U.S. Department of the Interior

U.S. Geological Survey

Scientific Investigations Report 2004-5018

Hydrogeology and Water Quality of the Pepacton 

Reservoir Watershed in Southeastern New York

Part 4. Quantity and Quality of Ground-Water and Tributary Contributions to Stream 

Base Flow in Selected Main-Valley Reaches

In cooperation with

NEW YORK STATE DEPARTMENT OF ENVIRONMENTAL CONSERVATION
This page has been left blank intentionally.
Hydrogeology and Water Quality of the Pepacton 

Reservoir Watershed in Southeastern New York

Part 4. Quantity and Quality of Ground-Water and 

Tributary Contributions to Stream Base Flow in 

Selected Main-Valley Reaches

By Paul M. Heisig

In Cooperation with New York State Department of Environmental Conservation

Scientific Investigations Report 2004-5018

U.S. Department of the Interior

U.S. Geological Survey
U.S. Department of the Interior

Gale A. Norton, Secretary

U.S. Geological Survey

Charles G. Groat, Director

U.S. Geological Survey, Reston, Virginia: 2004

For additional information about this report write to:

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Although this report is in the public domain, permission must be secured from the individual copyright owners to 

reproduce any copyrighted materials contained within this report.
iii

Contents

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

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

Purpose and Scope ............................................................................................................................. 2

Previous Investigations ...................................................................................................................... 3

Acknowledgments ............................................................................................................................... 4

Study Area ..................................................................................................................................................... 4

Approach and Methods ............................................................................................................................... 4

Valley-Reach Selection ...................................................................................................................... 5

Base-Flow Surveys .............................................................................................................................. 5

Field Measurements ............................................................................................................................ 6

Water Sampling and Analysis ............................................................................................................ 6

Estimation of Tributary Streamflow and Water Quality ................................................................ 7

Mass-Balance Calculation of Ground-Water Quality .................................................................... 8

Potential Errors in Estimates of Ground-Water Discharge and Water Type ............................ 8

Ground-Water and Tributary Contributions to Stream Base Flow in Selected MainValley Reaches ................................................................................................................................ 9

Quantity of Water ................................................................................................................................. 9

Relation Between Streamflow Gain and Annual Runoff Volume ........................................ 9

Ground-Water Discharge in Relation to Tributary Inflow .................................................. 11

Differences in Tributary Inflow Among Valley Reaches ..................................................... 11

Quality of Water ................................................................................................................................. 11

General Water-Type Classification ........................................................................................ 13

Waters Affected By Road Salt and Nutrients ...................................................................... 13

Chloride and Sodium Sources and Concentrations ................................................... 13

Nitrate and Orthophosphate Sources and Concentrations ...................................... 17

Summary ...................................................................................................................................................... 17

References Cited ........................................................................................................................................ 18

Appendix ...................................................................................................................................................... 19

Figures

1. Locations of valley-reach study sites, stream-gaging stations, and weather stations in 

the Pepacton Reservoir watershed in southeastern New York ...................................................... 3

2. Stream stage at four USGS stream-gaging stations within the Pepacton watershed 

during the July and August 2001 valley-reach surveys ..................................................................... 6

3. Total streamflow gain within the nine valley reaches as a function of annual runoff 

volume from their respective valley-reach drainage areas (not including headwater

drainage area upvalley from valley reach), Pepacton watershed, southeastern N.Y. , 

July and August 2001. ............................................................................................................................ 10

4. Ground-water-discharge and tributary-inflow contributions to total streamflow gain in 

the nine valley reaches, Pepacton watershed in southeastern New York, July and 

August 2001 ............................................................................................................................................. 12
iv

5. Relative discharge magnitude, water type, concentration of chloride, nitrate, and 

orthophosphate in streamflow and ground-water discharge, and land uses that might 

affect ground-water quality in each reach studied in Pepacton watershed, southeastern 

N.Y. , July and August 2001 ................................................................................................................... 14

6. Generalized valley reach (upland tributary drainage area is omitted) showing migration 

of road-salt leachate to shallow ground water and the adjacent valley stream ........................ 16

Tables

1. Drainage-area and runoff data on valley reaches in Pepacton watershed in 

southeastern New York .......................................................................................................................... 5

2. Discharge increases in valley-reach streams, contributions from tributaries, and 

calculated ground-water discharge to valley reaches in Pepacton watershed in Catskill 

region of southeastern New York, July and August 2001 ................................................................. 7

Multiply By To obtain

Length

inch (in.) 2.54 centimeter (cm)

inch (in.) 25.4 millimeter (mm)

foot (ft) 0.3048 meter (m)

mile (mi) 1.609 kilometer (km)

Area

square mile (mi2) 2.590 square kilometer (km2) 

Volume

million gallons (Mgal) 3,785 cubic meter (m3)

cubic foot (ft3) 0.02832 cubic meter (m3) 

Flow rate

cubic foot per second (ft3/s) 0.02832 cubic meter per second (m3/s)

inch per year (in/yr) 25.4 millimeter per year (mm/yr)

Temperature in degrees Celsius (°C) may be converted to degrees Fahrenheit (°F) as follows:

 °F=(1.8×°C)+32

Temperature in degrees Fahrenheit (°F) may be converted to degrees Celsius (°C) as follows:

 °C=(°F-32)/1.8

Vertical coordinate information is referenced to the North American Vertical Datum of 1988 

(NAVD 88).

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

Altitude, as used in this report, refers to distance above the vertical datum.

Specific conductance is given in microsiemens per centimeter at 25 degrees Celsius 

(μS/cm at 25 °C).

Concentrations of chemical constituents in water are given either in milligrams per liter (mg/L) 

or micrograms per liter (μg/L).

Conversion Factors and Abbreviations
Hydrogeology and Water Quality of the Pepacton Reservoir 

Watershed in Southeastern New York

Part 4. Quantity and Quality of Ground-Water and Tributary 

Contributions to Stream Base Flow in Selected Main-Valley Reaches

By Paul M. Heisig

The total gain in streamflow from the upper end to the 

lower end of each valley reach was positively correlated with 

the annual-runoff volume calculated for the drainage area 

of the reach. This correlation was not greatly affected by 

the proportions of ground-water and tributary contributions, 

except at two reaches that lost much of their tributary flow 

after the July survey. In these reaches, the gain in total 

streamflow showed a negative departure from this correlation.

Calculated ground-water discharge exceeded the total 

tributary inflow in each valley reach in both surveys. Groundwater discharge, as a percentage of streamflow gain, was 

greatest among reaches in wide valleys (about 1,000-ft wide 

valley floors) that contain permeable valley fill because 

tributary flows were seasonally diminished or absent as 

a result of streambed infiltration. Tributary inflows, as a 

percentage of streamflow gain, were highest in reaches of 

narrow valleys (200-500-ft wide valley floors) with little 

valley fill and high annual runoff. 

Stream-water and ground-water quality were 

characterized by major-ion type as either (1) naturally 

occurring water types, relatively unaffected by road salt, or (2) 

road-salt-affected water types having elevated concentrations 

of chloride and sodium. The naturally occurring waters were 

typically the calcium-bicarbonate type, but some contained 

magnesium and (or) sulfate as secondary ions. Magnesium 

concentration in base flow is probably related to the amount of 

till and its carbonate content, or to the amount of lime used on 

cultivated fields within a drainage area. Sulfate was a defining 

ion only in dilute waters (with short or unreactive flow paths) 

with low concentrations of bicarbonate. Nearly all tributary 

waters were classified as naturally occurring water types.

Ground-water discharge from nearly all valley 

reaches that contain State or county highways had elevated 

concentrations of chloride and sodium. The mean chloride 

concentrations of ground-water discharge—from 8 to 13 

milligrams per liter — did not exceed Federal or State 

standards, but were about 5 times higher than naturally 

occurring levels. Application of road salt along a valley 

Abstract 

Estimates of the quantity and quality of ground-water 

discharge from valley-fill deposits were calculated for nine 

valley reaches within the Pepacton watershed in southeastern 

New York in July and August of 2001. Streamflow and water 

quality at the upstream and downstream end of each reach 

and at intervening tributaries were measured under base-flow 

conditions and used in mass-balance equations to determine 

quantity and quality of ground-water discharge. These 

measurements and estimates define the relative magnitudes 

of upland (tributary inflow) and valley-fill (ground-water 

discharge) contributions to the main-valley streams and 

provide a basis for understanding the effects of hydrogeologic 

setting on these contributions. Estimates of the water-quality 

of ground-water discharge also provide an indication of the 

effects of road salt, manure, and human wastewater from 

villages on the water quality of streams that feed the Pepacton 

Reservoir. The most common contaminant in ground-water 

discharge was chloride from road salt; concentrations were 

less than 15 mg/L. 

Investigation of ground-water quality within a large 

watershed by measurement of stream base-flow quantity and 

quality followed by mass-balance calculations has benefits 

and drawbacks in comparison to direct ground-water sampling 

from wells. First, sampling streams is far less expensive than 

siting, installing, and sampling a watershed-wide network of 

wells. Second, base-flow samples represent composite samples 

of ground-water discharge from the most active part of the 

ground-water flow system across a drainage area, whereas 

a well network would only be representative of discrete 

points within local ground-water flow systems. Drawbacks 

to this method include limited reach selection because of 

unfavorable or unrepresentative hydrologic conditions, 

potential errors associated with a large number of streamflow 

and water-quality measurements, and limited ability to 

estimate concentrations of nonconservative constituents such 

as nutrients.
bottom probably affects only the shallow ground water in the 

area between a road and a stream. The elevated concentrations 

of chloride and sodium in the base-flow samples from such 

reaches indicate that the concentrations in the affected ground 

water were high enough to offset the low concentrations in all 

unaffected ground water entering the reach.

Nutrient (nitrate and orthophosphate) concentrations 

in base-flow samples collected throughout the valleyreach network could not generally be used to estimate their 

concentrations in ground-water discharge because these 

constituents can be transformed or removed from water 

through biological uptake, transformation, or by adsorption on 

sediments. Base-flow samples from streams with upgradient 

manure sources or villages served by septic systems 

consistently had the highest concentrations of these nutrients.

