Effects of Selective Forest Clearing, 

Fertilization, and Liming on the Hydrology 

and Water Quality of a Small Tributary to 

the Quabbin Reservoir, Central 

Massachusetts

U.S. Geological Survey

Water-Resources Investigations Report 95-4124

Prepared in cooperation with the 

COMMONWEALTH OF MASSACHUSETTS 

METROPOLITAN DISTRICT COMMISSION
Effects of Selective Forest Clearing, 

Fertilization, and Liming on the Hydrology 

and Water Quality of a Small Tributary to 

the Quabbin Reservoir, Central 

Massachusetts

By JAMES B. SHANLEY, JEFFREY L. STRAUSE, and

JOHN C. RISLEY ____ ________________

U.S. Geological Survey

Water-Resources Investigations Report 95-4124

Prepared in cooperation with the 

COMMONWEALTH OF MASSACHUSETTS 

METROPOLITAN DISTRICT COMMISSION

Marlborough, Massachusetts 

1995
U.S. DEPARTMENT OF THE INTERIOR 

BRUCE BABBIT, Secretary

U.S. GEOLOGICAL SURVEY 

Gordon P. Eaton, Director

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

Chief, Massachusetts-Rhode Island District U.S. Geological Survey

U.S. Geological Survey Earth Science Information Center

Water Resources Division Open-File Reports Section

28 Lord Road, Suite 280 Box 25286, MS 517

Marlborough, MA 01752 Denver Federal Center

	Denver, CO 80225
CONTENTS

Abstract ...................................................................................................................................^ 1

Introduction............................................................................................_^ 1

Purpose and Scope.................................................................................................................................................. 3

Previous Studies...................................................................._ 3

Experimental Design.............................................................................................................................................. 4

Description of Study Area...................................................................................................................................... 5

Acknowledgments.................................................................................................................................................. 5

Methods of Study ...................................................................................................................................................^ 8

Hydrologic Data Collection.................................................................................................................................... 8

Water-Quality Data Collection ............................................................................................................................... 9

Hydrologic Data Analysis....................................................................................................................................... 9

Calculations of Flow................................................................................................................................... 9

Construction of Flow-Duration Curves....................................................................................................... 10

Calculations of Evapotranspiration............................................................................................................. 10

Water-Quality Data Analysis.................................................................................................................................. 10

Solute-Concentrations Models.................................................................................................................... 11

Calculation of Solute Loads........................................................................................................................ 11

Pre-Treatment Hydrologic Characteristics of Experimental and Control Basins .............................................................. 11

Precipitation.............................................................................................................................................^ 11

Surface- Water Flow................................................................................................................................................ 12

Ground-Water Levels.............................................................................................................................................. 14

Pre-Treatment Water-Quality Characteristics of Experimental and Control Basins.......................................................... 15

Precipitation............................................................. 15

Surface Water.......................................................................................................................................................... 21

Groimd Water................................................................................................^^ 22

Effects of Selective Forest Clearing on Hydrology............................................................................................................ 24

Changes in Surface-Water Flow............................................................................................................................. 24

Changes in Ground-Water Levels........................................................................................................................... 29

Changes in Evapotranspiration............................................................................................................................... 29

Effects of Selective Forest Clearing, Fertilization, and Liming on Water Quality............................................................ 31

Changes in Solute Fluxes........................................................................................................................................ 31

Changes in Sediment Transport.............................................................................................................................. 51

Changes in Biogeochemical Controls on Water Quality........................................................................................ 51

Changes in Acid-Neutralization Processes............................................................................................................. 54

Summary and Conclusions................................................................................................................................................. 55

References Cited................................................................................................................................................................ 55

FIGURES

1 -3. Maps showing:

1. Location of the study areas and data-collection sites near Quabbin Reservoir, central

Massachusetts...................................................................................................................................... 2

2. Geology of the control and experimental basins near Quabbin Reservoir, central

Massachusetts...................................................................................................................................... 6

3. Areas of forest clearing, fertilization, and liming in the experimental basin near Quabbin

Reservoir, central Massachusetts......................................................................................................... 7

Contents
4-7. Graphs showing:

4. Precipitation in the control and experimental basins, Dickey Brook Basin near Quabbin

Reservoir, central Massachusetts, water years 1985-89...................................................................... 12

5. Streamflow and base flow in the experimental and control basins near Quabbin Reservoir, 

central Massachusetts, during the pre-treatment period, February 1985 through 

October 1986....................................................................................................................................... 13

6. Flow-duration curves for the experimental and control basins, near Quabbin Reservoir, 

central Massachusetts, during the pre-treatment period, February 1985 through 

October 1986....................................................................................................................................... 14

7. Ground-water levels in two wells in the experimental and control basins, near Quabbin

Reservoir, central Massachusetts, during the pre-treatment period, February 1985 through

October 1986....................................................................................................................................... 15

8. Boxplots of pH, alkalinity, and solute concentrations at New Salem, the control basin, and the 

experimental basin, near Quabbin Reservoir, central Massachusetts during the pre-treatment 

period, February 1985 through October 1986................................................................................................. 16

9. Diagram showing percentage of chemical constituents in streamwater from the control and 

experimental basins, Dickey Brook Basin, central Massachusetts, during the pre-treatment 

period, February 1985 through October 1986................................................................................................. 22

10. Triliner diagram showing percentage of chemical constituents in ground water from the control and 

experimental basins, Dickey Brook Basin, central Massachusetts, during the pre-treatment 

period, February 1985 through October 1986................................................................................................. 23

11,12. Graphs showing

11. Timing of treatments and annual precipitation and annual runoff at the control and 

experimental basins, Dickey Brook Basin, central Massachusetts, water years 1985 

trm>ugh 1989...................................................^^ 24

12. Timing of treatments and monthly runoff from control and experimental basins, Dickey Brook

Basin, central Massachusetts, February 1985 through September 1989............................................. 25

13. Flow-duration curves for the control and experimental basins, Dickey Brook Basin, central

Massachusetts, during the post-treatment period, November 1986 through September 1989........................ 26

14. Scatterplots and regression models of daily mean Streamflow data from the pre- and post-treatment

periods at the control and experimental basins, Dickey Brook Basin, central Massachusetts........................ 27

15. Flow-duration curves for the experimental basin, Dickey Brook Basin, central Massachusetts, 

during the post-treatment period, computed from measured and simulated daily mean 

Streamflow....................................................................................................................................................... 28

16-21. Graph showing:

16. Ground-water levels in wells in the control and experimental basins, Dickey Brook

Basin, central Massachusetts, February 1985 through September 1989............................................. 30

17. Estimated monthly potential evapotranspiration for the study area, Dickey Brook Basin,

central Massachusetts.......................................................................................................................... 31

18. Solute concentrations in stream water at the control- and experimental-basin outlets, Dickey

Brook Basin, central Massachusetts, February 1985 through September 1989.................................. 32

19. Annual input and output fluxes at the control and experimental basin outlets, Dickey Brook

Basin, central Massachusetts, water years 1985 through 1989........................................................... 41

20. Timing of treatments in experimental basin and monthly solute fluxes in streamwater at the 

control- and experimental-basin outlets, Dickey Brook Basin, central Massachusetts, 

February 1985 through September 1989............................................................................................. 44

21. Timing of treatments and concentrations of suspended sediment at the control-basin outlet, 

experimental-basin headwaters gage, and experimental-basin outlet, Dickey Brook Basin, 

central Massachusetts, February 1985 through September 1989........................................................ 52

IV Contents
TABLES

1. Summary of forest clearing, fertilization, and liming treatments in the experimental basin, Dickey

Brook Basin, central Massachusetts................................................................................................................ 8

2. Chemical constituents analyzed for the study, near Quabbin Reservoir, central Massachusetts.......................... 9

3. Results of pre- and post-treatment regression analysis and analysis of covariance on daily flows

at the control and experimental basins near Quabbin Reservoir, central Massachusetts ................................ 27

4. Estimated annual decrease in evapotranspiration as a result of selective forest clearing in the

experimental basin, Dickey Brook Basin, central Massachusetts................................................................... 31

5. Fertilizer and lime inputs to experimental basin, normalized to basin area, Dickey Brook Basin,

central Massachusetts...................................................................................................................................... 37

6. Parameters and coefficients of models used to estimate solute fluxes near Quabbin Reservoir,

central Massachusetts...................................................................................................................................... 38

7. Ratios of runoff-normalized annual solute fluxes in the experimental basin to runoff-normalized

annual solute fluxes in the control basin, Dickey Brook Basin, central Massachusetts.................................. 49

CONVERSION FACTORS, VERTICAL DATUM, AND ABBREVIATED WATER-QUALITY UNITS

Multiply

centimeter (cm)

cubic meter per second (m /s)

hectare (ha)

kilogram (kg)

kilometer (km)

liter per second (L/s)

metric ton (t)

meter (m)

millimeter (mm)

square kilometer (km2)

By

0.3937

35.31

2.471

2.205

0.6214

0.1585

0.386

0.30481

0.03937

0.3861

To obtain

inch

cubic foot per second

acre

pound

mile

cubic foot per second

British ton

foot

inch

square mile

The following abbreviations are used in the report: microequivalent per liter (fxeq/L) and micromohls per liter (^imhos/L).

Temperature in degrees Celsius (°C) can be converted to degrees Fahrenheit (°F)

by use of the following equation:

°F= 1.8(°C) + 32.

Sea level: In this report, "sea level" refers to the National Geodetic Vertical Datum of 1929 (NGVD of 1929) a geodetic datum derived from 

a general adjustment of the first-order level nets of both the United States and Canada, formerly called "Sea Level Datum of 1929."

ABBREVIATED WATER-QUALITY UNITS

Chemical concentrations and water temperature are given in metric units. Chemical concentration is given in milligrams per liter (mg/L). 

Milligrams per liter is a unit expressing the concentration of chemical constituents in solution as weight (milligrams) of solute units of solute 

unit per unit volume (liter) of water. One thousand micrograms per liter is equivalent to one milligram per liter.

Conversion Factors, Vertical Datum, and Abbreviated Water-Quality Units V
EFFECTS OF SELECTIVE FOREST CLEARING, 

FERTILIZATION, AND LIMING ON THE HYDROLOGY 

AND WATER QUALITY OF A SMALL TRIBUTARY TO THE 

QUABBIN RESERVOIR, CENTRAL MASSACHUSETTS

By James B. Shanley, Jeffrey L. Strause, and John C. Risley

Abstract

Effects of selective forest clearing on water 

yield and water quality were investigated in a 308- 

hectare basin that drains to Quabbin Reservoir 

Watershed in central Massachusetts. The 

experimental basin and a nearby 280-hectare 

control basin were studied together for comparison. Streamflow was measured continuously and 

water-quality samples were collected biweekly in 

both basins from February 1985 through 

September 1989. During the same period, 

measurements of precipitation quantity and 

ground-water levels were made and samples were 

collected for determination of precipitation and 

ground-water quality.

After an initial monitoring period to establish 

baseline hydrology and water quality in both 

basins, an area of red pine and white pine forest in 

the experimental basin was cleared. From October 

1986 until April 1987, 23.8 percent of the total 

basal area was removed by clearcutting and 

thinning. Part of the cleared area was converted to 

rye and other field grasses, and the remainder 

was allowed to regrow naturally. Fertilizer and 

lime were applied to part of the cleared area. 

An additional 8.3 percent of basal area was cleared 

in autumn 1988.

Despite differences in bedrock geology, 

topography, and amount of wetland area, pre-treatment hydrology and chemistry of the two basins 

were similar. Biogeochemical reactions of the 

dilute mixture of sulfuric and nitric acids in precipitation with soils and rocks in the basins resulted in

moderately buffered calcium magnesium bicarbonate type streamwater. During high flows, sulfate 

concentrations increased and alkalinity decreased. 

Selective forest clearing resulted in a slight 

increase in water yield during the year in which the 

clearing took place, particularly during the spring 

high-flow period, but flows returned to normal 

thereafter. Concurrent increases in solute flux were 

primarily a function of the increased water flux. No 

major alterations to biogeochemical processes 

were induced by the forest clearing, nor were any 

effects from the fertilizer or liming activity 

observed. The minimal effect observed from the 

clearing was attributed primarily to the limited area 

that was cleared, and the location of the cleared 

area in the headwaters of the basin (away from the 

riparian zone).

INTRODUCTION

Quabbin Reservoir in central Massachusetts 

(fig. 1) is the principal source of water supply for the 

metropolitan Boston area. During the early 1980's, the 

average daily demand on the system exceeded the 

design capacity of the reservoir. Although system 

improvements and a recent conservation program have 

significantly reduced daily demand, the agencies 

responsible for municipal water supply and delivery, the 

Metropolitan District Commission (MDC) and the 

Massachusetts Water Resources Authority (MWRA), 

continue to seek viable ways to increase the water 

supply. The Division of Watershed Management of the 

MDC is required by State law to periodically prepare 

watershed management plans that provide for water 

yield enhancement.

Introduction 1
72* 22' 72° 17' 30"

42° 30'

42° 25'

Wendell

Shutesbury

NTROL BASIN 

Dickey Brook Tributary Basin)

42°

9 20 40 60 MILES 

0 204'ogO KILOMETERS

EXPLANATION

- BASIN BOUNDARY

PRECIPITATION STATION

RECORDING PRECIPITATION 

STATION

STREAM GAGE 

OBSERVATION WELL

EXPERIMENTAL BASIN 

{Dickey Brook Basin)

1\74569

Prescott 

Peninsula

National Atmospheric 

f^ Deposition Program 

Station

Base from U.S. Geological Survey

Quabbin Reservoir, 1967 Photorevised, 1979

Figure 1. Location of the study areas and data-collection sites near Quabbin Reservoir, central 

Massachusetts.

2 Effects of Forest Clearing, Fertilization, and Umlng on Hydrology and Water Quality, Quabbin Reservoir, Massachusetts
In addition to maintaining an adequate water supply, the MDC is equally concerned about maintaining 

water quality that is suitable for drinking and other 

municipal uses. Most of the land within the 482-km2 

Quabbin Reservoir drainage basin is managed as a protected area by the MDC; however, water quality may 

still be adversely affected by deicing-salt runoff 

(Shanley, 1994) and acid precipitation (Godfrey, 1988; 

Yuretich and others, 1989). The MDC is concerned that 

acidic precipitation may adversely affect aquatic life 

and upset the ecological balance in streams tributary to 

the reservoir and in the reservoir. Also, acidified water 

could increase the leaching of lead from service lines 

and plumbing, potentially causing tap water to have 

concentrations of lead that exceed drinking water 

standards. Weathering reactions with aquifer materials 

in the Quabbin watershed neutralize acid inputs, but the 

acid-neutralizing capacity of the reservoir is low 

compared to most bodies of water for its size. Forest 

clearing is another activity that may acidify surface 

waters (Lawrence and others, 1987); thus, cutting of 

trees also is of concern because of its potential effects 

on water quality.

In October 1984, the U.S. Geological Survey 

(USGS), in cooperation with the Watershed Management Division of the MDC, began the first of two phases 

of a 4'/2-year study to evaluate the effects of selective 

forest clearing on the quality of ground water and surface water in a tributary to the Quabbin Reservoir. In the 

first phase, water quality and hydrologic characteristics 

of two basins of the tributary were assessed before 

forest clearing. In the second phase, stands of red and 

white pine were selectively cleared in the experimental 

basin, and the cleared land was partially converted to 

limed, fertilized fields of grass. Water quality continued 

to be monitored in the experimental basin and the control basin during the post-treatment period, allowing an 

assessment of the effects of forest clearing and land 

conversion on water yield and water quality.

Purpose and Scope

This purpose of this report is twofold: (1) to 

present the effects of selective forest clearing on the 

hydrology of the basins, and (2) to present the effects of 

selective forest clearing on water quality.

This report summarizes hydrologic and waterquality data collected in Dickey Brook Basin and 

Dickey Brook Tributary Basin from October 1984

through September 1989. Collection of water-quality 

and hydrologic data in the control basin and the 

experimental basin began with instrumentation and 

some preliminary measurements in late 1984. Full data 

collection for the pre-treatment phase began in February 

1985. Selective forest clearing of red and white 

pine stands began in October 1986 and continued 

throughout the following winter. Data collection 

continued through September 1989.

Previous Studies

Results of previous studies of the effect of forest 

clearing on water yield generally have shown that water 

yield increases in proportion to the amount of forest 

cleared (Hornbeck and others, 1993). Likens and others 

(1970), Mrazik and others (1980), and Hornbeck and 

others (1993) have shown that runoff increases 

substantially in a watershed after forest clearing takes 

place. Verry (1986) points out, however, that forestclearing experiments have shown little effect on water 

yields in forests with high water tables, which are 

common in the Quabbin area.

