U.S. GEOLOGICAL SURVEY

Trends in Streamflow, River Ice, and 

Snowpack for Coastal River Basins in Maine 

During the 20th Century

U.S. DEPARTMENT OF THE INTERIOR

Water-Resources Investigations Report 02-4245

U.S. GEOLOGICAL SURVEY

In cooperation with the

MAINE ATLANTIC SALMON COMMISSION
U.S. GEOLOGICAL SURVEY

Cover Photograph: Sheepscot River at North Whitefield, Maine, late January, 2001. Photograph courtesy of Jason Cyr.
U.S. GEOLOGICAL SURVEY

Water-Resources Investigations Report 02-4245

Trends in Streamflow, River Ice, and 

Snowpack for Coastal River Basins in Maine 

During the 20th Century

In cooperation with the

MAINE ATLANTIC SALMON COMMISSION

By Robert W. Dudley and Glenn A. Hodgkins

Augusta, Maine

2002
U.S. DEPARTMENT OF THE INTERIOR

GALE A. NORTON, Secretary

U.S. GEOLOGICAL SURVEY

Charles G. Groat, Director

For additional information write to: Copies of this report can be purchased 

from:

U.S. Geological Survey

Branch of Information Services

Box 25286

Federal Center

Denver, CO 80225

The use of firm, trade, and brand names in this report is for identification purposes 

only and does not constitute endorsement by the U.S. Government.

District Chief

U.S. Geological Survey

196 Whitten Road

Augusta, ME 04330

http://me.water.usgs.gov
Contents iii

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

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

Description of the Study Area.................................................................................................................................... 2

Data Collection .......................................................................................................................................................... 4

Streamflow ........................................................................................................................................................ 4

Ice ...................................................................................................................................................................... 4

Snow.................................................................................................................................................................. 5

Data Analysis ............................................................................................................................................................. 5

Streamflow ........................................................................................................................................................ 5

Ice ...................................................................................................................................................................... 8

Snow.................................................................................................................................................................. 8

Trends in Streamflow, River Ice, and Snowpack for Coastal River Basins in Maine During the 20th Century....... 10

Streamflow ........................................................................................................................................................ 10

Ice ...................................................................................................................................................................... 17

Snow.................................................................................................................................................................. 19

Synthesis of Trends in Streamflow, River Ice, and Snowpack.................................................................................. 20

Summary .................................................................................................................................................................... 25

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

LIST OF FIGURES

1. Map showing location of USGS-gaged coastal river basins in Maine....................................................................... 3

2. Map showing locations of coastal snow-survey sites in Maine and March 1 mean snowpack 

equivalent water content, in inches................................................................................................................. 6

3. MOVE.1 relation between the streamflows at Machias and Narraguagus Rivers, Maine............................................ 7

4. Generalized hydrograph showing date of peak flow and seasonal center-of-volume date for 

a typical spring, for coastal river basins in Maine............................................................................................. 8

5. Generalized hydrograph showing date of peak flow and seasonal center-of-volume date for an 

atypical spring with a winter thaw event, for coastal river basins in Maine ......................................................... 9

6. February daily mean streamflows for the Narraguagus Extended Record, coastal Maine. Loess 

regression lines are based on a 45-year weighting window................................................................................ 11

7. May daily mean streamflows for the Narraguagus Extended Record, coastal Maine. Loess regression

lines are based on a 45-year weighting window ............................................................................................... 12

8. Trend in spring center-of-volume date for the Narraguagus Extended Record, coastal Maine. 

Loess regression line is based on a 45-year weighting window.......................................................................... 16

9. Trend in spring peak-flow date for the Narraguagus Extended Record, coastal Maine. 

Loess regression line is based on a 45-year weighting window.......................................................................... 16

10. Trends in first ice-on date for coastal rivers in Maine. Loess regression lines are based on a

35-year weighting window ............................................................................................................................ 18

CONTENTS
iv Trends in Streamflow, River Ice, and Snowpack for Coastal River Basins in Maine During the 20th Century

LIST OF FIGURES —continued

11. Trends in last ice-off date for coastal rivers in Maine. Loess regression lines are based on a 

35-year weighting window ............................................................................................................................ 18

12. Trends in total number of days of ice effect for coastal rivers in Maine. Loess regression lines are 

based on a 35-year weighting window ............................................................................................................ 19

13. Trends in snow depth, equivalent water, and snow density at the Amherst snow-survey site for the 

March 1 survey date, coastal Maine. Loess regression lines based on a 35-year weighting window ...................... 21

14. Trends in snow depth, equivalent water, and snow density at the Amherst snow-survey site for the 

March 15 survey date, coastal Maine. Loess regression lines based on a 35-year weighting window..................... 22

. 15. Trends in snow depth, equivalent water, and snow density at the Amherst snow-survey site for the 

April 1 survey date, coastal Maine. Loess regression lines based on a 35-year weighting window ........................ 23

.

LIST of TABLES

1. Coastal river gages in Maine........................................................................................................................... 2

2. Snow-survey sites and survey dates analyzed for trends for coastal river basins in Maine ..................................... 10

3. Statistical significance (p-values) and trend direction for daily mean streamflow statistics for the 

Narraguagus Extended Record, coastal Maine, period of record: 1906-21, 1929-2000.......................................... 11

4. Statistical significance (p-values) and trend direction for daily mean streamflow statistics for the Machias

River, coastal Maine, period of record: 1906-21, 1929-77 ................................................................................. 12

5. Statistical significance (p-values) and trend direction for daily mean streamflow statistics for the East

Machias River, coastal Maine, period of record: 1927-58 .................................................................................. 13

6. Statistical significance (p-values) and trend direction for daily mean streamflow statistics for the 

Narraguagus River, coastal Maine, period of record: 1948-2000 ....................................................................... 13

7. Statistical significance (p-values) and trend direction for daily mean streamflow statistics for the 

West Branch Union River, coastal Maine, period of record: 1909-19, 1929-79.................................................... 14

8. Statistical significance (p-values) and trend direction for daily mean streamflow statistics for the 

Sheepscot River, coastal Maine, period of record: 1938-2000 ............................................................................ 14

9. Statistical significance (p-values) and trend direction for daily mean streamflow statistics for the

Royal River, coastal Maine, period of record: 1949-2000............................................................................................ 15

10. Statistical significance (p-values) and trend direction for Julian dates of spring and fall peak 

streamflows and centers-of-volume for coastal river basins in Maine.................................................................. 15

11. Statistical significance (p-values) and trend direction for spring and fall peak flow magnitudes

and seasonal and annual runoff volumes for coastal river basins in Maine........................................................... 15

12. Statistical significance (p-values) and trend direction for total number of days of ice,

first ice-on date, and last ice-off date for coastal river basins in Maine................................................................ 17

13. Statistical significance (p-values) and trend direction for snow data for the March 1 survey

date for coastal river basins in Maine .............................................................................................................. 21

14. Statistical significance (p-values) and trend direction for snow data for the March 15 survey

date for coastal river basins in Maine .............................................................................................................. 22

15. Statistical significance (p-values) and trend direction for snow data for the April 1 survey

date for coastal river basins in Maine .............................................................................................................. 23
Contents v

CONVERSION FACTORS, VERTICAL DATUM

To convert temperature in degrees Fahrenheit (°F) to degrees Celsius (°C) use the following equation:

°C = 5/9 * (°F - 32)

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

Multiply By To obtain

inch (in.) 25.4 millimeter

foot (ft) 0.3048 meter

mile (mi) 1.609 kilometer

cubic foot (ft3) 0.02832 cubic meter

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

Abstract 1

Trends in Streamflow, River Ice, and Snowpack for 

Coastal River Basins in Maine During the 20th Century

by Robert W. Dudley and Glenn A. Hodgkins

ABSTRACT

Trends over the 20th Century were examined in 

streamflow, river ice, and snowpack for coastal river 

basins in Maine. Trends over time were tested in the 

timing and magnitude of seasonal river flows, the 

occurrence and duration of river ice, and changes in 

snowpack depth, equivalent water content, and density. 

Significant trends toward earlier spring peak flow and 

earlier center-of-volume runoff dates were found in the 

extended streamflow record spanning 1906-21 and 

1929-2000. Only one of the six coastal rivers in the 

study analyzed for trends in cumulative runoff had a 

significant change in total annual runoff volume. Last 

spring river-ice-off dates at most coastal streamflowgaging stations examined are trending to earlier dates. 

Trends in later fall initial onset of ice also are evident, 

although these trends are significant at fewer stations 

than that observed for ice-off dates. Later ice-on dates 

in the fall and (or) earlier ice-off dates in the spring 

contribute to a statistically significant decrease over 

time in the total number of days of ice occurrence at 

most gaging stations on coastal rivers in Maine. The 

longest, most complete snow records in coastal Maine 

indicate an increase in snow density for the March 1 

snow-survey date during the last 60 years. The historical trends in streamflow, ice, and snow are all consistent with an earlier onset of hydrologic spring 

conditions in coastal Maine.

INTRODUCTION 

Global land and ocean surface temperatures have 

increased between 0.7 and 1.4 oF (95-percent confidence interval) during the 20th Century with most of 

the warming taking place during 1910-45 and from 

1976 to the present (Intergovernmental Panel on 

Climate Change, 2001). Global annual surface temperature trends, calculated from combined land-surface air 

and sea-surface temperature data and presented in the 

Third Assessment Report of the Intergovernmental 

Panel on Climate Change (IPCC) (2001), show an 

overall surface temperature trend for New England for 

the period 1901-2000 of 0.4 oF per decade. The trend is 

variable over the century—for the period from 1910 to 

1945, the temperature warmed at about 0.7 o

F per 

decade, then cooled from 1946 to 1975 at a rate of 

about -0.9 o

F per decade, and warmed again from 1976 

to 2000 at about 1.1 o

F per decade. Greatest seasonal 

warming rates for New England during 1976-2000 

occurred during the winter months of December, 

January, and February (Intergovernmental Panel on 

Climate Change, 2001). 