Introduction

Maintenance of the quality of water from upstate 

reservoirs that provide New York City’s water supply is a 

concern because degradation of water quality could result 

in the need for costly filtration, under the Surface Water 

Treatment Rule of the Safe Drinking Water Act (Public Law 

104-82). A variety of land-use activities occur within reservoir 

watershed areas, including some that may adversely affect 

the water quality of streams that supply the reservoirs. The 

New York State Department of Environmental Conservation 

(NYSDEC) is charged, under the requirements of the Federal 

Clean Water Act, section 305(b), with providing data to the 

United States Environmental Protection Agency (USEPA) 

on the quality of surface waters and ground waters of New 

York State. The Pepacton Reservoir watershed in the western 

Catskill Mountains (fig. 1) was selected by NYSDEC for 

hydrologic investigation because it had received much less 

study than the neighboring, and more intensely farmed, 

Cannonsville Reservoir watershed to the west. In 2000, 

the U.S. Geological Survey (USGS), in cooperation with 

NYSDEC, began a 2-year study to evaluate the quality 

of ground-water discharge to streams in reaches of major 

valleys (this report) and in smaller upland basins (Heisig and 

Phillips, 2004; Phillips and Heisig, 2004) within the Pepacton 

watershed. Surficial geology and recharge estimates within 

the Pepacton watershed were addressed in a concurrent USGS 

study (Reynolds, 2004). 

Base flow (dry-weather streamflow) is derived from 

ground-water discharge from springs and from direct 

seepage into stream channels. Therefore, any net change in 

stream-water quality between the upper and lower ends of a 

given stream reach (barring tributary inflow or point-source 

contamination) is a function of the composite water quality of 

ground water discharged to the stream within that reach. The 

quality of ground-water discharge will reflect the presence or 

absence of non-point sources such as road-deicing salts and 

human and animal wastes, especially in the valley-bottom area 

of a reach. 

The quality of shallow ground water in valley-fill 

deposits could be estimated through chemical analysis 

of water samples collected from a network of wells at 

appropriate locations along valley streams, but the installation 

of a well network for evaluation of shallow ground-water 

quality throughout the Pepacton watershed would be 

prohibitively expensive. In addition, it also would provide 

data only from isolated points and would thereby give a 

limited representation of the spatial variations in groundwater quality within the watershed. Instead, the chemical 

composition of ground-water discharge from valley-bottom 

deposits across the watershed was estimated from surfacewater measurements of flow and chemical quality. A baseflow sample can represent a composite sample of shallow 

ground-water discharge upstream of a sample site. Shallow 

ground water is susceptible to nonpoint-source contamination, 

especially in valley-bottom areas. 

The study entailed (1) selection of nine valley-stream 

reaches, (2) measurement of streamflow and major-ion 

concentrations at the upstream and downstream ends of 

each reach, (3) measurement of streamflow and major-ion 

concentrations of tributary flow entering each valley reach 

(or estimation of major-ion concentrations from specific 

conductance measurements), and (4) application of these data 

to mass-balance equations to estimate the amount of groundwater discharge and the concentrations of the selected groundwater constituents. Streamflow measurements and water 

sampling were carried out during two base-flow surveys—July 

10-17 and August 7-8, 2001. 

The mass-balance technique used in this study was 

best suited for estimating concentrations of conservative 

(unreactive) constituents. This technique is unreliable for 

estimating concentrations of nonconservative (chemically 

reactive) constituents, or of constituents with small 

concentration ranges. This technique is also unlikely to detect 

individual or widely spaced point sources of contamination. 

Purpose and Scope

This report (1) documents the results of base-flow 

sampling from selected reaches of nine major-valley streams 

and their associated tributaries; (2) presents calculated 

ground-water discharges within each reach for the July and 

August surveys of 2001; (3) evaluates ground-water discharge 

in relation to (a) annual runoff within the drainage area of 

each reach, and (b) the width and general permeability of 

unconsolidated material in the valley bottom (valley fill) within 

each reach; (4) classifies the chemical composition of baseflow samples and ground-water discharge according to water 

type (major ions) and interprets them in relation to land use, 

including roads, which are salted in the winter, and (5) relates 

the occurrence of selected constituents (chloride and sodium, 

nitrate, and orthophosphate) to their most likely sources. 

2 Hydrogeology and Water Quality of the Pepacton Reservoir Watershed in Southeastern New York Part 4
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Figure 1. Locations of valley-reach study sites, stream-gaging stations, and weather stations in the Pepacton Reservoir 

watershed in southeastern New York. 

Previous Investigations

Previous investigations that pertain to water resources 

in the Pepacton watershed have described the geologic 

framework of the area, and the low-flow characteristics 

of streams and tributaries within the region. Bedrock and 

the thickness and type of glacial deposits and within the 

Pepacton Reservoir area was discussed by Fluhr (1953), and 

ground-water resources of Delaware County were discussed 

by Soren (1963). Glacial geology and deglaciation in the 

western Catskill Mountains was discussed by Kirkland (1973) 

and Ozvath (1985). The effects of hydrology, geology, and 

geomorphology on low-flow characteristics of streams in the 

Delaware and Susquehanna River basins in New York were 

analyzed by Coates (1971). Infiltration of water from tributary 

streams as they enter larger valleys in the Susquehanna River 

Basin in New York was detailed by Randall (1978). 

Introduction 3
Acknowledgments

Thanks are extended to the landowners for access to their 

properties, and especially to Robert Bond and the Tuscarora 

Club for access to club lands in the Mill Brook basin. 

Thanks also are extended to State, county, and town highway 

superintendents that provided information on road-salt 

usage and practices. USGS staff members Daniel Edwards, 

Kevin Reisig, Thomas Suleski, and Brett Phillips, assisted in 

sample collection and stream-discharge measurements, and 

Krysta Button, Julia Guastella, Hannah Ingleston, and Patrick 

Phillips, processed the water samples.

Study Area

The Pepacton Reservoir watershed encompasses an 

area of 372 mi2 within the western Catskill Mountains of 

southeastern New York. It is largely rural and is drained by 

the East Branch Delaware River, which is impounded in 

the Pepacton Reservoir by the dam at Downsville (fig. 1). 

Maximum relief is about 2,800 ft. Runoff (precipitation 

minus evapotranspiration) ranges from 22 to 40 in/yr; 

the highest rates are associated with the highest mountains 

along the southeastern and eastern edges of the watershed 

(Randall, 1996).

The bedrock consists of nearly flat-lying sandstone, 

siltstone, shale, and conglomerate of Devonian age that 

is overlain by discontinuous glacial and alluvial deposits 

(Fisher and others, 1970). Cliff-forming sandstone and 

conglomerate are commonly interbedded with less resistant 

shale and siltstone; this produces a step-like alternation of 

near-vertical and gentle slopes on upper hillsides. The most 

common glacial deposit in upland areas is till, which is 

nearly continuous on low slopes and thin or absent on steep 

hillsides. Thick till deposits are common on the lee (typically 

south) side of hills relative to the direction of ice movement 

during glaciation (Coates, 1966). Deposits within the main 

valleys (herein referred to as valley fill) typically consist of 

postglacial alluvium, including alluvial fans, and are underlain 

and locally bordered by stratified drift that was deposited 

by glacial meltwater as outwash or ice-contact deposits. Till 

commonly underlies the stratified drift above the bedrock 

surface (Fluhr, 1953). 

Most streams in the large valleys flow over valley-fill 

deposits. Two exceptions are the Batavia Kill and especially 

Mill Brook, which flow over bedrock in their lower reaches 

near their confluence with the East Branch Delaware River 

(fig. 1). Mill Brook valley is oriented east-west and appears 

to contain thick till deposits that have shifted the stream 

course to the south side of the valley (A. Randall, USGS, oral 

communication, 2003). Bedrock has been exposed and incised 

by stream erosion along the lower 3 mi of Mill Brook (fig. 1). 

The elevation difference between the Batavia Kill valley and 

East Branch Delaware River valley has resulted in headward 

erosion up the Batavia Kill valley and exposure of bedrock in 

a 0.25-mi reach of the channel. 

Land use within the uplands differs considerably from 

that along the valley bottoms. The uplands are dominated by 

forest and former farmland that is reverting to forest, as well 

as low-density residential development and hayfields. Dairy 

farms were formerly widespread in these areas but now remain 

in only a few small upland subbasins. The valley-bottom 

areas, in contrast, have long been the focus of human activity 

because the soils are favorable for agriculture, the land is level 

and suitable for building and transportation, and the streams 

are a ready supply of water. The valley-bottom areas contain 

all of the villages and major roads, and much of the remaining 

farmland, including dairy farms and inactive farmland. Lowdensity residential development follows the main roads out of 

the villages. 

Rainfall within the Pepacton watershed was measured 

at the National Weather Service stations at Arkville and 

Downsville (fig. 1) throughout the study. The maximum 

July and August monthly total rainfall differences between 

the two stations exceeded 1 in., and flows at stream-gaging 

stations within the watershed (fig. 1) differed in their response 

to storms (see fig. 4, further on). Rainfall at the Arkville 

station was 0.3 in. above the long-term mean (54 years of 

record) in July 2001 and 1.25 in. below the mean in August 

2001 (Cornell University Northeast Regional Climate Center, 

written commun., 2002). Annual amounts of runoff from 

the drainage area of each of the nine stream reaches are 

summarized in table 1.

Approach and Methods

The amount of ground-water discharge and its 

chemical composition in each of nine valley reaches were 

determined with mass-balance calculations based on (1) the 

measured difference between streamflow at the upstream 

and downstream ends of each reach, (2) the measured 

difference between major-ion concentrations at the upstream 

and downstream ends of each reach, and (3) measured 

or estimated streamflow from tributaries to each reach 

(inflow) and measured or estimated chemical concentrations. 

Tributary concentration estimates were derived from specific 

conductance measurements. The streamflow measurements 

and water sampling were done during July 10-17 and August 

7-8, 2001.

Average annual runoff, in inches, within each valleyreach area was derived from a map by Randall (1996). 

These values were multiplied by their respective drainage 

areas to obtain annual volumes (in cubic ft) of water available 

to streams.

