The Sleepers River Research Watershed in northeastern Vermont was established by the Agricultural Research Service (ARS) of the U.S. Department of Agriculture in 1959 and is now operated jointly by the U.S. 

Geological Survey (USGS) and the U.S. Army Cold Regions Research and 

Engineering Laboratory (CRREL), with collaboration from several other 

Federal Agencies and Universities. The USGS has contributed to the understanding of hydrological processes and added a major biogeochemical 

cycling research component in the last 10 years of Sleepers River’s 40-year 

history as a field laboratory. The USGS uses hydrologic measurements and 

chemical and isotopic tracing techniques to determine how water moves 

from the hillslope to the stream, and what processes cause chemical 

changes, such as the neutralization of acid rain. Research results provide 

insights on how pollutants move through ecosystems, and how ecosystems may respond to climatic change.

The glaciers that covered New 

England until 10,000 years ago 

were a dominant force that 

shaped the present-day landscape and 

influenced its hydrologic and chemical 

characteristics. Most of the Sleepers 

Sleepers River, Vermont

U.S. Department of the Interior 

U.S. Geological Survey

Fact Sheet-166-99

June 2000

A Water, Energy, and Biogeochemical Budgets Program Site

River watershed is covered by 1–4 

meters of glacial till, a compacted fine 

silty material that formed underneath the 

glacial ice as it moved overland. The 

till was formed primarily from the local 

bedrock, which is a calcareous granulite/

quartz-mica phyllite. About 60 to 80 

centimeters of soil has developed in the 

till. Weathering of calcite in the till and 

bedrock causes highly buffered streamflow (compared to most streams in New 

England) and a nutrient-rich biological 

environment, which makes Sleepers 

River an end member in regional biogeochemical cycling studies (Hornbeck and 

others, 1997).

Like much of northern New England 

during the last century, the Sleepers 

River area has reverted from a predominately cleared, agricultural landscape to 

a mostly forested one. A Northern Hardwood forest, dominated by sugar maple, 

white ash, yellow birch, and beech, with 

lesser amounts of red spruce and balsam 

fir, now covers two-thirds of the area; 

the remaining open land is primarily pasture and hayfields. Dairy farming and 

logging are the primary human enterprises in the watershed.

Sleepers River has a humid continental 

climate. The average annual temperature 

is 6 degrees Celsius and average annual 

precipitation is 1,100 millimeters, 20–30 

percent of which falls as snow. The 

abundant snowfall at Sleepers River has 

driven much of the research activity. The 

National Weather Service established a 

snowmelt research station in 1968, and 

the modeling routines they developed 

are still used in their flood forecasting. 

Freeze/thaw cycles and winter rain and 

ice storms tend to produce highly layered snowpacks in the eastern United 

Streamgage placement in the Sleepers 

River Research Watershed was designed 

for nested- and paired-catchment studies.

Permeable brown soil rich in fine roots 

overlies the dense olive-gray glacial till. 

The tubing and collection vessels are part 

of devices that collect water from the 

unsaturated zone of the soil.

0 2 km

0 2 mi

W-9

(forest)

W-2

(pasture)

W-3

W-5

Stream-gaging station

Meteorological station

N. Danville

Snowmelt

research

station

VERMONT

Sle epers River

N

Passu mpsic R.

Montpelier

Study area

The Water, Energy, and Biogeochemical Budgets (WEBB) Program was started 

in 1991 at five small watersheds in the United States to examine water, energy, 

and biogeochemical fluxes and to determine the effects of atmospheric 

deposition, climatic variables, and human influences on watershed processes. 

The five sites are at Loch Vale, Colorado; Luquillo Experimental Forest, Puerto 

Rico; Panola Mountain, Georgia; Sleepers River, Vermont; and Trout Lake, 

Wisconsin. These sites are supported, in part, by other programs in the 

USGS, other Federal and State Agencies, and Universities.