In addition to warming trends in air temperature, 

precipitation also has increased in the mid- to high latitudes of the northern hemisphere during the last 

century. Land-surface precipitation records show an 

increase of 0.5 to 1 percent per decade, and total cloud 

cover has increased by about 2 percent over many midto high latitude land areas since the beginning of the 

20th century (Intergovernmental Panel on Climate 

Change, 2001). 

Because snowpack and the timing of snowmelt is 

a major component of the hydrology of river basins in 

New England, the hydrologic response of the region to 

warmer winters may be important. In a study of 13 river 

basins throughout Vermont, New Hampshire, and 

Massachusetts, Hartley and Dingman (1993) demonstrated sensitivity of snowmelt-dominated runoff to air 

temperature. They found that, on average, maximum 

streamflows (in spring) occur earlier in basins with 

higher average air temperatures. 

The flow of a river represents the integrated 

basin response to precipitation, temperature, and other 

climatic inputs. Because the methods of collecting 

hydrologic data differ from those associated with 

collecting meteorological data, analyzing the effects of 

climate change on hydrology of stable, unregulated 
2 Trends in Streamflow, River Ice, and Snowpack for Coastal River Basins in Maine During the 20th Century

basins provides a method of quantifying climate 

change that is independent of analyses of meteorological measures such as air temperature (Zhang and 

others, 2001). To analyze these effects of climate 

change in unregulated basins, the U.S. Geological 

Survey (USGS) and the Maine Atlantic Salmon 

Commission began a cooperative study in 2001. Of 

particular concern are seasonal changes in water 

temperatures and streamflows that may affect the 

behavior and subsequent survivability of Atlantic 

salmon in Maine. Because Maine’s coastal rivers are at 

the southern extent of the Atlantic salmon’s habitat 

range, Atlantic salmon in Maine may be particularly 

sensitive to climatic changes that affect hydrologic or 

thermal regimes. 

This report presents the data and methods used to 

determine whether there are trends in hydrologic and 

cryospheric variables for coastal river basins in Maine 

that would indicate a hydrologic response to changes in 

climate. The timing and magnitude of streamflow, river 

ice, and snowpack data are used to quantify hydrologic 

changes, or lack thereof, in response to changes in 

climate for coastal river basins in Maine during the last 

century. The trend analyses presented in this report will 

be used to help determine if these hydrologic changes 

relate to historical data on Atlantic salmon smolt sizes, 

run timing or numbers and (or) adult return rates, or 

other biological and population data. Further analysis 

ultimately could lead to the development of predictive 

models of Atlantic salmon behavior and projected 

survivability. 

DESCRIPTION OF THE STUDY AREA 

The study area covers all coastal river basins in 

Maine that either currently are gaged or have been 

gaged by the USGS (table 1, fig. 1). The basins are 

heavily forested and are characterized by low-relief 

rolling topography with no urban development. The 

coastal river basins lie in a hydrophysiographic region 

of broad lowlands that were inundated by the ocean 

during deglaciation (Randall, 2000). Consequently, the 

surficial geologic materials in the basins are predominantly glacial till and fine and coarse-grained glaciomarine deposits with some ice-contact glaciofluvial 

deposits, eskers, and bedrock (Thompson and Borns, 

1985). 

The greatest changes in land use in Maine during 

the 20th Century have been the replacement of agriculture and pasture lands by forest. The State’s overall 

forest cover, estimated at 70 percent in 1900, increased 

to 90 percent by 1995 (Irland, 1998). Six basins in close 

proximity in eastern coastal Maine (fig. 1) are in a 

sparsely populated part of the State. During the period 

1880-1995, the estimated increase in forested area in 

eastern coastal Maine varies from about 18 to 22 

percent (Irland, 1998). The remaining two river basins, 

Sheepscot and Royal, are in a historically more populated part of the State that was more heavily deforested. 

Reforestation estimates in these basins range from 

approximately 100 to 186 percent during the same time 

period (Irland, 1998). 

Number Name

01021200 Dennys River at Dennysville, Maine 44o

 54' 03" 67o 14' 56" 92.9 1955-98 na

01021500 Machias River at Whitneyville, Maine 44o

 43' 23" 67o 31' 15" 458 1906-21, 1929-77 1929-77

01022000 East Machias River near East Machias, Maine 44o

 46' 05" 67o 24' 30" 251 1927-58 na

01022260 Pleasant River near Epping, Maine 44o

 41' 52" 67o 47' 16" 60.6 1980-91 1980-91

01022500 Narraguagus River at Cherryfield, Maine 44o

 36' 29" 67o 56' 10" 227 1948-2000 1948-2000

01023000 West Branch Union River at Amherst, Maine 44o

 50' 25" 68o 22' 22" 148 1909-19, 1929-79 1929-79

01038000 Sheepscot River at North Whitefield, Maine 44o

 13' 23" 69o 35' 38" 145 1938-2000 1938-2000

01060000 Royal River at Yarmouth, Maine 43o

 47' 57" 70o 10' 45" 141 1949-2000 1949-2000

Period of record 

for streamflow 

data

Period of 

record for ice 

data

U.S. Geological Survey streamflow gaging station Latitude 

(north)

Longitude 

(west)

Drainage 

area (square 

miles)

Table 1. Coastal river gages in Maine

[na, not available]
Description of the Study Area 3

Figure 1. Location of USGS-gaged coastal river basins in Maine.
4 Trends in Streamflow, River Ice, and Snowpack for Coastal River Basins in Maine During the 20th Century

The climate of Maine’s coast is typified by mild 

summers and cold winters. Records from National 

Weather Service (NWS) stations indicate normal 

annual temperatures, based on the 30-year period 1961-

90, of 45.4 o

F in Portland and 45.6 oF in Eastport (fig. 

1). Mean monthly temperatures range from 20.8 o

F in 

January to 68.6 o

F in July in Portland and 21.8 oF in 

January to 63.0 o

F in July in Eastport. The average 

annual precipitation is 44.3 in. at Portland and 43.4 in. 

at Eastport and is fairly evenly distributed throughout 

the year (U.S. Department of Commerce, National 

Oceanic and Atmospheric Administration, 2000). 

DATA COLLECTION 

Data sets were assembled for streamflow, river 

ice, and snowpack data and were used to analyze 

historical trends. The methods of how these data sets 

were assembled are described below. 

Streamflow 

Daily mean streamflow data for the eight streamflow-gaging stations (table 1, fig. 1) were obtained 

from the USGS National Water Information System 

(NWIS) accessed on the World Wide Web at URL 

http://water-data.usgs.gov/nwis. The stations have 

periods of record ranging from 11 to 65 years in length 

with an average of 48 years (table 1). Because the 

Pleasant River near Epping (USGS station number 

01022260) has only 11 years of record, the Pleasant 

River station was not used in any historical trend analyses for this report. The flow of the Dennys River at 

Dennysville (01021200) is regulated by a dam at the 

outlet of Meddybemps Lake 14 mi upstream with a 

usable capacity of about 1.5 billion ft3 (Nielsen and 

others, 1998). Because of the effect of regulation on 

this river, streamflow data for this gaging station was 

omitted from any historical trend analyses. 

Two additional stations, Machias River at Whitneyville (01021500) and East Machias River near East 

Machias (01022000), have or historically have had 

some minor low-flow regulation. The regulation at 

these sites is thought to be small enough to have no 

effect on the computation of a monthly mean streamflow value computed on the basis of the daily mean 

streamflow (Slack and Landwehr, 1992). Although 

monthly means and longer term (for example, seasonal 

or annual) means and high-flow statistics are thought to 

be unaffected by regulation at these sites, it is important 

to note that low-flow statistics and averages computed 

on timeframes shorter than 1 month (especially during 

summer months) could be affected and should not be 

interpreted as representative of natural flow conditions; 

such statistics are censored in this report. The 

remaining four stations, Narraguagus River at Cherryfield (01022500), West Branch Union River at 

Amherst (01023000), Sheepscot River at North Whitefield (01038000), and the Royal River at Yarmouth 

(01060000) have little or no regulation, and daily and 

longer averages of streamflow are representative of 

natural conditions (Slack and Landwehr, 1992). 

Ice 

Ice data were obtained from annual USGS 

Water-Resources Data reports for Maine, USGS 

Water-Supply Papers for the North Atlantic Slope 

Drainage Basins, and USGS files used to compute 

streamflow. The ice data set consists of days during 

which river ice was present in sufficient quantities to 

cause backwater at the gaging station and affect the 

computation of streamflow (Rantz, 1982). River ice 

can include both surface ice and anchor ice near the 

hydraulic control at the gaging station. The days of iceeffect are referred to as “ice-days.” The first day of ice 

effect following a period of no ice-effect is called an 

“ice-on” day. The last day of ice-effect for a consecutive period of ice-days is called an “ice-off” day. The 

occurrence of ice-days can be discontinuous 

throughout the winter season; thus, for any given 

winter season, there can be many ice-on and ice-off 

dates. 

