U.S. Department of the Interior

U.S. Geological Survey

Scientific Investigations Report 2012–5151

Prepared in Cooperation with the Virginia Department of Environmental Quality, 

Office of Surface Water Investigations

Spatial and Temporal Trends in Runoff at Long-Term 

Streamgages within and near the Chesapeake Bay 

Watershed
Cover photo: Hughes River in the Shenandoah National Park within the Chesapeake Bay Watershed. Picture by Karen C. Rice, modified 

by James A. Tomberlin.
Spatial and Temporal Trends in Runoff at 

Long-Term Streamgages within and near 

the Chesapeake Bay Watershed

By Karen C. Rice and Robert M. Hirsch

Prepared in Cooperation with the Virginia Department of Environmental Quality, 

Office of Surface Water Investigations

Scientific Investigations Report 2012–5151

U.S. Department of the Interior

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

KEN SALAZAR, Secretary

U.S. Geological Survey

Marcia K. McNutt, Director

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

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Suggested citation:

Rice, K.C., Hirsch, R.M., 2012, Spatial and temporal trends in runoff at long-term streamgages within and near the 

Chesapeake Bay Watershed: U.S. Geological Survey Scientific Investigations Report 2012–5151, 56 p.

ISBN 978 1 4113 3456 4
iii

Contents

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

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

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

Methods..................................................................................................................................................2

Time-Series Graphs.....................................................................................................................6

Flow Statistics ..............................................................................................................................7

Spatial Trends In Runoff................................................................................................................................7

Annual Flow Statistics..........................................................................................................................7

Annual 7-Day Minimum Runoff..................................................................................................7

Annual Mean Runoff .................................................................................................................10

Annual 1-Day Maximum Runoff...............................................................................................10

Seasonal Flow Statistics ...................................................................................................................10

The 7-Day Minimum Runoff......................................................................................................11

Mean Runoff ...............................................................................................................................12

The 1-Day Maximum Runoff.....................................................................................................13

Discussion Of Annual And Seasonal Flow Statistics.............................................................................14

Temporal Trends In Runoff .........................................................................................................................15

Summary........................................................................................................................................................23

Acknowledgments.......................................................................................................................................24

References Cited..........................................................................................................................................24

Appendix........................................................................................................................................................25

Figures

1. Map showing location of study area.........................................................................................3

2. Map showing locations of streamgages analyzed .................................................................4

3. Graph showing spatial trend in annual 7-day minimum runoff, 1930–2010.........................9

4. Graph showing spatial trend in annual mean runoff, 1930–2010........................................10

5. Graph showing spatial trend in annual 1-day maximum runoff, 1930–2010......................11

6. Graph showing spatial trend in fall 7-day minimum runoff, 1930–2010 .............................11

7. Graph showing spatial trend in winter 7-day minimum runoff, 1930–2010 ......................11

8. Graph showing spatial trend in spring 7-day minimum runoff, 1930–2010.......................12

9. Graph showing spatial trend in summer 7-day minimum runoff, 1930–2010 ....................12

10. Graph showing spatial trend in fall mean runoff, 1930–2010...............................................12

11. Graph showing spatial trend in winter mean runoff, 1930–2010.........................................12

12. Graph showing spatial trend in spring mean runoff, 1930–2010.........................................13

13. Graph showing spatial trend in summer mean runoff, 1930–2010......................................13

14. Graph showing spatial trend in fall 1-day maximum runoff, 1930–2010 ............................13

15. Graph showing spatial trend in winter 1-day maximum runoff, 1930–2010 ......................14
iv

16. Graph showing spatial trend in spring 1-day maximum runoff, 1930–2010.......................14

17. Graph showing spatial trend in summer 1-day maximum runoff, 1930–2010 ...................14

18. Graphs showing selected regression model for means of the 7-day minimum runoff...20

19. Graphs showing selected regression model for means of the mean runoff ....................21

20. Graphs showing selected regression model for means of the 1-day maximum runoff..21

1−1 to 1–30. Graphs showing streamflow statistics, annual values and seasonal values, and

locally weighted scatterplot smooth for selected streamgages within the Chesapeake 

Bay Watershed..................................................................................................................... 26–55

Tables

1. Attributes associated with streamgages and their location, Chesapeake Bay

watershed ......................................................................................................................................5

2. Results of annual and seasonal trend slopes for 1930–2010.................................................8

3. Summary of results of annual and seasonal trends in data for 1930–2010.........................9

4. Summary of results of annual and seasonal trends in data for 1930–2010 north and

south of 40.25 degrees north latitude ......................................................................................10

5. Results of annual and seasonal trend slopes for 1930–1969 and 1970–2010....................15

6. Summary of results of annual and seasonal trends in data for 1930–1969 and

1970–2010 north and south of 40.25 degrees north latitude.................................................19

7. Model form, selected model and model coefficients, standard errors of the model

coefficients, and R2 values for the six time series tested ....................................................23
v

Conversion Factors

Multiply By To obtain

Area

square kilometer (km2) 0.3861 square mile (mi2)

square mile (mi2) 2.590 square kilometer (km2) 

Flow rate

millimeter per year (mm/yr) 0.3937 inch per year (in/yr)

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

Abbreviations

ANCOVA analysis of covariance

RSS residual sum of squares

SSE sum of squared errors

U.S. United States

USGS U.S. Geological Survey
vi
Abstract

Long-term streamflow data within the Chesapeake Bay 

watershed and surrounding area were analyzed in an attempt 

to identify trends in streamflow. Data from 30 streamgages 

near and within the Chesapeake Bay watershed were selected 

from 1930 through 2010 for analysis. Streamflow data were 

converted to runoff and trend slopes in percent change per 

decade were calculated. Trend slopes for three runoff statistics (the 7-day minimum, the mean, and the 1-day maximum) 

were analyzed annually and seasonally. The slopes also were 

analyzed both spatially and temporally. The spatial results 

indicated that trend slopes in the northern half of the watershed were generally greater than those in the southern half. 

The temporal analysis was done by splitting the 80-year flow 

record into two subsets; records for 28 streamgages were analyzed for 1930 through 1969 and records for 30 streamgages 

were analyzed for 1970 through 2010. The mean of the data 

for all sites for each year were plotted so that the following datasets were analyzed: the 7-day minimum runoff for 

the north, the 7-day minimum runoff for the south, the mean 

runoff for the north, the mean runoff for the south, the 1-day 

maximum runoff for the north, and the 1-day maximum runoff 

for the south. Results indicated that the period 1930 through 

1969 was statistically different from the period 1970 through 

2010. For the 7-day minimum runoff and the mean runoff, the 

latter period had significantly higher streamflow than did the 

earlier period, although within those two periods no significant 

linear trends were identified. For the 1-day maximum runoff, 

no step trend or linear trend could be shown to be statistically 

significant for the north, although the south showed a mixture 

of an upward step trend accompanied by linear downtrends 

within the periods. In no case was a change identified that 

indicated an increasing rate of change over time, and no general pattern was identified of hydrologic conditions becoming 

“more extreme” over time.

Introduction

The U.S. Geological Survey (USGS) has been measuring 

and recording streamflow throughout the United States (U.S.) 

since the late 1800s. Long-term records of streamflow are 

invaluable because of the information that they contain about 

temporal changes in the discharge of streams and rivers, a 

major component of the hydrologic cycle. Long-term records 

are necessary to detect and quantify natural and anthropogenic effects on streamflow. Analysis of long-term streamflow 

records can reveal information about the response of streamflow to climate and weather, to changes in land use in the 

watershed, and to changes in withdrawals of stream water for 

various human uses, because the records integrate those complex and interacting physical processes. Analysis of multiple 

streamflow records in a region is a particularly powerful tool 

for determining regional trends that may be related to climate.

The topic of climate change and variability is full of 

uncertainty, and any climatic changes are likely to result 

in changes to the hydrologic cycle at various scales. Some 

potential consequences of climate change and variability are 

changes in water availability for municipal and industrial use, 

changes in water demand for irrigation, changes in water quality, increased threats to stormwater and wastewater infrastructure, and a global rise in sea level. The longer the period of 

record of streamflow that is available, the better able hydrologists are to determine trends in streamflow, because shorter 

records can be dominated by the “noise” of natural variability, 

as well as long-term persistence (see, for example, Cohn and 

Lins, 2005). Evaluation of the trends that have taken place up 

to the present is important for the following reasons: (1) attaining an understanding of natural variability and the persistence 

of changing hydrologic conditions; (2) developing accurate 

representations of streamflow that can be useful in design and 

planning models for water quality, water supply, flood hazard 

mitigation, and ecosystem protection; and (3) forming a body 

of knowledge that can be used in the evaluation of models that 

are designed to forecast future changes in streamflow.

Spatial and Temporal Trends in Runoff at Long-Term 

Streamgages within and near the Chesapeake Bay 

Watershed

By Karen C. Rice and Robert M. Hirsch
2 Spatial and Temporal Trends in Runoff at Long-Term Streamgages within and near the Chesapeake Bay Watershed

Eutrophication of coastal water bodies is a problem, both 

nationally (Bricker and others, 1999) and globally (Bricker 

and others, 2007). The water quality of Chesapeake Bay is 

threatened by excess nutrients (in particular, nitrogen and 

phosphorus) and sediments transported to the bay by runoff 

from the contributing watershed area. The amount and timing of streamflow to the bay are integral determinants of the 

amount of nutrients, sediments, and other dissolved constituents that are delivered to the bay. How, when, and where 

streamflow, and resulting water quality, might change in the 

future is of great interest to a wide variety of stakeholders. 

Understanding past and future changes in water quality is 

important but must be based on an understanding of past and 

future changes in streamflow.

A report by Karl and Knight (1998) documents an 

increase in precipitation across the U.S. during the 20th century, with winter precipitation only slightly increased but with 

more pronounced increases in the other seasons, in particular 

spring and fall. The report defines the six New England States, 

as well as New York, Pennsylvania, and Maryland, as being 

part of the Northeastern U.S.; Virginia is included as part of 

the Southeastern U.S. Karl and Knight (1998) document that 

precipitation has increased more in the Northeast than in the 

Southeast. Increased streamflow trends have been reported for 

the U.S. (Lins and Slack, 1999; McCabe and Wolock, 2002) 

and the New England States (Collins, 2009). Najjar and others (2009) report a summary of modeling studies that shows 

projections of streamflow in the Susquehanna River Basin 

and Mid-Atlantic area for the last quarter of the 21st century. 

These projections of annual streamflow change range from 

–25 to 33 percent (Najjar and others 2009). Another study for 

the Northeastern U.S. indicates that modeled streamflow will 

become more variable throughout the 21st century (Hayhoe 

and others, 2007). Finally, a state of the science review for 

Chesapeake Bay summarizes the wide range of projections 

for streamflow for the Chesapeake Bay watershed (Pyke and 

Najjar, 2008). On the basis of the uncertainties concerning 

projected streamflow in the region, a study of existing streamflow trends in the Chesapeake Bay watershed is needed.

The purposes of this study, conducted by the U.S. Geological Survey Environments Program and Hydrologic Network and Analysis Program in cooperation with the Virginia 

Department of Environmental Quality, were to: 

(1) compute and analyze long-term (80-year) trends in streamflow in 30 nontidal watersheds within and near the Chesapeake Bay watershed, (2) identify any spatial patterns in the 

trends, and (3) further explore major variations in the temporal 

trends over the 80-year record (1930–2010). The scope of 

this report is to present the results of the spatial and temporal 

analyses. Although this report does not address future changes 

to streamflow, the results should serve as a baseline that can 

be used to compare with hindcasts made by climate models to 

evaluate the capability of these models to accurately simulate 

the hydrologic changes that have taken place in the watershed 

over the last 80 years.

Study Area

The watershed that encompasses all streams that drain to 

Chesapeake Bay consists of 165,759 square kilometers (km2) 

and extends from New York to Virginia. The Chesapeake 

Bay watershed includes parts of New York, Pennsylvania, 

Delaware, Maryland, Virginia, and West Virginia, as well as 

Washington, D.C. (fig. 1). Parts of the physiographic provinces 

that lie within the bay watershed are the Appalachian Plateaus, 

the Valley and Ridge, the Blue Ridge, the Piedmont, and the 

Coastal Plain (Fenneman and Johnson, 1946). The major river 

basins that lie within the Chesapeake Bay watershed are the 

Susquehanna River, Western Shore, Patuxent River, Potomac 

River, Rappahannock River, York River, James River, and 

Eastern Shore (Phillips, 2007).

Data were analyzed from USGS streamgages located 

within and near the Chesapeake Bay watershed and having 

the longest continuous period of daily mean discharge record 

in common. A total of 23 nontidal streamgages within, and 

7 nontidal streamgages near, the Chesapeake Bay watershed 

were chosen for analysis (fig. 2). This subset of streamgages 

in the bay watershed was selected because most of the 

streamgages have continuous daily mean discharge data 

extending for at least 80 years. The 30 streamgages selected 

for this analysis have watersheds that range in area from 

303 to 62,419 km2 (table 1). The Susquehanna River and its 

tributaries drain nearly half of the Chesapeake Bay watershed; 

slightly more than half of the streamgages analyzed in this 

report are located in the Susquehanna River Basin (table 1). 

Within the dataset are several streamgages that lie upstream 

from other streamgages used in the analysis. Thus, a degree of 

redundancy is present in some of the results, but the difference in drainage area between upstream and downstream sites 

warrants the inclusion of both. Unfortunately, streamgages 

located in the Coastal Plain part of the bay watershed, including the Eastern Shore, have records of insufficient length to be 

included in this analysis.

Methods

Data were analyzed by comparing the numerical results 

of calculated flow statistics for the period of record, 

1930–2010, and by analyzing two subsets of the period of 

record, 1930–1969 and 1970–2010. Three annual streamflow 

statistics were analyzed in this report. They are measures of 

high flow, average flow, and low flow.

The high-flow statistic is the annual maximum 1-day 

streamflow for the water year (October 1–September 30). High 

flows are important because of flood-hazard conditions and 

the resulting contaminants that affect water quality. Sediment 

and phosphorus fluxes during the highest streamflow days can 

be a substantial part of the total annual flux, and thus changes 

in high streamflow conditions could be important to Chesapeake Bay water quality. From a high-flow perspective, the 

annual peak discharge (highest instantaneous discharge during 
Introduction 3

CHESAPEAKE BAY ATLANTIC OCEAN

Potomac

River

Potomac

River

Susquehanna

River

Juniata

River

Chemung

West

Branch

Susquehanna R.

River

Patuxent River

James

James

Appomattox

Pamunkey River

Mattaponi River

Rappahannock R.

York River

River

River

River

Choptank 

R.

Pocomoke

River

Chester R.

Cr. guinet do Cono

South Fork

North Fork

FALL

LINE

MARYLAND

NEW YORK

PENNSYLVANIA

DE

WEST

VIRGINIA

VIRGINIA

CHESAPEAKE BAY

WATERSHED

BOUNDARY

Shenandoah R.

Elmira

Scranton

Williamsport

Altoona

Harrisburg

York

Annapolis

Washington,

D.C.

Charlottesville

Richmond

Harrisonburg

Front

Royal

0 10 20 30 40 50 MILES

0 10 20 30 40 50 KILOMETERS

Base modified from NAD 1983 Albers Equal-area conic projection

76o

76o

76o

76o

42o 42o

78o

78o

40o 40o

80o

80o

38o

38o

Norfolk

Baltimore

Lancaster

Chickahominy River

Dragon Run

EXPLANATION

Physiographic province

Appalachian Plateaus

Valley and Ridge

Blue Ridge

Piedmont

Coastal Plain

Figure 1. Location of study area.
4 Spatial and Temporal Trends in Runoff at Long-Term Streamgages within and near the Chesapeake Bay Watershed

BLACK

CHENA

SCONK CHEMU

STOWA

TOWAN TUNKH

DRIFT LYCOM

SRENO

SWILK

SWILL

BUSHK

CLEAR SDANV

SBOWE

JUNIA

RAYST SHARR

PLUKE PPTRX

GOOSE

RAPPA

JCART

JBUCH

ROANO

NEWRI

Geographic Coordinate System, North American Datum 1983

REEDC HOLST

BANIS

ATLANTIC OCEAN

Chesapeake Bay

PENNSYLVANIA

OHIO

WEST VIRGINIA

Washington,

D.C.

VIRGINIA

NORTH CAROLINA

NEW JERSEY

DELAWARE

NEW YORK

MARYLAND

0 50 100 Kilometers

EXPLANATION

DRIFT

Chesapeake Bay basin

Analyzed streamgage

80°W 75°W

40°N

Figure 2. Locations of streamgages analyzed. Abbreviated names are listed in table 1.
Introduction 5

the year) or the 1-day maximum streamflow can be used. For 

watersheds of the size considered in this study, the annual 

maximum 1-day streamflow is highly correlated with the 

annual peak discharge. Thus, selecting the annual maximum 

1-day discharge as the variable to analyze allows the entire 

analysis to be based on the daily flow record, rather than some 

parts being based on peak flows and other parts on daily flows.

Daily mean streamflow is highly relevant to the water 

balance of the watershed, as mean streamflow integrates the 

effects of precipitation and evapotranspiration. Like the annual 

maximum 1-day streamflow statistic, daily mean streamflow 

also is computed on a water-year basis.

The low-flow statistic used is the annual 7-day minimum 

discharge, calculated for the climate year (April 1 through 

March 31). The 7-day minimum is used because of its relevance to regulations regarding water withdrawals and wastewater discharges. In addition to this relevance to regulatory 

criteria, the 7-day minimum may be a more robust indicator 

of low flow than the 1-day minimum. One-day minimums are 

more likely to be strongly influenced by short-term fluctuations due to the operations of small reservoirs in the watershed 

Table 1. Attributes associated with streamgages and their location, Chesapeake Bay watershed.

[Watersheds are listed from north to south. ID, identification number; latitude and longitude given in decimal degrees; km2, square kilometers; Br., branch; 

N.Y., New York; Pa., Pennsylvania; Md., Maryland; Va., Virginia]

Stream name and location Abbreviated 

name

Streamgage 

ID

North

latitude

West

longitude

Watershed 

area, km2 Major watershed

Black River near Boonville, N.Y. BLACK 04252500 43.51174 75.30656 787 Lake Ontario

Chenango River near Chenango Forks, N.Y. CHENA 01512500 42.21813 75.84825 3,841 Susquehanna

Susquehanna River at Conklin, N.Y. SCONK 01503000 42.03535 75.80297 5,781 Susquehanna

Chemung River at Chemung, N.Y. CHEMU 01531000 42.00230 76.63467 6,491 Susquehanna

Susquehanna River at Towanda, Pa. STOWA 01531500 41.76535 76.44077 20,194 Susquehanna

Towanda Creek near Monroeton, Pa. TOWAN 01532000 41.70702 76.48467 557 Susquehanna

Tunkhannock Creek near Tunkhannock, Pa. TUNKH 01534000 41.55841 75.89464 992 Susquehanna

Lycoming Creek near Trout Run, Pa. LYCOM 01550000 41.41841 77.03275 448 Susquehanna

Driftwood Branch Sinnemahoning Creek at 

Sterling Run, Pa.

