SIMULATION OF A VALLEY-FILL AQUIFER SYSTEM TO 

DELINEATE FLOW PATHS, CONTRIBUTING AREAS, AND 

TRAVELTIME TO WELLFIELDS IN SOUTHWESTERN 

BROOME COUNTY, NEW YORK

By STEPHEN W. WOLCOTT and WILLIAM F. COON

______________________________________

U.S. GEOLOGICAL SURVEY

Water-Resources Investigations Report 01-4171

 (version 2.0) 

Prepared in Cooperation with 

U.S. ENVIRONMENTAL PROTECTION AGENCY and the

NEW YORK STATE DEPARTMENT OF ENVIRONMENTAL CONSERVATION

Troy, New York

2001
ii

U.S. DEPARTMENT OF THE INTERIOR

Gail A. Norton, Secretary

U.S. GEOLOGICAL SURVEY

Charles G. Groat, Director

_________________________________________________________________________________

For additional information, including digital input Copies of this report may be

data for the ground-water programs, purchased from:

MODFLOW and MODPATH, write to:

District Chief U.S. Geological Survey

U.S. Geological Survey Branch of Information Services

425 Jordan Road Box 25286

Troy, NY 12180-8349 Denver, CO 80225-0286
Contents III

CONTENTS

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

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

Purpose and scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

Previous studies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

Approach . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

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

Simulated Hydrogeologic system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

Description. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

Recharge . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

Discharge . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

Hydrologic boundaries . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

Hydraulic characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

Ground-water flow patterns . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

Simulation Enhancements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

Stream-aquifer relations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

Model recalibration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

Particle tracking. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

Contributing areas . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

Flow paths . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

Travel time. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

Limitations. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

References cited. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

FIGURES

1. Map of study area showing locations of aquifer and ground-water flow model boundaries, major geographic 

features, and municipal and industrial supply wells in the Susquehanna River valley in southwestern Broome 

County, N.Y. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

2. Map of model area and vicinity showing channeled and unchanneled upland areas that 

contribute recharge to the valley-fill aquifer. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

3. Map showing model grid and locations of stream cells, observation wells, and supply wells in valley-fill aquifer 

system of the Susquehanna River valley in southwestern Broome County, N.Y.: 

A. Study area . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

B. Inset from study area . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

4. A hypothetical valley-fill cross section from Randall (1986, fig. 6) showing geologicconfiguration, water bearing 

units, and subsequent model representation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

5. Map of model area showing extent of lower aquifer

A. Bedrock-surface altitude . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 

B. Thickness . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

6. Contributing areas of supply wells in valley-fill aquifer system in the Susquehanna River valley, in southwestern 

Broome County, N.Y. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

7. Particle flow paths from supply wells and 3-year travel distances in valley-fill aquifer system for the upper model 

layer of the Susquehanna River valley in southwestern Broome County, N.Y. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

8. Map showing particle flow paths from supply wells and 3-year travel distances in the valley-fill aquifer system 

in the lower model layer in the Susquehanna River valley, southwestern Broome County, N.Y. . . . . . . . . . . . . . . . . . 23

9. Map showing 3-year travel distances along flow paths to municipal supply well Endicott 32 (Ranney well, Bm 50) 
IV Contents

at high, medium, and low porosity values, in: A. Upper model layer; B. Lower model layer . . . . . . . . . . . . . . . . . . . 24

TABLES

1. Municipal and industrial ground-water withdrawals during April 1981 and 1990 in the 

Susquehanna River valley, southwestern Broome County, N.Y. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

2. Estimated hydrologic characteristics used in model simulation of the Susquehanna River 

and its tributaries in southwestern Broome County, N.Y. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

3. Observed and simulated steady-state water levels for April 1981 in the Susquehanna River 

valley, southwestern Broome County, N.Y. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

4. Simulated steady-state ground-water budget under average conditions during April 1981 for the valley-fill aquifer 

system of the Susquehanna River, southwestern Broome County, N.Y. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

5. Ranges in porosity used in model sensitivity analysis for unconsolidated materials 

commonly found in the valley-fill aquifer system in the Susquehanna River valley, 

southwestern Broome County, N.Y.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

CONVERSION FACTORS AND VERTICAL DATUM

For the convenience of readers who prefer metric (International System) units to the inch-pound unit 

used in this report, the following conversion factors may be used:

Multiply By To obtain

Length

inch (in) 25.4 millimeter 

foot (ft) 0.3048 meter 

mile (mi) 1.609 kilometer 

Area

square mile (mi2) 2.590 square kilometer 

Flow

gallon per minute (gal/min) 0.06309 liter per second 

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

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

million gallons per day (Mgal/d) 44.375 liter per second

Transmissivity

foot squared per day (ft2/d) 0.0929 meter squared per day 

Hydraulic conductivity

foot per day (ft/d) 0.3048 meter per day 

foot per mile (ft/mi) 0.1894 meter per kilometer 

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

datum derived from a general adjustment of the first-order level nets of both the United States and Canada, formerly called 

Sea Level Datum of 1929.
Introduction 1

Simulation of a Valley-Fill Aquifer System to Delineate 

Flow Paths, Contributing Areas, and Traveltime to 

Wellfields in Southwestern Broome County, New York

By Stephen W. Wolcott and William F. Coon

ABSTRACT

A valley-fill aquifer system that extends 

along a 14-mile reach of the Susquehanna River 

valley in southwestern Broome County, N.Y., is a 

major source of water supply to local municipalities and industries, but is highly susceptible to 

contamination from human activities. Protection 

of ground-water supplies requires accurate delineation of the areas that are the sources of water 

pumped by wells. A previously developed twolayer steady-state ground-water flow model of the 

aquifer system was upgraded with an improved 

method of simulating stream-aquifer interactions, 

then recalibrated and coupled to a particle-tracking program. Three-dimensional, ground-water 

flow modeling coupled with particle tracking is 

the most reliable method of simulating groundwater flow paths in multiaquifer systems such as 

this; it also allows delineation of contributing 

areas to wellfields. A primary advantage of threedimensional particle-tracking analysis is that it 

shows the complexities of the flow paths in each 

aquifer.

Model and particle tracking analyses indicate that groundwater frequently follows convoluted three-dimensional flow paths. The 

contributing areas of individual supply wells in 

this aquifer system each has a unique flow pattern 

and shape. Results of the model simulation indicate that recharge from precipitation, rivers, and 

tributaries contribute 35 percent, 29 percent, and 

25 percent, respectively to the aquifer system and 

that pumpage from supply wells accounts for 67 

percent of the discharge from the aquifer system. 

Particle-tracking results indicate that the simulated contributing areas to the 24 supply wells 

includes most of the valley floor.

INTRODUCTION

Ground-water contamination can adversely affect 

the health and economy of communities that depend 

on ground water for municipal and industrial use. 

Therefore, ground-water protection is becoming an 

integral part of local, state, and federal strategies for 

protection of public-water supplies. Congress 

established the Wellhead Protection Program through 

amendments to the Safe Drinking Water Act of 1974. 

Within these amendments is the requirement that each 

State identify the land area that contributes water to 

public-supply wells and enact programs to prevent 

contamination of ground water underlying these areas. 

In this report, the term “contributing area” is used 

to designate the land area that contributes water to a 

supply well, the synonymous term “capture zone” are 

also commonly used. These terms should not be 

confused with the term “recharge area” which is 

generally defined as land-surface area from which an 

aquifer receives recharges (Barlow, 1997).

Analysis of complex multi-aquifer systems has 

improved greatly with the development of algorithms 

that track the movement of simulated ground water 

particles within numerical flow models. Particle 

tracking is a modeling technique that allows 

delineation of contributing areas of a well by 

computing the movement of water particles from the 

point at which they enter the flow system at land 

surface to a discharging well. The starting locations of 

particles that reach the well define the area that 

contributes water to that well. Numerical modeling 
2 Simulation of a Valley-Fill Aquifer System to Delineate Flow Paths, Contributing Areas, and Traveltime to 

Wellfields in Southwestern Broome County, New York

coupled with particle tracking is an improvement over 

simpler analytical methods and two-dimensional flownet analyses because it enables delineation of recharge 

areas in complex multi-aquifer flow systems. 

Although two-dimensional flow-net analysis is useful 

for systems with simple, two-dimensional flow, 

construction of a two-dimensional flow net to 

represent three-dimensional flow is difficult and can 

yield inaccurate results because it disregards vertical 

flow. Particle tracking provides a relatively simple, yet 

quantitatively powerful, alternative to flow-net 

analysis for delineation of contributing areas to publicsupply wells and is superior to these methods for 

complex multiaquifer systems (Barlow, 1997).

The valley-fill aquifer system in the study area, a 

14-mi reach of the Susquehanna River valley in 

southwestern Broome County, N.Y. (fig. 1), is the sole 

source of water supply to more than half the 

population of Broome County (Yager, 1986) but is 

highly susceptible to contamination from human 

activities (Waller and Finch, 1982). During 1981, 26.1 

Mgal/d was pumped from 24 municipal and industrial 

wells screened in the valley-fill aquifer. The valley-fill 

material in the Susquehanna River and Chenango 

River valleys, which converge at Binghamton, is 1 to 2 

miles wide and is commonly 100 to 200 ft thick but 

can be as much as 300 ft thick in some places 

(Randall, 1972). The unconsolidated materials that 

form the valley fill range from sand and gravel in the 

most productive parts of the aquifer to silt and clay in 

the many discontinuous confining units. The 

Susquehanna and Chenango Rivers and tributary 

streams that cross the valley fill are in direct hydraulic 

connection with the aquifer system in many places 

and, thus, can provide significant recharge to wells.

In 1989, the U.S. Geological Survey (USGS) in 

cooperation with the New York State Department of 

Environmental Conservation and the U.S. 

Environmental Protection Agency, began a study to 

delineate, by numerical particle-tracking methods, the 

contributing areas to the 24 municipal and industrial 

supply wells in the valley system for use in waterresources planning.

Purpose and Scope

This report describes a particle-tracking analysis 

of the ground-water flow system of the Susquehanna 

River valley. It includes (1) a brief description of the 

valley-fill aquifer system, (2) a discussion of the 

modifications to a previously documented groundwater flow model of the aquifer system; (3) an 

explanation of particle tracking analyses, and (4) maps 

delineating the simulated contributing areas and 

ground-water flow paths to water-supply wells as 

indicated by flow modeling and particle tracking.

Previous Studies

Most of the data for this study were obtained in 

previous investigations. Hollyday (1969) made a 

preliminary evaluation of the hydrogeology of the 

Susquehanna River basin in New York State that 

included an economic feasibility study for developing 

ground water for public supply. Holecek and others 

(1982) mapped in detail the surficial geology, waterinfiltration potential, aquifer thickness, and 

potentiometric surface of the valley-fill aquifer system 

throughout the Endicott, Johnson City, and 

Binghamton areaand Randall (1977) provided records 

of wells and test borings and provided a detailed 

analysis of the aquifer system from western 

Binghamton to central Johnson City. Waller and Finch 

(1982) summarized the work of Holecek and others 

(1982), in the Endicott, Johnson City, and Binghamton 

valley-fill aquifer system and cited all pertinent 

references to date. MacNish and Randall (1982) 

developed a method for estimating the yield of 

stratified-drift aquifers in the Susquehanna River basin 

by accounting for and combining principal factors that 

control aquifer recharge, such as precipitation, 

seepage, and infiltration. 

These initial studies provided much of the 

information needed to define the aquifer geometry and 

the hydrogeologic properties and processes used in 

two numerical ground-water flow models of the area. 

The first, constructed by Randall (1986) used the 

computer program of Trescott and Larson (1976) and 

represented the study area described in this report (fig. 