At most streamflow-gaging stations in the early 

streamflow record (before the 1930’s), ice-days were 

determined by a local observer. Observers were later 

replaced by continuous recorders. In an effort to avoid 

any potential bias from an observer, only ice-effect 

data determined from a continuous recorder is used for 

this study. For this reason, data from a brief period of 

observer ice-days at the West Branch Union River from 

1910 to 1919 was not used. No ice data were available 

for the Dennys and East Machias River stations 

because of the proximity of these stations to upstream 

regulation that kept the gaged river reach free of ice. 

There are no ice data for the Machias River station 

prior to 1929 for the same reason; however, in 1929, 

the station on the Machias River was relocated to a site 

farther downstream where conditions were favorable 

for ice formation. 
Data Analysis 5

Snow 

Snow data were obtained from the Maine Cooperative Snow Survey Program database that stores 

snow depth and equivalent water content by site and 

survey date. The snow-survey program is run jointly by 

the Maine Geological Survey (MGS) and the USGS. 

The data are collected by many agencies and private 

companies on a regular basis in late winter and spring 

(Loiselle and Hodgkins, 2002). 

Several criteria were used to select the 11 coastal 

snow-survey sites used for this study. First, all snowsurvey sites either in or near the eight coastal drainage 

basins were selected. These were then further narrowed 

to include only sites with records up to the year 2001 

and those with records spanning at least 40 years. The 

average period of record for the 11 snow-survey sites is 

55 years, with a minimum of 43 years at Dedham and a 

maximum of 79 years at Amherst (fig. 2). The snowsurvey site at Amherst has the longest and most 

complete snow-survey record in this study.

DATA ANALYSIS 

Temporal trends were analyzed for all data sets 

using the non-parametric Mann-Kendall test (Helsel 

and Hirsch, 1992), because changes over time do not 

seem to be linear. The data were smoothed for graphical presentation and serial correlation testing by use of 

locally weighted regression (Loess) (Cleveland and 

Devlin, 1988) with locally linear fitting and a robustness feature. There must be no serial correlation for the 

p-values from the Mann-Kendall test to be correct. 

Serial correlations in the trend tests were analyzed by 

computing the Durbin-Watson statistic on the residuals 

of the Loess regressions for each river with a significant temporal trend (p-value less than 0.1) in any category. In this report, a p-value less than or equal to 0.10 

is referred to as significant and a p-value less than or 

equal to 0.01 is referred to as highly significant. All net 

changes cited in this report are computed using the endpoint values of Loess regression lines. 

Julian dates were used for all annual timing analyses in this investigation except for those of ice-effect. 

For ice-effect dates, a modified Julian date system 

called a Water Year Julian date (WYJD) was used. The 

term “water year” denotes the 12-month period from 

October 1 to September 30 and is designated by the 

calendar year in which it ends and which includes 9 of 

the 12 months. Thus, the year ending September 30, 

1996 is called “water year 1996.” The WYJD system 

begins numbering on October 1. This system was used 

to analyze ice-effect in order to capture the entire 

winter season in a single, sequentially numbered datesystem. A small bias in Julian date is introduced by 

using a calendar date rather than using timing relative 

to the vernal equinox. The maximum bias is 0.8 day 

(Sagarin, 2001), for sites with data from 1900 to 2000.

Streamflow 

Each daily mean streamflow data set was used to 

construct monthly, annual, and seasonal data sets 

described below. In addition to these data sets, an 

extended-record data set was constructed using streamflow records from the Narraguagus and Machias Rivers 

to examine trends in a single streamflow record spanning the 95-year period 1906-2000. The method of 

streamflow data extension, called MOVE.1 (Maintenance Of Variance Extension, type 1), uses the relation 

between the common data period of two streamflow 

records and produces streamflow estimates with a 

statistical distribution similar to that expected had the 

streamflow actually been measured (Helsel and Hirsch, 

1992). In the case of the Narraguagus and Machias 

River data sets, the base-10 logarithms of streamflow 

from their common 30-year period of 1948-77 was 

used to develop the relation between the stations (fig. 

3). Using this relation, the Narraguagus record was 

extended backwards to cover the additional years of 

1906-21 and 1929-47, thus generating a streamflow 

data set that spans from 1906 to 1921 and from 1929 to 

2000. The Narraguagus Extended Record is referred to 

as NER in the remainder of this report.

The linear relation (in log space) between the 

streamflow at the Machias and Narraguagus Rivers has 

an overall correlation coefficient of 0.93 (fig. 3). 

Because of the minor regulation of low streamflows on 

the Machias River and the absence of regulation at 

Narraguagus, the relation of low streamflows between 

the two rivers probably shows some non-linearity and 

greater variability than the relation at the higher range 

of streamflows (fig. 3). Low-flow data for the NER 

were censored because of the poor relation between the 

Machias and Narraguagus Rivers at the low end of the 

MOVE.1. Similarly, low-flow data for the Machias and 

East Machias Rivers were censored because of possible 

regulation effects. Monthly and annual data sets were 

not analyzed for trends if any streamflow value in the 

data set was lower than the minimum August mean 

flow for that station. 
6 Trends in Streamflow, River Ice, and Snowpack for Coastal River Basins in Maine During the 20th Century

STUDY AREA

01021200

01021500

01022000

01022500

01022260

01023000

01038000

01060000

SCALE 0

0

40 MILES

60 KILOMETERS

70o

45o

44o

69o

68o 67o

Base from U.S. Geological Survey

digital files, scale 1:2,000,000

Snow pack contours from Loiselle

and Hodgkins (2002)

River

River

River

Penobscot

Kennebec

Atlantic Ocean

Androscoggin

Eastport

Augusta

Portland

6

6

7

5

4

4

4

5

4

Baring

Cooper

mountain

Amherst

Franklin

Dedham

Whitneyville

Bucksport

Falmouth

Topsham

Auburn

Augusta

Streamflow-gaging station and

identification number

Snow-survey site and town

identifier

City or town location

Line of March 1 snowpack mean

equivalent water content, contour

interval 1 inch

Depression line of March 1 snowpack

mean equivalent water content,

contour interval 1 inch

01023000

Portland

6

5

Topsham

EXPLANATION

Figure 2. Locations of coastal snow-survey sites used in this study and March 1 mean snowpack equivalent water content, in 

inches.
Data Analysis 7

To examine trends over time in the quantity and 

timing of monthly and annual streamflow, selected 

streamflow statistics were computed on a monthly and 

calendar year basis: minimum, 75th percentile, median 

(50th percentile), 25th percentile, and maximum. 

To examine trends over time in the timing and 

magnitude of seasonal streamflows, the daily mean 

flow data were partitioned into the following seasons: 

winter/spring (January 1 to May 31), spring/summer 

(June 1 to September 30) and fall/winter (October 1 to 

December 31). The winter/spring seasonal window 

was chosen in an effort to capture all the spring snowmelt runoff in a single seasonal window. The 

spring/summer window was terminated at the end of 

September because deciduous trees lose their leaves in 

October and November, and evapotranspiration 

accordingly decreases at this time. The fall/winter 

seasonal window was chosen to capture high streamflows that often occur at this time of year. Seasonal 

volumes were computed by summing the daily 

volumes from the start to the end of each seasonal 

window for each of the three seasonal windows. 

The largest streamflows in Maine typically are in 

the spring when rain falls on a melting snowpack or on 

saturated soils. High streamflows also can occur in the 

fall after evapotranspiration decreases substantially 

and repeated rains saturate the soil. Hurricanes and 

tropical storms in the fall also sometimes will leave 

large amounts of rainwater in their path resulting in 

high streamflows. Because high streamflows tend to 

take place during the spring and fall, the center-ofvolume dates and the peak-flow dates were computed 

for the winter/spring and fall/winter seasonal windows. 

The center-of-volume date is the date on which half the 

total volume of water for a given period of time flows 

by a streamflow-gaging station. For this study, the 

seasonal center-of-volume date (SCVD) was computed 

as the first date, from the start of the season, on which 

at least half of the seasonal volume had flowed by a 

gaging station (figs. 4 and 5). The peak-flow date is the 

10 100 1,000 10,000 100,000

STREAMFLOW, IN CUBIC FEET PER SECOND, MACHIAS RIVER AT WHITNEYVILLE, MAINE

1

10

100

1,000

10,000

Correlation coefficient = 0.93

 STREAMFLOW, IN CUBIC FEET PER SECONDNARRAGUAGUS RIVER AT CHERRYFIELD, MAINE

Concurrent daily-mean streamflow

February 1948 to September 1977

MOVE.1 line

Figure 3. MOVE.1 relation between the streamflow at Machias and Narraguagus Rivers, Maine.
8 Trends in Streamflow, River Ice, and Snowpack for Coastal River Basins in Maine During the 20th Century

date on which the highest daily mean flow occurs 

during a given time period (figs. 4 and 5). The annual 

winter/spring and fall/winter peak streamflows used in 

this report were the largest daily mean streamflows 

between January 1 and May 31, and October 1 to 

December 31, respectively. The SCVD is a useful variable for examining streamflow trends over time as it is 

more resistant to noise in the data than the peak-flow 

date. The SCVD also is more sensitive to changes in the 

timing of flow than is the percentage of flow occurring 

in one or more fixed months (Court, 1962). 

The generalized hydrograph illustrated in figure 

4 has a peak flow occurring (April 13) during the spring 

snowmelt in April. The runoff volume is the integrated 

area under the hydrograph. The spring SCVD is on 

April 12, located near the date of the peak flow. An 

early thaw event at the end of January is illustrated in 

Figure 5. The peak flow on January 29 is larger than the 

peak flow that occurs during the bulk of the spring 

snowmelt in late March and April. The spring SCVD 

(March 28), however, corresponds more closely to the 

bulk of the spring snowmelt. 