DRIFT 01543000 41.41340 78.19695 704 Susquehanna

West Branch Susquehanna River at Renovo, Pa. SRENO 01545500 41.32451 77.75054 7,705 Susquehanna

Susquehanna River at Wilkes-Barre, Pa. SWILK 01536500 41.25091 75.88075 25,796 Susquehanna

West Br. Susquehanna River at Williamsport, Pa. SWILL 01551500 41.23619 76.99663 14,716 Susquehanna

Bush Kill at Shoemakers, Pa. BUSHK 01439500 41.08815 75.03767 303 Delaware

Clearfield Creek at Dimeling, Pa. CLEAR 01541500 40.97172 78.40585 961 Susquehanna

Susquehanna River at Danville, Pa. SDANV 01540500 40.95814 76.61912 29,060 Susquehanna

West Branch Susquehanna River at Bower, Pa. SBOWE 01541000 40.89701 78.67697 816 Susquehanna

Juniata River at Newport, Pa. JUNIA 01567000 40.47842 77.12915 8,687 Susquehanna

Susquehanna River at Harrisburg, Pa. SHARR 01570500 40.25481 76.88608 62,419 Susquehanna

Raystown Branch Juniata River at Saxton, Pa. RAYST 01562000 40.21591 78.26529 1,958 Susquehanna

North Branch Potomac River at Luke, Md.* PLUKE 01598500 39.47897 79.06378 1,052 Potomac

Potomac River at Point of Rocks, Md. PPTRX 01638500 39.27358 77.54311 24,996 Potomac

Goose Creek near Leesburg, Va. GOOSE 01644000 39.01955 77.57749 860 Potomac

Rappahannock River near Fredericksburg, Va. RAPPA 01668000 38.30846 77.52915 4,131 Rappahannock

James River at Cartersville, Va. JCART 02035000 37.67098 78.08583 16,193 James

James River at Buchanan, Va. JBUCH 02019500 37.53069 79.67893 5,369 James

Roanoke River at Roanoke, Va. ROANO 02055000 37.25847 79.93865 995 Albemarle Sound

New River at Radford, Va.* NEWRI 03171000 37.14167 80.56944 7,167 Kanawha

Reed Creek at Grahams Forge, Va. REEDC 03167000 36.93901 80.88730 668 Kanawha

North Fork Holston River near Saltville, Va. HOLST 03488000 36.89678 81.74623 572 Tennessee

Banister River at Halifax, Va. BANIS 02077000 36.77653 78.91584 1,417 Albemarle Sound

*

Streamgage excluded from the 1930–2010 analyses.
6 Spatial and Temporal Trends in Runoff at Long-Term Streamgages within and near the Chesapeake Bay Watershed

rather than the overall water balance in the watershed. The 

use of the climate year for low-flow statistics (rather than the 

water year) is a common practice in hydrology, because it 

minimizes the probability that individual drought events will 

span multiple years and thus be counted twice in the time 

series (Riggs, 1982, 1985; Gordon and others, 2004).

Seasonal trend analyses were performed on the full 

period of record. Seasons were defined as fall (September 

through November), winter (December through February), 

spring (March through May), and summer (June through 

August). The same three flow statistics that were calculated for 

the annual analysis were calculated for each season.

For the analysis of the spatial pattern of the trends, 

streamflow records for the 28 streamgages were analyzed for 

1930 through 2010, including annual data and seasonal data. 

To test for temporal trends, the 80-year record was divided 

into two subsets. Records for 28 streamgages were analyzed 

for 1930 through 1969 and records for 30 streamgages were 

analyzed for 1970 through 2010.

Time-Series Graphs

The analysis of long-term variation in streamflow 

characteristics used in this study builds on time-series smoothing methods that were pioneered by Cleveland (1979) and 

Cleveland and Devlin (1988). For any given time series, the 

graphs included in the appendix of this report show a scatterplot of runoff (Qi

) as a function of time (Ti), for i from one to 

n, where Qi is the i

th annual value of the streamflow statistic, 

expressed in millimeters per day, and Ti is the time value at the 

midpoint of the period over which the statistic is evaluated, 

expressed in years. For example, for a flow statistic computed 

for water year 1972, the Ti value is approximately 1972.25, 

which represents the decimal-year value of the half-way point 

in the 1972 water year.

In addition to showing the actual values of the annual 

or seasonal streamflow statistic, the graphs show a curve that 

represents a smoothed representation of the time series. The 

smoothing method used is based on locally weighted scatterplot smoothing (lowess) but with some particular features that 

are described below. The purpose of producing the smooth 

curves is an attempt to extract patterns of change that describe 

broad temporal-scale variations, at timespans of about a 

decade or more. Such curves are very resistant to the influence 

of 1 or 2 years with extremely high or low flows.

The term yi is the log-transformed value of the flow 

statistic:

y Q i i = ln( ) ,

where

ln is the natural logarithm function. 

If the flow statistic is equal to zero, Qi is replaced with a constant, set equal to 0.1 percent of the long-term daily mean discharge for the streamgage. The logarithm transformation was 

applied because streamflow data typically are highly skewed,

approximating a log-normal distribution in many cases. The 

logarithm transformation results in weighted regressions in 

which the residuals are more nearly normal, and thus individual extreme values do not exert a large amount of influence on 

the estimates. This results in a more robust smoothing process. 

It also means that the Qˆ

i

 values are more nearly an approximation of the median of the time series than they are an approximation of the mean. Helsel and Hirsch (1992, p. 254–260) 

provide additional discussion of transformation issues.

In log space, the smooth curve is defined by a series of 

n-weighted regressions on the dataset. The estimate, ŷi, of yi is 

defined as:

yˆi i = + β β 0 1i i •T for i =1, n, (1)

where:

0i is the estimated regression intercept for the 

regression model fitted for year i, and

1i is the estimated regression slope for the 

regression model fitted for year i.

The two regression coefficients, 0i and 1i , were 

computed from a weighted regression, where the weights 

are equal to 1 for the observation for the year in which the 

estimate is being made, and decay to 0 at a time separation 

of 30 years between a given observation and the time of the 

estimate. The specific weights are computed with the Tukey 

tri-cubed weight function (Tukey, 1977). The weight for the i

th

streamflow value in the computation of the smoothed value for 

the j

th year is:

w

d if d

if d

i j

i j i j

i j

,

, ,

,

= ( ) − ( ) ≤

≥











1 30 30

0 30

3 3

, (2)

where d T i j , = −i j T .

The shape of the weight function is such that all of the 

observations between 0 and 15 years before or after the year 

for which the estimate is being made have weights that are 

at least 67 percent as large as the largest weight. The largest 

weight is for the observation that is in the year for which the 

estimate is being made. For observations that are 25 years 

before or after the year for which the estimate is being made, 

the weight is only 7 percent of the maximum weight. At 30 

years, the weight is 0. The “half-window width,” in this case, 

30 years, was selected by visual examination of graphics for 

many alternatives. The half-window width was selected to be 

as narrow as possible, such that individual year-to-year oscillations are fully damped out. The smoothing process takes place 

on the full discharge record, not just the record shown in the 

graphs. Therefore, data prior to 1930, if available, were used 

to calculate the lowess line.
Spatial Trends In Runoff 7

The final step in producing the graphic of the smoothed 

annual values is the retransformation:

ˆQ y exp( ˆ ) i i = . (3)

Graphs showing time series with lowess trends for the 7-day 

minimum, mean, and the 1-day maximum for annual and seasonal data for each streamgage are included in the appendix.

Flow Statistics

A numerical basis for comparisons across various flow 

statistics, across various starting and ending years, and across 

the various streamgages used in the analysis is useful. To 

present the results in a manner that enhances comparability, changes are best expressed in terms of a percent change 

per year, such as percent change per decade for the indicated 

period. Because the watershed areas vary over three orders of 

magnitude (table 1), normalizing by watershed area is necessary so that depth of runoff at each streamgage can be compared, rather than discharge, which is determined largely by 

the size of the watershed. The trend slopes (described below) 

were used to identify general patterns over the broad Chesapeake Bay watershed region. No statistical significance levels 

(p-values) were calculated for any one streamgage, because 

the focus is on general patterns in the region, and trend significance can be overestimated if the data are serially correlated 

(Koutsoyiannis, 2003; Cohn and Lins, 2005), as is the case 

with the dataset. The units (the percent change per decade for 

the indicated period) reported for each streamgage take into 

account the length of record and the watershed area. Thus, the 

units give the most appropriate value for comparing spatial 

and temporal trends in streamflow across a region.

USGS streamflow data, provided in units of cubic 

feet per second, were downloaded from the National Water 

Information System (http://waterdata.usgs.gov/nwis). For this 

analysis, streamflow data were converted to runoff by dividing 

cubic feet per second by the watershed area and multiplying 

by conversion factors to obtain millimeters per day. Values in 

millimeters per day were multiplied by 365.25 to obtain millimeters per year, which is the unit shown on the graphs in the 

appendix.

The trend slopes were computed as:

ˆ ˆ

ˆ

Q Q

Q T T

end start

start end start

( ) − •

• − ( )

100

, (4)

where:

Qˆ end is the selected year index value (identified by 

the lowess line, in millimeters per year) of 

the ending year,

Tend (2010) and Qˆstart are the selected year index value of 

the starting year, and

Tstart (1930) is the comparison being made (1930–2010).

The difference multiplied by 100 yields the percent change in 

daily mean runoff over the selected period, which is divided 

by the number of decades between the start and end years, 

yielding a trend slope in percent change per decade. A positive trend slope is defined as a value greater than 1-percent 

increase per decade; a near-zero trend slope is defined as a 

value from –1- to 1-percent change per decade; and a negative trend slope is defined as a value greater than 1-percent 

decrease per decade. For the temporal analysis, where the 

dataset was divided into two subsets, the values for Tend were 

1969 and 2010, and the values for Tstart were 1930 and 1970, 

and the divisor was four for each subset.

Spatial Trends In Runoff

In this report, the period of record is defined as extending 

from 1930 through 2010. During this period, spatial trends in 

flow statistics were analyzed for 28 streamgages. The results 

indicate that the trend slopes tend to be of opposite signs in the 

northern part of the watershed compared to the southern part, 

or if of the same sign, of larger magnitude in the north relative 

to the south. Accordingly, the latitude 40.25 degrees (°) north 

was selected to differentiate between “north” and “south” 

for this study. A total of 18 streamgages are located north of 

40.25°, and 10 streamgages are located south of 40.25°.

Annual Flow Statistics

The focus of this section of the report is on the flow 

statistics that were calculated from the annual data at each of 

the streamgages, including the annual 7-day minimum runoff, 

the annual mean runoff, and the annual 1-day maximum 

runoff, for the full period of record, 1930 through 2010. Two 

streamgages, North Branch Potomac River at Luke, Maryland (Md.), and New River at Radford, Virginia (Va.), were 

excluded from this analysis because of an insufficient length 

of data record. Values of the trend slopes, in percent change 

per decade, are shown in table 2.

Annual 7-Day Minimum Runoff

Data from 28 streamgages were included in the analysis of 

the annual 7-day minimum runoff. A total of 21 streamgages 

showed positive slopes, 2 streamgages showed near-zero 

slopes, and 5 streamgages showed negative slopes (fig. 3). 

The average slope was 3.8 (table 3). All 5 of the streamgages 

showing negative slopes are located south of 40.25° north 

latitude, whereas north of 40.25° north latitude, all 

18 streamgages showed positive slopes (fig. 3; table 4).
8 Spatial and Temporal Trends in Runoff at Long-Term Streamgages within and near the Chesapeake Bay Watershed

Table 2. Results of annual and seasonal trend slopes for 1930–2010.

[ID, identification number; trend slope units in percent change per decade]

Abbreviated 

name of 

streamgage

Streamgage

ID

7-day 

minimum Mean 1-day maximum

Annual

BLACK 04252500 15.0 4.3 2.9

CHENA 01512500 3.9 1.8 -0.5

SCONK 01503000 3.4 1.5 1.3

CHEMU 01531000 9.0 1.7 -1.4

STOWA 01531500 4.0 2.0 1.1

TOWAN 01532000 4.2 0.6 -0.1

TUNKH 01534000 6.7 3.4 4.4

LYCOM 01550000 1.5 0.9 2.8

DRIFT 01543000 2.6 0.3 3.0

SRENO 01545500 6.6 0.0 -2.2

SWILK 01536500 5.7 2.6 1.5

SWILL 01551500 3.9 -0.2 -0.9

BUSHK 01439500 2.2 2.4 5.6

CLEAR 01541500 12.4 0.0 -1.1

SDANV 01540500 3.8 2.2 1.3

SBOWE 01541000 10.4 -0.8 -1.0

JUNIA 01567000 3.8 0.3 -2.3

SHARR 01570500 3.8 1.4 0.9

RAYST 01562000 -1.0 0.0 -0.3

PPTRX 01638500 3.1 0.3 -1.3

GOOSE 01644000 15.0 4.4 6.7

RAPPA 01668000 -7.7 -1.0 -1.2

JCART 02035000 -3.3 -2.1 -2.9

JBUCH 02019500 2.4 -1.2 -2.4

ROANO 02055000 -3.7 -2.6 -3.1

REEDC 03167000 0.7 -0.6 -2.0

HOLST 03488000 -0.6 -1.6 -0.3

BANIS 02077000 -2.1 -1.9 -3.3

Fall

BLACK 04252500 8.9 10.2 9.4

CHENA 01512500 3.5 6.1 5.3

SCONK 01503000 2.7 3.5 0.9

CHEMU 01531000 11.0 6.0 9.8

STOWA 01531500 3.6 4.4 4.1

TOWAN 01532000 5.2 6.1 4.2

TUNKH 01534000 7.3 7.4 3.8

LYCOM 01550000 3.3 4.0 1.6

DRIFT 01543000 4.8 5.2 10.5

SRENO 01545500 7.3 4.5 8.8

SWILK 01536500 6.0 7.1 7.0

SWILL 01551500 5.1 4.2 7.4

BUSHK 01439500 4.1 12.3 7.6

CLEAR 01541500 11.5 2.5 4.5

SDANV 01540500 3.4 7.6 6.8

SBOWE 01541000 8.5 2.3 3.4

JUNIA 01567000 4.4 3.3 5.8

SHARR 01570500 5.1 5.3 4.8

RAYST 01562000 -1.1 1.0 4.0

Abbreviated 

name of 

streamgage

Streamgage

ID

7-day 

minimum Mean 1-day maximum

PPTRX 01638500 3.9 2.2 -1.7

GOOSE 01644000 27.9 21.1 27.3

RAPPA 01668000 -5.5 0.7 3.2

JCART 02035000 -2.2 1.4 4.9

JBUCH 02019500 2.2 3.0 3.9

ROANO 02055000 -3.5 -0.2 3.3

REEDC 03167000 -0.2 -0.4 -1.0

HOLST 03488000 -0.7 -0.5 -1.9

BANIS 02077000 2.3 4.0 16.8

Winter

BLACK 04252500 3.9 6.7 10.9

CHENA 01512500 8.4 6.7 5.5

SCONK 01503000 7.9 5.8 8.1

CHEMU 01531000 17.6 10.8 10.0

STOWA 01531500 11.3 7.6 9.8

TOWAN 01532000 11.2 8.8 11.1

TUNKH 01534000 16.0 10.0 9.3

LYCOM 01550000 12.9 9.7 15.5

DRIFT 01543000 7.0 4.8 12.0

SRENO 01545500 10.5 4.5 5.7

SWILK 01536500 13.3 9.0 10.6

SWILL 01551500 10.6 5.2 8.3

BUSHK 01439500 8.8 7.1 11.2

CLEAR 01541500 14.5 3.0 3.1

SDANV 01540500 12.8 7.2 8.5

SBOWE 01541000 12.8 1.5 3.8

JUNIA 01567000 8.7 3.4 0.9

SHARR 01570500 12.0 6.8 7.0

RAYST 01562000 4.2 1.4 -1.1

PPTRX 01638500 3.0 0.7 -2.3

GOOSE 01644000 18.7 6.9 3.5

RAPPA 01668000 0.2 -1.1 -0.3

JCART 02035000 -0.5 -2.4 -1.9

JBUCH 02019500 0.9 -2.9 -4.6

ROANO 02055000 1.5 -3.5 -5.4

REEDC 03167000 1.0 -0.3 -2.5

HOLST 03488000 -1.0 -2.9 -3.4

BANIS 02077000 2.7 1.5 4.2

Spring

BLACK 04252500 4.5 0.3 1.7

CHENA 01512500 0.6 -1.7 -1.7

SCONK 01503000 1.0 -1.4 0.4

CHEMU 01531000 2.9 -1.9 -1.3

STOWA 01531500 1.8 -1.1 -0.1

TOWAN 01532000 2.6 -2.9 -2.8

TUNKH 01534000 2.7 -1.1 1.7

LYCOM 01550000 3.4 -3.0 -1.8

DRIFT 01543000 0.4 -2.6 -0.9

SRENO 01545500 1.1 -2.5 -3.3
Spatial Trends In Runoff 9

Table 2. Results of annual and seasonal trend slopes for 

1930–2010.—Continued

[ID, identification number; trend slope units in percent change per decade]

Abbreviated 

name of 

streamgage

Streamgage

ID

7-day 

minimum Mean 1-day maximum

SWILK 01536500 1.5 -1.3 -0.4

SWILL 01551500 0.7 -3.1 -2.9

BUSHK 01439500 -0.3 -1.6 1.5

CLEAR 01541500 3.5 -1.8 -4.5

SDANV 01540500 4.1 0.0 0.1

SBOWE 01541000 3.7 -2.2 -3.9

JUNIA 01567000 0.2 -1.3 -1.9

SHARR 01570500 1.6 -1.9 -1.2

RAYST 01562000 1.2 0.1 1.0

PPTRX 01638500 0.9 0.5 1.7

GOOSE 01644000 2.5 3.1 3.2

RAPPA 01668000 -2.3 -0.1 4.4

JCART 02035000 -3.0 -2.0 -3.1

JBUCH 02019500 -0.9 -0.9 -1.2

ROANO 02055000 -2.0 -2.3 -0.1

REEDC 03167000 0.6 -0.1 4.0

HOLST 03488000 -1.1 -1.0 3.5

BANIS 02077000 -1.2 -2.2 -3.8

Summer

BLACK 04252500 14.7 11.0 14.5

CHENA 01512500 4.4 5.7 5.3

SCONK 01503000 4.4 4.9 5.8

CHEMU 01531000 7.4 4.1 3.0

STOWA 01531500 3.8 4.4 4.5

TOWAN 01532000 0.7 -1.4 -2.3

TUNKH 01534000 5.9 5.3 9.1

LYCOM 01550000 -0.1 -1.0 -2.8

DRIFT 01543000 3.2 0.2 -4.4

SRENO 01545500 5.1 -1.0 -4.4

SWILK 01536500 3.5 4.6 3.3

SWILL 01551500 1.9 -1.7 -5.2

BUSHK 01439500 -0.6 1.0 0.9

CLEAR 01541500 7.1 -0.2 -3.1

SDANV 01540500 2.7 3.7 2.3

SBOWE 01541000 9.2 -1.1 -5.6

JUNIA 01567000 1.8 -1.0 -0.8

SHARR 01570500 1.3 0.6 -1.6

RAYST 01562000 -1.7 -1.9 -2.7

PPTRX 01638500 -0.1 -1.2 -2.4

GOOSE 01644000 19.4 10.1 9.3

RAPPA 01668000 -7.8 -4.4 -2.2

JCART 02035000 -3.6 -4.5 -6.2

JBUCH 02019500 2.8 -0.9 -5.1

ROANO 02055000 -3.5 -3.0 -4.8

REEDC 03167000 0.4 -0.2 -0.3

HOLST 03488000 -0.7 -0.3 -1.9

BANIS 02077000 -4.1 -6.0 -6.5

-10

-5

0

5

10

15

BLACK

CHENA

SCONK

CHEMU

STOWA

TOWAN

TUNKH

LYCOM

DRIFT

SRENO

SWILK

SWILL

BUSHK

CLEAR

SDANV

SBOWE

JUNIA

SHARR

RAYST

PPTRX

GOOSE

RAPPA

JCART

JBUCH

ROANO

REEDC

HOLST

BANIS

Trend slope, in percent change per decade

40.25 degreesnorth latitude

Figure 3. Spatial trend in annual 7-day minimum runoff, 

1930–2010. Streamgages are listed in order from north (left side of 

graph) to south (right side of graph) with the dashed line indicating 

the position of 40.25 degrees north latitude that separates the 10 

streamgages in the “south” subset from the 18 streamgages in the 

“north” subset.

