FACTORS AFFECTING WATER QUALITY AND NET 

FLUX OF SOLUTES IN TWO STREAM BASINS IN 

THE QUABBIN RESERVOIR DRAINAGE BASIN, 

CENTRAL MASSACHUSETTS, 1983-85

By ROCHELLE L. R ITT MA STEP and JAMES B. SHANLEY

U.S. GEOLOGICAL SURVEY

Water-Resources Investigations Report 94-4003

Prepared in cooperation with the 

METROPOLITAN DISTRICT COMMISSION and the 

MASSACHUSETTS DEPARTMENT OF ENVIRONMENTAL PROTECTION 

DIVISION OF WATER POLLUTION CONTROL

Marlborough, Massachusetts 

1995
U.S. DEPARTMENT OF THE INTERIOR 

BRUCE BABBITT, 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 Federal Center

Denver, CO 80225
CONTENTS

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

Introduction........................................................................................................................................................................ 2

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

Related Studies....................................................................................................................................................... 3

Location and Description of Study Area................................................................................................................ 4

Acknowledgments.................................................................................................................................................. 8

Methods of Study............................................................................................................................................................... 9

Sampling and Data Collection................................................................................................................................ 9

Precipitation................................................................................................................................................ 9

Streamflow.................................................................................................................................................. 9

Ground Water and Soil Water ..................................................................................................................... 11

Sample Handling and Chemical Analyses.............................................................................................................. 12

Estimation of Chemical Fluxes Entering and Leaving Stream Basins................................................................... 12

Chemical Inputs in Precipitation................................................................................................................. 12

Chemical Outputs in Streamflow................................................................................................................ 13

Net Fluxes................................................................................................................................................... 14

Hydrology of Stream Basins.............................................................................................................................................. 14

Precipitation............................................................................................................................................................ 14

Streamflow.............................................................................................................................................................. 14

Ground-Water Discharge........................................................................................................................................ 16

Evapotranspiration.................................................................................................................................................. 17

Chemical Quality of Precipitation, Streams, Ground Water, and Soil Water..................................................................... 17

Precipitation Quality............................................................................................................................................... 17

Stream-Water Quality............................................................................................................................................. 19

Major-Ion Chemistry................................................................................................................................... 19

Aluminum Chemistry.................................................................................................................................. 25

Trace Elements............................................................................................................................................ 30

Ground-Water and Soil-Water Quality ................................................................................................................... 30

Chemical Fluxes Entering and Leaving Stream Basins..................................................................................................... 30

Chemical Input Loads in Precipitation................................................................................................................... 30

Chemical Output Loads in Streamflow................................................................................................................... 32

Concentration-Discharge Relations............................................................................................................. 32

Monthly Solute Fluxes in Streamflow......................................................................................................... 32

Net Solute Fluxes.................................................................................................................................................... 32

Factors Affecting Water Quality and Net Flux of Solutes ................................................................................................. 39

Precipitation Quality............................................................................................................................................... 39

Basin Hydrogeology............................................................................................................................................... 40

Hydrologic Flow Paths................................................................................................................................ 40

Mineral Weathering..................................................................................................................................... 41

Aluminum Geochemistry........................................................................................................................................ 44

Seasonal Variations..................................................................................................................................... 44

Spatial Variations......................................................................................................................................... 44

Chemical Speciation and Solubility of Dissolved Aluminum .................................................................... 47

Biogeochemical Processes...................................................................................................................................... 50

Sulfate Mobility .......................................................................................................................................... 50

Retention of Hydrogen and Nitrate............................................................................................................. 52

Application of Deicing Salts................................................................................................................................... 53

Adjustment of Chemical Fluxes.................................................................................................................. 53

Comparison of Calculated Salt-Export and Salt-Application Data............................................................. 57

Acidification Status of the Basins ...................................................................................................................................... 58

Summary and Conclusions................................................................................................................................................. 61

References Cited................................................................................................................................................................ 62

Contents iii
FIGURES

1-5. Maps showing:

1. Locations of the West Branch Swift River and East Branch Fever Brook Basins,

central Massachusetts................................................................................................................................ 5

2. Lithology of bedrock underlying the West Branch Swift River Basin............................................................. 6

3. Lithology of bedrock underlying the East Branch Fever Brook Basin............................................................ 7

4. Surface-water, ground-water, and soil-water sampling sites, West Branch Swift River Basin........................ 10

5. Surface-water, ground-water, and soil-water sampling sites, East Branch Fever Brook Basin....................... 11

6-19. Graphs showing:

6. Mean monthly (1943-80) and monthly precipitation (November 1983 through August 1985)

at New Salem, Massachusetts.................................................................................................................... 15

7. Temporal variation of discharge and base flow, West Branch Swift River and East Branch Fever

Brook, December 1983 to September 1985............................................................................................... 16

8. Relations between hydrogen ion concentration and sulfate concentration, and hydrogen ion

concentration and sulfate plus nitrate concentration in wet deposition, New Salem, Massachusetts....... 18

9. Temporal variation of runoff, specific conductance, and concentrations of selected chemical solutes,

West Branch Swift River........................................................................................................................... 21

10. Temporal variation of runoff, specific conductance, and concentrations of selected chemical solutes,

East Branch Fever Brook........................................................................................................................... 23

11. Temporal variation of pH and concentrations of selected chemical solutes, tributaries of West Branch

Swift River and East Branch Fever Brook................................................................................................. 27

12. Relations between aluminum concentrations and pH in surface water, ground water, and soil water,

West Branch Swift River and East Branch Fever Brook........................................................................... 29

13. Relations between discharge and pH, calcium, alkalinity, and sulfate at West Branch Swift River and

East Branch Fever Brook........................................................................................................................... 34

14. Composition of water and stability of systems K^O-A^C^-SiC^-I^O and CaO-A^C^SiC^-I^O

at 25 degrees Celsius, West Branch Swift River and East Branch Fever Brook Basins............................ 45

15. Relations between aluminum concentration and pH, and aluminum concentration and dissolved organic

carbon concentration, West Branch Swift River and East Branch Fever Brook Basins........................... 46

16. Composition of water and stability of dissolved aluminum species in equilibrium with gibbsite 

and kaolinite at 25 degrees Celsius, West Branch Swift River and East Branch Fever 

Brook Basins.............................................................................................................................................. 49

17. Relations between sulfate and alkalinity concentrations in West Branch Swift River and

East Branch Fever Brook, June through October 1984............................................................................. 52

18. Charge balance for solute fluxes from the West Branch Swift River and East Fever Brook Basins,

December 1983 through August 1985....................................................................................................... 54

19. Relations between calcium plus magnesium concentrations and major anion solutes in stream water

in the West Branch Swift River and East Branch Fever Brook................................................................. 60

TABLES

1. Annual hydrologic budgets for West Branch Swift River and East Branch Fever Brook Basins,

central Massachusetts.......................................................................................................................................... 15

2. Volume-weighted-average concentrations of solutes in wet deposition, New Salem, Massachusetts..................... 17

3. Flow-weighted-average concentrations of chemical solutes and runoff data, West Branch Swift

River and East Branch Fever Brook, central Massachusetts.............................................................................. 20

4. Summary of mean pH and chemical solute concentrations at surface-,

ground-, and soil-water sampling sites,West Branch Swift River and East Branch Fever Brook

Basins, central Massachusetts............................................................................................................................. 26

5. Monthly loads of chemical solutes in wet deposition, New Salem, Massachusetts................................................. 31

6. Regression-model parameters for specific conductance and major chemical solutes in

West Branch Swift River and East Branch Fever Brook, central Massachusetts............................................... 33

7. Estimates of monthly chemical loads in streamflow and monthly runoff, West Branch Swift River and

East Branch Fever Brook, central Massachusetts............................................................................................... 36

8. Fluxes of major solutes and water, West Branch Swift River and East Branch Fever Brook Basins,

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

iv Contents
9. Saturation index for some minerals for flow-weighted-average base-flow and ground-water samples in 

West Branch Swift River and East Branch Fever Brook Basins, central Massachusetts.........................

10. Chemical speciation of aqueous aluminum in selected water samples from West Branch Swift River and 

East Branch Fever Brook Basins, central Massachusetts........................................................................

11. Composition of rock salt applied in West Branch Swift River and East Branch Fever Brook Basins,

central Massachusetts...............................................................................................................................

12. Deicing salt-application data, West Branch Swift River and East Branch Fever Brook Basins,

central Massachusetts...............................................................................................................................

13. Chloride load in applied deicing salt and net chloride flux from West Branch Swift River and

East Branch Fever Brook Basins, December 1983 through August 1985...............................................

43

48

56

57

58

CONVERSION FACTORS AND VERTICAL DATUM

Multiply By To obtain

cubic meter (m3 )

T fj

cubic meter per second per square kilometer [(m /s/km ]

hectare (ha)

kilometer (km)

liter (L)

meter (m)

meter per kilometer

millimeter (mm)

millimeter per day (mm/d)

square kilometer (km2)

35.31

91.49

0.003861

0.6214

0.2642

3.281

5.28

0.03937

0.03937

0.3861

cubic foot

cubic foot per second per square mile

square mile

mile

gallon

foot

foot per mile

inch

inch per day

square mile

Temperature in degrees Celsius (°C) can be converted to degrees Fahrenheit (°F) as follows: °F = (1.8 x °C) + 32.

Vertical Datum

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

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

Conversion Factors and Vertical Datum v
Factors Affecting Water Quality and Net 

Flux of Solutes in Two Stream Basins in 

the Quabbin Reservoir Drainage Basin, 

Central Massachusetts, 1983-85

By Rochelle L. Rittmaster and James B. Shanley

Abstract

The factors that affect stream-water quality 

were studied in two forested basins in metamorphic 

schist and gneiss terrane of central Massachusetts. 

West Branch Swift River (Swift River), which 

drains 32.9 square kilometers, and East Branch 

Fever Brook (Fever Brook), which drains 12.6 

square kilometers, flow into the northern part of 

Quabbin Reservoir, which supplies most of the 

water for metropolitan Boston. Data were collected 

on the hydrology and major solute chemistry of precipitation, surface water, ground water, and soil 

water. Spatial and temporal variations in chemistry 

and relations between chemical changes and hydrologic processes then were used to identify the mechanisms most important in the chemical evolution of 

water from acidic precipitation to moderately 

buffered stream water.

During the 21-month study period, December 

1983 through August 1985, precipitation chemistry 

was dominated by hydrogen ion (composite pH 

4.23), sulfate, and nitrate. Precipitation was 

1,546 millimeters during the first 10 months 

compared to 969 millimeters during the final 11 

months of the period, yet chemical inputs to the 

basins were higher during the second period by 41 

percent for hydrogen ion, 44 percent for sulfate, and 

36 percent for nitrate. Base-cation inputs were 

lower in the final 11 months by an amount directly 

proportional to the decrease in precipitation. The 

more acidic composition of precipitation during the 

final 11-month period indicates a shift in storm track

from coastal to continental, allowing air masses to 

acquire acidic precursors from industrialized 

regions west of the study area.

Stream chemistry was significantly affected by 

highway deicing salts, particularly in the Fever 

Brook Basin, where sodium and chloride were the 

dominant solutes. Some sodium in deicing salt 

replaced calcium and magnesium on cationexchange sites, resulting in increased export of 

those base cations in streamflow. At the Swift River 

outlet gaging station, concentrations of base cations 

and silica were relatively constant, although moderate dilution occurred at high flows and concentrations increased during base flow in the summer. At 

the Fever Brook outlet gaging station, base-cation 

concentrations were more variable than those at the 

Swift River outlet gaging station, and the dilution of 

silica was much greater during high flow in spring. 

At each gaging station, potassium concentrations 

peaked later in the year relative to concentration 

peaks of the other base cations because of leaching 

of potassium from fallen leaves. Alkalinity was less 

than 50 microequivalents per liter for most of the 

year at each gaging station, but increased to near 

150 microequivalents per liter in summer and early 

autumn. Organic acidity in stream water at the Fever 

Brook gaging station caused higher concentrations 

of dissolved organic carbon, hydrogen ion, and aluminum compared to the Swift River gaging station. 

However, episodic increases of hydrogen ion and 

aluminum were more frequent at the Swift River 

gaging station. Aluminum concentrations increased 

from less than 100 to nearly 300 micrograms per

Abstract 1
liter during high-flow periods in both streams. The 

large input of atmospheric sulfate was reflected in 

flow-weighted mean sulfate concentrations greater 

than 130 microequivalents per liter in both streams. 

At the Swift River gaging station, sulfate concentrations were relatively constant, whereas at the Fever 

Brook gaging station, sulfate concentrations 

decreased in summer as a result of sulfate reduction 

in wetlands.

Differences in stream-water quality among 

tributary sites in each basin can be attributed to variations in geology and hydrology. At Swift River, a 

subbasin that comprises only 11.2 percent of the 

total basin area contributed nearly 25 percent of the 

total base cations, 16 percent of the total silica, and 

77 percent of the total alkalinity exported from the 

basin. This subbasin is underlain by gabbro composed of hornblende and calcium feldspar, rather 

than the felsic rocks of quartz and sodium and potassium feldspars that underlie most of the remainder 

of Swift River Basin.

The large inputs of hydrogen ion and nitrate in 

wet deposition were almost entirely retained in the 

basins. In contrast, in the Swift River Basin, the 

output of sulfate in stream water (1,684 equivalents 

per hectare) was 63 percent greater than the input in 

wet deposition (1,034 equivalents per hectare). The 

net export of 650 equivalents per hectare was attributed predominantly to dry deposition of sulfate, 

which was not measured. Net export of sulfate from 

the Fever Brook Basin was only about one-half as 

much as that from Swift River Basin because of sulfate reduction in the extensive wetlands in Fever 

Brook Basin during summer and early autumn.

The weathering of hornblende and plagioclase 

controlled base-cation fluxes at both outlet gaging 

stations. After correction for the effect of deicing 

salts, the net flux of base cations was 41 percent 

greater at Swift River (2,014 equivalents per 

hectare) than at Fever Brook (1,429 equivalents per 

hectare) for the 21-month study period. The net flux 

of silica was 58 percent greater at Swift River (1,260 

moles per hectare) than at Fever Brook (799 moles 

per hectare). The disproportionately greater export 

of silica and calcium and the higher

calcium:magnesium ratio at Swift River compared 

to that at Fever Brook indicates that plagioclase 

weathering is predominant in the Swift River Basin, 

and that hornblende weathering is predominant in 

the Fever Brook Basin. The overall weathering rate 

appears to be greater in the Swift River Basin 

because of the presence of the easily weathered 

gabbro in one small subbasin, and because of a 

higher proportion of ground-water discharge at 

Swift River relative to that at Fever Brook. The 

alkalinity is about the same in each basin, however, 

because the additional alkalinity generated by 

higher weathering rates at Swift River is balanced 

by additional alkalinity generated by sulfate reduction coupled with organic carbon oxidation at Fever 

Brook.

An indication that acidification is occurring in 

Swift River and Fever Brook is that the sum of 

equivalents of base cations (primarily calcium and 

magnesium) is not balanced by bicarbonate alkalinity. Because sulfate concentrations generally were 

greater than alkalinity, sulfate in the stream water is 

the dominant anion accounting for transport of base 

cations from the basins. An important finding of the 

study was that sodium in highway deicing salts 

exchanged for calcium and magnesium on soil 

cation-exchange sites, which resulted in increased 

export of calcium and magnesium in stream water.

INTRODUCTION

The potential adverse effects of atmospheric acid 

deposition, commonly referred to as acid rain, have 

drawn national and international attention. Researchers 

in the United States, Canada, and Europe have been 

investigating the effect of acid deposition on damage to 

forests, mobility of heavy metals in soil and water, 

decreasing populations of fish and other aquatic life, 

and acidification of surface waters (Galloway and 

others, 1983; Henriksen and others, 1984; Schindler, 

1988).

The Quabbin Reservoir in central Massachusetts 

supplies most of the water demand for the Boston metropolitan area. The reservoir is owned and managed by 

the Metropolitan District Commission (MDC). Runoff 

from 485 km2 of drainage basin is impounded in the

2 Factors Affecting Water Quality and Net Flux of Solutes in Two Stream Basins, Quabbin Reservoir Basin, Central Mass., 1983-85
1.56 million m reservoir (Nesson, 1983). The 100-km2 

surface and 190 km of shoreline also are used for 

limited recreation.

Records maintained by the MDC indicate that 

alkalinity in the reservoir has decreased from greater 

than 200 |Lieq/L (microequivalents per liter) in the 

1940's to less than 100 |Lieq/L in 1980. Increased acidity 

could result in the mobilization of aluminum, which can 

affect the quality of drinking water (Sung and others, 

1984), and can be toxic to biota (Halliwell, 1985). Fishpopulation declines and some local fish kills have been 

observed in streams that discharge into the Quabbin 

Reservoir (DiNardo, 1984; Gelbspan, 1984).

In response to concerns about the effects of acid 

deposition on water quality and aquatic ecology of the 

Quabbin Reservoir, the MDC and the Division of Water 

Pollution Control of the Massachusetts Department of 

Environmental Protection (then known as the Department of Environmental Quality Engineering) cooperated with the U.S. Geological Survey (USGS) on a 21- 

month study (1983-85) of the hydrology and streamwater quality of two forested drainage basins whose 

streams discharge into the reservoir. These basins were 

selected on the basis of different geology and surfacewater hydrology so that various physical and chemical 

conditions could be considered.

The initial impetus for this study was primarily a 

concern over the effects of acid deposition on streamwater quality in the Quabbin Reservoir drainage basin. 

Knowledge of how acidic atmospheric inputs are processed in tributary basins in the drainage basin is vital to 

assessing the possibility of acidification in the reservoir. 

The elements of the study included: (1) collection 

and chemical analysis of wet deposition near the 

Quabbin Reservoir; (2) collection and chemical 

analysis of soil-water, ground-water, and stream-water 

samples, and measurement of stream discharge in the 

West Branch Swift River and East Branch Fever Brook 

Basins from December 1983 through August 1985; 

(3) calculation of fluxes of major chemical solutes 

entering each drainage basin in wet deposition and leaving in streamflow; and (4) interpretation of spatial and 

temporal variability of stream-water quality and solute 

fluxes on the basis of hydrologic, geologic, and 

biogeochemical characteristics of each drainage basin.

Purpose and Scope

The purpose of this report is to describe and interpret the processes that affect the net flux of solutes and 

the quality of stream water that discharges into Quabbin 

Reservoir. The report describes how solute fluxes and 

stream-water quality are affected by the quality of 

precipitation, basin hydrologic characteristics, and mineral weathering processes, with special attention to 

aluminum geochemistry. Other effects considered are 

general biogeochemical processes and the application 

of highway deicing salts. Spatial and temporal variations in solute concentrations and fluxes in stream water 

are evaluated in light of these potential controlling 

factors. Finally, the status of the basins with respect to 

acidification from atmospheric deposition is evaluated. 

The report details the extensive field sampling effort 

undertaken to collect the data needed for these interpretations. The study covered a 21-month period from 

1983 to 1985. The report is intended to provide managers of water resources in the Quabbin Reservoir drainage basin with sound scientific information that will 

help them guide their water-resources management 

decisions.

Related Studies

The bedrock geology of the area around the northern shoreline of the Quabbin Reservoir has been the 

subject of numerous investigations by the University of 

Massachusetts, Department of Geology (Makower, 

1964; Ashenden, 1973; Michener, 1983). Beginning in 

the 1980's, this work was supplemented by a series of 

hydrogeologic and hydrogeochemical investigations. 

Batchelder and others (1983) and Yuretich and Batchelder (1988) found that weathering rates in the Fort 

River Basin near Amherst were greater than rates at 

Hubbard Brook, N.H., because of differences in weathering processes and hydrogeology. Variations in hydrologic flow paths were the most important factor 

affecting spatial differences in ground-water chemistry 

in the adjacent Cadwell Creek Basin (Leonard and 

others, 1984; Yuretich and others, 1989).

Steckl (1985) contrasted hydrogeologic characteristics of Carter and Mundberry Brooks, two adjacent 

drainage basins on the northeast side of the Quabbin 

Reservoir. Although the residence time of ground water 

was similar in the two basins, weathering rates seemed 

greater in Carter Brook Basin because of the greater

Introduction 3
areal extent of thicker unconsolidated surficial deposits 

in the basin compared to Mundberry Brook Basin. The 

hydrochemistry of these two drainage basins has been 

studied in greater detail by researchers from the University of Massachusetts (Knapp, 1990; McManamon, 

1990) to compare the hydrochemistry of these two 

drainage basins to that in the Cadwell Creek Basin. A 

preliminary comparison of the two areas, including derivations of the pertinent weathering reactions that control the stream chemistry, was made by Yuretich and 

others (1986).

The USGS also has completed studies related to 

acid deposition in the Quabbin area and in other parts of 

Massachusetts. Gay and Melching (1994) collected precipitation samples at two sites in the State, and correlated precipitation chemistry with the track of the storm 

in an effort to relate rainfall acidity to its geographic 

source. This work was followed by a study in which the 

liquid and solid phase of incremental precipitation samples were analyzed to better define the geographic 

origin of the air mass and detecting changes in air 

masses during storms (Risley and Shanley, 1994).

Another USGS study in the Quabbin area investigated the effects of clearcutting on water quality and 

quantity (Shanley and others, written commun., 1992). 

The study used a paired drainage basin approach; one 

drainage basin was a control and a second drainage 

basin was partially logged, then limed and planted in rye 

grass, to ascertain whether this management practice 

could be used to increase runoff without affecting water 

quality. Bent (1994) analyzed the hydrologic results of 

that study. A report tabulating data on which the present 

report is based was prepared by Rittmaster and Girouard 

(1992). Finally, Shanley (1994) used data collected as 

part of the present study to determine that ion exchange 

of sodium in deicing salt for calcium and magnesium in 

soil altered the proportions of cations in stream solute 

fluxes.

Location and Description of Study Area

The drainage basins selected for study are in the 

Swift River subbasin of the Chicopee River, one of the 

major tributaries of the Connecticut River in central 

Massachusetts. West Branch Swift River Basin, hereafter referred to as Swift River, lies northwest of Quabbin 

Reservoir and drains 32.9 km2 ; East Branch Fever 

Brook Basin, hereafter referred to as Fever Brook, lies

northeast of Quabbin Reservoir and drains 12.6 km2 

(fig. 1). Altitude at the reservoir is 160 m above sea 

level, and altitudes range from 168 to 369 m above sea 

level in the Swift River Basin, and from 213 to 372 m 

above sea level in the Fever Brook Basin.

The average annual precipitation at New Salem, 

near the northwest shore of Quabbin Reservoir, is about 

1,270 mm, based on 44 years of record (National Oceanic and Atmospheric Administration, 1985a). Average 

annual snowfall at Worcester, 48 km southeast of the 

Quabbin Reservoir, is 1,780 mm, based on 28 years of 

record. Annual means of daily maximum and minimum 

temperatures at Worcester are 13 and 3°C.

Perennial streams in the Swift River Basin are 

roughly parallel, and generally trend north-south 

reflecting the significant control of the underlying geologic structure on drainage-pattern development 

(Thornbury, 1969). Ephemeral tributaries drain ridges 

with stream gradients of as much as 66 m/km. The 

drainage pattern in the Fever Brook Basin consists of 

irregular stream courses and short tributaries. In the 

western half of Fever Brook Basin, the hummocky terrain is composed of stratified-drift deposits. The terrain 

of the Fever Brook Basin generally is less rugged than 

the terrain of the Swift River Basin. Fever Brook Basin 

contains natural and manmade impoundments. Prominent features in Fever Brook Basin include Brooks 

Pond, which covers about 0.65 km2 in the upper part of 

the basin, and marshy areas in much of the lower half of 

the basin. In contrast, there is only one small 

impoundment in the headwater area of the Swift River 

Basin.