Ice 

Three variables were derived from the ice-effect 

data to test for significant changes over time: each 

water year’s first ice-on day, last ice-off day, and total 

cumulative days of ice-effect. Because the occurrence 

of ice can be discontinuous throughout the winter, the 

total days of ice-effect is not simply the difference 

between the first day of ice-on and day of last-ice-off. 

The Mann-Kendall trend test was used to test for significant changes over time in these three variables. 

Snow 

Because snow surveys in Maine are not done on 

specific dates, the snow data for each survey site were 

 January February March April May

DATE

DAILY MEAN STREAMFLOW, IN CUBIC FEET PER SECOND

Center of volume

date: April 12

Peak flow date:

April 13

SPRING SEASONAL WINDOW, JANUARY 1 TO MAY 31

Figure 4. Generalized hydrograph showing date of peak flow and seasonal center-of-volume date for a typical spring, for coastal 

river basins in Maine. 
Data Analysis 9

grouped by arbitrary survey dates bracketed by 2-week 

windows-that is, +/- 1 week each side of each survey 

date. The chosen survey dates and their corresponding 

windows were: February 15, February 8-21; March 1, 

February 22-March 7; March 15, March 8-22; April 1, 

March 23-April 7; and April 15, April 8-21. For any 

given year, if more than one snow measurement fell 

within a window for a given survey date, the date most 

closely corresponding to the survey date was retained. 

If there was a tie, the average of the data values was 

used. 

Historically, the snow-survey sites were not 

sampled every two weeks for the entire late-winter 

season and often not even every year. As a result, the 

snow data, grouped by survey dates, contain missing 

values. Only survey-date data sets with at least 60-

percent completeness were retained for analysis. 

Historically, snow-survey efforts have been greatest 

near March 1; therefore the March 1 survey date 

yielded the most complete data sets for the most 

number of sites. 

The remaining survey-date data sets were evaluated for potential bias associated with their missing 

values. If values were missing because snow conditions 

governed whether or not surveys were done, this situation could introduce bias. It was assumed that if snow 

conditions governed the decision to sample, only a nosnow condition would affect decision making. If values 

were missing because of a decision process unrelated to 

the snow conditions, such as sampling governed by a 

specific date, or no sampling at all for a particular year, 

then the missing values could be assumed to be unbiased-that is, had the snow been measured, it would 

have fallen within the normal distribution and variability of the measured values. As a result of this bias 

analysis, it was determined that all the data for the April 

15 survey date could be biased because snow conditions (usually no snow) late in the winter season likely 

 January February March April May

DATE

DAILY MEAN STREAMFLOW, IN CUBIC FEET PER SECOND

SPRING SEASONAL WINDOW, JANUARY 1 TO MAY 31

Center of volume

date: March 28

Peak flow date:

January 29

Figure 5. Generalized hydrograph showing date of peak flow and seasonal center-of-volume date for an atypical spring 

with a winter thaw event, for coastal river basins in Maine.
10 Trends in Streamflow, River Ice, and Snowpack for Coastal River Basins in Maine During the 20th Century

influenced whether sampling was or was not done, 

resulting in an under-representation of zero snowpack. 

The remaining survey dates were determined to be 

unbiased because it has been and still is common for 

snow to still be on the ground from mid-February to 

early April in coastal Maine. 

The survey-date data sets also were evaluated for 

potential bias associated with sampling date to determine if the sampling date moved systematically over 

time within the 2-week window for a given survey date 

and location. The Julian date of each survey was tested 

for trends over time using a non-parametric MannKendall trend test. As a result of this bias analysis, the 

following survey-site, survey-date pairs were eliminated because of potential sampling-date bias: 

Augusta, March 1; Baring, March 1; Topsham, March 

15; Dedham, March 15; and Whitneyville, March 15. 

Trend tests were run for the remaining unbiased sitesurvey date combinations (table 2).

TRENDS IN STREAMFLOW, RIVER ICE, 

AND SNOWPACK FOR COASTAL RIVER 

BASINS IN MAINE DURING THE 20TH 

CENTURY 

Streamflow 

Based on the Narraguagus Extended Record 

(NER), streamflows have increased in winter and early 

spring and decreased in late spring and early summer 

(table 3); however, there are no significant trends in 

calendar-year streamflow statistics. The strongest 

trends for increasing (positive) streamflows were in 

February (fig. 6), and the strongest trends for decreasing (negative) streamflows were in May and June 

(table 3, fig. 7). These months have highly significant 

trends across nearly all flow frequencies.

Overall, the same trends in seasonal streamflows 

observed in the NER also are present in the six coastal 

rivers analyzed (tables 4 - 9); however, the trends are 

not as systematic across all river basins, and the overall 

trends exhibit less coherence than that observed in the 

longer record of the NER likely because of their shorter 

periods of record and variation in periods of time 

covered.

Four of the seven streamflow records have statistically significant trends for earlier spring SCVD (table 

10, fig. 8). The advance in spring SCVD for the NER is 

highly significant with a p-value less than 0.0001. The 

advance of the spring SCVD over the NER period of 

record is approximately 20 days, moving from midApril to late March (fig. 8). Although many of the 

trends over time do not appear to be linear, the trend in 

the spring SCVD for the NER is nearly so; thus, a rate 

of advance in the SCVD may be estimated at 2.1 days 

per decade. Only the Sheepscot River and the NER 

show statistically significant advances in spring peakflow date (fig. 9). Trends in the fall peak-flow date and 

fall center-of-volume date are mixed. Two of three 

significant results indicate a trend toward later fall peak 

streamflows and center-of-volume dates (table 10). 

Few of the trend test results for the magnitude of 

seasonal peak streamflows and the seasonal and annual 

runoff volumes are statistically significant (table 11). 

Table 2. Snow-survey sites and survey dates analyzed for trends for coastal river basins in Maine

[Snow data through 2001; A, site analyzed for historical trends; *, not enough data for this site and survey date to do trend test; b1, dataset eliminated because of possible snow-condition sampling bias; b2, dataset eliminated because of possible sampling-date bias]

15-Feb 1-Mar 15-Mar 1-Apr 15-Apr

Falmouth 43o

 44' 70o 15' 141 1958 *A* * *

Auburn 44o

 04' 70o 17' 289 1954 *A* * *

Topsham 44o

 00' 69o 57' 200 1958 * A b2 * *

Augusta 44o

 17' 69o 42' 203 1923 * b2 A * *

Bucksport 44o

 33' 68o 48' 118 1956 *A* * *

Dedham 44o

 38' 68o 33' 351 1959 * A b2 A b1

Amherst 44o

 50' 68o 27' 650 1930 A A A A b1

Franklin 44o

 38' 68o 07' 249 1943 *A* * *

Whitneyville 44o

 42' 67o 31' 98 1935 * A b2 * *

Cooper Mtn. 44o

 58' 67o 27' 505 1941 * *A* *

Baring 45o

 07' 67o 20' 200 1956 * b2 A * *

Status of survey-date dataset Site name Latitude Longitude Altitude 

(feet)

First year of 

record
Trends in Streamflow, River Ice, and Snowpack for Coastal River Basins in Maine During the 20th Century 11

1900 1920 1940 1960 1980 2000

YEAR

100

1,000

200

300

400

500

600

700

800

900

STREAMFLOW, IN CUBIC FEET PER SECOND

25th percentile

Median

75th percentile

(50th percentile)

Figure 6. February daily mean streamflows for the Narraguagus Extended Record, coastal Maine. Loess 

regression lines are based on a 45-year weighting window.

Minimum 75th Percentile Median Mean 25th Percentile Maximum

January 0.0707 + 0.0997 + 0.2714 + 0.0525 + 0.0441 + 0.0707 +

February .0020 + .0008 + .0014 + .0002 + .0008 + .0003 +

March .1486 + .1692 + .1982 + .0320 + .0235 + .0931 +

April .4327 - .0350 - .0226 - .1931 - .0910 - .7777 +

May * .0003 - .0001 - .0001 - .0001 - .0003 -

June * .0101 - .0059 - .0015 - .0040 - .0092 -

July * .0722 - .0511 - .0606 - .0283 - .2074 -

August * * * .2553 - .1252 - .9673 -

September * * * .8142 - .7315 - .7259 -

October * * .4178 + .9415 - .8776 + .3930 -

November * .1726 + .1175 + .1476 + .0882 + .5117 +

December * .1507 + .1658 + .0696 + .0538 + .0822 +

Annual * 0.9815 - 0.5314 + 0.7099 - 0.7078 - 0.2777 +

Streamflow statistic/Trend direction

Table 3. Statistical significance (p-values) and trend direction for daily mean streamflow statistics for the Narraguagus 

Extended Record, coastal Maine, period of record: 1906-21, 1929-2000

[p-values in bold are significant at less than or equal to 0.10; p-values in bold and underlined are highly significant at less than or equal to 0.01; +, 

upward trend over time; -, downward trend over time; *, censored data]
12 Trends in Streamflow, River Ice, and Snowpack for Coastal River Basins in Maine During the 20th Century

Table 4. Statistical significance (p-values) and trend direction for daily mean streamflow statistics for the 

Machias River, coastal Maine, period of record: 1906-21, 1929-77

[p-values in bold are significant at less than or equal to 0.10; p-values in bold and underlined are highly significant at less than or equal 

to 0.01; +, upward trend over time; -, downward trend over time; *, censored data] 

1900 1920 1940 1960 1980 2000

YEAR

100

1,000

200

300

400

500

600

700

800

900

2,000

3,000

4,000

25th percentile

5,000

STREAMFLOW, IN CUBIC FEET PER SECOND

Median

75th percentile

(50th percentile)

Figure 7. May daily mean streamflows for the Narraguagus Extended Record, coastal Maine. Loess regression lines are based on 

a 45-year weighting window.