1). The second, constructed by Yager (1986) and used 

the computer program of McDonald and Harbaugh 

(1988) and simulated ground-water flow within a 0.8 

mi2

 area about 2 mi east of Randall's (1986) modeled 

area. Yager (1991) used this model with nonlinear 

regression to estimate the hydraulic conductivity of 

riverbed and aquifer material.
3

.

.

.

.

.

.

.

.

.

.

..

.

.

. .

.

.

.

.

.

01513500

EXPLANATION

Valley - fill aquifer system

Boundary of model grid

Road

City or Village boundary

Direction of river flow

. Endicott 32 - Industrial or municipal supply wellidentified by name and number

01513500 - Stream flow gauging site and USGS station number

Base from US Geological Survey, 1974, 1:500,000

42o10'

42o07'30"

42o05'

76o 05' 76o 02' 30" 76o 75o 57' 30" 75o 55' 

0

0

1

1 2

MILES

KILOMETERS

CC

Outline area shown in fig. 9

Broo

m

e

County

UNION

UNION

2

Crestview 1,2,3

Endicott 32

Castle Gardens

Endicott 5,28

Vestal 1-2

Vestal 1-1

Endicott

VESTAL

JOHNSON CITY

BIN

IBM 5 Endicott 30

Vestal 4-2

Vestal 4-3

Vestal 4-4

IBM

Country Club

Johnson City

GE

Johnson City 2,3

Anitec 11 Anitec 10

Titchner

G

SusquehannaRi v e r

Susquehanna River

Nan t ci oke

Creek

Tioga

County

Introduction

Figure 1. Map of study area showing locations of aquifer and ground-water flow model boundaries, major geographic features, and m

wells in the Susquehanna River valley in southwestern Broome County, N.Y.
4 Simulation of a Valley-Fill Aquifer System to Delineate Flow Paths, Contributing Areas, and Traveltime to 

Wellfields in Southwestern Broome County, New York

Approach

The delineation of contributing areas of municipal 

and industrial wells in this study consisted of two 

steps: (1) upgrading and recalibrating the numerical 

ground-water flow model developed by Randall 

(1986); and (2) application of particle-tracking to the 

simulated results. 

The aquifer geometry, hydrogeologic 

characteristics, and development of the ground-water 

flow numerical model on which this study was based, 

are summarized in Randall (1986). In this study the 

model was upgraded as follows: (1) the input data to 

the Trescott and Larson (1976) ground-water flow 

model were converted into an input data set 

compatible with the McDonald and Harbaugh (1988) 

ground-water-flow model (MODFLOW) (A.L. Kontis, 

U.S. Geological Survey, written commun. 1989), (2) 

recharge wells that were used to simulate tributary 

stream inflow to the ground-water system were 

eliminated and replaced with the Stream Package of 

Prudic (1989), (3) constant-head nodes that were used 

to simulate interaction of the aquifer with the 

Susquehanna and Chenango Rivers were replaced 

through the application of the Stream Package, and (4) 

the original model, which displayed a systematic bias 

between simulated and observed heads, was 

recalibrated such that differences between observed 

and simulated heads were minimized and randomly 

distributed.

Contributing-area boundaries, ground-water flow 

paths, and traveltimes along flow paths were 

delineated by the numerical particle-tracking computer 

program MODPATH (Pollock, 1999). MODPATH is a 

post-processing procedure that uses the flow between 

model cells obtained from a MODFLOW steady-state 

simulation to compute and display flow paths 

(Pollock, 1999).

Acknowledgments

Ground-water withdrawal data, site maps, and data 

on pumping operations were provided by the Broome 

County Department of Health, International Business 

Machines Corp., Anitec Image Corp., and General 

Electric. The authors thank Allan Randall of the U.S. 

Geological Survey (retired) for hydrogeologic 

descriptions of the study area.

SIMULATED HYDROGEOLOGIC SYSTEM

The valley-fill aquifer system that was simulated 

in this study encompasses about 30 mi2 along a 14-mi 

reach of the Susquehanna River valley (fig. 1). The 

primary sources of recharge to the system are direct 

infiltration of precipitation, induced infiltration from 

the Chenango and Susquehanna Rivers, and natural 

infiltration from tributary streams where they cross the 

valley floor. The primary discharges from the aquifer 

are the withdrawals of ground water for municipal and 

industrial supply and seepage to the Susquehanna and 

Chenango Rivers. The ground-water flow system has 

been documented in detail by Randall (1986) and is 

described briefly below.

Description

The valley-fill aquifer system lies within the 

bedrock valleys of the Susquehanna and Chenango 

Rivers. The bedrock surface along the center of the 

valley is about 100 to 200 ft below land surface but can 

reach depths of 300 ft locally. The aquifer consists 

mostly of sand and gravel with discontinuous 

confining units of silt and clay, and has a wide range in 

horizontal and vertical hydraulic conductivity. 

Recharge from precipitation enters the system at the 

water table. Water also enters or leaves the aquifer 

along the course of rivers and their tributary streams. 

Recharge from precipitation and infiltration from 

streams and rivers generally moves through the aquifer 

toward supply wells or discharges to the Susquehanna 

River.

Recharge

Sources of aquifer recharge to the valley-fill 

aquifer system are (1) precipitation that infiltrates to 

the aquifer, (2) precipitation that falls on hillsides 

bordering the aquifer and infiltrates into the aquifer 

along the valley edges (unchanneled upland recharge), 

(3) natural infiltration from tributary streams 

(channeled upland recharge) and from the two rivers 

that cross the valley floor, and (4) induced infiltration 

from streams and rivers in areas near supply wells. 

Locations of channeled and unchanneled areas that 

contribute recharge to the valley-fill aquifer system are 

shown in figure 2.

Recharge rates applied to the valley floor as 

calculated by Randall (1986) are 15.5 in/yr. 

Unchanneled flow from hillsides is applied as recharge 
5

Susquehanna

River

EXPLANATION

Direction of flow in river or creek

River or Creek

Model Boundary

Road

Valley-fill aquifer system

Uplands that contribute

 channeled recharge to

 valley-fill aquifer system

Uplands that contribute

 unchanneled recharge to

 valley-fill aquifer system

NEW YORK

PENNSYLVANIA

76o 07' 30" 76o 75o 52' 30"

42o

07'

30"

42o

Interstate 81

Interstate 88

Interstate 81

Rte. 12

Rte. 17

Rte. 17

Rte. 434

Rte. 26

Rte. 7

Rte. 17

Rte. 26

NEW YORK

LOCATION MAP

Nanticoke

Creek

Chenango

River

Base from US Geological Survey, 1974, 1:500,000

0

0

5

5

MILES

KILOMETERS

TIOGA

COUNTY BROOME

COUNTY

Simulated Hydrogeologic System

Figure 2. Map of model area and vicinity showing channeled and unchanneled upland areas that 

contribute recharge to the valley-fill aquifer.
6 Simulation of a Valley-Fill Aquifer System to Delineate Flow Paths, Contributing Areas, and Traveltime to 

Wellfields in Southwestern Broome County, New York

to the valley floor on upper aquifer and range from 

15.5 to 155 in/yr depending on the local setting. A full 

description of the methods used to calculate these rates 

are given in Randall (1986). Infiltration rates from 

streams and rivers varies locally and is described 

further on in the section “Stream-aquifer relations”.

The largest source of recharge is precipitation that 

directly infiltrates the valley-fill aquifer system. 

Precipitation in the Susquehanna River valley averages 

36 in/yr, of which 21 to 24 in/yr reaches the water 

table (Randall, 1986). The distribution of recharge 

from precipitation is assumed for modeling purposes 

to be uniform throughout the valley. Natural 

infiltration from tributary streams and rivers that cross 

the valley floor, and induced infiltration from streams 

and rivers near production wells, each provide nearly 

as much recharge as precipitation, but the amount of 

natural and induced infiltration from streams and 

rivers varies locally and occurs only where the head in 

the underlying aquifer is lower than the stage in the 

stream or river. Induced infiltration is greatest near 

supply wells that are close to, and hydraulically 

connected to rivers (Randall, 1986).

Discharge

Ground water discharges from the aquifer to (1) 

municipal and industrial supply wells, (2) the 

Chenango and Susquehanna Rivers, (3) tributary 

streams that cross the valley floor, and (4) the 

atmosphere through ground-water evapotranspiration. 

Pumping constitutes by far the largest discharge from 

the aquifer system. Under nonpumping conditions, the 

largest discharge would be seepage from the aquifer to 

the Chenango and Susquehanna Rivers. Pumping 

alters the ground-water flow patterns and decreases the 

discharge of ground water to rivers and streams. 

Tributary streams that cross the valley floor generally 

recharge the aquifer system along their courses. 

Exceptions occur where they enter the Susquehanna 

and Chenango Rivers, where the head in the aquifer is 

higher than the stream stage and results in the 

discharge of ground water from the aquifer to the 

stream. Ground-water evapotranspiration is seasonally 

variable and may be substantial in areas with a shallow 

water table, but it was not simulated in this study.

Randall (1986) used average pumping rates for 

April 1981 for his steady-state simulation. During this 

period, withdrawals from the valley-fill aquifer system 

averaged 26.1 Mgal/d, of which 21.1 

Mgal/d was withdrawn from 18 municipal wells and 

5.0 Mgal/d from 7 industrial supply wells. More recent 

(1990) average annual withdrawal rates indicate that 

pumpage for municipal supply decreased to 15.1 

Mgal/d, and industrial pumpage increased to 6.8 Mgal/

d. The increases in industrial pumping occurred at 

industrial wellfields in the City of Binghamton and at 

eight industrial recovery and interceptor wells in the 

Village of Endicott. Municipal and industrial groundwater withdrawals during these periods are listed in 

table 1.

Hydrologic Boundaries

The upper boundary of the valley-fill aquifer 

system is the water table (a flux boundary) where 

recharge from precipitation enters the system. The 

Chenango and Susquehanna Rivers, as well as the 

tributary streams crossing the valley floor, are 

considered part of the upper boundary in the model 

because considerable exchange of water occurs 

between the rivers and streams and the aquifer. 

The lateral boundaries of the valley-fill aquifer 

system are the bedrock valley walls. The largest total 

flux along this boundary is the inflow of unchanneled 

runoff from the bordering till and bedrock uplands. 

Minor fluxes of ground water occur as underflow 

where the Chenango and Susquehanna Rivers enter the 

model area and where the Susquehanna River exits the 

model area. The lateral boundaries are simulated as 

constant-flux boundaries.

The bottom of the simulated flow system the 

bedrock, which and is represented as a no-flow 

boundary. Bedrock crops out at or near the valley sides 

and ranges from 100 to 200 ft below land surface at the 

center of the valley, although is not necessarily deepest 

below the Chenango or Susquehanna Rivers; it also 

crops out on a hill east of the confluence of Nanticoke 

Creek and the Susquehanna River in the center of the 

valley.

Hydraulic Characteristics

The valley-fill aquifer system can be considered to 

consist of an upper and a lower aquifer. Both consist of 

sand and gravel with interbedded stringers of silt and 

clay in some areas. The upper and lower aquifers are 

separated in most places by a silt and clay confining 

unit, but where this unit is absent the two aquifers are 

in direct hydraulic contact with each other. The 

horizontal hydraulic conductivity of the upper aquifer 

ranges from 10 ft/d to 225 ft/d and averages about 130 
7

Table 1. Municipal and industrial ground-water withdrawals during April 1981 and 1990 in the 

Susquehanna River valley, Broome County, N.Y.

[Well locations shown on figs. 3A and 3B. Withdrawal rates are in ft3/s (cubic feet per second. Mgal/d, million gallons per day.] 

1

 Recvry, Recovery; Intrcptr, interceptor; Gov't, government; Ctr, center.

2

 System is designated as upper and lower aquifers, simulated by upper and lower model layers.

3

 April 1981 withdrawal rates were used for model simulation and total 40.37 ft3/s (26.09 Mgal/d).

4

 1990 withdrawal rates are provided to show current conditions and total 33.90 ft3/s (21.91 Mgal/d).