Most of the bedrock in the study area is composed 

of metamorphosed Paleozoic sediments and volcanics 

of the Bronson Hill tectonic province (Robinson, 1967). 

Dominant lithologies include felsic gneiss, schist, 

amphibolite, quartzite, gabbro, and minor granitic intrusives (figs. 2 and 3). Episodes of folding and faulting 

during the Acadian Orogeny imposed north-south 

trending ridges and valleys throughout the region. Bedrock outcrops generally follow the structural trend 

along ridges and hilltops (Mulholland, 1974). Numerous investigations of the regional bedrock have revealed 

few faults in the area, and ground-water loss to bedrock 

fractures is minimal (Yuretich and others, 1986).

4 Factors Affecting Water Quality and Net Flux of Solutes in Two Stream Basins, Quabbin Reservoir Basin, Central Mass., 1983-85
73.00' 72°00'

N

72 30

42°30' 

42 20' 

Base from U.S. Geological Survey

Digital Line Graphs

Scale 1:100,000, Polyconic projection 5 KILOMETERS

Figure 1 . Locations of the West Branch Swift River and East Branch Fever Brook Basins, central 

Massachusetts.

Introduction 5
72°24'

42°32' 

EXPLANATION

FELSIC GNEISS AND QUARTZITE 

FELSIC GNEISS

SSSSSS AMPHIBOLITE FELSIC GNEISS, SCHIST 

HORNBLENDE GABBRO

 DRAINAGE BASIN BOUNDARY

 SUBBASIN DRAINAGE BOUNDARY

5,000 FEET

I I I I

1,000 METERS

Figure 2. Lithology of bedrock underlying the West Branch Swift River Basin, central 

Massachusetts. (Geology from Robinson, 1967.)

6 Factors Affecting Water Quality and Net Flux of Solutes in Two Stream Basins, Quabbin Reservoir Basin, Central Mass., 1983-85
42°31' 

42°30'

42°29'

EXPLANATION

ALUMINOUS AND QUARTZOSE SCHISTS

SULFIDIC SCHIST AND AMPHIBOLITE

BIOLITE-PLAGIOCLASE DIORITE 

AND GNEISS

1 - DRAINAGE BASIN BOUNDARY 

 SUBBASIN DRAINAGE BOUNDARY

5,000 FEET

J___L

1,000 METERS

Figure 3. Lithology of bedrock unaenying ine bast Branch Fever Brook Basin, central 

Massachusetts. (Geology from Robinson, 1967.)

Mantled over the largely impermeable bedrock 

units are water-bearing unconsolidated materials deposited by glacial processes during the Pleistocene epoch. 

On the basis of regional reconnaissance mapping of the 

textures of surficial deposits, Stone and others (1979) 

delineated two major groups till and stratified drift. 

Till, which is more widely distributed, was formed 

beneath the ice by the movement and abrasion of continental ice sheets over bedrock, or formed as a residue 

from rock material imbedded in melting ice. Grain size 

of the typically unstratified and unsorted till ranges from 

clay to boulder, and thickness is as much as tens of feet 

(Newton, 1978). Minerals in the till probably are 

derived from local bedrock; Retelle (1979) found pebbles similar to underlying or nearby bedrock in a study 

of tills just north of the study area. Stratified drift typically overlies till in valleys but not exclusively. These 

deposits were formed in running or impounded glacial

meltwater and commonly are well sorted. Grain size of 

the stratified-drift layers ranges from silt to gravel (Mulholland, 1974; Stone and others, 1979). Stratified-drift 

deposits can be areally extensive, as in a kame plain or 

terrace, or of local areal extent, as in an esker (Eschman, 

1966).

The combined effects of glaciation and local bedrock geology have resulted in distinctly different terrains in the two basins. Glacier movements over belts of 

resistant gneisses and less-resistant schists in the Swift 

River Basin produced a terrain of steep ridges and 

exposed bedrock that alternate with valleys filled with 

tens of feet of unconsolidated till and stratified drift. In 

contrast, the Fever Brook Basin, which is underlain primarily by schist, consists of gentle slopes with few 

ridges and exposures of bedrock. Stratified drift composes 13 and 18 percent of surficial deposits in the Swift

Introduction 7
River and Fever Brook Basins, respectively (D.D. 

Ashenden, Metropolitan District Commission, written 

commun., 1986).

The major mineral composition also differs in the 

two basins. The diverse mineralogy of the bedrock 

underlying the Swift River Basin reflects the variability 

of bedrock geology (Makower, 1964; Ashenden, 1973; 

Michener, 1983; Shearer, 1983). One part of the Four 

Mile Gneiss, which underlies a large percentage of the 

drainage basin, is biotite-feldspar gneiss and amphibolite. These rocks are composed of microcline, sodic plagioclase, biotite, quartz, and hornblende. The Erving 

and the Mount Mineral Formations, which also underlie 

part of the basin, have amphibolites that contain hornblende and epidote. The Littleton Formation has muscovite and sodic plagioclase (albite) as major minerals. In 

the southeast part of the basin, the dominant lithology is 

a gabbro member of the Prescott Complex that contains 

50 to 72 percent hornblende, and calcic plagioclase 

(labradorite). The Cooleyville Granitic Gneiss, also in 

the southeastern subcatchment, is a fine-grained gneiss 

primarily composed of andesine a plagioclase intermediate in calcium content to the plagioclase in the 

Four Mile Gneiss and that in the Prescott Complex.

The Fever Brook Basin is underlain by large bands 

of the Littleton and the Rangely Formations and minor 

stringers of the Monson Gneiss and Hardwick Tonalite. 

The Littleton is composed of aluminous schist and phyllite (predominantly muscovite and albite, but containing 

some biotite and chlorite). The major mineral assemblages of rocks in the Rangely Formation include: (1) a 

sulfidic mica schist composed of quartz, muscovite, 

biotite, sillimanite, and sodic-rich plagioclase, as well 

as some iron sulfides; and (2) amphibolite, composed 

predominantly of hornblende.

The soils in both basins are classified as inceptisols 

(U.S. Department of Agriculture, 1975) immature 

soils with poorly developed horizons. Soils derived 

from stratified drift contain large amounts of sand and 

gravel and generally are less than 60 cm (centimeters) 

deep (Lyford, 1964a). Soils derived from till are stony 

and gravelly and may have localized hardened layers 

(Patric and Lyford, 1980). The drainage of these silty, 

low-clay soils is moderate to good but may be poor in 

closed depressions (Lyford, 1964b). Soil samples collected in the Swift River and Fever Brook Basins are 

described by Rittmaster and Girouard (1992). The O 

horizon consists of fresh and decomposed organic

material, and the loamy A horizon consists of mineral 

soil and organic matter. A weakly developed but extensive B horizon is only slightly altered from the parent 

material. Yellowish and reddish mottling indicates oxidation to ferric minerals in this horizon. Underlying the 

B horizon is a virtually unaltered C horizon composed 

of sandy and silty material from the stratified drift and 

till parent materials. The descriptions of the soil profiles 

from the Swift River and Fever Brook Basins were similar to the description of an inceptisol developed on glacial deposits in the Cadwell Creek Basin, about 14 km 

south of the Swift River Basin (Leonard and others, 

1984).

The dominant clay mineral (less than 2 jo.m) in 

nearly all soil samples from the two basins was vermiculite (Rittmaster and Girouard, 1992). Minor amounts 

of illite and kaolinite also were present in nearly all 

samples. Chlorite was a major clay mineral in some 

samples. Gibbsite was relatively abundant in samples 

from the Swift River Basin but was detected in only one 

of six samples from the Fever Brook Basin.

Four soil profiles from each basin were analyzed 

for pH, exchangeable cations, and cation-exchange 

capacity (CEC) (Rittmaster and Girouard, 1992). CEC 

in both basins ranged from 0.5 to 12 jo.eq/100 g; base 

saturation ranged from 15 to 96 percent at Swift River, 

and from 10 to 57 percent at Fever Brook. In general, 

CEC was highest in surface soil (O horizon), and 

decreased with depth. Percentage of base saturation 

tended to increase with soil depth. Soil-slurry pH generally ranged from 3.7 to 4.2 in the organic horizons to 4.4 

to 4.6 in the deeper mineral soil.

Historically, the land has been sparsely settled. 

Remnants of settlements include extensive sections of 

stone walls and breached small dams. Both drainage 

basins are forested with a mixture of deciduous and 

coniferous vegetation, including red oak, white ash, red 

maple, sugar maple, and white pine. The canopy 

reaches a height of 18 m, indicative of several decades 

of generally undisturbed growth.

Acknowledgments

The authors acknowledge State and local government personnel, and local residents who provided time 

and information to this study. The authors express gratitude to Mr. David Ashenden and Mr. Bruce Spencer, of 

the Metropolitan District Commission, for their on-site

8 Factors Affecting Water Quality and Net Flux of Solutes in Two Stream Basins, Quabbin Reservoir Basin, Central Mass., 1983-85
work and contributions to the study; to Norman 

LaPointe of the Petersham Department of Public Works, 

who provided information on deicing-salt application in 

Fever Brook Basin; and to Elizabeth Knapp and Ann 

McManamon of the University of Massachusetts, who 

provided chemical data from their study area adjacent to 

Fever Brook Basin.

METHODS OF STUDY

A data-collection network (figs. 4 and 5) was 

established to measure the various components of the 

chemical and the hydrologic budgets. Chemical and 

hydrologic mass balances were computed as the 

difference between chemical and hydrologic inputs in 

precipitation and outputs in stream water. Adjustments 

were made for solutes affected by the application of 

deicing salts in the drainage basins. Data were collected 

from December 1983 to August 1985. Site descriptions 

and basic data from these sites are in Rittmaster and 

Girouard(1992).

Sampling and Data Collection

Precipitation

Samples of wet deposition were collected with a 

wetfall-dryfall collector (Aerochem Metrics Model 

301 1 ) in New Salem (fig. 4). The collector was operated 

in a field on private property from December 1983 

through March 1985. In April 1985, the collector was 

moved 0.8 km to a site on MDC property. Weekly composite samples were collected each Tuesday to coincide 

with the sampling schedule established by the National 

Atmospheric Deposition Program (Bigelow, 1982). 

Daily volume of precipitation was recorded at the 

National Oceanic and Atmospheric Administration 

(NOAA) site at New Salem (National Oceanic and 

Atmospheric Administration 1983, 1984, 1985b). New 

Salem is between the two basins. Precipitation quantity 

and quality at New Salem was assumed to be representative for the two basins. Local variations in precipitation quantity and quality may introduce errors into the 

hydrologic and chemical budgets for Swift River and 

Fever Brook.

Streamflow

A continuous-record gaging station was established at the outlet of each basin (figs. 4 and 5). Samples 

of stream water were collected approximately weekly 

for chemical analysis; additional samples were collected during some storms and snowmelt periods. 

Chemical data were used to evaluate water-quality 

changes related to time, season, and hydrologic conditions. Instantaneous discharge and stream stage were 

measured concurrently with most sample collections 

during water year2 1984 to establish the stage-discharge 

rating curve. Spot measurements of instantaneous discharge during water year 1985 were made to verify the 

stage-discharge relation.

Records of stream stage were adjusted for effects 

from ice, vegetation, and beaver impoundments, based 

on weather records and field observations. Corrected 

stage records were converted to discharge using a rating 

curve developed from measurements of instantaneous 

discharge over a broad range of stages. Mean discharge 

at each outlet gaging station was calculated at a daily 

time step.

Stream discharge was partitioned into base flow, 

which is the ground-water component, and direct runoff 

that enters the stream system during and shortly after 

precipitation and snowmelt (Hem, 1985). The relative 

proportion of the ground-water component of streamflow was determined by use of the daily mean discharge 

hydrograph and standard graphical separation 

techniques (Davis and DeWiest, 1966).

Water samples were collected at four sites on tributaries of Swift River and at three sites on tributaries of 

Fever Brook Basin during snowmelt, summer low flow, 

and autumn and winter base flows. Analyses of these 

samples were used to evaluate spatial variability of 

water quality related to local bedrock geology, surficial 

geology, and hydrologic conditions in the basin. 

Because the waters were well mixed (specific conductance, pH, and temperature across the channels were 

uniform), except at the Swift River gaging station, grab 

samples were collected at all stream-sampling sites. The 

Swift River gaging station was downstream from the 

confluence of a tributary to the mainstem, and water was 

incompletely mixed (pH and specific conductance

^se of trade names or brand names in this report is for 

identification purposes only and does not constitute endorsement by 

the U.S. Geological Survey.

2The water year runs from Oct. 1 to Sept. 30 and is 

designated by the calendar year in which it ends. Thus, the year 

ending September 30, 1984, is called the "1984 water year."

Methods of Study 9
72°24'

42°32'

422800072233101

422800072232901

422803072231801

01174560

EXPLANATION

DRAINAGE BASIN BOUNDARY 

SUBBASIN DRAINAGE BOUNDARY

Xi OBSERVATION WELL AND NUMBER-Water 

S. levels and water quality were collected 

at these wells

A CONTINUOUS-RECORD GAGING 

m. STAT|ON AND NUMBER

m 1 T^RRI A MISCELLANEOUS STREAMFLOW01 1'»«» MEASUREMENT SITE AND NUMBER

V WATER-QUALITY SAMPLING SITE

422800072232801 D SOIL-WATER-SAMPLING SITE AND NUMBER 

422800072233101 LYSIMETER SAMPLING SITE AND NUMBER

WET-DEPOSITION COLLECTOR AND NUMBER

5,000 FEET

1,000 METERS

CONTOUR INTERVAL 100 FEET 

NATIONAL GEODETIC VERTICAL DATUM OF 1929

NEW SALEM 

423027072204501

FIRST NOAA SITE

BEFORE 

APRIL 1985

Figure 4. Surface-water, ground-water, and soil-water sampling sites. West Branch SwiftRiver Basin, central Massachusetts.

10 Factors Affecting Water Quality and Net Flux of Solutes in Two Stream Basins, Quabbin Reservoir Basin, Central Mass., 1983-85
EXPLANATION

 DRAINAGE BASIN BOUNDARY

 SUBBASIN DRAINAGE BOUNDARY

OBSERVATION WELL AND NUMBER-Water 

levels and water quality were collected 

at these wells

CONTINUOUS-RECORD GAGING 

STATION AND NUMBER

MISCELLANEOUS STREAMFLOWMEASUREMENT SITE AND NUMBER

V WATER-QUALITY SAMPLING SITE

422848072131701 D SOIL-WATER-SAMPLING SITE AND NUMBER

4229090721 21 001 | LYSIMETER SAMPLING SITE AND NUMBER

 422906072130201

*-H 

42°29' 

5,000 FEET

01174050

422906072124301

422848072131701

0 1,000 METERS

CONTOUR INTERVAL 100 FEET 

NATIONAL GEODETIC VERTICAL DATUM OF 1929

Figure 5. Surface-water, ground-water, and soil-water sampling sites. East Branch Fever 

Brook Basin, central Massachusetts.

varied laterally across the channel). Therefore, samples 

were collected at several points across the stream 

channel and composited.

Ground Water and Soil Water

Five monitoring wells cased with polyvinyl chloride (PVC) were sampled for chemical analysis of 

ground water in order to monitor hydrologic and chemical changes in the saturated zone (figs. 4 and 5). Three 

wells were completed in till, and two were completed in 

sand and gravel. Water levels in the wells were measured approximately monthly, and ground-water samples were collected monthly to bimonthly. At least three 

well volumes of water were evacuated from the sand 

and gravel wells before sampling. Because the till wells 

recharged very slowly, sometimes only two well volumes were evacuated from them prior to sampling. Two

types of soil-water collectors were installed: (1) a zerotension lysimeter, referred to as a "soil-water sampler," 

consisting of a 5-m PVC trough oriented with the slope, 

inserted laterally under a 150-mm segment of soil lifted 

gently from one side to minimize disturbance, and (2) a 

negative-tension TIMCO lysimeter with a porous 

Teflon cup, referred to as a "lysimeter." Few soil-water 

samples were collected due to rapid infiltration and 

drainage of water from the silty, permeable soil. Sufficient quantities of water were available for sampling 

only under conditions of high soil moisture, for 

example, during spring snowmelt and directly after 

rainstorms. One soil-water sampler was installed in the 

Swift River Basin; two were installed in the Fever 

Brook Basin (figs. 4 and 5). Two to four samples were 

collected at each location during the study. One site in 

each drainage basin was equipped with an array of three 

lysimeters at three different depths, about 100, 300, and

Methods of Study 11
600 mm below land surface. Water was recovered from 

only the deep lysimeter in the Swift River Basin and 

from the deep and medium depth lysimeters in the Fever 

Brook Basin. Water yield varied among samplers. Some 

sample volumes were sufficient only for pH and specific 

conductance measurements but some volumes were 

sufficient for full chemical analyses (pH, specific 

conductance, major cations and anions).

Sample Handling and Chemical Analyses

Temperature, specific conductance, and pH were 

measured in the field at the time of sample collection, 

except for precipitation samples, which first were 

returned to the laboratory for volume determination and 

melting if necessary. Specific conductance was measured with an Extech digital conductivity meter and pH 

was measured with an Extech model 609 digital pH 

meter equipped with an Orion combination glass pH 

electrode. These instruments were specifically designed 

for measurements in low-conductivity waters.

Samples were filtered, preserved, and chilled in 

the field in accordance with methods recommended by 

the USGS (Fishman and Friedman, 1989). Samples 

were shipped chilled to the USGS laboratory in 

Doraville, Georgia, for chemical analysis. An aliquot of 

each sample was retained for measurement of alkalinity 

in the USGS laboratory in Boston.

Alkalinity was measured by incremental, rather 

than fixed-endpoint titration (Fishman and Friedman, 

1989). The endpoint in the incremental titration method 

is determined as the titrant volume at which the pH 

decreases most quickly with incremental additions of 

titrant. In contrast, fixed-endpoint titration requires acid 

titration of the sample to a fixed pH, usually 4.3 or 4.5. 

Because alkalinity concentration in most water samples 

collected in the study area was low, the threshold of 

buffering was at a significantly higher pH (5.0 to 5.3) 

than that assumed for a fixed-endpoint titration. 

Therefore, the alkalinity measured by incremental 

titration was a more conservative and accurate determination of the buffering capacity of the water than that 

measured in a fixed-endpoint titration.

Concentrations of major ions in all water samples 

were determined by analytical methods outlined by 

Fishman and Friedman (1989). Many of these methods 

were developed for analysis of dilute waters (specific 

conductance less than 100 |j,S/cm) that are typical of the

study area. In addition, total and dissolved concentrations of aluminum, copper, lead, arsenic, vanadium, 

selenium, and mercury were analyzed for selected 

samples.

The original sampling protocol called for filtration 

of all samples through a 0.4-jJ.m pore-size membrane. 

However, Jones and others (1974) found that particulate 

and colloidal aluminum can pass through a 0.4-|Lim 

pore-size filter, causing overestimates of monomeric 

aluminum concentrations, the form of aluminum that is 

most toxic to fish (Driscoll and others, 1980). Therefore, the filter size was changed to 0.1 |Lim. Periodically 

during the first year of sample collection, two aliquots 

of each sample were submitted for analysis of aluminum, one which passed through a 0.4-|Lim filter and one 

which passed through a 0.1-|Lim filter. From 19 split 

samples, aluminum concentrations averaged 123 |Lig/L 

(micrograms per liter) (standard deviation 75 |Lig/L) in 

the 0.4-|Lim filtered samples and 73 jlg/L (standard deviation 65 |Lig/L) in the 0.1-|Lim filtered samples. This was 

a statistically significant difference; probability was less 

than 0.0005 that this difference occurred by chance 

(p<0.0005). Thus, some particulate or colloidal aluminum apparently passed through the larger pore size. 

Aluminum concentrations from 0.1-|Lim filtered samples 

were reported when available, including all samples 

collected after December 1, 1984.

Estimation of Chemical Fluxes Entering and 

Leaving Stream Basins

Chemical Inputs in Precipitation

Loads of major chemical solutes entering the 

drainage basin in wet deposition were determined from 

concentrations of weekly composite samples and precipitation volume corresponding to the sampling period. 

The general equation to determine the weekly load was:

Load = AxBx C,

where

A is concentration of a given solute from a

weekly composite sample, in milligrams

per liter; 

B is the total precipitation recorded for the

period, in inches; and 

C is the constant for converting inches of

precipitation to cubic meters of water per

(1)

12 Factors Affecting Water Quality and Net Flux of Solutes in Two Stream Basins, Quabbin Reservoir Basin, Central Mass., 1983-85
hectare, liters to cubic meters and 

milligrams to equivalents such that load 

units are equivalents per hectare.

An estimate for the weekly load was substituted 

when: (1) sample integrity was compromised due to 

equipment malfunction or vandalism, including 

contamination by leaves, insects, and other dryfall 

material; or (2) sample volume was insufficient for 

chemical analysis. The estimate was made by first calculating a volume-weighted concentration of each 

solute for the 2-week periods before and after the missing week and then multiplying the actual precipitation 

volume for the missing week by the calculated volumeweighted concentrations. This estimation method incorporated potential seasonal variability of solute concentrations in precipitation. Although deposition of the 

acidic components of precipitation was unrelated to 

season (Samson, 1987), the use of 4 weeks of data for 

computing an average was expected to yield a reliable 

estimate of solute load for the missing week.

Chemical Outputs in Streamflow

Relations between solute concentrations and discharge at the Swift River and Fever Brook gaging stations were explored to determine if a sufficiently strong 

relation could be derived to calculate solute loads. A 

concentration/discharge relation uses discharge data, 

which generally were collected at a short enough time 

step to be considered continuous, to compute a chemical 

concentration at any time. This was desirable when 

chemical data were available only from samples collected at widely spaced time intervals. If the relation is 

sufficiently strong, a continuous chemograph can be 

generated with confidence. If the relation is weak, the 

approach is not justified, and loads are best calculated 

using a time-series approach, as described below. 

Success in correlating concentration and discharge can 

be improved by choosing an appropriate regression 

model. Various models can be created by performing 

transformations on the discharge variable, such as that 

used by Johnson and others (1969). Concentration/ 

discharge relations were evaluated with the following 

four linear regression models:

Y = m(X) + b, linear model (model no. 1) (2) 

Y = m[\og(X)] + b log linear model (model no. 2) (3)

Y = m[l/l+|3X] + b, hyperbolic model tested with

eight values of |3 (model no. 3) (4)

Y = m(l/X) + b, inverse model (model no. 4), (5)

where

Y is the response variable representing solute

concentration;

m is the equation coefficient; 

X is the explanatory variable representing

the instantaneous discharge per unit area; 

b is the equation constant; and 

P is an empirical constant.

In addition to calculating the equation coefficient 

and constant for each concentration/discharge model, 

the coefficient of determination (r2) also was calculated. 

The r2 value represents the proportion of the variability 

in the response variable (Y) that is accounted for by the 

model. Analogous to the calculation of chemical loads 

in precipitation, chemical loads in streamflow were calculated as the product of discharge and chemical concentration. Loads were calculated at a daily time step. 

Daily mean discharge was computed from 15-minute 

stage measurements at each gaging station. Daily solute 

concentrations were either computed from concentration/discharge regression models or estimated by the 

time-series method.