Table 3. Summary of results of annual and seasonal trends in 

data for 1930–2010.

[n, number of streamgages; >, greater than; <, less than; trend slope units in 

percent change per decade]

Flow 

statistic

n, positive 

slope (> 1)

n, near-zero

slope (-1 to 1)

n, negative 

slope (< -1)

Average 

slope

Annual

7-day minimum 21 2 5 3.8

Mean 11 11 6 0.6

1-day maximum 10 6 12 0.2

Fall

7-day minimum 22 2 4 4.6

Mean 24 4 0 4.8

1-day maximum 24 1 3 5.9

Winter

7-day minimum 24 3 1 8.3

Mean 21 2 5 4.1

1-day maximum 19 2 7 4.9

Spring

7-day minimum 15 8 5 1.1

Mean 1 7 20 -1.3

1-day maximum 9 6 13 -0.4

Summer

7-day minimum 17 6 5 2.8

Mean 10 6 12 0.9

1-day maximum 9 3 16 -0.2
10 Spatial and Temporal Trends in Runoff at Long-Term Streamgages within and near the Chesapeake Bay Watershed

Annual Mean Runoff

Of the 28 streamgages that were analyzed for annual 

mean runoff, 11 showed positive slopes, 11 showed near-zero 

slopes, and 6 showed negative slopes (fig. 4). The average 

slope was 0.6 (table 3). South of 40.25° north latitude, 6 of 

the 10 streamgages showed negative slopes, and the majority 

located north of that latitude (10 out of 18) showed positive 

slopes (fig. 4; table 4).

Annual 1-Day Maximum Runoff

Of the 28 streamgages that were analyzed for the annual 

1-day maximum runoff, 10 showed positive slopes, 6 showed 

near-zero slopes, and 12 showed negative slopes (fig. 5). The 

average slope was 0.2 (table 3). South of 40.25° north latitude, 

7 of 10 streamgages showed negative slopes (fig. 5; table 4). 

North of 40.25° north latitude, half of the streamgages showed 

positive slopes (fig. 5; table 4).

Seasonal Flow Statistics

The focus of this section of the report is on the flow 

statistics that were calculated from the seasonal data at each 

of the streamgages, including the 7-day minimum runoff, 

the mean runoff, and the 1-day maximum runoff for each 

season. Data were analyzed from 1930 through 2010. Two 

streamgages, North Branch Potomac River at Luke, Md., and 

New River at Radford, Va., were excluded from this analysis 

because of insufficient data. Values of the slopes, in percent 

change per decade, are shown in table 3.

Table 4. Summary of results of annual and seasonal trends in 

data for 1930-2010 north and south of 40.25 degrees north latitude.

[n, number of streamgages; >, greater than; <, less than; trend slope units in 

percent change per decade; °, degrees]

Flow 

statistic

n, positive 

slope (> 1)

n, near-zero

slope (-1 to 1)

n, negative 

slope (< -1)

Average 

slope

North of 40.25° north latitude, 18 streamgages

Annual

7-day minimum 18 0 0 5.7

Mean 10 8 0 1.4

1-day maximum 9 4 5 0.8

Fall

7-day minimum 18 0 0 5.9

Mean 18 0 0 5.7

1-day maximum 17 1 0 5.9

Winter

7-day minimum 18 0 0 11.1

Mean 18 0 0 6.6

1-day maximum 17 1 0 8.4

Spring

7-day minimum 13 5 0 2.0

Mean 0 2 16 -1.7

1-day maximum 3 5 10 -1.2

Summer

7-day minimum 15 3 0 4.2

Mean 9 3 6 2.1

1-day maximum 8 2 8 1.0

South of 40.25° north latitude, 10 streamgages

Annual

7-day minimum 3 2 5 0.3

Mean 1 3 6 -0.6

1-day maximum 1 2 7 -1.0

Fall

7-day minimum 4 2 4 2.3

Mean 6 4 0 3.2

1-day maximum 7 0 3 5.9

Winter

7-day minimum 6 3 1 3.1

Mean 3 2 5 -0.3

1-day maximum 2 1 7 -1.4

Spring

7-day minimum 2 3 5 -0.5

Mean 1 5 4 -0.5

1-day maximum 6 1 3 1.0

Summer

7-day minimum 2 3 5 0.1

Mean 1 3 6 -1.2

1-day maximum 1 1 8 -2.3

BLACK

CHENA

SCONK

CHEMU

STOWA

TOWAN

TUNKH

LYCOM

DRIFT

SRENO

SWILK

SWILL

BUSHK

CLEAR

SDANV

SBOWE

JUNIA

SHARR

RAYST

PPTRX

GOOSE

RAPPA

JCART

JBUCH

ROANO

REEDC

HOLST

BANIS

Trend slope, in percent change per decade

40.25 degreesnorth latitude

-3

-2

-1

0

1

2

3

4

5

Figure 4. Spatial trend in annual mean runoff, 1930–2010. 

Streamgages are listed in order from north (left side of graph) 

to south (right side of graph) with the dashed line indicating the 

position of 40.25 degrees north latitude that separates the 10 

streamgages in the “south” subset from the 18 streamgages in the 

“north” subset.
Spatial Trends In Runoff 11

The 7-Day Minimum Runoff

The 7-day minimum runoff for fall was analyzed for 

28 streamgages. Results were mostly positive with 

22 streamgages showing positive slopes, 2 with near-zero 

slopes, and 4 with negative slopes (fig. 6). The average 

slope was 4.6 (table 3). North of 40.25° north latitude, all 

18 streamgages showed positive slopes (fig. 6; table 4). The 

4 streamgages showing negative slopes are located south of 

40.25° north latitude (fig. 6; table 4).

The 7-day minimum runoff for winter was analyzed for 

28 streamgages. The record for Goose Creek near Leesburg, 

Va., however, is missing data for the full 3 months of the winter of 1929 through 1930. Results were overall positive with 

24 streamgages showing positive slopes, 3 streamgages with 

near-zero slopes, and 1 streamgage with a negative slope 

(fig. 7). The average slope was 8.3 (table 3). The 1 streamgage 

with a negative slope is located south of 40.25° north latitude 

(fig. 7; table 4).

The 7-day minimum runoff for spring was analyzed for 

28 streamgages. Results were mostly positive with 

15 streamgages showing positive slopes, 8 streamgages with 

near-zero slopes, and 5 with negative slopes (fig. 8). The 

average slope was 1.1 (table 3). All 5 of the streamgages with 

negative slopes are located south of 40.25° north latitude 

(fig. 8; table 4).

The 7-day minimum runoff for summer was analyzed for 

28 streamgages. Results were mostly positive with 

17 streamgages showing positive slopes, 6 streamgages with 

near-zero slopes, and 5 with negative slopes (fig. 9). The 

average slope was 2.8 (table 3). All 5 of the streamgages with 

negative slopes are located south of 40.25° north latitude 

(fig. 9; table 4).

BLACK

CHENA

SCONK

CHEMU

STOWA

TOWAN

TUNKH

LYCOM

DRIFT

SRENO

SWILK

SWILL

BUSHK

CLEAR

SDANV

SBOWE

JUNIA

SHARR

RAYST

PPTRX

GOOSE

RAPPA

JCART

JBUCH

ROANO

REEDC

HOLST

BANIS

Trend slope, in percent change per decade

40.25 degreesnorth latitude

-4

-2

0

2

4

6

8

Figure 5. Spatial trend in annual 1-day maximum runoff, 

1930–2010. Streamgages are listed in order from north (left side of 

graph) to south (right side of graph) with the dashed line indicating 

the position of 40.25 degrees north latitude that separates the 10 

streamgages in the “south” subset from the 18 streamgages in the 

“north” subset.

-10

-5

0

5

10

15

20

25

30

BLACK

CHENA

SCONK

CHEMU

STOWA

TOWAN

TUNKH

LYCOM

DRIFT

SRENO

SWILK

SWILL

BUSHK

CLEAR

SDANV

SBOWE

JUNIA

SHARR

RAYST

PPTRX

GOOSE

RAPPA

JCART

JBUCH

ROANO

REEDC

HOLST

BANIS

Trend slope, in percent change per decade

40.25 degreesnorth latitude

Figure 6. Spatial trend in fall 7-day minimum runoff, 1930–2010. 

Streamgages are listed in order from north (left side of graph) 

to south (right side of graph) with the dashed line indicating the 

position of 40.25 degrees north latitude that separates the 10 

streamgages in the “south” subset from the 18 streamgages in the 

“north” subset.

-5

0

5

10

15

20

BLACK

CHENA

SCONK

CHEMU

STOWA

TOWAN

TUNKH

LYCOM

DRIFT

SRENO

SWILK

SWILL

BUSHK

CLEAR

SDANV

SBOWE

JUNIA

SHARR

RAYST

PPTRX

GOOSE

RAPPA

JCART

JBUCH

ROANO

REEDC

HOLST

BANIS

Trend slope, in percent change per decade

40.25 degreesnorth latitude

Figure 7. Spatial trend in winter 7-day minimum runoff, 

1930–2010. Streamgages are listed in order from north (left side of 

graph) to south (right side of graph) with the dashed line indicating 

the position of 40.25 degrees north latitude that separates the 10 

streamgages in the “south” subset from the 18 streamgages in the 

“north” subset.
12 Spatial and Temporal Trends in Runoff at Long-Term Streamgages within and near the Chesapeake Bay Watershed

Mean Runoff

Fall mean runoff was analyzed at 28 streamgages. Results 

were overall positive with 24 streamgages showing positive 

slopes and 4 with near-zero slopes; no negative slopes were 

observed (fig. 10). The average slope was 4.8 (table 3). The 

4 streamgages with near-zero slopes are located south of 

40.25° north latitude (fig. 10; table 4).

Results for 28 streamgages for winter mean runoff were 

mostly positive, with 21 positive slopes, 2 with near-zero 

slopes, and 5 with negative slopes (fig. 11). The average slope 

was 4.1 (table 3). The 5 streamgages with negative slopes are 

located south of 40.25° north latitude (fig. 11; table 4).

BLACK

CHENA

SCONK

CHEMU

STOWA

TOWAN

TUNKH

LYCOM

DRIFT

SRENO

SWILK

SWILL

BUSHK

CLEAR

SDANV

SBOWE

JUNIA

SHARR

RAYST

PPTRX

GOOSE

RAPPA

JCART

JBUCH

ROANO

REEDC

HOLST

BANIS

Trend slope, in percent change per decade

40.25 degreesnorth latitude

-3

-2

-1

0

1

2

3

4

5

Figure 8. Spatial trend in spring 7-day minimum runoff, 

1930–2010. Streamgages are listed in order from north (left side of 

graph) to south (right side of graph) with the dashed line indicating 

the position of 40.25 degrees north latitude that separates the 10 

streamgages in the “south” subset from the 18 streamgages in the 

“north” subset. BLACK CHENA SCONK CHEMU

STOWA

TOWAN

TUNKH

LYCOM

DRIFT

SRENO

SWILK

SWILL

BUSHK

CLEAR

SDANV

SBOWE

JUNIA

SHARR

RAYST

PPTRX

GOOSE

RAPPA

JCART

JBUCH

ROANO

REEDC

HOLST

BANIS

Trend slope, in percent change per decade

40.25 degreesnorth latitude

-10

-5

0

5

10

15

20

Figure 9. Spatial trend in summer 7-day minimum runoff, 

1930–2010. Streamgages are listed in order from north (left side of 

graph) to south (right side of graph) with the dashed line indicating 

the position of 40.25 degrees north latitude that separates the 10 

streamgages in the “south” subset from the 18 streamgages in the 

“north” subset.

-2

0

2

4

6

8

10

12

14

16

18

20

22

BLACK

CHENA

SCONK

CHEMU

STOWA

TOWAN

TUNKH

LYCOM

DRIFT

SRENO

SWILK

SWILL

BUSHK

CLEAR

SDANV

SBOWE

JUNIA

SHARR

RAYST

PPTRX

GOOSE

RAPPA

JCART

JBUCH

ROANO

REEDC

HOLST

BANIS

Trend slope, in percent change per decade

40.25 degreesnorth latitude

Figure 10. Spatial trend in fall mean runoff, 1930–2010. 

Streamgages are listed in order from north (left side of graph) 

to south (right side of graph) with the dashed line indicating the 

position of 40.25 degrees north latitude that separates the 10 

streamgages in the “south” subset from the 18 streamgages in the 

“north” subset. BLACK CHENA SCONK CHEMU

STOWA

TOWAN

TUNKH

LYCOM

DRIFT

SRENO

SWILK

SWILL

BUSHK

CLEAR

SDANV

SBOWE

JUNIA

SHARR

RAYST

PPTRX

GOOSE

RAPPA

JCART

JBUCH

ROANO

REEDC

HOLST

BANIS

Trend slope, in percent change per decade

40.25 degreesnorth latitude

-4

-2

0

2

4

6

8

10

12

Figure 11. Spatial trend in winter mean runoff, 1930–2010. 

Streamgages are listed in order from north (left side of graph) 

to south (right side of graph) with the dashed line indicating the 

position of 40.25 degrees north latitude that separates the 10 

streamgages in the “south” subset from the 18 streamgages in the 

“north” subset.
Spatial Trends In Runoff 13

Results for 28 streamgages for spring mean runoff were 

mostly negative. Only 1 streamgage showed a positive slope, 

7 had near-zero slopes, and 20 had negative slopes (fig. 

12). The average slope was –1.3 (table 3). A total of 16 

streamgages with negative slopes are located north of 40.25° 

north latitude (fig. 12; table 4).

Summer mean runoff was analyzed at 28 streamgages. 

Results were mixed: 10 streamgages had positive slopes, 6 had 

a near-zero slope, and 12 streamgages had negative slopes

(fig. 13). The average slope was 0.9 (table 3). A total of 6 

of the 10 streamgages located south of 40.25° north latitude 

showed negative slopes; north of that latitude, 9 of the 

18 streamgages showed positive slopes (fig. 13; table 4).

The 1-Day Maximum Runoff

The 1-day maximum runoff for fall was analyzed for 

28 streamgages. Results were overall positive: 24 streamgages 

showed positive slopes, 1 had a near-zero slope, and 

3 streamgages had negative slopes (fig. 14). The average slope 

was 5.9 (table 3). The 3 streamgages with negative slopes are 

located south of 40.25° north latitude (fig. 14; table 4).

The 1-day maximum runoff for winter was analyzed for 

28 streamgages. A total of 19 of the 28 streamgages showed 

positive slopes, 2 had near-zero slopes, and 7 streamgages had 

negative slopes (fig. 15). The average slope was 4.9 (table 3). 

The 7 streamgages with negative slopes are located south of 

40.25° north latitude (fig. 15; table 4).

The 1-day maximum runoff for spring was analyzed for 

28 streamgages. Results were mostly negative: 9 streamgages 

had positive slopes, 6 had near-zero slopes, and 

13 streamgages had negative slopes (fig. 16). The average 

slope was –0.4 (table 3). A total of 10 of the 13 streamgages 

with negative slopes are located north of 40.25° north latitude 

(fig. 16; table 4).

BLACK

CHENA

SCONK

CHEMU

STOWA

TOWAN

TUNKH

LYCOM

DRIFT

SRENO

SWILK

SWILL

BUSHK

CLEAR

SDANV

SBOWE

JUNIA

SHARR

RAYST

PPTRX

GOOSE

RAPPA

JCART

JBUCH

ROANO

REEDC

HOLST

BANIS

Trend slope, in percent change per decade

40.25 degreesnorth latitude

-4

-3

-2

-1

0

1

2

3

4

Figure 12. Spatial trend in spring mean runoff, 1930–2010. 

Streamgages are listed in order from north (left side of graph) 

to south (right side of graph) with the dashed line indicating the 

position of 40.25 degrees north latitude that separates the 10 

streamgages in the “south” subset from the 18 streamgages in the 

“north” subset.

BLACK

CHENA

SCONK

CHEMU

STOWA

TOWAN

TUNKH

LYCOM

DRIFT

SRENO

SWILK

SWILL

BUSHK

CLEAR

SDANV

SBOWE

JUNIA

SHARR

RAYST

PPTRX

GOOSE

RAPPA

JCART

JBUCH

ROANO

REEDC

HOLST

BANIS

Trend slope, in percent change per decade

40.25 degreesnorth latitude

-4

-6

-2

0

2

4

6

8

12

10

Figure 13. Spatial trend in summer mean runoff, 1930–2010. 

Streamgages are listed in order from north (left side of graph) 

to south (right side of graph) with the dashed line indicating the 

position of 40.25 degrees north latitude that separates the 10 

streamgages in the “south” subset from the 18 streamgages in the 

“north” subset.

Figure 14. Spatial trend in fall 1-day maximum runoff, 1930–2010.