5

 Withdrawal rate is estimated from owner’s incomplete records.

Well owner and name 1

USGS 

local well 

no.

Location

Model2

layer

Model cell Withdrawal rate

Latitude Longitude Row Column April 19813 19904

Owego; Crest View 1 TI 590 42°04' 04" 076°07' 08" lower 55 6 0.13 0.12

Owego; Crest View 2 TI 592 42°04' 07" 076°07' 12" lower 57 7 .04 .06

Owego; Crest View 3 TI 591 42°04' 05" 076°07' 09" lower 56 7 .03 .06

Vestal; 1-1 BM 73 42°05' 25" 076°03' 22" lower 38 40 1.70 ----

Vestal; 1-2 BM 61 42°05' 18" 076°03' 37" lower 40 37 .83 ----

Vestal; 1-3 BM 62 42°05' 19" 076°03' 40" lower 39 36 ---- 1.73

Vestal; 4-2 BM 160 42°06' 28" 075°59' 54" lower 19 82 1.70 1.64

Vestal; 4-3 BM 186 42°06' 37" 075°59' 50" lower 16 84 .60 .49

Vestal; 4-4 BM 196 42°06' 42" 075°59' 44" lower 14 86 2.34 1.15

Vestal; 5-1, Castle Gardens BM 42 42°04' 42" 076°05' 20" lower 48 20 .05 .13

Endicott; 5 BM 89 42°05' 39" 076°03' 10" lower 32 43 5.50 1.67

Endicott; 28, Park Well BM 90 42°05' 40" 076°03' 07" lower 31 44 3.40 1.58

Endicott; 30, Endwell BM 139 42°06' 06" 076°01' 01" upper 26 68 1.50 ----

Endicott; 32, Ranney Well BM 50 42°05' 04" 076°04' 50" lower 43 26 8.35 8.24

Endicott; 36, Endwell BM 136 42°06' 05" 076°01' 02" upper 26 68 ---- .23

Endicott; 37, Endwell BM 713 42°06' 06" 076°01' 01" upper 26 68 ---- .51

Endicott; Purge Well BM 714 42°05' 07" 076°05' 01" upper 41 24 ---- 1.11

IBM; Supply Well 5 BM 133 42°06' 02" 076°02' 06" lower 25 56 .625 .75

IBM; EN 38, Recvry Well BM 715 42°06' 26" 076°02' 47" upper 14 49 ---- .01

IBM; EN 107, Recvry Well BM 716 42°06' 25" 076°02' 53" upper 14 48 ---- .01

IBM; EN 120, Intrcptr Well BM 717 42°06' 12" 076°02' 49" upper 19 48 ---- .03

IBM; EN 133, Intrcptr Well BM 718 42°06' 13" 076°03' 02" upper 18 46 ---- .22

IBM; EN 154, Intrcptr Well BM 719 42°06' 16" 076°03' 18" upper 16 43 ---- .09

IBM; EN 160, Intrcptr Well BM 720 42°06' 11" 076°02' 50" upper 19 48 ---- .03

IBM; EN 175, Intrcptr Well BM 721 42°06' 11" 076°02' 34" upper 20 50 ---- .01

IBM; EN 185, Intrcptr Well BM 722 42°06' 10" 076°02' 36" upper 20 50 ---- .03

IBM; Country Club BM 234 42°07' 16" 075°59' 13" upper 5 92 .44 .48

Johnson City; 2 BM 208 42°06' 46" 075°58' 42" lower 15 97 2.40 2.52

Johnson City; 3 BM 210 42°06' 47" 075°58' 42" lower 15 97 3.00 2.56

Johnson City; 6 BM 224 42°07' 03" 075°57' 46" lower 11 106 ---- .91

Johnson City; 7, Ballpark BM 231 42°07' 11" 075°57' 24" lower 9 110 2.80 1.39

General Electric BM 533 42°06' 49" 075°58' 26" lower 15 100 .30 .28

Anitec; 3 BM 183 42°06' 36" 075°55' 42" lower 27 123 ---- .13

Anitec; 5 BM 188 42°06' 38" 075°55' 46" lower 26 122 ---- 1.89

Anitec; 7 BM 161 42°06' 29" 075°54' 51" lower 33 135 ---- 1.09

Anitec; 9 BM 174 42°06' 31" 075°55' 05" lower 31 131 1.72 ----

Anitec; 10 BM 166 42°06' 30" 075°55' 18" lower 31 128 1.22 .13

Anitec; 11 BM 192 42°06' 40" 075°55' 58" lower 24 120 .64 1.58

Titchener BM 147 42°06' 16" 075°55' 19" lower 37 127 .065 .045

Broome Gov't Ctr; Well 23 BM 723 42°05' 50" 075°54' 44" upper 48 136 ---- .50

Broome Gov't Ctr; Well 24 BM 724 42°05' 49" 075°54' 43" upper 48 136 ---- .50

Broome Gov't Ctr; 

Exchange and Hawley St BM 725 42°05' 50" 075°54' 40" upper 48 138 1.005 ----

Simulated Hydrogeologic System
8 Simulation of a Valley-Fill Aquifer System to Delineate Flow Paths, Contributing Areas, and Traveltime to 

Wellfields in Southwestern Broome County, New York

ft/d. The vertical water-transmitting capacity of the 

confining unit (represented as leakance between layers 

and defined as the vertical hydraulic conductivity 

divided by the thickness of the confining unit) is about 

0.6 (ft/d)/ft in areas where the upper and lower 

aquifers are in direct contact with each other, and 

about 2.0 x 10-5 (ft/d)/ft in areas where the confining 

layer clearly separates the upper from the lower 

aquifer. Transmissivity of the lower aquifer ranges 

from 1,000 ft2/d at the valley sides to 40,000 ft2/d 

within isolated pockets found mostly along the center 

of the valley, and averages about 10,000 ft2

/d. These 

estimates of horizontal hydraulic conductivity of the 

upper layer, vertical water-transmitting capacity of the 

confining unit, and transmissivity of the lower layer 

are based on the results of model simulations and 

aquifer tests conducted by Randall (1986).

Ground-Water Flow Patterns

Under average climatic conditions, ground water 

flows downgradient from recharge areas such as the 

valley floor, or as unchanneled runoff near the valley 

walls or as channeled runoff from tributary streams, 

moves through the aquifer discharging to production 

wells or to the Chenango or Susquehanna Rivers. Most 

of the recharge that enters the upper aquifer discharges 

to these two rivers in the valley; the rest moves 

unimpeded into the lower aquifer in areas where the 

confining unit is absent. Most wells that tap this 

aquifer system are screened in the lower aquifer; the 

largest discharge from this unit is from these wells. 

The rate at which water moves through the lower 

aquifer toward these wells increases with increased 

pumping and decreases with distance from the well.

Simulation Enhancements

Enhancements to the data sets of Randall (1980) 

were adapted for MODFLOW by A.J. Kontis (U.S. 

Geological Survey, written commun., 1989) and 

include (1) the addition of a modular computer 

package (Stream Package) to improve simulation of 

stream-aquifer interactions (Prudic, 1989), and (2) 

recalibration of the model to provide random areal 

distribution of differences between simulated and 

observed heads. These enhancements are discussed 

below. The domain of the model grid and locations of 

stream nodes and supply wells are shown on figure 

3A. Figure 3B is a detail of the Endicott wellfield 

area). A hypothetical valley-fill cross section (fig. 4) 

adapted from Randall (1986, fig. 6) indicates a typical 

geological configuration and the water-bearing units 

and their representation in the two-layered model.

Stream-Aquifer Relations

In Randall's (1986) ground-water flow model, 

rivers and major streams were represented by 

constant-head nodes and tributary streams crossing the 

valley floor that contribute recharge to the aquifer by 

infiltration were simulated as recharge wells. In the 

present study, simulation of stream-aquifer relations 

was improved by use of the Stream Package of Prudic 

(1989) which simulates flux between the stream and 

the aquifer. This flux is dependent on (1) the 

difference between head in the aquifer and stage in the 

stream or river, and (2) the hydraulic properties of the 

streambed. Stream discharge is specified in the 

upstream nodes of each stream and increases in 

gaining reaches and decreases in losing reaches. The 

maximum rate of seepage from a stream to the aquifer 

is equal to the discharge of the stream, and the 

minimum rate of seepage is zero, which occurs if the 

stream has gone dry. Stream nodes were placed at the 

locations of all streams and rivers that appear on 7.5-

minute USGS quadrangle maps (fig. 3A and 3B). 

Stream discharge was not simulated at model cells that 

correspond to concrete culverts or channels that cover 

the streambed and thereby prevent infiltration.

Two methods were used to calculate the initial 

stream discharge at the upstream node where a stream 

or river enters the active area of the model. The initial 

stream discharge values for the Susquehanna and 

Chenango Rivers and Nanticoke Creek were 

calculated as the drainage area at upstream nodes, 

multiplied by the streamflow (per unit area) 

determined from the average stream discharge at the 

Susquehanna River at Vestal, N.Y. (station 01513500, 

fig. 1). The magnitude of the initial values for these 

rivers is not critical because the flux between the river 

and the aquifer is insignificant in relation to the 

discharge in the river. The initial discharge values for 

the remaining streams were calculated through a 

method developed by MacNish and Randall (1982), as 

the product of (1) the drainage area at the point where 

the stream enters the active part of the model grid, and 

(2) the average annual recharge from precipitation to 

surficial stratified-drift aquifers in the Susquehanna 

River basin as indicated in MacNish and Randall 

(1982, fig. 14), multiplied by (3) the average flow 
54 53

54

50

49

49 48

46

46

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10 11

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42 ̊

05'

42 ̊

07'

30"

42 ̊ 05' 75 ̊ 52' 30" 76 ̊ 07' 30" 76 ̊

76 ̊ 07' 30" 42 ̊ 07' 30" 76 ̊ 75 ̊ 52' 30"

Base from U.S. Geological Survey, 7.5-minute topographic quadrangles, 1:24,000

Apalachin, 1969; Binghamton East, 1968; Binghamton West, 1968; Castle Creek,

1968; Chenango Forks, 1968; Endicott, 1969; Maine, 1969

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WU BM 7

BM 466

BM 519

BM 520

BM 521

BM 111

BM 529

BM 530

BM 598

BM 599

BM 207

BM 534

BM 236

BM 121

BM 208

BM 538

BM 539

BM 540

BM 199

BM 542

BM 543

BM 66

BM 446

BM 99

BM 547

BM 548

BM 549

BM 550

BM 551

BM 552

BM 553

BM 554

BM 555

BM 556

BM 557

BM 558

BM 559

BM 237

BM 227

BM 224

BM 195

BM 204

BM 223

BM 233

BM 180

BM 605

BM 152

BM 211

BM 203

BM 604

BM 167

BM 201

BM 198

BM 143

BM 183

BM 191

BM 182

BM 114

BM 190

BM 166

BM 175

BM 174

BM 173

BM 155

BM 176

BM 588

BM 161

BM 153

BM 145

BM 156

BM 597

BM 171

BM 100

BM 140

TI 590

TI 592

TI 591

BM 73

BM 61

BM 62

BM 160

BM 186

BM 196

BM 42

BM 50

BM 136

BM 139

BM 713

BM 714

BM 234

BM 208

BM 210

BM 224

BM 231

BM 533

BM 183

BM 188

BM 161

BM 174 BM 166

BM 192

BM 147

BM 723

BM 724

BM 725

1

1 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100 105 110 115 120 125 130 135 140 145 150 155 157

1 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100 105 110 115 120 125 130 135 140 145 150 155 157

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Area shown in Figure 3B

EXPLANATION

Simulated stream cell, and beginning and ending

 stream-reach numbers. Stream names and 

 characteristics are listed in Table 2.

Active model cell boundary, upper layer.

Model grid row and column designation.