4 Hydrogeology and Water Quality of the Pepacton Reservoir Watershed in Southeastern New York Part 4
Valley-Reach Selection 

The nine valley reaches (fig. 1) were chosen to represent 

a wide range in the valley-bottom width and several types 

of land use. Reach length ranged from 2.15 to 3.45 mi (table 

1). Valley-bottom widths ranged from about 200 ft in the 

bedrock-floored channel in the lower reach of Mill Brook 

(MB2) to about 1,500 ft in the lower reach of the East Branch 

Delaware River (EBD2). Land uses in selected reaches 

included dairy farms, an unsewered village, low-density 

residential development in formerly farmed areas and forested 

areas, and several types and lengths of roads. Reach selection 

was also based on the following hydrologic criteria:

1. Valley-reach drainage area exceeds 20 percent of the 

total drainage area above the downstream valley-reach 

site. Reaches with as small a headwater drainage area 

(the drainage area upstream from the valley reach, as 

delineated in fig. 1) as possible relative to the valley-reach 

drainage area were essential to minimize the uncertainty 

of the calculated streamflow gain within each reach. A 

large headwater drainage area would provide a large 

upstreamflow to the valley reach, and the uncertainty 

inherent in measurement of large flows could be nearly 

equal to the gain in flow within the reach. The valley-reach 

drainage areas (between the upstream and downstream 

sites) ranged from 21 to 59 percent of the total drainage 

area above the downstream end of each reach (table 1). 

The least reliable ground-water discharge estimates came 

from reaches with the largest headwater drainage areas. 

This criterion prevented use of the widest valley reach in 

the Pepacton watershed—the East Branch Delaware River 

valley just upstream of the Pepacton Reservoir. 

2. Minimal inflow from tributaries. Minimizing the number 

of tributaries (and their drainage area) within a valley reach 

minimizes errors associated with streamflow measurements 

and thereby improves the reliability of the ground-waterdischarge estimates. 

3. Absence of lakes or wetlands within the drainage area. 

Surface-water bodies store stormwater and its associated 

water-quality characteristics and release it gradually 

downstream. Thus, a delayed stormwater contribution 

during base-flow periods would make base-flow quantity 

and quality unrepresentative of ground-water discharge. 

4. Absence of wastewater-treatment plants. Effluent 

from wastewater-treatment plants, such as the facility on 

the East Branch Delaware River at Margaretville, makes 

base flow unrepresentative of ground-water-discharge 

quality and quantity. 

Base-Flow Surveys

Surveys of streamflow and stream-water quality were 

completed during low base-flow conditions, when tributary 

flow, which represents base flow from upland areas, was 

minimal and most of the increase within the valley-stream 

reaches represented ground-water discharge from the valleyfill deposits. Base-flow conditions were assessed through 

data from USGS stream-gaging stations within the Pepacton 

watershed (fig. 2) on a reach-by-reach basis because rainfall 

amounts varied locally, and because valley-bottom width 

and permeability differed from reach to reach. The high 

evapotranspiration rates and dry tributary streambeds 

(especially in wide valleys) in summer decreased the 

magnitude of stormflows and thereby decreased the number 

Table 1. Drainage-area and runoff data on valley reaches in the Pepacton watershed in southeastern New York.

[mi2, square miles. Locations are shown in fig. 1.]

* includes valley floor plus upland hillsides and tributary watersheds that drain to main-valley stream 

† estimated runoff derived from Randall (1996) 

Table 2. Discharge increases in valley-reach streams, contributions from tributaries, and calculated ground-water discharge to valley 

reaches in Pepacton watershed in Catskill region of southeastern New York, July and August 2001. 

[All streamflow and ground-water-discharge values in cubic feet per second. Est., estimate. A dash indicates no measurement made.]

* Stream -name abbreviations:

TC Terry Clove Kill MB Mill Brook BK Batavia Kill

TK Tremper Kill PK Platte Kill EBD East Branch Delaware River

** True value may be as much as 0.3 cubic feet per second lower than this value because an upstream water release

of unknown origin had not completely passed the downstream gage at the time of flow measurement. 

Reach

identifier

(see fig. 1)

Stream

name

Drainage 

area of 

valley 

reach

(mi2 *)

Drainage area 

above 

upstream end

of reach

(mi2)

Reach area as percent 

of total drainage area 

above downstream 

end of reach

Length

of

reach

(mi)

Reach drainage 

area per mile of 

reach length

(mi2)

Average annual runoff†

Inches†

Millions of 

cubic feet 

TC Terry Clove Kill 3.78 4.86 44 2.20 1.72 25.2 221

TK Tremper Kill 8.84 24.36 26 2.85 3.10 23.0 472

PK Platte Kill 4.15 15.84 21 2.80 1.48 24.0 231

MB1 Mill Brook 7.99 9.48 45 3.00 2.66 28.1 522

MB2 Mill Brook 7.73 17.47 30 3.10 2.49 25.6 460

BK1 Batavia Kill 5.22 9.02 36 2.50 2.09 25.8 313

BK2 Batavia Kill 4.8 14.24 26 3.45 1.39 24.7 275

EBD1 East Branch 

Delaware River

8 5.5 58 2.35 3.40 26.2 487

EBD2 East Branch 

Delaware River

10.26 13.5 44 2.15 4.77 26.2 625

Reach

identifier*

in fig. 1

July 2001 Survey August 2001 Survey

Increase in 

discharge

from

upstream to 

downstream 

measurement site

Total

tributary

flow to

reach

(values in 

parentheses

are est. 

percentage

of total flow)

Calculated

ground-water 

discharge

(values in 

parentheses

are est. groundwater contribution, 

as percentage of 

streamflow

gain )

Potential

percent error in 

ground-water 

discharge

(assuming ±10% 

error in flow 

measurements

that minimize

and maximize 

ground-waterdischarge est.)

Streamflow 

gain from 

upstream to 

downstream 

measurement sites

Total

tributary

flow 

to reach

(values in 

parentheses

are est. 

percentage

of total) 

Calculated

ground-water 

discharge.

(values in 

parentheses are 

est. ground-water 

contribution 

as percentage of 

streamflow

gain)

Potential percent 

error in 

ground-water 

discharge

(assuming ±10% 

error in flow 

measurements

that minimize 

and maximize 

ground-waterdischarge est.)

TC 1.22 0.20 (100) 1.02 (84) ± 22 0.60 0.05 (100) 0.55 (92) ± 16

TK 2.15 0.78 (19) 1.37 (64) ± 90 1.23** 0.05 (0) 1.18 (96) ± 44

PK 1.25 0.24 (21) 1.01 (81) ± 79 0.61 0.13 (16) 0.48 (79) ± 74

MB1 -- -- -- -- 2.02 0.47 (9) 1.55 (77) ± 51

MB2 -- -- -- -- 1.89 0.64 (0) 1.25 (66) ± 95

BK1 0.82 0.27 (19) 0.55 (67) ± 108 0.90 0.10 (0) 0.80 (89) ± 36

BK2 1.55 0.04 (100) 1.51 (97) ± 53 0.69 0.00 (0) 0.69 (100) ± 63

EBD1 3.57 0.66 (0) 2.91 (82) ± 25 0.87 0.02 (0) 0.85 (98) ± 15

EBD2 4.44 0.00 (0) 4.44 (100) ± 33 2.38 0.00 (0) 2.38 (100) ± 19

Approach and methods 5
of days before base-flow conditions resumed 

after each storm compared to other times 

of year. Base-flow conditions were reached 

between 1 and 4 days after a storm.

The valley-reach surveys included 

streamflow measurements and water-quality 

sampling. They were conducted on July 10, 

13, 16, 17, and August 7 and 8, 2001 (fig. 2). 

July survey. A total of 14 valleyreach sites and 29 tributaries were visited. 

Streamflow was measured at all valleyreach sites and 18 tributaries; the other 

11 tributaries were dry. Water samples 

were collected at all valley-reach sites and 

at six of the tributaries. Streamflow and 

specific conductance were estimated for 

an additional 10 small tributaries that were 

not visited. No ground-water-discharge or 

chemical-quality estimates were made for 

the two Mill Brook reaches because a halfhour rain shower (recorded as 0.01 in. at the 

two meteorological stations, but estimated 

to be locally higher) caused road runoff that 

entered the stream during the survey. 

August survey. A total of 15 valleyreach sites and 34 tributaries were visited. 

Streamflow was measured at all valley-reach sites and 15 

tributaries; the other 19 tributaries were dry. Water samples 

were collected at all valley-reach sites and at nine of the 

tributaries. Streamflow and specific conductance were 

estimated for three additional small tributaries that were not 

visited. An additional valley-reach stream-water sample was 

collected within the upper valley reach of Mill Brook (MB1), 

in which surface flow was lost along a nearly 2,000-ft reach 

of streambed adjacent to large alluvial fan. The major-ion 

composition of the re-emerging flow was nearly identical to 

that at the upstream valley-reach site (UMB). 

Field Measurements

Discharge, specific conductance, pH, temperature, 

and dissolved oxygen concentration were measured at the 

upstream and downstream ends of each valley reach, and at or 

near the mouth of as many as 17 tributaries during each of the 

two survey periods. Discharge was measured with a current 

meter at main-valley streams and some large tributaries, and 

with a volumetric-measurement bag or bucket (with one or 

two replicate measurements) at small tributaries. Two teams 

of hydrologic technicians made measurements in each valley 

reach—one at the valley stream and one at the tributaries. This 

approach ensured that (1) the same individuals measured the 

same flow components, and (2) the time between upstream 

and downstream measurements was short (about 1 hour), 

to minimize the effect of fluctuations in discharge. Diurnal 

fluctuations in stream stage were not evident at any of the 

stream-gage sites. Errors in discharge measurements may 

have been as high as ±8 to 10 percent, but probable errors 

at downstream sites were smaller (± 5 to 8 percent) because 

the greater stream widths allowed 30 or more measurement 

sections across the channels.

