Prepared in cooperation with the Town of Dryden and the Tompkins County Planning Department

Geohydrology, Water Quality, and Simulation of 

Groundwater Flow in the Stratified-Drift Aquifer System 

in Virgil Creek and Dryden Lake Valleys, Town of 

Dryden, Tompkins County, New York

Scientific Investigations Report 2013–5070

U.S. Department of the Interior

U.S. Geological Survey
Front cover: Test drilling and aquifer test near Dryden Lake, Town of Dryden, New York. Drilling completed in 2004. Aquifer test, 

January 5, 2005. All photos courtesy Todd MiIller, USGS.

Back cover. Three-dimensional-grid representation of groundwater-flow model of the stratified-drift aquifer system in the Virgil 

Creek and Dryden Lake valleys, Town of Dryden, Tompkins County, New York.
Geohydrology, Water Quality, and 

Simulation of Groundwater Flow in the 

Stratified-Drift Aquifer System in Virgil 

Creek and Dryden Lake Valleys, Town of 

Dryden, Tompkins County, New York

By Todd S. Miller and Edward F. Bugliosi

Prepared in cooperation with the Town of Dryden and the Tompkins County 

Planning Department

Scientific Investigations Report 2013–5070

U.S. Department of the Interior

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

SALLY JEWELL, Secretary

U.S. Geological Survey

Suzette M. Kimball, Acting Director

U.S. Geological Survey, Reston, Virginia: 2013

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as noted in the text. Permission to reproduce copyrighted items must be secured from the copyright owner.

Suggested citation:

Miller, T.S. and Bugliosi, E.F., 2013, Geohydrology, water quality, and simulation of groundwater flow in the stratifieddrift aquifer system in Virgil Creek and Dryden Lake Valleys, Town of Dryden, Tompkins County, New York: U.S. 

Geological Survey Scientific Investigations Report 2013-5070, 104 p., http://pubs.usgs.gov/sir/2013/5070/.
iii

Contents

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

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

Purpose and Scope ..............................................................................................................................4

Data Collection......................................................................................................................................4

Geologic Data...............................................................................................................................4

Well Inventory, Test Drilling, Water-Level Measurements, and Leveling ..........................4

Streamflow Measurements .......................................................................................................4

Seismic-Refraction Surveys ......................................................................................................4

Water Sampling and Analysis....................................................................................................5

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

Geology............................................................................................................................................................5

Glacial History .......................................................................................................................................6

Scouring by Ice ...................................................................................................................................10

Wisconsinan Deposits in the Study Area .......................................................................................20

Southern Part of Study Area....................................................................................................21

Northern Part of Study Area ....................................................................................................21

Geohydrology of the Stratified-Drift Aquifer System.............................................................................24

Aquifer Geometry................................................................................................................................29

Unconfined Aquifers .................................................................................................................29

Confined Aquifers and Confining Units ..................................................................................29

Bedrock .......................................................................................................................................29

Groundwater Recharge .....................................................................................................................29

Unconfined Aquifer ...................................................................................................................33

Confined Aquifers ......................................................................................................................33

Groundwater Discharge ....................................................................................................................35

Municipal Withdrawals ............................................................................................................35

Other Withdrawals ....................................................................................................................37

Groundwater Levels ...........................................................................................................................37

Aquifer Properties...............................................................................................................................41

Aquifer Test at Well TM 981 at the Jay Street Pumping Station........................................41

Specific Capacity Test in Test Well TM 993 Near Dryden Lake .........................................43

Water Quality................................................................................................................................................44

Surface Water.....................................................................................................................................47

Physicochemical Properties....................................................................................................47

Common Inorganic Constituents.............................................................................................47

Nutrients......................................................................................................................................47

Groundwater........................................................................................................................................47

Physicochemical Properties....................................................................................................50

Inorganic Major Ions.................................................................................................................50

Nutrients......................................................................................................................................51

Trace Elements...........................................................................................................................51

Groundwater-Age Dating .........................................................................................................51
iv

Simulation of Groundwater Flow...............................................................................................................58

Model Design.......................................................................................................................................59

Model Grid and Layers..............................................................................................................59

Boundary Conditions.................................................................................................................59

No-Flow Boundaries ........................................................................................................59

Specified-Flux Boundaries..............................................................................................59

Head-Dependent Boundaries.........................................................................................64

Model Calibration................................................................................................................................65

Model Parameters.....................................................................................................................65

Model Fit......................................................................................................................................68

Model Applications.............................................................................................................................74

Groundwater-Flow Directions .................................................................................................75

Areal Extent of the Zones of Groundwater Contribution to the Village of Dryden 

Municipal Production Wells .......................................................................................75

Water Budget .............................................................................................................................81

Model Limitations.......................................................................................................................84

Summary........................................................................................................................................................85

References Cited..........................................................................................................................................86

Appendix 1. Selected Wells in the Stratified-Drift Aquifer System in Virgil Creek and 

Dryden Lake Valleys, Tompkins County, and in Owego Creek Valley, Cortland 

County, New York ...........................................................................................................................91

Figures

1. Map showing locations of 17 unconsolidated aquifer reaches in Tompkins County,

New York ........................................................................................................................................3

2. Map showing physiographic features of New York State and location of Virgil

Creek Valley and Dryden Lake Valley study area in Tompkins County, New York .............6

3. Map showing the boundary of the stratified-drift aquifer system extending across

the Virgil Creek and Owego Creek Basins, Tompkins and Cortland Counties, New

York..................................................................................................................................................7

4. Map showing topographic altitudes, shaded relief, and boundary of stratified-drift

aquifer system study area in the Virgil Creek, Dryden Lake, and Owego Creek

Valleys, Tompkins County, New York .........................................................................................8

5. Chronostratigraphic classification of Pleistocene stades and interstades in

northeastern North America and their effect on the study area..........................................9

6. Map showing surficial geology of Virgil Creek, Dryden Lake, and Owego Creek

Valleys, Tompkins and Cortland Counties, New York............................................................11

7. Map showing altitude of bedrock surface and location of lines of seismic refraction

cross-sections in the study area in the Virgil Creek, Dryden Lake, and Owego Creek

Valleys, Tompkins and Cortland Counties, New York............................................................12

8. Map showing locations of wells and lines of geologic cross-sections, seismic

refraction cross-sections, and a hydrologic cross-section in the study area in the

Virgil Creek, Dryden Lake, and Owego Creek Valleys, Tompkins and Cortland

Counties, New York ....................................................................................................................13

9. Diagram showing construction details of U.S. Geological Survey test wells TM1695,

TM1699, and TM1700 and well log of test well TM1695 at Lake Road near Dryden,

New York ......................................................................................................................................14
v

10. Map and diagram showing A, location of line of seismic refraction cross-section

and B, seismic refraction cross-section A–A′ along Purvis Road, Town of Dryden,

New York, in the southern part of Dryden Lake Valley .........................................................15

11. Diagram showing construction details of U.S. Geological Survey test wells TM 997

and TM 998 at Virgil Creek Dam in the Town of Dryden, New York....................................17

12. Map and diagrams showing A, locations of lines of seismic refraction

cross-sections, test wells TM 997 and TM 998, and streamflow-measurement sites

near the Virgil Creek Dam, Town of Dryden, New York, B, seismic refraction

cross-section B–B′ along the Virgil Creek floodplain, and C, seismic refraction

cross-section C–C′ in the spillway of the Virgil Creek Dam ................................................18

13. Diagram showing longitudinal geologic cross-section A–A′ in the Virgil Creek and

Dryden Lake Valleys, Town of Dryden, New York..................................................................22

14. Diagram showing geologic section B–B′ at the Virgil Creek Dam, Town of Dryden,

New York ......................................................................................................................................25

15. Diagram showing well log and well construction details of U.S. Geological Survey

test well TM 993 at the New York State Department of Environmental Conservation

boat access facility at Dryden Lake, in the Town of Dryden, New York ............................26

16. Diagram showing well log and well construction details of U.S. Geological Survey

test well TM2724, on the Jim Schug trail near Keith Lane Road, Town of Dryden,

New York ......................................................................................................................................27

17. Diagrams showing well logs and well construction details of A, abandoned well

TM 207 and B, production well TM1046 at the South Street pumping station, Village

of Dryden......................................................................................................................................28

18. Diagram showing geohydrology across longitudinal geologic cross-section A–A′ in

the Virgil Creek and Dryden Lake Valleys, Town of Dryden, Tompkins County, and in

headwaters of Owego Creek, Town of Harford, Cortland County, New York ...................30

19. Diagram showing geohydrology across geologic cross-section B–B′ at the Virgil

Creek Dam, Town of Dryden, New York ..................................................................................32

20. Schematic diagram showing sources of recharge to aquifers in A, the northern

part of the study area and B, the southern part of the study area, Tompkins and

Cortland Counties, New York ....................................................................................................34

21. Graph showing monthly withdrawals from Village of Dryden, New York, municipal

production wells, September 1970 through December 2008, and water usage by

Tompkins Cortland Community College, 2006 through 2008. ...............................................36

22. Graph showing annual withdrawals from the Village of Dryden, New York,

municipal production wells from 1970 through 2008.............................................................37

23. Hydrograph of the altitude of the groundwater levels from June 24, 2005, through

May 14, 2008, in observation wells TM1699 and TM1700 at the Lake Road pumping

station, Village of Dryden, New York .......................................................................................39

24. Hydrographs showing altitude of the water level from observation wells A, TM 207

and B, TM 993..............................................................................................................................40

25. Map showing location of wells in which drawdown was measured for the aquifer

test conducted in production well TM 981 in the Village of Dryden, New York,

during June 19–21, 2007.............................................................................................................42

26. Graph showing results of specific capacity test in test well TM 993, 450 feet north

of Dryden Lake, Town of Dryden, New York ...........................................................................44

27. Map showing the location of groundwater and surface-water sampling sites in

Virgil Creek and Dryden Lake Valleys, Town of Dryden, New York ....................................46
vi

28. Piper diagram illustrating variability in major ion composition of groundwater in Virgil 

Creek Valley, Lower Sixmile Creek and Willseyville Creek trough, Upper Sixmile Creek 

and West Branch Owego Creek Valleys, and Upper Buttermilk and Danby Creek

Valleys, Tompkins County, New York .......................................................................................56

29. Schematic diagrams of the model used in the study of the stratified-drift aquifer

system in Virgil Creek and Dryden Lake Valleys, Town of Dryden, Tompkins County,

New York ......................................................................................................................................60

30. Maps showing boundary conditions in groundwater-flow model in stratified-drift

aquifer study area in the Virgil Creek, Dryden Lake, and Owego Creek Valleys,

Tompkins and Cortland Counties, New York: A, Upper confining unit (model layer 1),

B, middle and lower confining units (model layers 3 and 5) and upper, middle, and

lower confined aquifer units (model layers 2, 4, and 6)........................................................61

31. Diagram showing zones of horizontal hydraulic conductivity of the A, upper, B,

middle, and C, lower confined aquifers used in the numerical simulation of

groundwater flow in the stratified-drift aquifer system in Virgil Creek and Dryden

Lake Valleys, Tompkins County, New York..............................................................................69

32. Graph showing composite sensitivity of groundwater-flow model output to changes

in input parameters, stratified-drift aquifer system in the Virgil Creek, Dryden Lake,

and Owego Creek Valleys, Tompkins and Cortland Counties, New York...........................70

33. Plots showing groundwater-level residuals for the numerical groundwater-flow

model of the stratified-drift aquifer system in Virgil Creek and Dryden Lake Valleys,

Town of Dryden, Tompkins County, New York........................................................................71

34. Plots showing residuals for simulated heads in the numerical groundwater-flow 

model, showing relation between A,simulated and observed values and 

B, simulated values and residuals ...........................................................................................72

35. Maps showing distribution of hydraulic head computed by steady-state simulation

for the stratified-drift aquifer system in Virgil Creek and Dryden Lake Valleys in

Tompkins County and the headwaters of Owego Creek Valley in Cortland County,

New York ......................................................................................................................................76

36. Diagram showing groundwater flow in a longitudinal hydrologic cross-section A–A’

 in the central part of the numerical groundwater model study area, Town of

Dryden, Tompkins County, and Town of Harford, Cortland County, New York..................79