Well pumped in 1981 and/or 1990 for municipal 

 or industrial supply, or environmental cleanup.

Well owner's name and number are listed in Table 1.

Well used for water-level measurements during

 April 1981. Well owner's name and number

 are listed in Table 3.

BM 42 .

BM 99 .

80

5

Figure 3. Map showing model grid and locations of stream cells, observation wells, and supply wells in valley-fill aquifer system of the Susquehanna River valley in southwestern Broome County, N.Y. 

 

Simulated Hydrogeologic System 9
Figure 3. Map showing model grid and locations of stream cells, observation wells, and supply wells in valley-fill aquifer 

system of the Susquehanna River valley in southwestern Broome County, N.Y. 

 

10 Simulation of a Valley-Fill Aquifer System to Delineate Flow Paths, Contributing Areas, and Traveltime to Wellfields in Southwestern Broome County, New York 

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Well pumped in 1981 and/or 1990 for 

municipal or industrial supply, or 

environmental cleanup. Well owner's 

name and number are listed in Table 1. 

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GEOLOGIC

TION CONFIGURA

A

Bedrock 3 Outwash

2

Water table

TER-BEARING UNITS WA

(AQUIFERS)

B

1

ice-contact

deposits 2Lake deposits

(clay and silt)

5 Alluvium

Lake deposits 4 3 Ou wt

ash

2

1

5 Lake outwash

or alluvium

River

4

1

Kettlehole Kettlehole

Upper aquifer

Lower aquifer

C

MODEL

LAYER

Upper

Con- fining ("TK")

Lower

FLOW DIREC- TION

Horiz

Vert

Horiz

Med Med

Med

Med Med Med Med

Med

Med

Med

Med Med

Med

Med

Med

Med

Low

Low

Low Low

Low

Low Low Low

Low

Low

Low High High

High High

High

High

High High

High

High

High

Nil

Nil Nil Nil

WATER- TRANSMITTING CAPACITY

Fig. 4. A hypothetical valley-fill cross-section from Randall (1986, fig. 6) showing geologic 

configuration, water bearing units, and subsequent model representation 
Simulated Hydrogeologic System 11

duration for streams draining till-covered upland areas 

in the Susquehanna River basin, as indicated in 

MacNish and Randall (1982, fig. 15). The average 

flow duration for streams draining till-covered upland 

areas in the Susquehanna River basin is based on a 

duration of about 38 percent computed for April 1981 

at the Susquehanna River at Vestal (station 01513500, 

figure 1). Accurate discharge values for these small 

tributary streams is critical because natural and 

induced infiltration can cause them to dry up.

A streambed is hydraulic characteristics at a 

particular node in the model is incorporated into a 

streambed-conductance term defined as the product of 

streambed leakance (ratio of streambed vertical 

hydraulic conductivity to streambed thickness) and the 

area of the streambed. Selection of streambedthickness and streambed vertical hydraulic 

conductivity values was based on values given by 

Reynolds (1987) for the surficial outwash aquifer in 

Cortland County to the north (fig. 1 inset), and Yager 

(1986, 1991) in the valley-fill aquifer system of the 

Susquehanna River 2 mi upstream from the study area. 

A streambed thickness of 2.0 ft was chosen for the 

Susquehanna and Chenango Rivers, 1.0 ft for 

Nanticoke and Choconut Creek and 0.5 ft for the 

remaining tributary streams (fig. 3A and 3B). 

Streambed thickness probably is highly variable, but 

the available data are insufficient to quantify the 

variability. A streambed vertical hydraulic 

conductivity of 0.30 ft/d was chosen for the 

Susquehanna and Chenango Rivers; values for the 

remaining tributaries ranged from 0.50 to 2.50 ft/d. 

Values close to 0.50 ft/d were chosen for tributary 

streams in areas near the Susquehanna or Chenango 

Rivers to reflect the values used for these two major 

rivers. Most other tributaries were assigned values of 

1.50 ft/d, on the basis of results from the model 

calibrated by Randall (1986). Estimates of river and 

tributary stream depth (stage) range from 10 ft for the 

Susquehanna and Chenango Rivers to 0.5 ft for small 

tributary streams. These values were based on field 

observations and used for calculation of head in the 

stream. The estimated hydrologic characteristics of 

simulated streams are listed in table 2; locations of 

stream cells and stream reaches are shown on figures 

3A and 3B.

Model Recalibration

The model was calibrated to surface-water and 

ground-water data collected in April 1981, a period 

assumed to represent average steady-state conditions. 

Flow duration at the Susquehanna River at Vestal 

(station 01513500, figure 1) was 38 percent during 

that month. The locations and the amounts of ground 

water withdrawn by each well are listed in table 1. 

Observed water levels were compared with simulated 

values to assess the ability of the model to accurately 

represent the valley-fill aquifer system.

Randall’s (1986) data sets as converted for use 

with the MODFLOW ground-water model, required 

minor adjustments to the boundary conditions and 

hydraulic properties, and the addition of the Stream 

Package (Prudic, 1989). The bottom boundary of the 

upper model layer was lowered slightly and smoothed 

in the Endicott area, where the aquifer thins near the 

valley side. Other minor adjustments were made to the 

bottom boundaries of the upper model layer where 

justified by well-log data. Hydraulic conductivity in 

the Endicott area also was adjusted. These adjustments 

helped eliminate numerical instabilities in that area. 

Transmissivity of the lower model layer was adjusted 

in areas containing several production wells in 

accordance with data from previous aquifer tests. Most 

water levels that resulted from these adjustments 

closely matched observed water levels. Tributary 

stream discharges were simulated with the stream 

package (Purdic, 1989) described in the “Streamaquifer relations” section.

The numerical stability of the model was found to 

be sensitive to the initial water levels that were used to 

calculate a steady-state solution. When all model 

parameters were adjusted numerical instabilities in the 

form of widely oscillating water levels were generated 

for various configurations of starting water levels. The 

widest ranges of values, which were mostly in the 

upper model layer, were eliminated when MODFLOW 

was modified such that the saturated thickness in cells 

of the upper layer was set to a small finite thickness 

(0.1 ft) whenever it decreased to zero. The resulting 

heads in the upper layer were then examined, and if a 

particular head was below the bottom of the layer, it 

was raised to an elevation of 1 ft above the bottom of 

the upper layer. Use of this set of smoothed heads as 

the initial heads in the conventional version of 

MODFLOW eliminated the numerical instability.

Improvements in steady-state solutions during 

model calibration were identified through a 

comparison of the differences between observed and 

simulated heads (table 3) while (1) the distribution of 

the differences was kept random, and (2) the overall 
12 Simulation of a Valley-Fill Aquifer System to Delineate Flow Paths, Contributing Areas, and Traveltime to 

Wellfields in Southwestern Broome County, New York

water budget was kept consistent with Randall's 

(1986) ground-water flow model. The root-meansquare difference (RMS) between the simulated and 

observed heads was used to quantify model 

improvements as adjustments were made. The RMS of 

the calibrated model was about 3 ft in both layers. The 

simulated water budget for the valley-fill aquifer 

system of the Susquehanna River (table 4) indicates 

that direct infiltration of precipitation is the greatest 

single source of recharge and contributes 35 percent of 

the total recharge. Infiltration from the Susquehanna 

and Chenango Rivers and tributary streams crossing 

the valley floor contribute 29 and 25 percent, 

respectively. Withdrawals by supply wells have 

induced more infiltration than would occur under 

natural conditions. Unchanneled upland recharge, 

which occurs at the model's lateral boundaries, 

contributed 11 percent of the total recharge to the 

aquifer system.

Table 2. -Estimated hydrologic characteristics used in model simulation of the Susquehanna River and its tributaries

in southwestern Broome County, N.Y.

[Stream cells and model stream-reach locations are shown in figs. 3A and 3B. Trib, tributary; mi2

, square miles; ft, feet;

ft3/s cubic feet per second; ft/d, feet per day.] 

1 Simulated streamflow at first active model cell calculated by method described in MacNish and Randall (1982) unless otherwise stated. 

2 Simulated model streamflow at first active model cell is product of (1) drainage area and (2) streamflow per square mile as calculated from average 

streamflow at Susquehanna River at Vestal (station 01513500) during April 1981.

3 Vertical streambed conductivity is 0.25 ft/d at stream cells near Susquehanna River.

Stream name

Simulated stream 

reach

Drainage area 

at first active 

model cell 

(mi2)

Simulated 

discharge at 

first active 

model1 

(ft3/s)

Depth of 

water in 

stream 

(ft)

Streambed 

thickness 

(ft)

Vertical 

hydraulic 

conductivity of 

streambed

(ft/d)

Susquehanna River 1, 3, 5, 7, 13, 17, 

18, 19, 21, 22, 24, 

28, 30, 35, 36, 37, 

38, 48, 50, 52, 54

2270 29402 10.0 2.0 0.30

Unnamed trib. to Susquehanna River 2 .53 .37 .5 .5 1.50

Chamberlain Creek 4 1.17 .83 .5 .5 1.50

Pierce Creek 6 5.92 4.10 .5 .5 1.50

Chenango River 8, 10, 12 1590 2

2060 10.0 2.0 .30

Unnamed trib. to Chenango River 9 .38 .26 .5 .5 1.50

Brandywine Creek 11 1.04 .74 .5 .5 1.50

Finch Hollow 14 3.95 2.69 .5 .5 .75

Little Choconut Creek 15, 16 12.9 8.79 .5 .5 .75

Unnamed trib. to Susquehanna River 20 .88 .60 .5 .5 1.50

Patterson Creek 23 7.09 4.74 .5 .5 1.50

Willow Run 25, 27 1.26 .86 .5 .5 1.50

Unnamed trib. to Willow Run 26 .51 .35 .5 .5 1.50

Brixius Creek 29 1.79 1.02 .5 .5 1.50

Choconut Creek 31, 32, 33, 34 56.3 38.4 2.0 1.0 1.00

Nanticoke Creek 39, 41, 43, 45, 47 101 2

130 2.0 1.0 3

1.00

Day Hollow Creek 40 5.99 3.89 .5 .5 1.50

Unnamed trib. to Nanticoke Creek 42 .35 .23 .5 .5 1.50

Unnamed trib. to Nanticoke Creek 44 .38 .25 .5 .5 1.50

Dead Creek 46 1.08 .70 .5 .5 .50

Tracy Creek 49 8.51 5.53 .5 .5 2.50

Unnamed trib. to Susquehanna River 51 1.05 .68 .5 .5 1.50

Unnamed trib. to Susquehanna River 53 .62 .40 .5 .5 1.50
13

Table 3. Observed and simulated steady-state water levels for April 7-10, 1981, in Susquehanna River valley aquifer system 

in southwestern Broome County, N.Y.