Water Sampling and Analysis

Water samples were collected at all 15 valley-reach 

measurement sites and at six to eight tributary sites in each 

of the two surveys. Two methods were used: equal-widthincrement samples (Shelton, 1994) were collected at as many 

downstream valley-reach sites as feasible; grab samples were 

collected where the streams were too shallow and narrow for 

equal-width-increment samples. The grab-sample technique 

was used at all tributary sites and many of the upstream 

valley-reach sites. 

The water samples were analyzed for major ions, 

nutrients (dissolved nitrogen species and dissolved 

orthophosphate), dissolved organic carbon (DOC), iron, 

manganese, and selected trace elements by the USGS 

National Water Quality Laboratory in Denver, Colo. Results 

are given in Butch and others (2002). Replicate and blank 

samples collected in this study and in the concurrent baseflow study of small subbasins in the Pepacton watershed 

(Heisig and Phillips, 2004) represented 8 percent of the 

samples. Differences between major-ion replicate analyses 

were acceptable; typically 5 percent or less, except for low 

potassium concentrations (0.5 mg/L), for which replicate 

samples differed by as much as 10 percent.

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Figure 2 . Stream stage at four USGS stream-gaging stations within the Pepacton 

watershed during the July and August 2001 valley-reach surveys. (Locations are 

shown in fig. 1.)

6 Hydrogeology and Water Quality of the Pepacton Reservoir Watershed in Southeastern New York Part 4
Estimation of Tributary Streamflow and 

Water Quality 

The discharge and specific conductance values 

estimated for the one or two small, inaccessible tributaries 

in five of the valley reaches were based on values measured 

on the nearest tributaries with drainage basins of similar 

size. All estimated tributary discharges were small— 0.04 

to 0.2 ft3/s in July and 0.02 to 0.05 ft3/s in August (table 2). 

Estimated tributary discharges averaged 7 percent of the total 

streamflow gain in the July survey, and 4 percent of the gain 

in the August survey. 

Tributary water quality (major-ion concentrations) was 

estimated for all unsampled sites so that total, flow-weighted 

tributary water quality could be calculated for each valley 

reach and used in the mass-balance computations. Most small 

tributaries had low major-ion concentrations with narrow 

concentration ranges. Concentrations in unsampled tributaries 

were either (1) estimated from the regression relation of 

specific conductance to major-ion concentration for tributaries 

in drainage areas of similar land use, or (2) assigned on the 

basis of analytical results from nearby tributaries with similar 

specific conductance values (including tributaries sampled in 

the small-basin companion study (Heisig and Phillips, 2004).

Major-ion concentrations were estimated for 31 percent 

of all tributary flow for July and 10 percent of all tributary 

flow for August. The chemical composition of ground water in 

these areas is largely unaffected by road salt; hence, calcium 

and bicarbonate were typically the dominant ions (Heisig 

and Phillips, 2004). Concentrations of nutrients (nitrate and 

orthophosphate) in tributaries were not estimated because 

of their nonconservative nature and their unpredictable 

source concentrations from farmed areas. Concentrations 

of nonconservative constituents were subject to losses from 

biological uptake, chemical transformation, or sorption on 

sediments. Most tributaries for which major-ion concentrations 

were estimated drain small, largely undeveloped (forested) 

subbasins, although some contain farms, former farmland, and 

short stretches of roads.

Regression values (r2) for the relation of specific 

conductance to calcium, magnesium, acid-neutralizing 

capacity (ANC), and potassium concentration in tributaries 

ranged from 0.67 to 0.98. Values for chloride and sodium 

concentration where road salt had affected base-flow 

chemistry were within the lower part of the r2 range. Chloride 

and sodium concentrations below 1.5 mg/L did not show 

any correlation with specific conductance, nor did sulfate 

concentrations in any range. Therefore, the concentration 

Table 1. Drainage-area and runoff data on valley reaches in the Pepacton watershed in southeastern New York.

[mi2, square miles. Locations are shown in fig. 1.]

* includes valley floor plus upland hillsides and tributary watersheds that drain to main-valley stream 

† estimated runoff derived from Randall (1996) 

Table 2. Discharge increases in valley-reach streams, contributions from tributaries, and calculated ground-water discharge to valley 

reaches in Pepacton watershed in Catskill region of southeastern New York, July and August 2001. 

[All streamflow and ground-water-discharge values in cubic feet per second. Est., estimate. A dash indicates no measurement made.]

* Stream -name abbreviations:

TC Terry Clove Kill MB Mill Brook BK Batavia Kill

TK Tremper Kill PK Platte Kill EBD East Branch Delaware River

** True value may be as much as 0.3 cubic feet per second lower than this value because an upstream water release

of unknown origin had not completely passed the downstream gage at the time of flow measurement. 

Reach

identifier

(see fig. 1)

Stream

name

Drainage 

area of 

valley 

reach

(mi2 *)

Drainage area 

above 

upstream end

of reach

(mi2)

Reach area as percent 

of total drainage area 

above downstream 

end of reach

Length

of

reach

(mi)

Reach drainage 

area per mile of 

reach length

(mi2)

Average annual runoff†

Inches†

Millions of 

cubic feet 

TC Terry Clove Kill 3.78 4.86 44 2.20 1.72 25.2 221

TK Tremper Kill 8.84 24.36 26 2.85 3.10 23.0 472

PK Platte Kill 4.15 15.84 21 2.80 1.48 24.0 231

MB1 Mill Brook 7.99 9.48 45 3.00 2.66 28.1 522

MB2 Mill Brook 7.73 17.47 30 3.10 2.49 25.6 460

BK1 Batavia Kill 5.22 9.02 36 2.50 2.09 25.8 313

BK2 Batavia Kill 4.8 14.24 26 3.45 1.39 24.7 275

EBD1 East Branch 

Delaware River

8 5.5 58 2.35 3.40 26.2 487

EBD2 East Branch 

Delaware River

10.26 13.5 44 2.15 4.77 26.2 625

Reach

identifier*

in fig. 1

July 2001 Survey August 2001 Survey

Increase in 

discharge

from

upstream to 

downstream 

measurement site

Total

tributary

flow to

reach

(values in 

parentheses

are est. 

percentage

of total flow)

Calculated

ground-water 

discharge

(values in 

parentheses

are est. groundwater contribution, 

as percentage of 

streamflow

gain )

Potential

percent error in 

ground-water 

discharge

(assuming ±10% 

error in flow 

measurements

that minimize

and maximize 

ground-waterdischarge est.)

Streamflow 

gain from 

upstream to 

downstream 

measurement sites

Total

tributary

flow 

to reach

(values in 

parentheses

are est. 

percentage

of total) 

Calculated

ground-water 

discharge.

(values in 

parentheses are 

est. ground-water 

contribution 

as percentage of 

streamflow

gain)

Potential percent 

error in 

ground-water 

discharge

(assuming ±10% 

error in flow 

measurements

that minimize 

and maximize 

ground-waterdischarge est.)

TC 1.22 0.20 (100) 1.02 (84) ± 22 0.60 0.05 (100) 0.55 (92) ± 16

TK 2.15 0.78 (19) 1.37 (64) ± 90 1.23** 0.05 (0) 1.18 (96) ± 44

PK 1.25 0.24 (21) 1.01 (81) ± 79 0.61 0.13 (16) 0.48 (79) ± 74

MB1 -- -- -- -- 2.02 0.47 (9) 1.55 (77) ± 51

MB2 -- -- -- -- 1.89 0.64 (0) 1.25 (66) ± 95

BK1 0.82 0.27 (19) 0.55 (67) ± 108 0.90 0.10 (0) 0.80 (89) ± 36

BK2 1.55 0.04 (100) 1.51 (97) ± 53 0.69 0.00 (0) 0.69 (100) ± 63

EBD1 3.57 0.66 (0) 2.91 (82) ± 25 0.87 0.02 (0) 0.85 (98) ± 15

EBD2 4.44 0.00 (0) 4.44 (100) ± 33 2.38 0.00 (0) 2.38 (100) ± 19

Approach and methods 7
estimates for these constituents represent either individual or 

the average concentrations in nearby tributaries.

 The streamflow and chemical data for all tributaries 

were compiled, and all tributary flows within each valley 

reach were summed (total tributary inflow), their composite 

chemical concentrations were calculated as flow-weighted 

means (See appendix). Charge balances (the percent 

difference between the total negative charge of anions and 

the total positive charge of cations) were used as a check 

of the reasonableness of the major-ion-chemistry results. 

Charge balances for all valley reaches were acceptable 

(within ± 5 percent).

Mass-Balance Calculation of 

Ground-Water Quality

Major-ion concentrations of ground water in each valley 

reach were calculated from the July and August streamflow 

measurements and chemical data through the following massbalance equation: 

 Qgw Cgw = QdnCdn - QupCup - QtribCtrib (Equation 1)

Where: 

Qgw = ground-water discharge to the valley stream

Cgw = concentration of constituent in ground water

Qdn = streamflow at downstream valley-stream site

Cdn = concentration of constituent at downstream 

valley-stream site

Qup = streamflow at upstream valley-stream site

Cup = concentration of constituent at upstream 

valley-stream site

Qtrib = sum of tributary flows within a valley reach 

(tributary inflow) 

Ctrib = flow-weighted mean concentration of constituent 

among tributaries 

A major-ion concentration in ground water Cgw equals:

 Cgw = Qdn Cdn - Qup Cup - QtribCtrib

 Qgw

Individual major-ion results within each reach 

were combined and expressed as a major-ion water type 

(Appendix), defined by the ions that constituted at least 10 

percent of the total cations (calcium, magnesium, sodium, and 

potassium) or the total anions (bicarbonate, chloride, sulfate, 

and nitrate), in milliequivalents per liter. 

Potential Errors in Estimates of Ground-Water 

Discharge and Water Type 

Errors in estimates of ground-water discharge and, 

ultimately, major-ion water type, were largely related to (1) 

uncertainties in the upstream and downstream streamflow 

measurements, and (2) the difference between the upstream 

and downstream streamflow measurements relative to the 

magnitude of the flows. For instance, a potential uncertainty of 

±10 percent in streamflow measurement in valley streams with 

large flows would require a proportionately large difference 

between upstream and downstream streamflow measurements 

to overcome the effect of this uncertainty.