37. Map showing the estimated areal extent of the zones of groundwater contribution

and time of travel to Village of Dryden production wells TM 202, which is finished in

the upper confined aquifer (model layer 2), and TM 981, which is finished in the

middle confined aquifer (model layer 4), in the Dryden Lake and Virgil Creek

Valleys, Tompkins County, New York .......................................................................................80

38. Map showing the estimated areal extent of the zone of groundwater contribution 

and time of travel to Village of Dryden production well TM1046, which is finished 

in the lower confined aquifer (model layer 6), in the Dryden Lake and Virgil Creek 

Valleys, Tompkins County, New York .......................................................................................82

39. Map showing the estimated areal extent of the zones of groundwater contribution

and time of travel to Village of Dryden production well TM1046, which is finished in

the lower confined aquifer (model layer 6), and to a hypothetical well at test-well

site TM2724 near Keith Lane, also finished in the lower confined aquifer, in the

Dryden Lake and Virgil Creek Valleys, Tompkins County, New York ..................................83
vii

Tables

1. Estimated groundwater withdrawals from users outside the Village of Dryden

municipal supply system and within the Virgil Creek and Dryden Lake valley-fill

aquifer system study area, 2008. ............................................................................................38

2. Estimated hydraulic values from analyses of aquifer-test data of partially

penetrating muncipal well TM 981 at the Jay Street pumping station, Village of

Dryden ..........................................................................................................................................43

3. Historic well tests from water-supply investigations for the Village of Dryden...............45

4. Physical properties and concentrations of inorganic major ions, trace metals, and

nutrients in surface-water samples from Virgil Creek, inlet and outlet to Dryden

Lake, and several tributaries, Town of Dryden, New York, 2003–05...................................48

5. Summary statistics for pH and concentrations of major chemical constituents in

surface-water and groundwater samples collected in the Virgil Creek and Dryden

Lake valleys, Town of Dryden, New York, 2003–09................................................................50

6. Physical properties and concentrations of inorganic major ions, nutrients, and

tritium in groundwater samples from confined aquifers in the Virgil Creek and

Dryden Lake Valleys, Town of Dryden, New York, 2003–09 .................................................52

7. Concentrations of trace metals in groundwater samples from confined aquifers in

the Virgil Creek and Dryden Lake Valleys, Town of Dryden, New York, 2003–09 .............54

8. Summary statistics for concentrations of trace elements in groundwater samples

collected in the Virgil Creek and Dryden Lake valleys, Town of Dryden, New York,

2003–09 .........................................................................................................................................55

9. Apparent groundwater ages from groundwater samples collected from five wells

that tap the confined stratified-drift aquifers in the Virgil Creek and Dryden Lake

valleys, Town of Dryden, Tompkins County, New York .........................................................57

10. Numbers of parameters that represent the stratified-drift aquifer system in the

Virgil Creek and Dryden Lake valleys, Tompkins County, New York, as estimated

and fixed in the nonlinear, parameter-estimation inverse model .......................................66

11. Parameter values estimated for the groundwater-flow model of the stratified-drift

aquifer system in the Virgil Creek and Dryden Lake Valleys, Tompkins County, New

York................................................................................................................................................67

12. Measured and simulated water levels in wells open to the stratified-drift aquifers

in the Virgil Creek, Dryden Lake, and Owego Creek Valleys, Towns of Dryden and

Harford, Tompkins and Cortland Counties, New York...........................................................73

13. Simulated water budget for the stratified-drift aquifer system in the Virgil Creek

and Dryden Lake Valleys, Town of Dryden, Tompkins County, and in part of the

Owego Creek Valley, Town of Harford, Cortland County, New York...................................84
viii

Conversion Factors and Datum

Multiply By To obtain

Length

inch (in.) 2.54 centimeter (cm)

inch (in.) 25.4 millimeter (mm)

foot (ft) 0.3048 meter (m)

mile (mi) 1.609 kilometer (km)

Area

square foot (ft2

) 0.09290 square meter (m2)

square inch (in2

) 6.452 square centimeter (cm2)

square mile (mi2

) 2.590 square kilometer (km2) 

Volume

gallon (gal) 3.785 liter (L) 

gallon (gal) 0.003785 cubic meter (m3

) 

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

)

cubic foot (ft3

) 0.02832 cubic meter (m3) 

Flow rate

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

foot per year (ft/yr) 0.3048 meter per year (m/yr)

cubic foot per second (ft3

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

cubic foot per second per square mile 

[(ft3

/s)/mi2]

0.01093 cubic meter per second per square 

kilometer [(m3/s)/km2]

cubic foot per day (ft3

/d) 0.02832 cubic meter per day (m3/d)

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

gallon per day (gal/d) 0.003785 cubic meter per day (m3

/d)

million gallons per day (Mgal/d) 0.04381 cubic meter per second (m3

/s)

million gallons per day per square 

mile [(Mgal/d)/mi2

]

1,461 cubic meter per day per square 

kilometer [(m3/d)/km2]

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

Radioactivity

picocurie per liter (pCi/L) 0.037 becquerel per liter (Bq/L) 

Specific capacity

gallon per minute per foot [(gal/min)/

ft)]

0.2070 liter per second per meter [(L/s)/m]

Hydraulic conductivity

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

Hydraulic gradient

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

Transmissivity*

foot squared per day (ft2

/d) 0.09290 meter squared per day (m2/d) 
ix

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

(NAVD 88) where light detection and ranging (lidar) and Digital Elevation Model (DEM) data 

were used, and to the National Geodetic Vertical Datum of 1929 (NGVD 29) elsewhere.

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

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

Transmissivity: The standard unit for transmissivity is cubic foot per day per square foot times 

foot of aquifer thickness [(ft3/d)/ft2]ft. In this report, the mathematically reduced form, foot 

squared per day (ft2/d), is used for convenience.

Abbreviations

BP before present

CFC chlorofluorocarbons

GMS Groundwater Modeling System

HA health advisory

H/V horizontal-to-vertical

LiDAR light detection and ranging

MCL maximum contaminant level

NWIS National Water Information System

NWQL National Water Quality Laboratory

NYSDEC New York State Department of Environmental Conservation

SMCL secondary maximum contaminant level

3

H tritium

TU tritium unit

USEPA U.S. Environmental Protection Agency

USGS U.S. Geological Survey
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Geohydrology, Water Quality, and Simulation of 

Groundwater Flow in the Stratified-Drift Aquifer 

System in Virgil Creek and Dryden Lake Valleys, 

Town of Dryden, Tompkins County, New York

By Todd S. Miller and Edward F. Bugliosi

Abstract

In 2002, the U.S. Geological Survey, in cooperation with 

the Tompkins County Planning Department and the Town 

of Dryden, New York, began a study of the stratified-drift 

aquifer system in the Virgil Creek and Dryden Lake Valleys 

in the Town of Dryden, Tompkins County. The study provided 

geohydrologic data needed by the town and county to develop 

a strategy to manage and protect their water resources. In this 

study area, three extensive confined sand and gravel aquifers 

(the upper, middle, and lower confined aquifers) compose 

the stratified-drift aquifer system. The Dryden Lake Valley 

is a glaciated valley oriented parallel to the direction of ice 

movement. Erosion by ice extensively widened and deepened 

the valley, truncated bedrock hillsides, and formed a nearly 

straight, U-shaped bedrock trough. The maximum thickness of 

the valley fill in the central part of the valley is about 400 feet 

(ft). The Virgil Creek Valley in the east part of the study area 

underwent less severe erosion by ice than the Dryden Lake 

Valley, and hence, it has a bedrock floor that is several hundred 

feet higher in altitude than that in the Dryden Lake Valley.

The sources and amounts of recharge were difficult 

to identify in most areas because the confined aquifers are 

overlain by confining units. However, in the vicinity of the 

Virgil Creek Dam, the upper confined aquifer crops out at 

land surface in the floodplain of a gorge eroded by Virgil 

Creek, and this is where the aquifer receives large amounts of 

recharge from precipitation that directly falls over the aquifer 

and from seepage losses from Virgil Creek. The results of 

streamflow measurements made in Virgil Creek where it flows 

through the gorge indicated that the stream lost 1.2 cubic feet 

per second (ft3

/s) or 0.78 million gallons per day (Mgal/d) of 

water in the reach extending from 220 ft downstream from the 

dam to 1,200 ft upstream from the dam. In the southern part 

of the study area, large amounts of recharge also replenish the 

stratified-drift aquifers at the Valley Heads Moraine, which 

consists of heterogeneous sediments including coarse-grained 

outwash and kame sediments, as well as zones containing till 

with a fine-grained matrix. In the southern part of the study 

area, the confining units are thin and likely to be discontinuous 

in some places, resulting in windows of permeable sediment, 

which can more readily transmit recharge from precipitation 

and from tributaries that lose water as they flow over the 

valley floor. In contrast, in the northern part of the study 

area, the confining units are thick, continuous, and comprise 

homogeneous fine-grained sediments that more effectively 

confine the aquifers than in the southern part of the study area.

Most groundwater in the northern part of the study area 

discharges to the Village of Dryden municipal production 

wells, to the outlet to Dryden Lake, to Virgil Creek, and as 

groundwater underflow that exits the northern boundary 

of the study area. Most northward-flowing groundwater in 

the southern part of the study area discharges to Dryden 

Lake, to the inlet to Dryden Lake, and to homeowner, 

nonmunicipal community (a mobile home community and 

several apartments), and commercial wells. Most of this 

pumped water is returned to the groundwater system via septic 

systems. Most southward-flowing groundwater in the southern 

part of the study area discharges to the headwaters of Owego 

Creek and to agricultural wells; some flow also exits the 

southern boundary of the study area as groundwater underflow.

The largest user of groundwater in the study area is the 

Village of Dryden. Water use in the village has approximately 

tripled between the early 1970s when withdrawals ranged 

between 18 and 30 million gallons per year (Mgal/yr) 

and from 2000 through 2008 when withdrawals ranged 

between 75 and 85 Mgal/yr. The estimated groundwater 

use by homeowners, nonmunicipal communities, and 

small commercial facilities outside the area supplied by the 

Village of Dryden municipal wells is estimated to be about 

18.4 Mgal/yr. Most of this pumped water is returned to the 

groundwater system via septic systems.

For this investigation, an aquifer test was conducted at 

the Village of Dryden production well TM 981 (finished in 

the middle confined aquifer at a well depth of 72 ft) at the 
2 Geohydrology, Water Quality, and Simulation of Groundwater Flow, Town of Dryden, Tompkins County, New York

Jay Street pumping station during June 19–21, 2007. The 

aquifer test consisted of pumping production well TM 981 at 

104 gallons per minute over a 24-hour period. The drawdown 

in well TM 981 at the end of 24 hours of pumping was 19.2 ft. 

Results of the aquifer-test analysis for a partially penetrating 

well in a confined aquifer indicated that the transmissivity 

was 1,560 feet squared per day, and the horizontal hydraulic 

conductivity was 87 feet per day, based on a saturated 

thickness of 18 ft.

During 2003–5, 14 surface-water samples were 

collected at 8 sites, including Virgil Creek, Dryden Lake 

outlet, and several tributaries. During 2003 through 2009, 

eight groundwater samples were collected from eight 

wells, including three municipal production wells, two test 

wells, and three domestic wells. Calcium dominates the 

cation composition, and bicarbonate dominates the anion 

composition in most groundwater and surface-water samples. 

None of the common inorganic constituents collected 

exceeded any Federal or State water-quality standards.

Results from a three-dimensional, finite-difference 

groundwater-flow model were used to compute a water budget 

and to estimate the areal extent of the zone of groundwater 

contribution to the Village of Dryden municipal production 

wells. The model-computed water budget indicated that 

the sources of recharge to the confined aquifer system are 

precipitation that falls directly on the valley-fill sediments 

(40 percent of total recharge), stream leakage (35.5 percent), 

seepage from wetlands and ponds (12 percent), unchanneled 

runoff and groundwater inflow from the uplands (8.5 percent), 

and groundwater underflow into the eastern end of the model 

area (4 percent). Most groundwater discharges to surfacewater bodies, including Dryden Lake (33 percent), streams 

(33 percent), and wetlands and ponds (10 percent of the total). 