[Well and model-cell locations are shown in figures 3A and 3B. Water-level data from Randall (1986) 

Well owner and

number or name1

USGS1

local 

number

Location

Model 

layer

Model cell Water-level altitude

Difference2

Latitude Longitude Row Column Observed Simulated (feet)

Village of Endicott

Endicott Kelly well WUBM7 42 ̊  ̊05’06” 076 ̊04’47” lower 42 26 786.78 787.89 1.11

USGS Mercerau Park BM 466 42 ̊05’27” 076 ̊03’44” lower 36 35 803.64 800.55 -3.09

IBM En 96 BM 467 42 ̊06’17” 076 ̊03’19” upper 15-6 42-3 819.23 825.06 5.83

IBM En 59 BM 468 42 ̊06’01” 076 ̊03’15” upper 22 42-3 819.48 815.15 -4.33

IBM En 95 BM 469 42 ̊06’11” 076 ̊03’17” upper 18 43 820.71 822.01 1.30

Endicott 23 BM 470 42 ̊05’41” 076 ̊03’10” upper 31 43 794.25 799.46 5.21

Endicott 6 BM 406 42 ̊05’39” 076 ̊03’13” lower 32 43 758.30 757.55 -0.75

IBM En 66 BM 472 42 ̊06’17” 076 ̊03’16” upper 15 43-4 822.12 827.77 5.65

IBM En 69 BM 473 42 ̊06’22” 076 ̊03’13” upper 13-4 44-5 827.75 831.10 3.35

IBM En 60 BM 474 42 ̊06’09” 076 ̊03’08” upper 19-20 45 822.29 823.78 1.49

IBM En 70 BM 475 42 ̊06’21” 076 ̊03’08” upper 14-5 45 827.25 830.02 2.77

IBM En 61 BM 477 42 ̊05’57” 076 ̊03’04” upper 24 45 820.89 816.07 -4.82

IBM End-1 BM 726 42 ̊05’57” 076 ̊03’04” lower 24 45 805.69 803.89 -1.80

IBM End-3 BM 478 42 ̊05’50” 076 ̊03’04” lower 27 45 802.12 797.32 -4.80

IBM En 71 BM 479 42 ̊06’25” 076 ̊03’08” upper 13 45-6 828.57 831.88 3.31

IBM En 26 BM 480 42 ̊06’22” 076 ̊03’05” upper 14 46 828.69 831.12 2.43

IBM En 94 BM 481 42 ̊06’12” 076 ̊03’04” upper 18 46 822.30 825.29 2.99

IBM En 76 BM 482 42 ̊06’16” 076 ̊03’01” upper 16-7 46-7 826.68 827.28 0.60

IBM En 72 BM 483 42 ̊06’24” 076 ̊03’03” upper 13 46-7 829.09 831.78 2.69

IBM En 63 BM 110 42 ̊05’58” 076 ̊02’57” upper 24-5 46-7 819.79 818.60 -1.19

IBM En 62 BM 485 42 ̊06’05” 076 ̊02’58” upper 21 46-7 822.65 824.46 1.81

IBM En 74 BM 486 42 ̊06’21” 076 ̊03’00” upper 14-5 47 829.63 830.63 1.00

IBM En 98 BM 487 42 ̊06’27” 076 ̊02’59” upper 13 47 835.70 831.69 -4.01

IBM En 91 BM 488 42 ̊06’13” 076 ̊02’58” upper 18 47 823.91 825.99 2.08

Endicott Motor Inn BM 109 42 ̊05’58” 076 ̊02’55” lower 24 47 803.95 800.39 -3.56

IBM En 24 BM 490 42 ̊06’17” 076 ̊02’55” upper 16 47-8 827.07 828.44 1.37

IBM En 93 BM 491 42 ̊06’10” 076 ̊02’50” upper 19-20 48 822.68 825.90 3.21

IBM En 92 BM 492 42 ̊06’12” 076 ̊02’52” upper 18-9 48 822.98 826.32 3.34

Endicott Trust BM 493 42 ̊06’12” 076 ̊02’53” lower 19 48 816.31 819.42 3.11

IBM En 64 BM 494 42 ̊06’03” 076 ̊02’51” upper 22 48 823.09 824.09 1.00

IBM En 29 BM 495 42 ̊06’13” 076 ̊02’49” upper 18-9 48-9 823.07 826.56 3.49

IBM En 27 BM 496 42 ̊06’23” 076 ̊02’29” upper 14 49 832.11 831.60 -0.51

IBM En 21 BM 497 42 ̊06’22” 076 ̊02’46” upper 15 49 831.60 830.64 -0.96

IBM En 19 BM 498 42 ̊06’19” 076 ̊02’47” upper 16 49 829.95 829.47 -0.48

IBM En 22 BM 499 42 ̊06’04” 076 ̊02’45” upper 22 49 822.89 823.97 1.08

IBM End-2 BM 500 42 ̊06’04” 076 ̊02’45” lower 22 49 803.87 801.81 -2.06

Endicott stable BM 95 42 ̊05’48” 076 ̊02’42” upper 29 49 804.50 804.44 -0.06

Endicott stable 8" TW BM 96 42 ̊05’48” 076 ̊02’42” lower 29 49 802.54 800.60 -1.94

IBM En 6 BM 503 42 ̊06’13” 076 ̊02’44” upper 18-9 49-50 822.09 827.02 4.93

IBM En 77 BM 727 42 ̊06’18” 076 ̊02’44” upper 16-7 49-50 827.68 829.07 1.39

IBM En 34 BM 505 42 ̊06’27” 076 ̊02’46” upper 13 49-50 830.98 832.45 1.47

IBM En 78 BM 506 42 ̊06’16” 076 ̊02’39” upper 17-8 50 827.50 828.32 0.82

IBM En 35 BM 507 42 ̊06’20” 076 ̊02’43” upper 15-6 50 829.40 830.31 0.91

IBM En 81 BM 508 42 ̊06’21” 076 ̊02’38” upper 15-6 50 830.01 830.31 0.30

IBM En 58 BM 509 42 ̊06’26” 076 ̊02’40” upper 13-4 50 831.34 832.40 1.06

IBM En 32 BM 510 42 ̊06’24” 076 ̊02’42” upper 14 50 831.64 831.99 0.35

Simulated Hydrogeologic System
14 Simulation of a Valley-Fill Aquifer System to Delineate Flow Paths, Contributing Areas, and Traveltime to 

Wellfields in Southwestern Broome County, New York

IBM Cafeteria BM 511 42 ̊06’17” 076 ̊02’35” lower 17 50 823.32 822.22 -1.10

IBM En 80 BM 512 42 ̊06’14” 076 ̊02’35” upper 18-9 50-1 827.34 827.22 -0.12

IBM En 23 BM 151 42 ̊06’18” 076 ̊02’37” upper 16-7 50-1 827.89 829.10 1.21

IBM En 79 BM 514 42 ̊06’10” 076 ̊02’34” upper 20 50-1 822.97 825.87 2.90

IBM En 84 BM 515 42 ̊06’33” 076 ̊02’35” upper 11 51 839.82 837.83 -1.99

IBM En 83 BM 516 42 ̊06’28” 076 ̊02’32” upper 13 51 833.29 833.88 0.59

IBM En 82 BM 517 72 ̊06’23” 076 ̊02’33” upper 15 51 828.63 830.45 1.82

IBM En 65 BM 518 42 ̊06’16” 076 ̊02’26” upper 18 52 828.79 827.15 -1.64

Town of Union

IBM Glendale GR 2 BM 519 42 ̊05’31” 076 ̊05’30” lower 28 20 815.62 815.56 -0.06

IBM Glendale GR 4 BM 520 42 ̊05’48” 076 ̊05’25” lower 21 21-2 824.78 820.58 -4.20

Rose/Batch Plant BM 521 42 ̊05’27” 076 ̊05’17” lower 31 22 805.25 806.52 1.27

Oliver Main BM 111 42 ̊05’58” 076 ̊04’50” lower 19 28 809.50 814.38 4.88

IBM En 86 BM 523 42 ̊06’27” 076 ̊02’23” upper 14 52-3 833.62 831.36 -2.26

IBM En 87 BM 524 42 ̊06’24” 076 ̊02’23” upper 15 52-3 829.96 828.71 -1.25

IBM En 30 BM 525 42 ̊06’25” 076 ̊02’15” lower 15 54-5 829.52 826.09 -3.43

IBM Well Field 2 BM 126 42 ̊06’01” 076 ̊02’09” lower 25 55 796.81 801.01 4.20

IBM Well Field 3 BM 728 42 ̊06’01” 076 ̊02’09” lower 25 55 796.88 801.01 4.13

IBM En 89 BM 528 42 ̊06’29” 076 ̊02’13” upper 13-4 55-6 835.26 835.31 0.05

Endicott B7 BM 529 42 ̊06’02” 076 ̊01’13” lower 27 64 809.31 807.33 -1.98

Endicott B2 BM 530 42 ̊06’04” 076 ̊01’13” upper 26 64-5 805.25 807.04 1.79

USGS Hill Park 6" BM 598 42 ̊06’48” 075 ̊58’50” lower 14 95 807.43 804.88 -2.55

Johnson City 1 BM 207 42 ̊06’46” 075 ̊58’40” lower 15 97 799.00 794.40 -4.60

Johnson City 2 BM 208 42 ̊06’46” 075 ̊58’42” lower 15 97 794.00 794.40 0.40

General Electric 2 BM 534 42 ̊06’49” 075 ̊58’29” lower 15 99 808.32 805.46 -2.86

IBM Country Club 2 BM 236 42 ̊07’19” 075 ̊59’10” upper 5 93 814.96 812.88 -2.08

USGS Hill Park 1" BM 599 42 ̊06’48” 075 ̊58’50” upper 14 95 812.81 810.70 -2.11

USGS BM 121 42 ̊06’57” 075 ̊58’35” upper 11 98 809.09 808.41 -0.68

Goudey Station 1 BM 538 42 ̊06’38” 075 ̊58’17” upper 19-20 99 815.68 812.30 -3.38

Goudey Station 3 BM 539 42 ̊06’45” 075 ̊58’26” upper 16-7 99-100 811.33 808.24 -3.09

Goudey Station 2 BM 540 42 ̊06’39” 075 ̊58’17” upper 19-20 100-1 818.27 813.22 -5.05

USGS Bm 119 BM 199 42 ̊06’43” 075 ̊58’09” upper 17-8 101-2 818.98 814.38 -4.60

Town of Vestal

Castle Gardens BM 542 42 ̊04’47” 076 ̊04’52” lower 48 25 802.07 802.36 0.29

James Dittrich BM 543 42 ̊04’55” 076 ̊04’48” upper 46 26 802.10 800.89 -1.21

Vestal 1-3 (1-14) BM 66 42 ̊05’21” 076 ̊03’41” lower 39 36 803.90 800.64 -3.26

H.J. Russell BM 446 42 ̊05’55” 076 ̊00’57” lower 31 69 807.10 808.91 1.81

Vestal 4-1 BM 99 42 ̊05’49” 076 ̊00’53” lower 35 70 814.96 811.36 -3.60

Monarch A BM 547 42 ̊06’28” 076 ̊00’00” upper 20 81 799.72 803.09 3.37

Monarch B BM 548 42 ̊06’26” 075 ̊59’59” upper 20-1 81 800.23 803.73 3.51

DEC TH-1 BM 549 42 ̊06’28” 075 ̊59’58” lower 20 81 801.68 803.01 1.33

DEC TH-2 BM 550 42 ̊07’27” 075 ̊59’58” lower 20 81 799.12 803.01 3.89

Barney Dickenson BM 551 42 ̊06’31” 075 ̊59’56” lower 18 82 799.19 799.70 0.51

USGS Prentice Rd. Is. 6" BM 552 42 ̊06’26” 075 ̊59’52” lower 20-1 83-4 799.88 802.22 2.34

USGS Prentice Rd. Is. 2.5" BM 553 42 ̊06’45” 075 ̊59’53” upper 13 84 808.40 807.66 -0.74

Vestal B-6 BM 554 42 ̊06’39” 075 ̊59’52” lower 15 84 803.64 801.74 -1.90

Vestal B-3 BM 555 42 ̊06’37” 075 ̊59’52” lower 16 84 794.44 797.36 2.92

Vestal B-2 BM 556 42 ̊06’38” 075 ̊59’50” lower 15-6 85 796.03 799.42 3.39

Well owner and

number or name1

USGS1

local 

number

Location

Model 

layer

Model cell Water-level altitude

Difference2

Latitude Longitude Row Column Observed Simulated (feet)

Table 3. (continued) Observed and simulated steady-state water levels for April 7-10, 1981, in Susquehanna River valley 

aquifer system 
15

1 USGS, U.S. Geological Survey; IBM, International Business Machines; DEC, New York State Department of Environmental Conservation; 

NYG&E, New York Electric and Gas.

2 Root-mean-square difference between observed and simulated water levels for nodes containing observation wells open to the upper layer

is 3.09 ft, and that for nodes in the lower layer is 2.99 ft.