THE WEBB PROGRAM
as streamflow and 45 percent returns 

to the atmosphere by evapotranspiration, 

or water evaporated from watershed surfaces and water transpired by trees. 

Water availability is rarely a problem in 

forests of the humid, temperate northeastern United 

States, so the 

amount of evapotranspiration is 

fairly constant 

from year to year. 

As a general rule, 

the total streamflow each year is simply the amount 

of precipitation minus the amount of 

evapotranspiration.

Snow plays a key role in the hydrology 

at Sleepers River. Precipitation is stored 

in the snowpack during the winter 

months and is released in a short 

time during the spring. Spring snowmelt 

causes most of the annual ground-water 

recharge, and nearly half of the annual 

streamflow in March and April.

Water Flowpaths

Knowledge of how rain or snowmelt 

moves to a stream is fundamental to 

understanding many environmental contamination problems. In the late 1960s, 

Tom Dunne of the ARS dug a trench at 

the base of a hillslope at Sleepers River 

and determined that most of the runoff 

from the hillslope occurred as surface 

flow where the soils at the land surface 

were saturated (Dunne and Black, 1970). 

The term “Dunnean flow” is sometimes 

used to describe this runoff process, 

which is widely accepted as the dominant streamflow generation mechanism 

in humid, temperate environments. Fundamental questions remain, however, 

about how the saturated areas develop, 

and how much of the surface runoff is 

from direct rainwater/snowmelt on saturated areas compared to the discharge 

of shallow groundwater from upslope 

(return flow) onto saturated areas.

Since the time of Dunne’s experiments, 

hydrologists have made considerable use 

of the 18O/16O isotope ratio, which is 

an ideal tracer because it is a fundamental property of the water molecule. 

Precipitation that forms at cold temperatures tends to have a low 18O/16O; when 

the snow melts in spring, the 18O/16O of 

the meltwater contrasts with the higher 

18O/16O of ground water, which reflects 

the annual average isotopic ratio of precipitation. As flow rises from melting 

snow, the 18O/16O of streamflow, which 

is close to that of ground water during 

low flow in winter, deflects only slightly 

toward the 18O/16O of snow meltwater. 

This subdued response indicates that the 

snowmelt triggering the flow increase 

comprises only a small fraction of 

streamflow; most of the streamflow 

is composed of pre-existing ground 

water or “old” water already present in 

States. USGS and CRREL research shows 

that ice layers within the snowpack retard 

the downward movement of meltwater 

and solutes (Shanley and others, 1995). 

Sleepers River has one of the longest 

historical hydrologic and climatologic 

data bases for a 

cold-region area in 

the United States, 

featuring measurements of precipitation and streamflow 

since 1959, snow 

depth and corresponding water content since 1960, soil 

frost depth since 1984 (Shanley and 

Chalmers, 1999), and ground-water levels 

since 1991. These and other measurements 

constitute a valuable resource for hydrologic modeling and for the evaluation of 

climatic changes.

Water Budget

In an average year, 55 percent of the 

total water input in precipitation runs off 

At the agricultural catchment W-2, frozen 

ground during the 1993 snowmelt season 

led to direct runoff of snowmelt water to 

the stream; the 18O/16O of streamflow (circles) decreased from the value of ground 

water to nearly the level of snowmelt. 

In the more typical 1994 snowmelt, the 

18O/16O of streamflow remained much 

closer to that of ground water, indicating 

that ground water contributions dominated 

the stream snowmelt response.

This streamflow-gaging station (W-2) 

records streamflow 

from a 59-hectare 

agricultural catchment. The USGS 

operates 4 of the 

original 17 Sleepers 

River streamgages, 

as well as 5 new 

gages on small 

streams within the 

forested headwater 

catchment W-9. 

Much of the streamflow at Sleepers River 

is generated by rain falling or snow melting directly onto saturated areas adjacent 

to streams.

From oxygen isotope ratios we know 

that under most conditions, streamflow is composed primarily of ground 

water that was present in the catchment before the runoff event, not the 

rain or snowmelt causing the event.