At a 34-ha watershed in West Virginia, Aubertin 

and Patric (1974) found that runoff increased 200 mm 

during the first year after conventional clearcutting. 

Although most of the watershed was cleared, a small 

buffer zone of trees was left along the stream channel. 

Turbidity and nitrate-nitrogen and phosphate concentrations increased slightly during storms, but changes in 

stream temperature, pH, and turbidity between storms 

after clearcutting were negligible. Furthermore, little 

change was observed in concentrations of dissolved 

solids, calcium, magnesium, sodium, potassium, iron, 

copper, zinc, manganese, and ammonium.

During 1971-73, streamwater at the outlets of 23 

watersheds in the White Mountains of New Hampshire 

was sampled and analyzed for nitrate and calcium 

(Martin and Pierce, 1980). Nine watersheds were 

completely clearcut, seven watersheds were partially 

clearcut, and nine neighboring watersheds (selected 

as control watersheds) were undisturbed. Nitrate 

and calcium concentrations in the clearcut basins 

increased to maximums of 25.1 and 6.5 mg/L, 

respectively. Maximum nitrate and calcium concentrations of the undisturbed basins were 4.8 and 3.2 mg/L, 

respectively, during the period.

Introduction 3
Mrazik and others (1980) studied increases in 

water yield resulting from selective clearing of mature 

trees on the 163-ha Cadwell Creek Watershed of the 

Quabbin Reservoir. Removal of about one-third of the 

basal area of trees resulted in increases in water yield of 

22, 22, and 20 percent in the first 3 years after selective 

clearing.

Harr (1986) studied the effect of clearcutting on 

rain-on-snow runoff in western Oregon. He found 

that clearcutting altered snow accumulation and 

snowmelt patterns in a way that increased the size of 

peak streamflows caused by snowmelt during rainfall in 

a 96-ha and a 10-ha watershed.

The effects of two management practices, progressive strip cutting and block clearcutting, on the hydrology and water quality of small watersheds at the 

Hubbard Brook Experimental Forest, N.H. were studied 

by Hornbeck and others (1986). In the block-clearcut 

watershed, streamflow for the 10-year period after harvesting was 7 percent greater than it would have been 

had the trees in the watershed not been harvested. 

Streamflow during the same 10-year period in the stripcut watershed was 4 percent greater than it would have 

been had the trees in the watershed not been harvested. 

Maximum concentrations of calcium, magnesium, 

potassium, hydrogen, and nitrate collected from the 

block-clearcut watershed during the 10-year period 

were consistently higher than maximum concentrations 

of these constituents found in samples from the strip-cut 

watershed. Conversely, maximum concentrations of 

sodium, ammonium, sulfate, and chloride in runoff 

from the block-clearcut watershed were consistently 

lower than the maximum concentrations of these 

constituents in runoff from the strip-cut watershed.

Martin and Harr (1989) investigated the effect of 

the logging of mature Douglas fir trees in western 

Oregon on nutrient-output budgets. Three watersheds 

representing clearcut, partially cut, and undisturbed 

conditions were studied. Nitrate was the only measured 

constituent affected by logging. Despite a thirty-fold 

increase in nitrate export from the clearcut basin, nitrate 

concentrations were so low that more than twice as 

much nitrate-nitrogen was added to the clearcut 

watershed from precipitation as was lost in streamwater.

Experimental Design

A paired-watershed approach was used in this 

study to assess the effects of selective clearing on water 

yield and chemical fluxes from a small forested watershed. Whereas the design of this study is similar to 

earlier studies, few studies have specifically addressed 

the hydrologic and biogeochemical effects of long-term 

conversion to field cover. In the paired-watershed 

approach, two basins in close proximity were selected 

as the experimental and control basins. The best possible attempt was made to match basin characteristics, 

including mean elevation, drainage area, topography, 

soils, vegetation, and geology. Hydrologic and waterquality data were collected in both basins throughout 

the study. After lV2 years of baseline data were collected, red and white pine stands were selectively 

cleared in the experimental basin, and the cleared area 

was partially converted to rye and other field grasses. 

The control basin was left undisturbed.

In this study, both watersheds were monitored for 

lV2 years before forest clearing was initiated. During 

this time, relations in hydrologic and hydrochemical 

patterns between the basins are established. Effects of 

forest clearing were deduced from post-treatment 

changes in the nature of these relations. By comparison 

of the two basins, long-term trends were determined 

from seasonal variations.

Given a streamflow relation between the two 

basins for the pre-treatment period, the streamflows in 

the experimental basin during the post-treatment period 

had there been no clearing could be determined. The 

expected increase in water yield in the experimental 

basin during the post-treatment period resulting from 

the cutting can be quantified by subtracting calculated 

streamflows (calculated from an empirical pretreatment streamflow relation) from observed streamflows (Troendle, 1983; Troendle and King, 1985). Trimble and others (1987) applied an analogous technique to 

examine the reverse condition, that is, the reduction in 

water yield from reforestation in the Piedmont of the 

southern United States.

A similar method comparison of flow observed 

with flow predicted from a pre-treatment flow 

regression was used in this study. Changes in streamsolute flux caused by the forest clearing were likewise 

evaluated by examining differences in pre- and posttreatment. Patterns of solute fluxes in the experimental

4 Effects of Forest Clearing, Fertilization, and Liming on Hydrology and Water Quality, Quabbin Reservoir, Massachusetts
basin relative to those in the control basin were compared for the pre-treatment and post-treatment periods. 

Changes in flux were evaluated with reference to 

changes in water yield (for example, whether an 

increase of 10 percent in solute flux could be explained 

by an increase of 10 percent in water yield), and results 

were compared to results of other studies.

Description of Study Area

The study basins are on the Prescott peninsula in 

the Quabbin Reservoir Watershed in central Massachusetts (fig. 1). Dickey Brook Tributary, the control basin, 

drains 280 ha; Dickey Brook, the experimental basin, 

drains 308 ha. Both basins are mostly forested with a 

mixture of oak, eastern white pine, birch, red maple, 

hemlock, spruce, and red pine.

Bedrock geology in the study area is characterized 

by two distinct consolidated units of the Prescott Complex: a hornblende gabbro member, which covers nearly 

all of the eastern half of the control basin and less than 

10 percent of the experimental basin, and the 

Cooleyville Granitic Gneiss member, which underlies 

most of the western half of the control basin and nearly 

all of the experimental basin (fig. 2) (Makower, 1964; 

Zen and others, 1983). The presence of gabbro causes 

the pH of surface water in both basins to remain nearly 

neutral, in contrast to the more acidic surface water in 

most basins of similar size in the region (Gallant and 

others, 1990). Surficial geology includes unconsolidated deposits of mostly fine-grained till and some outwash. The unconsolidated deposits are more prevalent 

in the experimental basin than in the control basin 

(David Ashenden, Massachusetts Water Resources 

Authority, written commun., 1987).

The average topographic gradient between the 

highest point in the basin and the basin outlet is about 5 

percent in the control basin and about 2 percent in the 

experimental basin. Drilled boreholes in the study area 

indicate that the till thickness ranges from about 1.5 to 

12.0 m. Slopes facing north and west consistently have 

thicker till deposits than slopes facing south and east. 

Soils in both basins are fine sandy loam with 

permeability ranging from 5.1 to 16.0 cm/h. The available water capacity ranges from about 10 to 20 percent. 

By area, wetlands comprise about 15 percent of the 

experimental basin and 4 percent of the control basin.

Wetlands in both basins support beaver colonies, 

resulting in the loss of tree cover; regrowth has been 

limited because of deer browsing.

Red pine stands were planted throughout the 

Quabbin Reservoir Watershed during the construction 

of the reservoir in the 1930's and 1940's. Red pine was 

the only tree species that was thinned or clearcut during 

the study. Because the annual water consumption of 

pines is higher than the annual water consumption of 

other tree species, the elimination of pine stands has 

been considered a viable means of increasing the water 

yield from basins contributing to the reservoir.

During the main period of forest clearing in the 

first half of water year 1987 1 ,21.9 ha of pine forest was 

cleared and 9.3 ha was thinned in the experimental 

basin (fig. 3). The overall reduction of forest basal area 

(total cross-sectional area of tree stems) was 23.8 percent (table 1). Because pines have a higher stocking 

density than other trees in the basins, this 23.8-percent 

reduction in basal area was achieved by clearing only 

7.1 percent and thinning 3.0 percent of the basin area. 

Of the 21.9 ha in the initial clearing, part of the area was 

harrowed; 2.7 ha was planted to rye grass and 4.1 ha 

was planted to field mix (table 1) in September 1987. 

The remaining cleared area was allowed to regrow naturally. The grass area was fertilized in October 1987 and 

limed in September 1988. From October 24 through 

December 8, 1988, an additional 8.3 percent of basal 

area was removed by a clearing of 6.5 ha and thinning 

of 5.7 ha of pine stands in the northern section of the 

basin near the outlet.

Acknowledgments

We wish to thank Karen Eager and Bruce Spencer 

of the Metropolitan District Commission for supplying 

data and supplementary information for this study. 

Gardner C. Bent of the U.S. Geological Survey, Marlborough, Mass., made many helpful suggestions for the 

hydrologic analyses. Leslie A. DeSimone of the U.S. 

Geological Survey, Marlborough, Mass., helped 

extensively with figure drafting and text organization.

'Water year is the 12-month period, October 1 through September 30. The water year is designated by the calendar year in 

which it ends and which includes 9 of the 12 months. Thus, the year 

ending September 30, 1980, is called "water year 1980."

Introduction 5
72* 22 72' 20'

42° 28

42° 26'

EXPLANATION

TILL DEPOSITS OR 

ALLUVIAL OUTWASH

HORNBLENDE GABBRO

COOLEYVILLE GRANITIC 

GNEISS

BASIN BOUNDARY 

PRECIPITATION STATION

RECORDING PRECIPITATION 

STATION

STREAM GAGE 

OBSERVATION WELL

CONTROL BASIN 

Dickey Brook Tributary Basin)

Base from U.S. Geological Survey

Quabbin Reservoir, 1967 Photorevised, 1979

Figure 2. Geology of the control and experimental basins near Quabbin Reservoir, central 

Massachusetts.

6 Effects of Forest Clearing, Fertilization, and Uming on Hydrology and Water Quality, Quabbin Reservoir, Massachusetts
72° 22'

42° 28'

42° 26'

72' 20'

EXPLANATION

CLEARED, FERTILIZED, 

AND LIMED AREA

 BASIN BOUNDARY

^ PRECIPITATION STATION

$ RECORDING PRECIPITATION 

STATION

STREAM GAGE 

IS. OBSERVATION WELL

New Salem

CONTROL BASIN 

* (Dickey Brook Tributary Basin)

.EXPERIMENTAL BASIN 

\i(Dickey Brook Basin)

1MILE

1 KILOMETER

Base from U.S. Geological Survey

Quabbin Reservoir, 1967 Photorevised, 1979

Figure 3. Areas of forest clearing fertilization, and liming in the experimental basin near Quabbin 

Reservoir, central Massachusetts.

Introduction 7
Table 1. Summary of forest-clearing, fertilization, and liming treatments in the experimental basin. Dickey 

Brook Basin, central Massachusetts

[--, not applicable]

Area

Period of activity (date) Land area (hectare) Basal area (percentage of watershed)

Start End Clearcut Thinned Clearcut Thinned Total

Forest clearing

Initial clearing: 

Lily Pond area 

Basin outlet area

Total - initial

Final clearing: 

Basin outlet area

Total - initial + final

Date

8/87 -9/87

9/87

9/87

10/5/87

9/28/88

10/22/86 4/1/87 

10/22/86 4/1/87

--

10/22/88 12/8/88

--

Additional

Area (hectare)

7.9

2.7

4.1

4.9

6.1

21.4 7.8 19.1 

.5 1.5 .5

21.9 9.3 19.6

6.5 5.7 5.8

28.4 15.0 25.4

treatments in area northeast of Lily Pond

Activity

Removal of tree stumps, raking, harrowing

Seeding with rye grass

Seeding with field mix

3.5

.7

4.2

2.5

6.7

22.6 

1.2

23.8

8.3

32.1

Fertilizer [1, 415 kilogram 20-10-10 (nitrogen-phosphorus-potassium)] 

applied to all of field-mix area and part of rye grass area

Lime applied (34.5 metric tons)

METHODS OF STUDY

Intensive data collection for the pre-treatment 

characterization of the water quality and hydrology 

of the two basins began in February 1985. Data collection continued through the treatment period until the 

end of September 1989. Stream stage was recorded at 

15-minute intervals at the control basin outlet, the 

experimental basin outlet, and a headwater site in the 

experimental basin (fig. 1). Other data-collection 

activities included continuous recording of precipitation in or near the basins, weekly collection of precipitation samples for chemical analysis, biweekly surfacewater sample collection (augmented by automated 

sample collection during high flow), weekly measurement of ground-water levels, and collection of groundwater samples every 2 months.

Hydrologic Data Collection

Precipitation volumes were measured by a continuous-recording rain gage in the control basin and 

another downstream from the outlet of the experimental 

basin. Two nonrecording rain gages in or near each

basin were monitored weekly in 1985 to assess areal 

variations in precipitation quantity and to serve as 

backup for the recording gage.

The three streamflow-gaging stations are shown in 

figure 1. The gages at the two basin outlets were 

equipped with stage-sensing manometers linked to 

digital recorders that recorded gage height every 

15 minutes. Gage-height-discharge rating curves were 

developed from periodic measurements at the sites. 

These two gages had natural controls (no weir 

structures). The headwaters gage in the experimental 

basin was downgradient from the area where 

most of the clearing and thinning was done. During the 

pre-treatment period, instantaneous streamflow 

measurements were made intermittently at this site. 

In July 1986, a few months before the clearing was 

begun, a V-notch weir with a pressure transducer for 

stage recording was installed.

Streamflow was calculated from stream gage 

heights based on standard techniques applied at USGS 

gaging stations (Rantz and others, 1982). The base-flow 

component of streamflow was separated on the basis of 

the graphical technique of Davis and DeWeist (1966).

8 Effects of Forest Clearing, Fertilization, and Liming on Hydrology and Water Quality, Quabbin Reservoir, Massachusetts
Three observation wells were installed in each 

basin (fig. 1). All were completed in unconsolidated 

deposits to the apparent depth of the bedrock surface 

(except for one well purposely screened in more shallow till). The wells were cased with polyvinylchloride 

(PVC), and each was completed with 1.5 m of PVC 

screen. Water levels in wells were measured weekly. 

Well NLW15 in the experimental basin was in the flood 

plain close to the basin outlet. Wells NLW16 and 

NLW17 were in the headwaters of the experimental 

basin. Well NLW12 in the control basin was near the 

edge of a wetland area and also near to the basin outlet. 

Wells NLW14 and NLW13 were in well-drained 

uplands in the headwaters of the control basin.

Water-Quality Data Collection

Weekly precipitation-quality samples were collected with an Aerochem Metrics Model 301 wetfalldryfall collector at a site in New Salem about 8 km north 

of the control basin (fig. 1). Precipitation samples were 

analyzed for 11 selected constituents (table 2). Because 

the inherent variability of precipitation chemistry precludes the use of a model to simulate concentrations 

when data are missing, data from the National Atmospheric Deposition Program (NADP) site at Quabbin 

Observatory (Bigelow, 1982), 5 km south of the study 

area, were used to assemble a complete record of 

weekly precipitation quantity and quality data. (NADP 

data were used on average, 1 week for every 10 weeks 

of record.) The New Salem precipitation collector was 

sampled each Tuesday to coincide with the sampling 

schedule of the (NADP); precipitation data from the 

NADP were used in some of the data analyses.

Surface-water samples were collected every 2 

weeks from the centroid of flow at each of the two basin 

outlet gages, and intermittently from the headwaters 

gage in the experimental basin. Samples were analyzed 

for 11 selected constituents (table 2). Surface-water 

samples were collected more frequently during spring 

snowmelt and selected storms to ensure an adequate 

representation of high flow.