The actual errors in the streamflow measurements are 

unknown; therefore, a worst-case potential error (in percent) 

was calculated for each ground-water-discharge estimate. 

Ground-water discharges were recalculated from combinations 

of ± 10-percent adjustments in streamflow that maximized 

and minimized the ground-water estimates. Ground-waterdischarge estimates were maximized when the upstream and 

tributary inflow values were adjusted to 10 percent smaller 

than the measured values, and the downstream streamflow was 

adjusted to 10 percent greater than its measured value. The 

ground-water-discharge estimates were minimized when these 

negative and positive adjustments were reversed. Thus, the 

maximum and minimum ground-water discharges represent 

the same percent departure from the initial estimate and 

differ only in sign. Potential errors ranged from ± 15 to ±108 

percent and were generally smaller in August than in July 

because the smaller upstream and tributary flows in August 

generally resulted in an increase in the percentage of base flow 

contributed by ground-water discharge (table 2).

The potential-error results allow a comparison of the 

uncertainty of the ground-water discharge estimates among 

valley reaches within and between the two surveys. Small 

differences between upstream and downstream streamflow, 

and large flow magnitudes, contribute to high potential errors 

(table 2). The actual ranges of percent error are probably 

smaller than indicated, however, because these estimated 

uncertainty values used extreme-opposite biases among the 

streamflow measurements. Opposite biases are unlikely 

because (1) valley-stream measurements are probably biased 

in the same direction if the channel geometries within a given 

reach are similar; (2) the downstream-measurement errors 

are probably smaller than ± 10 percent because the channels 

at the downstream sites are larger than at the upstream sites 

and, thus, provide better measurement conditions; and (3) 

volumetric measurements of tributary flows are more likely to 

underestimate streamflow than to overestimate it; therefore, a 

negative bias is most likely. 

The effects of errors in ground-water-discharge estimates 

on water-type determinations were evaluated through data 

collected in August 2001 from four valley reaches (BK1, 

BK2, MB2, EBD2), which represent the range of land uses 

in valley-bottom areas within the watershed. Potential errors 

in ground-water discharges at these reaches ranged from ±19 

to ±95 percent. Ground-water types were calculated from the 

maximum and minimum ground-water discharges, based on 

±10-percent errors in streamflow measurements. If no change 

in water type occurred over this error range, the estimates 

were considered insensitive to the range of streamflowmeasurement errors, and no further analysis was done. If a 

change in water type was indicated, the sensitivities of watertype results to streamflow errors smaller than ±10 percent (±5, 

±3 percent) were evaluated.

8 Hydrogeology and Water Quality of the Pepacton Reservoir Watershed in Southeastern New York Part 4
Results of this sensitivity evaluation indicated that 

water type changed little, if at all, within any reach except 

the one (MB2) with the highest potential error (±95 percent). 

All changes in water type coincided only with positive (+) 

changes in ground-water discharge. The water types shifted 

from (1) unaffected water to water containing chloride (or 

sodium), or (2) water containing chloride as a secondary anion 

to water with chloride as the dominant anion. No change in 

water type was indicated for the valley reaches with potential 

ground-water-discharge errors of ±19 percent (EBD2) and 63 

percent (BK2). The water type for the valley reach with a ±36-

percent potential error (BK1) changed to a chloride-dominated 

type only at the +10-percent streamflow-measurement error. 

Water type at the valley reach with a ±95-percent potential 

error (MB2) changed to a chloride or sodium-affected water in 

response to +10, +5, and +3 percent increases in streamflow 

measurement error. In summary, water type remained stable 

over relatively large changes in ground-water-discharge 

estimates, except where those changes approached 100 percent 

of the original discharge value.

Ground-Water and Tributary 

Contributions to Stream Base Flow in 

Selected Main-Valley Reaches

The quantity and quality of ground-water and tributary 

contributions to valley-stream base flow provide basic 

hydrologic information on 1) the proportions of tributary flow 

from upland areas and ground-water discharge from valleybottom areas and 2) the interaction between the shallow, 

most active part of the ground-water flow system (affected by 

human activities) and surface water in valley-bottom settings. 

Water-quality and land-use data indicate a connection between 

land-use practices and the quality of shallow ground water and 

base flow in the main-valley streams studied.

Quantity of Water

Analysis of the streamflow measurements from the 

valley-reach surveys revealed three patterns in the total and 

individual quantities of ground-water discharge and tributary 

inflow to main-valley streams: (1) the streamflow gain in a 

given valley reach was chiefly a function of the volume of 

annual runoff (precipitation minus evapotranspiration) in the 

valley-reach drainage area, (2) ground-water discharges were 

consistently greater than tributary flows in all valley reaches in 

both surveys, and (3) tributary inflows were strongly affected 

by upland drainage area size, main-valley width, permeability 

of valley-fill deposits, and local annual runoff. These 

observations are described in the following paragraphs. 

Relation Between Streamflow Gain and 

Annual Runoff Volume

A general positive relation was found between 

streamflow gain within the valley reaches and annual 

runoff volume, regardless of the proportions of groundwater discharge and tributary inflow (fig. 3). Annual 

runoff represents the annual amount of water available for 

streamflow (stormflow plus base flow). Local differences in 

precipitation and evapotranspiration cause runoff differences 

of as much as 5 in. among the drainage areas of the nine valley 

reaches (Randall, 1996). The total volume of runoff from each 

valley reach, expressed in millions of cubic feet per year (table 

1), is the average annual runoff volume, in inches, multiplied 

by the drainage area of the valley reach. This includes the 

valley floor, the adjacent unchanneled uplands, and the 

drainage areas of upland tributaries. 

A study in central New England (Wandle and Randall, 

1994) reported that low-flow discharge (base flow) in streams 

was largely a function of the amount of water available to the 

upstream drainage area and the amount of permeable stratified 

drift at land surface relative to the amount of less-permeable 

unconsolidated material within the drainage area. The extent 

of stratified drift relative to the size of valley-reach drainage 

areas in the Pepacton watershed does not vary greatly; this 

may explain why annual runoff volume, not amount of 

stratified drift, appears to be the major control on streamflow 

gain along the valley reaches. 

Negative departures from the trend line for streamflow 

gain as a function of annual runoff volume for the July 

and August surveys (fig. 3) are probably due to one or 

more of the following factors: (1) large potential errors in 

ground-water-discharge estimates, (2) low rainfall within 

the Tremper Kill subbasin, and (3) complete loss of flow 

in large tributaries during the 3 to 4 weeks between the two 

surveys. The relatively small July streamflow gains at the 

Tremper Kill (TK) and upper Batavia Kill (BK1) valley 

reaches are consistent with the large potential errors in the 

ground-water-discharge estimates for these reaches (table 2, 

fig. 3). Specifically, BK1 is the only valley reach in which 

the streamflow gain in July was less than the streamflow 

gain in August—an anomaly that might be ascribed to overmeasurement of discharge at the upstream (BK1) site. The 

downstream-site measurement appears reasonable because it 

serves as the upstream site for valley reach BK2, which plots 

on the trend line in figure 3.

The relatively small streamflow gains within the Tremper 

Kill (TK) valley reach in July, and particularly in August, 

may also reflect smaller rainfall amounts in this subbasin than 

in the others. Localized thunderstorms are common during 

the summer, and monthly rainfall totals for July and August 

at the two weather stations (fig. 1) differed by more than 1 

in. (Cornell University Northeast Regional Climate Center, 

Ground-Water and Tributary Contributions to Stream Base Flow in Selected Main-Valley Reaches 9
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Figure 3. Total streamflow gain within the nine valley reaches as a function of annual runoff volume from their 

respective valley-reach drainage areas (not including headwater drainage area upvalley from valley reach), 

Pepacton watershed, southeastern N.Y., July and August 2001. (Locations are shown in fig. 1.)

10 Hydrogeology and Water Quality of the Pepacton Reservoir Watershed in Southeastern New York Part 4
written commun., 2002). Precipitation was not recorded within 

the Tremper Kill subbasin, but streamflow data were available 

from USGS stream-gaging stations (figs. 1, 2) on the Tremper 

Kill, Platte Kill, Mill Brook, and East Branch Delaware 

River at Margaretville (Butch and others, 2002). The July 

and August 2001 monthly means of daily mean discharges at 

these sites were compared with the corresponding monthly 

means for the period of record at each of these stream-gaging 

stations; the results indicate that Tremper Kill means were 6 

to 14 percent lower than the means for the other subbasins in 

July, and 8 to 17 percent lower in August; this supports the 

other evidence that rainfall in the Tremper Kill subbasin was 

less than in the surrounding subbasins during this study. 

The reach with the largest negative departure from 

the August trend line for streamflow gain as a function of 

annual runoff (fig. 3) was the upper East Branch Delaware 

River valley reach (EBD1), which had plotted close to the 

trend line in July. The decrease in streamflow gain between 

the two surveys coincided with the loss of all flow from the 

largest tributary to the reach and the loss of much of the flow 

from another large tributary. This observation suggests that 

as tributary flows ceased to reach the valley stream and the 

point of zero flow migrated upstream toward the main-valley 

wall, so did the ground-water mound that exists beneath the 

flowing tributary (Randall, 1978). Ground-water mounds are 

maintained by the infiltration of stream water to the water 

table. The dissipation of the mound under dry sections of 

streambeds thereby decreased ground-water discharge in 

addition to the loss of tributary discharge to the valley stream.

Ground-Water Discharge in Relation to 

Tributary Inflow

Ground-water discharge from valley deposits exceeded 

the inflow from tributaries in all valley reaches (fig. 4) and 

decreased from July to August in all but one valley reach 

(BK1). Tributary inflow decreased more than ground-water 

discharge, causing the ground-water-discharge contribution to 

increase as a percentage of streamflow gain in a valley reach 

(table 2). The decrease in tributary inflow reflects the seasonal 

decreases in: (1) flow from upland sources and (2) the 

amount of tributary flow lost through streambed infiltration 

(Randall, 1978). Infiltration losses are typically greatest where 

a tributary crosses permeable material within a wide main 

valley before joining the valley stream. Tributary flow that 

infiltrates permeable deposits near the valley stream can move 

rapidly toward the valley stream as ground water; thus, a loss 

of tributary flow through infiltration near the valley stream 

would result in an increase in ground-water discharge to the 

valley stream. 