In addition, some groundwater discharges as underflow out of 

the southern and northern ends of the model area (15 percent), 

to simulated pumping wells (4.5 percent), and to drains that 

represent seepage from the bluffs exposed in the gorge in the 

vicinity of the Virgil Creek Dam (4.5 percent).

The areal extents of the zones of groundwater 

contribution for Village of Dryden municipal production 

wells TM 202 (Lake Road pump station, finished in the upper 

confined aquifer) and TM 981 (Jay Street pump station, 

finished in the middle confined aquifer) are 0.5 square mile 

(mi2 ) and 0.9 mi2

, respectively. The areal extent of the zone 

of contribution to production well TM 202 extends 2.2 miles 

(mi)southeast into the Virgil Creek Valley, whereas production 

well TM 981 extends 3.8 mi south in the Dryden Lake Valley. 

The areal extent of the zone of contribution to production 

well TM1046 (South Street pump station) is 1.4 mi2

 and 

extends 2.4 mi into Dryden Lake Valley and 0.5 mi into Virgil 

Creek Valley.

Introduction

In 2000, the U.S. Geological Survey (USGS) 

published a reconnaissance-level map depicting the extent 

of unconsolidated aquifers in Tompkins County, New York 

(Miller, 2000b). During 2000 through 2002, the USGS and 

the Tompkins County Planning Department used the map to 

develop a plan to study the unconsolidated aquifers in more 

detail. The objectives of the more detailed aquifer studies 

were to provide geohydrologic data for planners to develop 

a strategy to manage and protect their water resources. An 

area with 17 valleys that contain unconsolidated aquifers was 

outlined, and a program was developed to study these aquifers 

over a 20-year period. The extents of these unconsolidated 

aquifers were defined mostly on natural hydrologic 

boundaries, but in some cases political boundaries were used 

as well. In order to have study areas of manageable size, the 

aquifer reaches were limited in length to about 3 to 10 miles 

(mi) each. Virgil Creek Valley (fig. 1) was one of the locations 

identified on the list of major aquifers to be studied. Where 

there are multiple aquifers in a valley, such as in the Virgil 

Creek Valley, the aquifers are referred to as a stratified-drift 

aquifer system.

In 2002, the USGS, in cooperation with the Tompkins 

County Planning Department and the Town of Dryden, began 

a study of the stratified-drift aquifer system in the Virgil Creek 

and Dryden Lake Valleys in the Town of Dryden, Tompkins 

County, and in part of the Owego Creek Valley in the Town 

of Harford, Cortland County, N.Y. (fig. 1). The Virgil Creek, 

Dryden Lake, and Owego Creek Valleys were selected 

to be studied because this area is undergoing increasing 

development and the aquifers underlying the valleys are the 

most used in the counties. The purpose of this study was to 

characterize the geohydrology of the stratified-drift aquifer 

system in Virgil Creek and Dryden Lake Valleys and provide 

the geohydrologic data needed by the Town of Dryden and 

Tompkins County to develop a strategy to manage and protect 

their water resources. Evaluation, development, and protection 

of these aquifers require information on aquifer framework 

(the three-dimensional extent and distribution of aquifers 

and confining units), sources of recharge, discharge areas, 

hydraulic properties, direction of groundwater flow, and water 

quality. As a result, a numerical groundwater-flow model was 

developed as a tool to help hydrologists and water-resource 

managers understand the relatively complicated flow system 

of the aquifer system. In addition, this study fulfills the 

mission of the USGS to publish and disseminate the Earthscience information needed to understand, to plan the use of, 

and to manage the Nation’s water resources. This study also 

adds to the volume of knowledge the USGS is collecting to 

further understand, plann, and manage the Nation’s water 

resources with a view to conservation and energy uses.
Introduction 3

Figure 1. Locations of 17 unconsolidated aquifer reaches in Tompkins County, New York.

EXPLANATION

Aquifer reaches Aquifer reaches, continued

Cascadilla Creek valley and upland Sixmile 

Creek valley

Enfield Creek valley

Lower Cayuga Inlet valley

Lower Fall Creek valley

Lower Sixmile Creek valley (towns of Dryden

and Ithaca)

Owasco Inlet valley

Pony Hollow valley

Salmon Creek/Myers Point/Locke Creek

Taughannock Creek valley and delta

Upper Buttermilk Creek and Danby Creek valleys

Upper Cayuga Inlet valley

Upper Fall Creek valley

Upper Sixmile Creek and West Branch Owego Creek valleys

Virgil Creek, Dryden Lake, and Owego Creek valleys (this study area)

West Branch Cayuga Inlet and Fish Kill valleys

West Branch Owego Creek valley and tributaries

Lower Sixmile Creek and Willseyville Creek valleys

(town of Caroline)

0 2 4 Miles

0 2 4 Kilometers

76°40' 76°30' 76°20'

42°30'

42°20'

Base from TOPO! 2003 ©National Geographic, scale 1:100,000 Aquifers mapped by T.S. Miller (2000)

TOWN OF 

LANSING

TOWN OF 

GROTON

Town of

Ulysesses

Town of

Eneld

Town of

Ithaca

City of

Ithaca

Town of

Dryden

Town of Harford

Town of

Caroline

Town of

Danby

Town of

Neweld

CAYUGA CO

TOMPKINS CO

TOMPKINS

CORTLAND

TOMPKINS

TIOGA

TOMPKINS

SCHUYLER CHEMUNG

TOMPKINS

SENECA

Study

area

Tompkins 

County

NEW

YORK
4 Geohydrology, Water Quality, and Simulation of Groundwater Flow, Town of Dryden, Tompkins County, New York

Purpose and Scope

This report describes the geohydrology, water quality, 

and simulated groundwater flow in the stratified-drift aquifer 

system in Virgil Creek and Dryden Lake Valleys in Tompkins 

County and a small part of the headwaters in Owego Creek 

Valley in Cortland County. The report describes (1) the 

geology of the study area, including the geologic framework 

of the stratified-drift aquifer system; (2) the groundwater-flow 

system, including water levels, groundwater and surfacewater interaction, direction of groundwater flow, and recharge 

and discharge conditions; (3) the water quality of the study 

area, including concentrations of common inorganic ions and 

nutrients; (4) the age of the groundwater in the study area; and 

(5) the construction, calibration, and interpretation of results 

from a numerical groundwater-flow model. The groundwaterflow model was used as a tool to understand the relatively 

complicated flow system of the aquifer system and to estimate 

the areal extent of the zones of groundwater contribution to 

the existing Village of Dryden municipal supply wells and to 

a hypothetical pumping well at a potential supply-well site. 

Also included are (1) geohydrologic sections; (2) maps and 

diagrams depicting well locations, geology, groundwater 

levels, and direction of groundwater flow; and (3) tables of 

well records and water-quality data.

Data Collection

The USGS collected the following types of information 

for inclusion in this report: geologic data, seismic-refraction 

surveys, well stratigraphic records collected through well 

inventory and test drilling, water-level and streamflow 

measurements, and water-quality data on surface water and 

groundwater. In addition, leveling was done to obtain the 

altitude of measuring points of wells (top of casings) and 

selected sites along streams and standing bodies of water 

(lakes, ponds, and wetlands).

Geologic Data

This report includes geologic mapping that builds on 

and modifies the mapping done by Miller (1993). Geologic 

data were collected by seismic-refraction surveys, field 

reconnaissance, interpretation from topographic maps and 

orthophoto interpretation, and review of available geologic 

reports, soils maps, and well-drilling records.

Well Inventory, Test Drilling, Water-Level 

Measurements, and Leveling

Records from approximately 100 wells (appendix 1) were 

used to determine the geohydrologic characteristics of the 

aquifer system. Sources of well and test-boring data include 

published USGS groundwater studies, the USGS National 

Water Information System (NWIS), files of the New York 

State Department of Environmental Conservation (NYSDEC) 

Water Well Drillers Registration Program, test boring data 

from the New York State Department of Transportation 

(appendix 1), and records from test wells that were drilled 

during this study.

Altitudes of 50 water-level-measuring points, which 

are typically the tops of the well casings, were determined 

to 0.01 foot (ft) using standard surveying techniques. Depths 

to water below the measuring points were then converted to 

altitudes, which were subsequently used in the calibration 

of the numerical groundwater-flow model. The altitudes at 

selected locations of the channel bottoms and water surfaces 

of the streams were also determined to 0.01 ft using standard 

surveying techniques. Elsewhere, altitudes of the land surface 

at wells and channel bottoms and water surfaces of the streams 

were estimated using light detection and ranging (lidar) or 

1:24,000-scale topographic contour maps.

Streamflow Measurements

Streamflow was measured by using a current meter 

in Virgil Creek and tributary streams during collection 

of stream water-quality samples during 2003 and 2004. 

Streamflow measuring techniques are described by Rantz and 

others (1982).

A streamgage (USGS station number 0423368620) was 

installed on Virgil Creek at State Highway Route 13 in Dryden 

on October 18, 2002, and was maintained by the USGS New 

York Water Science Center, Ithaca Program Office. The 

drainage area of the streamgage is 29.7 square miles (mi2

). 

Stage and discharge data were collected from October 18, 

2002, through September 30, 2004. In addition to these data, 

eight water-quality samples were collected during base-flow 

conditions and analyzed for selected chemical constituents 

(see Water Quality section). The water-quality and streamflow 

data collected for streamgage station 0423368620 from 

October 18, 2002, through September 30, 2004, are presented 

by Hornlein and others (2004, p. 182–183; 2005, p. 177–180).

Seismic-Refraction Surveys

Seismic-refraction surveys were conducted at three 

sites to supplement data from test drilling and well records. 

These surveys obtained data on depth to the water table and 

the bedrock surface. Seismic-refraction techniques used 

in this study are described by Haeni (1988). A series of 

12 geophones spaced either 50 or 100 ft apart were inserted 

into the ground, and arrival times of compressional waves 

generated by explosives were recorded and plotted as a 

function of source-to-geophone distances. Either a two-layer 

(saturated unconsolidated sediments and bedrock surface) 

or a three-layer (unsaturated unconsolidated sediments, 

saturated unconsolidated sediments, and bedrock surface) 
Geology 5

boundary-formula computer analysis (Scott and others, 1972) 

was used to calculate depths to the water table and to the 

bedrock surface.

One of the limitations to using seismic-refraction 

techniques, which was encountered in this study area, is the 

presence of slow-seismic velocity units (saturated sand and 

gravel) underlying high-seismic velocity units (compact till). 

In this setting, the low-velocity unit will not be detected, and 

the calculated depth to the deep refractor (top of bedrock) 

will likely be in error (the computed seismic depth to bedrock 

will be greater than the actual depth; Haeni, 1988). Where 

the depths to bedrock were available at drill holes along 

the seismic line, those depths were used to depict the top of 

bedrock in the geologic section. In the parts of the seismic 

lines where depths to bedrock were unavailable from drillhole data, it is likely that the depth to bedrock computed from 

seismic-refraction data is deeper than actual depths.

Water Sampling and Analysis

Stream samples were analyzed for inorganic constituents 

and nutrients at the USGS National Water Quality Laboratory 

(NWQL) in Denver, Colorado. Field properties including pH, 

specific conductance, and water temperature were measured 

before sample collection. The samples were collected and 

processed by methods described in the USGS manual 

for the collection of water-quality data (U.S. Geological 

Survey, 2004a).

Groundwater samples were collected from public-supply 

wells at raw-water spigots after the well had been pumped 

for more than an hour. Domestic wells were sampled after 

20 minutes of pumping or until at least five casing volumes of 

well water had passed the sampling point; then a raw-water 

spigot between the well and the pressure tank was opened, and 

the water was allowed to run for several more minutes to flush 

the spigot. Samples were collected from the raw-water spigot 

to avoid all water-treatment systems and to ensure that the 

water collected was representative of the water in the aquifer. 

In unused test wells, a stainless-steel submersible pump was 

used to purge the well of 5 to 10 casing volumes of water 

before collecting the water samples from the pump.