Samples were collected from the six wells every 2 

months and were analyzed for 11 selected constituents 

(table 2). The wells were purged at least 1 week before 

each sampling by evacuating several well volumes with

Table 2. Chemical constituents analyzed for the 

study near Quabbin Reservoir, central Massachusetts

Constituent

Hydrogen ion

Calcium

Magnesium

Sodium

Potassium

Alkalinity

Sulfate

Chloride

Silica

Nitrate

Dissolved organic carbon

Abbreviation

H+

Ca

Mg

Na

K

ALK

S04

Cl

Si

NO3

DOC

Use of the brand names in this report is for identification 

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

Geological Survey.

a centrifugal pump, and then a second time 1 to 2 days 

before samples were collected. Samples were collected 

with a bailer.

Specific conductance and pH were measured in all 

samples generally within 24 hours of collection. Alkalinity was measured in stream samples and groundwater samples by fixed-endpoint titration to pH 4.5. 

Concentrations of the other nine selected constituents 

(table 2) were determined at the USGS central laboratory in Arvada, Colo., by standard methods (Fishman 

and Friedman, 1989). Sediment samples were analyzed 

at the USGS laboratory in Harrisburg, Pa., to determine 

suspended-sediment concentrations.

Hydrologic Data Analysis 

Calculations of Flow

Daily mean streamflows from the outlets of the 

control and experimental basins during the pre- and 

post-treatment periods were analyzed to determine the 

effects of selective forest clearing on the hydrology of 

the experimental basin. Daily mean streamflows of the 

experimental basin were regressed on daily mean 

streamflows of the control basin separately for the preand post-treatment periods. The slopes and the 

intercepts of the two regression equations were tested 

for statistical differences by analysis of covariance 

(Helsel and Hirsch, 1992). A significant change in the

Methods of Study 9
slope and (or) intercept of the two equations would indicate that selective forest clearing caused an alteration in 

the hydrology of the experimental basin.

Construction of Flow-Duration Curves

A second approach to detect the effect of selective 

forest clearing on the hydrology of the experimental 

basin is flow-duration curves. A flow-duration curve, 

computed from the daily mean streamflows, shows the 

percentage of time a given flow is exceeded. The shape 

of a flow-duration curve is affected by the runoff 

characteristics of a specific basin, and it also reflects the 

climatic regime for the period of record from which the 

data are derived. Flow-duration curves were generated 

for both the pre- and post-treatment periods for each 

basin. The four flow-duration curves allowed a 

comparison of the flows from both basins during the 

same time period. The regression equation developed 

from the pre-treatment flow data was used to estimate 

daily mean flows for the post-treatment period as if no 

clearcutting was done in the experimental basin. An 

additional pair of flow-duration curves was generated to 

compare the estimated flows to the actual flows during 

the post-treatment period in the experimental basin.

Calculations of Evapotranspiration

Monthly potential evapotranspiration at the control 

and experimental basins was estimated by the 

Thornthwaite method (Thornthwaite and Mather, 

1955). Air temperature is applied in the method as an 

index of the energy available for evapotranspiration and 

makes no correction for different vegetation types. The 

empirical formula developed by Thornthwaite for the 

continental United States is

The annual heat index is computed as follows:

ET = 1.6 (1)

where

ET is potential evapotranspiration, in

centimeters per month, 

Ta is mean monthly air temperature, in

degrees Celsius, 

is an annual heat index, and 

is a computed coefficient.

12

(2)

where

i is the month of the year

The coefficient a is computed as follows:

a = 0.49 + (0.0179)7- (0.0000771)/2+

(0.000000675)/3 (3)

7 

a

Potential evapotranspiration computed from 

equation 1 was adjusted by a correction factor for 

monthly sunshine duration. During periods of normal 

or above-normal precipitation, estimated monthly 

potential evapotranspiration for a forested region in the 

humid northeastern United States is a reasonable 

approximation of actual monthly evapotranspiration 

(Dunne and Leopold, 1978).

The change in evapotranspiration in the experimental basin during the post-treatment period was 

estimated as the difference between the actual daily 

flow and the estimated daily flow calculated from the 

regression equation that was developed from the pretreatment daily mean flows of both basins. Annual 

estimates of the change in evapotranspiration were 

made by aggregating the daily differences.

Water-Quality Data Analysis

The general validity of the chemical analysis on 

each sample was evaluated on the basis of ion balance. 

Samples for which ion-balance discrepancies greater 

than 10 percent were eliminated from the data base with 

the exception of low-ionic-strength precipitation samples; for precipitation samples with total ionic composition less than 100 ^teq/L, an ion-balance discrepancy of 

up to 30 percent was tolerated. Additionally, data from 

each sampling location were screened for internal consistency by evaluating outliers on time plots and (or) 

concentration-discharge plots. Most outliers could be 

traced to recording of incorrect time or date, or erroneous stream discharge. Outliers that could not be rejected 

on the basis of ion balances and (or) by recording errors 

were retained in the data base. Occasionally, a precipitation sample was not obtained because of sample 

contamination or sampler malfunction.

10 Effects of Forest Clearing, Fertilization, and Liming on Hydrology and Water Quality, Quabbin Reservoir, Massachusetts
Solute-Concentrations Models Calculation of Solute Loads

Regression models were developed to simulate 

solute concentrations as a function of streamflow and 

(or) season following the method of Huntington and 

others (1994). Instantaneous streamflow was used 

directly as input to some of the regressions, but various 

transformations also were made on streamflow to obtain 

the optimum form of discharge term for each solute. 

Transformations included a log-transform and a transform of the type l/(l+pQ), where Q is discharge and (3 

is a coefficient that is optimized for the best model fit. 

In addition, for each sampling time, average streamflows for a series of time intervals before the sampling 

time were calculated. The time periods were 1,6, and 12 

hours, and 1,2,5, 10, 15, 30,45,60, and 90 days. These 

average streamflows were applied as an estimate of 

antecedent flows in the chemical processes. Average 

streamflows were transformed in the same manner as 

the instantaneous streamflow to yield the optimum 

discharge term for each model. No model included 

more than one streamflow term; that is, either instantaneous or an antecedent average streamflow, or some 

transformation of either term, was used.

The seasonal component in the regression models 

was represented by sine and cosine terms with annual 

periodicity. Inclusion of both sine and cosine terms- as 

independent variables enabled the models to adjust for 

phase. For example, if two solutes were characterized 

by annual concentration cycles that peaked on July 1 

and October 1, the model simulating the first solute 

would place all the weight on the cosine term and would 

not include a sine term (coefficient of zero), whereas the 

opposite applies for the second solute.

Models were optimized based on the highest coefficient of determination (r2), but special attention was 

paid to model residuals. Models having constantresidual variance (homoscedasticity) were favored over 

models that may have had a higher IT but a poor distribution of residuals. In particular, models where concentrations were poorly simulated at high flows were 

rejected because of the important effect of high-flow 

periods on chemical flux.

The regression models were used not only to 

calculate fluxes of constituents, but also to gain 

insight into the processes that affect the solute chemistry in the stream. Model structure, such as whether 

concentrations increased or decreased with increasing 

streamflow, or whether the seasonal maximum was in 

summer or winter, aided in the interpretation of 

biogeochemical processes in the study basins.

Solute fluxes in precipitation were calculated from 

the weekly sample data as the product of solute 

concentration and weekly precipitation volume. 

Separate calculations of solute fluxes were made in each 

basin on the basis of separate measurements of 

precipitation volume; concentrations were assumed to 

be the same. Solute fluxes in precipitation were summed 

by water year.

Stream-solute fluxes were calculated as the 

summed product of the continuous hydrograph and the 

continuous chemographs generated from the regression 

models. Output fluxes were calculated at a 5-minute 

time step. Residuals from the regression models were 

used to adjust the calculated concentrations at each time 

step. Adjustments were based on a linear interpolation 

of the residuals between the two observations bracketing the time step. For example, the hypothetical model 

residual for observation n at time tj is +1 fieq/L and the 

model residual for the next observation n+1 at time t2 is 

+2 fieq/L. At a time exactly intermediate between tj and 

t2 , the interpolated residual is +1.5 fieq/L; thus, 

1.5 fieq/L is added to the model-simulated solute 

concentration before the flux is calculated at that time 

step. Stream-solute fluxes were summed by water year 

and normalized to the area of each basin for ready 

comparison between the two basins.

PRE-TREATMENT HYDROLOGIC 

CHARACTERISTICS OF EXPERIMENTAL 

AND CONTROL BASINS

The hydrology and geology of the two basins are 

not identical. The control basin has steeper topography 

and better drainage, as indicated by the smaller extent of 

wetland areas. The effects of clearing on water yield are 

less significant in forests with high water tables; wetland areas cause greater evaporation and "luxury 

consumption" of water by the riparian forest (Verry, 

1986). From a chemical standpoint, it was thought that 

the greater amount of gabbro bedrock in the control 

basin would make chemical comparisons to the 

experimental basin problematic.

Precipitation

Annual precipitation quantities were nearly identical in the two basins during water years 1985-89 

(fig. 4). Annual precipitation during this period 

averaged 1,200 mm for the control basin and 1,158 mm

Pre-Treatment Hydrologic Characteristics of Experimental and Control Basins 11
O uu

LUDC ° 

Q. Z

150

100

50

CONTROL 

EXPERIMENTAL

1985

(PARTIAL YEAR)

1986 1987 

WATER YEAR

1988 1989

Figure 4. Precipitation in the control and experimental basins, Dickey Brook Basin near Quabbin 

Reservoir, central Massachusetts, water years 1985-89.

for the experimental basin. The correlation coefficient 

for monthly precipitation computed from measured 

daily precipitation at the two sites during the 4V2-year 

study was 0.979. Quantities at each of the two nonrecording gages within each basin were usually within 

2.5 mm of the weekly total measured precipitation at 

the recording gage in that basin.

At a National Weather Service observation station 

at New Salem (fig. 1), the long-term average annual 

precipitation derived from nearly 45 years of record is 

1,247 mm (National Oceanic and Atmospheric Administration, 1985). Precipitation is evenly distributed 

throughout the year. Mean monthly precipitation at 

New Salem for the period of record ranges from 66 to 

104 mm. Approximately 20 percent of annual precipitation falls as snow. At New Salem, annual precipitation 

exceeded the long-term average during each water year 

of this study: by 51 mm in 1986, by 187 mm in 1987, by 

50 mm in 1988, and by 399 mm in 1989 (Bent, 1994).

Greater precipitation can be expected at the New 

Salem gage relative to the control and experimental 

basins because the New Salem gage is at a higher elevation. Bent (1994) showed that precipitation at New 

Salem averaged 21 percent more than that at the control 

and experimental basins on an annual basis.

Surface-Water Flow

The precipitation-runoff characteristics of the two 

basins under undisturbed conditions were analyzed on 

the basis of daily mean streamflow data from the pretreatment period of the study. In the only complete 

water year of the pre-treatment period, water year 1986, 

mean annual stream discharge was 40.78 L/s in the 

control basin and 45.03 L/s in the experimental basin.

During the pre-treatment period, base flow accounted 

for nearly 75 percent of the total streamflow in both 

basins (fig. 5). Estimates of the base-flow components 

from four other basins contributing to the Quabbin Reservoir range from 37 to 73 percent of total stream 

discharge (Stekl, 1985; Rittmaster and Shanley, 1995).

Hydrographs from the two basins throughout the 

duration of the pre-treatment period (fig. 5) indicate that 

the timing of peak flows was very similar. However, the 

recession following peak flow characteristically was 

more rapid in the experimental basin relative to 

recession in the control basin. The experimental basin 

apparently has less storage capacity than the control 

basin. Wetlands account for 15 percent of the 

experimental basin but only for 4 percent of the control 

basin; therefore, more area in the experimental basin 

has a water table at or near land surface than in the 

control basin. Thus, the wetlands function as saturated 

contributing areas; precipitation and snowmelt on the 

wetland areas contribute directly to surface-water 

runoff. A greater proportion of the stormwater leaves 

the experimental basin as surface flow and less water 

reaches the underlying aquifer; thus, the hydrograph 

recession is curtailed.

The flashier response of the experimental basin is 

consistent with theories on streamflow generation based 

on topographic considerations. Basins with convergent 

gentle slopes are more likely than steeper catchments to 

develop extensive zones of surface saturation near 

stream channels (Dunne and others, 1975). Precipitation or snowmelt on these saturated contributing areas 

travels directly to stream channels as saturation-excess 

overland flow. Although other factors such as depth to 

bedrock and soil permeability are important,

12 Effects of Forest Clearing, Fertilization, and Liming on Hydrology and Water Quality, Quabbin Reservoir, Massachusetts
o 

o

LU 

CO 

DC 

LU

a_

LLJ 

LU 

LL

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DO

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u_

LU 

DC

o

100

10

1.0

0.1 -

0.01

100

10

1.0

0.1

0.01

EXPERIMENTAL BASIN

DOTTED LINE IS ESTIMATED BASE FLOW

CONTROL BASIN

DOTTED LINE IS ESTIMATED BASE FLOW

FEB MAR APR MAY JUNE JULY AUG SEPT OCT NOV DEC

1985

JAN FEB MAR APR MAY JUNE JULY AUG SEPT 

1986

Figure 5. Streamflow and base flow in the experimental and control basins near Quabbin Reservoir, 

central Massachusetts, during the pre-treatment period, February 1985 through October 1986.

topography alone commonly can account for much of 

the hydrologic conditions in a basin (Wolock and 

others, 1990). Topographic indices, which are derived 

from local slope and the upslope contributing area at 

each point in a basin, were not computed in this study. 

However, given the substantially lower average slopes 

in the experimental basin (2 percent compared to 5 percent in the control basin), the experimental basin should 

have a greater potential to generate rapid runoff during 

storms and snowmelt than the control basin. The steeper

slopes of the control basin could contribute to rapidresponse streamflows only if permeable soils or extensive macroporosity were present to cause a rapid subsurface response; the steep slopes would then enhance 

rapid downslope flow of water to a stream channel.

The capacity of the control basin to sustain 

base flow is confirmed by greater flows between the 

10th and 70th percentiles in flow-duration curves computed from pre-treatment data (fig. 6). The similarity in 

the flow-duration curves above the 70 percentile is

Pre-Treatment Hydrologic Characteristics of Experimental and Control Basins 13
100

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DC

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Q.

C/5

QC 

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DC 

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QC 

LJLJ 

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CONTROL BASIN (Dickey Brook Tributary Basin) 

EXPERIMENTAL BASIN (Dickey Brook Basin)

10 20 30 40 50 60 70

PERCENTAGE OF TIME FLOW IS EXCEEDED

80 90 100

Figure 6. Flow-duration curves for the experimental and control basins near 

Quabbin Reservoir, central Massachusetts, during the pre-treatment period, 

February 1985 through October 1986.

indicative of a limit to this base-flow-generating 

reservoir in the control basin. At low flows, both basins 

may supply base flow from deeper ground-water 

sources within similar low permeability substrates.

Peak discharges for various recurrence intervals 

were estimated for the two basins on the basis of a 

regional regression model (Wandle, 1983). The peak 

discharge for a given recurrence interval is a function of 

the drainage area and the total area of wetlands and 

ponds in the basin. The estimated 2-year peak flow was 

1,560 L/s in the control basin and 1,590 L/s in the 

experimental basin. The estimated 100-year peak flow 

was 9,260 L/s in the control basin and 8,440 L/s in the 

experimental basin. The increasing attenuation of peak 

flows in the experimental basin relative to the control 

basin is caused by the larger area of wetlands in the 

experimental basin. As the recurrence interval 

increases, conversion of the experimental basin to

grassland would be expected to increase water yield primarily through increases in base-flow yields (Hornbeck 

and others, 1993). However, elevated soil moisture as a 

result of reduced evapotranspiration may also lead to 

higher peak-storm discharges and higher flows for a 

given recurrence interval (Verry, 1986).

Ground-Water Levels

Hydrographs of ground-water levels from 

one observation well in each of the two basins (fig. 7) 

show typical responses to seasonal changes in 

evapotranspiration and recharge. Ground-water levels 

generally decline during spring and summer (the 

growing season) where evapotranspiration is greater 

than recharge. Ground-water levels generally rise 

during fall and reach their highest levels in early spring 

in response to recharge from precipitation and 

snowmelt. Because a greater proportion of the area of

14 Effects of Forest Clearing, Fertilization, and Liming on Hydrology and Water Quality, Quabbin Reservoir, Massachusetts
LJJ

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2

DC

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CO 

Q

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LJJ 

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CONTROL BASIN-Dickey Brook Tributary Basin Well #NLW14 

EXPERIMENTAL BASIN-Dickey Brook Basin Well #NLW16

JAN APR JULY 

1985

OCT JAN APR JULY 

1986

OCT

Figure 7. Ground-water levels in two wells in the experimental and control basins near 

Quabbin Reservoir, central Massachusetts, during the pre-treatment period, February 

1985 through October 1986.

the experimental basin is made up of wetlands, the 

water table in the experimental basin generally is closer 

to land surface than the water table in the control basin. 