Streamgages are listed in order from north (left side of graph) 

to south (right side of graph) with the dashed line indicating the 

position of 40.25 degrees north latitude that separates the 10 

streamgages in the “south” subset from the 18 streamgages in the 

“north” subset. BLACK CHENA SCONK CHEMU

STOWA

TOWAN

TUNKH

LYCOM

DRIFT

SRENO

SWILK

SWILL

BUSHK

CLEAR

SDANV

SBOWE

JUNIA

SHARR

RAYST

PPTRX

GOOSE

RAPPA

JCART

JBUCH

ROANO

REEDC

HOLST

BANIS

Trend slope, in percent change per decade

40.25 degreesnorth latitude

-5

0

5

10

15

20

30

25
14 Spatial and Temporal Trends in Runoff at Long-Term Streamgages within and near the Chesapeake Bay Watershed

The 1-day maximum runoff for summer was analyzed 

for 28 streamgages. Results were mostly negative: 

9 streamgages had positive slopes, 3 had near-zero slopes, 

and 16 streamgages had negative slopes (fig. 17). The average 

slope was –0.2 (table 3). A total of 8 of the 9 streamgages with 

positive slopes are located north of 40.25° north latitude 

(fig. 17, table 4).

Discussion Of Annual And Seasonal 

Flow Statistics

The flow statistics indicate that the 7-day minimum 

runoff, the mean runoff, and the 1-day maximum runoff generally have increased from 1930 through 2010. An accounting of 

the number of streamgages with positive, negative, and nearzero slopes shows that the majority of the slopes at the 

28 streamgages were positive (table 3). In addition, the majority of the average slopes (12 out of 15) for each statistic were 

positive (table 3). These results of generally positive trends in 

streamflow in the Chesapeake Bay region are in accordance 

with previous assessments of streamflow trends in the U.S. 

(Lins and Slack, 1999; McCabe and Wolock, 2002) and in the 

New England States (Collins, 2009). Because the northeastern 

region of Karl and Knight (1998) does not include the southern part of the Chesapeake Bay study area, the documented 

increases in precipitation are not directly comparable to the 

runoff results presented here. Nevertheless, the general pattern of precipitation increase supports the general pattern of 

runoff increase, particularly in the northern part of the study 

area. Analysis of the effects of urbanization on streamflow lies 

beyond the scope of this report. Some sites, such as Goose 

Creek near Leesburg, Va., however, yielded anomalous results, 

suggesting that in some cases urbanization may be a more 

powerful influence on streamflow trends than is the climate.

In general, the average 7-day minimum and the average 

1-day maximum slopes were greater than the average mean 

slopes (table 3). On an annual basis, the absolute difference 

between the average slopes of the 7-day minimum and the 

BLACK

CHENA

SCONK

CHEMU

STOWA

TOWAN

TUNKH

LYCOM

DRIFT

SRENO

SWILK

SWILL

BUSHK

CLEAR

SDANV

SBOWE

JUNIA

SHARR

RAYST

PPTRX

GOOSE

RAPPA

JCART

JBUCH

ROANO

REEDC

HOLST

BANIS

Trend slope, in percent change per decade

40.25 degreesnorth latitude

-10

-5

0

5

10

15

20

Figure 15. Spatial trend in winter 1-day maximum runoff, 

1930–2010. Streamgages are listed in order from north (left side of 

graph) to south (right side of graph) with the dashed line indicating 

the position of 40.25 degrees north latitude that separates the 10 

streamgages in the “south” subset from the 18 streamgages in the 

“north” subset. BLACK CHENA SCONK CHEMU

STOWA

TOWAN

TUNKH

LYCOM

DRIFT

SRENO

SWILK

SWILL

BUSHK

CLEAR

SDANV

SBOWE

JUNIA

SHARR

RAYST

PPTRX

GOOSE

RAPPA

JCART

JBUCH

ROANO

REEDC

HOLST

BANIS

Trend slope, in percent change per decade

40.25 degreesnorth latitude

-3

-4

-5

0

-2

-1

4

3

1

2

5

Figure 16. Spatial trend in spring 1-day maximum runoff, 

1930–2010. Streamgages are listed in order from north (left side of 

graph) to south (right side of graph) with the dashed line indicating 

the position of 40.25 degrees north latitude that separates the 10 

streamgages in the “south” subset from the 18 streamgages in the 

“north” subset.

-10

-5

0

5

10

15

BLACK

CHENA

SCONK

CHEMU

STOWA

TOWAN

TUNKH

LYCOM

DRIFT

SRENO

SWILK

SWILL

BUSHK

CLEAR

SDANV

SBOWE

JUNIA

SHARR

RAYST

PPTRX

GOOSE

RAPPA

JCART

JBUCH

ROANO

REEDC

HOLST

BANIS

Trend slope, in percent change per decade

40.25 degreesnorth latitude

Figure 17. Spatial trend in summer 1-day maximum runoff, 

1930–2010. Streamgages are listed in order from north (left side of 

graph) to south (right side of graph) with the dashed line indicating 

the position of 40.25 degrees north latitude that separates the 10 

streamgages in the “south” subset from the 18 streamgages in the 

“north” subset.
Temporal Trends In Runoff 15

mean was greater than the absolute difference between the 

average slopes of the mean and the 1-day maximum. This 

suggests that flows generally have become less variable; that 

is, the low flows have increased and moved closer to the mean 

flows, but the high flows have not moved an equal magnitude 

away from the mean flows. These results are in contrast to the 

modeling results of Hayhoe and others (2007), which predict 

that flow will become more variable throughout this century.

A notable difference is in the number of positive 

slopes among streamgages located in the north compared to 

streamgages located in the south (table 4). On an annual basis, 

in the north, there were 37 (out of 54) positive slopes (69 percent) and 5 (out of 54) negative slopes (9 percent), whereas in 

the south, there were 5 (out of 30) positive slopes (17 percent) 

and 18 (out of 30) negative slopes (60 percent). In addition, 

the magnitude of the average slopes in the north was greater 

than that of the average slopes in the south (table 4).

The absolute difference between the average slopes of the 

7-day minimum and the mean was greater in the north than in 

the south (table 4). Likewise, the absolute difference between 

the average slopes of the mean and the 1-day maximum was 

slightly greater in the north than in the south. This suggests 

that, on an annual basis, flows in the north have become less 

variable than flows in the south. The seasonal statistics suggest 

that in the north, the 1-day maximum flows were higher in 

the winter than in the other seasons, whereas in the south, the 

1-day maximum flows were higher in the fall than in the other 

seasons. On a seasonal basis, the absolute difference between 

the average slopes of the 7-day minimum and the mean for 

streamgages in the north was greater than in the south for winter, spring, and summer; for fall, the absolute difference was 

slightly greater in the south. The absolute difference between 

the average slopes of the mean and the 1-day maximum was 

greater in the north for winter but was greater in the south for 

fall, spring, and summer.

Temporal Trends In Runoff

The analysis of data for the period 1930 through 2010 

was further explored by dividing the period into two subperiods: 1930 through 1969 and 1970 through 2010. The two 

subperiods were chosen because McCabe and Wolock (2002) 

identified a step increase in U.S. river flows in 1970, which 

Table 5. Results of annual and seasonal trend slopes for 1930–1969 and 1970–2010.—Continued

[ID, identification number; trend slope units in percent change per decade; —, insufficient data]

Abbreviated name of 

streamgage

Streamgage

ID

1930-1969 1970-2010

7-day minimum Mean 1-day maximum 7-day minimum Mean 1-day maximum

Annual

BLACK 04252500 26.0 2.3 2.5 2.0 5.7 3.0

CHENA 01512500 -2.0 -1.1 -4.3 10.7 4.8 4.0

SCONK 01503000 -5.7 -1.0 -3.2 16.0 4.2 6.6

CHEMU 01531000 4.1 0.6 -2.6 12.0 2.7 -0.2

STOWA 01531500 -3.6 0.3 -0.4 13.6 3.7 2.5

TOWAN 01532000 -2.5 0.0 -0.6 12.2 1.2 0.4

TUNKH 01534000 0.3 0.4 2.8 13.0 6.2 5.4

LYCOM 01550000 -2.5 2.3 3.5 6.2 -0.4 1.9

DRIFT 01543000 -0.2 -0.8 -0.4 5.5 1.5 6.4

SRENO 01545500 9.5 1.6 -3.5 2.6 -1.5 -1.2

SWILK 01536500 -0.2 1.1 0.6 11.6 4.0 2.3

SWILL 01551500 8.6 1.1 -1.4 -0.6 -1.4 -0.4

BUSHK 01439500 -5.9 -0.7 4.0 13.5 5.7 6.3

CLEAR 01541500 16.8 1.2 -3.6 4.8 -1.2 1.7

SDANV 01540500 -0.4 0.2 -1.2 8.1 4.3 3.9

SBOWE 01541000 11.4 1.0 1.4 6.4 -2.4 -3.2

JUNIA 01567000 0.0 -0.2 -3.7 7.5 0.8 -1.2

SHARR 01570500 2.1 0.5 0.2 5.0 2.1 1.5

RAYST 01562000 -2.7 -0.1 -1.2 0.7 0.1 0.7

PLUKE 01598500 — — — 19.6 0.6 -7.3

PPTRX 01638500 2.0 1.0 -1.1 3.9 -0.3 -1.6

GOOSE 01644000 58.7 8.8 5.8 -8.0 0.5 5.9

RAPPA 01668000 -5.7 -1.0 1.3 -12.6 -1.1 -3.5
16 Spatial and Temporal Trends in Runoff at Long-Term Streamgages within and near the Chesapeake Bay Watershed

Table 5. Results of annual and seasonal trend slopes for 1930–1969 and 1970–2010.—Continued

[ID, identification number; trend slope units in percent change per decade; —, insufficient data]

Abbreviated name of 

streamgage

Streamgage

ID

1930-1969 1970-2010

7-day minimum Mean 1-day maximum 7-day minimum Mean 1-day maximum

JCART 02035000 -2.2 -0.4 2.0 -4.8 -3.8 -7.2

JBUCH 02019500 -2.6 0.2 3.9 8.3 -2.7 -7.5

ROANO 02055000 -3.9 -0.9 0.3 -4.1 -4.4 -6.4

NEWRI 03171000 — — — -4.4 -4.2 -7.1

REEDC 03167000 3.3 4.3 4.3 -1.8 -4.7 -7.0

HOLST 03488000 -1.4 0.5 7.8 0.2 -3.7 -6.4

BANIS 02077000 15.7 -0.9 -8.0 -12.2 -3.3 1.2

Fall

BLACK 04252500 24.6 7.8 4.6 -3.4 9.7 11.9

CHENA 01512500 -3.2 -3.5 -4.5 11.8 18.4 18.5

SCONK 01503000 -7.1 -5.2 -5.0 17.6 15.4 8.4

CHEMU 01531000 2.4 1.0 2.5 17.8 10.6 15.6

STOWA 01531500 -5.0 -3.7 -3.2 15.3 14.7 13.1

TOWAN 01532000 -2.6 -2.0 -2.9 14.5 15.5 12.6

TUNKH 01534000 -1.6 -4.4 -5.5 17.2 23.3 16.6

LYCOM 01550000 0.7 4.6 5.5 5.6 2.8 -2.0

DRIFT 01543000 1.1 1.3 1.2 8.2 8.7 18.8

SRENO 01545500 9.1 5.5 7.7 4.0 2.9 7.5

SWILK 01536500 -1.4 -1.3 -1.1 14.2 16.4 15.7

SWILL 01551500 7.7 5.3 8.6 1.9 2.5 4.7

BUSHK 01439500 -5.9 -1.8 -3.1 18.5 28.4 21.0

CLEAR 01541500 15.3 4.5 -0.2 4.8 0.4 9.3

SDANV 01540500 -1.5 -1.7 -2.4 8.7 18.1 17.8

SBOWE 01541000 10.0 2.4 -0.9 4.9 1.9 8.0

JUNIA 01567000 -1.0 -0.9 -0.1 10.1 7.8 11.6

SHARR 01570500 1.3 -0.1 0.8 8.4 10.8 8.5

RAYST 01562000 -2.9 -0.6 0.0 0.8 2.7 7.9

PLUKE 01598500 — — — 14.5 5.6 -5.4

PPTRX 01638500 1.8 0.4 -1.2 5.6 4.0 -2.4

GOOSE 01644000 51.6 26.8 28.4 -0.4 5.4 8.9

RAPPA 01668000 -6.1 -0.9 -1.0 -6.6 2.3 7.8

JCART 02035000 -2.3 0.7 -1.2 -2.3 2.1 11.4

JBUCH 02019500 -2.4 0.6 -0.7 7.5 5.4 8.6

ROANO 02055000 -4.9 0.0 -0.1 -2.7 -0.3 6.7

NEWRI 03171000 — — — -2.5 -2.1 5.8

REEDC 03167000 0.9 -1.3 -2.7 -1.3 0.5 0.7

HOLST 03488000 -1.9 -0.2 0.5 0.6 -0.8 -4.2

BANIS 02077000 13.7 4.4 3.6 -5.9 3.0 26.2

Winter

BLACK 04252500 4.7 1.6 2.2 2.6 11.1 17.9

CHENA 01512500 3.0 3.3 2.7 12.3 8.9 7.4

SCONK 01503000 1.6 3.8 5.5 13.3 6.9 8.8

CHEMU 01531000 9.8 7.0 6.7 18.2 11.4 10.5

STOWA 01531500 5.3 5.3 7.2 14.4 8.2 9.7

TOWAN 01532000 5.3 4.8 7.8 14.1 10.6 10.9
Temporal Trends In Runoff 17

Table 5. Results of annual and seasonal trend slopes for 1930–1969 and 1970–2010.—Continued

[ID, identification number; trend slope units in percent change per decade; —, insufficient data]

Abbreviated name of 

streamgage

Streamgage

ID

1930-1969 1970-2010

7-day minimum Mean 1-day maximum 7-day minimum Mean 1-day maximum

TUNKH 01534000 6.3 4.0 7.8 20.6 13.9 8.2

LYCOM 01550000 5.1 7.2 13.3 17.3 9.4 11.6

DRIFT 01543000 3.8 0.5 3.8 8.9 8.8 17.5

SRENO 01545500 8.7 3.2 1.5 9.2 5.2 9.3

SWILK 01536500 6.4 5.9 8.0 16.2 9.8 10.1

SWILL 01551500 9.2 3.8 3.3 8.7 5.7 11.8

BUSHK 01439500 3.2 1.3 7.2 12.8 12.2 11.8

CLEAR 01541500 11.5 1.5 1.5 12.0 4.2 4.3

SDANV 01540500 7.1 4.6 4.8 14.5 8.3 10.3

SBOWE 01541000 9.8 0.6 2.0 11.3 2.4 5.1

JUNIA 01567000 4.2 1.7 0.5 11.3 4.7 1.2

SHARR 01570500 6.2 4.0 5.1 14.3 8.2 7.4

RAYST 01562000 2.7 0.7 1.3 5.1 2.1 -3.4

PLUKE 01598500 — — — 5.0 -0.9 -9.2

PPTRX 01638500 4.6 1.6 0.7 1.2 -0.2 -5.1

GOOSE 01644000 30.3 20.1 12.9 3.9 -3.1 -3.7

RAPPA 01668000 1.8 1.9 8.8 -1.4 -3.8 -6.9

JCART 02035000 1.1 0.4 3.9 -2.1 -5.1 -6.7

JBUCH 02019500 0.7 0.7 3.5 1.1 -6.3 -11.1

ROANO 02055000 1.0 0.5 2.9 1.9 -7.3 -12.2

NEWRI 03171000 — — — -4.7 -4.7 -6.3

REEDC 03167000 5.0 10.4 18.4 -2.5 -7.7 -13.4

HOLST 03488000 0.4 1.6 4.4 -2.4 -6.9 -9.5

BANIS 02077000 6.9 7.0 8.7 -1.2 -3.1 -0.3

Spring

BLACK 04252500 5.4 0.2 2.9 2.9 0.4 0.4

CHENA 01512500 -0.1 -1.5 -4.1 1.2 -2.1 0.8

SCONK 01503000 0.3 -0.6 -1.6 1.7 -2.1 2.6

CHEMU 01531000 2.2 -0.9 -1.6 3.4 -3.1 -1.1

STOWA 01531500 0.7 0.3 0.6 2.8 -2.5 -0.9

TOWAN 01532000 0.4 -0.1 0.0 4.7 -5.7 -5.7

TUNKH 01534000 3.9 0.5 5.2 1.3 -2.7 -1.4

LYCOM 01550000 -2.7 0.6 3.2 10.6 -6.5 -6.0

DRIFT 01543000 -0.3 -1.5 -2.7 1.2 -3.8 1.1

SRENO 01545500 0.3 0.6 -3.4 1.8 -5.5 -3.8

SWILK 01536500 1.5 0.5 1.1 1.5 -3.0 -1.8

SWILL 01551500 -0.1 -0.5 -2.0 1.5 -5.9 -4.0

BUSHK 01439500 -1.8 0.1 4.0 1.3 -3.3 -1.0

CLEAR 01541500 4.9 1.7 -3.3 1.8 -4.9 -6.6

SDANV 01540500 1.3 -0.5 -0.7 6.5 0.6 0.8

SBOWE 01541000 6.0 1.8 0.3 1.2 -5.8 -8.0

JUNIA 01567000 -0.3 -0.7 -3.4 0.8 -1.9 -0.4

SHARR 01570500 -0.6 -0.4 -0.7 3.8 -3.3 -1.8

RAYST 01562000 1.8 0.3 -1.2 0.5 -0.2 3.5

PLUKE 01598500 — — — 5.3 -1.0 -3.9
18 Spatial and Temporal Trends in Runoff at Long-Term Streamgages within and near the Chesapeake Bay Watershed

Table 5. Results of annual and seasonal trend slopes for 1930–1969 and 1970–2010.—Continued

[ID, identification number; trend slope units in percent change per decade; —, insufficient data]