Differences in Tributary Inflow Among 

Valley Reaches

Differences in tributary-inflow contributions (base 

flow from upland areas) to the valley streams correspond to 

differences in width and permeability of valley-fill deposits, 

size of drainage area, and annual runoff volume. Tributaries 

entering wide valleys with permeable valley fill (outwash, 

ice-contact, or alluvial deposits) are likely to lose more water 

through streambed infiltration than those entering narrow 

valleys or valleys that contain only poorly permeable valley 

fill (thin alluvium over till). Similarly, valley reaches with 

large upland drainage areas and (or) large annual runoff 

volumes will have greater tributary inflow than valley reaches 

with small upland drainage areas and low annual runoff 

volumes. For example, no tributary flow reached the stream 

in reach EBD2 in July or in August 2001 (fig. 4). One large 

tributary lost all flow to streambed infiltration before reaching 

the valley stream because it has an exceptionally long (nearly 

0.5 mi) channel that traverses permeable valley-fill material 

within the main valley. Large tributaries to valley reaches 

TK and EBD1 contributed most of the tributary inflow to 

the valley streams in July, but these contributions decreased 

in August more than in the other valley reaches when their 

flow decreased to, or below, the infiltration capacity of the 

streambeds. The four valley reaches with narrow valley 

bottoms and relatively small upland drainage areas (BK2, 

BK1, TC, PK) had relatively small tributary inflows in 

July and August, but two other reaches with narrow valley 

bottoms (MB1, MB2) had the largest tributary inflows of 

the August survey. Reaches MB1 and MB2 have somewhat 

larger drainage areas, greater annual runoff volumes, and more 

tributaries than the four aforementioned valley reaches (fig. 

1, table 1). Unmeasured tributary flows to MB1 and MB2 

were probably greater in July than in August because tributary 

inflows in nearly all other valley reaches were greatest in July.

Quality of Water

The chemical quality of ground-water discharge and 

tributary inflows that entered valley streams during the July 

and August surveys was measured or calculated for all reaches 

except the two Mill Brook reaches (MB1, MB2) in July and 

the Tremper Kill (TK) reach in August. The Mill Brook 

reaches were temporarily affected by runoff from a local 

storm, and the Tremper Kill was temporarily affected by an 

unexplained 6-hour spike in discharge (fig. 2). Water-quality 

estimates were largely limited to major ions, which are more 

conservative (less reactive) than nutrients (such as nitrate and 

orthophosphate). Most major ions are derived largely from 

Ground-Water and Tributary Contributions to Stream Base Flow in Selected Main-Valley Reaches 11
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Figure 4. Ground-water-discharge and tributary-inflow contributions to total streamflow gain in the nine valley reaches, 

Pepacton watershed in southeastern New York, July and August 2001. (Locations are shown in fig. 1.)

12 Hydrogeology and Water Quality of the Pepacton Reservoir Watershed in Southeastern New York Part 4
natural sources, but sodium and chloride are derived mainly 

from road salt applied to State and county roads during winter. 

Nitrate and orthophosphate are a concern because they 

can contribute to downstream reservoir eutrophication. 

Ground-water contributions of nitrate were calculated for 

only four valley reaches, however, and no calculations for 

orthophosphate were made because 1) their nonconservative 

nature (loss or retention due to biological activity and (or) 

sorption on sediments) in hyporheic zones and in streams, and 

2) their unpredictable concentrations in tributaries, especially 

in farmed areas, introduce unacceptable uncertainties into 

budget calculations. The principal sources of these nutrients 

in ground water are human waste from septic systems, 

particularly in villages, and animal wastes, such as cow 

manure applied to cultivated fields and pastures. 

General Water-Type Classification

The water components (tributary inflow, ground-water 

discharge, and flow in valley streams) in each valley reach 

were classified as one of six chemical water types according to 

their major-ion concentrations (fig. 5 and appendix). Watertype designation reflects the specific ions that constituted at 

least 10 percent (in milliequivalents per liter) of the cations 

and anions (herein referred to as “defining ions”). The cations 

can include calcium (Ca), sodium (Na), magnesium (Mg), 

and potassium (K), and the anions can include bicarbonate 

(HCO3), chloride (Cl), sulfate (SO4), and nitrate (NO3). For 

example, sodium and chloride represent at least 10 percent of 

the cations and anions, respectively, in the two water types 

that are most affected by leachate from road-deicing salts, 

and represent less than 10 percent of the cations and anions, 

respectively, in the other four water types, which are largely 

unaffected by road-salt leachate. 

The four water types for which sodium and chloride 

are not defining ions all have Ca and HCO3 as defining 

ions; the presence or absence of Mg and SO4 as defining 

ions determines the specific water type (fig. 5). Magnesium 

concentration varies locally within streams in the Pepacton 

watershed and is probably associated with the till composition 

(carbonate minerals) and thickness within the watershed 

and, in some agricultural areas, with the amount of lime 

(crushed limestone) that is applied to fields. Base-flow 

SO4 concentrations in most small tributaries and in Mill 

Brook were generally low; SO4 was a defining ion only in 

dilute waters with low HCO3 concentrations. The specific 

conductance of these dilute waters (unaffected by road 

salt) was less than 70 �μS/cm in all samples. Dilute waters 

represent either a short ground-water residence time, or 

a longer residence time in relatively unreactive aquifer 

material. Bicarbonate (HCO3) concentration in ground water 

typically increases (evolves) with increasing residence time 

or increased reactivity (carbonate mineral content) of the 

surrounding aquifer material until it eventually becomes the 

only defining anion. 

Waters Affected By Road Salt and Nutrients

 The principal source of sodium and chloride to shallow 

ground water is road salt that is applied most heavily along 

major roads in winter, which subsequently infiltrates to the 

water table over time. The principal sources of nutrients in 

ground water are cow manure that is applied to cultivated 

fields, and human waste that is discharged from septic 

systems, particularly in villages.

Chloride and Sodium Sources and Concentrations

Chloride and (or) sodium become defining ions only in 

waters affected by road salt. Chloride may be more abundant 

than bicarbonate in some instances. Ground waters affected 

by road salt began as one of the four naturally occurring 

water types (largely unaffected by road salt), but became 

chemically altered by salt leachate as they flowed beneath 

roadway areas (fig. 6). The amount of chloride and sodium in 

ground water that discharges to streams is related to the type 

of roads and the road mileage within the drainage area (Heisig, 

2000; Heisig and Phillips, 2004). Annual salt-application 

rates are highest on State roads (40 tons per mile of twolane road) and county roads (32 tons per mile of two-lane 

road), and are lowest on town roads (1 to 12 tons per mile 

of two-lane road) (Heisig and Phillips, 2004). Many of the 

State and county roads in the Pepacton watershed parallel the 

major streams. The type of roads that follow the main-valley 

streams within each valley reach, and those in the upgradient 

drainage area of each valley reach, are indicated in figure 5; 

these roads represent nonpoint sources of salt leachate and 

affect only shallow ground water in the area between the road 

and the stream (fig. 6). The elevated sodium and chloride 

concentrations between roads and streams are commonly 

sufficient to shift the mean chemical quality of the overall 

ground-water discharge from a naturally occurring type to one 

with chloride and sodium as defining ions (fig. 5). 

The estimated chloride concentrations in ground-water 

discharge from valley-stream reaches that contain a State 

or county road averaged from 8 to 13 mg/L—about 5 times 

higher than naturally occurring levels (fig. 5) – but these 

concentrations do not pose health or regulatory concerns 

because they do not approach the New York State drinkingwater maximum contaminant level (MCL) for chloride (250 

mg/L). No MCL has been established for sodium, but health 

guidelines suggest less than 20 mg/L for severely restricted 

sodium diets and less than 270 mg/L for moderately restricted 

sodium diets (New York State Department of Health, 2001). 

The chloride concentrations of ground-water discharge 

calculated in this study represent the mean of three groundwater components (fig. 6): (1) shallow, high-chloride ground 

water entering from a small area on one side of a valley, (2) 

deeper, low-chloride ground water entering on that side of the 

valley, and (3) shallow and deep low-chloride ground water 

entering from the other side of the valley (fig. 6). The chloride 

and sodium concentrations of salt-affected shallow ground 

Ground-Water and Tributary Contributions to Stream Base Flow in Selected Main-Valley Reaches 13
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Figure 5. Relative discharge magnitude, water type, concentration of chloride, nitrate, and orthophosphate in 

streamflow and ground-water discharge, and land uses that might affect ground-water quality in each reach studied 

in Pepacton watershed, southeastern N.Y., July and August 2001. (Site locations are shown in fig. 1.).

14 Hydrogeology and Water Quality of the Pepacton Reservoir Watershed in Southeastern New York Part 4
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Figure 5. (Continued) Relative discharge magnitude, water type, concentration of chloride, nitrate, and orthophosphate in 

streamflow and ground-water discharge, and land uses that might affect ground-water quality in each reach studied in 

Pepacton watershed, southeastern N.Y., July and August 2001. (Site locations are shown in fig. 1.).

Ground-Water and Tributary Contributions to Stream Base Flow in Selected Main-Valley Reaches 15
Figure 6. Generalized valley reach (upland tributary drainage area is omitted) showing migration of road-salt 

leachate to shallow ground water and the adjacent valley stream. 

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16 Hydrogeology and Water Quality of the Pepacton Reservoir Watershed in Southeastern New York Part 4
water in some localities may be as high as a few hundred mg/L 

(Massachusetts—Granato and others, 1995; Ohio—Jones and 

Sroka, 1997). Other effects of road salt can include corrosion 

of metal on bridges, damage to vegetation, decreased 

biodiversity along roads and nearby streams, decreased soil 

permeability, and toxicity to fish and birds (Environment 

Canada and Health Canada, 2000).