Although ground-water-level fluctuations vary considerably depending on the topographic setting, data from 

the small number of wells in this study indicate that 

ground-water fluctuations in the experimental basin are 

less variable than those in the control basin.

PRE-TREATMENT WATER-QUALITY 

CHARACTERISTICS OF EXPERIMENTAL 

AND CONTROL BASINS

An overview of pH, alkalinity, and solute concentrations of the major chemical constituents in precipitation, surface water, and ground water from both the 

experimental and control basins during the pretreatment period is shown in figure 8. The boxplots 

summarize the median and range of concentrations for 

each solute. They provide a format for comparison of

solute concentrations among precipitation, ground 

water, and surface water within each basin and for 

comparison of surface water and ground water between 

the two basins.

Precipitation

Precipitation at the study basins can be characterized as a dilute mixture of sulfuric and nitric acids, as 

has been described at other sites in the northeastern 

United States (Likens and others, 1977; Gorham and 

others, 1984). Hydrogen ion was the dominant cation; 

the pH of precipitation ranged from 3.5 to 4.8 (fig. 8). 

Sulfate tended to dominant over nitrate but by less than 

the 2:1 ratio that is common in precipitation in the 

northeastern United States (Likens and others, 1977). 

The sum of base cations (calcium, magnesium, sodium, 

and potassium) generally balanced less than 20 percent 

of the strong acid-anion component. Similarly, chloride 

was a minor component of precipitation.

Pre-Treatment Water-Quality Characteristics of Experimental and Control Basins 15
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BEYOND THE QUARTILE

DATA-COLLECTION SITES SHOWN IN FIGURE 1

1 - New Salem Precipitation Station

2 - Observation Well NLW13 (11 feet deep)

3 - Observation Well NLW12 (16 feet deep)

4 - Observation Well NLW14 (22 feet deep)

5 - Control Basin Outlet

6 - Experimental Basin Outlet

7 - Experimental Basin Headwaters Gage

8 - Observation Well NLW15 (11 feet deep)

9 - Observation Well NLW16 (15 feet deep)

10 - Observation Well NLW17 (44 feet deep)

Figure 8. pH, alkalinity, and solute concentrations at New Salem, the control basin, and the experimental 

basin near Quabbin Reservoir, central Massachusetts, during the pre-treatment period, February 1985 

through October 1986.

16 Effects of Forest Clearing, Fertilization, and Liming on Hydrology and Water Quality, Quabbin Reservoir, Massachusetts
NEW SALEM 

450

EXPERIMENTAL BASIN

B.

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Pre-Treatment Water-Quality Characteristics of Experimental and Control Basins 17
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18 Effects of Forest Clearing, Fertilization, and Liming on Hydrology and Water Quality, Quabbin Reservoir, Massachusetts
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Figure 8. Continued.

Pre-Treatment Water-Quality Characteristics of Experimental and Control Basins 19
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Figure 8. Continued.

20 Effects of Forest Clearing, Fertilization, and Liming on Hydrology and Water Quality, Quabbin Reservoir, Massachusetts
NEW SALEM 

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Figure 8. Continued.

Surface Water

Biogeochemical processes in each basin transform 

unbuffered, mildly acidic, low-base-cation precipitation 

inputs to weakly buffered solutions of calcium magnesium sulfate and calcium magnesium bicarbonate type 

waters. Water that enters the basins in precipitation participates in biogeochemical reactions as it flows to the 

stream. As a result, total solute loads increase markedly 

and relative solute concentrations change. Base cations 

replace hydrogen ion, bicarbonate becomes a major ion 

along with sulfate, and nitrate becomes a minor constituent. The small amount of data available from the headwater site in the experimental basin indicates that 

alkalinity at the headwater site was approximately onehalf the alkalinity at the outlet gage; thus, water at the 

headwater site has undergone less neutralization.

Despite the differences in hydrology and surficial 

and bedrock geology among the two basins, solute 

concentrations (fig. 8) and annual solute budgets (see

below) were similar. Two explanations are proposed for 

the similarity in solute concentrations in the two basins. 

First, solute chemistry is affected less by bedrock than 

by soils and unconsolidated materials, which may be 

more similar between basins than the bedrock. Second, 

increased solute contributions from the greater percentage of gabbro in the control basin are offset by shorter 

hydrologic residence times due to the steeper topography and the lower percentage of wetlands in that basin. 

The case for shorter hydrologic residence time in the 

control basin is supported by the lower solute concentrations in ground water relative to the experimental 

basin (fig. 8). In the experimental basin, longer groundwater residence time may be a factor that increased 

solute concentrations in streamwater.

Some notable differences were found in the 

surface-water chemistry in the two basins. Concentrations of calcium, magnesium, and potassium all were 

slightly higher in the control basin (figs. %A, SB, and 

8Z)), whereas alkalinity and concentrations of silica

Pre-Treotment Water-Quality Characteristics of Experimental and Control Basins 21
were significantly higher in the 

control basin (figs. SE and 8J). 

These differences can be attributed 

to the greater percentage of the control basin underlain by the more 

reactive gabbro. Sulfate 

concentrations also were slightly 

higher in the control basin 

(fig. 8G), indicating that sulfide 

mineral weathering may occur in 

the control basin and (or) that sulfate reduction may occur in the 

wetlands of the experimental basin.

Calcium magnesium sulfate 

and calcium magnesium bicarbonate type waters were present in 

streamwater in the two basins at 

various times during the pretreatment period are indicated in 

the trilinear diagrams shown in 

figure 9. These diagrams were plotted separately for streamflows of 

less than and streamflows greater 

than 21.2 L/s (this amount of 

streamflow approximately separates the base flow and the surfacerunoff components of streamflow). 

This division illustrates the change 

from calcium magnesium bicarbonate to calcium magnesium sulfate 

type water as streamflow increases. 

Very little change was measured in 

the cation ratios of the high-flow 

and base-flow waters.

Ground Water

In general, the concentrations 

of constituents from the experimental basin were higher than those in 

the control basin. Samples from 

two or more wells in the experimental basin had median concentrations of calcium, magnesium, 

sodium, chloride, and alkalinity 

that were higher than the corresponding medians for ground-water 

samples in the control basin. Samples from the deepest well NLW 17

EXPLANATION

a CONTROL BASIN

o EXPERIMENTAL BASIN

STREAMFLOW

LESS THAN 0.75

CUBIC FOOT PER SECOND

STREAMFLOW

GREATER THAN 0.75

CUBIC FOOT PER SECOND

Ca Cl 

PERCENTAGE OF TOTAL MILLIEQUIVALENTS PER LITER

Figure 9. Percentage of chemical constituents in streamwater from 

the control and experimental basins, Dickey Brook Basin, central 

Massachusetts, during the pre-treatment period, February 1985 

through October 1986.

22 Effects of Forest Clearing, Fertilization, and Liming on Hydrology and Water Quality, Quabbin Reservoir, Massachusetts
(13.4 m) generally had higher concentrations of most constituents 

than samples from shallower wells 

(3.35 and 6.7 m). None of the samples from the wells from either 

basin was considered to be completely representative of the typical 

ground-water quality of that basin.

Judging from physical characteristics of the basin, ground water 

in the experimental basin would be 

expected to have higher solute concentrations than ground water in 

the control basin. The experimental 

basin has a gentler slope and a 

greater proportion of wetlands (15 

percent as compared to 4 percent). 

Thus, ground water would be 

expected to have a longer residence 

time in the experimental basin. 

Seasonal ground-water fluctuations 

in the experimental basin were less 

variable, and mean water levels 

were closer to land surface. Differences in ground-water chemistry 

between the two basins should not 

be rigorously compared because 

the number of sites is small (three 

wells in each basin) and because 

the spatial variability of the 

ground-water chemistry is typically large. Trilinear diagrams that 

depict the ratios of cations and 

anions in ground-water (fig. 10), 

however, indicate that the percentage of sulfate was higher in the 

control basin than in the experimental basin. The relatively high 

sulfate concentration may be 

derived from weathering of sulfide 

minerals, as discussed previously, 

or from atmospheric sulfate that 

has not been removed from 

solution. Alternatively, it may 

reflect greater sulfate reduction in 

the more wetland-dominated 

experimental basin. Bicarbonate 

was proportionally higher in the 

experimental basin, indicating a 

greater degree of weathering than 

in the control basin.

EXPLANATION

OBSERVATION WELLS 

O NLW 12 

A NLW 13 

+ NLW 14

CONTROL BASIN

EXPLANATION

OBSERVATION WELLS 

O NLW 15 

A NLW 16

-f NLW 17

Cl

EXPERIMENTAL BASIN

PERCENTAGE OF TOTAL MILLIEQUIVALENTS PER LITER

Figure 10. Percentage of chemical constituents in ground water from 

the control and experimental basins. Dickey Brook Basin, central 

Massachusetts, during the pre-treatment period, February 1985 

through October 1986.

Pre-Treatment Water-Quality Characteristics of Experimental and Control Basins 23
EFFECTS OF SELECTIVE FOREST CLEARING 

ON HYDROLOGY

Thus far, the control basin (Dickey Brook Tributary) and the experimental basin (Dickey Brook) have 

been compared and contrasted on the basis of pretreatment conditions. In the remainder of the report, the 

overall effect of selective forest clearing and partial 

conversion to field cover on the hydrology of the experimental basin is assessed. The next section examines the 

effect on the hydrology, and the subsequent section 

examines the effect on water quality.

Changes in Surface-Water Flow

The effect of selective forest clearing on streamflow can be assessed by a comparison of annual totals of 

precipitation and runoff (streamflow/basin area) from 

the two basins (fig. 11). During water year 1987, the 

year in which most of the forest clearing took place, 

runoff in the experimental basin was more than 50 mm 

greater than runoff in the control basin. In each of the 

other years, runoff from the experimental basin was 

slightly less than runoff from the control basin. The

increased runoff from the experimental basin during 

water year 1987 began in March and extended through 

the end of the growing season in October; the greatest 

increase was in March and April 1987 (fig. 12). This 

period of increased streamflow coincided with the completion of the first and largest phase of the selective 

forest clearing. Because the forest clearing did not begin 

until the end of the previous growing season, higher 

streamflows during spring runoff most likely resulted 

from increased insolation on the snowpack where the 

canopy had been removed. Continued high streamflows 

in the experimental basin during the growing season 

may be attributed to reduced water demand from the 

reduced forested area.

Another way to evaluate the effect of forest 

clearing is to compare the pairs of flow-duration curves 

from each basin for the pre- and post-treatment periods 

(figs. 6 and 13). The pre-treatment curves indicate that 

the hydrologic response of the experimental basin is 

more rapid than that of the control basin. The 

experimental basin had high peak flows, as shown by 

the high curve in the 0- to 10-percent range (fig. 6).

1,500

rc a: 1,000 -

a. *=. 

OLU 

DC 

Q.

500 -

1985

(PARTIAL YEAR)

1986 1987 

WATER YEAR

1988 1989

EXPLANATION

CONTROL BASIN - PRECIPITATION 

EXPERIMENTAL BASIN - PRECIPITATION

\ \ \ \ \ \ \ \ \

CONTROL BASIN - RUNOFF

EXPERIMENTAL BASIN - RUNOFF

Figure 11. Annual precipitation and annual runoff at the control and experimental basins, Dickey 

Brook Basin, central Massachusetts, water years 1985 through 1989 (data from water year 1985 are 

for February through September only).

24 Effects of Forest Clearing, Fertilization, and Liming on Hydrology and Water Quality, Quabbin Reservoir, Massachusetts
CLEARING FERTILIZATION LIMING

TIMING OF 

TREATMENTS

200

150

DC

. LL)

U- |-

U_ UJ

o 1 100

50

EXPERIMENTAL BASIN

J____I____I

CONTROL BASIN 

EXPERIMENTAL BASIN

JAN APR JUL OCT JAN APR JUL OCT JAN

1985 1986

APR JUL OCT JAN

1987

APR JUL OCT JAN APR JUL OCT

1988 1989

Figure 12. Timing of treatments and monthly runoff from control and experimental basins. Dickey Brook 

Basin, central Massachusetts, February 1985 through September 1989.

After a basin is cleared, peak flows typically increase 

because of reduced interception, increased soil compaction, increased soil moisture, and improved delivery 

efficiency by way of logging road gullies. Increased 

peak flows following clearing were not observed in the 

study; the pattern of the flow-duration curves of both 

basins at high flow was similar in the pre- and posttreatment periods (figs. 6 and 13).

In the middle-flow range, from 20 to 80 percent, 

the flow-duration curve for the experimental basin was 

below that of the control basin in the pre-treatment 

period. In the post-treatment period, both curves were 

shifted upward, but the curve for the experimental basin 

was shifted a greater amount such that it nearly 

coincided with the curve for the control basin. One 

interpretation of this relative shift is that some water in 

the experimental basin that would have left the basin as 

evapotranspiration had the forest not been cleared, left 

the basin as increased streamflow. The relative enhancement of flow duration in the experimental basin in the 

middle-flow range could result from higher sustained 

flows during storm recessions because of reduced 

evapotranspiration and thus increased soil moisture. 

However, the upward shift of the flow-duration curve

for the control basin indicates that wetter conditions 

prevailed in the post-treatment period, thus it is difficult 

to directly compare the two periods.

In the low-flow range, from 80 to 100 percent, flow 

duration in the experimental basin was sharply reduced 

relative to the control basin in the post-treatment period. 

This pattern is opposite to the expectation that the 

decreased water demand would leave additional water 

available to sustain base flow. However, lowest flows 

were measured in both basins during the post-treatment 

period (figs. 6 and 13). At these low flows, forest 

clearing in the headwaters probably has little effect on 

base flow at the outlet. During dry conditions, any 

increased delivery of water to riparian areas from the 

cleared uplands would be readily transpired. The divergence in the curves at low flows probably reflects natural differences in the flow characteristics of the two 

basins under dry conditions. Another consideration is 

that low-flow measurements are more susceptible to 

error than high-flow measurements are because of the 

insensitivity of the stage-discharge relations at natural 

controls used in this study.

Effects of Selective Forest Clearing on Hydrology 25
100

10

55 Q

a: a:

< LLJ t- oz w

^ a: -* uj

a: hLJJ LJJ

a- S

0.1

0.01

CONTROL BASIN (Dickey Brook Tributary Basin) 

EXPERIMENTAL BASIN (Dickey Brook Basin)

10 20 30 40 50 60 70

PERCENTAGE OF TIME FLOW IS EXCEEDED

80 90 100

Figure 13. Flow-duration curves for the control and experimental basins. Dickey Brook 

Basin, central Massachusetts, during the post-treatment period, November 1986 

through September 1989.

Paired regressions of pre- and post-treatment logtransformed daily mean streamflows from both basins 

(fig. 14) indicate a minimal effect of the selective forest 

clearing on the hydrology. An analysis of covariance 

(Helsel and Hirsch, 1992) indicates that the slope of 

the post-treatment regression line was significantly 

greater than the slope of the pre-treatment regression 

line, although the difference in slope was slight 

(table 3). Moreover, the two regression lines intersect, 

indicating that post-treatment streamflow in the 

experimental basin increased at high flows but 

decreased at low flows. The intercepts of the two

regression equations were not significantly different. 

The slope of the post-treatment regression line is 

strongly affected by low flows. As discussed above, 

apparent differences in low-flow magnitude and frequency during the post-treatment period are probably 

unrelated to the forest clearing. The change in slope 

may be an artifact of insufficient low-flow data during 

the pre-treatment phase.

The pre-treatment regression equation was used 

to assess the effect of the forest clearing on water 

yield. Daily runoff from the control basin during the

26 Effects of Forest Clearing, Fertilization, and Liming on Hydrology and Water Quality, Quabbin Reservoir, Massachusetts
-- POST-TREATMENT PERIOD 

y = 1.039 x- 0.020 

r2=0.89

PRE-TREATMENT PERIOD 

y = 0.924 x-0.053 

= 0.87

-1 0 1 

LOG (RUNOFF), CONTROL BASIN, IN MILLIMETERS PER DAY

Figure 14. Scatterplots and regression models of daily mean streamflow data from the preand post-treatment periods at the control and experimental basins. Dickey Brook Basin, 

central Massachusetts. (y, log runoff in experimental basin (Dickey Brook Basin); x, log 

runoff in control basin (Dickey Brook Tributary Basin); i2-, coefficient of determination.)