Abbreviated name of 

streamgage

Streamgage

ID

1930-1969 1970-2010

7-day minimum Mean 1-day maximum 7-day minimum Mean 1-day maximum

PPTRX 01638500 2.2 1.8 -0.7 -0.4 -0.7 4.3

GOOSE 01644000 9.9 4.4 -1.6 -3.6 1.5 8.5

RAPPA 01668000 0.0 -0.1 1.0 -4.6 -0.2 7.4

JCART 02035000 0.0 1.4 4.1 -6.0 -5.2 -8.8

JBUCH 02019500 0.2 2.8 8.0 -1.9 -4.1 -7.9

ROANO 02055000 0.9 3.6 14.7 -4.7 -7.1 -9.4

NEWRI 03171000 — — — -3.9 -6.0 -6.3

REEDC 03167000 8.6 8.8 16.0 -5.4 -6.6 -4.8

HOLST 03488000 0.6 4.4 16.2 -2.7 -5.5 -5.6

BANIS 02077000 2.5 -0.1 -7.1 -4.5 -4.3 -0.8

Summer

BLACK 04252500 21.5 9.0 6.6 4.2 9.6 17.6

CHENA 01512500 -2.0 -3.2 -6.7 11.8 16.7 23.7

SCONK 01503000 -5.8 -4.5 -6.6 19.1 17.4 24.8

CHEMU 01531000 1.4 -0.5 -0.3 12.7 8.8 6.4

STOWA 01531500 -3.8 -3.1 -3.8 13.4 13.6 15.1

TOWAN 01532000 -2.2 -2.5 -5.9 3.9 -0.2 1.6

TUNKH 01534000 -1.4 -2.0 -1.9 13.9 13.7 21.8

LYCOM 01550000 -2.2 0.9 -1.9 2.2 -2.7 -4.1

DRIFT 01543000 1.7 -0.9 -4.7 4.4 1.3 -5.1

SRENO 01545500 8.9 2.8 -0.8 1.0 -4.3 -8.3

SWILK 01536500 -1.0 -1.1 -2.4 8.3 10.8 9.9

SWILL 01551500 6.9 2.5 -2.9 -2.4 -5.3 -8.6

BUSHK 01439500 -5.8 -4.9 -5.9 5.8 8.6 10.0

CLEAR 01541500 10.5 1.6 -3.1 2.6 -1.8 -3.6

SDANV 01540500 -1.6 -1.6 -2.6 7.5 9.7 8.0

SBOWE 01541000 12.0 1.6 -3.9 4.3 -3.5 -8.6

JUNIA 01567000 -0.7 -1.0 -3.9 4.5 -1.0 2.6

SHARR 01570500 0.3 -0.8 -2.6 2.3 2.1 -0.6

RAYST 01562000 -2.3 -1.6 -4.3 -1.3 -2.4 -1.3

PLUKE 01598500 — — — 22.9 11.0 9.5

PPTRX 01638500 0.5 -0.4 1.1 -0.7 -2.1 -5.8

GOOSE 01644000 75.9 26.4 26.8 -9.2 -3.1 -4.0

RAPPA 01668000 -6.0 -4.8 -0.3 -12.6 -4.8 -4.2

JCART 02035000 -3.7 -3.7 -1.7 -4.1 -6.1 -11.5

JBUCH 02019500 -2.6 -3.2 -3.4 9.3 1.6 -7.8

ROANO 02055000 -5.7 -6.2 -10.4 -1.8 0.1 1.2

NEWRI 03171000 — — — -3.5 -3.9 -0.1

REEDC 03167000 2.2 0.5 -2.6 -1.3 -0.8 2.2

HOLST 03488000 -2.3 -3.7 -4.1 1.0 3.6 0.4

BANIS 02077000 5.5 -4.2 -6.3 -11.2 -9.5 -9.1
Temporal Trends In Runoff 19

Table 6. Summary of results of annual and seasonal trends in data for 1930–1969 and 1970–2010 north and south of 40.25 degrees 

north latitude.

[n, number of streamgages; >, greater than; <, less than; trend slope units in percent change per decade; °, degrees]

Flow 

statistic

1930-1969 1970-2010

n, positive 

slope (> 1)

n, near-zero

slope (-1 to 1)

n, negative 

slope (< -1)

Average 

slope

n, positive 

slope (> 1)

n, near-zero

slope (-1 to 1)

n, negative 

slope (< -1)

Average 

slope

North of 40.25° north latitude, 18 streamgages

Annual

7-day minimum 7 5 6 3.1 17 1 0 8.3

Mean 7 9 2 0.5 12 2 4 2.2

1-day maximum 5 5 8 -0.5 12 3 3 2.2

Fall

7-day minimum 8 1 9 2.4 17 0 1 10.0

Mean 4 2 8 0.4 17 1 0 11.6

1-day maximum 6 4 8 0.1 17 0 1 12.1

Winter

7-day minimum 18 0 0 6.2 18 0 0 12.9

Mean 16 2 0 3.6 18 0 0 8.3

1-day maximum 17 1 0 5.1 18 0 0 9.7

Spring

7-day minimum 7 9 2 1.2 17 1 0 2.8

Mean 2 14 2 0.0 0 2 16 -3.4

1-day maximum 5 5 8 -0.3 2 5 11 -2.0

Summer

7-day minimum 7 2 9 2.0 17 0 1 6.6

Mean 5 4 9 -0.4 11 1 6 5.2

1-day maximum 1 2 15 -3.0 11 1 6 5.7

South of 40.25° north latitude, 10 streamgages

Annual

7-day minimum 4 0 6 6.1 3 2 7 -1.3

Mean 3 6 1 1.1 0 4 8 -2.2

1-day maximum 6 1 3 1.5 2 1 9 -3.9

Fall

7-day minimum 3 6 2 4.8 3 3 6 0.6

Mean 2 7 1 3.0 8 3 1 2.3

1-day maximum 2 4 4 2.6 8 1 3 6.0

Winter

7-day minimum 8 2 0 5.5 6 0 6 0.3

Mean 6 4 0 4.5 1 2 9 -3.9

1-day maximum 9 1 0 6.5 0 1 11 -7.3

Spring

7-day minimum 5 5 0 2.7 1 2 9 -2.7

Mean 7 3 0 2.7 1 3 8 -3.3

1-day maximum 6 1 3 4.9 4 1 7 -2.0

Summer

7-day minimum 3 1 6 6.2 3 1 8 -1.0

Mean 1 2 7 -0.1 3 2 7 -1.4

1-day maximum 2 1 7 -0.5 3 2 7 -2.5
20 Spatial and Temporal Trends in Runoff at Long-Term Streamgages within and near the Chesapeake Bay Watershed

was confirmed for discharge in the New England States by 

Collins (2009). Comparison of the results of statistics for the 

two subperiods is shown in table 5, and a summary of the 

statistics north and south of latitude 40.25° north is shown in 

table 6.

The data in tables 5 and 6 suggest a discontinuity 

between the runoff values for 1930 through 1969 compared 

to those for 1970 through 2010. Because a large number 

of streamgages in the north are located on tributaries to the 

Susquehanna River, the sites were thinned to decrease spatial 

correlation and avoid extensive double counting of flows as 

these records were aggregated. As a result of the thinning, sites 

SRNEO, SWILK, and SDANV in the north and site JBUCH 

in the south were excluded from the analysis. To compare the 

data from the two subperiods, the mean of the runoff data for 

each site in the north (15 sites) for each year and the mean for 

each site in the south (11 sites) for each year were calculated. 

The mean of the data for all sites for each year was plotted for 

each of the six statistics of interest: the 7-day minimum runoff 

in the north and south (fig. 18); the mean runoff in the north 

and south (fig. 19); and the 1-day maximum runoff in the north 

and south (fig. 20).

Multiple regression models were developed and tested to 

define the nature of the change between the two subperiods. 

The general form of the multiple regression model is:

Q T = + β β • + β β • + D D• •T + ε 0 1 2 3 , (5)

where:

Q is the mean runoff for the region;

T is time defined as water year minus 1970, so 

that the T variable ranges from 40 to +40;

D is a dummy variable, defined as 0 for the 

years 1930 through 1969, and 1 for 1970 

through 2010;

 is the random error; and

 0

,  1 , 2, and  3 are regression coefficients.

Using analysis of covariance (ANCOVA; Helsel and Hirsch, 

2002), models that are subsets of these explanatory variables 

were compared, and the regression coefficients were tested for 

statistical significance.

The six time series (figs. 18–20) were tested for differences in runoff for 1930 through 1969 and 1970 through 2010. 

Five regression models were considered as a description of 

each of the time series.

Model 0: Q = + β ε 0 . Model 0 is a stationary random process 

with no linear or step trend and is considered the null 

hypothesis.

Model 1: Q T = + β β • + ε 0 1 . Model 1 is a stationary random 

process with a single linear trend.

Model 2: Q D = + β β • + ε 0 2 . Model 2 is a stationary random 

process with a step trend after 1969.

Model 3: Q T = + β β 0 1 • + β ε 2 • + D . Model 3 is a stationary 

random process with a single linear trend with a step 

trend added to it after 1969.

Model 4: Q T = + β β • + β β • + D D• •T + ε 0 1 2 3 .

Model 4 is a stationary random process with two separate 

linear trends, one for 1930 through 1969 and one for 1970 

through 2010.

The first step in selecting the optimal model for the time 

series was to fit all five of the models to each of the six time 

series. Model 1 and model 2, the two models with an identical 

number of coefficients, were compared; the model with the 

lowest sum of squared errors (SSE) was retained for further 

testing. The remaining models, model 0, model 3, and model 4, 

South of 40.25 degrees north latitude

North of 40.25 degrees north latitude

Annual 7-day minimum runoff, in millimeters per day (mm/day)

1930 1950 1970 1990 2010

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4

0.45

0.5

Annual 7-day minimum runoff, in millimeters per day (mm/day)

1930 1950 1970 1990 2010

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4

0.45

0.5

EXPLANATION

Model results

95 percent confidence interval for the mean

Figure 18. Selected regression model for means of the 7-day 

minimum runoff for sites north of 40.25 degrees north latitude and 

south of 40.25 degrees north latitude.
Temporal Trends In Runoff 21

were compared to the retained model in a pairwise fashion 

from least complex (model 0) to most complex (model 4). 

For each comparison, an F test was performed to determine if 

the decrease in the SSE was sufficiently large to merit retaining the model. The choice of models was determined by the 

p-value (the attained significance level), that is, the probability 

that the decrease in SSE of this size or greater can be expected 

by chance alone. If the p-value was less than or equal to 0.05, 

the more complex model was accepted. If the p-value was 

greater than 0.05, the simpler model was then compared to the 

next model. The decision to retain the next model was made 

on the basis of the p-value from the comparison with the next 

model. This procedure was repeated until all models had been 

tested.

The results of the model testing and model selection 

process for the six time series follow. RSSi is the residual sum 

of squares for model i; F is the test statistic; DF is the number 

of degrees of freedom; = is equal to; and < is less than.

1930 1950 1970 1990 2010

1930 1950 1970 1990 2010

Annual mean runoff, in millimeters per day (mm/day)

0

0.5

1

1.5

2

2.5

Annual mean runoff, in millimeters per day (mm/day)

0

0.5

1

1.5

2

2.5

South of 40.25 degrees north latitude

North of 40.25 degrees north latitude

EXPLANATION

Model results

95 percent confidence interval for the mean

Annual 1-day maximum runoff, in millimeters per day (mm/day)

1930 1950 1970 1990 2010

0

5

10

15

20

25

30

35

40

45

50

Annual 1-day maximum runoff, in millimeters per day (mm/day)

1930 1950 1970 1990 2010

0

5

10

15

20

25

30

35

40

45

50

South of 40.25 degrees north latitude

North of 40.25 degrees north latitude

EXPLANATION

Model results

95 percent confidence interval for the mean

Figure 19. Selected regression model for means of the mean 

runoff for sites north of 40.25 degrees north latitude and south of 

40.25 degrees north latitude.

Figure 20. Selected regression model for means of the 1-day 

maximum runoff for sites north of 40.25 degrees north latitude and 

south of 40.25 degrees north latitude.
22 Spatial and Temporal Trends in Runoff at Long-Term Streamgages within and near the Chesapeake Bay Watershed

Model selection for the 7-day minimum runoff in the north 

(fig. 18):

• Compare models 1 and 2, RSS1 = 0.309, 

RSS2 = 0.305, model 2 RSS is lower, therefore, 

proceed with model 2.

• Compare models 2 and 0, F = 16.3 on 1 and 79 DF, 

p = 0.0001, therefore, reject model 0 and proceed 

with model 2.

• Compare models 2 and 3, F = 0.717 on 1 and 78 DF, 

p = 0.40, do not reject model 2.

• Compare models 2 and 4, F = 0.356 on 2 and 77 DF, 

p = 0.70, do not reject model 2.

• Therefore, select model 2.

Model selection for the 7-day minimum runoff in the south 

(fig. 18):

• Compare models 1 and 2, RSS1 = 0.349, 

RSS2 = 0.339, model 2 RSS is lower, therefore, 

proceed with model 2.

• Compare models 2 and 0, F = 9.2 on 1 and 79 DF, 

p = 0.003, therefore, reject model 0 and proceed with 

model 2.

• Compare models 2 and 3, F = 0.0024 on 1 and 

78 DF, p = 0.96, do not reject model 2.

• Compare models 2 and 4, F = 0.042 on 2 and 77 DF, 

p = 0.964, do not reject model 2.

• Therefore, select model 2.

Model selection for the mean runoff in the north (fig. 19):

• Compare models 1 and 2, RSS1 = 8.17, RSS2 = 7.74, 

model 2 RSS is lower, therefore, proceed with 

model 2.

• Compare models 2 and 0, F = 9.28 on 1 and 79 DF, 

p = 0.003, therefore, reject model 0 and proceed with 

model 2.

• Compare models 2 and 3, F = 0.711 on 1 and 78 DF, 

p = 0.40, do not reject model 2.

• Compare models 2 and 4, F = 0.369 on 2 and 77 DF, 

p = 0.69, do not reject model 2.

• Therefore, select model 2.

Model selection for the mean runoff in the south (fig. 19):

• Compare models 1 and 2, RSS1 = 7.58, RSS2 = 7.22, 

model 2 RSS is lower, therefore, proceed with 

model 2.

• Compare models 2 and 0, F = 7.01 on 1 and 79 DF, 

p = 0.0097, therefore, reject model 0 and proceed 

with model 2.

• Compare models 2 and 3, F = 1.28 on 1 and 78 DF, 

p = 0.26, do not reject model 2.

• Compare models 2 and 4, F = 1.25 on 2 and 77 DF, 

p = 0.29, do not reject model 2.

• Therefore, select model 2.

Model selection for the 1-day maximum runoff in the north 

(fig. 20):

• Compare models 1 and 2, RSS1 = 3877, 

RSS2 = 3864, model 2 RSS is lower, therefore, proceed with model 2.

• Compare models 2 and 0, F = 0.26 on 1 and 79 DF, 

p = 0.61, therefore, accept model 0 and reject 

model 2.

• Compare models 0 and 3, F = 0.39 on 2 and 78 DF, 

p = 0.68, do not reject model 0.

• Compare models 0 and 4, F = 0.26 on 3 and 77 DF, 

p = 0.854, do not reject model 0.

• Therefore, select model 0.

Model selection for the 1-day maximum runoff in the south 

(fig. 20):

• Compare models 1 and 2, RSS1 = 2814, RSS2 = 2778, 

model 2 RSS is lower, therefore, proceed with 

model 2.

• Compare models 2 and 0, F = 1.42 on 1 and 79 DF, 

p = 0.29, therefore, reject model 2 and proceed with 

model 0.

• Compare models 0 and 3, F = 3.91 on 2 and 78 DF, 

p = 0.024, therefore, reject model 0 and proceed with 

model 3.

• Compare models 3 and 4, F = 0.17 on 1 and 77 DF, 

p = 0.68, therefore, reject model 4.

• Therefore, select model 3.

A summary of the selected model for each of the time 

series is shown in table 7.

For the 7-day minimum runoff and the mean runoff in 

both the north and south, a clear distinction was noted, with 

the 1970 through 2010 subperiod having higher runoff values 

than the 1930 through 1969 subperiod. These differences 

range from as small as a 15-percent increase in the case of the 

mean runoff in the north, to as large as a 41-percent increase 

in the case of the 7-day minimum runoff in the north. For the 

1-day maximum runoff in the north, there was no significant 

difference between the two subperiods. The situation for the 

1-day maximum runoff in the south is more complicated. 

There was an upward step change between the two subperiods, 

but within each subperiod there was a decreasing trend with 

slopes that were not statistically significantly different from 

each other. The size of the upward step change was somewhat 
Summary 23

larger than the amount of decrease over each of the subperiods. If no linear trends were considered as possibilities, then 

a step trend characterization of these data would be that of a 

statistically insignificant slight increase over time.

The general conclusion that can be drawn from the 

analysis of the six time series is that the period from 1930 

through 1969 was statistically significantly different from 

the period 1970 through 2010. Overall, the pattern is one of 

increasing runoff over time. No general pattern of hydrologic 

conditions becoming “more extreme” over time was identified, 

which would have been indicated by decreases in minimum 

flows and increases in maximum flows. The pattern of change 

in maximum discharge, however, is uncertain.

Summary

U.S. Geological Survey streamgages provide valuable 

information about streamflow for a variety of users and uses. 

In this report, long-term streamflow data were analyzed in 

an attempt to identify trends in streamflow within the Chesapeake Bay watershed and surrounding area. Data from 30 

streamgages near and within the Chesapeake Bay watershed 

were selected for analysis because they have the longest period 

of record in common, 1930 through 2010. Stream discharge 

data from each streamgage were normalized by watershed area 

to obtain depth of runoff; annual runoff values were plotted as 

time series along with a lowess line that was determined by 

a robust smoothing process. The difference between the end 

points of the smoothed line was converted to percent change 

per decade for the period of interest, which was referred to 

as the trend slope. Trend slopes were categorized as positive, 

defined as a value greater than 1-percent increase per decade; 

Table 7. Model form, selected model and model coefficients, 

standard errors of the model coefficients, and R2 values for the 

six time series tested.

Model 

form

Selected 

model

Standard errors of 

model coefficients R2

North 7-day minimum runoff

Model 2 Q = 0.133 + 0.0557*D (0.0098) (0.014) 0.17

South 7-day minimum runoff

Model 2 Q= 0.169 + 0.0442*D (0.010) (0.015) 0.10

North mean runoff

Model 2 Q = 1.39 + 0.212*D (0.049) (0.070) 0.11

South mean runoff

Model 2 Q = 0.979 + 0.178*D (0.048) (0.067) 0.08

North 1-day maximum runoff

Model 0 Q = 17.75 (774) 0

South 1-day maximum runoff

Model 3 Q = 11.08 - 0.140*T + 

7.08*D

(1.44) (0.054) 

(2.5)

0.09

near-zero, defined as a value from –1- to 1-percent change per 

decade; or negative, defined as a value greater than 1-percent 

decrease per decade. Three runoff statistics were selected 

for analysis: the 7-day minimum; the mean; and the 1-day 

maximum.

Trend slopes in the runoff statistics were analyzed on 

an annual basis for the whole period of record as well as on a 

seasonal basis. The slopes also were analyzed both spatially 

and temporally. The overall pattern identified was one of 

increasing runoff through time, without becoming more variable. A distinct difference was observed in streamgages in the 

northern part of the watershed relative to those in the south. 

A latitude of 40.25 degrees north was identified as the line that 

generally separated the change of sign or magnitude of the 

trend slopes across the region.