NYG&E 3 BM 557 42 ̊06’22” 075 ̊59’46” upper 22 85 802.78 808.65 5.87

NYG&E 1 BM 558 42 ̊06’19” 075 ̊59’44” upper 23-4 85-6 820.32 824.65 4.33

NYG&E 2 BM 559 42 ̊06’22” 075 ̊59’39” upper 22-3 87 839.56 832.04 -7.52

Village of Johnson City

USGS Bm 120 BM 237 42 ̊07’26” 075 ̊58’41” upper 4 98 820.41 813.84 -6.57

Johnson City 5TH ST. BM 227 42 ̊07’03” 075 ̊58’17” lower 10 101 806.79 811.55 4.76

Johnson City 6 BM 224 42 ̊07’03” 075 ̊57’46” lower 11 106 811.42 811.95 0.53

USGS Bm 118 BM 195 42 ̊06’42” 075 ̊57’39” lower 20 106 823.91 820.10 -3.81

Wilson Hospital BM 204 42 ̊06’46” 075 ̊57’31” lower 18-9 107-8 822.33 819.97 -2.36

Johnson City 4 BM 223 42 ̊07’02” 075 ̊57’32” lower 12 108 811.60 811.59 -0.01

City of Binghamton

USGS Harry L. Drive BM 233 42 ̊07’15” 075 ̊56’55” upper 8-9 113-4 839.79 837.89 -1.90

USGS Bm 116 BM 180 42 ̊06’34” 075 ̊56’44” upper 25-6 114 824.02 826.88 2.86

ANITEC 27T BM 605 42 ̊06’39” 075 ̊56’30” lower 24 116 822.00 823.21 1.21

USGS Bm 101 BM 152 42 ̊06’21” 075 ̊56’25” upper 32 116 844.97 845.03 0.06

USGS Bm 111 BM 211 42 ̊06’51” 075 ̊56’17” upper 19-20 117-8 818.54 823.82 5.28

ANITEC 24T BM 203 42 ̊06’45” 075 ̊56’13” lower 22 118 814.10 819.08 4.98

ANITEC 25T BM 604 42 ̊06’38” 075 ̊56’08” lower 25 118 812.20 819.15 6.95

Fairbanks Co. BM 167 42 ̊06’30” 075 ̊56’11” lower 28 118 816.12 820.08 3.96

ANITEC 23T BM 201 42 ̊06’44” 075 ̊56’05” lower 22 119 813.30 816.51 3.21

ANITEC 21T BM 198 42 ̊06’43” 075 ̊55’59” lower 23 120 813.40 813.69 0.29

USGS Bm 117 BM 143 42 ̊06’12” 075 ̊55’47” upper 38 121 850.80 842.58 -8.22

ANITEC 3 BM 183 42 ̊06’36” 075 ̊55’42” lower 27 123 812.20 814.31 2.11

ANITEC 4 BM 191 42 ̊06’39” 075 ̊55’39” lower 26 124 812.00 814.15 2.15

ANITEC 2A BM 182 42 ̊06’37” 075 ̊55’38” lower 27 124 813.10 814.08 0.98

USGS Bm 114 BM 114 42 ̊06’15” 075 ̊55’20” lower 37 127 813.95 815.12 1.17

USGS Bm 113 BM 190 42 ̊06’39” 075 ̊55’20” upper 27 128 811.09 809.92 -1.17

ANITEC 10 BM 166 42 ̊06’30” 075 ̊55’18” lower 31 128 797.30 798.53 1.23

ANITEC 6 BM 175 42 ̊06’31” 075 ̊55’13” lower 31 129 810.32 805.68 -4.64

ANITEC 9 BM 174 42 ̊06’31” 075 ̊55’05” lower 31 131 804.11 802.29 -1.82

ANITEC 8 BM 173 42 ̊06’32” 075 ̊54’57” lower 31 133 812.42 815.84 3.42

USGS Well K BM 155 42 ̊06’26” 075 ̊54’57” lower 34 133 822.03 821.20 -0.83

USGS Bm 115 BM 176 42 ̊06’32” 075 ̊54’55” lower 31 134 813.80 819.43 5.63

ANITEC 33T BM 588 42 ̊06’22” 075 ̊54’51” lower 36 134 824.07 823.77 -0.30

ANITEC 7 BM 161 42 ̊06’29” 075 ̊54’51” lower 33 135 822.93 823.37 0.44

USGS Well I BM 153 42 ̊06’25” 075 ̊54’50” lower 34 135 823.28 824.13 0.85

USGS Bm 112 BM 145 42 ̊06’15” 075 ̊54’45” upper 39 137 826.35 826.68 0.33

USGS Well J 6" BM 156 42 ̊06’27” 075 ̊54’47” lower 34 137 826.10 826.15 0.05

USGS Well J2 1/2” BM 597 42 ̊06’27” 075 ̊54’47” upper 34 137 825.89 826.88 0.99

USGS Bm 107 BM 171 42 ̊06’31” 075 ̊53’47” lower 35 147 830.77 832.48 1.71

USGS Bm 100 BM 100 42 ̊06’46” 075 ̊53’12” upper 29 151 839.45 841.11 1.66

USGS Bm 106 BM 140 42 ̊06’09” 075 ̊52’12” lower 46-7 156 840.00 834.29 -5.71

Well owner and

number or name1

USGS2

local 

number

Location

Model 

layer

Model cell Water-level altitude

Difference2

Latitude Longitude Row Column Observed Simulated (feet)

Table 3. (continued) Observed and simulated steady-state water levels for April 7-10, 1981, in Susquehanna River valley 

aquifer system 

Simulated Hydrogeologic System
16 Simulation of a Valley-Fill Aquifer System to Delineate Flow Paths, Contributing Areas, and Traveltime to 

Wellfields in Southwestern Broome County, New York

Pumpage is by far the largest item in the simulated 

water budget and represents 67 percent of the total 

discharge. Discharge from the aquifer to the 

Susquehanna and Chenango Rivers almost equals 

infiltration from these rivers to the aquifer and 

constitutes 22 percent of the total discharge. Under 

natural conditions (non-pumping), discharge from the 

aquifer to the rivers would be greater since the rivers 

typically act as discharge areas. Discharge from the 

aquifer to tributary streams crossing the valley floor 

represents only 10 percent of the total discharge and 

generally occurs near the major rivers.

Table 4. Simulated steady-state ground-water budget 

under average conditions of April 1981 for valley-fill 

aquifer system of the Susquehanna River, southwestern 

Broome County, N.Y.

[Mgal/d, million gallons per day; ft3/s, cubic feet per second]

PARTICLE TRACKING

Delineation of the contributing areas of a supply 

well requires identification of the surface and 

subsurface areas from which water flows to that well. 

The common methods of delineating wellheadprotection-areas, such as use of arbitrarily fixed radii 

or calculated fixed radii, simplified shapes, on 

analytical methods (U.S.E.P.A., 1987; Risser and 

Maddon, 1994) cannot adequately reflect the 

complexities of the Susquehanna River valley aquifer 

system. Analytical methods do not accurately account 

for partial penetration of the aquifer by the stream and 

rivers, nor of flow through confined aquifers. 

Therefore, the numerical ground-water flow model 

modified from Randall (1986), updated with the 

Stream Package (Prudic, 1989) and coupled with the 

particle-tracking computer program MODPATH 

(Pollock, 1994), was used to delineate contributing 

areas for supply wells in the study area. In addition, 

the graphics capability of MODPATH was used to 

delineate flow paths and traveltime along the flow 

paths. This visual information helped to define the 

three-dimensional movement of ground water in this 

aquifer system.

Methods

Flow paths generated by MODPATH are 

determined by velocity components computed from 

the head and intercell flow rates of the calibrated 

steady-state flow model. Each directional velocity 

component is assumed to vary linearly within each 

model cell. The position of a particle along a flow path 

can be estimated from this velocity, and its traveltime 

within each cell can be calculated. Starting locations 

of the particles can be specified, and the particles can 

be tracked either forward to discharge areas or 

backward to recharge areas.

Applying particle-tracking analysis to the steadystate ground-water model requires values for the 

altitude of the top and bottom of (1) the confining unit 

in cells in which it is present and (2) the lower model 

layer. These altitudes were not required for 

computation of ground-water levels or flows by 

MODFLOW because altitudes for the confining unit 

and lower model layer were not explicitly specified. 

The exchange of water from the upper to the lower 

model layer is controlled by the vertical hydraulic 

conductivity of a quasi-three-dimensional confining 

unit. In the lower model layer, transmissivity is 

specified; therefore, the altitudes of the top and bottom 

of the aquifer are not required. The altitude of the 

bottom of the lower model layer is equivalent to the 

bedrock surface altitude (fig. 5A) as estimated from 

well logs throughout the valley. The altitude of the top 

of the lower layer was based on well logs and the 

vertical hydraulic conductivity values. The confining 

unit was assumed to be absent in areas of high vertical 

hydraulic conductivity, and the altitude of the top of 

lower layer was equal to the bottom of the upper layer. 

The confining unit increases in thickness as the 

vertical hydraulic conductivity decreases. The 

thickness of the lower aquifer in the model is shown in 

figure 5B.

Analysis

Particle-tracking analysis of ground-water flow to 

each municipal and industrial supply well entailed (1) 

Source

Rate Percent of 

Mgal/d ft total 3/s

Recharge to aquifer from:

Direct infiltration of precipitation 13.68 21.17 35.3

Unchanneled uplands 4.32 6.68 11.1

Susquehanna and Chenango Rivers 11.05 17.09 28.5

Tributary streams 9.72 15.04 25.1

TOTAL 38.77 59.98 100.0

Discharge from aquifer to:

Supply wells 26.09 40.37 67.3

Susquehanna and Chenango Rivers 8.62 13.34 22.3

Tributary streams 4.04 6.26 10.4

TOTAL 38.76 59.97 100.0
17Figure 5A. Map of model area showing extent of lower aquifer and altitude of bedrock-surface.

Simulated Hydrogeologic System

42o05'00"

42o07'30"

76o 05' 00" 76o 02' 30" 76o 00' 00"

SUSQUEHANNA RIVER

700

700

700

700 

600

800 800

800

NANTICOKE CREEK 

0

0

2

2 KILOMETERS

MILES

EXPLANATION

Model boundary

Lower aquifer

700 Bedrock contour -- shows altitude of bedrock surface

contour interval is 50 feet. Datum is sea level

River or creek

Direction of stream flow

Base from US Geological Survey, 1974, 1:500,000

75o 57' 30" 75o 
18 Simulation of a Valley-Fill Aquifer System to Delineate Flow Paths, Contributing Areas, and Traveltime to 

Wellfields in Southwestern Broome County, New York

50

50

50

50

50

50

50

50

50

50

50

50

100

100

100

100

100

100

100

100

10

100

150

150

200

0

0 2

2

KILOMETERS

MILES

EXPLANATION

Model boundary

Lower aquifer 

Thickness contour -- line of equal aquifer thicknesscontour interval is 50 feet

Base from US Geological Survey, 1974, 1:500,000

42o07'30"

42o05'00"

76o 05' 00" 76o 02' 30" 76o 00' 00" 75o 57' 30" 75

Figure 5B. Map of model area showing thickness and extent of lower aquifer.
19

delineation of the ground-water-contributing area of 

each well, (2) plotting the flow paths from areas of 

recharge to the supply wells, and (3) calculation of 

distances that particles would travel along flow paths 

in 3 years.

Contributing Areas

Delineation of ground-water contributing areas for 

the wells entailed placing an equal number of fluid 

particles on the upper face of each cell in the upper 

model layer and tracking the particles forward 

movement in response to the gradient toward 

discharge areas or wells. The contributing area of a 

given well is defined as the area that encompasses the 

starting locations of particles that travel to that well. 