Tritium samples, collected to estimate groundwater age, 

were analyzed at the USGS Isotope Geochemistry Laboratory 

in Menlo Park, California. Chlorofluorocarbon (CFC) samples 

were collected according to specific sampling methods to 

minimize atmospheric exposure (U.S. Geological Survey, 

2004b) and were analyzed at the USGS Chlorofluorocarbon 

Laboratory in Reston, Virginia. Age-dating of groundwater 

using these methods gives an approximate date since the 

water recharged the aquifer (from precipitation) and entered 

the saturated zone. The ages are based on matching the 

concentrations of the tracers in groundwater to the historical 

atmospheric concentrations of these tracers, which are well 

documented. Details of CFC dating are explained in Plummer 

and others (1993) and Reilly and others (1994).

Dissolved gases were also analyzed from the five wells 

where CFC samples were collected. Dissolved-gas data are 

used to define recharge temperatures for CFC dating, to 

reconstruct initial nitrate concentrations based on the amount 

of denitrification that has occurred, and to trace sources of 

groundwater recharge. Temperature and excess air in recharge 

water are important components in determining the age of 

the water based on concentrations of CFCs, and these factors 

can be calculated from the ratios of dissolved nitrogen and 

argon gas concentrations in the water along with the altitude 

at which recharge occurs (Heaton, 1981; Heaton and Vogel, 

1981; Stute and Schlosser, 1999).

Description of Study Area

The study area is in the Appalachian Plateau 

physiographic province (fig. 2). The plateau is characterized 

by hills and valleys that resulted from millions of years of 

dissection by initially south-flowing streams that have been 

pirated (captured) by advancing northward-flowing streams 

draining into Lake Ontario (fig. 2). The hills and valleys have 

been subsequently modified by several glaciations.

The study area is 5.3 mi long and 1.0 mi wide and 

encompasses 5.4 mi2

 in the Dryden Lake Valley and parts 

of the Virgil Creek and Owego Creek Valleys (fig. 3). The 

Dryden Lake Valley and the Virgil Creek Valley have northerly 

flowing drainage that joins Fall Creek 2.7 mi northwest of 

the Village of Dryden. The Owego Creek Valley drains to the 

south and is part of the Susquehanna River Basin (fig. 3).

The study area is of moderate relief, with altitudes 

ranging from as low as 1,060 ft in the channel where Virgil 

Creek leaves the north part of the study area to a little more 

than 2,000 ft on the highest hilltops (fig. 4). The Virgil Creek 

Valley is an intrusive valley that incised through a 600- to 

800-ft high escarpment (referred to as the Portage escarpment 

by von Engeln (1961)) in the northern part of the study area 

(fig. 4).

Geology

Geologic materials present in the study area include 

bedrock, unstratified and stratified glacial drift, and recent 

alluvium and swamp deposits. Bedrock consists of Devonian 

shale, siltstone, and fine-grained sandstone. In most places, 

bedrock is covered by unconsolidated sediments; however, 

in some places, bedrock crops out at land surface, such as on 

hilltops and on upper parts of oversteepened valley walls.

The sedimentary rocks that form the bedrock in the 

study area were deposited in ancient seas during the Devonian 

period, 416 to 359.2 million years ago (Isachsen and others, 

1991). The rocks were uplifted during the Alleghanian 

orogeny in the late Paleozoic, about 330 to 250 million years 

ago (Isachsen and others, 1991). The uplifted rocks formed 
6 Geohydrology, Water Quality, and Simulation of Groundwater Flow, Town of Dryden, Tompkins County, New York

25 50 75 100 MILES

0 25 50 75 100 KILOMETERS

0

Hill 

Plateau

Adirondack Mountains 

New England Uplands

Atlantic Coastal Plain

Triassic Lowland

Erie 

Lowlands

Ontario Lowlands

Appalachian Plateau

Appalachian Plateau (hills of moderate relief)

(hills of moderate relief)

Finger Lakes and hills of the 

Appalachian Plateau 

(severly eroded- low relief) Tompkins

County

45°

80° 79° 78° 77° 76° 75° 74° 73° 72°

44°

43°

42°

41°

NEW YORK

PENNSYLVANNIA

Valley Heads

Moraine

CONNECTICUT

MASSACHUSETTS

VERMONT

NEW 

HAMPSHIRE

NEW JERSEY

CANADA

St. Lawrence-Champlain Lowlands

Tug

Wallkill-Hudson

Lowlands

Mowhawk

Lowlands

Study area (in red)

ATLANTIC OCEAN

Lake Ontaroi

Lake Erie

Base from U.S. Geological Survey digital data, 1972, 1:2,000,000

Albers equal-area conic projection

Standard parallels 20°30' and 45°30', central meridian -96°00'

CANADA

UNITED STATES

Figure 2. Physiographic features of New York State and location of Virgil Creek Valley and Dryden Lake Valley study area 

in Tompkins County, New York.

a plateau (Appalachian Plateau) which has subsequently 

undergone dissection by streams that resulted in a region 

dominated by hills and valleys. The bedrock landforms in the 

study area were modified by several glaciations during the 

Quaternary period, which extended from 2.6 million years ago 

to when the last glacier left the study area about 14,400 years 

before present (BP).

Glacial till is a poorly sorted and unstratified mixture of 

stones embedded in a fine-grained matrix consisting of clay, 

silt, and very fine sand. The stones in till can range in size 

from pebbles to boulders. Till is deposited directly by glacial 

ice, rather than by meltwater. In this study area, there are at 

least two till units that are interbedded within the stratified 

drift in the valley. Till has very low permeability (hydraulic 

conductivity is very low) because it is poorly sorted and has 

a fine-grained matrix that was compacted by the weight of 

the glacier.

Stratified drift consists of layered and sorted sediments 

that were deposited chiefly in valleys as glaciofluvial 

sediments by glacial meltwater streams and as glaciolacustrine 

sediments deposited in proglacial lakes. Coarse-grained (sand 

and gravel) glaciofluvial sediments deposited as outwash and 

kames form either extensive confined aquifers where they are 

overlain by a confining unit or smaller unconfined aquifers 

where they are found on top of the uppermost confining unit. 

Fine-grained glaciolacustrine sediments of very fine sand, silt, 

and clay deposited in a proglacial lake form confining units, 

along with till.

Glacial History

The study area underwent several major glaciations 

during the Pleistocene epoch (fig. 5), commonly referred to 

as the ice age, which began 2.6 million years ago and ended 
Geology 7

Figure 3. The boundary of the stratified-drift aquifer system extending across the Virgil Creek and Owego Creek 

Basins, Tompkins and Cortland Counties, New York. Basin boundaries indicated by red lines.

76°20' 76°15'

42°30'

42°25'

0 1 2 MILES

0 1 2 KILOMETERS

Tompkins County

NEW

YORK

Owego Creek Basin

Approximate location of former bedrock col 

that was preglacial surface-water divide

Sixmile Creek Basin

Virgil Creek Basin

Fall Creek

Basin

Fall 

Creek

Basin

Owasco 

Inlet

Basin

Otter Creek

Basin

Virgil

Creek Valley

Dryden

Lake

Valley

Owego Creek

Valley

Boundary of stratified-drift 

aquifer system study area

(dashed where boundary 

is arbitrarily cut off)

Fall Creek

Fall Creek

Virgil Creek

Base from TOPO! 2003 ©National Geographic, scale 1:100,000
8 Geohydrology, Water Quality, and Simulation of Groundwater Flow, Town of Dryden, Tompkins County, New York

Figure 4. Topographic altitudes, shaded relief, and boundary of stratified-drift aquifer system study area in the Virgil 

Creek, Dryden Lake, and Owego Creek Valleys, Tompkins County, New York. NAVD88, North American Vertical Datum 

of 1988.

76°20' 76°15'

42°30'

42°25'

0 1 2 MILES

0 1 2 KILOMETERS

% % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % %

% % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % %

% % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % EXPLANATION

Altitude, in feet

(Datum is NAVD88)

950 - 1,000

1,000 - 1,050

1,050 - 1,100

1,100 - 1,150

1,150 - 1,200

1,200 - 1,250

1,250 - 1,300

1,300 - 1,350

1,350 - 1,400

1,400 - 1,450

1,450 - 1,500

1,500 - 1,550

1,550 - 1,600

1,600 - 1,650

1,650 - 1,700

1,700 - 1,750

1,750 - 1,800

1,800 - 1,850

1,850 - 1,900

1,900 - 1,950

1,950 - 2,000

2,000 - 2,050

2,050 - 2,100

2,100 - 2,150

TOMPKINS COUNTY CORTLAND COUNTY

TIOGA COUNTYTOMPKINS COUNTY

CORTLAND COUNTY

Town of Dryden Town of Virgil

Town of Cortlandville

Town of Groton

Town of Harford

Town of Caroline Town of Richford

Village 

of Dryden

Village 

of Freeville

Boundary of stratified-drift 

aquifer system study area

(dashed where boundary is

arbitrarily cut off)

Portage Escarpment

Portage Escarpment

Base from U.S. Geological Survey, Seamless Data Distribution System,

accessed in 2008 at URL http://seamless.usgs.gov/

Universal Transverse Mercator projection, Zone 18

Approximate location of preglacial 

drainage divide
Geology 9

Figure 5. Chronostratigraphic classification of Pleistocene stades and interstades in northeastern 

North America and their effect on the study area. Modified from Dreimanis and Karrow (1972) and 

Fulton and others (1984). 14C, carbon 14; YBP, years before present.

System/Period

System/Epoch

Stage

Substage

Stades and interstades

14C age YBP

Events that affected the study area

11,850

12,500

Late Wisconsinan

St. Pierre interstade

68,000

63,000

36,000

Cherrytree stade

Port Talbot interstade

Ice retreats north of Ithaca

13,500

15,500

16,500

Quaternary

Pleistocene

Wisconsinan

Postglacial erosion and depostion by 

recent streams

Port Huron stade

13,000

Mackinaw interstade

HoloceneHolocene

Two Creeks interstade

Erie interstade

Plum Point interstade

Middle Wisconsinan Early Wisconsinan

New York is ice free

Ice retreats north of Ithaca

75,000

Nicolet stade

Nissouri stade

Port Bruce stade

23,000

32,000

53,000

Guildwood stade

Valley Heads readvance-forms massive 

moraines

Wisconsinan ice sheet spreads across

New York
10 Geohydrology, Water Quality, and Simulation of Groundwater Flow, Town of Dryden, Tompkins County, New York

11,850 years BP (uncalibrated radiocarbon years; 13,700 

calibrated calendar years; Fullerton, 1980). A raw BP date 

cannot be used directly as a calendar date because the level of 

atmospheric 14C has not been strictly constant during the span 

of time that can be radiocarbon dated. The raw radiocarbon 

dates, in BP years, are calibrated to give calendar dates.

Each successive glaciation removed or reworked most 

of the previously deposited sediments; therefore, most of the 

unconsolidated deposits consist of sediments deposited during 

and after the last glacial episode (Wisconsinan glaciation). 

During the Wisconsinan glaciation, the Laurentide Ice Sheet 

expanded southward from northeastern Canada and advanced 

and retreated several times into New York State.

During the last major glacial episode in Late Wisconsinan 

time, the maximum extent of the glacier occurred during 

the Nissouri stade (a period of time represented by a glacial 

advance) about 24,000 to 23,000 years BP (Muller and 

Calkin, 1993), when the ice extended as far south as northern 

Pennsylvania. During the Erie interstade (about 16,500 to 

15,500 years BP; fig. 5), the ice retreated northward from 

Pennsylvania and is believed to have melted back to north 

of the study area. The location of the ice margin during the 

retreat is uncertain because there are no radiocarbon data 

in New York for this period (Muller and Calkin, 1993) and 

evidence for the Erie interstade is based on circumstantial data 

(Dyke and others, 2002).

Following the Erie interstade, ice readvanced into central 

New York during the Port Bruce stade (about 15,500 years 

BP; fig. 5). In the study area, the advancing ice deposited 

a massive kame moraine, called the Valley Heads Moraine 

(fig. 6, surficial geologic unit km), in the southern part of the 

Dryden Lake Valley and in the eastern part of the Virgil Creek 

Valley. During this period, the ice had likely surged back and 

forth as evidenced by multiple sequences of glacial deposits 

that include interlayers of till, lacustrine sediments, and fluvial 

sand and gravel. The final retreat of ice from the study area 

commenced around 14,400 years BP (Muller and Calkin, 

1993); the ice retreated rapidly northward and probably took 

several hundred years to retreat north of the study area. The 

retreat of Valley Heads ice north of the study area marked 

the end of the influence of ice in the study area. The multiple 

advances and retreats of the ice during stadial and interstadial 

periods, in addition to the minor surges of ice, resulted in a 

complex array of multiple sequences of glacial deposits in the 

study area that, in some places, makes it difficult to map and 

correlate geologic units.