The spatial results indicated that trend slopes in the north 

were generally greater than those in the south. In addition, 

runoff at streamgages in the north generally has become less 

variable over time than runoff in the south. This means that the 

low flows have increased so that they are closer to the mean 

flows and that the high flows have not increased as much as 

the low flows, remaining closer to the mean flows. In contrast, 

results in the south do not indicate a loss of variability as large 

as sites in the north. The seasonal statistics indicate that in the 

north, the 1-day maximum flows are higher in the winter than 

in the other seasons, whereas in the south, the 1-day maximum 

flows are higher in the fall than in the other seasons.

The temporal analysis was done by splitting the 80-year 

flow record into two subsets: 1930 through 1969 and 1970 

through 2010. The mean of the data for all sites for each year 

were plotted so that the following datasets were analyzed: 

the 7-day minimum runoff for the north and south; the mean 

runoff for the north and south; and the 1-day maximum runoff 

for the north and south. Results indicated that the period 1930 

through 1969 was statistically significantly different from the 

period 1970 through 2010. For the 7-day minimum runoff 

and the mean runoff, the latter period had significantly higher 

streamflow than did the earlier period, although within those 

two periods no significant linear trends were identified. For 

the 1-day maximum runoff, no step trend or linear trend could 

be shown to be statistically significant for the north, although 

the south showed a mixture of an upward step trend accompanied by linear downtrends within the periods. In no case was 

a change identified that indicated an increasing rate of change 

over time. No general pattern was identified of hydrologic 

conditions becoming “more extreme” over time, which would 

have been indicated by decreases in minimum flows and 

increases in maximum flows.

This analysis is the first to determine trends in runoff 

in the Chesapeake Bay watershed and surrounding area. The 

north-to-south extent of the study area spans two regions that 

generally are used for analysis of precipitation patterns, so previously published precipitation results and the runoff results 

presented here are not directly comparable. Nevertheless, the 

overall increase in runoff identified in this analysis generally 

is consistent with reported increases in precipitation in the 
24 Spatial and Temporal Trends in Runoff at Long-Term Streamgages within and near the Chesapeake Bay Watershed

region over similar time periods. This report does not address 

future changes to streamflow, but the results should serve as a 

baseline by which future changes can be compared.

Acknowledgments

The authors wish to acknowledge the colleague reviews 

of the report provided by Samuel H. Austin, Hydrologist, 

USGS, Richmond, Virginia, and Karen R. Ryberg, Statistician, 

USGS, Bismarck, North Dakota.

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Schwartz, M.D., Sheffield, Justin, Wood, Eric, Anderson, 

Bruce, Bradbury, James, DeGaetano, Art, Troy, T.J., and 

Wolfe, David, 2007, Past and future changes in climate 

and hydrological indicators in the US Northeast: Climate 

Dynamics, v. 28, p. 381–407.

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water resources: New York, Elsevier, 522 p.

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

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Investigations, book 4, chap. A3, 510 p.

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Appendix 25

Appendix
26 Spatial and Temporal Trends in Runoff at Long-Term Streamgages within and near the Chesapeake Bay Watershed

0.0

0.5

1.0

1.5

7−day minimum

Annual values,

in millimeters per day

0

1

2

3

4

5

6

annual mean

Black River near Boonville, N.Y.

0

10

20

30

40

50

1−day maximum

0.0

0.5

1.0

1.5

2.0

Fall season values,

in millimeters per day

0

1

2

3

4

5

6

7

0

5

10

15

20

25

30

35

0.0

0.5

1.0

1.5

2.0

2.5

Winter season values,

in millimeters per day

0

1

2

3

4

5

6

0

10

20

30

40

50

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

Spring season values,

in millimeters per day

0

2

4

6

8

10

0

10

20

30

40

50

1930 1950 1970 1990 2010

0.0

0.5

1.0

1.5

2.0

Summer season values,

in millimeters per day

1930 1950 1970 1990 2010

0

1

2

3

4

5

1930 1950 1970 1990 2010

0

10

20

30

40

50

Figure 1−1. Streamflow statistics (circles) in units of millimeters per day, annual values and seasonal values

Fall (Sept., Oct., and Nov.,), Winter (Dec., Jan., and Feb.), Spring (Mar., Apr., and May), and Summer (June, July, and Aug.)

and locally weighted scatterplot smooth (solid curve) for Black River near Boonville, N.Y., 1930−2010.

Figure 1−1. Streamflow statistics (circles) in units of millimeters per day, annual values and seasonal values; fall 

(September, October, and November), winter (December, January, and February), spring (March, April, and May), and 

summer (June, July, and August), and locally weighted scatterplot smooth (solid curve) for Black River near Boonville, N.Y., 

1930−2010.
Appendix 27

Figure 1−2. Streamflow statistics (circles) in units of millimeters per day, annual values and seasonal values; fall 

(September, October, and November), winter (December, January, and February), spring (March, April, and May), and 

summer (June, July, and August), and locally weighted scatterplot smooth (solid curve) for Chenango River near Chenango 

Forks, N.Y., 1930−2010.

0.0

0.1

0.2

0.3

0.4

0.5

0.6

7−day minimum

Annual values,

in millimeters per day

0.0

0.5

1.0

1.5

2.0

2.5

annual mean

Chenango River near Chenango Forks, N.Y.

0

10

20

30

40

1−day maximum

0.0

0.2

0.4

0.6

0.8

Fall season values,

in millimeters per day

0

1

2

3

4

0

5

10

15

0.0

0.2

0.4

0.6

0.8

1.0

1.2

Winter season values,

in millimeters per day

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

0

5

10

15

20

25

0.0

0.5

1.0

1.5

2.0

Spring season values,

in millimeters per day

0

1

2

3

4

5

0

5

10

15

20

25

30

35

1930 1950 1970 1990 2010

0.0

0.1

0.2

0.3

0.4

0.5

0.6

Summer season values,

in millimeters per day

1930 1950 1970 1990 2010

0.0

0.5

1.0

1.5

2.0

2.5

3.0

1930 1950 1970 1990 2010

0

10

20

30

40

Figure 1−2. Streamflow statistics (circles) in units of millimeters per day, annual values and seasonal values

Fall (Sept., Oct., and Nov.,), Winter (Dec., Jan., and Feb.), Spring (Mar., Apr., and May), and Summer (June, July, and Aug.)

and locally weighted scatterplot smooth (solid curve) for Chenango River near Chenango Forks, N.Y., 1930−2010.
28 Spatial and Temporal Trends in Runoff at Long-Term Streamgages within and near the Chesapeake Bay Watershed

0.0

0.1

0.2

0.3

0.4

0.5

7−day minimum

Annual values,

in millimeters per day

0.0

0.5

1.0

1.5

2.0

2.5

annual mean

Susquehanna River at Conklin, N.Y.

0

5

10

15

20

25

30

35

1−day maximum

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

Fall season values,

in millimeters per day

0

1

2

3

4

5

0

5

10

15

20

25

0.0

0.2

0.4

0.6

0.8

1.0

1.2

Winter season values,

in millimeters per day

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

0

5

10

15

20

25

0.0

0.5

1.0

1.5

2.0

Spring season values,

in millimeters per day

0

1

2

3

4

5

0

5

10

15

20

25

30

1930 1950 1970 1990 2010

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

Summer season values,

in millimeters per day

1930 1950 1970 1990 2010

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

1930 1950 1970 1990 2010

0

5

10

15

20

25

30

35

Figure 1−3. Streamflow statistics (circles) in units of millimeters per day, annual values and seasonal values

Fall (Sept., Oct., and Nov.,), Winter (Dec., Jan., and Feb.), Spring (Mar., Apr., and May), and Summer (June, July, and Aug.)

and locally weighted scatterplot smooth (solid curve) for Susquehanna River at Conklin, N.Y., 1930−2010.

Figure 1−3. Streamflow statistics (circles) in units of millimeters per day, annual values and seasonal values; fall 

(September, October, and November), winter (December, January, and February), spring (March, April, and May), and 

summer (June, July, and August), and locally weighted scatterplot smooth (solid curve) for Susquehanna River at Conklin, 

N.Y., 1930−2010.
Appendix 29

Figure 1−4. Streamflow statistics (circles) in units of millimeters per day, annual values and seasonal values; fall 

(September, October, and November), winter (December, January, and February), spring (March, April, and May), and 

summer (June, July, and August), and locally weighted scatterplot smooth (solid curve) for Chemung River at Chemung, N.Y., 

1930−2010.

0.00

0.05

0.10

0.15

0.20

0.25

0.30

7−day minimum

Annual values,

in millimeters per day

0.0

0.5

1.0

1.5

2.0

annual mean

Chemung River at Chemung, N.Y.

0

10

20

30

40

50

60

70

1−day maximum

0.0

0.1

0.2

0.3

0.4

0.5

Fall season values,

in millimeters per day

0.0

0.5

1.0

1.5

2.0

2.5

0

5

10

15

20

25

30

35

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

Winter season values,

in millimeters per day

0.0

0.5

1.0

1.5

2.0

2.5

0

5

10

15

20

25

30

0.0

0.2

0.4

0.6

0.8

1.0

1.2

Spring season values,

in millimeters per day

0

1

2

3

4

0

10

20

30

40

50

1930 1950 1970 1990 2010

0.00

0.05

0.10

0.15

0.20

0.25

0.30

Summer season values,

in millimeters per day

1930 1950 1970 1990 2010

0.0

0.5

1.0

1.5

2.0

2.5

3.0

1930 1950 1970 1990 2010

0

10

20

30

40

50

60

70

Figure 1−4. Streamflow statistics (circles) in units of millimeters per day, annual values and seasonal values

Fall (Sept., Oct., and Nov.,), Winter (Dec., Jan., and Feb.), Spring (Mar., Apr., and May), and Summer (June, July, and Aug.)

and locally weighted scatterplot smooth (solid curve) for Chemung River at Chemung, N.Y., 1930−2010.
30 Spatial and Temporal Trends in Runoff at Long-Term Streamgages within and near the Chesapeake Bay Watershed

Figure 1−5. Streamflow statistics (circles) in units of millimeters per day, annual values and seasonal values; fall 

(September, October, and November), winter (December, January, and February), spring (March, April, and May), and 

summer (June, July, and August), and locally weighted scatterplot smooth (solid curve) for Susquehanna River at Towanda, 

Pa., 1930−2010.

0.0

0.1

0.2

0.3

0.4

7−day minimum

Annual values,

in millimeters per day

0.0

0.5

1.0

1.5

2.0

2.5

annual mean

Susquehanna River at Towanda, Pa.

0

10

20

30

40

1−day maximum

0.0

0.1

0.2

0.3

0.4

0.5

0.6

Fall season values,

in millimeters per day

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

0

5

10

15

20

25

30

0.0

0.2

0.4

0.6

0.8

1.0

Winter season values,

in millimeters per day

0.0

0.5

1.0

1.5

2.0

2.5

3.0

0

5

10

15

20

25

0.0

0.5

1.0

1.5

Spring season values,

in millimeters per day

0

1

2

3

4

5

0

5

10

15

20

25

1930 1950 1970 1990 2010

0.0

0.1

0.2

0.3

0.4

0.5

0.6

Summer season values,

in millimeters per day

1930 1950 1970 1990 2010

0.0

0.5

1.0

1.5

2.0

2.5

1930 1950 1970 1990 2010

0

10

20

30

40

Figure 1−5. Streamflow statistics (circles) in units of millimeters per day, annual values and seasonal values

Fall (Sept., Oct., and Nov.,), Winter (Dec., Jan., and Feb.), Spring (Mar., Apr., and May), and Summer (June, July, and Aug.)

and locally weighted scatterplot smooth (solid curve) for Susquehanna River at Towanda, Pa., 1930−2010.
Appendix 31

Figure 1−6. Streamflow statistics (circles) in units of millimeters per day, annual values and seasonal values; fall 

(September, October, and November), winter (December, January, and February), spring (March, April, and May), and 

summer (June, July, and August), and locally weighted scatterplot smooth (solid curve) for Towanda Creek near Monroeton, 

Pa., 1930−2010.

0.00

0.05

0.10

0.15

0.20

7−day minimum

Annual values,

in millimeters per day

0.0

0.5

1.0

1.5

2.0

2.5

annual mean

Towanda Creek near Monroeton, Pa.

0

20

40

60

80

100

120

140

1−day maximum

0.0

0.1

0.2

0.3

0.4

0.5

Fall season values,

in millimeters per day

0.0

0.5

1.0

1.5

2.0

2.5

3.0

0

20

40

60

80

100

0.0

0.2

0.4

0.6

0.8

Winter season values,

in millimeters per day

0

1

2

3

4

0

20

40

60

80

100

120

140

0.0

0.2

0.4

0.6

0.8

1.0

1.2

Spring season values,

in millimeters per day

0

1

2

3

4

5

0

20

40

60

80

1930 1950 1970 1990 2010

0.00

0.05

0.10

0.15

0.20

0.25

0.30

0.35

Summer season values,

in millimeters per day

1930 1950 1970 1990 2010

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

1930 1950 1970 1990 2010

0

20

40

60

80

100

120

140

Figure 1−6. Streamflow statistics (circles) in units of millimeters per day, annual values and seasonal values

Fall (Sept., Oct., and Nov.,), Winter (Dec., Jan., and Feb.), Spring (Mar., Apr., and May), and Summer (June, July, and Aug.)

and locally weighted scatterplot smooth (solid curve) for Towanda Creek near Monroeton, Pa., 1930−2010.
32 Spatial and Temporal Trends in Runoff at Long-Term Streamgages within and near the Chesapeake Bay Watershed

Figure 1−7. Streamflow statistics (circles) in units of millimeters per day, annual values and seasonal values; fall 

(September, October, and November), winter (December, January, and February), spring (March, April, and May), and 

summer (June, July, and August), and locally weighted scatterplot smooth (solid curve) for Tunkhannock Creek near 

Tunkhannock, Pa., 1930−2010.

0.00

0.05

0.10

0.15

0.20

0.25

0.30

0.35

7−day minimum

Annual values,

in millimeters per day

0.0

0.5

1.0

1.5

2.0

2.5

annual mean

Tunkhannock Creek near Tunkhannock, Pa.

0

20

40

60

80

1−day maximum

0.0

0.2

0.4

0.6

0.8

Fall season values,

in millimeters per day

0.0

0.5

1.0

1.5

2.0

2.5

3.0

0

10

20

30

40

50

60

70

0.0

0.2

0.4

0.6

0.8

1.0

1.2

Winter season values,

in millimeters per day

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

0

10

20

30

40

0.0

0.2

0.4

0.6

0.8

1.0

1.2

Spring season values,

in millimeters per day

0

1

2

3

4

5

0

10

20

30

40

50

60

1930 1950 1970 1990 2010

0.0

0.1

0.2

0.3

0.4

Summer season values,

in millimeters per day

1930 1950 1970 1990 2010

0.0

0.5

1.0

1.5

2.0

2.5

1930 1950 1970 1990 2010

0

20

40

60

80

Figure 1−7. Streamflow statistics (circles) in units of millimeters per day, annual values and seasonal values

Fall (Sept., Oct., and Nov.,), Winter (Dec., Jan., and Feb.), Spring (Mar., Apr., and May), and Summer (June, July, and Aug.)

and locally weighted scatterplot smooth (solid curve) for Tunkhannock Creek near Tunkhannock, Pa., 1930−2010.
Appendix 33

Figure 1−8. Streamflow statistics (circles) in units of millimeters per day, annual values and seasonal values; fall 

(September, October, and November), winter (December, January, and February), spring (March, April, and May), and 

summer (June, July, and August), and locally weighted scatterplot smooth (solid curve) for Lycoming Creek near Trout Run, 

Pa., 1930−2010.

0.0

0.1

0.2

0.3

0.4

0.5

7−day minimum

Annual values,

in millimeters per day

0.0

0.5

1.0

1.5

2.0

2.5

3.0

annual mean

Lycoming Creek near Trout Run, Pa.

0

20

40

60

80

100

1−day maximum

0.0

0.2

0.4

0.6

0.8

1.0

1.2

Fall season values,

in millimeters per day

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

0

10

20

30

40

50

60

0.0

0.2

0.4

0.6

0.8

1.0

1.2

Winter season values,

in millimeters per day

0

1

2

3

4

0

20

40

60

80

100

0.0

0.5

1.0

1.5

Spring season values,

in millimeters per day

0

1

2

3

4

5

6

0

10

20

30

40

50

60

1930 1950 1970 1990 2010

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

Summer season values,

in millimeters per day

1930 1950 1970 1990 2010

0

1

2

3

4

1930 1950 1970 1990 2010

0

20

40

60

80

Figure 1−8. Streamflow statistics (circles) in units of millimeters per day, annual values and seasonal values

Fall (Sept., Oct., and Nov.,), Winter (Dec., Jan., and Feb.), Spring (Mar., Apr., and May), and Summer (June, July, and Aug.)

and locally weighted scatterplot smooth (solid curve) for Lycoming Creek near Trout Run, Pa., 1930−2010.
34 Spatial and Temporal Trends in Runoff at Long-Term Streamgages within and near the Chesapeake Bay Watershed

Figure 1−9. Streamflow statistics (circles) in units of millimeters per day, annual values and seasonal values; fall 

(September, October, and November), winter (December, January, and February), spring (March, April, and May), and 

summer (June, July, and August), and locally weighted scatterplot smooth (solid curve) for Driftwood Branch Sinnemahoning 

Creek at Sterling Run, Pa., 1930−2010.

0.00

0.05

0.10

0.15

0.20

0.25

0.30

0.35

7−day minimum

Annual values,

in millimeters per day

0.0

0.5

1.0

1.5

2.0

2.5

3.0

annual mean

Driftwood Branch Sinnemahoning Creek at Sterling Run, Pa.

0

10

20

30

40

50

60

70

1−day maximum

0.0

0.2

0.4

0.6

0.8

1.0

Fall season values,

in millimeters per day

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

0

10

20

30

40

50

0.0

0.2

0.4

0.6

0.8

1.0

Winter season values,

in millimeters per day

0

1

2

3

4

0

10

20

30

40

50

0.0

0.5

1.0

1.5

2.0

Spring season values,

in millimeters per day

0

1

2

3

4

5

6

0

10

20

30

40

50

60

70

1930 1950 1970 1990 2010

0.0

0.1

0.2

0.3

0.4

Summer season values,

in millimeters per day

1930 1950 1970 1990 2010

0.0

0.5

1.0

1.5

2.0

2.5

3.0

1930 1950 1970 1990 2010

0

10

20

30

40

50

60

70

Figure 1−9. Streamflow statistics (circles) in units of millimeters per day, annual values and seasonal values

Fall (Sept., Oct., and Nov.,), Winter (Dec., Jan., and Feb.), Spring (Mar., Apr., and May), and Summer (June, July, and Aug.)

and locally weighted scatterplot smooth (solid curve) for Driftwood Branch Sinnemahoning Creek at Sterling Run, Pa., 1930−2010.
Appendix 35

Figure 1−10. Streamflow statistics (circles) in units of millimeters per day, annual values and seasonal values; fall 

(September, October, and November), winter (December, January, and February), spring (March, April, and May), and 

summer (June, July, and August), and locally weighted scatterplot smooth (solid curve) for West Branch Susquehanna River 

at Renovo, Pa., 1930−2010.