Table 3. Results of pre- and post-treatment regression analysis and analysis of covariance on daily flows 

at the control and experimental basins near Quabbin Reservoir, central Massachusetts

[Flow in log, millimeter per day. , not applicable]

Regression analysis

Pre-treatment 

Post-treatment

Analysis of covariance

Test for equal slopes 

Test for equal ^-intercepts

Slope

0.924 

1.039

7-value

6.312 

1.233

^-Intercept

-0.053 

-.020

P(T)

0.0000

.2177

Number of 

measurements

615 

1,075

~-

Coefficient of 

determination

(>*)

0.87 

.89

__

Effects of Selective Forest Clearing on Hydrology 27
post-treatment period was used as the independent variable in the pre-treatment regression equation (fig. 14) to 

simulate daily runoff in the experimental basin. The 

simulated daily streamflow represents the streamflow 

that would have occurred had there been no clearing. 

Measured and simulated daily mean flows from the 

experimental basin during the post-treatment period are 

presented as flow-duration curves (fig. 15). The 

measured and simulated flow-duration curves for 

the experimental basin were similar in the middleflow range. The pre-treatment regression markedly 

under-simulated flows in the high-flow range (0- to 30- 

percent flow duration) and over-simulated flows in the 

low-flow range (85 to 100-percent flow duration). 

Although the undersimulation at high flow could be 

interpreted to represent an increase in water yield as a 

result of the clearing, note that the pre-treatment

regression also undersimulates high flows (fig. 14). 

Conversely, the divergence of the two curves at low 

flows may be an artifact of the inadequacy of the regression equation because it is applied to flows in the posttreatment period that were less than flows measured in 

the pre-treatment period.

Because the effect of the selective tree clearing 

on the hydrology was not clearly discernible, Bent 

(1994) specifically reanalyzed the data to detect 

changes in the hydrologic properties most likely to be 

affected by the clearing. The data were analyzed for 

differences in pre- and post-treatment total monthly 

runoff, instantaneous peak runoff, and daily mean base 

flow. No increase in runoff as a result of forest clearing 

was revealed by any of these comparisons.

<

Q

o:

LJJ 

QCO

o:

LJJ

tD

UJ

a:

CL 

UJ 

QS

100

10

0.1

0.01

EXPERIMENTAL BASIN MEASURED 

SIMULATED

10 20 30 40 50 60 70

PERCENTAGE OF TIME FLOW IS EXCEEDED

80 90 100

Figure 15. Flow-duration curves for the experimental basin, Dickey Brook Basin, 

central Massachusetts, during the post-treatment period (November 1986 through 

September 1989) computed from measured and simulated daily mean streamflow.

28 Effects of Forest Clearing, Fertilization, and Liming on Hydrology and Water Quality, Quabbin Reservoir, Massachusetts
In summary, forest clearing caused a slight 

increase in water yield for a few months. Five factors 

were responsible for the limited response:

1. The area of the cut was limited. Although 

increases in water yield are generally proportional to the percentage of basal area harvested, 

results from several studies indicate that a 

threshold equal to about 25 percent of the basal 

area must be cut before effects are observed 

(Hornbeck and others, 1993). In this study, 20 

percent of the basal area was removed during 

the main clearcutting, plus an additional 4 percent from thinning. It irs questionable whether 

thinning is effective in increasing water yield 

because the transpiration of remaining trees 

may increase. Thus, although a slight increase 

in water yield was observed during the year of 

the tree clearing, the cleared area was probably 

too small to cause a lasting effect.

2. The tree clearing was restricted to the headwaters 

of the basin. The effect on water yield depends 

on the position of the cleared area within a basin 

(Hornbeck and others, 1993). Because of the 

greater availability of water in riparian areas as 

compared to upland areas, transpiration tends to 

be greater in riparian forests; thus, clearing of 

riparian areas has a greater effect on water yield 

than does clearing of upland areas (Mrazik and 

others, 1980).

3. The extensive wetlands in the experimental basin 

are areas of high evapotranspiration. Any 

additional water that reaches the riparian zone 

because of increased recharge (or decreased 

evapotranspiration) upslope may be evaporated 

or transpired by riparian trees rather than 

augmenting streamflow. This is particularly true 

during dry periods.

4. Although precipitation during the entire study 

period was above average, the year of the selective clearing and the year that followed were relatively dry, particularly during the growing 

season. Dry conditions are least conducive to 

generating increased flows after clearing

because any excess water that otherwise may 

have run off as streamflow is used to satisfy 

evapotranspiration demand.

5. The cleared area was partially re vegetated with 

grasses, which grew in the second year after 

treatment, and the remaining area was allowed 

to revegetate naturally. Grass cover has a lower 

water demand than forest cover, but evapotranspiration losses from grassland are considerable, 

particularly in the early part of the growing 

season (Rutter, 1968). Maximum water-yield 

increases from forest clearing are obtained 

when revegetation is prevented (Hornbeck and 

others, 1993).

Changes in Ground-Water Levels

The effect of the selective forest clearing in the 

experimental basin on ground-water levels is evident 

for water year 1987. Water levels of wells NLW16 and 

NLW17, which were in the area of selective tree clearing, were noticeably higher than usual during the summer, as is evident from comparison with water-level 

data for the control basin (fig. 16). For water year 1987, 

the summer decline of the water table at wells in the 

experimental basin was the smallest of all five summers 

in the study period, whereas the summer decline at 

wells in the control basin was the largest of all five 

summers. This indicates that the clearing caused a 

significant local decrease in evapotranspiration in the 

vicinity of the two wells.

Changes in Evapotranspiration

Monthly estimates of potential evapotranspiration 

for the experimental and control basins (fig. 17) were 

derived from monthly mean air temperatures computed 

from long-term historical data collected at Amherst, 

Mass. (National Oceanographic and Atmospheric 

Administration, 1985). The evapotranspiration losses 

followed the expected seasonal pattern: large losses in 

the peak of the growing season (approximately May to 

August) and negligible losses in midwinter. Total 

monthly evapotranspiration during the growing season 

ranged from 79 to 132 mm.

Effects of Selective Forest Clearing on Hydrology 29
CLEARING FERTILIZATION LIMING

TIMING OF 

TREATMENTS

LLJ 

LLJ 

LL

^ 4

LU

8Ll_ 

DC

ID 

CO

Q 6

I

LU 

CO

10

12

EXPERIMENTAL BASIN

CONTROL BASIN-Dickey Brook Tributary Basin Well #NLW14

EXPERIMENTAL BASIN-Dickey Brook Basin Well #NLW16

I . , , I . . . I

JAN APR JUL OCT JAN APR JUL OCT JAN APR JUL OCT JAN APR

1985 1986 1987

JUL OCT

1988

JAN APR JUL OCT

1989

Figure 16. Ground-water levels in wells in the control and experimental basins, Dickey Brook Basin, 

central Massachusetts, February 1985 through September 1989.

Annual estimates of the decrease in evapotranspiration in the experimental basin during the posttreatment period (table 4) were computed from the 

regression equation for the pre-treatment daily mean 

flows. As above, observed post-treatment daily mean 

flows from the control basin were used as independent 

data in the pre-treatment regression equation to simulate 

the daily mean flows that would have occurred in the 

experimental basin during the post-treatment period had 

there been no selective clearing. Estimated decreases in 

evapotranspiration for the post-treatment period in the 

experimental basin were calculated by subtracting

observed from simulated daily mean flows. This 

approach is based on a simple water budget in which it 

is assumed that either no loss of ground water from the 

basin or a constant rate of loss. The daily differences 

were summed to compute the annual differences. The 

greatest decrease in evapotranspiration was during 

water year 1987, which coincides with the year of the 

selective clearing. The decrease in evapotranspiration 

for water years 1988 and 1989 was not as great as it was 

in water year 1987, most likely because of the return of 

vegetation in the cleared areas.

30 Effects of Forest Clearing, Fertilization, and Liming on Hydrology and Water Quality, Quabbin Reservoir, Massachusetts
JAN FEB MAR APR MAY JUNE JULY AUG SEPT OCT NOV DEC

Figure 17. Estimated monthly potential 

evapotranspiration for the study area, Dickey 

Brook Basin, central Massachusetts.

Table 4. Estimated annual decrease in evapotranspiration as a result of selective forest clearing 

in the experimental basin, Dickey Brook Basin, 

central Massachusetts

Water year

Estimated annual decrease

in evapotranspiration,

in millimeters

1987

1988

1989

16.26

4.27

8.76

EFFECTS OF SELECTIVE FOREST CLEARING, 

FERTILIZATION, AND LIMING ON 

WATER QUALITY

Changes in Solute Fluxes

Temporal patterns of solute concentrations in the 

two basins were consistently similar throughout the 

study period (fig. 18). This similarity indicates that no 

fundamental shifts or trends in water quality resulted

from selective forest clearing and conversion of cleared 

areas to grass cover. It is especially noteworthy that the 

applications of fertilizer in October 1987 and lime in 

September 1988 had minimal effect on solute concentrations in streamwater. Applications of potassium, 

nitrogen, calcium, and alkalinity in the form of fertilizer 

and lime in the experimental basin constituted very 

large pulse inputs of these solutes (table 5), in some 

cases larger than the entire annual input from precipitation. At most, any trends and episodic rises in solute 

concentration that may be related to the forest clearing 

and treatments are minimal.

Solute-concentration models were developed to 

assess effects of selective forest clearing, fertilization, 

and liming on solute fluxes. The object of applying a 

solute-concentration model is to use data that are 

readily available information such as streamflow (or 

some transformation thereof), day of year, length of 

antecedent dry period as independent variables to 

simulate solute concentrations, for which measurements are relatively infrequent. For the control basin, 

solute-concentration models were developed from 

chemical data from the entire 4V2-year study period. For 

the experimental basin, separate models were developed for each solute for the pre-treatment and posttreatment periods. The post-treatment period in the 

experimental basin was marked by a series of disturbances, including the two periods of forest clearing 

activity and the pulse inputs of fertilizer at the beginning of the second water year and lime at the beginning 

of the third water year. Nevertheless, no systematic 

increases, decreases, or related spikes in solute concentrations were evident as a result of these disturbances, 

so a single model for each solute in the post-treatment 

period was adequate. Solute-concentration models for 

the post-treatment period generally had higher r2 (that 

is, a higher percentage of the variation in solute concentrations was explained by the model parameters) than 

those of the pre-treatment period. The parameters and 

coefficients used in each model formulation are 

summarized in table 6.

Effects of Selective Forest Clearing, Fertilization, and Liming on Water Quality 31
CLEARING FERTILIZATION LIMING

TIMING OF 

TREATMENTS

~i i i i \ r 

EXPERIMENTAL BASIN 

_i i i I i i

CONTROL BASIN OUTLET

JAN APR JUL OCT JAN APR JUL OCT JAN APR JUL OCT JAN APR JUL OCT JAN APR JUL OCT

1985 1986 1987 1988 1989

TIMING OF 

TREATMENTS

400

300

DC 

LLJ

,- b 200

. 

O > 400

<0

0 

S

a: 300

200

100

CLEARING FERTILIZATION LIMING

EXPERIMENTAL BASIN 

i i i I

CONTROL BASIN OUTLET

I 

EXPERIMENTAL BASIN OUTLET

B. "JAN APR JUL OCT JAN APR JUL OCT JAN APR JUL OCT JAN APR JUL OCT JAN APR JUL OCT

1985 1986 1987 1988 1989

Figure 18. Solute concentrations in stream water at the control- and experimental-basin outlets. Dickey 

Brook Basin, central Massachusetts, February 1985 through September 1989.

32 Effects of Forest Clearing, Fertilization, and Liming on Hydrology and Water Quality, Quabbin Reservoir, Massachusetts
CLEARING FERTILIZATION LIMING

TIMING OF 

TREATMENTS

150

I . 1 1 1 . 1

EXPERIMENTAL BASIN

i i i 1 i i i

i

i

ill

ill

&:* *£

\

\ 1 1

1

1 1 1

z

z co

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S Z> 2 o

CO UJ

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O O

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 I I I I I 

CONTROL BASIN OUTLET

EXPERIMENTAL BASIN OUTLET

-i r

JAN APR JUL OCT JAN APR JUL OCT JAN APR JUL OCT JAN APR JUL OCT JAN APR JUL OCT

1985 1986 1987 1988 1989

CLEARING FERTILIZATION LIMING

TIMING OF 

TREATMENTS

150

DC 

LLI

Q cr

O IJ 

Z <

o >

o =>

121 s

Si

100

50

150

100

50

EXPERIMENTAL BASIN

. i , J

I 

CONTROL BASIN OUTLET

I 

EXPERIMENTAL BASIN OUTLET

D. 'JAN APR JUL OCT JAN APR JUL OCT JAN APR JUL OCT JAN APR JUL OCT JAN APR JUL OCT

1985 1986 1987 1988 1989

Figure 18. Continued.

Effects of Selective Forest Clearing, Fertilization, and Liming on Water Quality 33
CLEARING FERTILIZATION LIMING

TIMING OF 

TREATMENTS

50

1 1 , 1

EXPERIMENTAL BASIN

i i i 1 i i i

1

i

HI

III

11

1

1 i i

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Z £

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30

20

10

0

50

40

30

^ 20

10

I

CONTROL BASIN OUTLET

EXPERIMENTAL BASIN OUTLET

E. JAN APR JUL OCT

1985

JAN APR JUL 

1986

OCT JAN APR JUL OCT JAN

1987

APR JUL OCT

1988

JAN APR JUL

1989

OCT

CLEARING FERTILIZATION LIMING

TIMING OF 

TREATMENTS

400

300

DC

Ml

b 200 _i

$ 100

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< §

DC 

O

F.

0 

4°0

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200

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CONTROL BASIN OUTLET

\ 

EXPERIMENTAL BASIN OUTLET

JAN APR JUL OCT JAN APR JUL OCT JAN APR JUL OCT JAN APR JUL OCT JAN APR JUL OCT

1985 1986 1987 1988 1989

Figure 18. Continued.

34 Effects of Forest Clearing, Fertilization, and Liming on Hydrology and Water Quality, Quabbin Reservoir, Massachusetts
CLEARING FERTILIZATION LIMING

TIMING OF 

TREATMENTS

400

CO

8°

LU

t?iCO §

G.

1 1 1 I 1 I I

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i i i 1 i i i

:^:::S:W:-:¥:^:^::::i;S:: $;^ 1 

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300

200

100

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400

300

200

100

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EXPERIMENTAL BASIN OUTLET

JAN APR JUL OCT JAN APR JUL OCT JAN APR JUL OCT JAN APR JUL OCT JAN APR JUL OCT

1985 1986 1987 1988 1989

TIMING OF 

TREATMENTS

15

EXPERIMENTAL BASIN

i . i I

: CONTROL BASIN OUTLET

a: LU

10

 oc ,-

I LU 5

< 0.

CC

LU

co

LU

O > 15

o 5

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o

10

CLEARING FERTILIZATION

EXPERIMENTAL BASIN OUTLET

LIMING

H. JAN APR JUL OCT JAN APR JUL OCT JAN APR JUL OCT JAN APR JUL OCT JAN APR JUL OCT

1985 1986 1987 1988 1989

Figure 18. Continued.

Effects of Selective Forest Clearing, Fertilization, and Liming on Water Quality 35
CLEARING FERTILIZATION LIMING

TIMING OF 

TREATMENTS

100

80

60

40

20

0

1 1 1 1 1 1 1

EXPERIMENTAL BASIN

i i i 1 i i i

i HI

III ili

1 ' ' 

1 I I

1

1 I I

I 

_ CONTROL BASIN OUTLET

cr

LU

z b o -1

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< LU

cr Qzf?

UJ Z 

O LU

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u R 

s 2

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1985 1986 1987 1988 1989

CLEARING FERTILIZATION LIMING

TIMING OF 

TREATMENTS

300

200

. cr

z uj

Q t 100

LU

1 1 1

EXPERIMENTAL BASIN

1 i i i

i

i

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HI

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1

1 i i

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0

o 300 

81

< CE

51 200

CO -7.

100

I

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EXPERIMENTAL BASIN OUTLET

JAN APR JUL OCT JAN APR JUL OCT JAN APR JUL OCT JAN APR JUL OCT JAN APR JUL OCT

1985 1986 1987 1988 1989

Figure 18. Continued.