Solute concentrations were computed from 

concentration/discharge regression models, using the 

regression equation with the highest r 2 , provided a minimum r2 of 0.40 was achieved. R. Hooper (U.S. Geological Survey, written commun., 1990) recently 

demonstrated that a concentration/discharge model with 

an r2 greater than 0.30 yields a reliable estimate of load. 

However, an r2 of 0.40 was chosen here because it represents a natural grouping in the data among those solutes that were strongly correlated with discharge and 

those that were not. Although the regressions were 

based on the instantaneous discharge associated with 

each solute concentration, daily mean concentrations 

were calculated from daily mean discharge. Depending 

on the nature of the relation, this approximation may 

lead to errors, especially for days on which discharge 

varies. Nonetheless, it is common practice to compute 

daily loads in this manner (R. Hooper, U.S. Geological 

Survey, written commun., 1990).

The time-series method (Dolan and others, 1981) 

was used to estimate daily concentrations when the 

concentration/discharge model had an r2 less than 0.40.

Methods of Study 13
In the time-series method, daily solute concentrations 

were set equal to those measured in the stream sample 

collected nearest in time. Because samples typically 

were collected on a weekly basis, the concentration of a 

solute on the sampling day generally was assigned to 

the days beginning 3 days prior to sampling and ending 

3 days after sampling. The assignment of daily concentration values diverged from this schedule when samples were collected more frequently. As above, daily 

loads were calculated as the product of daily mean 

discharge and the assigned daily concentrations.

Net Fluxes

Chemical loads in precipitation and streamflow 

represent the best estimate of total fluxes of chemical 

solutes entering and leaving the basins. Net flux, the difference between the input and output of a chemical 

solute (Shaffer and Galloway, 1982), indicates whether 

solutes are retained or released from the drainage basin. 

A negative net flux (stream load greater than precipitation load) indicates a net mass transfer of a solute from 

the drainage basin. Negative net fluxes could reflect 

processes in the drainage basin that contribute solutes to 

water, such as mineral weathering (Bricker and others, 

1968; Katz and others, 1985) or biomass decomposition. A positive net flux (stream load less than precipitation load) indicates that a solute introduced in 

precipitation was retained in the drainage basin, for 

example by biological uptake, sorption, ion exchange, 

or mineral precipitation.

Net solute outputs were adjusted to account for 

deicing salts applied to roads passing through the 

basins. In the Swift River Basin, the adjustment was 

based on the assumption that chloride is conservative; 

equivalents of excess chloride (after accounting for 

chloride in precipitation) were balanced by equivalents 

of base cations in the ratio that they are present in the 

salt (mostly sodium). In the Fever Brook Basin, where 

salt application was quantitatively a greater percentage 

of chemical input than in Swift River Basin, this method 

could not be used because of the effect of ion-exchange 

reactions. An alternate method was devised and is 

explained in a later section, "Application of Deicing 

Salts."

HYDROLOGY OF STREAM BASINS

Precipitation

The amount and distribution of precipitation differed greatly from water year 1984 to water year 1985 

(fig. 6). Historically, precipitation at New Salem averages about 100 mm per month, fairly evenly distributed 

throughout the year (National Oceanic and Atmospheric Administration, 1985a). From December 1983 

through July 1984, precipitation was well above average; 338 mm fell in May 1984. This period was followed by a long period of mild to moderate drought, 

during which precipitation was less than average each 

month from August 1984 through July 1985.

Streamflow

In water year 1984, when precipitation was well 

above average, runoff per unit area was significantly 

greater in the Swift River Basin than in the Fever Brook 

Basin (table 1). Total precipitation of 1,546 mm resulted 

in 915 mm of runoff in the Swift River Basin and 

744 mm runoff in the Fever Brook Basin, corresponding to runoff of 59.2 and 48.1 percent, respectively. In 

water year 1985, when precipitation was less than average, runoff was nearly identical in the two basins. 

Runoff from 969 mm of total precipitation was 285 mm 

in the Swift River Basin and 290 mm in the Fever Brook 

Basin, corresponding to runoff of 29.4 percent and 29.9 

percent, respectively. Normalized to a 12-month period, 

average runoff from December 1983 through August 

1985 was 686 mm in the Swift River Basin and 591 mm 

in the Fever Brook Basin. These figures are comparable 

to long-term average annual runoff at two similar 

streams in central Massachusetts, East Branch Swift 

River near Hardwick, and Cadwell Creek near Belchertown, which averaged 551 and 661 mm, respectively 

(Gadoury and others, 1989).

Differences in the magnitude of streamflow from 

1984 to 1985 at the Swift River and Fever Brook gaging 

stations are apparent from the discharge hydrographs 

(fig. 7). Snowmelt and heavy spring rains resulted in 

high flows in 1984. A 5-day rainstorm of 230 mm in late 

May 1984 caused a 50-year flood. Flow decreased in 

both streams from June to mid-October 1984, reflecting 

increased evapotranspiration and little precipitation in 

the summer. Flow generally increased from autumn 

through early spring because of increased precipitation

14 Factors Affecting Water Quality and Net Flux of Solutes in Two Stream Basins, Quabbin Reservoir Basin, Central Mass., 1983-85
350

300

CO 

DC

LLJ

LLJ 250

200

150

Q.

O 

LLJ 

DC 

Q.

100

50

I I I I T

£2 Monthly precipitation during study period 

D Monthly mean precipitation, 1943-80

Dec

1983

Jan Feb Mar Apr May June July Aug Sept Oct Nov Dec

1984

Jan Feb Mar Apr May June July Aug

1985

Figure 6. Mean monthly (1943-80) and monthly precipitation (November 1983 through 

August 1985) at New Salem, Massachusetts.

Table 1. Annual hydrologic budgets for West Branch Swift River and East Branch Fever Brook Basins, 

central Massachusetts

[All units in millimeters, except percentages. Water year 1984 (WY84) represents data collected from December 1983 through September 

1984. Water year 1985 (WY85) represents data collected from October 1984 through August 1985. Total base flow determined by 

graphical techniques (Davis and DeWiest, 1966)]

Water 

year

Precipitation Total 

runoff

Total 

base flow

Percentage of 

precipitation as runoff

Percentage of runoff 

as base flow

WEST BRANCH SWIFT RIVER BASIN

WY84 ............

WY85 ........ ....

Total.... ......

............ 1,546

969

............ 2,515

915 

285 

1,200

464

174 

638

59.2 

29.4 

47.7

50.7 

61.1 

53.2

EAST BRANCH FEVER BROOK BASIN

WY84 ............

WY85 ............

Total..........

........... 1,546

969

2515

744 

290 

1,034

290 

145 

435

48.1 

29.9 

41.1

39.1 

50.0 

42.1

Hydrology of Stream Basins 15
100 f I I I I I 

WEST BRANCH SWIFT RIVER

i i i i i i i i I i I i I I

EAST BRANCH FEVER BROOK

DISCHARGE

l l I I 0.01 l l i l I l l l I I I I I I I

Dec

1983

Jan Feb Mar Apr May June July Aug Sept Oct Nov Dec

1984

Jan Feb Mar Apr May June July Aug

1985

Figure 7. Temporal variation of discharge and base flow, West Branch Swift River and East 

Branch Fever Brook, central Massachusetts, December 1983 to September 1985.

and seasonally low evapotranspiration rates. Discharge 

peaks and total flow were lower in winter, spring, and 

early summer 1985 relative to the same period in 1984.

Discharge at the outlet gaging stations in the Swift 

River and Fever Brook Basins responded rapidly to precipitation, as shown in the annual hydrographs (fig. 7). 

The magnitude of the hydrologic response generally 

was greater at Swift River than at Fever Brook. Particularly during the high-discharge period early in 1984, 

peak daily flows (normalized to basin area as millimeters per day) associated with storms or snowmelt were 

higher at Swift River than at Fever Brook. The initial 

hydrograph recession was more rapid at Swift River 

than at Fever Brook, but the rate of recession slowed 

more quickly at Swift River, so that higher discharges 

were maintained several days after a storm or melt 

period. For example, peak daily discharges from a large 

storm in late May 1984 were 45 mm at Swift River and 

40 mm at Fever Brook. Discharge decreased to less than 

10 mm on the fourth day after peak discharge at Swift 

River, and not until the fifth day after peak discharge at 

Fever Brook. However, discharge decreased to 1 mm on 

the 13th day at Fever Brook and not until the 18th day 

at Swift River. Thus, there is a quick runoff component 

to flow at Swift River that is absent at Fever Brook, but 

subsurface storage also is sufficient in the Swift River 

Basin to sustain a long base-flow recession.

Ground-Water Discharge

The contrasting pattern of hydrograph recession in 

the two basins is attributed to greater subsurface storage 

capacity at Swift River and greater surface storage 

capacity at Fever Brook. At Swift River, a greater 

amount of storm and snowmelt waters infiltrate to 

recharge ground water, and the remaining runoff waters 

leave the basin relatively rapidly. At Fever Brook, the 

extensive areas of wetlands and impoundments attenuate and prolong the discharge peak, but flow decreases 

rapidly after the surface storage is depleted. The sustained higher rate of hydrograph recession at Fever 

Brook than at Swift River results in lower discharges 

when several days elapse without subsequent hydrologic inputs. Moreover, Fever Brook attained much 

lower minimum discharge levels during the summer 

low-flow period; the minimum daily discharge during 

the period of record was 0.02 mm at Fever Brook compared to 0.07 mm at Swift River (fig. 7). Lower minimum flows at Fever Brook relative to Swift River 

resulted in part from the higher evaporation caused by 

more exposed saturated areas. However, minimum 

flows also were lower at Fever Brook during the winter 

months, when evapotranspiration was negligible. This 

is indicative of a lower overall base-flow component at 

Fever Brook relative to that at Swift River.

The hydrograph separation verified the relatively 

greater importance of ground-water discharge (base 

flow) at Swift River. From December 1983 through 

September 1984, base flow was 51 and 39 percent of

16 Factors Affecting Water Quality and Net Flux of Solutes in Two Stream Basins, Quabbin Reservoir Basin, Central Mass., 1983-85
total runoff for Swift River and Fever Brook, respectively, and from October 1984 through August 1985 

base flow was 61 and 50 percent of total runoff in the 

two streams (table 1). The relative percentage of base 

flow in each basin increased during water year 1985 

because precipitation was much lower; a greater percentage of precipitation (snowmelt and rainfall) infiltrated to satisfy soil-moisture deficits, minimizing total 

runoff as streamflow. Although the flashier response of 

Swift River would be expected to result in a lower percentage of base-flow contribution, the impoundments in 

Fever Brook caused higher evapotranspiration of potential base-flow waters, and favored direct stormflow 

runoff by providing an extensive saturated contributing 

area.

Evapotranspiration

The importance of evapotranspiration at Fever 

Brook is illustrated by a comparison of runoff. In water 

year 1985, when precipitation was less than average, the 

two basins had nearly identical runoff (table 1). In water 

year 1984, when precipitation was greater than average, 

runoff was substantially lower at Fever Brook than at 

Swift River. Viewed in another way, the absolute 

amount of evapotranspiration (calculated as the difference between precipitation and runoff, that is, assuming 

no change in storage) at Swift River was nearly the 

same in each water year. This implies that water is 

apportioned first to evapotranspiration demand, and that 

only the excess appears as runoff. At Fever Brook, the 

absolute evapotranspiration was more than 100 mm 

greater in the wetter water year 1984. Because the vegetative demand for water probably was about the same 

in each basin for each water year, the increased evapotranspiration at Fever Brook in water year 1984 was 

attributed to increased evaporation from the greater area 

of open surface water in the wetter conditions of water 

year 1984. Records from two nearby streams, East 

Branch Swift River near Hardwick and Cadwell Creek 

near Belchertown (Gadoury and others, 1984, 1985) 

indicate that water years 1982 and 1983 had greater than 

average discharge. These data discount the possibility 

that the low runoff at Fever Brook in water year 1984 

resulted from increased storage.

CHEMICAL QUALITY OF PRECIPITATION, 

STREAMS, GROUND WATER, AND 

SOIL WATER

Precipitation Quality

Hydrogen ion was the dominant cation in precipitation, contributing 75 percent of total cation charge 

(table 2). The volume-weighted average pH (determined from hydrogen ion equivalents) was 4.23 for 

December 1983 through August 1985. Volumeweighted concentrations of hydrogen ion, sulfate, and 

nitrate averaged approximately two times higher in the 

dry water year 1985 (October 1984 through August 

1985) than in the wet water year 1984 (December 1983 

through September 1984). Concentrations of base 

cations and chloride were about the same each year.

The concentration of hydrogen ion in wet deposition at New Salem was directly proportional to the concentration of sulfate, and to the sum of concentrations of 

sulfate and nitrate (fig. 8). Similar relations of hydrogen 

ion concentration with sulfate and nitrate concentrations have been observed in other studies of chemical

Table 2. Volume-weighted-average concentrations of solutes in wet deposition, New Salem, 

Massachusetts

[Concentrations are given in microequivalents per liter, 

except for precipitation (millimeters) and pH (standard units). 

To compute averages, concentrations less than detection limit 

were assigned a value of one-half the detection limit. Water 

year 1984 (WY84) represents data collected from December 

1983 through September 1984. Water year 1985 (WY85) 

represents data collected from October 1984 through August 

1985]

Concentrations

Solute or 

property

Hydrogen ion......

(pH) 

Calcium...............

Magnesium .........

Sodium. ....... ........

Potassium............

Sulfate.................

Nitrate ............... ..

Chloride..............

Total 

precipitation...

WY84

... 39

(4.41) 

... 4.4

... 3.0

... 8.4

1.0

... 31

... 17.6

... 7.4

...1,546

WY85

88 

(4.05) 

6.3 

2.9 

7.1 

1.3 

63 

38 

7.2

969

Average during period of 

record

58 

(4.23) 

5.1 

3.0 

7.9 

1.1 

43 

25.5 

7.3

2,515

Chemical Quality of Precipitation, Streams, Ground Water, and Soil Water 17
300

= 250

DC DC >E£ 

8P

UJ ULJ

CD O

or y

i

200

100

50

O O 

OOO

oooo o

OQ8DO O 

OOD

B o

ODOO

oooo 

ooo

50 100 150 200 250 300 0 50 100 150 200 250 300

SULFATE CONCENTRATION, IN 

MICROEQUIVALENTS PER LITER

SULFATE PLUS NITRATE CONCENTRATION, 

IN MICROEQUIVALENTS PER LITER

Figure 8. Relations between hydrogen ion concentration and sulfate concentration (A), and hydrogen 

ion concentration and sulfate plus nitrate concentration (fl) in wet deposition, New Salem, 

Massachusetts.

composition of precipitation (Likens and others, 1979; 

Brezonik and others, 1980; Pack, 1980; Raynor and 

Hayes, 1982; Samson, 1987).

In precipitation collected at New Salem, the sum of 

volume-weighted-average concentrations of sulfate 

(43 |ieq/L) and nitrate (25.5 |ieq/L) exceeded the hydrogen ion input by only 10 |ieq/L. Based on the ratio of sulfate to nitrate and the approximate balance of these 

strong acid anions with the hydrogen ion concentration, 

nearly two-thirds of the acidity of the precipitation was 

sulfuric acid, and about one-third was nitric acid. Some 

of the sulfate and nitrate not associated with hydrogen 

ion may have been associated with ammonium (NH4+). 

In the atmosphere, ammonia can neutralize nitrate and 

sulfate aerosols and form the ammonium salts NH4HSO4 

and NH4NO3 (Monahan, 1984). This association also 

was observed by Munger and Eisenreich (1982), who 

found that the geographic distribution of ammonium 

deposition in the eastern United States was similar to that 

of sulfate and nitrate. The pH of pure water in equilibrium with atmospheric carbon dioxide gas at 25°C is 5.7 

(Garrels and Christ, 1965). The pH of natural 

precipitation may differ from 5.7 because of reaction

with dust derived from soil, marine aerosol, volcanic 

gases and ash, and other natural and anthropogenic gases 

and particulates (Gambell and Fisher, 1966; Likens and 

others, 1979; Raynor and Hayes, 1982). Precipitation pH 

lower than 5.0 generally is associated with anthropogenic sources of acidity (Schindler, 1988). Sulfur dioxide and nitrous oxide released as byproducts of fossil 

fuel burning (Monahan, 1984) are converted to sulfuric 

and nitric acid by atmospheric chemical reactions. 

Hydrochloric acid, generally a minor component of acid 

deposition, originates from industrial emission of chlorine gas (Gorham, 1976). Other sources of solutes in precipitation include sea-salt aerosols, soil dust, and fly-ash 

particles from industrial combustion processes. Assuming that natural rain water has a minimum pH of 5.0 

(10 (leq/L H+ ), at least 83 percent of the volumeweighted-average hydrogen ion concentration in wet 

deposition at New Salem (table 2) can be attributed to 

anthropogenic sources.

Variations of volume-weighted solute concentrations in wet deposition in water years 1984 and 1985 

may be attributed to the differences in precipitation 

volumes and patterns during this period (table 2).

18 Factors Affecting Water Quality and Net Flux of Solutes in Two Stream Basins, Quabbin Reservoir Basin, Central Mass., 1983-85
Concentrations of base cations and chloride were very 

similar in the two water years, contrary to the expectation that concentrations would be lower during the 

much wetter year (water year 1984) from dilution. In 

contrast, concentrations of hydrogen, sulfate, and 

nitrate during water year 1984 were less than one-half 

those in water year 1985, resulting in considerably 

greater loads of these solutes in water year 1985 despite 

much less precipitation (see below). These patterns are 

consistent with a higher proportion of coastal storms in 

water year 1984 relative to water year 1985. Coastal 

storms are the primary source of precipitation during 

winter and early spring (Gambell and Fisher, 1966), 

thus greater amounts of the marine-derived solutes, 

such as magnesium, sodium, and chloride, were likely 

introduced by large storms during early 1984. These 

same coastal storms also probably were dilute in the 

acidic components; sulfate, nitrate, and hydrogen ion. 

Risley and Shanley (1994) working at a site near Quabbin Reservoir, also noted that continental storms, which 

tracked over the industrialized midwestern United 

States, were relatively enriched in acidic components in 

comparison to coastal storms, which tracked up the 

Atlantic seaboard.

The volume-weighted mean pH (4.23 as determined from H equivalents) in wet deposition for the 

study period was slightly higher than the pH recorded in 

1982 at a nearby site at Fort River in central Massachusetts (Yuretich and Batchelder, 1988) and in the Adirondack Mountains in New York (Peters and others, 1982). 

However, the pH was somewhat lower than the pH 

recorded in 1982 and 1983 at Turners Falls, Massachusetts (Samson, 1987). Sulfate concentrations in wet deposition at New Salem were comparable to those at 

Turners Falls.

Volume-weighted mean concentrations of sulfate 

and hydrogen ion in wet deposition were significantly 

greater at New Salem than at Hubbard Brook in New 

Hampshire (Driscoll and others, 1989) during the study 

period. The time periods are not directly comparable 

because the Hubbard Brook data are reported for the 

calendar year. However, in 1984, precipitation at New 

Salem had a pH of 4.41 and a sulfate concentration of 

31 n,eq/L, compared to corresponding values at 

Hubbard Brook of 4.47 and 25.5 ^leq/L. In 1985, 

precipitation at New Salem had a pH of 4.05 and a sulfate concentration of 63 p,eq/L, compared to corresponding values at Hubbard Brook of 4.27 and 

34.5 n,eq/L. Higher concentrations of these acidic

components at New Salem may be a consequence of its 

location closer to industrial sources of anthropogenic 

acidity than was the case at Hubbard Brook. Concentrations of base cations in wet deposition at New Salem 

were nearly two times greater than those at Hubbard 

Brook during the two years. Base cations in precipitation counter the capacity of acidic deposition to 

consume alkalinity in surface waters (Driscoll and 

others, 1989).

Precipitation also was analyzed for trace elements. 

Concentrations of dissolved copper and lead in wet deposition were variable but generally less than 5 \lgfL. 

Based on analyses from water year 1984 only, concentrations of vanadium ranged from less than 1 to 5 M£/L; 

concentrations of selenium and mercury generally were 

equal to or less than the detection limits of 1 and 

0.1 H,g/L, respectively.

Stream-Water Quality

Major-Ion Chemistry

Flow-weighted-average concentrations were similar for many of the major dissolved chemical solutes in 

Swift River and Fever Brook during the study period 

(table 3). Each basin had low buffering capacity, with 

average alkalinity less than 30 p,eq/L. Hydrogen ion and 

nitrate averaged near 2 \ieq/L in each basin, despite 

much higher concentrations in precipitation. Flowweighted average concentrations of sodium and chloride were higher at Fever Brook because of the higher 

amount of applied road salt in that basin.

Concentrations of most dissolved chemical solutes 

in the streams had pronounced temporal variations in 

response to storms and to seasonal changes (figs. 9 and 

10). Alkalinity, silica, base cations, and chloride 

attained maximum concentrations during low flow in 

summer. At Fever Brook, concentrations of these 

solutes peaked later in the autumn, after the period of 

minimum discharges. Concentrations for these solutes 

reached a minimum during peak flows in spring. The pH 

and alkalinity reached minimum values during the May 

1984 flood. The pH ranged from 5.1 to 6.8 at Swift 

River and from 5.4 to 6.3 at Fever Brook; alkalinity 

ranged from 1 to 136 p,eq/L at Swift River and from 5 to 

136 p,eq/L at Fever Brook.

Chemical Quality of Precipitation, Streams, Ground Water, and Soil Water 19
Table 3. Flow-weighted-average concentrations of chemical solutes and runoff data, West Branch Swift 

River and East Branch Fever Brook, central Massachusetts

[Concentrations are given in microequivalents per liter unless otherwise noted. Water year 1984 (WY84) represents data 

collected from December 1983 through September 1984. Water year 1985 (WY85) represents data collected from October 

1984 through August 1985. Average concentration during base-flow conditions: Base-flow samples taken from Rittmaster and 

Girouard (1992). (imol/L, micromole per liter; mm, millimeter. -, no data]

Concentrations Solute or 

property WY84 WY85 Average during Average during baseif J TV A. UT VT J. \J+J i /» i ft i* period of record now conditions 

WEST BRANCH SWIFT RIVER (gaging station 01174565)

Hydrogen ion.................................... 2~6 O8 22 O7

pH...................................................... 5.58 6.11 5.66 6.19

Calcium............................................. 108.1 117.4 110.3 104.0

'104.0 '113.2 406.2

Magnesium........................................ 37.0 39.9 37.7 40.0

'36.5 '39.4 '37.2

Sodium.............................................. 123.6 135.9 126.5 140.0

'47.9 '59.9 '50.8

Potassium.......................................... 9.4 10.2 9.6 10.0

Alkalinity.......................................... 26.2 36.3 28.6 33.0

Sulfate............................................... 139.9 147.9 141.8 150.0

'138.5 '146.5 '140.4

Nitrate............................................... 1.6 3.2 2.0

Chloride............................................ 91.5 103.8 94.4 99.0

'12.5 '24.6 '15.4

Silica (nmol/L).................................. 102.9 112.1 105.1 102.0

Runoff (mm)..................................... 915 285 1,200

Base flow2 (mm)................................ 464________174____________638_____________--______

EAST BRANCH FEVER BROOK (gaging station 01174050)

Hydrogen ion.................................... 2.1 1.4 1.9 1.2

pH...................................................... 5.69 5.86 5.73 5.94

Calcium............................................. 97.2 123.7 104.6 120.0

'68.5 '106.0 '79.0

Magnesium........................................ 50.9 66.0 55.1 60.0

'38.4 '59.7 '44.4

Sodium.............................................. 206.4 256.7 220.5 270.0

'42.5 '38.1 '41.3

Potassium.......................................... 13.8 18.4 15.1 18.0

Alkalinity.......................................... 24.7 30.2 26.3 28.0

Sulfate............................................... 132.8 131.9 132.6 146.0

'129.3 '127.9 '128.9

Nitrate............................................... 1.3 5.4 2.5

Chloride............................................ 221.3 258.6 231.8 235.0

'15.4 '24.2 '17.8

Silica (nmol/L).................................. 79.6 71.2 77.3 83.0

Runoff (mm)..................................... 744 290 1,034

Base flow2 (mm)................................ 290________145____________435_____________»______

'Concentration after deducting deicing-salt contributions (see section "Adjustment of Chemical Fluxes"). 