Scouring by Ice

In the area south of the Finger Lakes region, including 

the study area, scouring by flowing ice and subglacial 

meltwaters played a major role in modifying the preglacial 

landscape. Most scouring was concentrated in the valleys (hill 

tops were little modified), which resulted in smoothed and 

truncated hillsides along valley walls, U-shaped transverse 

valley profiles, and displacement of a bedrock col (a high, 

narrow pass or saddle through a divide or between two 

adjacent hilltops) that was a preglacial surface-water drainage 

divide (fig. 3). The configuration of the altitude of the bedrock 

valley as a result of glacial scouring is shown on figure 7.

The Dryden Lake Valley and many other valleys along 

the northern part of the Appalachian Plateau (fig. 2) are 

referred to by Clayton (1965) as intrusive troughs. Intrusive 

troughs were north-draining, preglacial valleys that were 

oriented in the direction of glacier flow. As the ice flowed 

south from the Ontario lowlands (fig. 2) and uphill against the 

regional slope of a higher landmass (Appalachian Plateau), 

ice flow was funneled and concentrated into preglacial, 

north-draining tributary valleys. The concentration of ice flow 

extensively scoured (widened and deepened) these valleys 

forming deep troughs. Results of test drilling at the Village of 

Dryden well field (TM1695; location shown in fig. 8, well log 

shown in fig. 9) in the northern part of the study area, and a 

seismic-refraction survey along Purvis Road in the southern 

part of the study area (figs. 10A, B), indicate that the valley is 

filled with about 400 ft of unconsolidated sediments and the 

bedrock floor in the Dryden Lake Valley rises from an altitude 

of 728 ft at the Village of Dryden in the northern part to an 

altitude of about 800 ft at Purvis Road in the southern part of 

the study area (fig. 7).

The northwest-southeast-oriented Dryden Lake Valley, 

which was aligned parallel to the direction of ice flow, 

underwent more extensive erosion (greater amount of 

deepening and widening) than the eastern branch of Virgil 

Creek Valley, which diverges eastward from Dryden Lake 

Valley (fig. 7). The eastern branch of Virgil Creek Valley, 

which was orientated nearly perpendicular to the direction 

of ice flow (southwest-northeast), underwent less intensive 

erosion (less deepening and widening) than that in the Dryden 

Lake Valley. In the eastern branch of the Virgil Creek Valley, 

a log of test well TM 997 (fig. 11) at the Virgil Creek Dam 

and results of a seismic-refraction survey in the floodplain 

of the Virgil Creek channel (figs. 12A, B) indicate that the 

altitude of the bedrock floor ranges from 1,085 to 1,100 ft, 

while the bedrock floor in the Virgil Creek Valley at the Lake 

Road pumping station in the Village of Dryden is at altitude 

728 ft (fig. 9). Consequently, the eastern branch of the Virgil 

Creek Valley is a hanging valley (fig. 7) with a bedrock floor 

that is several hundred feet higher than that in the Dryden 

Lake Valley.

In the Dryden Lake Valley, the deepest part of the valley 

is not in the center, but rather along the southwestern side of 

the valley (figs. 7 and 10A, B), which indicates that either the 

ice dynamics were such that ice flow was concentrated against 

the southwestern valley wall or the preglacial valley may have 

been located there or both. The more extensive scouring along 

the southwestern side of the valley resulted in an asymmetrical 

transverse profile of the bedrock surface in that part of the 

study area (fig. 10B).
Geology 11

Figure 6. Surficial geology map of Virgil Creek, Dryden Lake, and Owego Creek Valleys, Tompkins and Cortland 

Counties, New York. Modified from Miller (1993).

0 2,000 4,000 FEET

0 500 1,000 METERS

t/r

t/r

t/r

t/r

t/r

al/t

al/t

ksg/t

ksg/t

km

km

al

al

al

ksg/t

km

t/usg

t/usg

ksg

ksg/t

km

al

al

alf/km/t

alf/osg

w

ksg

km

km

km

tm

ksg

alf/t

km

w

pm

al/osg

alf

tm

pm

pm

al

pm

pm

76°18' 76°16' 76°14'

42°28'

42°26'

Base from U.S. Geological Survey, Seamless Data Distribution System, accessed in 2007 at http://seamless.usgs.gov /

Universal Transverse Mercator projection, Zone 18 Geology modied from Miller, 1993

EXPLANATION

Water

Wetland

Surficial geologic units

Alluvial fan over outwash sand and gravel

Alluvial fan 

Alluvium over outwash sand and gravel

Alluvium

Alluvium over till

Kame sand and gravel

Kame moraine (Valley Heads Moraine)

Kame sand and gravel over till

Till moraine

Valley till over unclassified sand and gravel

Upland till over bedrock

Stratified-drift aquifer system study area—

dashed where boundary is arbitrarily cut off

Alluvial fan over kame moraine and till

Alluvial fan over till

w

pm

alf

alf/km/t

alf/osg

Dryden

Lake

alf/t

al/osg

al t/r

t/usg

km

ksg/t

tm

ksg

al/t

Outwash head

Valley Heads Moraine

Valley Heads Moraine

Daisy

Hollow Brook
12 Geohydrology, Water Quality, and Simulation of Groundwater Flow, Town of Dryden, Tompkins County, New York

Figure 7. Altitude of bedrock surface and location of lines of seismic refraction cross-sections in the study area in 

the Virgil Creek, Dryden Lake, and Owego Creek Valleys, Tompkins and Cortland Counties, New York.

76°18' 76°16'

42°30'

42°28'

42°26'

0 0.5 1 MILE

0 0.5 1 KILOMETER

900

800

800

1000

1100

1200

1300

750

1400

1500

1100

900

1100

1200

800

1200

1000

1300

1400

1000

1000

1300

1200

1100

900

900

750

1200

1200

1100

1100

1000

800

900

900

EXPLANATION

900 Bedrock contour—Shows approximate altitude of 

bedrock surface. Contour interval 100 feet except 

where noted. Datum is National Geodetic Vertical 

Datum of 1929.

Aquifer study area

Data point and altitude (in feet) of top of bedrock.

Datum is National Geodetic Vertical Datum of 1929.

A A’ Line of seismic refraction cross-section

Hanging valley

Purvis Road

seismic-survey site

Virgil Creek Dam

seismic-survey sites

Base from U.S. Geological Survey, Seamless Data Distribution System,

accessed in 2007 at http://seamless.usgs.gov/

Universal Transverse Mercator projection, Zone 18

A A’

B

C

C’

B’

x 728

x 930

x 1,063

x 1,258

x 1,202

x

1,184

x 1,170

x 1,170

x 1,091

x 1,136

x

1,181

x 1,195
Geology 13

Figure 8. Locations of wells and lines of geologic cross-sections, seismic refraction cross-sections, and 

a hydrologic cross-section in the study area in the Virgil Creek, Dryden Lake, and Owego Creek Valleys, 

Tompkins and Cortland Counties, New York. (Available separately at http://pubs.usgs.gov/sir/2013/5070/pdf/

sir2013-5070_miller_fig08_sheet.pdf)

76°18' 76°16' 76°14'

42°30'

42°28'

42°26'

0 0.5 1 MILES

0 0.5 1 KILOMETERS

B

B’

A’

A’

A

A

C’

C

B

B’

R

R

R

C 123

C 122

C 88

C 75

C 44

TM2118

TM2103

TM2509

TM2444

TM2094

TM2081

TM2070

TM2063

TM2020

TM2001

TM1940

TM1920

TM1887

TM1855

TM1779

TM1735 TM1725

TM1699

TM1700

TM1629

TM1580

TM1543

TM1524

TM1432

TM2480

TM2256

TM1386

TM1384

TM1374

TM1334

TM1034

TM1033

TM1032 TM1031

TM1030

TM1016

TM1014

TM1013

TM1012

TM1011

TM1010

TM1005

TM1007

TM1006

TM1006

TM1005

TM1000

TM 997,

TM 998

TM 993

TM 981

TM 214

TM1050

TM 207

TM 204

TM1695 TM 203

TM 202

TM 199

TM 198

TM 195 TM 193

TM 192

TM 189

TM 187 TM 184

TM 179 TM 178 TM 177

TM 174

TM 172

TM 171

TM 169 TM 170

TM 168

TM 166 TM 164 TM 163 TM 162 TM 161 TM 160 TM 157

TM 156 TM 154

TM 152 TM 153

TM 150

TM 149

TM 146

TM 145 TM 144 TM 143

TM 141

TM 138 TM 135

TM 134

TM 133

TM2571

TM 125

TM 159

TM2724

TM1676

TM1046

Jim Schug trail

C 57

TM1015

C 609

TM1920

Base from U.S. Geolgical Survey

1:24,000 Digital Line Graph

TM2063

Village of Dryden boundary

Drainage divide between Dyden Lake and Owego Creek Valleys

Line of geologic cross-section

Line of hydrologic cross-section—Hydrogic cross-section shown in figure 36.

Line of seismic refraction cross-survey

Boundary of stratified-drift aquifer system study area—Boundary dashed where arbitrarily cut off.

Well used for domestic-water supply and well site name—Site name is assigned by U.S. Geological 

Survey. Well data are in appendix at end of report.

TM2063 Flowing-artesian well used for domestic-water supply and well site name—Site name is assigned 

by U.S. Geological Survey. Well data are in appendix at end of report.

Observation well drilled for this study to collect water data and well site name—Site name is 

assigned by U.S. Geological Survey. Well data are in appendix at end of report.

Test hole bored for previous studies and test hole site name—Site name is assigned by U.S. Geological 

Survey. Well data are in appendix at end of report.

Well used for agriculture and well site name—Site name is assigned by U.S. Geological Survey. 

Well data are in appendix at end of report.

Well used for small commercial facility and well site name—Site name is assigned by U.S. Geological Survey. 

Well data are in appendix at end of report.

Well used for non-municipal community supply and well site name—Site name is assigned by U.S. 

Geological Survey. Well data are in appendix at end of report.

Flowing artesian well used for non-municipal community supply and well site name—Site name is 

assigned by U.S. Geological Survey. Well data are in appendix at end of report.

Unused water well and well site name—Site name is assigned by U.S. Geological Survey. Well data are 

in appendix at end of report.

Unused water well equiped with water-level recorder and well site name—Site name is assigned by 

U.S. Geological Survey. Well data are in appendix at end of report.

Well used for municipal-public supply and well site name—Site name is assigned by U.S. Geological 

Survey. Well data are in appendix at end of report.

EXPLANATION

TM2724

TM1033

C 44

TM 207

TM 199

Observation well drilled for this study (equipped with water-level recorder) and well site name—

Site name is assigned by U.S. Geological Survey. Well data are in appendix at end of report.

TM 993

TM 981

TM 170

TM1384

R

R

A A’

A A’

A A’

Figure 8. Locations of wells and lines of geologic cross-sections, seismic refraction cross-sections, and a hydrologic cross-section in the study area in the Virgil Creek, Dryden Lake, and Owego Creek Valleys, Tompkins and Cortland Counties, New York.

A A’

Village of Dryden

Keith Lane

Former spring fed reservoir 

(spring use discontinued in 

1963, reservoir currently used 

as a water storage facility)

Water 

tank

South Street

Lake

Road

Jay

Street

Hamlet 

of Harford

New York State Department 

of Environmental Conservation 

boat access facility

U.S. DEPARTMENT OF INTERIOR

U.S. GEOLOGICAL SURVEY

PREPARED IN COOPERATION WITH 

TOMPKINS COUNTY DEPARTMENT OF PLANNING AND TOWN OF DRYDEN SCIENTIFIC INVESTIGATIONS REPORT 2013-5070 Location of wells, test borings, lines of geologic sections, and seismic surveys

Sewage

treatment plant
14 Geohydrology, Water Quality, and Simulation of Groundwater Flow, Town of Dryden, Tompkins County, New York

Figure 9. Construction details of U.S. Geological Survey test wells TM1695, TM1699, and TM1700 and well log of test well TM1695 at 

Lake Road near Dryden, New York. Locations shown on figure 8.