Minimum 75th Percentile Median Mean 25th Percentile Maximum

January * 0.7325 + 0.9446 + 0.5546 + 0.6979 + 0.4548 +

February * .1191 + .1608 + .0574 + .1458 + .0134 +

March .7456 + .8620 - .4942 - .9908 - .6224 + .5701 -

April .9215 - .6306 + .7809 + .7065 + .8894 - .7325 +

May * .0071 - .0307 - .0907 - .1697 - .3848 -

June * .0080 - .0023 - .0006 - .0031 - .0055 -

July * .6058 - .2673 - .1981 - .0327 - .3307 -

August * * * .7264 - .3997 - .7850 +

September * * * .8634 + .8309 + .4584 +

October * * * .3661 - .3079 - .4173 -

November * .7898 - .9723 + .4041 + .2395 + .0559 +

December * * .1010 + .0294 + .0285 + .0088 +

Annual * 0.8034 - 0.1729 - 0.7089 - 0.4475 - 0.6950 +

Streamflow statistic/Trend direction
Trends in Streamflow, River Ice, and Snowpack for Coastal River Basins in Maine During the 20th Century 13

Table 5. Statistical significance (p-values) and trend direction for daily mean streamflow statistics for the 

East Machias River, coastal Maine, period of record: 1927-58

[p-values in bold are significant at less than or equal to 0.10; +, upward trend over time; -, downward trend over time; *, censored data]

Minimum 75th Percentile Median Mean 25th Percentile Maximum

January 0.4208 - 0.5752 - 0.6189 - 0.6247 - 0.5486 - 0.6190 -

February .7945 + .8128 + .7703 + .6586 + .5970 + .9120 +

March .5859 + .4614 + .0702 + .0496 + .1514 + .0057 +

April .4476 - .0690 - .2111 - .4162 - .7531 - .4117 -

May .9449 - .8841 + .6180 + .9267 - .9267 - .6073 -

June .6900 + .2897 + .3493 + .3494 + .3694 + .3300 +

July .1947 + .1072 + .1054 + .1176 + .1089 + .2226 +

August .6562 + .4294 + .4073 + .3187 + .4071 + .2794 +

September .9083 - .9939 + .9755 - .3573 + .5912 + .7184 +

October .2428 + .1875 + .1007 + .1876 + .1163 + .4678 +

November .4582 + .4630 + .9559 + .4300 - .5733 - .0637 -

December .4485 - .2242 - .1091 - .1258 - .1200 - .1465 -

Annual 0.9223 - 0.2656 + 0.6846 + 0.8138 + 0.8837 + 0.4120 -

Streamflow statistic/Trend direction

Table 6. Statistical significance (p-values) and trend direction for daily mean streamflow statistics for the 

Narraguagus River, coastal Maine, period of record: 1948-2000

[p-values in bold are significant at less than or equal to 0.10; p-values in bold and underlined are highly significant at less than or equal 

to 0.01; +, upward trend over time; -, downward trend over time] 

Minimum 75th Percentile Median Mean 25th Percentile Maximum

January 0.7726 + 0.9323 + 0.5983 + 0.5074 + 0.3677 + 0.3677 +

February .1533 + .1260 + .2208 + .2998 + .2997 + .2476 +

March .2210 + .3587 + .3587 + .2693 + .3158 + .2547 +

April .4267 + .2844 + .5703 - .8968 - .8329 - .8204 +

May .5060 + .3069 + .1783 + .3147 + .4173 + .4363 +

June .5702 - .5163 - .6265 - .4958 - .7213 - .6151 -

July .2631 - .1486 - .0195 - .0252 - .0222 - .0556 -

August * * * .9225 - .7456 - .5592 -

September * * * .6498 - .5482 - .4653 -

October *** .0517 - .0693 - .0125 -

November * * * .2845 - .6497 - .9483 -

December .2562 + .5376 + .2495 + .3812 + .4362 + .3809 +

Annual * 0.3535 - 0.9431 + 0.8166 + 0.0970 + 0.9858 +

Streamflow statistic/Trend direction
14 Trends in Streamflow, River Ice, and Snowpack for Coastal River Basins in Maine During the 20th Century

Minimum 75th Percentile Median Mean 25th Percentile Maximum

January 0.0909 + 0.1258 + 0.1846 + 0.1424 + 0.1605 + 0.2483 +

February .0162 + .0616 + .0794 + .0973 + .1011 + .0126 +

March .2509 + .5071 + .7937 + .2671 + .2754 + .7161 +

April .9695 + .4253 - .2020 - .4517 - .4478 - .6460 -

May .5487 + .3927 + .4252 + .5488 + .6831 + .8233 +

June .3820 - .6324 - .9035 - .8483 - .8934 + .8184 -

July .3961 - .6736 - .6460 - .7402 - .6278 - 1.0000

August .3968 - .4041 - .8567 - .8034 - .7699 + .7415 +

September .9503 + .8567 - .6185 + .7747 + .9901 + .6676 +

October .9542 - .9491 - .7546 + .8433 - .8733 - .6279 -

November .8783 - .8483 + .6691 + .5660 + .6972 + .5531 +

December .0946 + .0816 + .1274 + .0510 + .0376 + .0691 +

Annual 0.6241 - 0.6433 + 0.5065 + 0.4093 + 0.0486 + 0.5868 +

Streamflow statistic/Trend direction

Table 7. Statistical significance (p-values) and trend direction for daily mean streamflow statistics for the West 

Branch Union River, coastal Maine, period of record: 1909-19, 1929-79

[p-values in bold are significant at less than or equal to 0.10; +, upward trend over time; -, downward trend over time]

Minimum 75th Percentile Median Mean 25th Percentile Maximum

January 0.8127 + 0.3558 + 0.9661 + 0.5118 + 0.8745 + 0.6930 +

February .3816 + .3340 + .3017 + .2663 + .2021 + .1606 +

March .2849 + .4660 + .2386 + .0573 + .0703 + .0020 +

April .2769 - .2742 - .3133 - .7292 - .7155 - .6707 +

May .6662 - 1.0000 .9322 + .9178 - .6885 - .9758 +

June .9612 - .6530 + .6530 + .6840 + .4156 + .6433 +

July .8126 - .5718 - .8080 - .9806 - .8793 + .6707 +

August .5592 + .9225 + .7751 - .8985 + .9612 - .8363 +

September .6094 + .8315 + .3912 + .2560 + .4585 + .1142 +

October .2126 + .1447 + .0682 + .1157 + .0366 + .1978 +

November .2337 + .5275 + .6929 + .7020 + .5276 + .9467 +

December .5638 + .5001 + .7799 + .7292 + .9903 - .4698 -

Annual 0.8565 + 0.2494 + 0.3473 + 0.1228 + 0.2321 + 0.2816 +

Streamflow statistic/Trend direction

Table 8. Statistical significance (p-values) and trend direction for daily mean streamflow statistics for the 

Sheepscot River, coastal Maine, period of record: 1938-2000

[p-values in bold are significant at less than or equal to 0.10; p-values in bold and underlined are highly significant at less than or equal to 

0.01; +, upward trend over time; -, downward trend over time]
Trends in Streamflow, River Ice, and Snowpack for Coastal River Basins in Maine During the 20th Century 15

Minimum 75th Percentile Median Mean 25th Percentile Maximum

January 0.9676 + 0.9870 + 0.3759 - 0.7887 - 0.6260 - 0.9611 -

February .6725 - .4259 - .8264 - .9935 - .7886 + .9935 +

March .9676 + .6609 + .5210 + .3673 + .4403 + .0676 +

April .1622 - .0320 - .0206 - .0448 - .0193 - .4899 -

May .9935 - .7886 + .9611 + .8582 + .9353 + .5316 +

June .2197 - .5156 - .8454 + .8138 + .8012 + .6434 +

July .4594 - .3932 - .7948 - .7638 + .6609 + .6727 +

August .4111 - .6141 - .7267 - .9288 - .6726 - .9611 +

September .4995 - .4115 - .9029 - .8391 + .7823 + .9288 -

October .4496 + .1799 + .0390 + .1482 + .0522 + .2910 +

November .6786 + .3378 + .5211 + .6089 - .8327 - .1855 -

December .5918 + .9546 + .5862 - .2325 - .1801 - .3983 -

Annual 0.2871 - 0.6878 + 0.8018 + 0.8737 - 0.9068 - 0.0895 +

Streamflow statistic/Trend direction

Table 9. Statistical significance (p-values) and trend direction for daily mean streamflow statistics for the 

Royal River, coastal Maine, period of record: 1949-2000

[p-values in bold are significant at less than or equal to 0.10; +, upward trend over time; -, downward trend over time]

