U.S. Department of the Interior

U.S. Geological Survey

Fact Sheet 2009–3044

June 2009

Framework for a U.S. Geological Survey 

Hydrologic Climate-Response Program in Maine

The seasonal water cycle in Maine has been shown to be sensitive to changes in air temperature 

during the last century. A hydrologic climate-response program would improve understanding of the 

future effects of climate change in the State.

Introduction

It is important to monitor hydrologic 

systems in the United States that could 

change dramatically over the short term 

as a result of climate change. Many 

ecological effects of climate change 

can be understood only if hydrologic 

data networks are in place. Because of 

its humid, temperate climate and its 

substantial annual snowpack, Maine’s 

seasonal water cycle is sensitive to air 

temperature changes (Hodgkins and 

others, 2003). Monitoring of relevant 

hydrologic data would provide important 

baseline information against which future 

climate change can be measured.

A series of recent investigations 

by the U.S. Geological Survey (USGS)

has documented changes in several 

components of the water cycle, including 

earlier snowmelt runoff in Maine during 

the last 30 to 40 years (Hodgkins and 

others, 2003), earlier lake- and riverice breakups (Hodgkins and others, 

2002; Hodgkins and others, 2005), 

and a denser and thinner late-winter 

snowpack (Hodgkins and Dudley, 2006). 

Snowmelt runoff timing was measured 

as the date, each year, by which half 

of the total winter-spring streamflow 

passed a streamflow-gaging station. 

Historical snowmelt runoff timing for 

the Piscataquis River in central Maine is 

shown in figure 1 as an example.

Results of climate projections 

input to hydrologic models indicate 

that hydrologic trends, such as earlier 

spring snowmelt runoff, are expected 

to continue into the future (Hayhoe and 

others, 2007). These trends could affect 

species at the southern edge of their 

range in Maine, such as Atlantic salmon 

and Canada lynx, and may also affect 

availability of water for human use. This 

fact sheet describes the framework of a 

hydrologic climate-response program 

that would improve understanding of the 

effects of future climate change in Maine.

Program Design

The framework of a USGS 

hydrologic climate-response program 

in Maine would consist of four 

major parts (Hodgkins and others, 

2009): (1) identifying homogeneous 

climate-response regions; (2) identifying 

hydrologic components and key variables 

of those components that would be 

included in a hydrologic climateresponse data network (for example, 

streamflow has been identified as a 

primary component, with a key variable 

of streamflow being the timing of 

snowmelt runoff); (3) regularly updating 

historical trends of hydrologic-network 

variables; and (4) selecting basins for 

process-based studies. 

Maine would be divided into seven 

climate-response regions that follow 

major river-basin boundaries and have 

relatively homogeneous climates. A 

map of the climate-response regions and 

May

10

Apr

30

Apr

20

Apr

10

Mar

31

Mar

21

Mar

11

DATE

1900 1920 1940 1960 1980 2000

YEAR

Figure 1. Annual snowmelt runoff timing for the Piscataquis River in 

central Maine, 1903-2000.
streamflow-gaging stations with longterm data that would be appropriate for 

inclusion in a climate-response data 

network are shown in figure 2. 

Components to be included in the 

hydrologic climate-response network 

would have at least one key variable 

for which extensive historical data 

are available at multiple sites. The 

components proposed for inclusion are 

streamflow, lake ice, river ice, snowpack, 

and groundwater. The proposed key 

variables of the hydrologic climateresponse network are expected to be 

responsive to climate change in the next 

few decades. These variables are also 

important for human water use and (or) 

ecosystem function. 

Key hydrologic variables within 

each climate-response region would 

be analyzed periodically to maintain 

up-to-date analyses of year-to-year 

variability, decadal variability, and longer 

term trends. One basin in each climateresponse region would be identified for 

process-based hydrologic and ecological 

studies. The hydrologic climate-response 

program for Maine would provide early 

warning of changes in the seasonal 

water cycle of Maine and increase 

understanding of the effects of changes 

on humans and ecosystems.

References Cited

Hayhoe, K., Wake, C.P., Huntington, 

T.G., Luo, L., Schwartz, M.D., Sheffield, J., Wood, E., Anderson, B., 

Bradbury, J., DeGaetano, A., Troy, T.J., 

and Wolfe, D., 2007, Past and future 

changes in climate and hydrological 

indicators in the US Northeast: Climate 

Dynamics, v. 28, p. 381-407.

Hodgkins, G.A., and Dudley, R.W., 2006, 

Changes in late-winter snowpack 

depth, water equivalent, and density 

in Maine, 1926-2004: Hydrological 

Processes, v. 20, p. 741-751.

Hodgkins, G.A., Dudley, R.W., and 

Huntington, T.G., 2003, Changes in 

the timing of high river flows in New 

England over the 20th century: Journal 

of Hydrology, v. 278, p. 242-250.

MAINE

NEW HAMPSHIRE

Hydrologic climate-response region

Southern coastal, Saco, Presumpscot, mid-coastal

Eastern coastal (Downeast)

Lower Androscoggin, lower Kennebec

Lower Penobscot, St. Croix

Upper Androscoggin, upper Kennebec, upper Penobscot

Upper St. John, Allagash

Lower St. John, Fish, Aroostook, Meduxnekeag

70°

44°

68°

46°

68°

70°

46°

44° #

#

#

#

#

#

#

#

#

#

#

#

#

01022500

01030500

01013500

01014000

01010500

01031500

01038000

01010000

01047000

01060000

01057000

01055000

01052500

01064500

EXPLANATION

# Streamflow-gaging station and number

County boundary

01031500

#

State boundary

Hodgkins, G.A., Dudley, R.W., and 

Huntington, T.G., 2005, Changes in 

the number and timing of days of 

ice-affected flow on northern New 

England rivers, 1930-2000: Climatic 

Change, v. 71, p. 319-340.

Hodgkins, G.A., James, I.C. II, 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, v. 22, p. 1819-1827.

Hodgkins, G.A., Lent, R.M., Dudley, 

R.W., and Schalk, C.W., 2009, Framework for a U.S. Geological Survey 

hydrologic climate-response program 

for Maine: U.S. Geological Survey 

Open-File Report 2009-1115, 29 p.

By Glenn A. Hodgkins, Robert M. Lent, 

Robert W. Dudley, and Charles W. Schalk

For more information, please contact:

Robert Lent, Director

USGS Maine Water Science Center

196 Whitten Road

Augusta, Maine 04330

Telephone: (207) 622-8201

E-mail: rmlent@usgs.gov

Web site: http://me.water.usgs.gov

Figure 2. Location of climate-response regions and streamflow-gaging 

stations with long-term data that would be appropriate for inclusion in a 

hydrologic climate-response program in Maine.