Well depth = 300 feet

6 inch steel casing, open end

(finished in clay)

Borehole (mud rotary)

deepened from 300 to 

396 feet May 27, 2003

No aquifers penetrated

No casing or screen

installed in this interval

Well abandoned

760

752

745

728

719

965

935

860

845

1,064

1,056

1,033

1,018

1,007

1,086

1,075

760

752

745

728

719

965

935

860

845

1,064

1,056

1,033

1,018

1,007

Till or silty gravel, grey, silty matrix, 

gravel lens at 24 to 26 feet

Gravel

Very fine and fine sand, grey

Sand and gravel, silty 62 to 66 feet

Sand and gravel, 66 to 82 feet

Till, gravel, silty/clay matrix, stony

Till, grey, silty/clay matrix, stony,

no water

Sand and gravel, grey brown,

lenses of sand and silt

1,086

1,115086 Topsoil

Clay, soft

Silt

0

3

8

29

Depth below land surface, in feet

Silty sand and gravel

Hardpan (till)

40

51

59

62

82

97

100

108

150

180

255

270

355

363

370

387

396

Clay, soft

Clay, silt, and sand

Fine sand (quicksand or 

flowing sand)

Clay, grey, soft, no stones

Shale, medium grey, 

Clay

Clay, grey, soft, no stones

Till, grey, silt/clay matrix, 

stony, dense

Silt and very fine sand

Well depth = 41 Feet

6 inch diameter steel, 

open end

Water level= 7.3 feet 

(not reliable-- 

well plugged with 

sediment before

and after drilling

Sump below 

screen from

72 to 115 feet

Water level =7.86 feet 

below top of casing, 

6/10/2003. Altitude of

water level = 1,110.83 

feet

Water level 

= 8.06 feet

below land 

surface 6/3/03

El. water level

= 1,110.38 feet

Well depth = 72 feet

Bore hole depth = 115 feet

4 inch diameter pvc casing 

10 foot long 

pvc srceen

from 62 to 72 feet

Well drilled to 300 feet

in the 1970s

TM1695

5/27/2003

42o

28' 58.8''

076o

17' 27.6''

TM1700

5/29/2003

42o

28' 58.5''

076o

17' 27.4''

Altitude top of

casing = 1117.19 feet 

Altitude top of

casing = 1118.69 feet

Altitude top of

casing = 1118.44 feet

TM1699

5/28/2003

42o28' 58.4''

076o

17' 27.6''

1,075

Date drilled:

Latitude:

Longitude:

Site name:

Altitude relative to National GeodeticVertical Datum of 1929

Bottom of hole at 396 feet below land surface
Geology 15

1 2 3 4 5 6 7 8 9 101112

0 ft

500

1,050

1,600

2,100 ft

S1 S2 S3

0

0 100

500 1,000 FEET

200 METERS

Bedrock hill

Bedrock hill

76° 16’ 20” 76°

 15’ 30”

42°

 27’ 30”

42°

 26’ 30”

EXPLANATION

Seismic-refraction survey line

1 2 3 4 5 6 7 8 9 101112

0 ft

500

1,050

1,600

2,100

S2 S1 S3

Distance from initial shot point

Shot Shot

Geophones

Aquifer boundary

Base from Tompkins County 12- and 24-inch resolution 

color infrared orthoimagery, New York State Office of Cyber 

Security and Critical Infrastructure Coordination, 2002

DRYDEN LAKE

A A’

Purvis Road

seismic-survey site

A

Figure 10. A, location of line of seismic refraction cross-section and B, seismic refraction cross-section A–A′ along Purvis Road, 

Town of Dryden, New York, in the southern part of Dryden Lake Valley. Location of line of seismic refraction cross-section shown on 

figure 8.
16 Geohydrology, Water Quality, and Simulation of Groundwater Flow, Town of Dryden, Tompkins County, New York

Figure 10. A, location of line of seismic refraction cross-section and B, seismic refraction cross-section A–A′

along Purvis Road, Town of Dryden, New York, in the southern part of Dryden Lake Valley. Location of line of 

seismic refraction cross-section shown on figure 8.—Continued

0

0 50

200 400 FEET

100 METERS

Saturated unconsolidated deposits,

velocity = 5,000 feet per second

Bedrock (shale),

velocity = 14,850

feet per second

1,000

900

800

1,100

1,300

1,200

VERTICAL EXAGGERATION x4

Verical datum is National

Geodetic Vertical Datum of 1929, in feet

FEET A A’

WEST EAST

Land surface

Unsaturated unconsolidated deposits Velocity = 2,500 feet per second

B

Center 

of 

valley

Seismic-refraction survey line

Shot

1 Shot

2 Shot

3
Geology 17

Figure 11. Construction details of U.S. Geological Survey test wells TM 997 and TM 998 at Virgil Creek Dam in the Town of Dryden, 

New York. Locations shown on figure 8.

Virgil Creek

altitude of water

surface =

1197.5 feet

11/21/2005

1,096

1,100

1,109

1,123

1,132

 1,152

1,161

1,205

1,196

1,132

1,123

1,109

1,100

1,096

Sand and gravel, fine to coarse pebbles, makes some 

water ~ 3 gallons per minute

Makes water ~ 30 gallons per minute

Three-foot diameter boulder from 72 to 75 ft

Silty clay, grey, massive, no stones

Silty clay, grey, massive, very dense, no stones

Siltstone, greyish green

1,196

1,205

1,2095

Gravel, brown, fine to coarse pebbles, some cobbles, 

subround to round clasts, dry

Gravel, brown, fine to coarse pebbles, some cobbles, 

subround to round clasts. saturated

Silt and clay mixed with some stones (till?)

Stony till or silty gravel, grey matrix, makes no water

Fill, silt mixed with some stones

0

Depth below land surface, in feet

4

13

48

 57

 77

 86

Bottom of casing = 110 feet

Water level in 

deep aquifer 

= 19.6 feet below

land surface 

(altitude 1189.4 

feet) 11/21/2005

Water level in 

unconfined aquifer 

= 13.2 feet below

land surface (altitude

1195.8 feet) 11/21/2005

Water from confined

aquifer enters 6-inch 

diameter well through 

perforations in casing 

between 79 to 84 feet

100

109

113

Site name: TM 997 (well depth = 84 feet)

Site identifier: 422824076154501

Latitude: 42o

28' 23.58''

Longitude: 076o

15' 45.23''

Date completed: 11/17/2005

6-inch-diameter steel casing

Casing above ground = 2.1 feet

TM 997

Altitude of top of 

6-inch casing

= 1,211.1 feet

TM 998

Altitude of top of 

6-inch casing

= 1,211.4 feet

Site name: TM 998 (well depth = 37 feet)

Site identifier: 422823076154501

Latitude: 42o

28' 23.49''

Longitude: 076o

15' 45.26''

Date completed: 11/18/2005

6-inch-diameter steel casing

Casing above ground = 2.4 feet

Altitude relative to National Geodetic

Vertical Datum of 1929, in feet
18 Geohydrology, Water Quality, and Simulation of Groundwater Flow, Town of Dryden, Tompkins County, New York

Figure 12. A, locations of lines of seismic refraction cross-sections, test wells TM 997 and TM 998, and streamflowmeasurement sites near the Virgil Creek Dam, Town of Dryden, New York, B, seismic refraction cross-section B–B′

along the Virgil Creek floodplain, and C, seismic refraction cross-section C–C′ in the spillway of the Virgil Creek Dam. 

Locations of wells and lines of seismic refraction cross-sections are shown on figure 8.

Virgil Creek

Flow

Aquifer boundary (inside)

 (outside)

1 2 3 4 5 6 7 8 9 10 11 12

0 ft

38

88

138

238

338

438

538

638

738

838

938

988

1,028 ft

123456789101112

144

0 ft

344

444

544

244

744

844

944

1,044

1,144

1,244

644

1,394 ft

s

s s

0

0 50

250 500 FEET

100 METERS

Emergency spillway

Earthen dam

CORTLAND CO

Base from Tompkins County 12-inch resolution 

color infrared Oothoimagery, New York State Office of Cyber 

Security and Critical Infrastructure Coordination, 2002

42°

 28’ 38”

76°

 15’ 55” 76° 15’

42°

 28’ 08”

B

C

C’

TOMPKINS CO

B’

A

EXPLANATION

Line of seismic-refraction survey 

1 2 3 4 5 6 7 8 9 10 11 12

0 ft

3888

1382383384385386387388389389881,028 ft

Geophones

Distance from initial shot point

Shot Shot

s s

s

s

Streamflow-measurement site, number 

is stream discharge in cubic feet per 

second. Measurement made on 

May 10, 2007

12.7

Test wells

TM 997 and

TM 998

12.7

11.5
Geology 19

Land surface

1,050

1,100

1,150

1,200

1,250

VERTICAL EXAGGERATION x 4 0

0 25

100 200 FEET

50 METERS

B B’

FEET

WEST EAST

Virgil 

Creek

Saturated unconsolidated deposits,

velocity = 5,000 feet per second

Bedrock (shale),

velocity = 14,850

feet per second

B

Vertical datum is National Geodetic Vertical Datum of 1929

Shot

1

Shot

2

Figure 12. A, locations of lines of seismic refraction cross-sections, test wells TM 997 and TM 998, and 

streamflow-measurement sites near the Virgil Creek Dam, Town of Dryden, New York, B, seismic refraction 

cross-section B–B′ along the Virgil Creek floodplain, and C, seismic refraction cross-section C–C′ in the 

spillway of the Virgil Creek Dam. Locations of wells and lines of seismic refraction cross-sections are 

shown on figure 8.—Continued
20 Geohydrology, Water Quality, and Simulation of Groundwater Flow, Town of Dryden, Tompkins County, New York

Figure 12. Map and diagrams showing A, locations of lines of seismic refraction cross-sections, test wells TM 997 and TM 998, and 

streamflow-measurement sites near the Virgil Creek Dam, Town of Dryden, New York, B, seismic refraction cross-section B–B′ along 

the Virgil Creek floodplain, and C, seismic refraction cross-section C–C′ in the spillway of the Virgil Creek Dam. Locations of wells and 

lines of seismic refraction cross-sections are shown on figure 8.—Continued

1,150

1,200

1,250

1,300

0

0 25

100 200 FEET

50 METERS

C C’ FEET

NORTHEAST SOUTHWEST

Land surface

Virgil Creek Dam

emergency 

spillway

VERTICAL EXAGGERATION x 4

Vertical datum is National Geodetic Vertical Datum of 1929

Saturated unconsolidated deposits,

velocity = 5,000 feet per second

Bedrock (shale),

velocity = 14,500

feet per second

Shot

2 Shot

3

Shot

1

C

Wisconsinan Deposits in the Study Area

The valley fill in the study area contains glacial drift that 

consists of unstratified (till) and stratified (glaciolacustrine 

and glaciofluvial) glacial sediments deposited during 

Wisconsinan glaciation and recent (postglacial) alluvium and 

swamp deposits (fig. 6). The unstratified drift consists of till. 

In most places in the uplands, till is the sole unconsolidated 

deposit that overlies bedrock. However, in the valley, there 

are typically multiple till units that are interlayered with 

other units of stratified drift. In the study area, till makes up 

a large portion of the drift, and in some places, it crops out at 

land surface.

The stratified glacial drift (glaciolacustrine and 

glaciofluvial deposits) consists of layered and sorted 

sediments. Glaciolacustrine deposits (lake-bottom and deltaic 

sediments) were deposited where meltwater that had flowed 

on top, within, or at the sole of the ice debouched into a lake 

in front of the ice. The deposits consist of (1) coarse-grained 

sediments (sand and gravel) deposited at nearshore subaerial 

environments and at the mouths of subglacial tunnels, 

(2) medium-grained sediments (mostly sand and pebbly sand) 

deposited in shallow water, such as at the front of the delta 

shore (foresets), and (3) fine-grained sediments (fine sand, silt, 

and clay) deposited in deep water at distal parts of a delta.