Streamflow-gaging 

station

Machias 0.0928 - 0.9338 - 0.0529 + 0.2498 +

East Machias 0.0823 - 0.2080 - 0.0348 + 0.0464 +

Narraguagus 0.4915 - 0.3764 - 0.2585 - 0.1623 -

West Branch Union 0.1757 - 0.2895 - 0.1286 + 0.0029 +

Sheepscot 0.0309 - 0.0604 - 0.0896 - 0.0946 -

Royal 0.1478 - 0.4744 - 0.1692 - 0.1574 -

NER <0.0001 - 0.0163 - 0.2627 + 0.5555 +

Fall peak flow Spring centerof-volume

Fall center-ofvolumeSpring peak 

flow

Streamflow-gaging 

station

Machias 0.6564 + 0.2379 + 0.8541 + 0.0191 - 0.2884 + 0.6999 -

East Machias .9593 - .6461 + .4444 + .5519 - .8784 - .9593 +

Narraguagus .6585 - .2273 - .6816 + .2096 + .6135 - .9246 -

West Branch Union .5921 + .3998 + .2406 + .9187 - .3260 + .1568 +

Sheepscot .3046 + .9467 - .1335 + .2362 + .5639 + .0856 +

Royal .3061 + .4747 + .7887 - .1600 + .8391 + .9935 +

NER 0.3727 + 0.6491 + 0.7797 + 0.0207 - 0.1328 + 0.8200 -

Fall total runoff 

volume

Total annual 

runoff volume

Spring peak 

streamflow

Fall peak 

streamflow

Spring total 

runoff volume

Summer total 

runoff volume

Table 10. Statistical significance (p-values) and trend direction for Julian dates of spring and fall peak streamflows 

and centers-of-volume for coastal river basins in Maine 

[p-values in bold are significant at less than or equal to 0.10; p-values in bold and underlined are highly significant at less than or equal to 0.01; 

+, upward trend over time; -, downward trend over time; <, less than; NER, Narraguagus Extended Record—see text]

Table 11. Statistical significance (p-values) and trend direction for spring and fall peak flow magnitudes and seasonal and 

annual runoff volumes for coastal river basins in Maine 

[p-values in bold are significant at less than or equal to 0.10; +, upward trend over time; -, downward trend over time; NER, Narraguagus Extended 

Record—see text]
16 Trends in Streamflow, River Ice, and Snowpack for Coastal River Basins in Maine During the 20th Century

1900 1920 1940 1960 1980 2000

YEAR

0

40

80

120

160

JULIAN DATE

1900 1920 1940 1960 1980 2000

YEAR

0

40

80

120

160

JULIAN DATE

Figure 8. Trend in spring center-of-volume date for the Narraguagus Extended Record, coastal Maine. Loess regression line is 

based on a 45-year weighting window. 

Figure 9. Trend in spring peak-flow date for the Narraguagus Extended Record, coastal Maine. Loess regression line is 

based on a 45-year weighting window.
Trends in Streamflow, River Ice, and Snowpack for Coastal River Basins in Maine During the 20th Century 17

Only the Machias River and the NER show statistically 

significant trends toward decreasing summer runoff 

volumes. The total summer runoff volume for the 

Machias River record decreased by 24 percent between 

Loess regression line end-point values in 1906 and 

1977. The total summer runoff volume for the NER 

decreased 56 percent between 1906 and 2000. 

The Sheepscot River is the only river that shows 

a statistically significant increasing trend in total 

annual runoff volume with a 20-percent increase over 

its period of record. Because this increase is not statistically significant for any single seasonal window, it is 

likely that this increase in annual runoff is distributed 

across multiple seasons. 

Ice 

Trend test results indicate, in general, fall ice-on 

is later, spring ice-off is earlier, and there are fewer 

days of total winter ice effect on the rivers in coastal 

Maine. The trends in later fall ice-on dates are significant at two of the five rivers (highly significant at the 

West Branch Union River), whereas trends for earlier 

spring ice-off are significant at four of five of the rivers. 

The combined effect of these trends yields statistically 

significant trends toward decreasing the total number 

of days of ice effect throughout the winter season at 

four of the five stations examined—highly significant 

trends at the Machias River.

Because the Loess regression line is sensitive to 

values at the beginning and end of the time period 

being plotted, the Narraguagus and Royal Rivers, both 

beginning around 1950, do not seem to follow the same 

trends as the rest of the rivers (fig. 10). Otherwise, all 

other river-ice trends are in agreement suggesting that 

trends in first fall ice-on date (fig. 10) are similar across 

the entire study area. The trend toward later first fall 

ice-on dates is statistically significant at the Machias 

River and highly significant at the West Branch Union 

River (table 12). Each river covers nearly the same time 

period with 48 years (1930-77) and 50 years (1930-79) 

of record, respectively. The average net change in iceon date for the Machias and West Branch Union Rivers 

is 14 days. 

The trend toward earlier last spring ice-off dates 

is statistically significant in all rivers except for the 

West Branch Union River (table 12). There was a 

period of particularly cold and (or) snowy weather 

evident during the 1960’s (fig. 11). The net change in 

last spring ice-off date for the Machias River (1930-77) 

is 18 days. The Narraguagus (1950-00) and Royal 

Rivers (1949-00) are representative of the latter half of 

the 20th century. The average net change in last spring 

ice-off dates for the Narraguagus and Royal Rivers is 

8.5 days. The Sheepscot River has 62 years (1939-

2000) of record with a net change in last ice-off date of 

12 days. 

Table 12. Statistical significance (p-values) and trend direction for total number of days of ice, first ice-on date, and last ice-off 

date for coastal river basins in Maine 

[p-values in bold are significant at less than or equal to 0.10; p-values in bold and underlined are highly significant at less than or equal to 0.01; +, upward 

trend over time; -, downward trend over time]

Streamflow-gaging 

station

Period of 

record

Machias 1929-77 0.0293 + 0.0202 - 0.0012 -

Narraguagus 1948-2000 .8931 - .0529 - .0379 -

West Branch Union 1929-79 .0041 + .3611 - .0295 -

Sheepscot 1938-2000 .1348 + .0534 - .1977 -

Royal 1949-2000 .2761 + .0773 - .0849 -

Total 

number of 

days of ice

First ice-on 

date

Last ice-off 

date
18 Trends in Streamflow, River Ice, and Snowpack for Coastal River Basins in Maine During the 20th Century

1930 1940 1950 1960 1970 1980 1990 2000

YEAR

50

60

70

80

90

West Branch Union

Machias

Narraguagus

Royal

Sheepscot

EXPLANATION

WATER YEAR JULIAN DATE (OCTOBER 1 = WYJD 1)

1930 1940 1950 1960 1970 1980 1990 2000

YEAR

150

160

170

180

190

WATER YEAR JULIAN DATE (OCTOBER 1 = WYJD 1)

W. Branch Union

Machias

Narraguagus

Royal

Sheepscot

EXPLANATION

Figure 10. Trends in first ice-on date for coastal rivers in Maine. Loess regression lines are based on a 35-year 

weighting window. 

Figure 11. Trends in last ice-off date for coastal rivers in Maine. Loess regression lines are based on a 35-year weighting 

window.
Trends in Streamflow, River Ice, and Snowpack for Coastal River Basins in Maine During the 20th Century 19

The total number of days of ice-effect, also was 

affected by the anomalous weather during the 1960’s 

(fig. 12). The trend toward fewer days of ice effect is 

statistically significant at all rivers except for the 

Sheepscot River (table 12). The net change in total days 

of ice-effect for the Machias and West Branch Union 

Rivers, representative of the mid-century (1930-

77,79), is 37 days. The end of the Machias River 

regression line could be affected by the data values at 

the end of the time period being plotted. The net change 

in total days of ice-effect for the Narraguagus and 

Royal Rivers, representative of the latter half of the 

century (1949, 1950-00), is 15 days. 

Snow 

A straightforward histogram analysis of 

maximum values of snowpack water equivalent show 

the winters of 1963, 1966-67, 1969, and 1971 had large 

snowfalls, with 1963 and 1969 being most notable. In 

their analysis of historical snowpack in Maine, Loiselle 

and Hodgkins (2002) also found the winters of 1963 

and 1969 to be heavy snow years. The effect of the 

particularly cold and (or) snowy winters during this 

decade can be seen not only in the snow data but in the 

trend plots of last ice-off date and total days of ice. This 

snowy period confounds the trend-test results for the 

snow data because much of the available snow data is 

sparse and of short duration. Most of the snow-survey 

sites have snow data beginning in the late 1950’s, 

which places the beginning of these data sets in a time 

period of heavy snowfall. Because the trend test is 

sensitive to values at the beginning and end of the 

temporal window being tested, trends in snow depth 

and equivalent water for sites with data beginning in 

the late 1950’s or early 1960’s show highly significant 

decreasing trends, whereas snow sites with longer 

record show no significant trends. 

For the February 15 survey date, only the snowsurvey site at Amherst contained enough data to test for 

trends, and there were no significant trends in snow 

depth, equivalent water, or density. 

1930 1940 1950 1960 1970 1980 1990 2000

YEAR

20

40

60

80

100

120

W. Branch Union

Machias

Narraguagus

Royal

Sheepscot

NUMBER OF DAYS OF ICE EFFECT

EXPLANATION

Figure 12. Trends in total number of days of ice effect for coastal rivers in Maine. Loess regression lines are based on a 35-year 

weighting window.
20 Trends in Streamflow, River Ice, and Snowpack for Coastal River Basins in Maine During the 20th Century

The March 1 survey date contained most of the 

available snow data with eight survey sites available 

for trend analyses. An analysis of water content in 

snowpack in Maine by Hayes (1972) showed that the 

average date of maximum water content of the snowpack along the coast occurs in early March. Only the 

stations with periods of record beginning in the late 

1950’s have statistically significant trends towards 

decreasing snow depth and equivalent water content 

(table 13) indicating that this trend is a product of 

heavy snowfall occurring in the early years of the 

temporal window. 