1993

1994

March

21

March

31

April

10

April

20

April

30

Discharge (millimeters per hour)

δ18O (18O/16O ratios relative to a standard, in permil)

of streamflow, snowmelt, and groundwater

0.0

2.0

1.5

1.0

0.5

-19

-11

-13

-15

-17 Discharge

Snowmelt

Streamflow

Groundwater

-19

-11

-13

-15

-17

0.0

2.0

1.5

1.0

0.5
the catchment before snowmelt began 

(McGlynn and others, 1999). Isotopic 

data revealed a striking exception to this 

pattern during one snowmelt season at 

the agricultural catchment W-2, when 

frozen soils caused snowmelt to run off 

directly into the stream channel.

In the forested catchment W-9, nested 

wells and piezometers were used to distinguish zones of ground-water recharge 

and discharge and to discern the nature 

of ground-water/surface-water interactions. Hillslopes are recharge areas where 

ground water rises into the soil nearly to 

land surface during snowmelt. The 

surficial soil transmits water more 

readily than the 

underlying till, 

such that water 

moves easily 

downslope and 

generates increased 

streamflow. 

Ground-water discharge occurs only in 

riparian areas and in upland convergent 

flow areas. The relation between groundwater level and streamflow revealed a 

hysteresis relation; for a given streamflow, ground-water level at riparian sites 

was higher on the rising limb of the 

snowmelt hydrograph than for the same 

streamflow on the falling limb. The pattern was reversed at hillslope sites (Kendall and others, 1999). 

Hydrologic Modeling and 

Energy Budgets

A topographically based model TOPMODEL was used as a supplementary 

approach to understanding water movement and storage in the headwater 

catchment. TOPMODEL simulates soilsaturation deficit and generates overland 

flow when the deficit is zero. The model 

is built on the concept that the amount 

of water draining toward a point on 

the landscape is 

controlled by the 

upslope contributing area, and 

the amount of 

water draining 

away from that 

point is controlled 

by the local slope. 

The minimum requirements to run 

TOPMODEL are topographic and precipitation data; soil hydraulic properties 

can be incorporated if available. Wolock 

(1995) applied TOPMODEL to the 

nested catchments at Sleepers River and 

determined that the percentage of overland flow in total streamflow increased 

as catchment size increased up to 5 

square kilometers, after which the percentage remained fairly constant. 

The energy aspects of the WEBB studies 

have been investigated primarily by 

CRREL. CRREL maintains three energy 

stations for the collection of meteorological and energy data, including 

temperature, humidity, wind speed, and 

incoming and outgoing short- and longwave radiation. This information is used 

to compute an energy balance, which then 

is used in a model that simulates how 

fast the snow melts. Recently CRREL has 

focused on measurements in the forested 

environment to quantify how the forest 

litter in the snow changes the snowpack 

albedo an important term in the energy 

balance. The USGS collaborates with 

CRREL on using the output of the 

snowmelt model as the input to drive 

TOPMODEL.

Biogeochemical Budgets 

Although the Sleepers River watershed 

receives significant acidic precipitation, 

streamflow is well-buffered from the 

weathering of calcite in the bedrock 

and glacial till. Calcium (Ca), magnesium (Mg), sodium (Na), and bicarbonate (HCO3) are products of mineral 

In riparian areas, ground-water levels 

rise rapidly as streamflow increases in 

response to snowmelt, then fall rapidly 

after peak flow. On hillslopes, by contrast, 

ground water rises slowly at first but 

maintains high levels during the snowmelt 

recession (note opposite direction of time 

arrows). This pattern suggests that riparian 

ground water supplies most streamflow 

during the early part of snowmelt and hillslope ground water supplies most streamflow during the later part of snowmelt. 

Negative depths indicate the water table is 

above land surface. 