Glaciofluvial deposits consist of layered and sorted 

coarse-grained sediments (sand and gravel) that were 

transported and deposited by meltwaters that flowed on top, 

beneath, or within a glacier. Glaciofluvial deposits include 

outwash, kame, and kame end moraine sediments. Outwash 

was deposited by meltwaters that flowed away (southward) 

from the ice front. In the study area, outwash was deposited in 

front of the Valley Heads Moraine in the Dryden Lake Valley 

and extends southward as an outwash plain in the Owego 

Creek Valley (fig. 6).

Kame deposits consist of glaciofluvial (sand and gravel 

that was transported by meltwater) and inwash (silt, sand, 

and gravel transported by streams that drain uplands) that 

accumulated between the ice and the adjacent valley wall and 

on top of the ice. Those sediments that were supported by the 

ice were laid down (often chaotically) as the ice melted. Kame 

deposits are commonly present in most places along the sides 

(kame terraces) and in some places in the central parts of the 

Dryden Lake Valley (fig. 6).
Geology 21

Kame end-moraine deposits consist of ice-contact 

deposits (poorly sorted and consist of silt, sand, and gravel) 

and, in some places, till. These end moraines form one or 

more of the following landforms (1) linear or arcuate ridges; 

(2) complex accumulations of mounds, knobs, hummocks; 

or (3) belts of both types of landforms. The sediments were 

deposited at or near a stagnating glacial ice margin. In the 

study area, kame end-moraine deposits are found at the 

terminus of the Valley Heads Moraine in the southern part of 

the Dryden Lake Valley and in the eastern part of the Virgil 

Creek Valley (fig. 6). The deposits that formed kame-end 

moraines were initially laid down as well-stratified sediments 

on top or adjacent to ice but, as the ice that supported the 

sediments melted, the sediments collapsed chaotically and the 

sediments became poorly stratified and often ended up dipping 

steeply at various angles of repose. Thus, the kame-endmoraine deposits commonly have highly variable stratification 

and contain lenses of sediments with little continuity.

Recent (postglacial) deposits consist of alluvium 

deposited by recent streams, lake sediments that were 

deposited in Dryden Lake, and peat and muck that were 

deposited in some wetlands and kettles (depressions formed 

where blocks of ice that became partially or entirely buried 

by sediment). Alluvium includes coarse sand and gravel 

deposited in channels and fans, and silt and fine to medium 

sand deposited as overbank sediments in floodplains.

Southern Part of Study Area

The prominent surficial geologic features in the southern 

part of the study area (from the southern boundary of the study 

area to the north end of Dryden Lake) include (1) alluvium 

overlying outwash interbedded with till units in the Owego 

Creek Valley, (2) a kame moraine (Valley Heads Moraine) that 

forms the drainage divide between the Susquehanna River and 

Great Lakes basins, and (3) a large kettle lake (Dryden Lake) 

that is underlain by several till and sand-and-gravel units 

(figs. 6 and 13).

The Valley Heads Moraine was formed during 

a readvance of ice during the Port Bruce stade about 

15,500 years BP (Muller and Calkin, 1993). At that time, 

the main ice sheet abutted against the northern rim of the 

Portage escarpment (fig. 4) and a tongue of ice intruded 

several miles southward into the north-draining Virgil Creek 

and Dryden Lake Valleys. The moraine is part of the most 

extensive moraine system in New York State, which forms a 

roughly 240-mi-long ridge across central and western New 

York (fig. 2). The landforms at the moraine include terminal 

moraine ridges and ice-disintegration features such as kame 

terraces, hummocky knobs and kettles (kames), and channels 

carved by postglacial streams.

Meltwaters that flowed south from the Valley Heads 

Moraine deposited an outwash plain in the Owego Creek 

Valley that has subsequently been covered by a veneer of 

recent alluvial sediments (fig. 6). Near the Valley Heads 

Moraine, the outwash consists of coarse sand and gravel that 

is interlayered with two till units (fig. 13), which suggests that 

the ice had surged twice past the main crest of the moraine 

and into the outwash plain. However, the southernmost extent 

of the till layers is unknown because they extend beyond the 

southern limit of the study area.

Dryden Lake occupies a large kettle in the central part 

of the Dryden Lake Valley (figs. 6 and 13). Sand and gravel 

deposited by meltwaters between the valley wall and the 

block of ice were subsequently laid down as the supporting 

ice melted. These collapsed sediments formed kame moraine 

deposits (fig. 6) that drape downward toward the central part 

of the valley and extend beneath Dryden Lake.

The preglacial surface-water divide between the St. 

Lawrence River Basin and the Susquehanna River Basin was 

a former preglacial bedrock col in the Owego Creek Valley 

about 4 mi south of the study area. The area of the former 

bedrock col coincides with an upland region with hilltops 

of slightly higher altitude than the surrounding area (figs. 3 

and 4). The bedrock col was removed by glacial erosion and 

became covered by glacial drift. The present surface-water 

divide is formed by the Valley Heads Moraine (a subtle ridge 

that loops across the valley) and an alluvial fan deposited by 

Daisy Hollow Brook (geologic unit alf/km/t; fig. 6).

The result of a seismic-refraction survey along Purvis 

Road, which crosses the Valley Heads Moraine, indicated that 

the unconsolidated deposits are greater than 400-ft thick in the 

south-central part of the Dryden Lake Valley (figs. 10A, B). 

Well records indicate that the upper part of the moraine (upper 

100 to 150 ft) comprises layers of kame sand and gravel; till; 

and glaciolacustrine fine sand, silt, and clay.

In the southern part of the Dryden Lake Valley, the 

stratigraphy is mostly unknown because there are no wells 

that extend to the deep zones of the valley fill. However, basal 

confined sand and gravel aquifers are typically present on 

top of bedrock at the Valley Heads Moraine in other major 

valleys across central New York (Wellner and others, 1996; 

Miller and others, 1998; Yager and others, 2001; Kappel and 

Miller, 2003, 2005), and it is reasonable to assume that there 

is a basal confined aquifer underlying the southern part of this 

study area also. Well C57 (fig. 8) and several other wells (not 

shown in map) near the hamlet of Harford (0.9 mi south of the 

study area, fig. 8) were reported to have been drilled to depths 

about 200 ft each and were finished in sand or sand and gravel, 

which suggests that the deep confined aquifer extends south 

beyond the study area.

Northern Part of Study Area

The prominent surface geologic features in the northern 

part of the study area (from Dryden Lake to the northern 

boundary of the study area, fig. 13) include alluvium, ground 

moraine (till), and kames (figs. 6 and 13). All these surficial 

deposits overlie buried units of sand and gravel, till, and 

glaciolacustrine deposits (fig. 13). In the floodplains of the 

outlet to Dryden Lake and of Virgil Creek (west of the Virgil 

Creek Dam), there is 5 to 20 ft of alluvium that overlies till 
22 Geohydrology, Water Quality, and Simulation of Groundwater Flow, Town of Dryden, Tompkins County, New York

Figure 13. Longitudinal geologic cross-section A–A′ in the Virgil Creek and Dryden Lake Valleys, Town of Dryden, New York. Location 

of line of section shown on figure 8. (Available separately at http://pubs.usgs.gov/sir/2013/5070/pdf/sir2013-5070_miller_fig13_11x17.pdf) Dryden Lake outlet

Approximate bedrock surface in the center (thalweg) of the valley

EXPLANATION

Water

Alluvium

Unclassified sand and gravel (lower confined aquifer)

Unclassified sand and gravel (middle confined aquifer)

Unclassified sand and gravel (upper confined aquifer)

Lacustrine silt and clay 

Till and lacustrine silt and clay 

Till 

Kame sand and gravel

Kame moraine (Valley Heads Moraine)

0 10,000 

1,250

1,200

1,150

1,100

1,050

1,000

950

900

800

750

700

850

TM 214

TM 207, TM1046

TM 187

TM 172

TM 163

TM2724

TM2081, TM1676

TM1007 (projected)

TM 993

TM 198 (projected)TM 195 (projected)

TM1695,

TM1699,

TM1700

Dryden L

(kettle la

BEND INSECTION

BEND INSECTION

BEND INSECTION

BEND INSECTION

NORTHWEST

FEET

Virgil Creek

VERTICAL EXAGGERATION X 10

Datum is North American Vertical Datum of 1988

Horizontal distanc

A 

TM 1011

Northern part of study area 
Geology 23

Figure 13. Longitudinal geologic cross-section A–A′ in the Virgil Creek and Dryden Lake Valleys, Town of Dryden, New York. Location of line 

of section shown on figure 8.—Continued

fer)

ifer)

fer)

Bedrock (shale and siltstone)

TM12724

Well and well number— Number is assigned 

by U.S. Geological Survey. Well data are in appendix 

at end of report

20,000 30,000

1,250

1,200

1,150

1,100

1,050

1,000

950

900

800

750

700

850

TM1007 (projected)

TM1010 (projected)

TM2571 (projected)

TM1005

TM 993

Dryden Lake

(kettle lake)

C 75

C 44

SECTION

SEISMIC

SECTION A-A’

SOUTHEAST

Bogs

rizontal distance, in feet

A’ 

Valley Heads Moraine

Southern part of study area
24 Geohydrology, Water Quality, and Simulation of Groundwater Flow, Town of Dryden, Tompkins County, New York

(fig. 13). However, in the floodplain of Virgil Creek east of 

the Virgil Creek Dam, the creek has removed the surficial till 

layer and deposited a thin layer of recent alluvium overlying 

kame sand and gravel (fig. 14). Records of test wells and 

borings at the dam indicate that the stratified-drift deposits are 

100- to 150-ft thick in this area and consist of three sand and 

gravel units that are interlayered with relatively impermeable 

units (having low hydraulic conductivity) such as till and 

glaciolacustrine fine-grained sediments (very fine sand, silt, 

and clay).

In the areas above the Virgil Creek floodplain and on the 

backside (northwest) of the Valley Heads Moraine, ground 

moraine (till) and kame deposits are present at or near land 

surface (fig. 6). The uppermost till is underlain by at least 

three extensive sand and gravel units that form confined 

aquifers bounded between relatively impermeable till and 

glaciolaustrine units (fig. 13). The multiple till units suggest 

that the ice front of the glacier had oscillated back and forth in 

this area.

The well log of TM 993 (fig. 15; location shown in figs. 8 

and 13), a 234-ft-deep test well in the NYSDEC parking lot at 

the north end of Dryden Lake, indicates that the upper 105 ft 

of deposits consists of a surficial till that overlies a lacustrine 

unit, which in turn overlies at least two thin sand and gravel 

units. Below a depth of 110 ft, there is a 67-ft-thick confining 

unit consisting of lacustrine silt, clay, and till that overlies 

a more than 68-ft-thick coarse sand and gravel unit (177 to 

245 ft below land surface).

The well log of TM2724 (fig. 16; location shown in 

figs. 8 and 13), a 229-ft-deep test well, located 300 ft north 

of Keith Lane and along the Jim Schug trail, penetrated 

three major sand and gravel units (40–52 ft, 69–106 ft, and 

152–187 ft below land surface), several minor sand and 

gravel units interlayered with confining units consisting of till 

and glaciolacustrine sediments, and bedrock at 218 ft below 

land surface. The three major sand and gravel units probably 

correlate with the three sand and gravel units encountered in 

test well TM 993 near Dryden Lake (fig. 13). The minor sand 

and gravel units encountered in test well TM2724 above the 

bottom major sand and gravel unit are probably discontinuous 

lenses that do not form extensive aquifers.

Logs for test wells TM1695, TM1699, and TM1700 at 

the Village of Dryden Lake Road pumping station indicate 

that the wells were drilled to depths of 396 ft, 72 ft, and 41 ft, 

respectively (fig. 9; locations shown on figs. 8 and 13). Well 

TM1695 penetrated interbedded till and sand and gravel 

units in the upper 108 ft, mostly glaciolacustrine fine sand, 

silt, and clay from 108 to 387 ft, and bedrock at 387 ft below 

land surface. At the Village of Dryden South Street pumping 

station, a now-abandoned well (TM 207) and a production 

well operating since 1986 (TM1046) (fig. 17; locations shown 

on figs. 8 and 13) penetrated a confined sand and gravel 

aquifer between depths 155 ft and 185 ft and possibly one or 

two minor shallow confined sand and gravel units, but they 

were deemed unsuitable for finishing as production wells for 

municipal purposes. There are few subsurface data northwest 

of the Village of Dryden (northwest of the boundary of the 

study area). Therefore subsurface geologic conditions there 

are unknown.