0.0

0.1

0.2

0.3

0.4

0.5

0.6

7−day minimum

Annual values,

in millimeters per day

0.0

0.5

1.0

1.5

2.0

2.5

3.0

annual mean

West Branch Susquehanna River at Renovo, Pa.

0

10

20

30

40

50

60

70

1−day maximum

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

Fall season values,

in millimeters per day

0.0

0.5

1.0

1.5

2.0

2.5

3.0

0

5

10

15

20

25

30

35

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

Winter season values,

in millimeters per day

0

1

2

3

4

0

5

10

15

20

25

30

0.0

0.5

1.0

1.5

2.0

Spring season values,

in millimeters per day

0

1

2

3

4

5

6

0

10

20

30

40

50

60

70

1930 1950 1970 1990 2010

0.0

0.2

0.4

0.6

0.8

1.0

Summer season values,

in millimeters per day

1930 1950 1970 1990 2010

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

1930 1950 1970 1990 2010

0

10

20

30

40

50

60

Figure 1−10. Streamflow statistics (circles) in units of millimeters per day, annual values and seasonal values

Fall (Sept., Oct., and Nov.,), Winter (Dec., Jan., and Feb.), Spring (Mar., Apr., and May), and Summer (June, July, and Aug.)

and locally weighted scatterplot smooth (solid curve) for West Branch Susquehanna River at Renovo, Pa., 1930−2010.
36 Spatial and Temporal Trends in Runoff at Long-Term Streamgages within and near the Chesapeake Bay Watershed

Figure 1−11. Streamflow statistics (circles) in units of millimeters per day, annual values and seasonal values; fall 

(September, October, and November), winter (December, January, and February), spring (March, April, and May), and 

summer (June, July, and August), and locally weighted scatterplot smooth (solid curve) for Susquehanna River at Wilkes−

Barre, Pa., 1930−2010.

0.0

0.1

0.2

0.3

0.4

7−day minimum

Annual values,

in millimeters per day

0.0

0.5

1.0

1.5

2.0

2.5

annual mean

Susquehanna River at Wilkes−Barre, Pa.

0

5

10

15

20

25

30

35

1−day maximum

0.0

0.2

0.4

0.6

0.8

Fall season values,

in millimeters per day

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

0

5

10

15

20

25

0.0

0.2

0.4

0.6

0.8

1.0

Winter season values,

in millimeters per day

0.0

0.5

1.0

1.5

2.0

2.5

3.0

0

5

10

15

20

25

0.0

0.5

1.0

1.5

Spring season values,

in millimeters per day

0

1

2

3

4

5

0

5

10

15

20

25

1930 1950 1970 1990 2010

0.0

0.1

0.2

0.3

0.4

0.5

0.6

Summer season values,

in millimeters per day

1930 1950 1970 1990 2010

0.0

0.5

1.0

1.5

2.0

2.5

1930 1950 1970 1990 2010

0

5

10

15

20

25

30

35

Figure 1−11. Streamflow statistics (circles) in units of millimeters per day, annual values and seasonal values

Fall (Sept., Oct., and Nov.,), Winter (Dec., Jan., and Feb.), Spring (Mar., Apr., and May), and Summer (June, July, and Aug.)

and locally weighted scatterplot smooth (solid curve) for Susquehanna River at Wilkes−Barre, Pa., 1930−2010.
Appendix 37

Figure 1−12. Streamflow statistics (circles) in units of millimeters per day, annual values and seasonal values; fall 

(September, October, and November), winter (December, January, and February), spring (March, April, and May), and 

summer (June, July, and August), and locally weighted scatterplot smooth (solid curve) for West Branch Susquehanna River 

at Williamsport, Pa., 1930−2010.

0.0

0.1

0.2

0.3

0.4

0.5

0.6

7−day minimum

Annual values,

in millimeters per day

0.0

0.5

1.0

1.5

2.0

2.5

3.0

annual mean

West Branch Susquehanna River at Williamsport, Pa.

0

10

20

30

40

50

1−day maximum

0.0

0.2

0.4

0.6

0.8

1.0

1.2

Fall season values,

in millimeters per day

0.0

0.5

1.0

1.5

2.0

2.5

3.0

0

5

10

15

20

25

30

35

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

Winter season values,

in millimeters per day

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

0

5

10

15

20

25

30

35

0.0

0.5

1.0

1.5

2.0

Spring season values,

in millimeters per day

0

1

2

3

4

5

0

10

20

30

40

1930 1950 1970 1990 2010

0.0

0.2

0.4

0.6

0.8

Summer season values,

in millimeters per day

1930 1950 1970 1990 2010

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

1930 1950 1970 1990 2010

0

10

20

30

40

50

Figure 1−12. Streamflow statistics (circles) in units of millimeters per day, annual values and seasonal values

Fall (Sept., Oct., and Nov.,), Winter (Dec., Jan., and Feb.), Spring (Mar., Apr., and May), and Summer (June, July, and Aug.)

and locally weighted scatterplot smooth (solid curve) for West Branch Susquehanna River at Williamsport, Pa., 1930−2010.
38 Spatial and Temporal Trends in Runoff at Long-Term Streamgages within and near the Chesapeake Bay Watershed

Figure 1−13. Streamflow statistics (circles) in units of millimeters per day, annual values and seasonal values; fall 

(September, October, and November), winter (December, January, and February), spring (March, April, and May), and 

summer (June, July, and August), and locally weighted scatterplot smooth (solid curve) for Bush Kill at Shoemakers, Pa., 

1930−2010.

0.0

0.2

0.4

0.6

0.8

1.0

1.2

7−day minimum

Annual values,

in millimeters per day

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

annual mean

Bush Kill at Shoemakers, Pa.

0

20

40

60

80

100

120

1−day maximum

0.0

0.2

0.4

0.6

0.8

1.0

1.2

Fall season values,

in millimeters per day

0

1

2

3

4

5

0

5

10

15

20

25

30

35

0.0

0.5

1.0

1.5

2.0

Winter season values,

in millimeters per day

0

1

2

3

4

5

0

5

10

15

20

25

30

0.0

0.5

1.0

1.5

2.0

Spring season values,

in millimeters per day

0

1

2

3

4

5

6

0

10

20

30

40

50

1930 1950 1970 1990 2010

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

Summer season values,

in millimeters per day

1930 1950 1970 1990 2010

0

1

2

3

4

5

1930 1950 1970 1990 2010

0

20

40

60

80

100

120

Figure 1−13. Streamflow statistics (circles) in units of millimeters per day, annual values and seasonal values

Fall (Sept., Oct., and Nov.,), Winter (Dec., Jan., and Feb.), Spring (Mar., Apr., and May), and Summer (June, July, and Aug.)

and locally weighted scatterplot smooth (solid curve) for Bush Kill at Shoemakers, Pa., 1930−2010.
Appendix 39

Figure 1−14. Streamflow statistics (circles) in units of millimeters per day, annual values and seasonal values; fall 

(September, October, and November), winter (December, January, and February), spring (March, April, and May), and 

summer (June, July, and August), and locally weighted scatterplot smooth (solid curve) for Clearfield Creek at Dimeling, Pa., 

1930−2010.

0.0

0.1

0.2

0.3

0.4

0.5

0.6

7−day minimum

Annual values,

in millimeters per day

0.0

0.5

1.0

1.5

2.0

2.5

3.0

annual mean

Clearfield Creek at Dimeling, Pa.

0

20

40

60

80

1−day maximum

0.0

0.2

0.4

0.6

0.8

1.0

Fall season values,

in millimeters per day

0.0

0.5

1.0

1.5

2.0

2.5

3.0

0

5

10

15

20

25

30

35

0.0

0.5

1.0

1.5

Winter season values,

in millimeters per day

0

1

2

3

4

0

5

10

15

20

25

30

0.0

0.5

1.0

1.5

2.0

Spring season values,

in millimeters per day

0

1

2

3

4

5

0

20

40

60

80

1930 1950 1970 1990 2010

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

Summer season values,

in millimeters per day

1930 1950 1970 1990 2010

0.0

0.5

1.0

1.5

2.0

2.5

3.0

1930 1950 1970 1990 2010

0

10

20

30

40

50

60

Figure 1−14. Streamflow statistics (circles) in units of millimeters per day, annual values and seasonal values

Fall (Sept., Oct., and Nov.,), Winter (Dec., Jan., and Feb.), Spring (Mar., Apr., and May), and Summer (June, July, and Aug.)

and locally weighted scatterplot smooth (solid curve) for Clearfield Creek at Dimeling, Pa., 1930−2010.
40 Spatial and Temporal Trends in Runoff at Long-Term Streamgages within and near the Chesapeake Bay Watershed

Figure 1−15. Streamflow statistics (circles) in units of millimeters per day, annual values and seasonal values; fall 

(September, October, and November), winter (December, January, and February), spring (March, April, and May), and 

summer (June, July, and August), and locally weighted scatterplot smooth (solid curve) for Susquehanna River at Danville, 

Pa., 1930−2010.

0.0

0.1

0.2

0.3

0.4

0.5

7−day minimum

Annual values,

in millimeters per day

0.0

0.5

1.0

1.5

2.0

2.5

annual mean

Susquehanna River at Danville, Pa.

0

5

10

15

20

25

30

1−day maximum

0.0

0.2

0.4

0.6

0.8

Fall season values,

in millimeters per day

0.0

0.5

1.0

1.5

2.0

2.5

3.0

0

5

10

15

20

25

0.0

0.2

0.4

0.6

0.8

1.0

1.2

Winter season values,

in millimeters per day

0.0

0.5

1.0

1.5

2.0

2.5

3.0

0

5

10

15

20

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

Spring season values,

in millimeters per day

0

1

2

3

4

5

0

5

10

15

20

25

1930 1950 1970 1990 2010

0.0

0.1

0.2

0.3

0.4

0.5

0.6

Summer season values,

in millimeters per day

1930 1950 1970 1990 2010

0.0

0.5

1.0

1.5

2.0

2.5

1930 1950 1970 1990 2010

0

5

10

15

20

25

30

Figure 1−15. Streamflow statistics (circles) in units of millimeters per day, annual values and seasonal values

Fall (Sept., Oct., and Nov.,), Winter (Dec., Jan., and Feb.), Spring (Mar., Apr., and May), and Summer (June, July, and Aug.)

and locally weighted scatterplot smooth (solid curve) for Susquehanna River at Danville, Pa., 1930−2010.
Appendix 41

Figure 1−16. Streamflow statistics (circles) in units of millimeters per day, annual values and seasonal values; fall 

(September, October, and November), winter (December, January, and February), spring (March, April, and May), and 

summer (June, July, and August), and locally weighted scatterplot smooth (solid curve) for West Branch Susquehanna River 

at Bower, Pa., 1930−2010.

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

7−day minimum

Annual values,

in millimeters per day

0.0

0.5

1.0

1.5

2.0

2.5

3.0

annual mean

West Branch Susquehanna River at Bower, Pa.

0

20

40

60

80

1−day maximum

0.0

0.2

0.4

0.6

0.8

1.0

Fall season values,

in millimeters per day

0.0

0.5

1.0

1.5

2.0

2.5

3.0

0

10

20

30

40

50

0.0

0.5

1.0

1.5

Winter season values,

in millimeters per day

0

1

2

3

4

5

0

10

20

30

40

50

0.0

0.5

1.0

1.5

2.0

Spring season values,

in millimeters per day

0

1

2

3

4

5

0

10

20

30

40

50

60

70

1930 1950 1970 1990 2010

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

Summer season values,

in millimeters per day

1930 1950 1970 1990 2010

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

1930 1950 1970 1990 2010

0

20

40

60

80

Figure 1−16. Streamflow statistics (circles) in units of millimeters per day, annual values and seasonal values

Fall (Sept., Oct., and Nov.,), Winter (Dec., Jan., and Feb.), Spring (Mar., Apr., and May), and Summer (June, July, and Aug.)

and locally weighted scatterplot smooth (solid curve) for West Branch Susquehanna River at Bower, Pa., 1930−2010.
42 Spatial and Temporal Trends in Runoff at Long-Term Streamgages within and near the Chesapeake Bay Watershed

Figure 1−17. Streamflow statistics (circles) in units of millimeters per day, annual values and seasonal values; fall 

(September, October, and November), winter (December, January, and February), spring (March, April, and May), and 

summer (June, July, and August), and locally weighted scatterplot smooth (solid curve) for Juniata River at Newport, Pa., 

1930−2010.

0.0

0.1

0.2

0.3

0.4

0.5

7−day minimum

Annual values,

in millimeters per day

0.0

0.5

1.0

1.5

2.0

2.5

annual mean

Juniata River at Newport, Pa.

0

10

20

30

40

50

60

1−day maximum

0.0

0.2

0.4

0.6

0.8

1.0

Fall season values,

in millimeters per day

0.0

0.5

1.0

1.5

2.0

2.5

3.0

0

5

10

15

20

25

30

0.0

0.2

0.4

0.6

0.8

1.0

1.2

Winter season values,

in millimeters per day

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

0

5

10

15

20

25

30

0.0

0.5

1.0

1.5

Spring season values,

in millimeters per day

0

1

2

3

4

5

0

10

20

30

40

50

60

1930 1950 1970 1990 2010

0.0

0.1

0.2

0.3

0.4

0.5

0.6

Summer season values,

in millimeters per day

1930 1950 1970 1990 2010

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

1930 1950 1970 1990 2010

0

10

20

30

40

50

Figure 1−17. Streamflow statistics (circles) in units of millimeters per day, annual values and seasonal values

Fall (Sept., Oct., and Nov.,), Winter (Dec., Jan., and Feb.), Spring (Mar., Apr., and May), and Summer (June, July, and Aug.)

and locally weighted scatterplot smooth (solid curve) for Juniata River at Newport, Pa., 1930−2010.
Appendix 43

Figure 1−18. Streamflow statistics (circles) in units of millimeters per day, annual values and seasonal values; fall 

(September, October, and November), winter (December, January, and February), spring (March, April, and May), and 

summer (June, July, and August), and locally weighted scatterplot smooth (solid curve) for Susquehanna River at Harrisburg, 

Pa., 1930−2010.

0.0

0.1

0.2

0.3

0.4

0.5

7−day minimum

Annual values,

in millimeters per day

0.0

0.5

1.0

1.5

2.0

2.5

annual mean

Susquehanna River at Harrisburg, Pa.

0

10

20

30

40

1−day maximum

0.0

0.2

0.4

0.6

0.8

1.0

Fall season values,

in millimeters per day

0.0

0.5

1.0

1.5

2.0

2.5

0

5

10

15

20

25

0.0

0.2

0.4

0.6

0.8

1.0

1.2

Winter season values,

in millimeters per day

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

0

5

10

15

20

25

0.0

0.5

1.0

1.5

Spring season values,

in millimeters per day

0

1

2

3

4

5

0

5

10

15

20

25

30

1930 1950 1970 1990 2010

0.0

0.1

0.2

0.3

0.4

0.5

0.6

Summer season values,

in millimeters per day

1930 1950 1970 1990 2010

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

1930 1950 1970 1990 2010

0

10

20

30

40

Figure 1−18. Streamflow statistics (circles) in units of millimeters per day, annual values and seasonal values

Fall (Sept., Oct., and Nov.,), Winter (Dec., Jan., and Feb.), Spring (Mar., Apr., and May), and Summer (June, July, and Aug.)

and locally weighted scatterplot smooth (solid curve) for Susquehanna River at Harrisburg, Pa., 1930−2010.
44 Spatial and Temporal Trends in Runoff at Long-Term Streamgages within and near the Chesapeake Bay Watershed

Figure 1−19. Streamflow statistics (circles) in units of millimeters per day, annual values and seasonal values; fall 

(September, October, and November), winter (December, January, and February), spring (March, April, and May), and 

summer (June, July, and August), and locally weighted scatterplot smooth (solid curve) for Raystown Branch Juniata River at 

Saxton, Pa., 1930−2010.

0.00

0.05

0.10

0.15

0.20

0.25

0.30

7−day minimum

Annual values,

in millimeters per day

0.0

0.5

1.0

1.5

2.0

2.5

annual mean

Raystown Branch Juniata River at Saxton, Pa.

0

20

40

60

80

1−day maximum

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

Fall season values,

in millimeters per day

0.0

0.5

1.0

1.5

2.0

2.5

3.0

0

10

20

30

40

50

0.0

0.2

0.4

0.6

0.8

1.0

1.2

Winter season values,

in millimeters per day

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

0

10

20

30

40

50

60

0.0

0.2

0.4

0.6

0.8

1.0

1.2

Spring season values,

in millimeters per day

0

1

2

3

4

5

0

20

40

60

80

1930 1950 1970 1990 2010

0.0

0.1

0.2

0.3

0.4

Summer season values,

in millimeters per day

1930 1950 1970 1990 2010

0.0

0.5

1.0

1.5

2.0

2.5

1930 1950 1970 1990 2010

0

10

20

30

40

50

60

Figure 1−19. Streamflow statistics (circles) in units of millimeters per day, annual values and seasonal values

Fall (Sept., Oct., and Nov.,), Winter (Dec., Jan., and Feb.), Spring (Mar., Apr., and May), and Summer (June, July, and Aug.)

and locally weighted scatterplot smooth (solid curve) for Raystown Branch Juniata River at Saxton, Pa., 1930−2010.
Appendix 45

Figure 1−20. Streamflow statistics (circles) in units of millimeters per day, annual values and seasonal values; fall 

(September, October, and November), winter (December, January, and February), spring (March, April, and May), and 

summer (June, July, and August), and locally weighted scatterplot smooth (solid curve) for North Branch Potomac River at 

Luke, Md., 1930−2010.

0.0

0.2

0.4

0.6

0.8

1.0

7−day minimum

Annual values,

in millimeters per day

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

annual mean

North Branch Potomac River at Luke, Md.