Streamflow chemistry provides clues 

about hydrology. High concentrations of calcium and magnesium 

indicate a deep ground-water flow 

path, whereas high concentrations of 

nitrate and dissolved organic carbon 

indicate shallow subsurface flow.

During snowmelt, the large volume of 

water moving through the upper organic 

soil zone flushes nitrate and dissolved 

organic carbon (DOC) to the stream. Nitrate 

concentrations reach a maximum early 

in the snowmelt period, whereas DOC 

concentrations continue to peak with individual streamflow peaks throughout the 

melt period.

0.0 0.5 1.0 1.5 2.0

Streamflow (millimeters per hour)

0.0 0.5 1.0 1.5 2.0

Depth to water table

(millimeters below land surface)

0

400

800

1200

-100

-150

-50

0

50

Riparian site Hillslope site

Rising Limb

Falling Limb

40

30

20

10

0

400

300

200

100

0

25 30 4 9 14 19 24 29

March

DOC concentration

(micromoles per liter)

Nitrate

(microequivalents per liter)

2.0

1.5

1.0

0.5

0

Streamflo

w

(millimeters per hour)

Nitrate

Runoff

DOC

April
For more information about the Sleepers River 

Research Watershed WEBB study visit:

http://nh.water.usgs.gov/CurrentProjects/sleepers/

For more information or for reprints, please contact:

Project Chief, WEBB Program

U.S. Geological Survey

P.O. Box 628

Montpelier, VT 05601

802-828-4466 or jshanley@usgs.gov.

REFERENCES

Bullen, T.D., and Kendall, C., 1999, Tracing of weathering reactions and water flowpaths: a multi-isotope 

approach, in Kendall, C., and McDonnell, J.J., editors, 

Isotopes in Catchment Hydrology, Elsevier, Amsterdam, Chapter 18, p. 611-646.

Dunne, T., and Black, R.D., 1970, Partial area contributions to storm runoff in a small New England watershed: Water Resources Research, v. 6, p. 1296-1311.

Hornbeck, J.W., Bailey, S.W., Buso, D.C., and Shanley, J.B., 1997, Streamwater chemistry and nutrient 

budgets for forested watersheds in New England: variability and management implications: Forest Ecology 

and Management, v.93, p. 73-89.

Kendall, C., Silva, S.R., Chang, C.C., Campbell, D.H., 

Burns, D.A., and Shanley, J.B., 1995, Use of oxygen 

and nitrogen isotopes to trace sources of nitrate 

during snowmelt in forested catchments: in Tonnessen, K.A., Williams, M.W., and Tranter, M., editors, 

Biogeochemistry of Seasonally Snow-Covered Catchments, International Association of Hydrologic Sciences, Publication no. 228, p. 339-347.

Kendall, K.A., Shanley, J.B., and McDonnell, J.J., 

1999, A hydrometric and geochemical approach to 

testing the transmissivity feedback hypothesis during 

snowmelt: Journal of Hydrology, v. 219, p. 188-205.

McGlynn, B.L., McDonnell, J.J., Shanley, J.B., and 

Kendall, C., 1999, Riparian zone flowpath dynamics in 

a small headwater catchment: Journal of Hydrology, v. 

222, p. 75-92.

Shanley, J.B., and Chalmers, A., 1999, The effect of 

frozen soil on snowmelt runoff at Sleepers River, Vermont: Hydrological Processes, v. 13, p. 1843-1857.

Shanley, J.B., Kendall, C., Albert, M.R., and Hardy, 

J.P., 1995, Chemical and isotopic evolution of a layered eastern U.S. snowpack and its relation to streamwater composition: in Tonnessen, K.A., Williams, 

M.W., and Tranter, M., editors, Biogeochemistry of 

Seasonally Snow-Covered Catchments, International 

Association of Hydrologic Sciences, Publication no. 

228, p. 329-338.

Wolock, D.M., 1995, Effects of subbasin size on topographic characteristics and simulated flow paths in 

Sleepers River watershed, Vermont: Water Resources 

Research, v. 31, p. 1989-1997.