Contributing areas for the 24 industrial and municipal 

supply wells within the valley-fill aquifer system of 

the Susquehanna River, as indicated by simulation of 

April 1981 steady-state conditions, are shown in 

figure 6.

Delineation of contributing areas required 

interpretation because some model cells were 

converted into no-flow cell by the iterative solution 

process and were thereby excluded from the analysis. 

In a MODFLOW simulation, if the head in a given cell 

falls below the bottom of a cell in which transmissivity 

is a function of saturated thickness, then flow within 

that cell ceases, and the cell is considered dry. Flow 

paths within “dry” cells cannot be computed in a 

MODPATH analysis. In reality, areal recharge can pass 

through the area represented by the cell along a 

vertical path to the lower model layer. In this analysis, 

flow in that cell became “dry” was considered to be 

part of the contributing area of the adjacent active cell 

identified in the MODPATH analysis.

The contributing areas delineated from the 

MODPATH analyses are affected by “weak internal 

sinks”, which are specified-flux or head-dependent 

discharge cells that do not capture all flow that passes 

into them because the model discretization is too 

coarse. Weak internal sinks in the model include some 

cells with supply wells and gaining streams. For 

example, a simulated well that pumps only a part of 

the water that flows into that cell would be a weak 

internal sink. Strong internal sinks, by contrast, 

capture all flow that passes into the model cell. The 

MODPATH analysis cannot determine whether a fluid 

particle that enters a cell that is specified as a weak 

sink will pass through the cell or will stop within the 

cell (Pollock, 1999).

The majority of weak sinks in the model area, 

were associated with river or stream cells in which the 

flow into a cell exceeded the flow discharged to the 

stream. In this situation, particles that enter the cell do 

not terminate at the weak stream sink, but rather pass 

through the cell to a nearby production well. Thus, a 

MODPATH analysis that uses only strong sinks will 

result in a minimum contributing area, whereas one 

that uses only weak sinks will yield a maximum 

contributing area. In some areas of the model, the 

designation of a cell as either a weak or strong sink 

does not greatly affect the dimensions of the 

contributing area (Pollock, 1999). In this study, both 

the maximum and minimum contributing areas 

(corresponding to weak and strong sinks, respectively) 

were delineated. The maximum contributing areas for 

weak sinks and minimum contributing areas for strong 

sinks are shown on figures 6A and 6B. The shapes of 

the contributing areas are irregular and are strongly 

affected by local hydrogeologic features and pumping 

rates of nearby supply wells. With either type of sink 

most of the valley floor to contributes flow to the 24 

supply wells. In general the strong-sink option causes 

the Susquehanna River to alter the shape of most of the 

contributing areas whereas the weak sink option 

produces a larger total contributing area. Many of the 

wells with high pumping rates have extensive 

contributing areas that reach to the valley walls, where 

unchanneled upland flow recharges the system. With 

either option the contributing area commonly extends 

beyond the model boundaries into the upland area.

Flow Paths

Whereas forward particle-tracking is a useful 

method for delineation of contributing areas, backward 

particle tracking can be used to delineate specific flow 

paths of particles that reach supply wells. Backward 

particle-tracking flow path analyses also help depict 

the system’s three-dimensional character which cannot 

be discerned from simulated water levels alone. 

Delineating the flow paths to production wells entails 

placing fluid particles at the faces or center of a model 

cell containing a production well and tracking the 

particles backward toward their point of origin.

The flow paths for particles placed at the industrial 

and municipal supply wells and tracked backward to 

their point of recharge are shown in figure 7 (upper 

model layer) and figure 8 (lower model layer). In 

MODPATH simulations, the movement of particles 

through the confining unit is assumed to be vertical. In 

Simulated Hydrogeologic System
20 Simulation of a Valley-Fill Aquifer System to Delineate Flow Paths, Contributing Areas, and Traveltime to 

Wellfields in Southwestern Broome County, New York

this study, internal sinks were specified as strong 

sinks. The plotted flow paths in figure 7 show particles 

during their travel in the upper model layer. These 

particles have been tracked backward from a specified 

production well in the upper model layer or from 

lower model layer below to their place of origin such 

as the valley floor, contributing upland areas, rivers, or 

tributary streams. Likewise, plotted flow path in figure 

8 show particles while traveling through the lower 

model layer. In most cases these particles have been 

tracked backward from a specified supply well 

screened in the lower model layer and appear to “end” 

where they enter the lower model layer, either directly 

or through the confining layer above. The flow paths 

in both model layers (figures 7 and 8) indicate that 

particles travel long, convoluted paths from their 

source of recharge to supply wells. The longest paths 

generally originate at valley sides where the aquifer 

systems receives recharge from unchanneled upland 

areas. Long flow paths also tend to be associated with 

large withdrawal rates. Particles rapidly enter the 

lower model layer in places where the confining layer 

is highly permeable or absent and travel directly to a 

supply well. In certain localities where the hydraulic 

connection between the upper and lower layers is 

decoupled particles in the lower model layer are able 

to flow in a direction opposite that of the stream or 

river in the upper model layer. The shortest flow paths 

are those where recharge originates at land surface 

near a well, or where the well induces infiltration from 

a nearby stream or river. Note that the spacing of flow 

paths around supply wells in figures 7 and 8 is 

arbitrary, and the rate of ground-water flow between 

any two adjacent flow paths varies. Clusters of many 

flow paths, therefore, does not necessarily indicate a 

high rate of ground-water flow.

Traveltime

MODPATH also can be used to estimate the 

velocity at which fluid particles travel along a defined 

flow path and thereby indicate the distance traveled in 

a given time period. Traveltimes are useful for 

evaluating the advective component of transport of 

conservative (non-reactive) constituents and, thus, can 

be used in the design of monitoring-well networks for 

aquifer protection and remediation.

The simulated flow paths of particles from wells 

to the in point of recharge were analyzed to obtain he 

distances traveled in a 3-year period. Particles were 

placed at the center of model cells containing supply 

wells and were tracked backwards for 3 years toward 

their source of recharge. The 3-year period was chosen 

because it to clearly displays the speed at which water 

particles travel to supply wells in this valley-fill 

aquifer system.

The velocity of ground-water flow is a function of 

flow and the porosity of the aquifer material, as given 

by the following equation:

,

where v = the velocity of the particle, Q = flow and n = 

the porosity, and A is the area through which the flow 

passes (Pollock, 1989). Flow rates were calculated 

from the results of the recalibrated ground-water flow 

simulation and values of porosity were obtained from 

Heath (1983) and Driscoll (1986).

Distance traveled along a flow path in a given time 

span is inversely proportional to the porosity; 

therefore, particles would travel twice as far along 

flowpaths if the porosity of aquifer material were 

reduced by one-half. The sensitivity of flowpath length 

to differing values of effective porosity is illustrated in 

figures 9A and 9B which depicts the flow paths in the 

upper and lower model layers, respectively, for a 

municipal supply well, (Endicott 32, Ranney well, Bm 

50, figures 1 and 3A). Set of low, medium, and high 

porosity values were used in each MODPATH 

simulation. These are listed in table 5. Differences in 

length of the 3-year flow paths are more pronounced in 

the lower layer than in the upper layer, presumably 

because most flow paths in the upper layer reach the 

major source of recharge, the Susquehanna River, 

within 3 years. The 3-year travel distances along flow 

paths to municipal and industrial supply wells as 

calculated from the medium porosity values (table 5), 

are shown in figure 7 for the upper model layer and 

figure 8 for the lower model layer. The shortest flow 

paths originate at the Susquehanna River, which 

provides recharge by induced infiltration and the 

longest originate in recharge areas at land surface or at 

the valley walls where unchanneled runoff from the 

uplands enters the aquifer system. Most flow paths are 

not longer than 4,000 ft. The differences among flowpath length resulting from porosity differences in the 

v Q

An = ------
Simulated Hydrogeologic System 21

42û

05'

42û

07'

30"

42û 05' 75û 52' 30" 76û 07' 30" 76û

76û 07' 30" 42û 07' 30" 76û 75û 52' 30"

Base from U.S. Geological Survey, 7.5-minute topographic quadrangles, 1:24,000

Apalachin, 1969; Binghamton East, 1968; Binghamton West, 1968; Castle Creek,

1968; Chenango Forks, 1968; Endicott, 1969; Maine, 1969

1

1 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100 105 110 115 120 125 130 135 140 145 150 155 157

1 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100 105 110 115 120 125 130 135 140 145 150 155 157

5

10

15

20

25

30

35

40

45

50

55

60

1

5

10

15

20

25

30

35

40

45

50

55

60

MODEL GRID BOUNDARY

CRESTVIEW 1

.

.

.CRESTVIEW 2

CRESTVIEW 3

"CRESTVIEW 1"

"CRESTVIEW 2"

"CRESTVIEW 3"

"ENDICOTT 32"

"CASTLE GARDENS"

.

.

.

. .

.

. .

. .

.

.

CASTLE GARDENS

"ENDICOTT 32"

ENDICOTT 32

"ENDICOTT 32"

"ENDICOTT 5"

VESTAL 1-2

VESTAL 1-1

"VESTAL 1-1"

"VESTAL 1-1"

ENDICOTT 5

ENDICOTT 28

"ENDICOTT 28" "ENDICOTT 5"

IBM SUPPLY WELL 5

"IBM SUPPLY WELL 5"

ENDICOTT 30

"VESTAL 4-2"

"VESTAL 4-3"

VESTAL 4-2

VESTAL 4-3

.VESTAL 4-4

.

.

.

"VESTAL 4-4"

"VESTAL4-3"

IBM

COUNTRY CLUB

JOHNSON CITY 2-3

GENERAL ELECTRIC

"GENERAL

ELECTRIC"

JOHNSON CITY 7

ANITEC 11

ANITEC 10 . .

.

ANITEC 9

"ANITEC 9"

TITCHENER

TITCHENER

. BROOME GOV'T CENTER

0

0

1/2

1/2 1

1 MILES

KILOMETER

Contour Interval 10 feet

National Geodetic Vertical Datum of 1929

EXPLANATION

. VESTAL 4-4 Municipal or industrial supply well used to simulate April 1981

conditions, identified by well owner's name and number (See

Table 1).

Active model cell boundary, upper aquifer.

Contributing area, strong sink option.

Contributing area, weak sink option. 

"VESTAL 4-4" Quotation marks designate contributing area not in direct contact

with municipal or industrial well.

Figure 6. Contributing areas of supply wells in valley-fill aquifer system in the Susquehanna River valley, in southwestern Broome County, N.Y.
Figure 7. Particle flow paths from supply wells and 3-year travel distances in valley-fill aquifer system for the upper model layer of the Susquehanna River River valley in southwestern Broome County, N.Y.

22 Simulation of a Valley-Fill Aquifer System to Delineate Flow Paths, Contributing Areas, and Traveltime to Wellfields in Southwestern Broome County, New York 

42û

05'

42û

07'

30"

42û 05' 75û 52' 30" 76û 07' 30" 76û

76û 07' 30" 42û 07' 30" 76û 75û 52' 30"

Base from US. Geological Survey, 7.5-minute topographic quadrangles, 1:24,000

Appalachian, 1969; Binghamton East, 1968; Binghamton West, 1968; Castle Creek,

1968; Chenango Forks, 1968; Endicott, 1969; Maine, 1969

1

1 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100 105 110 115 120 125 130 135 140 145 150 155 157

1 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100 105 110 115 120 125 130 135 140 145 150 155 157

5

10

15

20

25

30

35

40

45

50

55

60

1

5

10

15

20

25

30

35

40

45

50

55

60

EXPLANATION

Active model cell boundary, upper aquifer.

Municipal or industrial supply well used to simulate April 1981

condition, identified by well owner's name and number.

(See Table 1)

.