0

10

20

30

40

50

1−day maximum

0.0

0.2

0.4

0.6

0.8

1.0

1.2

Fall season values,

in millimeters per day

0

1

2

3

4

0

5

10

15

20

25

30

35

0.0

0.5

1.0

1.5

2.0

Winter season values,

in millimeters per day

0

1

2

3

4

5

0

5

10

15

20

25

0.0

0.5

1.0

1.5

Spring season values,

in millimeters per day

0

1

2

3

4

5

6

0

5

10

15

20

25

30

1930 1950 1970 1990 2010

0.0

0.2

0.4

0.6

0.8

1.0

Summer season values,

in millimeters per day

1930 1950 1970 1990 2010

0.0

0.5

1.0

1.5

2.0

2.5

3.0

1930 1950 1970 1990 2010

0

10

20

30

40

50

Figure 1−20. Streamflow statistics (circles) in units of millimeters per day, annual values and seasonal values

Fall (Sept., Oct., and Nov.,), Winter (Dec., Jan., and Feb.), Spring (Mar., Apr., and May), and Summer (June, July, and Aug.)

and locally weighted scatterplot smooth (solid curve) for North Branch Potomac River at Luke, Md., 1930−2010.
46 Spatial and Temporal Trends in Runoff at Long-Term Streamgages within and near the Chesapeake Bay Watershed

Figure 1−21. Streamflow statistics (circles) in units of millimeters per day, annual values and seasonal values; fall 

(September, October, and November), winter (December, January, and February), spring (March, April, and May), and 

summer (June, July, and August), and locally weighted scatterplot smooth (solid curve) for Potomac River at Point of Rocks, 

Md., 1930−2010.

0.0

0.1

0.2

0.3

0.4

0.5

7−day minimum

Annual values,

in millimeters per day

0.0

0.5

1.0

1.5

2.0

annual mean

Potomac River at Point of Rocks, Md.

0

10

20

30

40

50

1−day maximum

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

Fall season values,

in millimeters per day

0.0

0.5

1.0

1.5

2.0

2.5

0

5

10

15

20

25

30

35

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

Winter season values,

in millimeters per day

0.0

0.5

1.0

1.5

2.0

2.5

3.0

0

5

10

15

20

25

30

0.0

0.2

0.4

0.6

0.8

1.0

1.2

Spring season values,

in millimeters per day

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

0

10

20

30

40

50

1930 1950 1970 1990 2010

0.0

0.1

0.2

0.3

0.4

0.5

Summer season values,

in millimeters per day

1930 1950 1970 1990 2010

0.0

0.5

1.0

1.5

2.0

2.5

1930 1950 1970 1990 2010

0

5

10

15

20

25

30

35

Figure 1−21. Streamflow statistics (circles) in units of millimeters per day, annual values and seasonal values

Fall (Sept., Oct., and Nov.,), Winter (Dec., Jan., and Feb.), Spring (Mar., Apr., and May), and Summer (June, July, and Aug.)

and locally weighted scatterplot smooth (solid curve) for Potomac River at Point of Rocks, Md., 1930−2010.
Appendix 47

Figure 1−22. Streamflow statistics (circles) in units of millimeters per day, annual values and seasonal values; fall 

(September, October, and November), winter (December, January, and February), spring (March, April, and May), and 

summer (June, July, and August), and locally weighted scatterplot smooth (solid curve) for Goose Creek near Leesburg, Va., 

1930−2010.

0.0

0.2

0.4

0.6

0.8

1.0

1.2

7−day minimum

Annual values,

in millimeters per day

0

1

2

3

4

5

6

7

annual mean

Goose Creek near Leesburg, Va.

0

100

200

300

400

500

1−day maximum

0.0

0.5

1.0

1.5

2.0

2.5

3.0

Fall season values,

in millimeters per day

0

2

4

6

8

0

50

100

150

200

250

0

1

2

3

4

Winter season values,

in millimeters per day

0

2

4

6

8

10

0

20

40

60

80

100

120

0.0

0.5

1.0

1.5

2.0

2.5

3.0

Spring season values,

in millimeters per day

0

2

4

6

8

10

0

50

100

150

200

1930 1950 1970 1990 2010

0.0

0.2

0.4

0.6

0.8

1.0

1.2

Summer season values,

in millimeters per day

1930 1950 1970 1990 2010

0

2

4

6

8

10

1930 1950 1970 1990 2010

0

100

200

300

400

500

Figure 1−22. Streamflow statistics (circles) in units of millimeters per day, annual values and seasonal values

Fall (Sept., Oct., and Nov.,), Winter (Dec., Jan., and Feb.), Spring (Mar., Apr., and May), and Summer (June, July, and Aug.)

and locally weighted scatterplot smooth (solid curve) for Goose Creek near Leesburg, Va., 1930−2010.
48 Spatial and Temporal Trends in Runoff at Long-Term Streamgages within and near the Chesapeake Bay Watershed

Figure 1−23. Streamflow statistics (circles) in units of millimeters per day, annual values and seasonal values; fall 

(September, October, and November), winter (December, January, and February), spring (March, April, and May), and 

summer (June, July, and August), and locally weighted scatterplot smooth (solid curve) for Rappahannock River near 

Fredericksburg, Va., 1930−2010.

0.0

0.1

0.2

0.3

0.4

0.5

0.6

7−day minimum

Annual values,

in millimeters per day

0.0

0.5

1.0

1.5

2.0

2.5

annual mean

Rappahannock River near Fredericksburg, Va.

0

20

40

60

80

1−day maximum

0.0

0.2

0.4

0.6

0.8

1.0

1.2

Fall season values,

in millimeters per day

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

0

20

40

60

80

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

Winter season values,

in millimeters per day

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

0

5

10

15

20

25

30

35

0.0

0.2

0.4

0.6

0.8

1.0

Spring season values,

in millimeters per day

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

0

10

20

30

40

50

60

1930 1950 1970 1990 2010

0.0

0.1

0.2

0.3

0.4

0.5

0.6

Summer season values,

in millimeters per day

1930 1950 1970 1990 2010

0.0

0.5

1.0

1.5

2.0

2.5

1930 1950 1970 1990 2010

0

10

20

30

40

50

60

Figure 1−23. Streamflow statistics (circles) in units of millimeters per day, annual values and seasonal values

Fall (Sept., Oct., and Nov.,), Winter (Dec., Jan., and Feb.), Spring (Mar., Apr., and May), and Summer (June, July, and Aug.)

and locally weighted scatterplot smooth (solid curve) for Rappahannock River near Fredericksburg, Va., 1930−2010.
Appendix 49

Figure 1−24. Streamflow statistics (circles) in units of millimeters per day, annual values and seasonal values; fall 

(September, October, and November), winter (December, January, and February), spring (March, April, and May), and 

summer (June, July, and August), and locally weighted scatterplot smooth (solid curve) for James River at Cartersville, Va., 

1930−2010.

0.0

0.1

0.2

0.3

0.4

0.5

0.6

7−day minimum

Annual values,

in millimeters per day

0.0

0.5

1.0

1.5

2.0

annual mean

James River at Cartersville, Va.

0

10

20

30

40

50

1−day maximum

0.0

0.2

0.4

0.6

0.8

Fall season values,

in millimeters per day

0.0

0.5

1.0

1.5

2.0

2.5

0

5

10

15

20

25

30

35

0.0

0.5

1.0

1.5

2.0

Winter season values,

in millimeters per day

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

0

5

10

15

20

0.0

0.2

0.4

0.6

0.8

1.0

1.2

Spring season values,

in millimeters per day

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

0

5

10

15

20

25

1930 1950 1970 1990 2010

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

Summer season values,

in millimeters per day

1930 1950 1970 1990 2010

0.0

0.5

1.0

1.5

2.0

2.5

3.0

1930 1950 1970 1990 2010

0

10

20

30

40

50

Figure 1−24. Streamflow statistics (circles) in units of millimeters per day, annual values and seasonal values

Fall (Sept., Oct., and Nov.,), Winter (Dec., Jan., and Feb.), Spring (Mar., Apr., and May), and Summer (June, July, and Aug.)

and locally weighted scatterplot smooth (solid curve) for James River at Cartersville, Va., 1930−2010.
50 Spatial and Temporal Trends in Runoff at Long-Term Streamgages within and near the Chesapeake Bay Watershed

Figure 1−25. Streamflow statistics (circles) in units of millimeters per day, annual values and seasonal values; fall 

(September, October, and November), winter (December, January, and February), spring (March, April, and May), and 

summer (June, July, and August), and locally weighted scatterplot smooth (solid curve) for James River at Buchanan, Va., 

1930−2010.

0.0

0.1

0.2

0.3

0.4

0.5

7−day minimum

Annual values,

in millimeters per day

0.0

0.5

1.0

1.5

2.0

2.5

annual mean

James River at Buchanan, Va.

0

10

20

30

40

50

1−day maximum

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

Fall season values,

in millimeters per day

0.0

0.5

1.0

1.5

2.0

2.5

0

10

20

30

40

50

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

Winter season values,

in millimeters per day

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

0

10

20

30

40

0.0

0.2

0.4

0.6

0.8

1.0

1.2

Spring season values,

in millimeters per day

0

1

2

3

4

5

0

5

10

15

20

25

30

35

1930 1950 1970 1990 2010

0.0

0.1

0.2

0.3

0.4

0.5

Summer season values,

in millimeters per day

1930 1950 1970 1990 2010

0.0

0.5

1.0

1.5

2.0

2.5

1930 1950 1970 1990 2010

0

10

20

30

40

50

Figure 1−25. Streamflow statistics (circles) in units of millimeters per day, annual values and seasonal values

Fall (Sept., Oct., and Nov.,), Winter (Dec., Jan., and Feb.), Spring (Mar., Apr., and May), and Summer (June, July, and Aug.)

and locally weighted scatterplot smooth (solid curve) for James River at Buchanan, Va., 1930−2010.
Appendix 51

Figure 1−26. Streamflow statistics (circles) in units of millimeters per day, annual values and seasonal values; fall 

(September, October, and November), winter (December, January, and February), spring (March, April, and May), and 

summer (June, July, and August), and locally weighted scatterplot smooth (solid curve) for Roanoke River at Roanoke, Va., 

1930−2010.

0.0

0.1

0.2

0.3

0.4

7−day minimum

Annual values,

in millimeters per day

0.0

0.5

1.0

1.5

2.0

annual mean

Roanoke River at Roanoke, Va.

0

10

20

30

40

50

1−day maximum

0.0

0.1

0.2

0.3

0.4

0.5

Fall season values,

in millimeters per day

0.0

0.5

1.0

1.5

2.0

0

10

20

30

40

0.0

0.2

0.4

0.6

0.8

1.0

1.2

Winter season values,

in millimeters per day

0.0

0.5

1.0

1.5

2.0

2.5

3.0

0

5

10

15

20

25

30

0.0

0.2

0.4

0.6

0.8

1.0

1.2

Spring season values,

in millimeters per day

0

1

2

3

4

0

10

20

30

40

1930 1950 1970 1990 2010

0.0

0.1

0.2

0.3

0.4

0.5

0.6

Summer season values,

in millimeters per day

1930 1950 1970 1990 2010

0.0

0.5

1.0

1.5

2.0

2.5

1930 1950 1970 1990 2010

0

10

20

30

40

50

Figure 1−26. Streamflow statistics (circles) in units of millimeters per day, annual values and seasonal values

Fall (Sept., Oct., and Nov.,), Winter (Dec., Jan., and Feb.), Spring (Mar., Apr., and May), and Summer (June, July, and Aug.)

and locally weighted scatterplot smooth (solid curve) for Roanoke River at Roanoke, Va., 1930−2010.
52 Spatial and Temporal Trends in Runoff at Long-Term Streamgages within and near the Chesapeake Bay Watershed

Figure 1−27. Streamflow statistics (circles) in units of millimeters per day, annual values and seasonal values; fall 

(September, October, and November), winter (December, January, and February), spring (March, April, and May), and 

summer (June, July, and August), and locally weighted scatterplot smooth (solid curve) for New River at Radford, Va., 

1930−2010.

0.0

0.2

0.4

0.6

0.8

1.0

7−day minimum

Annual values,

in millimeters per day

0.0

0.5

1.0

1.5

2.0

annual mean

New River at Radford, Va.

0

10

20

30

40

1−day maximum

0.0

0.2

0.4

0.6

0.8

1.0

1.2

Fall season values,

in millimeters per day

0.0

0.5

1.0

1.5

2.0

2.5

3.0

0

5

10

15

20

25

30

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

Winter season values,

in millimeters per day

0.0

0.5

1.0

1.5

2.0

2.5

3.0

0

5

10

15

20

25

30

0.0

0.5

1.0

1.5

2.0

Spring season values,

in millimeters per day

0

1

2

3

4

0

5

10

15

20

25

1930 1950 1970 1990 2010

0.0

0.2

0.4

0.6

0.8

1.0

1.2

Summer season values,

in millimeters per day

1930 1950 1970 1990 2010

0.0

0.5

1.0

1.5

2.0

2.5

3.0

1930 1950 1970 1990 2010

0

10

20

30

40

Figure 1−27. Streamflow statistics (circles) in units of millimeters per day, annual values and seasonal values

Fall (Sept., Oct., and Nov.,), Winter (Dec., Jan., and Feb.), Spring (Mar., Apr., and May), and Summer (June, July, and Aug.)

and locally weighted scatterplot smooth (solid curve) for New River at Radford, Va., 1930−2010.
Appendix 53

Figure 1−28. Streamflow statistics (circles) in units of millimeters per day, annual values and seasonal values; fall 

(September, October, and November), winter (December, January, and February), spring (March, April, and May), and 

summer (June, July, and August), and locally weighted scatterplot smooth (solid curve) for Reed Creek at Grahams Forge, 

Va., 1930−2010.

0.0

0.1

0.2

0.3

0.4

0.5

0.6

7−day minimum

Annual values,

in millimeters per day

0.0

0.5

1.0

1.5

2.0

annual mean

Reed Creek at Grahams Forge, Va.

0

10

20

30

40

50

1−day maximum

0.0

0.1

0.2

0.3

0.4

0.5

0.6

Fall season values,

in millimeters per day

0.0

0.5

1.0

1.5

2.0

0

5

10

15

20

0.0

0.2

0.4

0.6

0.8

1.0

1.2

Winter season values,

in millimeters per day

0.0

0.5

1.0

1.5

2.0

2.5

3.0

0

5

10

15

20

25

0.0

0.2

0.4

0.6

0.8

1.0

1.2

Spring season values,

in millimeters per day

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

0

10

20

30

40

50

1930 1950 1970 1990 2010

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

Summer season values,

in millimeters per day

1930 1950 1970 1990 2010

0.0

0.5

1.0

1.5

2.0

1930 1950 1970 1990 2010

0

5

10

15

20

25

Figure 1−28. Streamflow statistics (circles) in units of millimeters per day, annual values and seasonal values

Fall (Sept., Oct., and Nov.,), Winter (Dec., Jan., and Feb.), Spring (Mar., Apr., and May), and Summer (June, July, and Aug.)

and locally weighted scatterplot smooth (solid curve) for Reed Creek at Grahams Forge, Va., 1930−2010.
54 Spatial and Temporal Trends in Runoff at Long-Term Streamgages within and near the Chesapeake Bay Watershed

Figure 1−29. Streamflow statistics (circles) in units of millimeters per day, annual values and seasonal values; fall 

(September, October, and November), winter (December, January, and February), spring (March, April, and May), and 

summer (June, July, and August), and locally weighted scatterplot smooth (solid curve) for North Fork Holston River near 

Saltville, Va., 1930−2010.

0.00

0.05

0.10

0.15

0.20

0.25

0.30

0.35

7−day minimum

Annual values,

in millimeters per day

0.0

0.5

1.0

1.5

2.0

2.5

annual mean

North Fork Holston River near Saltville, Va.

0

10

20

30

40

50

60

1−day maximum

0.00

0.05

0.10

0.15

0.20

0.25

0.30

0.35

Fall season values,

in millimeters per day

0.0

0.5

1.0

1.5

2.0

2.5

0

10

20

30

40

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

Winter season values,

in millimeters per day

0

1

2

3

4

5

0

10

20

30

40

50

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

Spring season values,

in millimeters per day

0

1

2

3

4

0

10

20

30

40

50

60

1930 1950 1970 1990 2010

0.0

0.1

0.2

0.3

0.4

0.5

0.6

Summer season values,

in millimeters per day

1930 1950 1970 1990 2010

0.0

0.5

1.0

1.5

2.0

1930 1950 1970 1990 2010

0

5

10

15

20

25

30

Figure 1−29. Streamflow statistics (circles) in units of millimeters per day, annual values and seasonal values

Fall (Sept., Oct., and Nov.,), Winter (Dec., Jan., and Feb.), Spring (Mar., Apr., and May), and Summer (June, July, and Aug.)

and locally weighted scatterplot smooth (solid curve) for North Fork Holston River near Saltville, Va., 1930−2010.
Appendix 55

Figure 1−30. Streamflow statistics (circles) in units of millimeters per day, annual values and seasonal values; fall 

(September, October, and November), winter (December, January, and February), spring (March, April, and May), and 

summer (June, July, and August), and locally weighted scatterplot smooth (solid curve) for Banister River at Halifax, Va., 

1930−2010.

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

7−day minimum

Annual values,

in millimeters per day

0.0

0.5

1.0

1.5

2.0

annual mean

Banister River at Halifax, Va.

0

20

40

60

80

100

1−day maximum

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

Fall season values,

in millimeters per day

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

0

20

40

60

80

100

0.0

0.2

0.4

0.6

0.8

1.0

1.2

Winter season values,

in millimeters per day

0.0

0.5

1.0

1.5

2.0

2.5

0

5

10

15

20

25

0.0

0.2

0.4

0.6

0.8

1.0

Spring season values,

in millimeters per day

0.0

0.5

1.0

1.5

2.0

2.5

3.0

0

5

10

15

20

25

30

1930 1950 1970 1990 2010

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

Summer season values,

in millimeters per day

1930 1950 1970 1990 2010

0.0

0.5

1.0

1.5

2.0

2.5

1930 1950 1970 1990 2010

0

10

20

30

40

50

60

Figure 1−30. Streamflow statistics (circles) in units of millimeters per day, annual values and seasonal values

Fall (Sept., Oct., and Nov.,), Winter (Dec., Jan., and Feb.), Spring (Mar., Apr., and May), and Summer (June, July, and Aug.)

and locally weighted scatterplot smooth (solid curve) for Banister River at Halifax, Va., 1930−2010.
56 Spatial and Temporal Trends in Runoff at Long-Term Streamgages within and near the Chesapeake Bay Watershed

Prepared by:

USGS Science Publishing Network

Raleigh Publishing Service Center

3916 Sunset Ridge Road

Raleigh, NC 27607

USGS Publishing Service Center staff:

Edited by Twila Darden Wilson

Layout and illustrations by James A. Tomberlin, 

 figure 1 by Timothy W. Auer

For additional information regarding this publication, contact:

Director

USGS Virginia Water Science Center

1730 East Parham Road

Richmond, VA 23228

(804) 261-2600

email: dc_va@usgs.gov

Or visit the USGS Virginia Water Science Center Web site at:

http://va.water.usgs.gov
Appendix 57
By K.C. Rice and R.M. Hirsch—Spatial and Temporal Trends in Runoff at Long-Term Streamgages within and near the Chesapeake Bay Watershed—Scientific 

Investigations Report 2012–5151

Printed on recycled paper