—James B. Shanley

COLLABORATORS

The WEBB research program at Sleepers River 

watershed relies on collaborations among the USGS, 

CRREL, U.S. Forest Service, Natural Resources Conservation Service, Vermont Department of Forests, 

Parks, and Recreation, and academia. Students from 

the State University of New York—College of Environmental Science and Forestry, the University of 

New Hampshire, and Dartmouth College have all 

contributed to the WEBB program at Sleepers River 

through thesis research projects. 

weathering in the soil and till. By contrast, nitrate (NO3) and dissolved organic 

carbon (DOC) in streamflow are derived 

primarily from organic matter in shallow 

soil horizons. At high 

flow, concentrations of 

Ca, Mg, Na, and HCO3

are diluted, whereas 

concentrations of DOC 

and NO3 increase. These opposite trends 

suggest that as flow increases, greater 

amounts of water enter the stream 

through shallow flowpaths in the soil. 

This is an example of how chemical 

patterns reveal clues about catchment 

hydrology.

Isotopic tracers of solutes

Whereas oxygen isotopes reveal how 

much streamflow is derived from ground 

water and how much is derived from 

melting snow, isotopes of strontium and 

lead reveal the source of solutes in 

streamflow (Bullen and Kendall, 1999). 

For example, the weathering of calcite 

yields a lower 87Sr/86Sr ratio than the 

weathering of most silicate minerals. The

87Sr/86Sr ratio of streamflow decreases

as basin size increases, suggesting that 

the primary source of solutes shifts from 

the calcite-depleted soil zone in headwater 

catchments to deeper 

soil and bedrock sources 

downstream. The ratio 

206Pb/204Pb is greater 

in ground water (Pb 

derived from weathering of till and bedrock) than in shallow soil water (Pb 

derived from the atmosphere). At Sleepers River, Pb isotopes indicate that significant atmospheric Pb is delivered to 

streamflow by shallow soil water discharge only during the initial phase of a 

runoff event; the majority of Pb is derived 

from the weathering of till and bedrock 

minerals and is delivered to streamflow by 

ground water.

Nitrogen and carbon

Atmospheric deposition of nitrate is a 

regional concern because of its acidifying 

effects on streamflow and forest soils. 

The fate of nitrate in the forest ecosystem 

is being investigated by analysis of both

CO2 production and flux out 

of the soil continue through 

the cold winter months.

the N and O isotopes of the nitrate ion.

The isotopic composition of nitrate in 

streamflow matches that of nitrate produced by mineralization and nitrification 

in the soil, indicating that streamflow 

nitrate is derived from the soil and not 

from the rain or snowmelt that causes 

the high flow (Kendall and others, 1995). 

This finding suggests that most incoming 

atmospheric nitrogen is incorporated at 

least temporarily in the soil where it is 

utilized by the biota. 

The role of carbon in global warming has 

generated great interest in the carbon cycle 

within the scientific community. Recent 

research indicates that North America may 

be a major sink for atmospheric carbon. 

The amounts of carbon stored in the soil 

and vegetation at the Sleepers River watershed are being quantified, and CO2 fluxes 

from the soil have been measured. One 

objective of the CO2 research is to determine the effect of the snowpack on soil 

CO2 fluxes. Research results indicate that 

CO2 production and flux out of the soil 

continue throughout the winter despite the 

presence of the overlying snowpack. 

RESEARCH FINDINGS

• Precipitation is acidic, but streamflow is well-buffered from the 

weathering of calcite in till and bedrock. 

• Infiltrating snowmelt causes ground water to rise into the permeable 

soil zone, where it moves rapidly downslope.

• Naturally occurring isotopic and chemical tracers indicate that “old” 

water dominates streamflow, and that water acquires solutes from weathering and biogeochemical processes along deep and shallow flowpaths.

• Nitrate in streamflow is supplied primarily by mineralization and 

nitrification in the soil, rather than directly by precipitation.