36 Effects of Forest Clearing, Fertilization, and Liming on Hydrology and Water Quality, Quabbin Reservoir, Massachusetts
CLEARING FERTILIZATION LIMING

TIMING OF 

TREATMENTS

20 z" 

O

t 15

LU E= O -1

Z DC

O LU

O DZ W

0 Z

CD m

DC ^

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< LJJ

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I 

CONTROL BASIN OUTLET

EXPERIMENTAL BASIN OUTLET

JAN APR JUL

1985

OCT JAN APR JUL

1986

OCT JAN APR JUL OCT JAN

1987

APR JUL OCT

1988

JAN APR JUL

1989

OCT

Figure 18. Continued,

Table 5. Fertilizer and lime inputs to experimental basin, 

normalized to basin area, Dickey Brook Basin, central 

Massachusetts

[Quantity in equivalents per hectare]

Source

Fertilizer 

Lime

Date of 

application

September 1987 

September 1988

Constituent

Nitrogen (N) 

Phosphorus (P) 

Potassium (K) 

Calcium (Ca) 

Bicarbonate (HCO3)

Quantity

65.52 

19.56 

9.74 

2,231 

2,231

Effects of Selective Forest Clearing, Fertilization, and Liming on Water Quality 37
fc 3 fV Q

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38 Effects of Forest Clearing, Fertilization, and Uming on Hydrology and Water Quality, Quabbin Reservoir, Massachusetts
O

8

Table 6. Parameters and coefficients of models used to estimate solute fluxes near Quabbin Reservoir, centra

-Continued

Models used

Constituent

Seasonal

Flow 

model

Averaging R 

period

Model coefficients

Cl

CONTROL BASIN, PRE- AND POST-TREATMENT

Al

PERIOD,

(Number of cases

Hydrogen ion

Calcium

Magnesium

Sodium

Potassium

Alkalinity

Sulfate

Chloride

Silica

Nitrate

No

Yes

Yes

Yes

Yes

Yes

Yes

Yes

Yes

1

3

3

3

None

3

3

3

1

No Model

Inst.

Inst. 1.8

Inst. .7

1 day .6

..

5 day 1.6

15 days 3

Inst. 4

30 days

0.124

139.6

47.96

61.76

15.86

71.72

177.6

31.51

91.95

-

-17.5

-5.61

-4.08

0

-10.8

0

-3.85

0

A2 C2

Model statisti

Standard 

error

r

FEBRUARY 1985 THROUGH SEPTEM

is 75)

--

-6.81

0

0

4.48

-29.3

33.37

5.75

37.3

0.0243

137.62

34.73

41.57

--

210.79

-101.5

-8.81

9.06

0.0955

16.96

4.645

6.843

3.031

33.88

23.94

5.377

23.07

58

83

84

69

50

72

62

45

59

O 

Q.

i

0 

o
Five generalizations can be made from a comparison of annual fluxes of all solutes in both basins 

(fig. 19):

1. Chemical loads in precipitation in each basin were 

nearly identical. The minor differences in input 

loads for a solute generally were inconsequential relative to the higher loads in streamwater 

for most solutes. Thus, a single input value was 

used in each of the bar graphs for annual flux.

2. Annual solute output fluxes were similar between 

basins during each year of the study, despite the 

disturbances in the experimental basin.

3. In water year 1989, output fluxes in both basins 

were markedly higher than in any other water 

year during the study, because of generally 

wetter conditions in that year.

4. Solute fluxes in streamwater in the control basin 

were slightly higher than solute outputs in the 

experimental basin, following the differences in 

concentration mentioned above.

5. Solute fluxes increased in the experimental basin 

relative to those in the control basin in water 

year 1987, the year in which most of the forest 

clearing took place. However, these relative 

increases were almost directly proportional to 

the increase in water yield (fig. 11).

The similarity of temporal variations among solute 

fluxes is a logical consequence of the linkage between 

solute flux and water flux. This correspondence is 

apparent in the similarity between the monthly runoff 

(fig. 12) and the monthly solute fluxes (fig. 20). The 

higher annual solute fluxes in the experimental basin 

relative to the control basin in water year 1987 were 

attributed predominantly to higher water yield in that 

year. In particular, higher flows in March and April 

accounted for most of the increase in solute flux at the 

experimental basin in water year 1987. The major 

differences in the model structure used to determine 

the chemographs for specific solutes indicate that 

various combinations of seasonal and hydrologic 

characteristics control solute flux. However, the strong

correlation between chemical flux and water flux 

indicates that water flux is the overriding control on 

solute flux from the basins. Thus, the concentrations of 

most solutes did not change as a result of the forest 

clearing.

If the concentration of a solute does not change but 

water yield increases, the increase in solute flux will be 

directly proportional to the increase in water yield. The 

changes in solute flux resulting from the forest clearing 

independent of changes in water yield were evaluated 

by normalizing annual solute fluxes (fig. 18) to annual 

runoff (fig. 11). Next, the ratio of runoff-normalized 

annual solute fluxes in the experimental basin to runoffnormalized annual solute fluxes in the control basin was 

computed for each year of the study (table 7). Variations 

in this ratio from year to year for a given solute indicate 

that some factor other than water yield affected solute 

flux.

Runoff-normalized annual flux ratios (table 7) for 

calcium, sodium, potassium, and sulfate were relatively 

constant from year to year. Fluxes of these solutes were 

most closely linked to water yield. Magnesium, nitrate, 

and silica fluxes appeared to have been affected by the 

clearing in 1987, but each of these solutes also had a 

similar change in the ratio in 1989, which was the 

wettest year of the study. Compared to the other years of 

the study, normalized ratios in water years 1987 and 

1989 were higher for magnesium (by 5-10 percent), and 

lower for nitrate (by 30-40 percent) and silica (by 12-15 

percent). Because 1987 and 1989 were the 2 years of 

greatest water yield in the experimental basin, the 

similar ratios of these solutes in these two years could 

be linked either to biogeochemical effects of the 

clearing that are manifested under wet conditions or 

simply to changes in basin hydrochemistry at higher 

flows. Alkalinity flux in 1987 increased by 

approximately 10 percent more than that expected from 

water flux alone, but no similar effect was observed in 

1989.

40 Effects of Forest Clearing, Fertilization, and Liming on Hydrology and Water Quality, Quabbin Reservoir, Massachusetts
DGEN IONFLUX, ENTS PERHECTA A 0CT>§ g

g £ 200 £§

z °

A

-

111

111

I

ill 

llli

lllll

III

llli

Hill

llli

ill!! 

ill!

ill!

Ill

-

-

1985 1986 1987 1988 1989

(PARTIAL YEAR) WATER YEAR

1,200

1,000

800

600

400

200

B.

1985

(PARTIAL YEAR)

1986 1987 

WATER YEAR

1988 1989

. O

:$ I

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LLJ Z

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LiJ

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400

300

200

100

0

c.

1985

(PARTIAL YEAR)

1986 1987 

WATER YEAR

1988 1989

EXPLANATION

PRECIPITATION

- INPUT FLUX

CONTROL BASIN

- OUTPUT FLUX

EXPERIMENTAL BASIN

- OUTPUT FLUX

Figure 19. Annual input and output fluxes at the control and experimental outlets, 

Dickey Brook Basin, central Massachusetts, water years 1985 through 1989 (data for 

water year 1985 are from February through September only).

Effects of Selective Forest Clearing, Fertilization, and Liming on Water Quality 41
sr 

o

Tl

I 

O

Q 

g.

(O 

O

9

a

i 

I

i

I

I

(Q 

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CD 

Q.

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IN EQUIVALENTS PER HECTARE

IND

O

00

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O O 

00

00 O

O O

O O

Im --.

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m

//////// 

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IN EQUIVALENTS PER HECTARE

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IN EQUIVALENTS PER HECTARE

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li.,01

Im -^

CHLORIDE FLUX, 

IN EQUIVALENTS PER HECTARE

-^ ro co

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3).

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m

5

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IN EQUIVALENTS PER HECTARE

-* ro co ^

o o o o

o o o o o

I

m

m
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TIMING OF 

TREATMENTS

1.0

0.8

x o

Z> UJ

^ or 0.6 ^ m O Q.

EXPERIMENTAL BASIN

.

LU

0.4

UJ

1 0.2

o CONTROL BASIN

EXPERIMENTAL BASIN

A.

00

JAN APR JUL OCT JAN APR JUL OCT JAN APR JUL OCT JAN APR JUL OCT JAN APR JUL OCT

1985 1986 1987 1988 1989

CLEARING FERTILIZATION LIMING

TIMING OF 

TREATMENTS

250

UJ 200

O

UJ

DC 150

UJ 

O. 

CO

-J 100

<,

a

UJ

1 50

EXPERIMENTAL BASIN

CONTROL BASIN 

EXPERIMENTAL BASIN

B.

JAN APR JUL OCT JAN APR JUL OCT JAN APR JUL OCT JAN APR JUL OCT JAN APR JUL OCT

1985 1986 1987 1988 1989

Figure 20. Timing of treatments in experimental basin and monthly solute fluxes in streamwater at the 

control- and experimental-basin outlets, Dickey Brook Basin, central Massachusetts, February 1985 

through September 1989,

44 Effects of Forest Clearing, Fertilization, and Liming on Hydrology and Water Quality, Quabbin Reservoir, Massachusetts
CLEARING FERTILIZATION LIMING

TIMING OF 

TREATMENTS

100

80

. o

X LU

ill oc 60 ": LU

S D_

2 co 

Ez

£ % 40

O

LU

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, , , 1

EXPERIMENTAL BASIN

i i i 1 i i i

::::33S::£&3&:W:WW3S :::::::::|$::i:::::::;:::;^::::^::^:::$::;:>

1 

1

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111

mm 1 I I 1 1 I I

CONTROL BASIN 

EXPERIMENTAL BASIN

c.

JAN APR JUL OCT JAN APR JUL OCT JAN APR JUL OCT JAN APR JUL OCT JAN APR JUL OCT

1985 1986 1987 1988 1989

TIMING OF 

TREATMENTS

120

EXPERIMENTAL BASIN

100

o

LU 80

oc

_l LU LL D_

Q LU

O -J

CO <

60

5 40

o

LU

z

20

CLEARING FERTILIZATION LIMING

D.

JAN APR JUL OCT JAN APR JUL OCT JAN APR JUL OCT JAN APR JUL OCT JAN APR JUL OCT

1985 1986 1987 1988 1989

Figure 20. Continued.

Effects of Selective Forest Clearing, Fertilization, and Liming on Water Quality 45
CLEARING FERTILIZATION LIMING

TIMING OF 

TREATMENTS

40

EXPERIMENTAL BASIN

o 

x'jjj

of £

co

30

20on 

CO

5

10

J____I____L

T 

CONTROL BASIN

EXPERIMENTAL BASIN

E.

JAN APR JUL OCT JAN APR JUL OCT JAN APR JUL OCT JAN APR JUL OCT JAN APR JUL OCT

1985 1986 1987 1988 1989

TIMING OF 

TREATMENTS

200

LU 

DC

< 150

EXPERIMENTAL BASIN

I I I

o

s/ LJJ

3 =

-J CC

U- LLI

>- d.

100

< ^

2 50

0

CLEARING FERTILIZATION LIMING

i i J____L

I 

CONTROL BASIN

EXPERIMENTAL BASIN

F.

JAN APR JUL OCT JAN APR JUL OCT JAN APR JUL OCT JAN APR JUL OCT JAN APR JUL OCT

1985 1986 1987 1988 1989

Figure 20. Continued.

46 Effects of Forest Clearing, Fertilization, and Liming on Hydrology and Water Quality, Quabbin Reservoir, Massachusetts
CLEARING FERTILIZATION LIMING

TIMING OF 

TREATMENTS

300

uj 250

DC 

g

200

UJ

150

5 100 

OUJ

50

EXPERIMENTAL BASIN

I 

CONTROL BASIN

EXPERIMENTAL BASIN

G.

JAN APR JUL OCT JAN APR JUL OCT JAN APR JUL OCT JAN APR JUL OCT JAN APR JUL OCT

1985 1986 1987 1988 1989

CLEARING FERTILIZATION LIMING

TIMING OF 

TREATMENTS EXPERIMENTAL BASIN

0 CONTROL BASIN

EXPERIMENTAL BASIN

H.

JAN APR JUL OCT JAN APR JUL OCT JAN APR JUL OCT JAN APR JUL OCT JAN APR JUL OCT

1985 1986 1987 1988 1989

Figure 20. Continued.

Effects of Selective Forest Clearing, Fertilization, and Liming on Water Quality 47
CLEARING FERTILIZATION LIMING

TIMING OF 

TREATMENTS

50

40

I I 1 1 1

EXPERIMENTAL BASIN

1,,,

'

i

i

11

i

1 i i

1

1 i i

o

. LLJ

. LI. LU LU aQ £. £ = O LU 5* 3

o >

ID

O

LU

30

20

? 10

I 

CONTROL BASIN

EXPERIMENTAL BASIN

JAN APR JUL OCT JAN APR JUL OCT JAN APR JUL OCT JAN APR JUL OCT JAN APR JUL OCT

1985 1986 1987 1988 1989

CLEARING FERTILIZATION LIMING

TIMING OF 

TREATMENTS

200

r i i | 

EXPERIMENTAL BASIN

LU 

CC

150

100

O

LU

C/5

2 50

CONTROL BASIN 

EXPERIMENTAL BASIN

JAN APR JUL OCT JAN APR JUL OCT JAN APR JUL OCT JAN APR JUL OCT JAN APR JUL OCT

1985 1986 1987 1988 1989

Figure 20. Continued.

48 Effects of Forest Clearing, Fertilization, and Liming on Hydrology and Water Quality, Quabbin Reservoir, Massachusetts
Table 7. Ratios of runoff-normalized annual solute fluxes in the experimental basin to runoff-normalized 

annual solute fluxes in the control basin. Dickey Brook Basin, central Massachusetts

[Water year 1985, data from February through September only]

Water Hydrogen _ , . ,. . _ ,. _ 4 . A11 ,. . Sulfate, ~,U1 ., c .r xr. . - Calcium Magnesium Sodium Potassium Alkalinity ,. , , Chloride Silica Nitrate

year ion & J dissolved

1985

1986

1987

1988

1989

1.42

1.77

1.79

1.47

1.38

0.80

.81

.83

.82

.86

0.84

.89

.93

.85

.94

0.94

.97

.99

1.00

1.00

0.87

.79

.83

.89

.93

0.71

.78

.84

.75

.75

0.94

.90

.89

.92

.87

0.91

1.07

1.13

1.15

1.21

0.92

.94

.80

.98

.81

1.67

1.50

.92

1.32

.86

The changes noted above are small compared to 

the large effects documented in other studies, which 

generally involved a greater percentage of cleared area. 

For example, Martin and Pierce (1980) found that 

nitrate concentrations increased by more than a factor of 

10 after clearcutting. In the present study, nitrate concentrations actually decreased after selective clearing. 

The small annual fluctuations in solute flux observed at 

the experimental basin are probably within the range of 

natural variations; no definitive changes can be related 

to forest clearing, fertilization, and liming.

Forest clearing has the potential to release 

nutrients to streamflow. Hornbeck and others (1986) 

summarized the mechanisms by which nutrient release 

occurs as (1) decomposition of remaining dead tree 

material, enhanced by increased temperature and light 

(see also Patric and Reinhart, 1971), (2) decreased 

nutrient uptake by vegetation, (3) increased nitrification; that is, conversion of organic nitrogen to nitrate as 

organic matter mineralizes, and (4) increased weathering and cation leaching associated with the acidifying 

effect of nitrification (see also Lawrence and others, 

1987). Acidification of soil after forest clearing also has 

the effect of increasing sulfate adsorption, so sulfate 

concentrations in streams may decrease (Nodvin 

and others, 1986). All of these changes reverse 

rapidly within a few years if the cleared area is 

allowed to regenerate; a young canopy has a high 

nutrient demand (Bormann and Likens, 1979).

Despite the expectation of increased nutrient flux, 

several other studies have found little change in streamwater chemistry as a result of forest clearing. Martin 

and others (1984) examined 6 totally cleared and 32

partially cleared basins in New England. For most 

basins, and particularly for those that were not completely clearcut, changes in stream chemistry were 

within the range of natural variations among streams. 

Likewise, Corbett and others (1978) and Aubertin and 

Patric (1974) found only minimal effects on stream 

chemistry from cleared basins in other areas of the eastern United States. Somewhat greater effects were 

observed at Hubbard Brook, N.H., where some of the 

most comprehensive studies have been done. Significant increases in nitrate, calcium, and potassium were 

observed within the first 3 years after clearcutting at 

Hubbard Brook (Pierce and others, 1972; Hombeck and 

others, 1975; Martin and Pierce, 1980).

