20 4.70 5.00 6.00 7.10 8.70 10.0 12.0 13.0 15.0 18.0 28.0 45.0 65.0 --

P 0.63 0.91 1.65 2.03 2.64 3.30 3.88 4.38 4.93 5.57 6.95 8.39 9.94 12.2 13.4 15.1 17.4 21.5 31.2 49.4 67.2 447

01484000 O -- 1.00 1.50 1.80 2.40 3.00 3.50 4.10 4.70 5.60 7.60 10.0 13.0 17.0 20.0 23.0 27.0 35.0 54.0 96.0 139 --

P 0.55 0.80 1.45 1.84 2.54 3.27 3.95 4.62 5.30 6.05 7.67 9.59 11.8 14.9 16.5 19.0 22.4 28.2 41.7 68.4 96.1 563

01484100 O 0.01 0.04 0.31 0.40 0.60 0.81 1.10 1.30 1.50 1.80 2.30 2.80 3.40 4.10 4.60 5.10 5.80 6.70 8.90 14.0 21.0 99.9

P 0.12 0.18 0.26 0.34 0.51 0.69 0.86 1.04 1.23 1.44 1.88 2.42 3.05 3.98 4.51 5.19 6.27 8.12 12.6 21.9 31.9 170

01484270 O -- -- 4.30 4.80 6.00 7.00 7.70 8.30 8.90 9.40 10.0 12.0 13.0 15.0 16.0 17.0 18.0 20.0 24.0 28.0 32.5 --

P 0.95 1.33 3.25 3.81 4.42 5.01 5.45 5.64 5.93 6.35 7.22 8.01 8.77 10.2 10.8 11.6 12.8 15.0 20.3 29.9 38.5 310

01484300 O -- -- 2.30 2.60 3.20 3.90 4.30 4.90 5.50 6.20 7.70 9.10 10.0 12.0 13.0 14.0 15.0 17.0 21.0 27.0 31.0 --

P 1.00 1.40 3.54 4.13 4.73 5.33 5.76 5.93 6.21 6.64 7.55 8.32 9.05 10.5 11.0 11.8 13.0 15.3 20.6 30.3 38.9 323

01484500 O 0.08 0.15 0.75 0.91 1.20 1.60 2.00 2.40 2.80 3.30 4.20 5.40 6.70 8.30 9.30 10.0 12.0 15.0 19.0 27.0 35.0 191

P 0.33 0.48 0.94 1.17 1.54 1.89 2.18 2.41 2.66 2.94 3.56 4.22 4.91 5.96 6.50 7.24 8.38 10.4 15.4 25.2 35.1 236

01487000 O 6.70 8.40 16.0 18.0 22.0 26.0 30.0 35.0 39.0 43.0 54.0 69.0 85.0 105 117 133 153 182 239 345 452 2,700

P 5.47 7.57 14.1 16.9 21.9 26.6 30.9 34.9 38.8 42.9 51.4 62.4 74.9 94.2 102 117 134 162 222 336 455 2,740

01488500 O 1.20 1.60 3.10 3.60 5.60 7.90 9.80 12.0 14.0 16.0 22.0 30.0 40.0 52.0 60.0 71.0 86.0 114 176 311 447 2,681

P 1.79 2.60 3.80 4.84 7.06 9.34 11.6 14.1 16.6 19.1 24.5 31.9 40.9 53.8 60.2 71.4 86.0 110 163 273 393 1,987

01498500 O -- 6.31 9.30 11.0 16.0 22.0 29.0 38.0 49.0 61.0 94.0 132 184 260 312 380 463 587 859 1,325 1,798 --

P 3.35 4.44 4.57 5.77 8.95 14.3 20.8 29.6 40.5 53.5 83.8 124 181 262 308 392 493 648 979 1,564 2,153 9,648

01499000 O -- 4.83 7.46 9.00 12.0 16.0 21.0 28.0 35.0 42.0 62.0 89.0 124 172 205 244 294 366 557 917 1,200 --

P 2.93 3.90 2.80 3.57 5.60 9.00 13.2 18.8 25.8 34.1 53.7 79.9 116 168 199 252 319 422 646 1,050 1,457 6,527

01533950 O -- -- 0.30 0.50 0.90 1.40 1.90 2.40 2.90 3.50 5.10 7.20 9.60 14.0 17.0 21.0 27.0 37.5 63.0 122 176 --

P 0.30 0.41 0.70 0.90 1.33 1.97 2.66 3.46 4.41 5.51 8.09 11.0 14.6 19.3 22.4 27.1 33.8 45.1 72.7 127 181 1,035

01534000 O 7.10 9.70 21.0 25.0 36.0 52.0 67.0 85.0 109 135 194 270 373 520 630 765 957 1,260 1,930 3,170 4,330 25,770

P 11.3 14.1 28.9 34.7 48.3 68.3 90.7 117 147 181 257 349 470 628 711 885 1,078 1,378 2,018 3,136 4,271 23,328

01538000 O 1.60 2.36 4.50 5.10 6.80 9.10 12.0 15.0 18.0 22.0 31.0 41.0 53.0 69.0 80.0 93.0 111 139 198 306 419 2,610

P 0.98 1.30 3.55 4.45 6.24 8.73 11.3 14.2 17.4 20.9 29.3 38.6 50.2 64.1 73.0 88.6 109 143 226 386 549 3,313

01539000 O 8.40 9.30 19.0 22.0 35.0 54.0 76.0 99.0 125 150 208 278 368 495 580 685 838 1,070 1,560 2,380 3,190 25,760

P 13.7 17.3 33.5 39.8 53.2 71.4 90.8 112 135 159 214 278 359 458 511 626 756 964 1,420 2,246 3,091 18,752

01576754 O -- -- 95.0 112 143 182 217 251 285 316 390 472 567 694 776 883 1,020 1,240 1,752 2,741 4,140 --

P 20.1 24.8 90.4 108 135 164 190 217 242 269 345 419 509 590 644 781 934 1,205 1,871 3,143 4,506 33,139

01578400 O -- -- 1.60 1.80 2.10 2.60 3.00 3.30 3.60 3.90 4.60 5.40 6.08 7.20 7.90 8.70 10.00 13.0 19.0 41.8 65.0 --

P 0.20 0.27 0.91 1.16 1.53 1.96 2.32 2.64 2.99 3.40 4.48 5.41 6.44 7.43 8.30 9.61 11.61 15.4 25.7 47.2 69.4 533.01
Prepared by USGS West Trenton Publishing Service Center.

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Coordinator—National Water Census

U.S. Geological Survey

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or visit the National Water Census Web site at:

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Stuckey, M.H.—Estimation of Daily Mean Streamflow for Ungaged Stream Locations in the Delaware River Basin, Water Years 1960–2010—Scientific Investigations Report 2015–5157

ISSN 2328-0328 (online)

http://dx.doi.org/10.3133/sir20155157