2 Base flow determined by graphical techniques (Davis and DeWiest, 1966).

20 Factors Affecting Water Quality and Net Flux of Solutes in Two Stream Basins, Quabbin Reservoir Basin, Central Mass., 1983-85
100

10

Oso: 1

Z ^j LU

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BASE FLOW

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180

120

60

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60

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30

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SPECIFIC CONDUCTANCE

I I I I I I I I I I I I I I I I

i i i i i i i i i i i i i i

Dec

1983

Jan Feb Mar Apr May June July Aug Sept Oct Nov Dec

1984

Jan Feb Mar Apr May June July Aug

1985

Figure 9. Temporal variation of runoff, specific conductance, and concentrations of selected 

chemical solutes. West Branch Swift River, central Massachusetts.

Chemical Quality of Precipitation, Streams, Ground Water, and Soil Water 21
0.01

I I I I I I I I I I I I I I

HYDROGEN ION

i i i i i i i i i i

F<CC 

< CC LU 

CC (5 I- £°^

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DISSOLVED ORGANIC CARBON

iii

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100

50

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90

45

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_ ALKALINITY

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SULFATE

i i i i i

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i i i

Dec

1983

Jan Feb Mar Apr May June July Aug Sept Oct Nov Dec

1984

Jan Feb Mar Apr May June July Aug

1985

Figure 9. Temporal variation of runoff, specific conductance, and concentrations of selected 

chemical solutes. West Branch Swift River, central Massachusetts Continued.

22 Factors Affecting Water Quality and Net Flux of Solutes in Two Stream Basins, Quabbin Reservoir Basin, Central Mass., 1983-85
SPECIFIC CONDUCTANCE

180

120

60

0

100

80

60

40

20

CALCIUM

MAGNESIUM

i i i

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Dec

1983

Jan Feb Mar Apr May June July Aug Sept Oct Nov Dec

1984

Jan Feb Mar Apr May June July Aug

1985

Figure 10. Temporal variation of runoff, specific conductance, and concentrations of selected 

chemical solutes, East Branch Fever Brook, central Massachusetts.

Chemical Quality of Precipitation, Streams, Ground Water, and Soil Water 23
_ _

a. iii Q 

Q2tr

Z jUJ 

^ _i£L

cc ~

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i i i i i i i

i i i i i i i i i i i i i i i i i i i i

i i i i i i i i i i i i i i i _ i i i i i

Dec

1983

Jan Feb Mar Apr May June July Aug Sept Oct Nov Dec

1984

Jan Feb Mar Apr May June July Aug

1985

Figure 10. Temporal variation of runoff, specific conductance, and concentrations of selected 

chemical solutes, East Branch Fever Brook, central Massachusetts Continued.

24 Factors Affecting Water Quality and Net Flux of Solutes in Two Stream Basins, Quabbin Reservoir Basin, Central Mass., 1983-85
The dilution of silica was much more significant at 

Fever Brook, suggesting the possibility of silica uptake 

by spring diatom blooms in the impoundments. Patterns 

of potassium concentrations were similar to those of the 

other base cations, with the exception that the maximum 

concentration in autumn was more pronounced, probably as a result of decomposing leaves. Concentrations of 

dissolved organic carbon (DOC) in Swift River 

increased markedly in association with snowmelt and 

rainfall runoff, and in autumn coincident with the peak 

in potassium. At Fever Brook, DOC progressively 

increased through the summer, probably as a result of 

decomposition of organic matter in the impoundments. 

Concentrations of DOC peaked at Fever Brook in 

autumn, also coincident with the peak in potassium concentration, suggesting that leaf decomposition further 

increased DOC concentrations.

Sulfate concentrations were higher and less variable at Swift River than at Fever Brook. At Fever 

Brook, sulfate decreased during low flow in summer 

and early autumn, whereas at Swift River there was no 

apparent change. Concentrations of nitrate in the 

streams generally were low compared to those in precipitation, but during snowmelt runoff in 1985, concentration of nitrate peaked at nearly 20 (Aeq/L in Swift 

River and exceeded 35 (Aeq/L in Fever Brook.

The effect of road deicing salts was evident in the 

high sodium and chloride concentrations in both basins, 

particularly in Fever Brook. Before adjustments for 

deicing salts, the total flow-weighted average base 

cation concentration was 284 (Aeq/L in Swift River and 

396 (Aeq/L in Fever Brook; after adjustments, the concentrations were 204 and 180 (Aeq/L, respectively 

(calculated from table 3). The distribution of adjusted 

cation concentrations was somewhat different in the 

two basins. Fever Brook had moderately higher potassium and magnesium concentrations than Swift River, 

whereas Swift River had higher sodium and calcium 

concentrations. When comparing the concentrations for 

the two water years at each site, Fever Brook had markedly higher concentrations of calcium and magnesium 

in water year 1985, the drier of the two years, whereas 

there was little difference in calcium and magnesium 

concentrations between the two water years at Swift 

River. Despite the similarity in base-cation concentrations, the average silica concentration was about 35 

percent higher in the Swift River than in Fever Brook.

After adjustment for salt-derived chloride, sulfate 

was the dominant anion in each basin, 140.4 (Aeq/L at 

Swift River and near 128.9 (ieq/L at Fever Brook. Sulfate accounted for nearly 75 percent of the anion charge. 

Bicarbonate, assumed equal to alkalinity, was the 

second most dominant anion. Background chloride concentrations, assumed to be derived only from the atmosphere, were about one-half the bicarbonate 

concentration in each basin; nitrate was a very minor 

component.

Stream water at headwater sites and tributaries in 

the two basins (figs. 4 and 5) generally was more dilute 

and more poorly buffered than stream water at the outlet 

gaging stations (table 4). In general, solute chemistry 

did not vary markedly among the tributary sites in each 

basin. An exception was site 01174564 (fig. 4), the tributary that drains the area of gabbro bedrock in the southeast part of the Swift River Basin. Mean pH at this 

tributary site was 6.88 compared to a pH range of 5.07 

to 5.58 at the other Swift River Basin tributaries. Basecation concentrations at this tributary were higher by a 

factor of 3, and alkalinity by a factor of 10, relative to 

the other Swift River tributary sites.

Seasonal patterns of solute concentration variations at the tributary and headwater sites were similar to 

those at the outlets. Dissolved solute concentrations and 

pH generally increased during summer base-flow conditions in summer and autumn and decreased during 

high-flow conditions in spring (fig. 11). Although variations in solute concentration generally were similar 

among tributaries in each basin, consistent differences 

were apparent between the inlet and outlet of Brooks 

Pond, an impoundment on Fever Brook. Concentrations 

of calcium, alkalinity, and silica, as well as pH, generally were greater at the site upstream of the pond 

(01174035) than at the site downstream of the pond 

(01174040) (fig. 5). The concentration difference was 

greatest in summer, particularly for silica, which 

reached a minimum concentration at the downstream 

site in summer (fig. 11).

Aluminum Chemistry

Concentration of aluminum at the Swift River and 

Fever Brook outlet gaging stations ranged from less 

than 10 to 280 (Ag/L (figs. 9 and 10). Concentrations of 

aluminum and hydrogen ion were highest during high 

flows in late winter and spring runoff. This pattern was 

contrary to most relations between dissolved solutes

Chemical Quality of Precipitation, Streams, Ground Water, and Soil Water 25
8

o

35

I

O. 

(Q

I

O

Q 

Q.

CO

O

I

O 

g

a 

a3'

2.

9

I

Table 4. Summary of mean pH and chemical solute concentrations at surface-, ground-, and soil-water sam

Swift River and East Branch Fever Brook Basins, central Massachusetts

[Concentrations are in microequivalents per liter, unless otherwise noted. |ig/L, microgram per liter; mg/L, milligram per liter; |0.mol/L, m

<, actual value is less than value shown]

Site and number

Swift River near Cooleyville (01174555).........................

Swift River at Cooleyville (01174560).. ...........................

Swift River tributary (01174563) .....................................

Swift River tributary (gabbro bedrock) (01174564).........

Swift River outlet gaging station (01174565)...................

Fever Brook tributary above pond (01174035) ................

Fever Brook tributary below pond (01174040)................

Fever Brook at West Road (01174045) ............................

Fever Brook outlet gaging station (01174050).................

HydropH gen 

ion

.. 5.07 8.5

.. 5.44 3.6

.. 5.58 2.5

.. 6.88 .1

.. 6.00 1.0

.. 6.02 1.3

.. 5.51 3.1

.. 5.70 2.0

.. 5.82 1.5

Calcium

SURFACE

71 

81 

76 

216 

114

101 

94 

101 

118

Magnesium

WATER

24 

25 

26 

74 

39

52 

51 

57 

62

Sodium

82 

85 

56 

307 

132

148 

242 

283 

240

Potassium

7 

8 

7 

20 

11

18 

14 

18 

18

Alkalinity

3 

14 

17 

196 

46

42 

21 

37 

42

Sulfate

104 

133 

115 

153 

152

122 

116 

106 

129

Chloride

55 

55 

26 

333 

110

150

255 

323 

253

GROUND WATER

Swift River till well (422800072232901)........................,

Swift River sand and gravel well (422803072231801)...., 

Fever Brook till well (422906072124301).......................,

Fever Brook sand and gravel well (422906072130201) .., 

Fever Brook Knault's well (till) (422910072120501)......,

5 73 19

.. 5.73 1.9 

.. 7.56 <.l

.. 6.00 1.0

.. 7.25 .1

110 

128 

1,261 

171 

276

63 

40 

210

75 

247

69

83 

187 

137 

345

16 

20

233 

22 

120

40 

116 

1,245 

252 

730

183 

138 

711 

226 

94

26

35 

52 

67 

86

SOIL WATER

Swift River soil water (422800072232801) .....................

Swift River deep lysimeter (422800072233101)..............,

Fever Brook fox den soil water (422848072131701).......,

Fever Brook soil water (422901072121201)....................,

Fever Brook deep lysimeter (422909072120901)............,

Fever Brook medium lysimeter (422909072121001)

.. 5.56 2.7

.. 5.26 5.5

.. 5.52 3.0

.. 5.01 9.7

.. 4.91 12.2

4.67 21.2

192

127 

142 

22 

95 

92

42

38 

19 

61 

60

57 

78 

25 

55 

168 

174

130 

12 

253 

4 

11 

13

65

82

78

23

193 

196 

203 

161 

141 

141

51

47 

49

233 

247

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Dec

1983

Jan Feb Mar Apr May June July Aug Sept Oct Nov Dec

1984

EXPLANATION

Jan Feb Mar Apr May June July Aug

1985

 p Swift River near Cooleyville (Station Number 01174555)

 O Swift River at Cooleyville (Station Number 01174560)

 - -A- - - Swift River tributary 1 (Station Number 01174563)

 x -- Swift River tributary 2 (Station Number 01174564)

Figure 11. Temporal variation of pH and concentrations of selected chemical solutes, tributaries 

of West Branch Swift River (A) and East Branch Fever Brook (B), central Massachusetts.

Chemical Quality of Precipitation, Streams, Ground Water, and Soil Water 27
Q.

i i i i i i i i i i i i i

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 4---t -r

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Dec

1983

B

Jan Feb Mar Apr May June July Aug Sept Oct Nov Dec

1984

Jan Feb Mar Apr May June July Aug

1985

EXPLANATION

 Tributary above Brooks Pond (Station Number 01174035)

 Fever Brook below Brooks Pond (Station Number 01174040)

. _ _ Fever Brook at West Road (Station Number 01174045)

Figure 11. Temporal variation of pH and concentrations of selected chemical solutes, tributaries 

of West Branch Swift River (A) and East Branch Fever Brook (B), central Massachusetts 

Continued.

28 Factors Affecting Water Quality and Net Flux of Solutes in Two Stream Basins, Quabbin Reservoir Basin, Central Mass., 1983-85
and discharge in which solute concentration decreased 

as discharge increased. Concentrations of aluminum 

and hydrogen ion clearly were affected by high-flow 

events. At Swift River, baseline concentrations of aluminum and hydrogen ion were somewhat lower than 

those at Fever Brook, but episodic increases in concentration were more frequent and greater in magnitude. 

Concentrations of dissolved aluminum peaked (greater 

than 250 (ig/L) during the May 1984 flood at Swift 

River and during early snowmelt periods at Fever 

Brook.

At Swift River, aluminum concentrations generally 

were less than 100 (leq/L, but increased to near 

300 |Lig/L in response to storm runoff and snowmelt in 

winter and spring (fig. 9). At Fever Brook, aluminum 

concentrations ranged from 0 to 150 (leq/L, with less 

frequent increases to near 300 (ig/L; there was no distinctive seasonal pattern (fig. 10). Because aluminum 

concentration increases tend to be episodic, the weekly 

sampling in this study probably does not adequately 

describe the frequency and magnitude of the increases.

However, the apparent higher responsiveness of aluminum concentrations to increased flows at Swift River 

was consistent with the rapid hydrologic response of the 

stream; spikes in aluminum concentrations generally 

are associated with water that enters streams quickly 

along shallow flow paths (McAvoy, 1989).

High aluminum concentrations in surface water, 

ground water, and soil water in both basins generally 

were associated with low pH (fig. 12). This was particularly evident at tributary sites in the Swift River Basin. 

For example, after the 230-mm rainstorm in May 1984, 

pH at the headwater tributary sites ranged from 4.7 to 

4.8, and aluminum concentration ranged from 260 to 

290 (ig/L (fig. 11). In contrast, during the same period at 

the tributary draining the gabbro subcatchment, the pH 

was 6.5 and the aluminum concentration was 110 (ig/L.

Aluminum concentrations in tributary streams 

generally were greater at Swift River sites than 

at Fever Brook sites (table 4). However, aluminum 

concentrations were greater at Fever Brook sites during

GC 

LU

GC 

LLJ 

Q.

CO

GC 

O 

O 

GC 

O

Z

o

CC

LLJ

O

o 

o

Z

2

D

700

600

400

300

200

D SURFACE WATER

O GROUND WATER

A SOIL WATER

5.0 5.5 6.0 6.5 7.0 

pH, IN STANDARD UNITS

7.5 8.0 8.5

Figure 12. Relations between aluminum concentrations and pH in surface water, ground 

water, and soil water, West Branch Swift River and East Branch Fever Brook, central 

Massachusetts.

Chemical Quality of Precipitation, Streams, Ground Water, and Soil Water 29
summer low flow. Aluminum concentrations at the 

uppermost sites in both basins [01174555 in Swift River 

Basin (fig. 4) and 01174035 in Fever Brook Basin 

(fig. 5)] were greater than at downstream sites during 

most sampling periods. At Fever Brook, aluminum concentrations varied considerably but generally were uniformly less than 50 |o,eq/L throughout the basin during 

base flow. Concentrations of aluminum at Swift River 

Basin tributary sites ranged from less than 10 to 

290 (ig/L. At Swift River tributary sites 01174560 and 

01174563, aluminum concentrations were relatively 

constant near 150 |J,g/L. At site 01174564, the tributary 

that drains the gabbro area, aluminum concentrations 

were significantly lower.

Trace Elements

In general, total and dissolved concentrations of 

the trace elements copper, lead, arsenic, selenium, and 

mercury in stream samples were less than standards outlined by the U.S. Environmental Protection Agency 

(1986) for domestic, aquatic, and irrigation use. Total 

and dissolved concentrations of copper ranged from 0.2 

to 13 (J,g/L. Total and dissolved concentrations of lead 

ranged from 0.1 to 13 (o,g/L, but the concentrations generally were less than 2 (ig/L, much less than the domestic use standard of 50 (J,g/L. Maximum concentrations 

of arsenic and selenium were 1 (o,g/L, which is the analytical detection limit. Maximum concentration of mercury was 0.9 (J,g/L, but concentrations of most samples 

were less than 0.1 (o,g/L, the analytical detection limit.

Ground-Water and Soil-Water Quality

At the two Swift River wells, ground water was 

relatively poorly buffered as indicated by the relative 

low pH's (table 4). Although silica concentrations were 

somewhat elevated, alkalinity and base-cation concentrations were in the same range as surface waters. In 

ground water at Fever Brook, however, concentrations 

of nearly all solutes were elevated relative to surface 

water. Ground water from the Fever Brook till well, in 

particular, had alkalinity and calcium concentrations 

greater than 1,000 |neq/L. Coupled with the relatively 

low silica concentration, the chemistry at this well is 

suggestive of carbonate weathering, though no carbonates have been found in the region. This well also had 

unusually high sulfate concentrations, indicative of 

sulfide weathering. In contrast, ground water at the 

other till well at Fever Brook (Knault's well) is silicarich and sulfate-poor. Water at this well is high in alkalinity and base cations and the chemical composition 

seems to be controlled by silicate weathering. The high 

solute concentrations in these waters indicates that only 

a small amount of this water type may contribute to 

streamflow. Ground-water chemistry at the sand and 

gravel well at Fever Brook is similar to that at the Swift 

River wells, although somewhat more enriched in silica, 

alkalinity, and base cations, which are probable 

weathering products.

Soil waters in both basins were poorly buffered, 

low-pH waters enriched in aluminum (table 4). In general, these waters reflect incipient contact of acidic precipitation with the surficial soil; sulfate concentrations 

were nearly equal to or somewhat higher than those in 

precipitation; varying amounts of silica were derived 

from soil contact; and aluminum and DOC were derived 

most likely from the forest floor. Alkalinities were comparable to those in surface water, despite the low pH and 

high aluminum concentrations. This is attributed to the 

presence of organics. In the normal course of chemical 

evolution of soil water to ground or surface water, the 

organic matter will oxidize, causing an increase in 

alkalinity and a decrease in aluminum.

CHEMICAL FLUXES ENTERING AND 

LEAVING STREAM BASINS

Chemical Input Loads in Precipitation

Loads of hydrogen ion, sulfate, and nitrate were 

greater in water year 1985 than in water year 1984, 

despite the much lower precipitation in water year 1985 

(table 5). Loading of base cations and chloride was 

greater in the wetter year because concentrations of 

these solutes vary little with precipitation amount. 

Occasionally, particularly when precipitation volume 

was high, solute concentrations in weekly samples were 

less than the detection limit of the analytical method. In 

these cases, solute concentrations were assumed to be 

one-half the detection limit. If this assumption is in 

error, the total input fluxes of chloride may be in error 

by a maximum of 48 percent for sodium, 10 percent for 

chloride, and 5 percent for nitrate. Other solutes are 

relatively unaffected by an error in the assumption.

Loadings of hydrogen ion and sulfate in wetdeposition samples at New Salem generally were 

greater during the summer and early autumn compared

30 Factors Affecting Water Quality and Net Flux of Solutes in Two Stream Basins, Quabbin Reservoir Basin, Central Mass., 1983-85
Table 5. Monthly loads of chemical solutes in wet deposition. New Salem, Massachusetts

[Loads are given in equivalents per hectare, except for precipitation (millimeters). Water year 1984 represents data collected from 

September 1984. Water year 1985 represents data collected from October 1984 through August 1985. Totals were rounded]

o

lemical Fl

X

8

m

t

<Q

Q

a.

r1 

<Q

Stream E

0

Month

Dec. 1983

Jan. 1984

Feb.

Mar.

Apr.

May

June

July

Aug.

Sept. 

Total. ................

Oct. 1984

Nov. 

Dec. 

Jan. 1985

Feb. 

Mar.

Apr.

May

June 

July

Aug. 

Total.................

Total, water years 

1984-85.........

Hydrogen 

ion

36.9

42.4

67.9

75.6

53.7

98.7

36.5

111

25.1

59.3 

607

66.5

17.7 

78.4 

26.0

34.7 

71.1

44.1

64.3

114 

110

227 

854

1,461

Calcium

6.2

4.2

7.8

9.0

6.8

22

2.4

6.8

1.0

2.2 

68

2.2

.4 

3.4

2.2

7.0 

7.8

13.8

4.8

7.4 

'3.1

9.0 

'61

430

Magnesium

11.2

4.7

40.3

'3.0

4.9

'4.9

2.6

'8.6

4.1

1.6

4.5

3.0 

3.0

.7

4.3 

'2.1

5.4

5.4

3.2 

1.0

4.7 

'28

'75

Sodium

WATER YEAR

'38

42

'20

44

'6.3

46

1 6.6

42

4.8

'2.8 

430

WATER YEAR

'3.7

'8.0 

'6.8 

'2.1

'8.8 

'7.9

'8.0

'5.5

'6.0

'3.3

'8.0 

'68

498

Potassium

1984

4.8

3.1

1.3

1.3

.6

4.5

.6

1.6

.2

.4 

45

1985

0.7

.4 

3.7 

.9

.7 

.9

1.3

.5

1.5 

1.3

.9 

13

28

Sulfate

35.6

21.4

3.8

43.4

41.8

86.4

29.6

93.2

17.6

50.8 

424

50.4

10.8 

33.4 

15.2

17.4 

38.0

39.8

46.4

107.2 

72.0

179 

610

1,034

Nitrate

44.5

28.7

21.8

42.5

19.3

46.3

48.8

41

9.9

28.9

'272

'41.6

8.0 

19.4

'3.5

6.1 

16.8

68.8

35.8

56.5 

44.5

'68.2 

'369

'641

1 Solute concentration was less than detection limit for at least 1 week of the month. Load was calculated assuming a concentrat

limit (see text, page 30).
to other seasons (table 5). The seasonal pattern of maximum loading in summer and minimum loading in 

winter for hydrogen ion and sulfate in precipitation is 

common (Likens and others, 1979; Raynor and Hayes, 

1982; Suarez and Jones, 1982), and is attributed to 

annual cycles of wind direction and air mass velocity. 

The concentration/volume relation, in which high solute 

concentrations are associated with low precipitation 

volume (Raynor and Hayes, 1982), causes deviations 

from this annual cycle. For example, two low-volume 

wet-deposition samples from early April 1985 had 

hydrogen ion concentrations among the highest measured during the study. Loadings of acidic and basic 

components in wet deposition at New Salem probably 

have decreased in recent years, based on decreasing 

trends at Hubbard Brook (Driscoll and others, 1989) 

and on the recent decline in emissions of sulfur dioxide 

in the northeastern United States (Smith and Alexander, 

1983).

Chemical Output Loads in Streamflow

Concentration-Discharge Relations

As the first step in the output flux calculations, the 

concentration-discharge models described in the 

"Methods of Study" section were applied for all major 

solutes analyzed in each basin (table 6). For nearly all 

constituents, coefficients of determination (r 2) were 

greater at Swift River compared to those at Fever 

Brook. Based on a minimum acceptable r 2 of 0.40, 

models could be used to calculate concentration from 

discharge for hydrogen ion, magnesium, sodium, potassium, and alkalinity at Swift River, but could be used 

only for alkalinity at Fever Brook. Concentrations of 

major cations at Fever Brook, and concentrations of all 

anions except bicarbonate at both sites, correlated 

poorly with discharge.