Ground-water discharge in all valley reaches that contain 

State or county roads was estimated to have elevated chloride 

concentrations (8-13 mg/L) except the Tremper Kill (TK) 

reach (fig. 5), which contains a county road; ground-water 

discharge to this reach during the July survey had an estimated 

chloride concentration of only about 2 mg/L. This anomaly 

has two possible explanations:

1. The county road largely follows the lower hillsides, well 

above the valley bottom, and the stream generally flows 

along the opposite side of the valley. Limited storm 

runoff from this road likely infiltrates to the water table 

because storm drains and ditches probably divert most 

runoff directly to tributaries or the stream, where it flows 

downstream as part of stormflow before the resumption of 

base-flow conditions. Also, salt leachate that infiltrates to 

the water table at some distance from the stream probably 

becomes entrained in deeper flow paths, with longer 

residence times, than leachate that becomes ground water 

in areas close to the stream and, thus, may not yet have 

reached the valley stream.

2. The large potential error in the quantity of ground water 

discharging to the Tremper Kill (table 2, fig. 4) indicates 

a large uncertainty in concentration estimates; therefore, 2 

mg/L could be an under estimate of the actual value.

The water types indicated for nearly all valley-reach, 

tributary inflow, and ground-water discharge waters in each 

reach did not change from July to August, and none shifted 

to or from road-salt-affected types (fig. 5). All valley reaches 

except the Terry Clove Kill and the two Mill Brook reaches, 

which contain only town roads, had at least one streamflow 

component affected by road salt. The tributary contributions 

to streamflow gain in all reaches were classified as naturally 

occurring water types, largely unaffected by road salt, which 

is consistent with the absence of State and county roads in the 

tributary drainage areas.

Nitrate and Orthophosphate Sources and Concentrations

Streamflow in many of the valley reaches showed 

either little increase, or even a decrease, in nitrate (NO3) and 

orthophosphate (PO4) concentrations from the upstream site 

to the downstream site; therefore, the nitrate concentration 

in ground-water discharge could be estimated only for valley 

reaches with little or no tributary inflow and a relatively 

large downstream increase in nitrate concentration. Only four 

estimates of nitrate concentration (mg/L as N) in ground-water 

discharge were made, and no estimate of orthophosphate 

concentration was made.

Large nitrate increases within a valley reach indicate a 

nitrogen source within that reach, but two factors— dilution 

by tributary inflow and the potential for biological uptake 

or transformation of nitrate, indicate that the concentrations 

obtained through the mass-balance calculation for ground 

water entering a reach represents a lower limit of the true 

average nitrate concentration. The reaches for which nitrate 

concentrations in ground-water discharge were calculated 

were the two East Branch Delaware River reaches (EBD1, 

EBD2) and the Terry Clove Kill reach (TC ) during the July 

survey, and EBD2 during the August survey. All of these 

reaches contain nutrient sources within their valley-bottom 

areas; the EBD2 reach contains a village served by septic 

systems, and the others contain cultivated fields or dairy 

farms (fig. 5). The estimated concentrations of nitrate in 

ground water entering these reaches ranged from 0.23 to 0.62 

mg/L as N. The value for each reach represented an average 

for the entire reach; the concentrations in shallow ground 

water immediately downgradient from the sources would 

presumably have been higher than the average for the reach.

Nutrient concentrations (NO3, PO4) in most of the mainvalley reaches were low (fig. 5). The highest concentrations 

of both nutrients were consistently found within the Terry 

Clove Kill and the two East Branch Delaware River valley 

reaches. The elevated concentrations are generally attributable 

to dairy farming and septic-waste disposal within the 

upstream drainage areas, but an evaluation of the intensity of 

these practices was beyond the scope of this study; such an 

evaluation would require data on livestock and septic-system 

density and locations of sources relative to the valley stream, 

and the drainage area associated with each valley reach. 

Nevertheless, the results of this study indicate that livestock 

and human waste contribute nutrients to ground water that 

discharges to main-valley streams in the Pepacton watershed.

Summary

Streamflow measurements and water-quality data were 

collected at nine main-valley reaches and their tributaries in the 

Pepacton Reservoir watershed in the Catskill Mountains during 

base-flow periods in July and August of 2001. The data were 

used in mass-balance equations to estimate the quantity and 

major-ion concentrations of ground water entering main-valley 

streams from adjacent valley-fill deposits. This information 

provides a general indication of the major-ion concentrations 

of shallow ground water that discharges to streams in six main 

valleys within the Pepacton watershed. Estimation of nutrient 

concentrations (nitrate and orthophosphate) in ground water by 

this method was limited or precluded by the nonconservative 

behavior of these constituents. 

Total gains in streamflow between the upstream and 

downstream valley-reach sites were closely related to the 

volume of annual runoff from the respective valley-reach 

Summary 17
drainage areas, regardless of the proportion of ground-water 

discharge to tributary inflow within a reach. Ground-water 

discharge exceeded tributary inflow in all valley reaches. The 

proportions of ground-water discharge and tributary inflow 

in the valley reaches reflected the width and permeability of 

valley-fill deposits. Stream reaches in narrow valleys without 

extensive valley fill tended to receive the largest proportions 

of tributary inflow and the smallest proportions of groundwater discharge, whereas tributary inflow to wide valleys with 

extensive valley fill was the smallest proportion of stream 

gain because of losses through streambed infiltration. Groundwater discharge was the largest proportion of streamflow gain 

in reaches of wide valleys. 

The major-ion composition of water from valleystream sites, tributary inflow, and ground-water discharge in 

each reach was evaluated. All waters ranged from naturally 

occurring waters with little or no indication of human effect, 

to water types affected by road salt. Naturally occurring water 

types were typically a calcium-bicarbonate type. Nearly all 

ground-water-quality estimates and base-flow samples from 

main-valley reaches that contain State or county highways 

indicated road-salt-affected water types. Mean concentrations 

of chloride in ground-water discharge (8-13mg/L) were 

typically about 5 times higher than the naturally occurring 

concentrations (less than 2 mg/L). Application of salt to a road 

in a valley bottom affects only the shallow ground water in the 

area between the road and the stream, but the concentrations 

in the water entering the stream can be sufficiently large to 

elevate the mean chloride concentration of ground-water 

discharge in the reach. 

Estimation of nitrate and orthophosphate concentrations 

in ground-water discharge was not possible because these 

nutrients are nonconservative and their concentrations in 

unsampled tributaries that pass through dairy-farm areas 

could not be reliably estimated. However, stream-water 

samples collected downstream from manure sources or 

villages served by septic systems consistently had the highest 

nutrient concentrations.

References Cited

Butch, G.K., Murray, P.M., Robideau, J.A., Gardner II, J.A., 

2002, Water resources data, New York, water year 2001, v. 

1, Eastern New York: U.S. Geological Survey Water-Data 

Report NY-01-1, p. 549-568.

Coates, D.R., 1966, Glaciated Appalachian Plateau—till 

shadows on the hills: Science, v. 152, p. 1617-1619.

Environment Canada and Health Canada, 2000, Draft report 

- Canadian Environmental Protection Act, 1999; priority 

substances list assessment report - road salts: Environment 

Canada and Health Canada, 173 p. 

Fisher, D.W., Isachsen, Y.W., and Rickard, L.V., 1970, 

Geological map of New York: Hudson-Mohawk Sheet,

New York State Museum and Science Service, Map and Chart 

Series no. 15, 1:250,000.

Granato, G.E., Church, P.E., and Stone, V.J., 1995, 

Mobilization of major and trace constituents of highway 

runoff in groundwater potentially caused by deicing 

chemical migration: Transportation Research Record 1483, 

p. 92-104.

Heisig, P.M., 2000, Effects of residential and agricultural land 

uses on the chemical quality of baseflow of small streams 

in the Croton watershed, southeastern New York: U.S. 

Geological Survey Water-Resources Investigations Report 

99-4173, 15 p.

Heisig, P.M. and Phillips, P.J., 2004, Hydrogeology and water 

quality of the Pepacton Reservoir watershed in southeastern 

New York—Part 3. Responses of stream base-flow 

chemistry to hydrogeologic factors and nonpoint sources 

of contamination: U.S. Geological Survey ScientificInvestigations Report 2004-5008, 31 p. 

Jones, A.L., and Sroka, B.N., 1997, Effects of highway 

deicing chemicals on shallow unconsolidated aquifers in 

Ohio, interim report, 1988-93: U.S. Geological Survey 

water-Resources Investigations Report 97-4027, 139 p.

New York State Department of Health, 2001, Public Health 

Law, Section 225, Part 5, Subpart 5-1 (Public Water 

Systems): Albany, New York State Department of Health, 

67 p.

Phillips, P.J. and Heisig, P.M., 2004, Hydrogeology and water 

quality of the Pepacton Reservoir watershed in southeastern 

New York—Part 1. Concentrations of pesticides and their 

degradates in stream baseflow, 2000-2001: U.S. Geological 

Survey Water-Resources Investigations Report 03-4137, 

14 p. 

Randall, A.D., 1978, Infiltration from tributary streams in 

the Susquehanna River basin, New York: U.S. Geological 

Survey, Journal of Research, v. 6, no. 3, p. 285-297.

Randall, A.D., 1996, Mean annual runoff, precipitation, and 

evapotranspiration in the glaciated northeastern United 

States, 1951-80: U.S. Geological Survey Open-File Report 

96-395, 2 sheets, scale 1: 1,000,000. 

Reynolds, R.J., 2004, Hydrogeology and water quality of the 

Pepacton Reservoir watershed in southeastern New York—

Part 2. Hydrogeology, stream base flow, and estimates of 

recharge: U.S. Geological Survey Scientific Investigations 

Report 2004-5134, 31 p.

Shelton, L. R., 1994, Field guide for collecting and processing 

stream-water samples for the National Water-Quality 

Assessment Program: U.S. Geological Survey Open-File 

Report 94-455, 42 p. 

Wandle, S.W., and Randall, A. D., 1994, Effects of surficial 

geology, lakes and wetlands, and annual water availability 

on low flows of streams in central New England, and their 

use in low-flow estimation: U.S. Geological Survey WaterResources Investigations Report 93-4092, 57 p. 