For the March 1 survey date, two of the three 

stations with periods of record beginning before 1945 

have statistically significant trends in increasing snow 

density (table 13). Amherst and Whitneyville, respectively, had net increases of 12 and 10 percent in snow 

density during their periods of record (fig. 13). Data for 

the Amherst site is shown on the figure because it has 

the longest and most complete snow data set of all the 

survey sites examined for this study. 

The March 15 survey date only had four stations 

with data available for trend testing. The Augusta site 

has statistically significant trends toward decreasing 

snow depth and equivalent water with net decreases of 

33 and 50 percent, respectively, during the period of 

record (table 14). The Baring site has a statistically 

significant trend in decreasing snow density (table 14); 

however, the period of record for the snow density 

trend begins in 1962 so the trend also could be a 

product of the large snowfall occurring in the early 

years of the temporal window analyzed. The effects of 

the anomalous winter weather in the 1960’s are 

conspicuous for the Amherst snow-survey site for this 

survey date (fig. 14). 

The April 1 survey date only had two stations 

with data available for trend testing. Both stations have 

highly significant trends in decreasing snow depth and 

equivalent water (table 15). Although these trends in 

early-spring decreasing snowpack agree with a significant linear trend toward earlier initiation of frost-free 

conditions for New England for the period 1961-90 

(Cooter and LeDuc, 1995), these trends likely are a 

product of the anomalous winter weather occurring in 

the early years of the temporal window being examined, with both snow records beginning in the late 

1950’s (fig. 15). 

SYNTHESIS OF TRENDS IN STREAMFLOW, RIVER ICE, AND SNOWPACK 

Long periods of record are of great value when 

examining historical trends. Effects that are not 

discernable in a short period of record (decades) can 

become clearer as a longer period of time (century or 

more) is examined. For example, a recent USGS investigation of trends in lake ice-off dates in New England 

showed statistically significant (p<0.10) trends 

towards earlier (advancing) lake-ice out dates at 4 of 13 

lakes with 100 years or less of record; statistically 

significant (p<0.10) advancing trends at 10 of 11 lakes 

with 101-150 years of record; and highly significant (in 

this case, p<0.0001) advancing trends in 5 of 5 lakes 

with more than 150 years of record (Hodgkins and 

others, 2002). The same is the case with records examined in this study—trends in daily mean streamflow are 

more evident with the longer record of the NER and are 

not as clear in the shorter, temporally disparate streamflow records of the other sites. 

The trends over time in streamflow statistics, 

timing and magnitude of runoff, ice occurrence, and 

snowpack data corroborate the hydroclimatological 

scenario of a temporal shift towards earlier spring 

snowmelt runoff. The NER shows a significant trend 

toward increasing streamflows in February and trends 

toward decreasing streamflows in May and June across 

all flow-frequencies analyzed. This result is supported 

by the highly significant trend in earlier spring SCVD 

for the NER. Trends in river-ice data also show shorter 

ice-effect periods with earlier ice-off dates in the 

spring. The significant trends observed in the ice-off 

data for these coastal rivers could result, in large part, 

because of trends in spring streamflow. Magnuson and 

others (2000) noted that whereas freeze and breakup 

dates were strongly correlated to air temperature, the 

mechanisms for ice breakup on rivers can be dominated 

by the timing, magnitude, and rate of spring runoff. 

Trends toward increased snowpack density at 

sites with the longest snowpack record for March 1 is 

consistent with earlier snowpack melt. Analyzing a 

data set of historical and reconstructed snow-cover data 

from stations in Canada, the United States, the former 

Soviet Union, and the People’s Republic of China, 

Brown (2000) found a rapidly decreasing trend in 

North American spring snow cover during the 1980’s 

and early 1990’s and a significant long-term (since the 

early 1900’s) decrease in water equivalent of April 

snowpack. Brown (2000) also observed that a signifi-
Synthesis of Trends in Streamflow, River Ice, and Snowpack 21

Table 13. Statistical significance (p-values) and trend direction for snow data for the March 1 survey date for 

coastal river basins in Maine 

[p-values in bold are significant at less than or equal to 0.10; p-values in bold and underlined are highly significant at less than or equal to 

0.01; +, upward trend over time; -, downward trend over time; *, no trend test because of lack of data]

1940 1950 1960 1970 1980 1990 2000

YEAR

0

6

13

19

25

0.22

0.24

0.26

0.28

SNOW PACK DEPTH AND EQUIVALENT WATER, IN INCHES

SNOW DENSITY, IN INCHES OF WATER PER INCHES OF SNOW

Snow depth

Snow density

Equivalent water

Figure 13. Trends in snow depth, equivalent water, and snow density at the Amherst snow-survey site for the March 1 

survey date, coastal Maine. Loess regression lines based on a 35-year weighting window.

Falmouth 0.0318 - 0.0504 - 0.0390 + 1958

Auburn .0559 - .0962 - .5190 + 1954

Topsham .0182 - .0171 - .0567 + 1959

Augusta * * * *

Bucksport .0100 - .0233 - .1584 + 1956

Dedham .0378 - .0587 - .4028 + 1959

Amherst .2427 - .4254 - .0780 + 1938

Franklin .2548 - .2324 - .3523 + 1943

Whitneyville .2906 - .9645 - .0344 + 1941

Cooper Mountain * * * *

Baring * * * *

Snow-survey 

station location Snow depth

Equivalent 

water 

content Snow density

Beginning 

of period 

of record
22 Trends in Streamflow, River Ice, and Snowpack for Coastal River Basins in Maine During the 20th Century

1930 1940 1950 1960 1970 1980 1990 2000

YEAR

0

5

10

15

20

25

0.22

0.24

0.26

0.28

0.30

SNOWPACK DEPTH AND EQUIVALENT WATER, IN INCHES

SNOW DENSITY, IN INCHES OF WATER PER INCHES OF SNOW

Snow depth

Snow density

Equivalent water

Figure 14. Trends in snow depth, equivalent water, and snow density at the Amherst snow-survey site for the March 15 survey 

date, coastal Maine. Loess regression lines based on a 35-year weighting window.

Table 14. Statistical significance (p-values) and trend direction for snow data for the March 15 survey date for coastal river 

basins in Maine

[p-values in bold are significant at less than or equal to 0.10; p-values in bold and underlined are highly significant at less than or equal to 0.01; +, upward 

trend over time; -, downward trend over time; o, no trend over time; *, no trend test because of lack of data]

Falmouth * * * *

Auburn * * * *

Topsham * * * *

Augusta 0.0842 - 0.0340 - 0.3041 - 1945

Bucksport * * * *

Dedham * * * *

Amherst .8683 - .6414 - .8496 - 1930

Franklin * * * *

Whitneyville * * * *

Cooper Mountain .4629 - .3371 - .8202 - 1947

Baring 1.0000 o .4159 - .0643 - 1962

Beginning 

of period 

of record

Snow-survey 

station location Snow density

Equivalent 

water 

Snow depth content
Synthesis of Trends in Streamflow, River Ice, and Snowpack 23

Table 15. Statistical significance (p-values) and trend direction for snow data for the April 1 survey date for coastal 

river basins in Maine

[p-values in bold are significant at less than or equal to 0.10; p-values in bold and underlined are highly significant at less than or equal to 0.01; 

+, upward trend over time; -, downward trend over time; *, no trend test because of lack of data]

Falmouth * * * *

Auburn * * * *

Topsham * * * *

Augusta * * * *

Bucksport * * * *

Dedham 0.0065 - 0.0057 - 0.2968 - 1959

Amherst .0004 - .0003 - .8457 - 1956

Franklin * * * *

Whitneyville * * * *

Cooper Mountain * * * *

Baring * * * *

Beginning 

of period 

of record

Snow-survey 

station location Snow density

Equivalent 

water 

Snow depth content

1960 1970 1980 1990 2000

YEAR

0

5

10

15

20

25

0.28

0.30

0.32

0.34

0.36

SNOWPACK DEPTH AND EQUIVALENT WATER, IN INCHES

SNOW DENSITY, IN INCHES OF WATER PER INCHES OF SNOW

Snow depth

Snow density

Equivalent water

Figure 15. Trends in snow depth, equivalent water, and snow density at the Amherst snow-survey site for the April 1 

survey date, coastal Maine. Loess regression lines based on a 35-year weighting window.
24 Trends in Streamflow, River Ice, and Snowpack for Coastal River Basins in Maine During the 20th Century

cant hemispheric-scale reduction in snow-cover extent 

was associated with warming over the Northern Hemisphere mid-latitude areas, with the largest warming 

during the November-April snow season in March.

The statistically significant decreasing trend in 

the NER summer runoff volume is consistent with findings of an earlier spring snowmelt runoff that would 

contribute less water in the late spring and summer 

months. Zhang and others (2001) generally found 

trends that were not significant for starting dates of the 

spring high-flow season (both earlier and later) from 

1947 to 1996 in areas of Canada to the northwest and 

northeast of Maine. This result could indicate that the 

mechanisms controlling the timing of Canadian 

streamflows did not change in the same way as the 

mechanisms in Maine, that their measure of timing is 

not as sensitive as the spring SCVD, or that the additional years of streamflow data from 1997 to 2000 used 

in this study strengthen the trend test results. 