The concentration/discharge regression analysis 

was done prior to any adjustment of concentrations or 

loads for deicing salts. Salts enter the ground-water 

system and are released throughout the year, thus it is 

possible to have a significant correlation between discharge and base-cation concentrations throughout the 

year, despite the fact that deicing salt is applied only in 

winter. However, the generally poor correlations at 

Fever Brook may be related to the relatively greater 

effect of deicing salts in that basin.

At Swift River, concentrations of solutes derived 

primarily from weathering and ion exchange (base cations, alkalinity, and silica) were inversely related to discharge; that is, concentrations were at a maximum 

during low flow and at a minimum during high flow 

(fig. 13). For example, calcium concentration had a 

highly significant inverse relation to log discharge. In 

contrast, concentrations of sulfate, nitrate, and chloride, 

which were controlled by loadings in atmospheric deposition and deicing salts, were weakly correlated with 

discharge. There was a significant inverse relation 

between pH and discharge at Swift River. Likewise, 

alkalinity varied inversely with discharge. Sulfate concentrations were relatively constant; there was little 

relation of sulfate concentration with flow except for a 

slight dilution at high flows.

At Fever Brook, alkalinity was the only solute that 

was significantly correlated with discharge (r 2=0.69). 

Although alkalinity generally is regarded as a weathering product, the lack of significant concentrationdischarge relations for the other solutes indicates that 

the significant relation for alkalinity was related to some 

process other than weathering, most likely biologic production of alkalinity in impoundments. Alkalinity 

increased during summer and autumn as flow decreased 

and biological activity increased. Other solutes correlated with discharge in different parts of the flow regime 

at Fever Brook. Calcium correlated inversely with discharge at high discharge. Sulfate increased with discharge at low discharges but there was no relation at 

moderate or high discharge.

Monthly Solute Fluxes in Streamflow

Monthly stream loads were calculated for December 1983 through August 1985 (table 7) using either the 

linear regression models or the time-series method. 

Variation in monthly load of each major chemical solute 

analyzed was at least ten-fold. In general, these variations were associated with a similar magnitude of 

change in monthly runoff, an indication that monthly 

loads were primarily a function of monthly runoff.

Net Solute Fluxes

Net fluxes of major solutes in the two drainage 

basins were calculated for the study period (table 8). 

Uptake of hydrogen and nitrate in the two drainage 

basins was significant, as indicated by the large positive

32 Factors Affecting Water Quality and Net Flux of Solutes in Two Stream Basins, Quabbin Reservoir Basin, Central Mass., 1983-85
O

<Q 

Q 

Q.

<Q

Table 6. Regression-model parameters for specific conductance and major chemical solutes in West Branch 

Branch Fever Brook, central Massachusetts

[Constituents are given in microequivalents per liter unless otherwise noted. Units of response variable used in regression are in cu

mile; |iS/cm2 , microsiemen per square centimeter at 25 degrees Celsius; |imol/L, micromole per liter; , equation does not have a 

Regression-model 

parameters

Specific 

conductance 

(|iS/cm2)

Hydrogen 

ion

Calcium Magnesium Sodium Potassium Alkalinity Sulfate N

WEST BRANCH SWIFT RIVER

Regression model No. 1

Slope (ra)

y-intercept (b)

Beta (P)

Coefficient of

determination (r 2)

2

-3.92

36.93

-

.67

3

-11.6

11.72

.0316

.84

2

-13.6

119

~

.77

2

-4.23

40.4

~

.71

2

-18.1

138

~

.62

3

34.2

9.11

31.6

.64

3

156

21.9

10.0

.48

1

-.75

149

-

.17

~

EAST BRANCH FEVER BROOK

Regression model No. 1

Slope (ra)

y-intercept (b)

Beta (P)

Coefficient of

determination (r 2)

3

34.5

19.9

.0316

.40

1

.03

1.38

~

.18

3

68.4

61.9

.10

.30

3

34.4

34.1

.10

.26

3

115

146

.10

.24

3

9.19

11.8

.316

.13

3

4.86

1.08

10.0

.69

3

-203

145

31.6

.34

-

1 Model numbers are as follows:

1 Linear model Y = m(X) + b,

2 Semilog model Y= ra[log(X)]+ b,

3 Hyperbolic model Y= ra[l/(l+pX)] + b,

4 Inverse model Y= m(\IX) + b,

where Y is the response variable representing solute concentration; 

m is the equation coefficient;

X is the explanatory variable representing the instantaneous discharge per unit area; 

b is the equation constant; and 

P is an empirical constant.
TlaIO

c Q

 ? 

Q 

g. aXoII«Q

CD 

i. 

</> I1

Q 

CT

a n

s? I

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(D

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CD

(D Q

0.5

between diiMassachuse

-jo

c/j zr

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<Q

(DQD

Q. XOQOc" 3

DISCHAF

>A/ Om

^. O

C 

00o~n 

m mH

"Dm

COm0

Q 0

CALCIUM CONCENTRATION, IN 

MICROEQUIVALENTS PER LITER

o ro ^ i OOOi

pH, IN STAN

00

o
I

(Q Q

Q.

(Q

CD 

§.

Sf 

*S

O Cd

-^ 12:

Is

Q 0 

O 0 D- D

£ Q 

CD w

CD

c Q.

CD T5 

Q. I

O 

Q Oc' 3Q

D 

Q.

COC

 h

Q 

0 Q

CO

D 

CO 0

3D 

Q moc

CD 

O 

Tl

m m

TJ m

3D 

CO

m 

o Oz

D 

TJm

3D 

COOC

3Dmm

§

SULFATE CONCENTRATION, IN 

MICROEQUIVALENTS PER LITER

8 8

ALKALINITY CONC

MICROEQUIVALE

D 
c

Q

a 

2

I

$

§

Q 

I

3

S

sCo

do 

en

Table 7. Estimates of monthly chemical loads in streamflow and monthly runoff, West Branch Swift River and 

central Massachusetts

6" [Units are in equivalents per hectare, except for silica (moles per hectare) and runoff (millimeters). West Branch Swift River: Loads for hydrogen 

*? potassium, and alkalinity were calculated using regression analysis. Sulfate, chloride, nitrate, and silica were calculated by time-series method. Eas

as alkalinity were calculated using regression analyses. Hydrogen ion, calcium, magnesium, sodium, potassium, sulfate, chloride, nitrate, and silica wer

o. Water year 1984 represents data collected from December 1983 through September 1984. Water year 1985 represents data collected from October 

^ Month

Q^

<D 

Q

3

| Dec. 1983

| Jan. 1984

3 Feb. 

* Mar.

J£ Apr.

S. May

SJ June 

i1 July

w Aug.

I Sept.

Hydrogen 

ion

Calcium

Magnesium

Sodium Potassium Alkalinity Sulfate Nitrate Ch

WEST BRANCH SWIFT RIVER

Water Year 1984

3.1

.4

4.4 

1.0

5.1

7.4

1.7 

.6 

0

0

142.0

56.9

162.4 

96.3

197.4 

187.3

88.0 

46.9 

8.4

3.9

48.6

19.3

55.7 

32.9

67.7 

64.3

30.1 

16.0 

2.8

1.3

162.3

65.6

185.1 

110.7

225.0 

212.5

100.7 

54.0 

9.8

4.5

12.3

4.8

14.2 

8.1

17.2 

16.7

7.6 

4.1 

.9

.5

33.1

15.0

37.5

23.2

44.9 

43.9

21.7 

13.1 

4.5

2.8

195.3

78.0

223.6 

129.0

252.3 

225.8

109.1

53.7 

8.7

4.2

3.8

.8

1.5 

.8

2.9 

.8

2.2 

.3 

.4

1.0

Total................... 24 989 339 1,130

Oct. 1984 0

Nov. .1

Dec. .2

Jan. 1985 .1

Feb. .2

Mar. 1.1

Apr. .2

May .1

June 0

July 0

Aug. .1

Total................... 2 334 114 387

Total, WY 1984-

85..................... 26 1,323 452 1,517

86 240 

Water Year 1985

1,280 14 

7.6

27.1

40.3

30.5

33.2

79.0

40.1

28.9

17.4

8.6

21.4

2.6

9.2

13.7

10.4

11.3

26.9

13.6

9.8

5.9

2.9

7.2

8.9

31.4

46.6

35.4

38.4

90.7

46.4

33.6

20.3

10.0

24.8

.8

2.4

3.4

2.6

2.9

6.7

3.4

2.5

1.6

.9

1.9

4.2

8.7

11.6

9.6

9.8

19.7

11.5

9.3

6.8

4.5

7.5

8.8

34.8

55.2

39.8

35.8

117.0

50.4

29.8

18.6

8.5

22.3

29

115

103 421

,700

2

23

.1

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1.1

1.5

3.3

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Chemical Fluxes Entering and Leaving Stream Basins 37
Table 8. Fluxes of major solutes and water, West Branch Swift River and East Branch Fever Brook Basins, 

central Massachusetts

[Fluxes are given in equivalents per hectare, except for silica (moles per hectare) and water (millimeters). Net flux is calculated as input (wet 

deposition) minus output (stream load), after adjustment for deicing salts. Water year 1984 represents data collected from December 1983 

through September 1984. Water year 1985 represents data collected from October 1984 through August 1985]

Solute Input Output Salt-corrected Net flux

output

WEST BRANCH SWIFT RIVER

Water Year 1984

Solute Input Output Salt-corrected Net flux

output

EAST BRANCH FEVER VROOK-Continued

Water Year 1984

Hydrogen ion.. 

Calcium..........

Magnesium..... O

Sodium...........

Potassium.......

Alkalinity........

Sulfate ............

Nitrate.............

Chloride..........

Silica. ............ ..

Water..............

Hydrogen ion.. 

Calcium..........

Magnesium..... O

Sodium...........

Potassium .......

Alkalinity........

Sulfate ............

Nitrate. ........ ....

Chloride..........

Silica...............

Water..............

Hydrogen ion.. 

Calcium ..........

Magnesium..... O

Sodium...........

Potassium.......

Alkalinity........

Sulfate ............

Nitrate.............

Chloride.. ........

Silica...............

Water..............

.... 607 

.... 68

.... 47

.... 130

.... 15

0

.... 424

.... 272

.... 114

0

.... 1,546

Wa 

.... 854 

.... 61

.... 28

.... 69

.... 13

0

.... 610

.... 370

.... 70

0

.... 969

Total for \

.... 1,461 

.... 130

.... 75

.... 198

.... 28

0

.... 1,034

M1

.... 184

0

? 515

24 

989 

339 

1,130 

86 

240 

1,280 

14 

837 

941 

915

ter Year 

2 

334 

114 

387 

29 

103 

421 

9 

295 

319 

285

Vater Ye 

26 

1,323 

452 

1,517 

115 

343 

1,700 

23 

1,132 

1,260 

1,200

24 

951 

334 

438 

86 

240 

1,267 

14 

114 

941 

915

1985

2 

322 

112 

171 

29 

103 

417 

9 

70 

319 

285

ars 1984-85 

26 

1,273 

446 

609 

115 

343 

1,684 

23 

184 

1,260 

1,200

583 

-883 

-287 

-308 

-71 

-240 

-843 

258 

0 

-941 

631

852 

-261 

-84 

-102 

-16 

-103 

193 

361 

0 

-319 

684

1,435 

-1,144 

-371 

-411 

-88 

-343 

-650 

618 

0 

-1,260 

1,315

EAST BRANCH FEVER BROOK

Hydrogen ion.. 

Calcium..........

Wa 

.... 607

/;o

ter Year 

15

724

1984 

15 

510 

'469-546

592

-442 

1 [-478]- [-401]

Magnesium.....

Sodium...........

Potassium.,.,.,,

Alkalinity........

Sulfate ............

Nitrate ...

Chloride..........

Qilir-a

Water

Hydrogen ion.. 

Calcium..........

Magnesium, ,, 

Sodium...........

Potassium .......

Alkalinity........

Sulfate ............

Nitrate... ......... .

Chloride..........

Silica...............

Water..............

Hydrogen ion.. 

Calcium..........

Magnesium.....

Sodium...........

Potassium .......

Alkalinity........

Sulfate ............

Chloride..........

Nitrate.............

Silica...... ...... ...

Water..............

.... 47

.... 130

.... 15

0

424

.... 272

.... 114

0

.... 1,546

Wa

.... 854 

.... 61

oo

.... 69

.... 13

0

.... 610

.... 370

.... 70

0

.... 969

Total for > 

.... 1,461 

.... 130

.... 75

.... 198

.... 28

0

.... 1,034

.... 184

.... 641

0

2515

379 

1,536

102 

184 

989 

10 

1,648 

593 

744

ter Year

4

358

191

743

53 

88 

382 

16 

749 

206 

290

Vater Ye

19 

1,082

570 

2,280

156 

272 

1,371 

2,397 

26 

799 

1,034

286 

1 265-305 

317 

'250-383 

102 

184 

963 

10 

114 

593 

744

1985 

4 

307 

'295-315 

173 

'166-177 

110 

'87-133 

53 

88 

370 

16 

70 

206 

290

ars 1984-85 

19 

816 

'764-861 

459 

'432-482 

427 

'337-516 

156 

272 

1,333 

184 

26 

799 

1,034

-239 

'[-258H-218] 

-187 

'[-253H-121] 

-87 

-184 

-539 

262 

0 

-593 

802

850 

-246 

'[-254]- [-234] 

-145 

'[-149H-138] 

-42 

'[-65H-19] 

-40

-88 

240 

354 

0 

-206 

679

1,442 

-688 

'[-732H-635] 

-384 

i[_407]-[-356] 

-229 

'[-318H-139] 

-128 

-272 

-299 

0 

615 

-799 

1,481

'Ranges reflect uncertainty in deicing salt adjustments.

38 Factors Affecting Water Quality and Net Flux of Solutes in Two Stream Basins, Quabbin Reservoir Basin, Central Mass., 1983-85
values for net flux. More than 98 percent of hydrogen 

ion and as much as 96 percent of nitrate that entered 

each basin by wet deposition was retained. Net export 

was observed for all other major solutes. The net flux of 

alkalinity was 26 percent greater at Swift River than at 

Fever Brook. After adjustments for deicing salts, the net 

export of potassium was greater at Fever Brook, calcium and sodium export was greater at Swift River, and 

magnesium export was about the same in each basin 

(table 8). The total net export of base cations and silica 

was higher at Swift River relative to Fever Brook by 41 

and 58 percent, respectively. This comparison of net 

solute fluxes suggests a higher rate of weathering in the 

Swift River Basin. Although there may be loss of silica 

to diatom uptake at Fever Brook, the disproportionately 

higher net export of silica at Swift River is indicative of 

a different stoichiometry of weathering. About two 

times more sulfate was exported at Swift River than at 

Fever Brook; the additional sulfate export at Swift River 

partly balances the additional base-cation export.

During the 21-month study period, the Swift River 

and Fever Brook Basins yielded net base-cation fluxes 

of 2,014 and 1,429 eq/ha (equivalents per hectare), 

respectively, after adjustment for deicing salts (calculated from table 8). At Fever Brook, the net retention of 

hydrogen ion, 1,442 eq/ha, thus could account for the 

entire net flux of base cations. Because some of the 

hydrogen ion retention was balanced by nitrate retention, each basin had an excess export of cations that was 

necessarily balanced by the export of alkalinity and sulfate. Accordingly, the export of alkalinity and sulfate 

was greater at Swift River than at Fever Brook.

FACTORS AFFECTING WATER QUALITY AND 

NET FLUX OF SOLUTES

Precipitation Quality

Precipitation entering the Swift River and Fever 

Brook Basins was a dilute mixture of sulfuric and nitric 

acids, and minor amounts of base cations and chloride 

(table 2). Stream water leaving the basins was much 

enriched in base cations, which were balanced by 

sulfate, chloride (predominantly from deicing salts) and 

bicarbonate alkalinity (alkalinity in a low DOC circumneutral freshwater stream is virtually all as bicarbonate). 

Thus, processes within the basins transform the acidic 

precipitation into a moderately buffered solution of

sulfate and chloride salts. Precipitation chemistry may 

appear to have a limited role in final stream chemistry. 

However, there are three important ways in which 

stream chemistry is affected by the precipitation chemistry.

The first effect of precipitation chemistry on 

stream chemistry is related to the retention of hydrogen 

ion in the drainage basin; inputs of H+ in precipitation 

are much greater than outputs of H+ in streamflow 

(table 8). H+ is retained through consumption of protons 

in weathering reactions, or by ion exchange. There is 

much debate whether the increased acidity of modern 

precipitation causes increased weathering rates (Drever, 

1988). However, the possibility that increased acidity 

may drive ion-exchange reactions that alter the stoichiometry of cations in soil solution, and ultimately, stream 

water, is generally recognized. The effect of precipitation acidity on ion exchange is seen as a perturbation of 

a steady-state system; cation populations on exchange 

sites are in the process of adjustment to elevated inputs 

of hydrogen ion.

The second effect of precipitation chemistry on 

stream chemistry is evident during high flows. In both 

Swift River and Fever Brook Basins, alkalinity reached 

minimum concentrations of 1 |ieq/L (from typical concentrations near 100 |ieq/L) during the study (figs. 9 

and 10). These near-acidification events are attributed to 

the dilution of base-flow stream water with precipitation 

acidity. If precipitation were not acidic or only slightly 

acidic, such mixing would result in a much less pronounced dilution of acidity. Thus, at high flows, the 

acidity of precipitation contributes to the alkalinity 

decrease in the streams.

The third effect of precipitation chemistry on 

stream chemistry results from the high concentrations 

of sulfate in precipitation. Disregarding the effect of 

deicing salts, sulfate is the dominant anion in precipitation and stream water. Sulfate inputs and outputs are 

approximately balanced (table 8). Some sulfate may be 

released from weathering of sulfidic schist, which is 

more abundant in Fever Brook Basin; however, this 

source is believed to be minor relative to atmospheric 

sulfate. The dominance of sulfate in stream water 

appears to be a direct consequence of high atmospheric 

inputs. In pre-industrial times, bicarbonate most likely 

was the dominant anion (Reuss and Johnson, 1986). 

Sulfate serves as a mobile anion to transport base

Factors Affecting Water Quality and Net Flux of Solutes 39
cations to the stream, thus cation export is likely to be 

greater than it would be in a bicarbonate-dominated 

system.

Basin Hydrogeology

Differences in stream chemistry in Swift River and 

Fever Brook Basins are attributed in part to differences 

in hydrology in the two basins. The hydrology, in turn, 

is affected by the type and distribution of surficial geologic deposits. In deposits that have high hydraulic conductivities, such as outwash sands, ground water travels 

quickly to the stream and there is little opportunity for 

weathering. In deposits that have low hydraulic conductivities, such as dense basal tills, ground water has a 

long residence time and weathering reactions can be 

extensive.

Swift River is more responsive to storms than 

Fever Brook, as indicated by its more rapid hydrograph 

rise and recession. However, Swift River has a higher 

percentage of base flow and overall runoff than Fever 

Brook (table 1). These factors indicate greater soil/ 

water contact time at Swift River, which would tend to 

increase mineral weathering and solute transport. The 

higher concentration of weathering products (silica, 

base cations, and alkalinity) at Swift River relative to 

Fever Brook (table 3), therefore, is consistent with the 

hydrology of the two basins.

Hydrologic Flow Paths

Stream chemistry reflects in part the relative contributions of the various hydrologic flow paths to 

streamflow. Associated with each of the different hydrologic flow paths channel interception of canopy 

throughfall, saturation-excess overland flow, unsaturated subsurface flow, ground-water flow is a different 

set of factors that control the chemical evolution of that 

water. Some of these factors include: differences in mineralogy, contact time (flow velocity), ion-exchange 

capacity, oxidation/reduction state, microbiological 

activity, and abundance of tree roots. At low flows, 

streamflow is primarily composed of ground water that 

is rich in weathering products (silica, base cations, and 

alkalinity). During storms, streamflow is primarily 

composed of water from shallow flow paths, such as 

channel interception and saturation-excess overland 

flow, which are lower in solutes from weathering, and 

higher in solutes associated with precipitation including

sulfate, nitrate, and hydrogen ion. This type of conceptual model, in which stream chemistry is considered a 

product of the mixing of waters from different flow 

paths, each with a distinctive chemistry, is widely used 

to interpret stream chemistry and hydrology (Hooper 

and others, 1990).

The chemistry of ground water varied greatly in 

each basin (table 4), and differed in turn from the chemistry of base flow at the outlet gaging stations (table 3). 

This pattern indicates that the ground water sampled in 

each basin probably was not representative of that basin 

as a whole. Therefore, the water quality of base flow at 

each gaging station was considered to be a more reliable 

indicator of the composition of ground water discharging from that basin. Total base-cation loads exported 

from each basin in ground-water discharge were calculated using the quantified base-flow component of discharge from December 1983 through August 1985 with 

the flow-weighted average concentration of each chemical solute in selected samples of base flow collected at 

the gaging stations (table 3).

At the Swift River gaging station, ground-water 

discharge accounted for 53 percent of total discharge 

and 55 percent of the flux of base cations. At the Fever 

Brook gaging station, ground-water discharge 

accounted for 42 percent of total discharge and 50 percent of the flux of base cations. Significantly, transport 

of hydrogen ion in base flow accounted for only 17 and 

27 percent of the stream loads of hydrogen ion in Swift 

River and Fever Brook, respectively. The disproportionately higher export of base cations and lower export of 

hydrogen ion in ground water relative to those in total 

flow indicate that a greater degree of mineral dissolution 

and acid neutralization results when inputs of atmospheric acidity follow flow paths that allow considerable contact time of water with minerals in the basins 

before discharging to the streams.

At Fever Brook, surface-water impoundments 

significantly affected the temporal pattern of solute 

fluxes. Runoff water was retained in the impoundments 

where it mixed with older ground water, thus attenuating variations in solute concentrations and obscuring 

concentration-discharge relations. The impoundments 

appeared to have the most pronounced effect on 

alkalinity and sulfate. The significant concentration-discharge relation for alkalinity was attributed to the biologic production of alkalinity in the impoundments, 

which may have been the dominant alkalinity

40 Factors Affecting Water Quality and Net Flux of Solutes in Two Stream Basins, Quabbin Reservoir Basin, Central Mass., 1983-85
generating mechanism. Alkalinity increased during 

summer and autumn as flow decreased and biological 

activity increased. Alkalinity production was associated 

with sulfate reduction; sulfate concentrations decreased 

at Fever Brook during base-flow conditions in summer, 

in contrast to the sustained elevated sulfate 

concentrations during base flow at Swift River (figs. 9 

and 10).

Mineral Weathering

Differences in chemical concentrations and fluxes 

at the Swift River and the Fever Brook outlet gaging stations reflect contrasts in bedrock lithology and mineralogy of the two basins. The higher export of silica, base 

cations, and alkalinity at Swift River is a general indicator of greater weathering in that basin. The stoichiometry of weathering differs in the two basins as well. Net 

export of calcium and sodium is considerably higher at 

Swift River, net export of potassium is higher at Fever 

Brook, and net export of magnesium is about the same 

in the two basins. In general, the granitic lithologies of 

the Swift River Basin are resistant to weathering. However, a high proportion of the net cation export at Swift 

River, in particular the high calcium export, is attributed 

to weathering of the hornblende gabbro in the southeastern subcatchment (fig. 2). In the Fever Brook Basin, the 

amphibolite-schist lithology is relatively easily weathered. The greater relative export of magnesium and 

potassium at Fever Brook probably results from the 

weathering of hornblende, potassium feldspar, biotite, 

and (or) muscovite. The sodium flux probably derives 

from the weathering of plagioclase and (or) hornblende.