18 Hydrogeology and Water Quality of the Pepacton Reservoir Watershed in Southeastern New York Part 4
Appendix

Appendix 19
Appendix A . Valley-stream discharge at sampling sites and tributary discharge and ground-water flow into reach, with major-ion water type 

concentration of each during baseflow-sampling surveys in Pepacton Reservoir watershed in southeastern New York, July and August 2001.

[Concentrations in milligrams per liter except as specified. μS/cm, microsiemens per centimeter at 25 ̊ Celsius. � greater than or equal to, < less than. 

Dash indicates no data or no estimated value. Analyses by U.S. Geological Survey, Denver, Colo. Locations are shown in fig. 1.].

Valley 

stream

Site or flowcomponent

identifier*

USGS

station

identifier

Discharge

 or flow

 (ft3/s) Major-ion water type

Specific

conductance

 (mS/cm)

Sodium

(Na)

Potassium

 (K)

Magnesium

(Mg)

Calcium

(Ca)

Chloride 

(Cl)

Sulfate

(SO4)

B

carb

(HC

July 2001 SurveyBatavia Kill UBK 0141309740 2.42 Ca-HCO3 55 2.1 0.41 1.2 6.6 1.7 4.5 2

BK1 trib 0.27 Ca-HCO3 94 3.5 0.48 1.9 12.0 4.0 4.6 4

BK1 gw 0.55 Ca-Na-Cl-HCO3 101 6.7 1.02 1.4 7.8 11.8 7.4 1

MBK 01413098 3.24 Ca-Na-HCO3 66 3.0 0.52 1.3 7.3 3.6 5.0 2

BK2 trib 0.04 Ca-HCO3-SO4 50 2.0 0.45 0.9 6.0 2.0 5.3 1

BK2 gw 1.51 Ca-Na-HCO3-Cl 98 5.3 0.36 1.7 9.8 8.1 5.6 4

LBK 01413099 4.79 Ca-Na-HCO3 76 3.7 0.47 1.4 8.1 5.0 5.2 2

East Branch UEBD 01413070 1.50 Ca-Na-HCO3-Cl 106 7.9 0.45 1.5 10.2 8.9 3.7 3

Delaware EBD1 trib 0.66 Ca-HCO3-SO4 49 1.9 0.45 0.9 6.0 1.7 5.3 1

EBD1 gw 2.91 Ca-Na-HCO3-Cl 112 9.3 0.68 1.6 10.4 10.3 5.6 3

MEBD 01413088 5.07 Ca-Na-HCO3-Cl 102 7.9 0.58 1.5 9.8 8.8 5.0 3

EBD2 trib 0.00 -- -- -- -- -- -- -- -- -

EBD2 gw 4.44 Ca-Na-HCO3-Cl 126 7.7 0.8 1.9 12.0 11.0 6.7 3

LEBD 01413092 9.51 Ca-Na-HCO3-Cl 113 7.8 0.68 1.7 10.8 9.8 5.8 3

Mill Brook UMB 01414308 4.93 (rain) Ca-HCO3-SO4 52 1.2 0.38 1.0 6.8 1.9 5.5 2

MB1 trib (rain) -- -- -- -- -- -- -- -- -

MB1 gw (rain) -- -- -- -- -- -- -- -- -

MMB 01414340 8.34 (rain) Ca-HCO3-SO4 48 1.2 0.38 1.1 6.0 1.9 5.3 1

MB2 trib (rain) -- -- -- -- -- -- -- -- -

MB2 gw (rain) -- -- -- -- -- -- -- -- -

LMB 01414500 9.52 Ca-Mg-HCO3-SO4 52 1.5 0.42 1.3 6.3 2.0 5.5 2

Platte Kill UPK 10413936 3.23 Ca-Mg-HCO3 72 3.0 0.65 1.8 7.7 3.6 4.9 2

PK trib 0.24 Ca-Mg-HCO3 72 2.5 0.31 1.7 7.5 3.2 4.9 3

PK gw 1.01 Ca-Na-HCO3-Cl 130 7.0 0.8 2.3 10.2 10.5 6.1 3

LPK 01413945 4.48 Ca-Na-Mg-HCO3 85 4.1 0.71 2.0 8.9 5.5 5.5 3

Tremper Kill UTK 01414865 4.71 Ca-Na-HCO3-Cl 125 8.7 1.03 2.5 9.2 15.7 5.8 3

TK trib 0.78 Ca-Mg-HCO3-SO4 55 1.7 0.34 1.8 5.7 1.5 5.6 2

TK gw 1.37 Ca-Mg-HCO3-SO4 60 1.7 0.57 1.9 6.0 2.2 6.4 1

LTK 0141500 6.86 Ca-Na-Mg-HCO3-Cl 104 6.5 0.86 2.3 8.2 11.4 5.9 2

Terry Clove Kill UTC 01415438 0.41 Ca-Mg-HCO3 67 1.6 1.1 2.1 7.2 1.0 5.3 3

TC trib 0.20 Ca-Mg-HCO3-SO4 55 1.8 0.75 1.7 6.0 1.6 5.3 2

TC gw 1.02 Ca-Mg-HCO3 79 2.2 1.56 2.5 8.2 1.8 7.0 3

 LTC 01415465 1.63 Ca-Mg-HCO3 74 2.0 1.37 2.3 7.7 1.6 6.4 3

* Prefix U, upper site; M, middle site; L, lower site. trib (tribuary) estimates refer to all tributaries entering valley reach; gw (ground water) estimates refer to entire valley reach 
Valley 

stream

Site or flowcomponent

identifier*

USGS

station

identifier

Discharge

 or flow

 (ft3/s) Major-ion water type

Specific

conductance

(mS/cm)

Sodium

(Na)

Potassium

 (K)

Magnesium

(Mg)

Calcium

(Ca)

Chloride 

(Cl)

Sulfate 

(SO4)

car

(H

August 2001 Survey Batavia Kill UBK 0141309740 0.94 Ca-HCO3 67 2.5 0.58 1.3 7.8 2.5 4.5 

BK1 trib 0.1 Ca-HCO3 113 4.0 0.51 2.2 14.3 4.6 4.7 

BK1 gw 0.8 Ca-Na-HCO3-Cl 80 4.8 0.77 1.3 7.2 8.7 6.3 

MBK 01413098 1.84 Ca-Na-HCO3-Cl 75 3.6 0.66 1.4 7.9 5.3 5.3 

BK2 trib 0 -- -- -- -- -- -- -- -- 

BK2 gw 0.69 Ca-Na-HCO3-Cl 83 4.7 0.74 1.4 8.0 7.8 6.1 

LBK 01413099 2.53 Ca-Na-HCO3-Cl 86 4.2 0.66 1.6 8.9 6.5 5.4 

East Branch UEBD 01413070 0.21 Ca-Na-HCO3-Cl 145 9.8 0.97 2.0 13.2 13.3 3.6 

 Delaware EBD1 trib 0.02 Ca-HCO3-SO4 57 1.8 0.39 1.1 7.0 1.3 5.4 

EBD1 gw 0.85 Ca-Na-HCO3-Cl 140 12.2 0.95 1.9 11.6 13.3 5.2 

MEBD 01413088 1.08 Ca-Na-HCO3-Cl 139 11.6 0.94 1.9 11.8 13.1 4.9 

EBD2 trib -- -- -- -- -- -- -- -- -- 

EBD2 gw 2.38 Ca-Na-HCO3-Cl 123 7.2 0.98 1.9 11.7 12.2 6.8 

LEBD 01413092 3.46 Ca-Na-HCO3-Cl 128 8.6 0.97 1.9 11.7 12.5 6.2 

Mill Brook UMB 01414310 2.65 Ca-HCO3-SO4 59 1.3 0.5 1.1 7.4 2.3 5.4 

MB1 trib 0.47 Ca-Mg-HCO3-SO4 46 1.0 0.45 1.4 5.0 1.1 5.5 

MB1 gw 1.55 Ca-HCO3-SO4 48 1.6 0.62 1.2 6.1 2.4 6.0 

MMB 01414340 4.67 Ca-HCO3-SO4 54 1.3 0.5 1.2 6.3 2.2 5.4 

MB2 trib 0.64 Ca-Mg-HCO3-SO4 62 2.4 0.48 1.6 6.0 3.0 5.8 

MB2 gw 1.25 Ca-Mg-HCO3 87 3.4 0.98 2.0 8.7 4.9 5.2 

LMB 01414500 6.56 Ca-Mg-HCO3-SO4 61 1.8 0.59 1.4 6.8 2.8 5.4 

Platte Kill UPK 10413936 1.42 Ca-Mg-HCO3 89 3.3 0.99 2.1 8.9 5.4 5.3 

PK trib 0.13 Ca-Mg-HCO3 90 3.5 0.36 2.4 9.3 4.3 4.7 

PK gw 0.48 Ca-Na-HCO3-Cl 149 8.0 1.64 3.1 14.0 13.0 9.3 

LPK 01413945 2.03 Ca-Mg-Na-HCO3-Cl 103 4.4 1.1 2.4 10.1 7.1 6.2 

Tremper Kill UTK 01414865 1.94 Ca-Na-Cl-HCO3 146 10.7 1.47 2.8 10.3 21.5 6.6 

TK trib 0.05 Ca-Mg-HCO3-SO4 65 1.9 0.19 2.3 7.1 1.2 6.7 

TK gw 1.18 -- -- -- -- -- -- -- -- 

LTK 0141500 3.17 Ca-Na-Mg-HCO3-Cl 106 6.3 1.08 2.4 8.5 12.2 6.2 

Terry Clove Kill UTC 01415438 0.12 Ca-Mg-HCO3 76 1.8 2.68 2.0 7.6 1.8 6.5 

TC trib 0.05 Ca-Mg-HCO3-SO4 65 1.9 0.19 2.3 7.1 1.2 6.7 

TC gw 0.55 Ca-Mg-HCO3 84 2.5 1.7 2.6 8.5 2.6 7.2 

 LTC 01415465 0.72 Ca-Mg-HCO3 82 2.4 1.82 2.5 8.3 2.4 7.1 

Appendix A (continued) . Valley-stream discharge at sampling sites and tributary discharge and ground-water flow into reach, with majo

major-ion concentration during baseflow-sampling surveys in Pepacton Reservoir watershed in southeastern New York, July and August