Throughout Canada, with the exception of the Atlantic 

region, Zhang (2001) observed increases in March and 

April mean monthly streamflows and decreases in 

streamflow for June through September, attributing the 

trends to an earlier snowmelt resulting in less water 

remaining in the basin later in the year. In the Atlantic 

region of Canada, where the trends are more mixed and 

less significant, Zhang attributes the trends to 

increasing total spring precipitation and decreasing 

spring temperatures related to the North Atlantic Oscillation (NAO). 

Directions of trends in the fall peak-flow date 

and fall center-of-volume date with any statistical 

significance are mixed, although two of three significant results indicate a trend to later fall peak streamflows and center-of-volume. Statistically significant 

trends over time in river ice-on data for the late fall and 

early winter are for later ice-on dates, even though this 

trend is significant at fewer sites than the statistically 

significant trends in ice-off data. 

These seasonal trends in streamflow, river ice, 

and snowpack for coastal rivers in Maine could be the 

result of changes over time in air temperature, seasonal 

distribution, amount of precipitation, and (or) land use. 

Increased air temperatures could contribute to earlier 

melting of the snowpack. The winter air temperature 

also could affect the nature of winter precipitation 

causing wetter and denser snowfall. The effect of air 

temperature on ice formation and breakup can be 

substantial; for example, the length of the river-ice 

season in the Atlantic region of Canada has increased 

during the past 45 years with the greatest rates of 

change observed in Cape Breton and Newfoundland, 

Canada in response to colder air temperatures (Prowse 

and Beltaos, 2002). Prowse and Beltaos (2002) point 

out that other than this North Atlantic anomaly and 

certain rivers in central and eastern Siberia, the overall 

trend elsewhere is toward shorter river-ice seasons. 

Although the system of explanatory mechanisms is 

complex, the North Atlantic anomaly appears to be 

linked to winter ocean currents that have become 

colder as a result of the intensity of the NAO (Brimley 

and Freeman, 1997). Magnuson and others (2000) have 

found that later freeze and earlier breakup dates of lake 

and river ice during the past 150 years (1846-1995) 

correspond to an increase in air temperature of approximately 2.2 o

F per century, with freeze and breakup 

dates correlating most strongly with air temperatures 1 

to 2 months preceding the event. 

Although the seasonal distribution of precipitation was not specifically examined in this study, trends 

over time for more rain in the spring and less in summer 

could contribute to the monthly and seasonal trends 

observed in the streamflow record. Although this study 

did not find any significant trends in minimum daily 

streamflow on an annual basis, Lins and Slack (1999) 

report trends toward increasing annual minimum daily 

streamflow at various central and northern Maine 

streamflow-gaging stations possibly associated with 

NAO-affected precipitation patterns. 

Reforestation has been the greatest change in 

land use in Maine during the last century with increases 

in forest area ranging from 18- to 186-percent in 

various areas throughout the State. Reforestation 

contributes to greater evapotranspiration during the 

growing season of summer and early fall. Fall runoff 

volumes can be decreased further by an extended 

length of the growing season caused by warmer 

temperatures. Given the large amount of reforestation 

that has occurred in these coastal basins over the last 

century, however, none of the coastal rivers show 

statistically significant trends toward decreasing total 

annual runoff. The Sheepscot River basin has experienced a large increase in forest area with estimates 

ranging from 100- up to 186-percent, whereas the 

streamflow data show a statistically significant trend 

toward increasing annual runoff volume. These results 

suggest an increase in precipitation and (or) a decrease 

in evapotranspiration.
References Cited 25

Because of the uncertainty regarding the causes 

of these trends in streamflow, river ice, and snowpack 

for coastal rivers in Maine, additional studies could be 

done to investigate the relation of the trends to changes 

in regional air temperature, NAO index, Gulf of Maine 

ocean temperature, and the frequency, distribution, 

magnitude, and ratio of snow to rain for coastal precipitation. 

SUMMARY 

Air temperature and precipitation have increased 

in New England during the past century. Because a 

major component of the hydrology of river basins in 

New England involves snow-pack and the timing of 

snowmelt, the hydrologic response of the region to 

warmer winters may be significant. This report, by the 

U.S. Geological Survey, in cooperation with the Maine 

Atlantic Salmon Commission, presents the data and 

methods used to determine if any statistically detectable changes in streamflow, river ice, and snowpack 

have taken place in coastal river basins in Maine in 

response to observed changes in climate. Specific data 

evaluated include the timing and magnitude of annual, 

monthly, and seasonal streamflows; the occurrence and 

duration of river ice; and changes in snowpack depth, 

equivalent water content, and snow density for coastal 

river basins in Maine. 

Historical trends in streamflow, ice, and snow 

are all consistent with an earlier onset of spring conditions in coastal Maine. There has been a significant 

trend in the timing of spring runoff toward earlier dates 

for extended streamflow record spanning 1906-21 and 

1929-2000. Only one of the coastal rivers (Sheepscot) 

had a significant trend in annual runoff volume. Riverice occurrence at coastal river streamflow-gaging 

stations show, in general, earlier last ice-off dates in the 

spring. Later initial onset of ice also is evident, 

although significant at fewer stations than the number 

for earlier ice-off dates. Later ice-on in the winter and 

earlier ice-off in the spring contribute to a statistically 

significant decrease over time in the total number days 

of ice-effect at most gages on coastal rivers in Maine. 

The longest, most complete snow records indicate an 

increase in snow density for the March 1 snow-survey 

date during the last 60 years; however, trends in snowpack depth, equivalent water content, and snow density 

generally are inconclusive because of missing data and 

short periods of available record. 

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Brimley, W.A., and Freeman, C.N., 1997, Trends in river ice 

cover in Atlantic Canada, in Proceedings of the Ninth 

Workshop on River Ice, September 24-26, 1997: Fredricton, New Brunswick, Canadian Committee on 

River Ice Processes and the Environment, Canadian 

Geophysical Union, p. 335-349. 

Brown, R.D., 2000, Northern Hemisphere snow cover variability and change, 1915-97: Journal of Climate, v. 13, 

p. 2339-2355. 

Cleveland, W.S., Devlin, S.J., 1988, Locally weighted 

regression: an approach to regression analysis by local 

fitting: Journal of the American Statistical Association, 

v. 83, p. 596-610. 

Cooter, E.J., and LeDuc, S.K., 1995, Recent frost date trends 

in the North-Eastern USA: International Journal of Climatology, v. 15, p. 65-75. 

Court, A., 1962, Measures of streamflow timing: Journal of 

Geophysical Research. v. 67, p. 4335-4339. 

Hartley, S., and Dingman, S.L., 1993, Effects of climatic 

variability on winter-spring runoff in New England 

river basins: Physical Geography, v. 14, p. 379-393. 

Hayes, G.S., 1972, Average water content of snowpack in 

Maine: U.S. Geological Survey Hydrologic Investigations Atlas HA-452, scale 1:1,000,000. 

Helsel, D.R., and Hirsch, R.M., 1992, Statistical methods in 

water resources: Amsterdam, Elsevier, 529 p. 

Hodgkins, G.A., James, I.C., and Huntington, T.G., 2002, 

Historical changes in lake ice-out dates as indicators of 

climate change in New England, 1850-2000: International Journal of Climatology, Volume 22, Issue 15, p. 

1819-1827.

Intergovernmental Panel on Climate Change, 2001, Climate 

change 2001, the scientific basis: Cambridge, Cambridge University Press, 881 p.

Irland, L.C., 1998, Maine’s forest area, 1600-1995-Review 

of available estimates-College of Natural Sciences, 

Forestry, and Agriculture, University of Maine, Maine 

Agricultural and Forest Experiment Station Miscellaneous Publication 736, February 1998, 12 p. 

Lins, H.F., and Slack, J.R., 1999, Streamflow trends in the 

United States: Geophysical Research Letters, v. 26, p. 

227-230.

Loiselle, M.C., and Hodgkins, G.A., 2002, Snowpack in 

Maine-Maximum observed and March 1 mean equivalent water content: U.S. Geological Survey WaterResources Investigations Report 01-4258, 19 p. 

Magnuson, J.J., Robertson, D.M., Benson, B.J., Wynne, 

R.H., Livingstone, D.M., Arai, T., Assel, R.A., Barry, 

R.G., Card, V., Kuusisto, E., Granin, N.G., Prowse, 

T.D., Stewart, K.M., and Vuglinski, V.S., 2000, Trends 

in lake and river ice cover in the Northern Hemisphere: 

Science, v. 289, p. 1743-1746. 
26 Trends in Streamflow, River Ice, and Snowpack for Coastal River Basins in Maine During the 20th Century

Prowse, T.D., and Beltaos, S., 2002, Climatic control of 

river-ice hydrology-A review: Hydrologic Processes, v. 

16 p. 805-822. 

Randall, A.D., 2000, Hydrogeologic framework of stratified-drift aquifers in the glaciated northeastern United 

States: U.S. Geological Survey Professional Paper 

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network (HCDN)-A U.S. Geological Survey streamflow data set for the United States for the study of climate variations, 1874-1988: U.S. Geological Survey 

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Thompson, W.B., and Borns, H.W., 1985, Surficial geologic 

map of Maine: Maine Geological Survey, Department 

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Atmospheric Administration, 2000, Climatological 

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District Chief

Maine District

U.S. Geological Survey

Water Resources Division

196 Whitten Road

Augusta, ME 04330

__________________________________________________________________________________

Dudley, R.W., Hodgkins, G.A., Trends in Streamflow, River Ice, and Snowpack for Coastal River Basins in Maine During the 20th Century—

WRIR 02-4245

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