In Fever Brook Basin, the more easily weathered 

suite of minerals, coupled with the gentler topography, 

should be conducive to a higher rate of weathering compared to Swift River Basin. Most tributaries in the Swift 

River Basin have dilute chemistry with low alkalinity, 

indicative of limited weathering (table 4). The relative 

enrichment of solutes by weathering at the Swift River 

outlet gaging station is partly attributable to the composition of the tributary draining the southeast subbasin 

that is underlain by gabbro. Although this subbasin 

comprises only 11.2 percent of the total basin area, it 

contributes nearly 25 percent of the total base cations, 

16 percent of the total silica, and 77 percent of the total 

alkalinity exported from the basin. These figures were 

calculated from average solute concentrations in the 

tributary streams, assuming that streamflow in each 

tributary is proportional to its area.

The capability of minerals in the basins to neutralize acidic inputs is reflected in the enrichment of base 

cations in ground water (table 4). Water enters the 

basins as precipitation and continuously evolves in 

chemical composition as it contacts and reacts with 

minerals in the soil and surficial deposits (till and stratified drift) before discharging to the streams. The concentration of base cations increases in the water as 

primary minerals are dissolved by carbonic and mineral 

acids. Prolonged contact between water and minerals 

enables chemical reactions to proceed more completely 

and increases the degree of neutralization of acids.

Except for the small amounts in precipitation, base 

cations are ultimately derived from mineral weathering. 

The possible mineral-weathering reactions in the Swift 

River and Fever Brook Basins generally involve incongruent dissolution of primary aluminosilicate minerals 

in the soil and shallow aquifer. Typically, the primary 

minerals in igneous and metamorphic source rocks are 

metastable, owing to their formation at pressures, temperatures, and in the presence of fluids that are not 

found in weathering environments at the Earth's surface. Generally, the higher the temperature and pressure 

at which a mineral formed, the more reactive it is at the 

Earth's surface (Garrels and Christ, 1965). However, 

because of their strong chemical bonding and structural 

framework, silicate minerals weather slowly and therefore yield relatively small quantities of base cations and 

alkalinity in comparison to carbonates and other 

minerals.

The dissolution of aluminosilicate minerals is 

driven by the acidic hydrogen ion. Primary minerals 

react with water and hydrogen ion to yield base cations 

(calcium, magnesium, sodium, potassium) and silica to 

solution and form new aluminous mineral phases (usually clay minerals) that are more stable at the Earth's 

surface. This reaction was generalized by Bricker and 

others (1968) as:

Primary aluminosilicate + H++H2O = Secondary 

aluminum-rich minerals + base cations + H4SiO4, (6)

In this reaction, aluminum is assumed to be conserved in solid phases. This assumption appears to be 

valid in the study drainage basins, given the low concentrations of dissolved aluminum in ground water and 

base-flow stream samples.

Factors Affecting Water Quality and Net Flux of Solutes 41
In most soil and ground-water environments, the 

most important source of hydrogen ions to drive weathering reactions is carbonic acid. For a system open to 

the atmosphere, a continuous source of carbon dioxide 

gas is in contact with soil water. Additional carbon dioxide may be supplied by biological processes, such as 

plant respiration. Carbon dioxide and water react to 

form carbonic acid, which dissociates to produce 

bicarbonate and hydrogen ion, described as follows:

CO2 + H2O = H2CO3 = HCO3 + H+ (7)

Other sources of hydrogen ion include organic acids in 

the soil zone, weathering of sulfide minerals, and strong 

mineral acids in precipitation.

Possible weathering reactions involving minerals 

identified in the bedrock and in soil samples from Swift 

River and Fever Brook Basins include:

CaAl2Si2O8 (anorthite) +2CO2 + 3H2O = Ca2+ + 

2HCO3 + Al2 Si2O5 (OH) 4 (kaolinite) , (8)

2NaAlSi 3 O8 (albite) +2CO2 +11H2O = 2HCO3 + 

2Na+ + 4H4 SiO4 + Al2 Si 2O5 (OH) 4 (kaolinite) , (9)

3KAlSi 3 O8 (microcline) +2H+ + 12H2O = 2K+ + 

6H4 SiO4 + KAl3 Si 3 O 10 (OH) 2 (illite) , (10)

8H4 SiO4

3K2 (Mg3 Fe 3 ) Al2 Si6O20 (OH) 4 (biotite)

16H2O + 20H+ = 6K+ + 3Mg2+ + 3Fe2+

+ 2 (Mg3Fe3)(Al3Si502{)H8H20)

(vermiculite) (11)

(Ca, Na) 2 _ 3 (Mg, Fe2+ , Fe 3+ , Al) 5 ( Al, Si) 8O22 (OH) 2

(hornblende) + vH+ + w>H2O = xCa2++ jNa+ -I- zMg2+ 

+nH4SiO4 + 2(Mg3Fe3)(Al3Si5O20>(8H2O)

(vermiculite), (12)

Equations (8) and (9) represent the weathering of 

the calcium and sodium end members of plagioclase to 

kaolinite. True plagioclase nearly always has a 

composition intermediate between the end members, 

thus equations (8) and (9) could be replaced with a 

single reaction if that composition were known. The 

weathering of microcline to illite (eq. 10) generally is 

less important, although illite was detected in all soil 

samples. Vermiculite was the dominant clay mineral in

most soil samples, indicating that the weathering of 

biotite and hornblende to vermiculite (eqs. 11 and 12) 

may be important reactions in the basins. In equation 

12, the quantities in italics are variables, because 

hornblende composition varies widely.

Although the overall net export of solutes was 

higher at Swift River (table 8), the export of magnesium 

was about the same in each basin, and the export of 

potassium was higher at Fever Brook than at Swift 

River. This implies that the weathering of hornblende 

(eq. 12) and (or) biotite (eq. 11) was relatively more 

important at Fever Brook. At Cadwell Creek, 14 km 

south of the Swift River outlet gaging station, hornblende was relatively rich in calcium and magnesium 

and poor in sodium (Michener, 1983). Hornblende 

weathering probably was responsible for the relatively 

high magnesium export at Fever Brook, given that hornblende is abundant in the basin and is easily weathered 

(April and others, 1986). Biotite (eq. 11) is more easily 

weathered than microcline (eq. 10), and thus was the 

most likely source for the higher potassium export from 

Fever Brook.

If the hornblende compositional analyses of 

Michener (1983) are indicative, hornblende in the 

region is too low in sodium to account for the sizeable 

sodium fluxes (after deicing salt corrections) at each of 

the two basin outlet gaging stations. The more likely 

source of sodium is plagioclase weathering (eq. 9). 

Michener (1983) found that the average plagioclase 

composition at Cadwell Creek was An20, or 80 percent 

of the sodium end member. Plagioclase in the Carter and 

Mundberry Basins, adjacent to Fever Brook, also was 

high in sodium (Elizabeth Knapp, University of Massachusetts, written commun., 1990). Weathering of 

sodium plagioclase has been the dominant source of 

sodium to solution in other studies of drainage basins 

(Katz and others, 1985; Velbel, 1985; Clayton, 1988; 

Peters, 1989b). As plagioclase weathers to kaolinite, 

two moles of silica are released for each mole of sodium 

(eq. 9), but no silica accompanies the release of calcium 

(eq. 8). Thus, in the absence of other weathering 

reactions releasing or consuming sodium or silica, the 

sodium: silica ratio should be 0.5. The sodium: silica 

ratio is 0.33 at Swift River and 0.29 at Fever Brook. 

These ratios suggest that plagioclase weathering 

accounts for a considerable amount of the silica flux, 

and probably is more important at Swift River. At Swift 

River, the high net export of calcium, and the high

42 Factors Affecting Water Quality and Net Flux of Solutes in Two Stream Basins, Quabbin Reservoir Basin, Central Mass., 1983-85
calcium:silica and calcium:magnesium ratios compared 

to Fever Brook, result from the abundance of calcic 

plagioclase in the southeast tributary.

The equilibrium solubility model WATEQF 

(WATer EQuilibrium Fortran) was used to calculate 

the equilibrium speciation of inorganic ions and ion 

complexes in the two basins (Plummer and others, 

1976; thermodynamic data current with the 1984 

version of the program). The saturation index, defined 

as the log of the ratio of the ion activity product to the 

thermodynamic equilibrium constant, was computed in 

the model for possible mineral phases (table 9). Saturation indexes less than zero for a given mineral imply 

that the solution is undersaturated with respect to that 

mineral; saturation indexes greater than zero imply that 

the solution is supersaturated with respect to that mineral. Undersaturated conditions favor dissolution 

whereas supersaturated conditions favor precipitation. 

Saturation indexes were determined from analyses of

ground water and stream base flow, because those 

waters had the longest contact time with minerals of the 

soil, till, and bedrock. In each basin, all waters analyzed 

were undersaturated with respect to the primary minerals and were nearing saturation or were somewhat 

supersaturated with respect to secondary minerals postulated to be forming as weathering products. Based on 

the analysis, kaolinite was the secondary mineral most 

favored to be forming in each basin (table 9).

Stability diagrams of mineral equilibria illustrate 

conditions of chemical equilibrium of selected minerals 

in contact with natural waters. If it is assumed that all 

reactions occur at 25°C and that aluminum is conserved 

in the solid phases, the stability of one mineral relative 

to another can be evaluated, as can the degree of 

saturation of that water with respect to a given mineral. 

Activities of aqueous species calculated by use of 

WATEQF were plotted on activity diagrams for the

Table 9. Saturation index for some minerals for flow-weighted-average base-flow and 

ground-water samples in West Branch Swift River and East Branch Fever Brook Basins, central 

Massachusetts

[Saturation index: The saturation index is the log of the ratio of ion activity product to the thermodynamic equilibrium constant, K, 

at the temperature of the water sample]

Sampling site

Swift River

till well.

Swift River sand

and gravel well.

Sampling 

date

3-28-84

4-10-84

3-28-84

4-10-85

y Saturation index

Anorthite

-9.9

-11.5

-7.2

-9.8

-5.8

-6.4

-3.5

-5.2

Albite Chlorite Gibbsite Kaolinite Chalcedony

-31.5

-34.1

-24.5

-30.8

-0.04

-.75

.49

-.35

2.2

85

3.8

1.9

-0.19

-.13

.11

.00

Swift River outlet 

gaging station.... o

Fever Brook 

till well....................... 4-03-84

Fever Brook sand 

and gravel well.

4-25-84 

3-20-85 

8-20-85

Fever Brook 

Knault's well (till)........ 4-10-85

-7.5

-3.8

-9.4 -4.6

-6.9 -3.4

-10.5 -5.2

-3.1

-4.8

-2.5

-23.3 46

-7.4 .36

2.6

3.2

-26.1

-24.2

-28.9

-.70 

.58 

-1.1

1.5 

4.02 

.70

.14 

.13 

.11

Fever Brook outlet 

gaging station...... o

-.70

-5.4

-8.2

-25.8

1.0

.14

5.3

1.78

-.39

-.05

.34

-.48

'Flow-weighted-average base flow.

Factors Affecting Water Quality and Net Flux of Solutes 43
systems CaO-A^CVSiCV^O and K^O-A^C 

H2O at 25°C (fig. 14). In these simplified four-component systems, kaolinite was the most stable mineral. The 

field evidence provided some support for this analysis, 

as kaolinite was detected in minor amounts in nearly all 

soil samples. However, gibbsite also was detected in 

several samples.

Aluminum Geochemistry

The solubility of some aluminum minerals is 

enhanced by a decrease in pH (Drever, 1988). Increased 

aluminum concentrations associated with acidic deposition have been linked to fish mortality (Driscoll and 

others, 1980; Schofield and Trojnar, 1980), and have 

been implicated as a contributing cause of forest dieback in Germany (Ulrich, 1983). Aluminum is most 

toxic in the labile, monomeric form (Al ); its effects 

are more benign when complexed with either an inorganic ligand, such as fluoride or hydroxide, or with an 

organic ligand. Aluminum toxicity is low in organicrich waters, even when the pH is low, because most of 

the aluminum is organically complexed. Aluminum 

geochemistry is important not only from the standpoint 

of aluminum toxicity, but also because aluminum has a 

significant effect on the geochemical cycles of phosphorous, carbon, and trace metals, and because it plays an 

important role in pH buffering (Driscoll, 1985).

Seasonal Variations

The rapid increase in aluminum concentrations in 

response to increased flows at Swift River was consistent with the surficial geology of the basin. The thin 

soils and steep ridges lead to rapid runoff and short contact time of storm water with rock and soil materials, 

allowing minimal neutralization of the acidic inputs. 

Hydrogen-ion acidity can rapidly mobilize aluminum in 

near-surface soil (McAvoy, 1989). Relations between 

aluminum concentration and discharge contrasted 

sharply to relations between other dissolved solutes and 

discharge, in which solute concentrations generally 

decreased with increasing discharge (figs. 9, 10, and 

13).

Aluminum concentration is frequently affected by 

variations in pH and DOC. At Swift River, aluminum 

concentration increases were associated with concurrent increases in hydrogen ion concentration (fig. 9), 

and there was a significant correlation between

aluminum and pH (fig. 15). Elevated concentrations of 

hydrogen ion may have caused the increase in aluminum through the dissolution of aluminum-bearing minerals in the soils, such as gibbsite [A1(OH)3 ] (Johnson, 

1979). Alternatively, increases in aluminum may be 

attributed to the replacement of hydrogen for aluminum 

on cation-exchange sites; ion exchange caused the episodic increases of aluminum during high-runoff periods 

at a drainage basin in Massachusetts, as acidic runoff 

flowed predominantly through the shallow soil zone 

(McAvoy, 1989).

At Fever Brook, aluminum concentrations were 

poorly correlated with pH (fig. 15). Hydrogen ion concentrations generally were higher in Fever Brook than 

in Swift River in late spring and summer (figs. 9, 10). 

The higher hydrogen ion concentrations (lower pH) 

probably were maintained by organic acids, as suggested by the concurrent increase in DOC from 4 to 

10 mg/L from late spring to early autumn. Water was 

highly colored in Fever Brook, because of the presence 

of organic anions. Despite variations in DOC and pH, 

aluminum concentrations were fairly constant at Fever 

Brook. Except for the moderate increase in aluminum 

associated with the May 1984 flood, the few episodic 

increases that were detected at Fever Brook were not 

clearly correlated with changes in pH or DOC at high 

discharge; those increases, however, did coincide with 

high aluminum concentrations during the same period 

at Swift River. More frequent aluminum increases may 

have occurred at Fever Brook than were detected by 

weekly sampling. The higher chronic aluminum concentrations at Fever Brook may result from kinetic constraints on the precipitation of aluminum when 

aluminum-rich soil water, such as that sampled from the 

Fever Brook deep lysimeter (table 4), mixes with 

stream water during storm runoff (Burns, 1989).

Spatial Variations

At sites on Fever Brook tributaries, the relation 

between aluminum and pH was masked by the additional effect of DOC (table 4). Although mean DOC 

concentrations varied little among the surface-water 

sites, aluminum concentrations tended to decrease with 

increasing DOC. The outlet to Brooks Pond had the 

lowest aluminum, despite the lowest pH and highest 

DOC. The data from the tributary sites though 

limited are consistent with data from the main outlet 

(fig. 15), which suggest that there is no relation between

44 Factors Affecting Water Quality and Net Flux of Solutes in Two Stream Basins, Quabbin Reservoir Basin, Central Mass., 1983-85
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DISSOLVED ORGANIC CARBON CONCENTRATION, IN MILLIGRAMS PER LITER

Figure 15. Relations between aluminum concentration and pH, and aluminum concentration and 

dissolved organic carbon concentration, West Branch Swift River and East Branch Fever Brook, central 

Massachusetts.

46 Factors Affecting Water Quality and Net Flux of Solutes in Two Stream Basins, Quabbin Reservoir Basin, Central Mass., 1983-85
aluminum and DOC at Fever Brook. However, the high 

DOC, coupled with the low solubility of aluminum at 

pH greater than 5.5 (Johnson, 1979), assures that the 

most of the aluminum present is organically complexed.

Variations in aluminum concentrations at the outlet 

gaging stations, particularly at Swift River, can be 

explained by a mixing of waters from shallow (within 

the upper 30 cm of soil, including the organic horizon) 

and deep (deeper than 30 cm, or within the mineral soil 

or till) flow pathways. Ground water in both basins had 

aluminum concentrations less than 40 (ig/L (table 4). 

Ground water represents the deep flow path. As the 

ground-water component of flow increased, aluminum 

concentrations in the streams decreased. The low aluminum concentrations would be expected in ground water 

that has evolved to a stage where it is high in weathering 

solutes, pH, and alkalinity. At Swift River, ground water 

has considerably less aluminum than the tributary 

streams, despite a comparably low pH. This is attributed 

to the lower DOC in ground water relative to the 

streams. Storm runoff through the upper soil zone represents the shallow flow path. Increases in aluminum 

during high streamflow resulted as a higher percentage 

of streamflow was derived from this flow path. Soil 

waters had aluminum concentrations of several hundred 

micrograms per liter, consistent with the low pH (4.67 

to 5.56) (table 4). Data were too limited to assess the 

effect of DOC in the high aluminum concentrations in 

soil waters.

The spatial pattern of aluminum concentrations in 

stream water is dependent on the spatial pattern of 

ground-water discharge to streamflow. Ground-water 

discharge to tributaries, particularly during storms or 

snowmelt runoff, is likely to be minimal compared to 

ground-water discharge at the outlet gaging stations. 

Unconsolidated surficial deposits along headwater tributaries are not as thick or extensive as those along the 

mainstem. Thus, precipitation inputs in the headwater 

areas follow shorter flow paths before discharging to 

streams, and have less contact time for neutralization 

reactions in the soil. A large pool of aluminum is readily 

available to infiltrating acidic waters, causing the high 

concentrations measured in soil waters (table 4). Therefore, the limited extent of surficial deposits in the headwater areas results in shorter hydrologic flow paths that 

tend to limit the degree to which acidic inputs are neutralized, leading to elevated concentrations of dissolved 

aluminum in the headwater streams.

Chemical Speciation and Solubility of 

Dissolved Aluminum

Aluminum speciation must be considered in 

assessing the effects of acid deposition on fish and other 

aquatic biota in the basins. Driscoll and others (1980) 

reported that low pH and high aluminum concentrations 

in streams in the Adirondack region of New York were 

most prevalent at high discharge conditions during 

storms and during snowmelt in the spring, and at low 

discharge conditions during the summer. The aluminum 

during snowmelt was predominantly labile inorganic 

aluminum, whereas during summer low flow it was predominantly organically complexed aluminum. Concentrations of dissolved aluminum in Swift River during 

spring snowmelt regularly exceeded 110 (ig/L, the 

threshold for toxicity to fish (Schofield and Trojnar, 

1980). On the basis of the results of Driscoll and others 

(1980), most of this aluminum is assumed to be in the 

labile inorganic form, which is most toxic. "Fish kills" 

(DiNardo, 1984; Halliwell, 1985) as reported in nearby 

streams, may have been caused by high concentrations 

of labile aluminum. At Fever Brook, in contrast, aluminum toxicity to fish probably is minimal because more 

of the dissolved aluminum is organically complexed, 

and because episodic increases in aluminum 

concentration are less frequent.

WATEQF was used to calculate the equilibrium 

distribution of dissolved aluminum species for selected 

samples from Swift River and Fever Brook (table 10). 

WATEQF requires the "thermodynamically active" 

inorganic aluminum concentration to calculate aluminum speciation. From this study, only total dissolved 

aluminum concentrations, which included organically 

bound aluminum, were available. This limitation of the 

data is noted where it may affect interpretation of the 

model results.

Input to the model for each speciation calculation 

included aluminum and major dissolved solute concentrations, as well as temperature and pH. The model calculated the activity, or effective concentration, of each 

ion and its complexes. Model results indicated that the 

aluminum hydroxide complex, A1(OH)2+ , was the 

major form of aluminum in most samples, followed in 

importance by the fluoride complex, A1F2+. Monomeric 

aluminum, A13+, generally comprised only 1 to 10 percent of total dissolved aluminum in each sample. Only 

one sample (pH 5.1) collected during snowmelt runoff 

had A13+ as the dominant form of dissolved aluminum

Factors Affecting Water Quality and Net Flux of Solutes 47
Table 10. Chemical speciation of aqueous aluminum in selected water samples from West Branch Swift 

River and East Branch Fever Brook Basins, central Massachusetts

[Concentrations are given in moles per liter, in "p" notation (negative logarithm (base 10) of concentration). Altotal, total dissolved aluminum. , no data]

Sampling

Sampling site identifier Date 

(see fig. 14)

PH Altotal A1(OH)2+ A1(OH)2+ AIF+ AISO4+

WEST BRANCH SWIFT RIVER BASIN

Swift River outlet 

gaging station

1

2 

3

1-24-84 

2-16-84 

6-26-84

6.6 

5.1 

6.7

5.35 

5.13 

5.96

7.38 

5.41 

9.31

6.80 

6.34 

8.05

5.39 

6.42 

6.04

7.14 

5.59 

7.74

8.72 

6.82 

10.62

Average base flow

Swift River sand 

and gravel well

Swift River till well

4

5 

6

7 

8

-

3-28-84 

4-10-85

3-28-84 

4-10-85

6.2

6.0

5.8

5.7 

5.5

5.66

6.72 

5.96

5.66 

5.96

8.35

8.12 

7.27

6.51 

6.80

7.08

7.85 

7.15

6.59 

6.96

5.72

6.80 

6.25

5.85 

6.35

6.96

6.46

6.72 

6.52

9.52

9.51 

8.59

7.74 

7.96

EAST BRANCH FEVER BROOK BASIN

Fever Brook 

gaging station

Average base flow

Fever Brook sand 

and gravel well

Fever Brook till well

Fever Brook 

Knault's well (till)

1 

2 

3

4

5 

6 

7

8

9

1-24-84 

2-16-84 

6-26-84

-

4-25-84 

3-20-85 

8-20-85

4-03-84

4-10-84

6.0 

5.6

5.7

5.9

6.2 

7.5 

5.9

7.7

7.3

5.43 

5.59 

4.66

5.72

6.72 

5.43 

6.43

6.43

5.96

6.60 

6.52 

6.57

8.01

8.60

7.27 

8.42

12.10

10.41

6.64 

6.96 

6.00

7.30

8.17 

6.82 

8.12

10.17

8.80

5.82 

6.54 

4.74

5.89

6.96

5.62 

7.06

7.43

6.40

5.77 

5.72 

5.68

6.55

11.42 

6.09 

6.80

12.47

7.64

7.96 

7.96 

8.05

9.22

9.82 

8.39 

9.33

13.13

11.96

(27 percent by molarity). The sulfate complex, A1SO4+, 

was a minor component in all water samples, and the 

molarity usually was several orders of magnitude less 

than that of total dissolved aluminum.