The relative lack of change in streamwater chemistry after forest clearing in the experimental basin is 

consistent with the other studies mentioned above 

where the basins were not completely clearcut. The lack 

of response of the nutrients calcium and potassium 

indicates that any of these nutrients that may have been 

released by decomposition were either sequestered by 

the new-grown grass, or stored in the soil because 

runoff was insufficient to transport them to the stream. 

An acidification effect (Nodvin and others, 1986; 

Lawrence and others, 1987) also seems not to be a likely 

cause; alkalinity was the lone solute that increased (relative to the increase in water yield) in the year of the 

clearing only (table 7). The increase in alkalinity is consistent with the decrease in nitrate in that year. Nitrate is 

generally more readily affected by forest clearing than 

other solutes, and the effect is invariably an increase in 

flux due to nitrification (Martin and Pierce, 1980; 

Vitousek, 1981; Lawrence and others, 1987). The

Effects of Selective Forest Clearing, Fertilization, and Uming on Water Quality 49
observed decrease in nitrate (relative to water flux), particularly in light of further additions in the form of fertilizer in late 1987, underscores the lack of effect on 

stream chemistry from the selected forest clearing at the 

experimental basin.

The only apparent effect on chemical fluxes from 

the forest clearing is associated with increased water 

flux in the first year of the clearing, as seen by comparing monthly hydrologic flux (fig. 12) and monthly 

solute fluxes (fig. 20) in the control and experimental 

basins. The pattern in monthly fluxes for calcium 

(fig. 207?) typifies the pattern for most constituents. In 

each month from the first full month of data collection 

in March 1985 through May 1986, and again in each 

month from October 1987 until the end of the study in 

September 1989, output flux of calcium was higher at 

the control basin than that at the experimental basin, 

generally by more than 10 percent. During water year 

1987, however, monthly calcium fluxes in the two 

basins were nearly equivalent. Although this change in 

pattern started before the forest clearing, more significance is given to the anomalously high calcium flux in 

the experimental basin beginning during the spring 

1987 runoff and extending through summer 1987. In 

March and April 1987, calcium flux in the experimental 

basin substantially exceeded that in the control basin. 

The timing and magnitude of this relative increase in 

calcium flux is in phase with the relative increase in 

water flux at the experimental basin.

The effect appeared to end abruptly in October 

1987. After this time, the pattern of greater calcium flux 

in the control basin was reestablished; calcium flux in 

the control basin exceeded that in the experimental 

basin by 30 percent in water year 1988 and 23 percent 

in water year 1989. These percentages underscore the 

absence of any observed effect of the lime application in 

September 1988. Clearly, liming had a negligible effect 

on streamwater chemistry at the outlet of the basin 

during the first year after application.

Magnesium flux (fig. 20C) followed a pattern 

similar to calcium flux, except for a more substantial 

spike in magnesium flux in the experimental basin in 

March 1987. Sodium flux (fig. 207)) also increased 

sharply in March 1987, but, in general, the monthly 

sodium fluxes in the two basins followed a similar pattern more than did calcium and magnesium fluxes. 

Potassium flux (fig. 20£) was less predictable month to 

month than the other base cations, although on an 

annual basis it followed a similar pattern. No sustained 

increase in potassium flux at the experimental basin was

observed as a result of the fertilizer application in October 1987. A few high potassium concentrations in 

summer 1988 and winter 1989 may be attributed to 

potassium inputs in fertilizer, but in general no effect 

was evident. Likewise, neither the flux nor stream 

concentration of nitrate seemed to increase in response 

to fertilizer application (fig. 2077).

Chloride differed from that of other solutes in that 

chloride flux was consistently higher at the experimental basin than at the control basin (fig. 207). The disparity was greatest during water year 1987. Because 

chloride is derived primarily from precipitation and 

takes limited part in biogeochemical reactions, the chloride flux in the two basins was expected to be similar. 

The consistently higher chloride flux in the experimental basin is not understood. Although minor differences 

resulted in flux, two separate episodes of unusually high 

chloride concentrations nearly double the typical 

chloride maximum in fall occurred in the experimental basin (fig. 187). The high chloride concentrations 

occurred in October of 1985 and again in October of 

1988. At those times only a slight increase in chloride 

concentration was observed in the control basin. The 

reason why chloride export exceeds chloride input by 

nearly a factor of 2 is unclear. One possibility is that 

road salt aerosols enter the basins as dry deposition, 

which was not measured in this study. Mineralogical 

sources of chloride are rare, and none are known in the 

Quabbin area (Rittmaster and Shanley, 1995).

The pattern of monthly sulfate flux (fig. 20G) was 

similar to that of the base cations; sulfate flux was usually greater in the control basin, except for water year 

1987, when fluxes were nearly equal in each basin. The 

disproportionately greater flux in the control basin in 

water year 1989 was somewhat more pronounced for 

sulfate than for the other constituents. Other studies of 

clearcuts (for example, Nodvin and others, 1986) have 

documented decreased flux of sulfate because increased 

nitrification resulting from the cut promotes soil 

acidification, which increases the potential for sulfate 

adsorption. The changes in sulfate flux observed in 

water year 1989 are too subtle to invoke such an 

explanation particularly in light of the apparent lack 

of effect on any of the other solutes. Moreover, the 

liming in water year 1989 would almost certainly 

negate any modest soil acidification that may have 

resulted from the cutting.

Alkalinity flux (fig. 2QF) closely paralleled basecation flux; fluxes were nearly identical in each basin 

from June 1986 through September 1987. Similar to

50 Effects of Forest Clearing, Fertilization, and Liming on Hydrology and Water Quality, Quabbin Reservoir, Massachusetts
calcium flux, the alkalinity flux was greater in the 

control basin than in the experimental basin in water 

year 1989, an indication that none of the applied lime 

was transported to streamwater. The pattern of silica 

flux paralleled that of calcium and magnesium fluxes. 

Dissolved silica results primarily from mineral weathering; the similarity of these three patterns indicates that 

mineral weathering is a common source for silica, 

calcium, and magnesium.

Changes in Sediment Transport

Suspended-sediment concentration was determined for samples collected occasionally during the 

pre- and post-treatment periods at the outlets of the control and experimental basins and during the posttreatment period at the headwaters site in the experimental basin (fig. 21). Samples were collected on the 

same day at the outlets of the experimental and control 

basins. Suspended-sediment concentrations generally 

increased as stream discharge increased. Results from 

the 36 samples at each site indicate that rates of physical 

weathering are higher in the control basin than those in 

the experimental basin. Physical weathering rates in 

basins can differ because of differences in geology and 

soils. Higher background concentrations of suspended 

sediment in the control basin were attributed to higher 

basin relief in the control basin. Interpretation of 

suspended-sediment concentrations at high flow was 

tentative because sampling was limited; generally only 

1-2 samples were collected per site during high-flow 

periods. Based on these limited data, the concentrations 

of suspended sediments in the experimental basin were 

higher than those in the control basin during high flow 

in April 1987, which was 6 months after the cutting 

began. However, suspended-sediment concentrations 

were higher in the control basin during storms in May 

1988 and May 1989.

At the headwaters stream gage near the area of 

most of the forest clearing in the experimental basin, 

suspended-sediment concentration increased sharply 

during the clearing operations in late 1986 and early 

1987 (fig. 21). Concentrations in two samples in April 

1987 were 90 and 140 mg/L, considerably higher than 

peak concentrations at the basin outlets. However, 

suspended-sediment concentrations for the following 

years at the headwater site were reduced to levels 

similar to those at the basin outlets. The conversion of 

the cleared area to grassland, which took place in the 

same year as the clearing, stabilized the disturbance and 

likely slowed erosion rates.

Changes in Biogeochemical Controls on 

Water Quality

The close similarity of the hydrology and streamwater chemistry of the two basins makes possible a 

common discussion of their biogeochemistry before 

basin disturbance. In general terms, the differences 

between solute inputs and outputs in the two basins 

(fig. 19) are typical of those found in undisturbed forested basins in the northeastern United States (Likens 

and others, 1977). Precipitation is acidic, characterized 

by a weak mixture of nitric and sulfuric acid with minor 

amounts of chloride and base cations. Hydrogen ion and 

nitrate are mostly retained in the basins. In contrast, 

their net export is small. Base cations (calcium, magnesium, sodium, potassium), silica, and alkalinity, which 

have minor or negligible inputs in precipitation, have a 

high net export primarily as a result of weathering. 

Chloride and sulfate have a net export that is intermediate between those of the constituents previously mentioned above. Sources of chloride and sulfate are 

thought to be minor in the basin, and each is relatively 

conservative; thus, outputs should reflect inputs. In the 

eastern United States, approximately half of sulfate 

inputs are in the form of dry deposition (Lindberg and 

Garten, 1988), which was not measured in this study. 

Thus, the combined input of sulfate (wet plus dry) probably exceeds outputs. This conclusion is consistent with 

the likelihood that some sulfate is retained in the basins 

through sulfate reduction in wetlands and (or) sulfate 

adsorption in basin soils. The excess chloride export is 

less easily explained, but one possibility as mentioned 

previously, is dry deposition of sodium chloride aerosol 

derived from locally applied road salt.

Chemistry of streamwater leaving the two basins 

reflects weathering of the silicate minerals in the local 

bedrock and till. Superimposed on the geochemical 

processes of weathering and ion exchange are 

biogeochemical processes such as nutrient cycling and 

sulfate reduction. The importance of the biological 

component is indicated in that most of the soluteconcentration models had seasonal components 

(table 6). Although discharge, as expected, generally 

was the most important parameter affecting solute concentrations, variation in concentration of several solutes 

also was attributable to seasonal factors. For example, 

in the post-treatment period in the experimental basin, 

the model for sulfate, which generally is very sensitive 

to changes in discharge, had no discharge term at all; 

variation in sulfate concentration was explained by a 

seasonal model alone (^=0.63).

Effects of Selective Forest Clearing, Fertilization, and Liming on Water Quality 51
CLEARING FERTILIZATION LIMING

TIMING OF 

TREATMENTS

150

100

cc

LLJ

IJ 50 

cc

UJ 

Q.

1 °

g 

I

-

Q 100

cc

z 

o 50

SEDIMENT COh ^JDED 

Ul

o

£ 100 

CO

CO

50

n

EXPERIMENTAL BASIN !J I

CONTROL BASIN OUTLET

p

: I :

:

| | R f D/ \

I ' ' ' I ^ ' ' I ' ' ' I

EXPERIMENTAL BASIN HEADWATERS GAGE

i \

-

" . . . , i^ L^rrfp--- __ D JV '

I ' ' ' I ' ' ' I ' 

EXPERIMENTAL BASIN OUTLET

-

-

f I

^Jcacb........-^.-. I i L lm I~oo6 , , kftnfltJilflcJ T~~+-o^rrfiSD 

JAN APR JUL OCT JAN APR JUL OCT JAN APR JUL OCT JAN APR JUL OCT JAN APR JUL OCT

1985 1986 1987 1988 1989

Figure 21. Tinning of treatments and concentrations of suspended sediment at the control-basin 

outlet, experimental-basin headwaters gage, and experimental-basin outlet. Dickey Brook Basin, 

central Massachusetts, February 1985 through September 1989.

52 Effects of Forest Clearing, Fertilization, and Liming on Hydrology and Water Quality, Quabbin Reservoir, Massachusetts
For solutes that have seasonal controls, the seasonality is represented in the concentration model by a sine 

wave of period one year. The phase of the sine wave 

timing (that is, of the maximum and minimum) offers 

additional clues about the biogeochemical processes 

that affect solute concentrations, and the amplitude 

indicates the relative importance of the seasonal control. For example, a minimum sulfate concentration 

near July 12 was simulated with the post-treatment 

seasonal sulfate model, consistent with the time of 

maximum sulfate reduction which commonly peaks 

during the warmest time of the year. Sulfate adsorption 

is ruled out as an explanation of the seasonal behavior. 

Sulfate adsorption would be as strong during winter 

base flow as during summer base flow (Shanley and 

Peters, 1993); moreover, a model that accounts for sulfate adsorption also would need a flow component to 

explain increases in sulfate that typically occur during 

storm runoff, when water following shallow flow paths 

bypasses the mineral soils where adsorption takes place.

The behavior of the base cations calcium, magnesium, and sodium in the pre- and post-treatment periods 

in the experimental basin indicates that their concentrations are affected by a simple dilution mechanism. No 

seasonal component was utilized in model simulation of 

base cations, and concentration was inversely related to 

discharge. This model form indicates that these solutes 

are contributed primarily by weathering. Solute concentrations are higher during periods of base flow because 

the hydrograph during those periods is dominated by 

ground water, which, compared to storm runoff, has 

acquired more weathering products along its relatively 

longer flowpaths and during its greater contact time 

with mineral surfaces in the regolith. Storm runoff is 

low in base cations and causes dilution of base-flow 

cation concentrations. Thus, the concentration models 

for these solutes have flow components only; no 

seasonal biogeochemical processes are important 

enough to call for seasonal components to the models. 

In the control basin, concentration models for the base 

cations had seasonal components, but only of minor 

significance. For example, the model for sodium in the 

control basin had a seasonal component, but its amplitude was only 4 jaeq/L. Comparison of this amplitude to

the model constant (analogous to the ^-intercept in a 

simple regression) of 62 jneq/L indicates that the 

seasonal component is minor.

Alkalinity behaves similarly to base cations, 

consistent with their common source in mineral 

weathering. However, the relative increase in alkalinity 

in summer is greater than that of base-cation 

concentrations, indicative of an additional seasonal 

control. The seasonal control on alkalinity is reflected in 

the alkalinity concentration models for the control 

basin, the pre-treatment experimental basin, and the 

post-treatment experimental basin. All alkalinity 

models have seasonal components that peak in late 

spring or summer. The process responsible is most 

likely sulfate reduction, which increases alkalinity as 

sulfate decreases. The seasonal components for sulfate 

and alkalinity are approximately 6 months out of phase 

in all three models, lending support to this explanation.

Model structures for silica, chloride, and nitrate 

concentrations also have seasonal components indicative of biological interactions. Nitrate in the experimental basin is the most straightforward to interpret, having 

a peak in the seasonal sine wave in February and thus a 

minimum in August. This pattern is consistent with 

maximum biological uptake of nitrate in late summer, 

when nitrate concentrations in streamwater decrease to 

near zero. The amount of nitrate in streamwater at the 

experimental basin is only a minor fraction of the 

amount of nitrate entering the basin in precipitation; 

thus, biological uptake affects nitrate flux all year. An 

interesting aspect of the nitrate models is that using 

longer-term average flow (for the post-treatment period, 

45 days) resulted in more accurate simulations of concentration than instantaneous flow, an indication of the 

importance of antecedent conditions to nitrate flux. 

During dry periods, nitrate concentrations build up in 

the soil because of nitrification the conversion of 

organic nitrogen to inorganic nitrate. This nitrate is 

readily flushed to streamwater by storms. Nitrate 

concentration is inversely related to stream discharge. 

Thus, in generally wet periods (as indicated by high 45- 

day discharge), little nitrate buildup occurs in the soil, 

and nitrate concentrations in streamwater are kept low.

Effects of Selective Forest Clearing, Fertilization, and Liming on Water Quality 53
Silica and chloride have minimal interaction with 

the biota, so the strong seasonal components in the concentration models are unexpected. Silica may be incorporated in diatom blooms, consistent with its seasonal 

minimum in June or July. Chloride, which also is at a 

minimum at this time, may likewise be incorporated 

into biota. Despite the common assumption that 

chloride is conservative, Peters (1989) has presented 

evidence that it is taken up by trees.

Concentrations of potassium are controlled by several processes, both geochemical and biological, and 

potassium concentration is thus less predictable (Likens 

and others, 1977). This multiplicity of controls was 

reflected in lower r2 values for the potassium models. A 

significant percentage of the variance in potassium concentration for the post-treatment period in the experimental basin could not be simulated in the models. In 

the control basin, the model has a seasonal component 

only. Peak potassium concentration from the model 

occurred at January 1, consistent with summer biological uptake of potassium. The experimental basin pretreatment model likewise had a seasonal peak for potassium in early winter and also had a discharge term with 

positive slope (increasing concentration with increasing 

flow). Positive concentration-discharge relations are not 

uncommon for potassium (Likens and others, 1977). A 

considerable amount of potassium is associated with 

organic matter in upper soil horizons. This source 

contributes potassium to streamwater, as storm runoff 

follows shallow flow paths and contacts these horizons 

and (or) ground water rises into these zones.