ENDICOTT 30

Backward tracked flow path and 3-year travel distance along

flow path from supply well. 3 year

travel time

a a

"ENDICOTT 32" Quotation marks designate flow paths for supply wells 

not located in upper aquifer. (See Table 1)

Model simulated stream cell.

Contour Interval 10 feet

National Geodetic Vertical Datum of 1929

0

0

1/2

1/2 1 KILOMETER

1 MILE

UPPER AQUIFER UPPER AQUIFER

"ENDICOTT 32"

"VESTAL 1-1"

"VESTAL 1-1"

"ENDICOTT 32"

"CRESTVIEW 1"

"CRESTVIEW 3"

"CRESTVIEW 2"

"CASTLE GARDENS"

"VESTAL 1-2"

"VESTAL 1-2"

"ENDICOTT 5"

"ENDICOTT 5"

"ENDICOTT 28"

"IBM SUPPLY WELL 5"

"ENDICOTT 30"

"VESTAL 4-2"

"VESTAL 4-3"

"VESTAL 4-4"

IBM COUNTRY CLUB

"JOHNSON CITY 2&3"

"JOHNSON CITY 7"

"ANITEC 11"

"ANITEC 9"

"ANITEC 10"

BROOME GOV'T CENTER
Simulated Hydrogeologic System 23

Figure 8. Map showing particle flow paths from supply wells and 3-year travel distances in the valley-fill aquifer system in the lower model layer in the Susquehanna River valley, southwestern Broome County, N.Y.

42û

05'

42û

07'

30"

42û 05' 75û 52' 30" 76û 07' 30" 76û

76û 07' 30" 42û 07' 30" 76û 75û 52' 30"

Base from US. Geological Survey, 7.5-minute topographic quadrangles, 1:24,000

Appalachian, 1969; Binghamton East, 1968; Binghamton West, 1968; Castle Creek,

1968; Chenango Forks, 1968; Endicott, 1969; Maine, 1969

1

1 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100 105 110 115 120 125 130 135 140 145 150 155 157

1 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100 105 110 115 120 125 130 135 140 145 150 155 157

5

10

15

20

25

30

35

40

45

50

55

60

1

5

10

15

20

25

30

35

40

45

50

55

60

"BROOME GOV'T CENTER"

CRESTVIEW 1

CRESTVIEW 2

CRESTVIEW 3

CASTLE GARDENS

ENDICOTT 32

"ENDICOTT 30"

ENDICOTT 28

VESTAL 1-1

VESTAL 4-4

VESTAL 1-2

IBM SUPPLY WELL 5

VESTAL 4-2 JOHNSON CITY 2 & 3

GENERAL ELECTRIC

JOHNSON CITY 7

ANITEC 11

ANITEC 9

ANITEC 10

TITCHENER

ENDICOTT 5

VESTAL 4-3

EXPLANATION

Active model cell boundary, lower aquifer.

Municipal or industrial supply well used to simulate April 1981

condition, identified by well owner's name and number (See

Table 1).

.

VESTAL 4-2

Backward tracked flow path and 3-year travel distance along

flow path from supply well. 3 year

travel time

a a

"ENDICOTT 30" Quotation marks designate identification of flow paths for 

supply wells not located in lower aquifer (See Table 1).

Model simulated stream cell 9 (upper aquifer).

Contour Interval 10 feet

National Geodetic Vertical Datum of 1929

0

0

1/2

1/2 1 KILOMETER

1 MILE

LOWER AQUIFER LOWER AQUIFER
ROUTE 17C

CONRAIL

ROUTE 17

NANTICOKE CRE

E

K

SUSQUEHANNA RIVER

42o

05'

30"

42o

05'

00"

42o

04'

30"

76o 05' 30" 76o 05' 00" 76o 04' 30"

42o

05'

30"

42o

05'

30"

42o

04'

30"

1000

300

FEET

METERS

EXPLANATION

3-year travel distances along flow paths for high porosity values

(40%, 55%, 40% in the upper aquifer, confining unit, and lower aquifer, respectively).

3-year travel distances along flow paths for medium porosity values

(30%, 45%, 30% in the upper aquifer, confining unit, and lower aquifer, respectively.)

3-year travel distances along flow paths for low porosity values

(20%, 35%, 20% in the upper aquifer, confining unit, and lower aquifer, respectively.)

Active model cell boundary, upper aquifer.

Model stream cell

Base from US Geological Survey, 1969, 1:24,000

CONRAIL

ROUTE 17C

ROUTE 17

ENDICOTT 32

CASTLE GARDENS WELL

EXPLANATION

3-year travel distances along flow paths for high porosity values

(40%, 55%, 40% in the upper aquifer, confining unit, and lower aquifer, respectively).

3-year travel distances along flow paths for medium porosity values

(30%, 45%, 30% in the upper aquifer, confining unit, and lower aquifer, respectively.)

3-year travel distances along flow paths for low porosity values

(20%, 35%, 20% in the upper aquifer, confining unit, and lower aquifer, respectively.)

Active model cell boundary, lower aquifer.

Municipal supply well

0

0

1000

300

FEET

METERS

76o 05' 30" 76o 05' 00" 76o 04' 30"

42o

05'

30"

42o

05'

00"

42o

04'

30"

42o

04'

30"

42o

05'

00"

42o

05'

30"

Base from US Geological Survey, 1969, 1:24,000

Figure 9A. Map showing 3-year travel distances along flow paths to municipal supply well Endicott 32 

(Ranney well, Bm 50) at high, medium, and low porosity values, in upper model layer. 

Figure 9B. Map showing 3-year travel distances along flow paths to municipal supply well Endicott 32 

(Ranney well, Bm 50) at high, medium, and low porosity values in lower model layer.

lower layer are large enough that the 3-year travel 

distances shown in figures 7 and 8 should be interpreted 

with caution. Actual measured values of effective porosity 

would decrease uncertainty in the estimated travel 

distances.

Table 5. Ranges in porosity used in model-sensitivity analysis 

for unconsolidated material in valley-fi ll aquifer system in 

Susquehanna River valley, southwestern Broome County, N.Y.

[Data from Heath (1983) and Driscoll (1986). Values are in percent. 

Units are depicted in fig. 4.] 

 Porosity 

Model layer Type of material Low Medium High

Upper sand and gravel 20 30 40

Confining unit silt and clay 35 45 55

Lower sand and gravel 20 30 40

Limitations

Particle tracking is only as accurate as the groundwater flow model to which it is coupled. The model 

used in this study is an approximation of a complex 

aquifer system. The weak- or strong-internal sink question 

that results from the model discretization introduces 

ambiguity into the particle-tracking analysis. Furthermore, 

contributing-area analyses indicate that much of the 

recharge that enters at the valley sides originates from 

the uplands, but the flow paths within the uplands are 

unknown because they are beyond the model boundaries. 

The supply-well-pumpage values used for delineation of 

contributing areas for this study area are based on April 

1981 rates which do not represent current (1999) pumping 

rates. Therefore, caution should be used when applying 

the results of this study to current conditions. Despite 

these limitations, particle tracking is an effective means of 

delineating contributing areas and flow paths to wells, and 

of estimating the travel times along flow paths.

SUMMARY

A previously developed numerical steady-state 

ground-water flow model of a 14-mi reach of the 

Susquehanna River valley that contains 24 supply wells in 

southwestern Broome County, N.Y., was converted into a 

MODFLOW data set and was upgraded with the Stream 

Package of Prudic (1989) and recalibrated. The resulting 

model output was then coupled to the MODPATH 

particle-tracking routine to delineate (1) ground-water 

contributing areas, (2) particle flow paths, and (3) 

distances traveled along those flow paths in 3 years. 

Delineation of the contributing areas entailed placing 

particles on the upper face of all upper model layer 

cells and tracking them forward, and plotting the points 

of origin of those particles that discharge to municipal 

and industrial supply wells. Flow paths were delineation 

entailed placing particles at the center of model cells 

containing a pumping well and tracking the particles 

backward to their source. The 3-year travel distance of 

particles along flow paths ending at production wells, 

based on medium porosity values obtained from the 

literature, did not exceed 4,000 ft.

Results of this investigation indicate that simulated 

flow paths to the 24 supply wells within the valley-fill 

aquifer system are three dimensional, and that the 

contributing areas to these wells together include most of 

the valley floor. The techniques used in this study enabled 

delineation of ground water flow paths that could not be 

predicted by conventional analytical methods.

REFERENCES CITED

Barlow, P.M., 1997, Particle-tracking analysis of 

contributing areas of public-supply wells in simple and 

complex flow systems, Cape Cod, Massachusetts: U.S. 

Geological Survey Water-Supply Paper 2434, 66 p.

Driscoll, F.G., 1986, Groundwater and wells, 2nd Edition: 

St. Paul, Minn., Johnson Division, 1,089 p.

Heath, R.C., 1983, Basic ground-water hydrology: U.S. 

Geological Survey Water-Supply Paper 2220, 84 p.

Holecek, T.J., Randall, A.D., Belli, J.L., and Allen, 

R.V., 1982, Geohydrology of the valley -fill aquifer 

in the Endicott-Johnson City area, Broome County, 

New York: U.S. Geological Survey Open-File Report 

82-268, 5 sheets, 1:24,000 scale.

Hollyday, E.F., 1969, An appraisal of the ground-water 

resources of the Susquehanna River basin in New 

York State: U.S. Geological Survey Open-File Report 

69-128, 52 p.

MacNish, R.D. and Randall, A.D., 1982, Stratified-drift 

aquifers in the Susquehanna River basin, New 

York: New York State Department of Environmental 

Conservation Bulletin 75, 68 p.

McDonald, M.G., and Harbaugh, A.W., 1988, A modular 

three-dimensional finite-difference, ground-water flow 

model: U.S. Geological Survey Techniques of WaterResources Investigations book 6, chapter A1, 586 p.

24 Simulation of a Valley-Fill Aquifer System to Delineate Flow Paths, Contributing Areas, and Traveltime to Wellfields in Southwestern Broome County, New York 
References Cited 25

Pollock, D.W., 1994, User’s guide for MODPATH/MODPATH-PLOT, version 3—A particle-tracking post-processing package for MODFLOW, the U.S. Geological 

Survey finite-difference ground-water flow model: 

U.S. Geological Survey Open-File Report 94-404, 249 

p.

Prudic, D.A., 1989, Documentation of a computer program 

to simulate stream-aquifer relations using a modular, 

finite-difference, ground-water flow model: U.S. Geological Survey Open-File Report 88-729, 113 p.

Randall, A.D., 1972, Records of wells and test borings in 

the Susquehanna River basin, New York: New York 

State Department of Environmental Conservation Bulletin 69, 92 p.

———1977, The Clinton Street-Ballpark aquifer in Binghamton and Johnson City, New York: New York State 

Department of Environmental Conservation Bulletin 

73, 87 p.

——— 1986, Aquifer model of the Susquehanna River valley in Southwestern Broome County, New York: U.S. 

Geological Survey Water-Resources Investigations 

Report 85-4099, 38 p.

Reynolds, R.J., 1987, Hydrogeology of the surficial outwash aquifer at Cortland, Cortland County, New York: 

U.S. Geological Survey Water-Resources Investigations Report 85-4090, 43 p.

Risser, D.W., and Madden, T.M., Jr., 1994, Evaluation of 

methods for delineating areas that contribute water to 

wells completed in valley-fill aquifers in Pennsylvania: 

U.S. Geological Survey Water Resources Investigations Report 92-635, 82 p.

Trescott, P.C., and Larson, S.P., 1976, Documentation of 

finite difference model for simulation of three-dimensional ground-water flow: U.S. Geological Survey 

Open-File Report 76-591, 21 p.

U.S. Environmental Protection Agency, 1987, Guidelines 

for delineation of wellhead protection areas: U.S. Environmental Protection Agency, Office of Ground Water 

Protection, Washington, D.C., June 1987, variously 

paged.

Waller, R.M., and Finch, A.J., 1982, Atlas of eleven selected 

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