Aluminum-bearing minerals in the system A12O3- 

SiO2-H2O, such as gibbsite and kaolinite, are weathering products of primary aluminosilicate minerals. Solubilities of these minerals in water reach a minimum near 

pH 6.4 and increase as pH decreases (Drever, 1988). In 

general, at any particular concentration of silica, the 

most stable aluminum silicate mineral is the mineral 

that has the lowest equilibrium concentration of aluminum. For streams in the Swift River and the Fever 

Brook Basins, in which the activity of silica is 

approximately 10~4 , the activity of aluminum in

equilibrium with kaolinite is less than that which would 

be in equilibrium with gibbsite, A1(OH)3 (fig. 16). For 

solution pH values from 5.1 to 6.8 at the outlet gaging 

stations, the theoretical activity of aluminum in equilibrium with kaolinite ranges from 10~7 -° (2.7 |Xg/L) to 

10'8 - 1 (0.2 jig/L), respectively.

Aluminum activity in stream water and ground 

water generally was 10 to 100 times greater than the 

calculated theoretical activity at equilibrium with 

kaolinite and gibbsite; the activities of aluminum calculated for selected samples plot above the solubility lines 

of these minerals (fig. 16). Gibbsite and kaolinite were 

identified in some of the soil samples collected in the 

basins. However, the apparent supersaturation suggests 

that concentrations of aluminum may be controlled by

48 Factors Affecting Water Quality and Net Flux of Solutes in Two Stream Basins, Quabbin Reservoir Basin, Central Mass., 1983-85
C/D

LLJ

O 

LJJ 

Q. 

OD

Q 

LJJ

P

CD 

O

-3

-4

-5

-6

-7

-8

-9

-10

SWIFT RIVER

O

C/D 

C/D

Q 

LL 

O

£

g -4

O

-3

-5

-6

-7

-8

-9

-10

Sampling Locations 

See Figure 14

a H4 SiO4 =10"4

6 8 

pH, IN STANDARD UNITS

10 12

FEVER BROOK

-4

4 6 8 10 

pH, IN STANDARD UNITS

12

Figure 16. Composition of water and stability of dissolved aluminum species in 

equilibrium with gibbsite and kaolinite at 25 degrees Celsius, West Branch Swift River 

and East Branch Fever Brook Basins, central Massachusetts. (Modified from Drever, 

1988.)

Factors Affecting Water Quality and Net Flux of Solutes 49
minerals other than gibbsite and kaolinite, for example, 

cryptocrystalline phases of aluminum hydroxide (Jones 

and others, 1974). An alternate interpretation is that the 

solutions are in fact in equilibrium with crystalline gibbsite and kaolinite, but that the presence of colloidal or 

suspended aluminum, and (or) organically bound 

aluminum, caused an overestimation of aluminum 

concentrations.

When the infiltration capacity of the soil is 

exceeded during heavy storms or rapid snowmelt, the 

low-pH, high-aluminum soil water can be flushed rapidly from the soil zone. As this water mixes with stream 

water of higher pH, precipitation of aluminum may be 

limited kinetically. A possible example of the resulting 

supersaturation with respect to gibbsite is the stream 

sample collected during the heavy rainstorm on May 30, 

1984, at the tributary in the subbasin underlain by 

gabbro. The aluminum concentration was 110 (ig/L, 

much higher than the equilibrium concentration calculated for the relatively high pH (6.48) at the time of sampling. The supersaturation may be explained either by 

kinetic constraints on the precipitation reaction, or by 

the presence of increased polymeric or organicallybound aluminum in the filtered sample. More frequent 

sampling of soil water, ground water, and stream water 

during storm runoff and snowmelt would help to 

improve the understanding of the relation between 

aluminum geochemistry and hydrology.

Biogeochemical Processes

Sulfate Mobility

The mobility of sulfate in a basin that has surface 

and ground water of low ionic strength is an important 

factor in determining the sensitivity of that basin to 

acidic deposition. To maintain electrical charge balance, 

sulfate ions that are transported in solution must be 

accompanied by positively charged ions. These ions 

generally are base cations, important nutrients for plant 

growth. The availability of base cations for uptake by 

vegetation is directly affected by the fate of sulfate in 

the soil zone. Sulfate transport promotes transport of 

base cations from the soil, potentially causing a lack of 

nutrients for vegetation. If base cations are depleted 

from exchange sites faster than they are resupplied by 

weathering, hydrogen or aluminum becomes the cation 

that accompanies the sulfate, thus lowering the 

alkalinity of receiving waters. Streams and lakes in

drainage basins with limited capacity to supply base cations are thought to acidify over periods of decades to 

centuries (National Acid Precipitation Assessment 

Program, 1983).

Sulfate sorption takes place primarily in the soil, 

where weathering of primary minerals to clays and 

metal oxides and hydroxides has generated sorption 

sites. Where sulfate is retained by sorption sites, basecation depletion from the soil is limited; where sulfate 

is not retained, and (or) sulfate is desorbed from sorption sites, base-cation depletion results as cations are 

removed to balance the anion charge. The potential for 

acidification is greatest in drainage basins with soils that 

have little capacity to adsorb sulfate or already are saturated with sulfate. At this stage, sulfate replaces bicarbonate as the dominant anion in solution, as 

documented in a forested drainage basin in the White 

Mountains of New Hampshire (Cronan, 1978). After 

correction for chloride from road salt, sulfate also is the 

dominant anion in the surface and ground waters in the 

Swift River and Fever Brook Basins.

The flux of sulfate in streamflow is the result of 

several sources and processes, and can be expressed as:

Ss = Swd dd S - S - S -

sp mw (13)

where

Ss is sulfate in streamflow, 

Swd is sulfate in wet deposition, 

Sdd is sulfate in dry deposition, 

Ssp is sulfate that is added or removed by

sorption processes, 

Smw is sulfate generated by mineral weathering

and (or) consumed in precipitation

reactions, and 

Sbp is sulfate generated or consumed by

biological processes.

Ss was calculated from sulfate concentrations and 

stream discharge for each basin. Swd was calculated 

from measurements of sulfate concentrations and precipitation at the collection site in New Salem. Sdd, Ssp, 

Smw, and Sbp were not directly measured, thus the quantities of sulfate that entered in dry deposition and sulfate 

that was cycled in each basin had to be indirectly 

evaluated.

A reliable, reproducible method for the measurement of Sdd was not available during this study. 

However, some researchers have equated the dry

50 Factors Affecting Water Quality and Net Flux of Solutes in Two Stream Basins, Quabbin Reservoir Basin, Central Mass., 1983-85
deposition of sulfate to the net flux of sulfate if no other 

sources are present in the drainage basin (Likens and 

others, 1977; Katz and others, 1985; Peters, 1989a).S^ 

probably is the largest of the unknown terms. Dry deposition has been recognized as an important source of 

sulfate in many drainage basins (Brezonik and others, 

1980; Kerr, 1981; Suarez and Jones, 1982; Lindberg and 

Garten, 1988). The particulate form of sulfur may be a 

neutral or acidic salt, whereas sulfur which enters as a 

gas, such as SO2 , can oxidize and react with water to 

produce sulfuric acid. Sulfate is incorporated in wet 

deposition by washout (scavenging) or rain out (sulfatebearing particles provide nucleation centers for the formation of water droplets or snow flakes). Dry deposition of sulfur occurs through absorption by vegetation 

or settling on vegetation surfaces independently of rain. 

This sulfur eventually will be washed into the drainage 

basin but will not be accounted for in samples of wet 

deposition.

Sulfate export in stream water (Ss) exceeded sulfate inputs in wet deposition (Swd) by 55 percent at Swift 

River and 23 percent at Fever Brook. If sulfate behaves 

conservatively, which is equivalent to the condition that 

Smw> Ssp, and SbP are negligible, or Sdd = SS - Swd, then dry 

deposition accounted for 36 percent of the total sulfate 

deposition at Swift River and 19 percent of the total sulfate deposition at Fever Brook from December 1983 

through August 1985 (calculated from table 8). This 

difference can not be attributed entirely to differences in 

dry deposition between the two basins, because of the 

geographic proximity of the basins and similar vegetation. The 36 percent dry deposition of sulfur calculated 

for Swift River is comparable to the dry deposition contribution estimated for the nearby Catskill Mountains in 

southern New York (P.S. Murdoch, U.S. Geological 

Survey, written commun., May 1985). However, the 

sulfate dry deposition estimate of 19 percent for Fever 

Brook probably is too low, calling into question the 

assumption that Smw, Ssp, and Sbp are negligible. From 

these results, a sink for sulfate appears to be present in 

Fever Brook.

The total (salt-corrected) flux of sulfate from the 

Fever Brook Basin (1,333 eq/ha, table 8) was 79 percent 

of sulfate flux from the Swift River Basin (1,684 eq/ha). 

This difference in sulfate flux between the two basins 

may be attributed to differences in water flux, as well as 

factors affecting Smw, Ssp , and Sbp . Water flux can 

significantly affect sulfate flux (Shaffer and Galloway,

1982; Shanley, 1989; Huntington and others, 1994). The 

runoff from Fever Brook (1,034 mm) was only 86 percent of the runoff from Swift River (1,200 mm), and 

thus may account for most of the difference in the net 

flux of sulfate.

If water flux accounts for most of the difference in 

sulfate flux, the additional sulfate retained in Fever 

Brook would be as Ssp . This pool of sorbed sulfate is 

labile and will be mobilized given sufficiently high soil 

moisture. An additional amount of sulfate at Fever 

Brook probably was consumed by sulfate reduction, 

which would be represented in equation (18) as a negative term Sbp . Decreases in sulfate during the summer at 

Fever Brook (fig. 10), while sulfate concentrations at 

Swift River remained constant (fig. 9), indicate that sulfate reduction may be an important process. Sulfate 

concentrations at the three ground-water sites in the 

Fever Brook Basin were significantly higher than sulfate concentrations at the four ground-water sites in the 

Swift River Basin (table 4), an indication that there may 

be contributions of sulfate, Smw, from the weathering of 

sulfides. A positive Smw term would increase Ss, whereas 

sulfate reduction would decrease Ss. Sulfide weathering 

and sulfate reduction each may be significant processes 

at Fever Brook, and both are discussed briefly below.

The weathering of sulfide minerals such as pyrite 

and pyrrhotite may contribute to the sulfate flux from 

the drainage basins. These minerals are present in the 

sulfidic schist contained in the Rangely Formation, 

which underlies parts of both basins. This formation is 

areally more extensive in the Fever Brook Basin. Two 

ground-water sites in the Fever Brook Basin have sulfate concentrations much greater than 200 jLieq/L 

(table 4), well in excess of the amount that would be 

expected from precipitation and evapotranspiration. 

Parnell (1983) identified pickeringite, a highly soluble 

aluminum sulfate mineral, in powdery surface encrustations at a nearby outcrop of the Partridge Formation. 

Weathering of sulfide minerals in the formation are the 

likely source of sulfate for the formation of this 

secondary mineral.

The extensive wetlands in the Fever Brook drainage basin provide an environment favorable to sulfate 

reduction. Evidence for sulfate reduction is given by the 

pattern of sulfate concentrations in the two basins from 

June to November 1984. During this period, discharge 

decreased in both basins during a period of less than 

average precipitation. At Swift River, alkalinity

Factors Affecting Water Quality and Net Flux of Solutes 51
increased during this period, whereas sulfate concentrations remained constant or increased only slightly 

(fig. 9). At Fever Brook, alkalinity increased but sulfate 

concentrations decreased during the period. Loss of sulfate by reduction appeared to contribute to the alkalinity 

increase at Fever Brook; alkalinity and sulfate concentration were negatively correlated at Fever Brook and 

positively correlated at Swift River during June to October 1984 (fig. 17). A concurrent increase in the concentration of DOC in Fever Brook (fig. 10) is consistent 

with favorable conditions for sulfate reduction. Additionally, hydrogen sulfide gas was usually detected at 

the Fever Brook sand and gravel well, located near a 

marshy area. These conditions indicate that sulfate was 

being reduced by bacteria in the impoundments and 

swampy areas. In the bacterially mediated sulfate reduction reaction, sulfate is reduced, whereas organic matter 

(CH2O) is oxidized (Monahan, 1984) as follows:

2C02 + 2H2 0. (14)

Although sulfate reduction apparently was the most 

important during the summer and autumn of 1984, it 

may proceed at slower rates and affect the sulfate 

concentration and flux (Ss) during other periods as well.

Retention of Hydrogen and Nitrate

Most of the hydrogen ion and nitrate that entered in 

wet deposition were retained by both basins. Hydrogen 

ion was removed by weathering and cation-exchange 

reactions, and nitrate was taken up as a nutrient by vegetation. Short-lived increases in the concentration of 

hydrogen ion and nitrate in the streams were observed 

after large hydrologic inputs, such as storms or rapid 

snowmelt. During these events, normal flow paths were 

short-circuited, and the resulting limited soil contact 

time precluded significant removal of hydrogen ion and 

nitrate from solution. Using net-flux data (table 8) and 

estimating ammonium flux from data at nearby Bickford Reservoir drainage basin (Hemond and Eshleman, 

1984), the processes by which chemical solutes are 

generated and consumed in the drainage basins can be

iii

160

140

120

O ^j 100

o >

°5 

£0

< o 80 iS

ID O

60

40

i r

Swift River

n i i i i i

Fever Brook

0 20 40 60 80 100 120 140 0 20 40 60 80 100 120 140

ALKALINITY CONCENTRATION, IN MICROEQUIVALENTS PER LITER

Figure 17. Relations between sulfate and alkalinity concentrations in West Branch Swift River and 

East Branch Fever Brook, central Massachusetts, June through October 1984.

52 Factors Affecting Water Quality and Net Flux of Solutes in Two Stream Basins, Quabbin Reservoir Basin, Central Mass., 1983-85
quantified. The net result of these processes is constrained by the following charge-balance equation, 

derived from rearranging the alkalinity equation:

2[Ca2+ ] +2[Mg2+ ] + [Na+ ] + [K+ ] - [NOj]

= 2 [SO2/] + [HCO-] - ([H+ ] - [NHJ]) (15)

The left side of the equation represents the products of mineral-weathering reactions that produce base 

cations, and the retention of nitrate. The right side of the 

equation balances those reactions with export of sulfate 

and bicarbonate alkalinity, and consumption of hydrogen and ammonium (fig. 18). Negligible amounts of 

carbonate CO32" and hydroxide (OH") are present at the 

ranges of pH in the basins, and thus are not shown in the 

equation. Nitrate retention could account for 43 percent 

of hydrogen consumption in each drainage basin 

(table 8), an indication of the effectiveness with which 

these drainage basins buffer inputs of nitric acid.

Application of Deicing Salts

The significant effect of deicing salt application on 

water quality in Swift River and Fever Brook Basins 

was unexpected. Based on total ionic equivalents for the 

period of study (table 8), deicing salts increased the 

total ionic output flux by 41 percent at Swift River and 

120 percent at Fever Brook. Although nearly all salt was 

applied during a 4-month period in winter, seasonal 

trends of sodium and chloride concentrations in streamflow were not pronounced. At Fever Brook, elevated 

concentrations persisted throughout the year, implying 

that the salt reached the saturated zone and was continually released to the stream by ground-water discharge. 

At Swift River, sodium concentrations varied similarly 

to the other cations, indicating that the seasonal input of 

deicing salt was primarily incorporated in the annual 

ground-water recharge from which it was supplied to 

surface water in a relatively uniform manner throughout 

the year. At Swift River, the significant correlation 

between sodium concentration and discharge was not 

masked by sodium from deicing salts.

Several researchers have investigated the effect of 

deicing salts on water quality. Oberts (1986) found that 

many pollutants were released from sand and salt 

applied to Minnesota highways. Kunkle (1972) examined the movement of salt-contaminated ground water 

generated by runoff from a highway in Vermont. Wilcox

(1986) investigated the effects of leachate from a deicing salt storage pile and runoff from a salted Interstate 

highway on water chemistry in a peat bog in Indiana. 

Known adverse environmental effects of road salting 

include elevated sodium and chloride concentrations in 

water-supply wells (Huling and Hollocher, 1972), 

injury to roadside vegetation (Scharpf and Srago, 1974), 

and alterations to the ecology of wetlands (Wilcox, 

1986). An additional effect determined in this study is 

the potential of deicing salts, through ion exchange, to 

accelerate the leaching of calcium and magnesium from 

soils, thus increasing the adverse effect of acid 

deposition by undermining soil fertility.

At Fever Brook, ion exchange was an important 

factor in the overall effect of deicing salts on water 

chemistry. Sodium in road salt replaced calcium and 

magnesium on exchange sites. As a result, the output 

flux of calcium increased by 75 percent and the output 

flux of magnesium increased by 61 percent (see below). 

A minor part of these increases was caused by small 

amounts of calcium and magnesium impurities in the 

deicing salts; most was caused by ion exchange. Few 

studies, however, have specifically addressed the process of ion exchange in interpreting the effects of deicing salts on water chemistry. Kunkle (1972) alludes to 

the possibility of ion exchange in the Vermont stream 

study. Wilcox (1986) discusses ion exchange in the 

study of the Indiana peat bog, but does not propose it as 

a mechanism to explain the measured increases in base 

cations greater than background concentrations, and the 

excess of chloride over sodium at many of the sampling 

sites. Ion exchange of sodium for calcium and magnesium would in fact be entirely consistent with his 

observations.

Adjustment of Chemical Fluxes

Both drainage basins contained road sections that 

were treated with deicing salts. At Fever Brook, in particular, these salts were the dominant source of solute 

load in the stream. Therefore, to understand the processes controlling stream-water geochemistry in these 

basins, the contribution of the deicing salts to the 

chemical load of the streams needs to be quantified.

Common deicing salt is predominantly sodium 

chloride, with varying but generally minor amounts of 

calcium chloride, magnesium chloride, and calcium sulfate. Other workers (Katz and others, 1985; Yuretich

Factors Affecting Water Quality and Net Flux of Solutes 53
2,500 -

2,000 

LU 

DC

£

o

LU

I

DC 

LU

a.

CO

z

UJ

I

o

UJ

X

B!

UJ

o

CO

1,500 -

1,000 -

500

-

-

-

"

_

_

-

-

-

-

-

Nitrate retention 

24 percent

Potassium weathering 3 percent

Sodium

weathering 

1 5 percent

Magnesium

weathering

14 percent

Calcium

44 percent

Net alkalinity export 

14 percent

Ammonium retention 4 percent

Net sulfate export 

24 percent

Hydrogen

retention

58 percent

-

Nitrate retention 

30 percent

Potassium

weathering

6 percent

Sodium

weathering

Magnesium

weathering

19 percent

Calcium

weathering

34 percent

Net alkalinity

export

1 3 percent

Ammonium retention 4 percent

Net sulfate

export

1 2 Dorcont

Hydrogen

retention

70 percent

_

-

-

-

-

-

-

-

SWIFT RIVER FEVER BROOK

Figure 18. Charge balance for solute fluxes from the West Branch Swift River and East Branch Fever 

Brook Basins, central Massachusetts, December 1983 through August 1985. The left column for each 

site includes cations that had a net export (output in streamflow greater than input in precipitation) 

and anions that had a net retention; the right column includes anions that had a net export and 

cations that had a net retention.

54 Factors Affecting Water Quality and Net Flux of Solutes in Two Stream Basins, Quabbin Reservoir Basin, Central Mass., 1983-85
and Batchelder, 1988) have made corrections for 

deicing salt based on the assumption that the chloride in 

stream water in excess of that accounted for by precipitation was balanced by cations in the ratio that they are 

present in the salt (sulfate impurities generally have 

been ignored). A drawback to this approach is that ionexchange reactions may alter the relative proportion of 

cations that balance the chloride (Kunkle, 1972). This is 

the well-known salt effect, which has been shown to 

cause episodic acidification in areas of thin, acidic soils 

in Norway. The salt effect is the process whereby 

sodium in precipitation exchanges for hydrogen ion on 

soil-exchange sites (Wiklander, 1975; Wright and 

others, 1988). In soils with higher base saturation, the 

salt effect is more likely to be reflected in the exchange 

of sodium for calcium and magnesium. Thus, flux corrections for deicing salts that fail to account for 

exchange reactions may underestimate the natural 

sodium export and overestimate the natural calcium and 

magnesium export.

If the net chloride export in the Fever Brook Basin 

is assumed to be derived from deicing salt, and if the 

cations associated with net chloride export are apportioned based on the stoichiometry of the salt composition, it is readily seen that all of the exported sodium is 

required to match the chloride export (table 7). This calculation implies that sodium from weathering sources is 

negligible, a condition that is inconsistent with the presence of sodic-rich plagioclase in the schist of the 

Rangely Formation, which underlies a large part of the 

basin (Knapp, 1990). Weathering of plagioclase should 

supply an amount of sodium to stream water such that 

the total sodium flux is considerably greater than the 

sodium from deicing salt alone. Because sodium export 

approximately balances chloride export, there must be a 

sink for sodium or, alternatively, an additional source of 

chloride.

Possible additional sources of chloride include a 

chloride-bearing mineral, or a net release of chloride 

from storage. Fever Brook Basin contains considerable 

amounts of hornblende and biotite, both potential 

sources of chloride. Microprobe analyses of hornblende 

from various formations in the north Quabbin area show 

chloride concentrations on the order of 0.01 percent 

(Peter Robinson, University of Massachusetts, oral 

commun., 1990), far too little to be of significance to 

stream chemistry. Analyses of biotite were not 

available, but biotite is less easily weathered and is less

likely to contain significant amounts of chloride, thus it 

likewise is discounted as a source of chloride. Net 

release of chloride from storage is feasible in a wet year, 

such as the first year of the study, but net release is 

unlikely given that the two years prior to the study also 

had greater than average flow for nearby streams 

(Gadoury and others, 1984, 1985). Given the apparent 

lack of a chloride source, there must be a sodium sink; 

this sink is postulated to be the soil cation-exchange 

complex.

Quantitative accounting of ion exchange is difficult because it is a function of the ionic composition of 

the runoff, the cation populations on soil-exchange 

sites, flow path of the runoff, and antecedent soil moisture conditions, all of which vary in space and time. 

Consider sodium and calcium, the major ions involved 

in ion-exchange reactions; if ion exchange is the dominant control on stream chemistry, and all other factors 

were constant, the sodium:calcium ratio in stream water 

would not vary. In Fever Brook, however, the sodium: 

calcium ratio ranges from 1 to 3.5 (equivalent basis). 

Furthermore, variations in the sodium:calcium ratio are 

not linked to season or flow regime.

The pattern of variation in base-cation concentrations at Fever Brook suggests that ion exchange has a 

greater short-term effect on base-cation concentrations 

than that of weathering. Sodium, calcium, and magnesium each have temporally similar patterns of variation 

in concentration that are at variance with the pattern 

observed for silica (fig. 10). If base-cation concentrations are directly controlled by weathering, variations in 

base-cation concentrations should track variations in 

silica concentrations. Although uptake of silica by diatoms may complicate this interpretation, cation 

exchange clearly affects the flux of sodium from applied 

deicing salt. Therefore, a method was developed to 

quantify the exchange and derive the background cation 

fluxes, or those fluxes that would be observed in the 

absence of deicing-salt application.

At Fever Brook, the first step in the salt correction 

was the usual assumption that the chloride flux in excess 

of that from precipitation was due to deicing salts. An 

independent estimate was then made of the sodium flux 

from weathering. The chloride excess was balanced by 

(1) the sodium remaining after adjustment for the estimated amount of sodium from weathering, (2) the 

minor amounts of calcium and magnesium in deicing 

salts, and (3) calcium and magnesium from ion

Factors Affecting Water Quality and Net Flux of Solutes 55
exchange. The amounts of calcium and magnesium 

derived from deicing salt and ion exchange were subtracted from the total fluxes to yield the background 

fluxes. Also an adjustment was made for the small 

amount of sulfate in deicing salt. All adjustments were 

made on a monthly time step.