Hydrogen ion concentration had a minor seasonal 

component in two of the three models, but in general it 

was controlled by discharge. Hydrogen ion concentrations increased with increasing discharge, probably for 

the same reason as did potassium. Higher flows are 

associated with more runoff contact with surficial 

organic-soil horizons. Weak organic acids released by 

this contact may cause the observed increases in hydrogen ion. Alternatively, rapid movement of precipitation 

to the stream during high flow may result in less 

removal of atmospheric hydrogen ion by weathering or 

ion-exchange reactions. Increases in hydrogen ion at 

high flow must be interpreted in context; even at high 

flows, hydrogen ion concentrations in the streamwater 

were nearly two orders of magnitude lower than those 

in unbuffered precipitation. Thus, these patterns, and 

the postulated controls on hydrogen ion, are of minor 

significance in the overall context of processes affecting 

streamwater chemistry.

Changes in Acid-Neutralization Processes

Acid precipitation is effectively neutralized at the 

experimental basin. Atmospheric inputs of strong acids 

are converted through biogeochemical processes to calcium magnesium bicarbonate-type waters. A key to this 

process is the ability of the basins to retain some of the 

sulfate inputs, probably by sulfate reduction in wetland 

areas bordering the major stream channels. During periods of high runoff, however, the effectiveness of the 

sulfate-retention process diminishes, particularly 

during nonsummer periods when sulfate reduction is 

not as active. At these times, streamwater chemistry 

shifts to a calcium magnesium sulfate-type water, and 

alkalinity is reduced. Alkalinity less than 50 (j,eq/L was 

recorded five times in the experimental basin, before 

and after basin treatment, and two times in the control 

basin (fig. l&F). Thus, the experimental-basin system is 

not in danger of chronic acidification in the immediate 

future, but it approaches episodic acidification during 

high flows.

As with the effects on biogeochemical processes, 

the effect of the forest clearing, fertilization and liming 

on acid neutralization was negligible. Fluxes of 

alkalinity and sulfate were affected little by the basin 

treatment. The massive application of lime in the 

cleared area represents a major one-time addition to the 

acid-neutralizing capacity of the basin, equivalent to the 

amount of calcium that was exported from the 

experimental basin in the 3 water years, 1986,1987, and 

1988 (fig. \9B; table 5). Over time, associated increases 

in base cations and alkalinity probably would be detectable at the basin outlet. Two factors may prevent this 

signal from appearing at the basin outlet in the short 

term. First, the newly applied lime that dissolved and 

became available to plants would be sequestered by the 

highly productive rye and field grasses and the new 

forest regrowth. In other words, the calcium and carbonate inputs would be added to the terrestrial biogeochemical cycle rather than removed by way of 

streamflow. Much of the added calcium may be permanently incorporated in biomass. Over time, however, 

leakages from the biogeochemical cycle to surface 

waters could be expected to result in increased export of 

calcium and alkalinity from the basin. Second, the 

applied lime may not readily dissolve. In a recent study 

at Woods Lake in the Adirondack Mountains, N.Y., in 

which lime was applied to a large watershed by helicopter, undissolved lime pellets were found on the forest 

floor and on the streambed within pools in a small 

stream 1 year after application (Douglas Burns, U.S. 

Geological Survey, oral commun., 1991).

54 Effects of Forest Clearing, Fertilization, and Liming on Hydrology and Water Quality, Quabbin Reservoir, Massachusetts
SUMMARY AND CONCLUSIONS

The effects of selective forest clearing, fertilization, and liming were investigated at Dickey Brook 

Basin, which drains to Quabbin Reservoir in central 

Massachusetts. A paired-basin approach was used in the 

investigation. Background conditions were monitored 

in a control basin (Dickey Brook Tributary Basin) and 

in an experimental basin (Dickey Brook Basin) from 

February 1985 through September 1986. Although 

minor differences in bedrock geology are present (more 

gabbro in the control basin), hydrologic setting (15 percent wetlands in the experimental basin and 4 percent in 

the control basin), and average slope (5 percent in control basin and 2 percent in experimental basin), the 

chemistry and hydrology of the two basins were similar. 

The experimental basin was subject to higher evapotranspiration rates because of its much higher percentage of wetlands. Consequently, before forest clearing, 

the control basin produced higher sustained base flows 

and slightly higher total water yield. Solute concentrations were slightly higher in the control basin, probably 

because it is underlain by a higher percentage of the 

more easily weathered gabbro. In both basins, acidic 

deposition was neutralized by retention of most of the 

hydrogen and nitrate and probably some sulfate (allowing for the sulfate inputs from dry deposition, which 

was not measured). Streamwater quality shifted from a 

calcium magnesium bicarbonate type-water at base 

flow to a calcium magnesium sulfate type water at 

higher flows.

The experimental basin was selectively cleared 

from October 1986 through April 1987. The clearing 

resulted in a slight increase in water yield and solutes in 

water year 1987, most of which occurred during the 

spring high-flow period. The increased flow probably 

resulted from increased insolation on the snow pack 

where the canopy had been moved, and thus more rapid 

snowmelt runoff from the cleared area, as well as from 

decreased evapotranspiration during the 1987 growing 

season. A decrease in evapotranspiration in water year 

1987 was indicated by higher ground-water levels in 

two wells within the cut area. For water year 1987, the 

summer decline of the water table at these wells was the 

least of all five summers in the study period, whereas 

the summer decline at wells in the control basin was the 

maximum of all five summers. Fluxes of nearly all 

major solutes increased in the experimental basin 

during water year 1987. Increased fluxes were attributed primarily to increased water yield rather than to a 

major perturbation in biogeochemical cycles.

Further effects of the forest clearing after the 

summer of 1987 were inconsequential. New surface 

vegetation stabilized the cut areas. Furthermore, little or 

no effect was observed from the fertilization and liming 

applications in following years, despite the high loading 

of nitrate, potassium, and calcium from the treatments 

relative to inputs in precipitation. Much of the added 

nitrogen, potassium, and calcium probably was incorporated in nutrient cycles and (or) the transport of these 

solutes was limited by slow ground-water flow such that 

the signal had not reached the basin outlet before the 

study ended in September 1989. The minimal effect 

observed from the forest clearing and treatment was 

probably a consequence of the limited area of the tree 

cutting, and the position of the cleared area in the 

headwaters of the basin.

REFERENCES CITED

Aubertin, G.M., and Patric, J.H., 1974, Water quality after 

clearcutting a small watershed in West Virginia: Journal 

of Environmental Quality, v. 3, no. 3, p. 243-249.

Bent, G.C., 1994, Effects of timber cutting on runoff to Quabbin Reservoir, central Massachusetts, in Effects of 

human-induced changes on hydrologic systems: American Water Resources Association, 1994 Annual Summer 

Symposium, p. 187-196.

Bigelow, D.S., 1982, National Atmospheric Deposition Program instruction manual, site operation: Fort Collins, 

Colo., Colorado State University, National Atmospheric 

Deposition Program, Program Coordinator's Office, 

30 p.

Bormann, F.H., and Likens, G.E., 1979, Pattern and process 

in a forest ecosystem disturbance, development, and 

the steady state based on the Hubbard Brook ecosystem 

study: New York, Springer-Verlag, 253 p.

Corbett, E.S., Lynch, J.A., and Sopper, WE., 1978, Timber 

harvesting practices and water quality in the eastern 

United States: Journal of Forestry, v. 76, p. 484-488.

Davis, S.N., and De Wiest, R.J.M., 1966, Hydrogeology: 

New York, John Wiley, 463 p.

Dunne, Thomas, Moore, T.R., and Taylor, C.H., 1975, Recognition and prediction of runoff-producing zones in 

humid regions: Hydrologic Sciences Bulletin, v. 20, 

p. 305-327.

Dunne, Thomas, and Leopold, L.B., 1978, Water in environmental planning: San Francisco, W.H. Freeman and 

Company, p. 126-162.

Summary and Conclusions 55
Fishman, M.J., and Friedman, L.C., 1989, Methods for determination of inorganic substances in water and fluvial 

sediments: U.S. Geological Survey Techniques of 

Water-Resources Investigations, book 5, chap. Al, 

545 p.

Gallant, J., Link, I.E., Pardo, A., Kendall, T., and Reid, J.B., 

1990, Bedrock controls on acid neutralization in Quabbin Reservoir tributaries, Massachusetts [abs.]: Geological Society of America, 25th annual meeting, Syracuse, 

N.Y., March 4-7, 1990, v. 22, p. 19.

Godfrey, P.J., 1988, Acid rain in Massachusetts the Massachusetts acid rain research program in action: Amherst, 

Mass., University of Massachusetts, Water Resources 

Research Center, 54 p.

Gorham, E., Martion, F.B., and Litzau, J.T., 1984, Acid 

rain ionic correlations in the eastern United States, 

1980-1981: Science, v. 225, p. 407-409.

Harr, R.D.,1986, Effects of clearcutting on rain-on-snow 

runoff in western Oregon a new look at old studies: 

Water Resources Research, v. 22, no. 7, p. 1095-1100.

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

water resources: Amsterdam, Elsevier, 522 p.

Hornbeck, J.W., Pierce, R.S., Likens, G.E., and Martin, C.W., 

1985, Moderating the impact of contemporary forest 

cutting on hydrologic and nutrient cycles: International 

Association of Hydrologic Sciences Publication 117, 

p. 423-433.

Hornbeck, J.W., Martin, C.W, Pierce, R.S., Bormann, F.H., 

Likens, G.E., and Eaton, J.S., 1986, The northern 

hardwood forest ecosystem ten years of recovery from 

clearcutting: Broomall, Pa., U.S. Forest Service, 

Northeastern Forest Experiment Station, Research 

Paper NE-596, 30 p.

Hornbeck, J.W, Adams, M.B., Corbett, E.S., Verry, E.S., and 

Lynch, J.A., 1993, Long-term impacts of forest treatments on water yield a summary for northeastern 

USA: Journal of Hydrology, v. 150, p. 323-344.

Huntington, T.G., Hooper, R.P., and Aulenbach, B.T., 1994, 

Hydrologic processes controlling sulfate mobility in a 

small forested watershed: Water Resources Research, 

v. 30, no. 2, p. 283-295.

Lawrence, G.B., Fuller, R.D., and Driscoll, C.T., 1987, 

Release of aluminum following whole-tree harvesting at 

the Hubbard Brook Experimental Forest, New 

Hampshire: Journal of Environmental Quality, v. 16, 

p. 383-390.

Likens, G.E., Bormann, F.H., Pierce, R.S., Eaton, J.S., and 

Johnson, N.M., 1977, Biogeochemistry of a forested 

ecosystem: New York, Springer-Verlag, 146 p.

Likens, G.E., Bormann, F.H., Johnson, N.M., Fischer, D.W, 

and Pierce, R.S., 1970, Effects of forest cutting and herbicide treatment on nutrient budgets in the Hubbard 

Brook watershed-ecosystem: Ecological Monographs, 

v. 40, p. 23-47.

Lindberg, S.E., and Garten, C.T, 1988, Sources of sulphur in 

forest canopy throughfall: Nature, v. 336, p. 148-151.

Makower, J., 1964, Geology of the Prescott intrusive complex, Quabbin Reservoir quadrangle, Massachusetts: 

Amherst, University of Massachusetts, M.S. thesis, 

91 p.

Martin, C.W, and Harr, R.D., 1989, Logging of mature Douglas-fir in western Oregon has little effect on nutrient 

output budgets: Canadian Journal of Forest Research, 

v. 19, p. 35-43.

Martin, C.W, and Pierce, R.S., 1980, Clearcutting patterns 

affect nitrate and calcium in streams of New Hampshire: 

Journal of Forestry, v. 78, no. 5, p. 268-272.

Martin, C.W, Noel, D.S., and Federer, C.A., 1984, Effects of 

forest clearcutting in New England on stream chemistry: 

Journal of Environmental Quality, v. 13, p. 204-210.

Mrazik, B.R., Mader, D.L., and MacConnell, W.P., 1980, 

Integrated watershed management an alternative for 

the Northeast: Massachusetts Agricultural Experiment 

Station, Amherst, Mass., Research Bulletin 664, 50 p.

56 Effects of Forest Clearing, Fertilization, and Liming on Hydrology and Water Quality, Quabbin Reservoir, Massachusetts
National Oceanographic and Atmospheric Administration, 

1985, Climatological data, annual summary, New 

England: v. 97, no. 13, 36 p.

Nodvin, S.C., Driscoll, C.T., and Likens, G.E., 1986. The 

effect of pH on sulfate adsorption by a forest soil: Soil 

Science, v. 142, p. 69-75.

Patric, J.H., and Reinhart, K.G, 1971, Hydrologic effects of 

deforesting two mountain watersheds in West Virginia: 

Water Resources Research, v. 7, p. 1182-1188.

Peters, N. E., 1989, Chloride cycling in forested lake watersheds in the west-central Adirondack Mountains, New 

York, in Moldan, Bedrich, and Paces, Tomas, eds., 

GEOMON, International workshop on geochemistry 

and monitoring in representative basins extended 

abstracts: Prague, Czechoslovakia, Geological Survey, 

p. 264-266.

Pierce, R.S., Horabeck, J.W., Likens, G.E., and Bormann, 

F.H., 1972, Nutrient loss from clearcuttings in New 

Hampshire, in Csallany, C.S. and others, eds., Symposium on Watersheds in Transition, Fort Collins, Colorado, June 19-22, 1972: Urbana, 111., American Water 

Resources Association, p. 285-295.

Rantz, S.E., and others, 1982, Measurement and computation 

of streamflow, volume 1 measurement of stage and 

discharge: U.S. Geological Survey Water-Supply Paper 

2175, 284 p.

Rittmaster, R.L., and Shanley, J.B., 1995, Factors affecting 

water quality and net flux of solutes in two stream basins 

in the Quabbin Reservoir Watershed, central Massachusetts, 1983-1985: U.S. Geological Survey WaterResources Investigations Report 94-4003.

Rutter, A.J., 1968, Water consumption in forests, in 

Kozlowski, T.T., ed., Water deficits and plant growth: 

New York, Academic Press, v. 2, p. 23-84.

Shanley, J.B., 1994, Effects of ion exchange on stream solute 

fluxes in a basin receiving deicing salts: Journal of 

Environmental Quality, v. 23, p. 977-986.

Shanley, J.B., and Peters, N.E., 1993, Variations in aqueous 

sulfate concentrations at Panola Mountain, Georgia: 

Journal of Hydrology, v. 146, p. 361-382.

Stekl, P.J., 1985, A hydrologic investigation of two small 

watersheds of the eastern Quabbin subbasin: Amherst, 

University of Massachusetts, M.S. thesis, 169 p.

Thornthwaite, C.W., and Mather, J.R., 1955, The water 

balance: Centerton, N.J., Laboratory of Climatology, 

Publications in Climatology, v. 8, no. 1, 104 p.

Troendle, C.A., 1983, The potential for water yield augmentation from forest management in the Rocky Mountain 

region: Water Resources Bulletin, v. 19, p. 359-373.

Troendle, C.A., and King, R.M., 1985, The effects of timber 

harvest on the Fool Creek watershed, 30 years later: 

Water Resources Research, v. 21, p. 1915-1922.

Trimble, S.W., Weirich, F.H., and Hoag, B.L., 1987, Reforestation and the reduction of water yield on the southern 

Piedmont since circa 1940: Water Resources Research, 

v. 23, p. 425-437.

Verry, E.S., 1986, Forest harvesting and water the Lake 

States experience: Water Resources Bulletin, v. 22, 

p. 1039-1047.

Vitousek, P.M., 1981, Clear-cutting and the nitrogen cycle: 

Ecological Bulletin, v. 33, p. 631-642.

Wandle, W.W., Jr., 1983, Estimating peak discharges of 

small, rural streams in Massachusetts: U.S. Geological 

Survey Water-Supply Paper 2214, 26 p.

Wolock, D.M., Hornberger, G.M., and Musgrove, T.J., 1990, 

Topographic effects on flow path and surface water 

chemistry of the Llyn Brianne catchments in Wales: 

Journal of Hydrology, v. 115, p. 243-259.

Yuretich, Richard; Leonard, Wendy; and Pohanka, Susan, 

1989, Hydrogeologic factors affecting acid neutralization in Cadwell Creek watershed, west central Massachusetts: Water Resources Research, v. 25, p. 644-654.

Zen, E-an, Goldsmith, G.R., Ratcliffe, N.L., Robinson, P., 

and Stanley, R.S., 1983, Bedrock geologic map of Massachusetts: Washington, D.C., U.S. Geological Survey, 

3 sheets.

References Cited 57