The estimate of the sodium flux from weathering 

was based on the stoichiometric relation between 

sodium and silica in ground water. At the three groundwater-sampling sites in the Fever Brook Basin, the sodium: silica ratio ranged from 0.25 to 0.51. Three of 11 

samples from the till well (fig. 5, well No. 

422906072124301) had sodium:silica ratios greater 

than 0.8, apparently affected by salt, and were not used 

in the analysis. The remaining eight samples from this 

well had sodium:silica ratios intermediate between 

those of the other two wells sampled. In the adjacent 

Carter and Mundberry Basins, which are underlain by 

the same geologic formations as Fever Brook Basin, 

samples from 10 wells had sodium:silica ratios near 0.5, 

and in no case greater than 1.0 (Knapp, 1990). By contrast, samples from another well in the Carter Basin, 

near a road treated with deicing salt, had sodium: silica 

ratios between 1 and 2. Ground water in this well was 

apparently contaminated with deicing salt, thus this site 

was not considered in the analysis. All analyses from 

the 10 wells at Carter and Mundberry Basins and the 

three wells at the Fever Brook Basin were combined; 

the overall mean sodium: silica ratio (molar basis) was 

0.534± 0.112 (the range represents one standard deviation on either side of the mean). All silica in the stream 

was assumed to be derived from weathering, and thus 

the sodium flux from weathering was calculated from 

the mean sodium: silica ratio, applied to the monthly 

silica fluxes in the stream.

Monthly chloride fluxes were then adjusted for 

chloride in precipitation using the overall ratio of chloride load in precipitation to chloride load in the stream 

using totals from the study period. The adjustment was 

made as follows:

C1net = C1stream x F »

where F = (Clstream - Clppt)/Clstream , 

For Fever Brook, F = 0.923.

The net monthly chloride flux was balanced by five 

components:

Clnet = Nasalt + Casalt + Mgsalt + Caex + Mgex, (17)

where the subscript "salt" denotes a source in the deicing salt and the subscript "ex" denotes a source in the 

soil-exchange complex. Nasajt represents the amount of 

the sodium from applied deicing salts that was not 

retained by ion-exchange reactions. It is calculated by 

deducting the sodium flux from weathering from the 

total sodium flux:

Nasalt = Nastream -Naweathering (18)

Direct inputs of calcium and magnesium to stream 

water from the dissolution of deicing salt (Ca^ and 

Mgsalt) were calculated from Clnet on the basis of the 

relative proportions of Ca and Mg in the composition of 

the applied salt (table 11), including applied CaCl2 (see 

below):

0.0365,

MgSalt = Clnet X 0.0062.

(19)

(20)

Table 11 . Composition of rock salt applied in West 

Branch Swift River and East Branch Fever Brook 

Basins, central Massachusetts

[Percentages may not add to 100 percent due to rounding] 

Percentage of composition

Bv Weight

Compounds

Sodium chloride (NaCl).............................. 97.0

Calcium chloride (CaC^)............................ .5

Magnesium chloride (MgCy..................... 5

Calcium sulfate (CaSO4)............................. 2.0

Bv Equivalents

Cations

Sodium (Na+)............................................... 97.1

Calcium (Ca2+)............................................. 2.2

Magnesium (Mg2+)...................................... .6

Anions

Chloride (Cl-)............................................... 98.3

Sulfate (SO2;) .......................................... 1.7

56 Factors Affecting Water Quality and Net Flux of Solutes in Two Stream Basins, Quabbin Reservoir Basin, Central Mass., 1983-85
Inputs of calcium and magnesium to stream water 

from ion exchange were calculated from the residual 

chloride not balanced by the cations in deicing salt. The 

sum (Caex + Mgex) was calculated from equation 17. 

The individual quantities Caex and Mgex were calculated based on the assumption that calcium and magnesium are released from exchange sites in the same 

relative proportion that they appear in stream loads for 

each month, as follows:

Caex = (Cae Mgex) x (Castream / (Castream 

Mgstream)), (21)

Mgex) x (Mgstream / (Castream + 

Mgstream)) (22)

Thus, the background net flux of sodium reported 

(table 8) was that of the estimated weathering flux; 

background fluxes of calcium and magnesium were 

calculated as the actual measured flux minus the flux 

from exchange and the minor deicing salt contributions. 

An upper and lower bound for the sodium contribution 

was estimated using the standard deviation of the 

sodium: silica ratio, and upper and lower bounds on the 

calcium and magnesium fluxes were calculated accordingly (table 8). Note that an increase in the sodium 

assigned to weathering requires an increase in calcium 

and magnesium from ion exchange, and a resulting 

decrease in the calculated background flux of calcium 

and magnesium. Sulfate was assumed to be 

conservative and also was adjusted based on its 

content in salt and the excess chloride flux.

Comparison of Calculated Salt Export and SaltApplication Data

The estimated total salt application calculated from 

the excess chloride was checked against the salt application records for the State and town highways in the 

basins. If all applied salt reached the stream, the 

amounts should agree. However, errors may arise 

because the application records are not broken down to 

the small scale of the basins in this study, and because 

the salting activity of both State and town must be considered. Nonetheless, a general agreement of the 

amounts would assure that no gross errors have been 

made, such as failing to identify a major internal source 

of chloride.

Salt-application data were obtained from the Massachusetts Department of Public Works, which maintains State Routes 202 and 122 through the Swift River 

and Fever Brook Basins, respectively (table 12). Also, 

the Swift River Basin includes parts of the towns of 

Wendell, Shutesbury, and New Salem, all of which 

maintain town roads in the basin. Of those roads, however, only a part of Louck's Pond Road in Shutesbury is 

salted. Fever Brook Basin is entirely within the town of 

Petersham, where West Road and State Route 32A are 

salted by the town. State salt-application records were 

available on tonnage of rock salt and calcium chloride 

applied per winter per lane mile for maintenance areas 

that included the road segments of interest. A lane mile

At Swift River, deicing salts had a less 

important role in stream chemistry; application 

rates per unit area were lower and natural flux of 

sodium was higher. Thus, deicing salt corrections 

thus were made in the conventional manner 

(table 8). Excess chloride (Clstream-Clppt) simply 

was balanced by cations in the ratio that they 

occur in the deicing salts. Cation ratios were 

somewhat different at Swift River because of the 

higher percentage of calcium chloride in the 

applied salt (see below). Sulfate flux was corrected in like manner. Corrections were made on 

total fluxes for each water year.

Table 12. Deicing salt-application data, West Branch 

Swift River and East Branch Fever Brook Basins, central 

Massachusetts

[All values in megagrams]

Salt type

Swift River Fever Brook

1983-84 1984-85 1983-84 1984-85

Town rock salt 

State rock salt

2.01 

70.57

2.01 

49.55

4.88 

109.36

5.00 

106.84

State calcium 

chloride (CaCl2) 1.79 1.87 1.53 1.53

Factors Affecting Water Quality and Net Flux of Solutes 57
Table 13. Chloride load in applied deicing salt and net chloride flux from West Branch Swift River 

and East Branch Fever Brook Basins, December 1983 through August 1985, central 

Massachusetts

[All values, except percent, in equivalents per hectare]

Basin Chloride input Chloride output Chloride flux Chloride load in 

(precipitation) (stream) (net) applied deicing salt

Percentage of deicing

salt exported in

streamflow

West Branch 

Swift River.. .......

East Branch 

Fever Brook.......

..... 184

..... 184

1,132

2,397

948

2,213

655

3,078

145

72

is defined as a mile of paved roadway 12 ft wide; thus a 

1-mile section of two-lane highway with paved shoulders and an entire paved width of 36 ft has 3 lane miles. 

For each basin, the roadway segment of interest represented about 5 percent of the roadway in the corresponding maintenance area. Salt application was 

assumed to be uniform, and the tonnage of applied salt 

was prorated according to the number of lane miles of 

State road in each basin. A chemical analysis of the rock 

salt was obtained from the supplier, and the calcium 

chloride, which was used in minor amounts, was 

assumed to be pure. Calculations were made in a similar 

manner for the town roads; the estimate of the total 

amount of salt applied was prorated for the fraction of 

town road in the basins relative to the total amount of 

town road salted. Rock-salt composition again was 

obtained from the supplier. Salt application by the 

towns was minor relative to amounts applied by the 

State.

On the basis of net chloride flux, salt export from 

Fever Brook Basin was slightly more than two-thirds of 

the amount applied, whereas salt export from Swift 

River Basin was 45 percent more than the amount 

applied (table 13). Although the discrepancies between 

applied and transported salt appear large, the discrepancies probably are within the error introduced by the 

assumption of uniform salt-application rates. Differences in salt-application history probably do not 

account for the discrepancies, because in each basin, the 

annual salt application during the 2-year study period 

was nearly exactly average for the 1975-85 period (Sam 

Pollock, Massachusetts Department of Public Works, 

written commun., 1990). The higher percentage of wetlands at Fever Brook relative to Swift River Basin may 

attenuate annual variations in the chloride flux through

longer water residence times. Cherkauer (1977) found 

that deicing salts in runoff were stored in impoundments, attenuating salt loads in spring runoff and releasing salt to runoff during summer storms. The net salt 

retention at Fever Brook thus may reflect a net loss of 

salt to storage following the unusually low salt application in the winter of 1982-83. Although there was about 

the same amount of salted roadway in each basin, the 

effect of salting is greater in Fever Brook because it has 

less than one-half the drainage area and approximately 

double the salt-application rate of Swift River. The calculated retention at Fever Brook may be within the error 

of the calculated application amounts.

ACIDIFICATION STATUS OF THE BASINS

The acidification status of Swift River and Fever 

Brook was explored by use of an approach developed 

by Henriksen (1980) and modified by Dillon and others 

(1980). Henriksen defined acidification as the quantitative difference between historic and present-day alkalinity. On the basis of the chemistry of pristine 

freshwaters sampled throughout the world, Henriksen 

observed that the sum of the major weathering base cations, predominantly calcium and magnesium, virtually 

equaled alkalinity. This relation results if carbonic acid 

is the primary agent in mineral-weathering reactions; 

one equivalent of bicarbonate and one equivalent of 

base cations are yielded to solution for each mole of carbonic acid consumed in the reaction. Thus, Henriksen 

estimated historic alkalinity to be the sum of equivalents 

of calcium and magnesium and he attributed this 

amount to mineral weathering by carbonic acid. Using 

this approach, one can infer the effect of sulfuric acid in 

weathering reactions by the deviation from the idealized

58 Factors Affecting Water Quality and Net Flux of Solutes in Two Stream Basins, Quabbin Reservoir Basin, Central Mass., 1983-85
one-to-one relation of stream alkalinity to base cations. 

The addition of sulfuric acid can cause one of two 

chemical responses in a drainage basin. One response 

may be that sulfuric acid increases the rate of weathering simply by adding to the amount of weathering by 

carbonic acid. One equivalent of sulfuric acid will react 

to produce one equivalent of base cations in solution, 

and transport of base cations would be increased onefor-one relative to an original level. For example, consider an unaffected drainage basin in which the annual 

net flux of base cations of 100 eq (equivalents), balanced by a net flux of 100 eq of alkalinity. If 50 eq of 

sulfuric acid are introduced and reacted in the system, 

the net flux of base cations would be 150 eq, alkalinity 

would still be 100 eq, and the net flux of sulfate would 

be 50 eq. This appears to be occurring in many drainage 

basins, though commonly the source of base cations 

may be the ion-exchange complex rather than mineral 

weathering. A second response of a drainage basin may 

be that sulfuric acid does not increase the rate of mineral 

weathering. Minerals are dissolved by carbonic acid, 

which yields cations and bicarbonate to the water. The 

sulfuric acid does not cause weathering, but it reacts 

with and neutralizes the alkalinity. The result is 

decreased alkalinity. For example, in the system just 

described, 100 eq of base cations and 100 eq of alkalinity would be produced by weathering with 100 eq of 

carbonic acid. The 50 eq of added sulfuric acid would 

neutralize 50 eq of alkalinity so that alkalinity would 

decrease from 100 to 50 eq. Net export would be 100 eq 

of base cations, and 50 eq each of alkalinity and sulfate.

Consistent with the observations of Henriksen 

(1980), calcium and magnesium were the major cations 

produced by weathering at Swift River and Fever Brook 

Basins. Plots of the relations among calcium, magnesium, alkalinity, and sulfate at Swift River and Fever 

Brook illustrate Henriksen's theory (fig. 19). The theoretical concentrations resulting from simple carbonic 

acid weathering is illustrated by a one-to-one relation 

between alkalinity and calcium plus magnesium (figs. 

19A and 195). In each basin, all stream samples plot 

below the theoretical carbonic acid weathering line, an 

indication of the deficit of alkalinity relative to weathering base cations. A second set of plots (fig. 19C and 

19D) incorporate the concept of stream sulfate as a 

balancing anion (Dillon and others, 1980). There was a

shift in the plot toward the theoretical weathering line 

(figs. 19C and 19D) when sulfate concentrations were 

included in the chemical balance.

Assuming that the rate of transport of base cations 

measured during this study is equal to the rate before 

acid deposition, then mineral acids entering the basins 

in wet and dry deposition are reacting with and consuming alkalinity. This condition would imply that the 

streams are showing signs of acidification. If, however, 

alkalinity has remained constant through time, then sulfuric acid inputs have increased the rate of weathering 

(or the rate of depletion of base saturation) in the drainage basins. At Swift River and Fever Brook, calcium 

and magnesium concentrations are balanced by alkalinity and sulfate, but this does not indicate whether the 

rate of weathering has increased or whether alkalinity 

has been consumed by sulfuric acid.

The chemical budget of solutes entering a basin as 

wet deposition and leaving by streamflow is useful in 

interpreting drainage basin interactions that may affect 

the degree of acidification in a drainage basin. The net 

fluxes of chemical solutes can be used graphically to 

depict a mass balance of the sources of alkalinity and 

acidity (Eshleman and Hemond, 1985). Terms in the 

alkalinity equation (eq. 15) are quantified in a vertical 

bar graph (fig. 18). Sources of alkalinity, which are primarily weathering reactions, are shown as the left bar of 

each pair; sources of acidity are to the right. Ideally, if 

all ionic species were measured without error, the 

heights of the alkalinity and acidity flux bars would be 

the same. The slight differences noted may be attributed 

to organic acid anions, which were not measured.

Sulfuric acid from precipitation clearly is a major 

factor in the chemical quality of the streams. Net transport of sulfate in the Swift River Basin could account 

for as much as 33 percent of the transport of base cations 

derived from weathering, including calcium, magnesium, sodium, and potassium. Reduction of sulfate in 

the Fever Brook Basin may mask the full extent that sulfuric acid affects base-cation transport in that drainage 

basin. On the basis of net flux, as much as 17 percent of 

base-cation transport may be associated with sulfate 

flux in Fever Brook.

Acidification Status of the Basins 59
IOU

INCENTRATION, IN 

LENTS PERLITER

o o

O < 

O >

18 »

§0

°<

200

- UJ 150

IE

cr ^ 

£j ui 1 °°

0 >

u o

ID 0 50 

n

I I / I I

A> / 0

Swift River / u

0

/ O

Expected concentrations ^ 

from carbonic acid weathering 

in the absence of atmospheric O 

sulfate inputs OQ V °°°

V

" 1 o tf

/ o S&°

1 1 dS^* ! 1 1

I I /I I I

BFever Brook /

/ 0

/ o 

o

/ QD / O (j

I 0 0^ ^>0

/ fff^

I i P i i i

) 50 100 150 200 250 300 0 50 100 150 200 250 30 

CALCIUM PLUS MAGNESIUM CONCENTRATION, IN MICROEQUIVALENTS PER LITER

i i i y

C. / 

Swift River Q QO<§> ° /

oc^^/

o o/o 

o 7

0 /

' Balance of concentrations

/ between calcium plus 

_ / magnesium and alkalinity 

, plus sulfate

/ \ I I

i i \ /

D. /

Fever Brook O 9)

c8^°i> °"

s* °?

^^OD a °

/o o o

/8 °

/ \ \ \

0 50 100 150 200 0 50 100 150 200 

CALCIUM PLUS MAGNESIUM-ALKALINITY CONCENTRATION, IN MICROEQUIVALENTS PER LITER

Figure 19. Relations between calcium plus magnesium concentrations and major anion solutes in 

stream water in the West Branch Swift River and East Branch Fever Brook, central Massachusetts.

60 Factors Affecting Water Quality and Net Flux of Solutes in Two Stream Basins, Quabbin Reservoir Basin, Central Mass., 1983-85
SUMMARY AND CONCLUSIONS

In cooperation with the Metropolitan District 

Commission and the Massachusetts Department of 

Environmental Protection, the U.S. Geological Survey 

conducted an investigation in the Quabbin Reservoir 

Basin from December 1983 through August 1985. The 

purpose of the study was to determine the processes 

that affect water quality and solute fluxes in two inlet 

streams to the reservoir the major water source for 

metropolitan Boston. In the Swift River and Fever 

Brook Basins, measurements were made of streamflow 

and precipitation quantity and quality as well as 

ground-water quality. Data from these measurements 

were interpreted to assess the effect of acid precipitation, road salting, basin hydrology, sulfate adsorption, 

aluminum geochemistry, and other factors on streamwater quality and solute fluxes. The scientific findings 

of the study are intended to help guide water-resources 

management of the drainage basin, such that the high 

water quality in the Quabbin Reservoir is maintained.

Processes in the Swift River and Fever Brook 

Basins, central Massachusetts, neutralized inputs of 

dilute sulfuric and nitric acids in precipitation to a moderately buffered solution enriched in base cations and 

silica in stream water. Inputs of hydrogen ion and nitrate 

in precipitation were nearly completely retained in both 

basins. The most likely causes for this retention are 

assimilation of nitrate by the biota, and exchange of 

hydrogen ion for base cations in the soil. In contrast, 

each basin had a net export of sulfate relative to inputs 

in wet deposition. At Swift River, sulfate export 

exceeded the input of sulfate in wet deposition by 63 

percent. This percentage is near the amount typically 

attributed to dry deposition of sulfate in the northeastern 

United States; thus, sulfate outputs were in approximate 

balance with inputs. The sulfate adsorption capacity of 

the soils in Swift River appears to be saturated. At Fever 

Brook, sulfate export was 29 percent greater than inputs 

in wet deposition. Accounting for dry deposition, there 

probably was some net retention of sulfate in the basin. 

Sulfate retention at Fever Brook was attributed to sulfate reduction in the wetland areas. In both basins, 

export of base cations, derived from mineral weathering 

and ion-exchange processes, greatly exceeded inputs in 

atmospheric deposition. Somewhat more alkalinity was 

produced in the Swift River Basin from higher

weathering rates, but this was approximately matched at 

Fever Brook Basin by sulfate reduction, so that 

alkalinity was about the same in each basin.

The different chemical responses in the Swift 

River and Fever Brook Basins were caused, in part, by 

differences in hydrology. Of the two streams, Swift 

River responded more rapidly to rain and snowmelt 

because of the more rugged topography. Despite a basin 

area more than two times greater than Fever Brook, discharge peaks (normalized to basin area) associated with 

most storms were greater at Swift River. The initial 

hydrograph recession was more rapid at Swift River, but 

then stabilized to sustain considerably higher base-flow 

levels, whereas flow at Fever Brook continued to 

recede. Estimates of base-flow discharge during the 21- 

month study were 53 percent at Swift River compared 

to 42 percent at Fever Brook. Total runoff was 48 percent at Swift River compared to 41 percent at Fever 

Brook. Thus, despite a rapid hydrologic response, there 

is an important ground-water component to streamflow 

at Swift River. The lower percentage of runoff at Fever 

Brook was caused in part by evaporation from the 

extensive wetland areas in that basin. The surface storage reservoir appeared to have a greater effect on the 

ground-water storage reservoir in the hydrologic 

response at Fever Brook.

At Swift River, base cations were inversely correlated with discharge. Similar patterns of concentration 

variations of base cations and silica suggested that base 

cations primarily were derived from mineral weathering; concentrations diluted moderately at high flows and 

increased in summer when ground-water discharge 

dominated flow. At Fever Brook, base-cation concentrations were somewhat more variable, and the dilution of 

silica was much greater during high flow in spring, possibly reflecting elevated silica concentrations from 

diatom blooms in the impoundments. The high percentage of wetland areas and the major effect of deicing 

salts on stream chemistry at Fever Brook caused poor 

correlations of solute concentrations and discharge. 

Whereas concentrations of most base cations peaked in 

late summer, potassium concentrations at each site 

peaked later in the autumn, in association with leaf fall. 

At Swift River, sulfate concentrations were relatively 

constant, whereas at Fever Brook, sulfate concentrations decreased in summer when sulfate reduction 

occurred. During summer and early autumn at each site, 

alkalinity increased from less than 50 to near 150 jneq/L

Summary and Conclusions 61
as base-cation concentrations increased and sulfate 

concentrations remained relatively constant or 

decreased.

Differences in the relative amounts of base cations 

(after subtracting the contributions of road deicing salts) 

and silica in the two streams suggest differences in the 

important mineral weathering reactions. At Swift River, 

net fluxes exceeded those at Fever Brook by 58 percent 

for silica and 41 percent for base cations. The disproportionately greater export of silica and calcium and the 

higher calcium:magnesium ratio at Swift River suggest 

that plagioclase weathering is more important at Swift 

River, and hornblende weathering is more important at 

Fever Brook. The overall weathering rate appears to be 

greater at Swift River because of a higher proportion of 

ground-water discharge relative to Fever Brook, and 

also due to the presence in one subbasin of easily weathered gabbro bedrock composed of hornblende and calcium feldspar. This subbasin comprises only 11.2 

percent of the total Swift River Basin area but 

contributes nearly 25 percent of the total base cations, 

16 percent of the total silica, and 77 percent of the total 

alkalinity exported from the basin.

In contrast to the other solutes, hydrogen ion and 

aluminum tended to increase in concentration with 

increasing discharge, reflecting the mixing of runoff 

from the more acidic rain and snowmelt waters with 

base flow. Rapid runoff from steep slopes in the Swift 

River Basin limited the degree to which acid was neutralized, resulting in episodic increases of aluminum 

concentration in the stream. As the ground-water component of stream discharge increased, pH and alkalinity 

increased and aluminum concentration decreased. 

Although baseline concentrations of hydrogen ion, 

DOC, and aluminum were higher at Fever Brook than at 

Swift River because of organic acidity generated in the 

wetlands, episodic increases of hydrogen ion and aluminum were more frequent at Swift River. In both streams, 

aluminum increased from less than 100 to nearly 

300 |J.g/L during some high-discharge events. Because 

of the high DOC at Fever Brook, aluminum is likely to 

be organically bound and thus nontoxic.

Deicing salt application had a major effect on 

water quality in Swift River and Fever Brook Basins. 

Deicing salts increased the total ionic output flux by 41 

percent at Swift River and 120 percent at Fever Brook. 

At Fever Brook, sodium in deicing salt exchanged with 

calcium and magnesium in the soil. The combined

effects of loading in the applied salt and ion exchange in 

the soil caused increases in the output fluxes by 33 percent for calcium and 24 percent for magnesium. This 

ion exchange effect could promote soil infertility and 

soil acidification through the accelerated leaching of 

calcium and magnesium from soils.

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