Geohydrology of the Stratified-Drift 

Aquifer System

Characterization of the stratified-drift aquifer system 

in the Virgil Creek and Dryden Lake Valleys in the Town of 

Dryden, Tompkins County, and in part of the Owego Creek 

Valley, Town of Harford, included describing the (1) aquifer 

type (confined or unconfined), (2) aquifer framework, and 

(3) groundwater-flow system, including water levels and 

recharge and discharge conditions. Because drilling more than 

a few wells was beyond the scope of this study, most data used 

to characterize the geologic framework of the aquifers were 

obtained from existing well records. Many of the wells used in 

this study are within the central part of the study area, where 

the density of self-supply wells is higher; however, attempts 

were made to characterize the southern and northern parts of 

the aquifer system using available well logs, water-level data, 

and correlations made from seismic data. The locations of 

wells used to characterize the stratified-drift aquifer system 

are shown on figure 8, and well records are presented in 

appendix 1.

The major aquifers in the study area are confined. 

However, there are several thin, discontinuous unconfined 

aquifers as well. Because unconfined aquifers are thin, 

discontinuous, and are tapped by few wells, this report 

concentrates on the three more extensive confined aquifers 

in which most wells are finished. A confined aquifer (also 

known as an artesian aquifer) is bounded between confining 

layers and is composed of sediments of sufficient permeability 

that it is able to store and yield usable amounts of water to 

wells. In a confined aquifer, the potentiometric surface is, by 

definition, always above the top of the permeable sediments 

in which the water is stored and transmitted. When a confined 

aquifer is tapped by a well, water in the casing is forced up 

to its potentiometric altitude. If the hydraulic pressure in the 

confined aquifer is great enough, it may cause the water in 

the well to flow above land surface, in which case the well is 

referred to as a flowing artesian well.

Confining layers are made up of sediments with low 

permeability (low hydraulic conductivity) that prevent 

groundwater from rapidly moving through them. In the 

study area, the confining layers consist of fine-grained 

glaciolacustrine sediments (clay, silt, and very fine sand) 

and till.

An unconfined aquifer comprises sediment of sufficient 

permeability that can store and yield usable amounts of water 

to wells. In an unconfined aquifer, the water table is at or near 

atmospheric pressure and is the upper boundary of the aquifer.
Geohydrology of the Stratified-Drift Aquifer System 25

Figure 14. Geologic section B–B′ at the Virgil Creek Dam, Town of Dryden, New York. Location of line of section shown on figure 8.

1,050

1,100

1,150

1,200

1,250

1,300

VERTICAL EXAGGERATION x10

Datum is North America Vertical Datum of 1988

FEET

0

0 50

250 500 FEET

100 METERS

TM1034

TM1032

TM1031

TM1030

TM 997

Virgil

Creek 

B B’

SOUTH NORTH Seismic-refraction 

survey in Virgil Creek 

floodplain

Till Till

Sand and gravel

Sand and gravel

Glaciolacustrine silt and clay

Glaciolacustrine silt and clay

Seismic-refraction 

survey in spillway

channel

Berm

Lake sediments eroded

(backfilled by gravel)

Original till surface.

Till was eroded by Virgil Creek 

during post-glacial period

(present site of Virgil Creek

dam)

Till

Till

Sand and gravel

Glaciolacustrine silt

and clay

Bedrock 

(Shale and siltstone)

Bedrock 

(Shale and siltstone)

EXPLANATION

Surficial geologic units

TM1032

Well and well number—Number is assigned 

by U.S. Geological Survey. Well data are in 

appendix at end of report

Water

Alluvium

Till 

Glaciofluvial sand and gravel

Glaciolacustrine silt and clay

Bedrock (shale and siltstone)
26 Geohydrology, Water Quality, and Simulation of Groundwater Flow, Town of Dryden, Tompkins County, New York

Figure 15. Well log and well construction details of U.S. Geological Survey test well TM 993 at the New York State Department of 

Environmental Conservation boat access facility at Dryden Lake, in the Town of Dryden, New York. Location shown on figure 8.

1,092

922

1,071

1,027

1,068

1,062

1,057

990

1,102

1,112

1,127

Developed well 2 hours at a pumping rate of 200 gallons per minute (12/9/04)

Pumped well at a rate of 45 gallons per minute for 1 hour, drawdown = 0.8 feet 

(12/13/04).

Refusal at 234 feet where a 4-foot diameter boulder was encountered.

Casing ends at 234 feet, uncased borehole was drilled through boulder to 

depth 245 feet. A thick sequence of coarse sand and gravel extends from 

177 to 245 feet.

Bottom of casing = 234 feet

0

2

40

55

65

75

96

99

105

110

140

177

245 922

1,071

1,027

1,068

1,062

1,057

990

Coarse sand and gravel, grey brown, fine to coarse clasts, subround 

to round clasts, highly permeable, clasts mostly grey shale, some green 

shale, trace red sandstone, white sandstones, and crystallines

Four foot diameter boulder (green crystalline) from 234 to 238 feet

Silt, greenish grey, massive, no stones, with 1/32

inch thick clay seams, horizontal bedding

Silt and clay, grey

Clay, grey, with stones (may be till or lacustrine with dropstones)

Sand and gravel, makes a little water ~ 1 gpm

Sand and gravel

Clay, grey

1,102

1,112

Very fine and fine sand, grey, some pebbles

Sand and gravel, grey, fine to coarse pebbles

Clay, grey, soft

Silty clay, grey

Gravel fill

1,127

1,166.53 Water level = 2.77 feet

below land surface

(altitude. = 1,163.76 feet),

12/13/2004

Groundwater level is

7.41 feet higher than 

Dryden Lake (altitude 

Dryden Lake =

1,156.35 feet)

Site name: TM 993 (well depth = 234 ft)

Site ID: 422755076164801

Latitude: 42° 27' 55.23''

Longitude: 076° 16' 47.92''

Date completed: 12/9/04

6-inch- diameter steel casing

Casing above ground = 4.3 feet 

Altitude top of 

6-inch casing

= 1,170.83 feet

Till, greyish brown, silty clay matrix, trace fine pebbles, dense, compact

Altitude relative to National 

Geodetic Vertical Datum of 1929

Drilling contractor: Barber & Deline, Tully, NY 

Depth below land surface, in feet
Geohydrology of the Stratified-Drift Aquifer System 27

Figure 16. Well log and well construction details of U.S. Geological Survey test well TM2724, on the Jim Schug trail near Keith 

Lane Road, Town of Dryden, New York. Location shown on figure 8.

1,144

1,139

1,128

1,118

1,108

1,096

1,088

1,079

1,063

1,042

1,026

1,020

1,115

1,060

1,135

953

941

930

919

996

961

Sand and gravel, fine to coarse pebbles, fine to coarse 

sand, subround to round clasts, makes some water

Coarse sand and gravel, fine to coarse pebbles, 

medium to coarse sand, makes >100 gallons per minute,

artesian flow, water level 7 feet above land surface

Coarse sand and gravel, fine to coarse pebbles, 

medium to coarse sand, makes 50 to >100 gallons

per minute

Shale, dark grey, makes little or no water

1,144

1,1448

1,139

1,128

1,118

1,108

1,096

1,088

1,079

1,063

1,042

1,026

1,020

1,115

1,060

1,135

953

941

930

919

0

4

Depth below land surface, in feet

60

52

40

33

30

20

13

9

88

85

69

106

 122

 128

 152

187

195

207

218

229

Water level was approximately

8 feet above land surface at 

casing depth175 feet on 

12/15/2009. Altitude water 

level = 1,156 feet

Casing driven 

11 ft into bedrock

TM2724

Altitude top of

6-inch casing 

= 1,151.93 feet

Very fine sand and silt coarsening with depth to

medium to coarse sand

Clay, grey

Interbedded grey till and sand and gravel

Till, grey, stony, with silt clay matrix

Till, grey, stony, with silt clay matrix

Till, grey, stony, with silt clay matrix

Silty sand and gravel, makes little water

Till, grey, stones embedded in sand and silt matrix

Till, grey, stones embedded in sand and silt matrix

Clayey silt and very fine sand, heaves up casing

Silt and clay, grey

Sand and gravel, makes some water

Cobble fill

Cinder fill (railroad bed material)

Sand and gravel, recent alluvium

Coarse sand and gravel, fine to coarse pebbles, 

medium to coarse sand, makes some water

Coarse sand and gravel, fine to coarse pebbles, 

medium to coarse sand, subround-round clasts

makes 75 to >100 gallons per minute. Under artesian flowing 

conditions, static water level 8 feet above land surface 

Bottom of

casing = 229 ft

Artesian flow at zones 

69 to 106 and 152 to 187 ft

996

961

Site name: TM2724 (well depth = 229 feet)

Site identifier: 422812076172201

Latitude: 42° 28' 11.64''

Longitude: 076° 17' 22.10''

Date completed: 12/16/2009

6-inch-diameter steel casing

Casing above ground = 3.6 feet

Drilling contractor: Barber & Deline, Tully, NY 

]

Altitude relative to National 

Geodetic Vertical Datum of 1929
Figure 17. Well logs and well construction details of A, abandoned well TM 207 and B, production well TM1046 at the South Street pumping station, 

Abandoned well TM 207 is used as an observation well and is equipped with a water level recorder. Locations shown on figure 8.

1,0851,0671,035

984975956943929913908

1,0231,018

923917

1,008

978

941931

1,0301,077

Silty fine sandClayey silt with layers of fine sandSilty fine sand

Sand and gravel with some silty and clayey zones, grey

Grey clayey siltSilty fine sandSilty sand and gravel, grey

1,025

Srceened from 169 to 175 feet

12-inch diameter casing to 120 feet

6-inch diameter casing to 169 feet

0

2124

0

13

3163

114123142155169173185190194

68 68758090

120157167175181

Depth below land surface, in feet 1,020

925919

1,010

980

943933

1,032

Clay, grey

Sand and gravel 1,079

1,099.5

Artesian flowing well,

water level = 25 feet

above land surface

during nonpumping

conditions

(altitude 1,123 feet)

Date: 8/18/1949

Site name: TM 207 (well depth = 178 feet)Site ID: 422905076144901Latitude: 42o 29’ 05”

Longitude: 076o 14’ 49”

Date completed: 8/18/1949Drilling contractor: Cranston Water6-inch diameter steel casingCasing above ground = 2.5 feet

Site name: TM1046 (well depth = 180 feet)Site ID: 422906076174801Latitude: 42o 29’ 06”

Longitude: 076o 14’ 48”

Date cWell d12-incCasing 

Altitude top of 

6-inch diameter 

casing = 1,101.97 feet

Altitud

12-inch 

casing= 1,

Till (clay, gravel, and sand )Sand and gravel, water Clay and siltSand and gravelSand, gravel, cobbles, and clay

Lacustrine silt and clayTill (clay, sand, gravel, and cobbles), blue

}

Till (clay, sand, gravel, and cobbles)Till (clay, sand, and gravel)

Silty sand and gravel (alluvium)

Till (grey silt, some sand and gravel)Till (silty clay with some sand and gravel)Till (clayey silt with some sand, gravel, and cobbles)Gravelly silt (dirty sand and gravel or till)Fine sand with some silt

} 

1,085

1,098.5

1,0671,035

984975956943929913908

Altitude relative to National 

Geodetic Vertical Datum of 1929

Altitude relative to National 

Geodetic Vertical Datum of 1929

A B
Geohydrology of the Stratified-Drift Aquifer System 29

Aquifer Geometry

The stratified-drift aquifer system in the study area 

contains three extensive and continuous confined sand 

and gravel aquifers and several small and discontinuous 

unconfined and confined aquifer units (figs. 18 and 19). Most 

wells in the study area tap the three confined aquifers. The 

discontinuous unconfined and confined aquifer units are of 

local extent and are tapped by only a few wells.

Unconfined Aquifers

Except for locally thick unconfined alluvial deposits 

in the Virgil Creek floodplain west of the Virgil Creek Dam 

(fig. 19), there are only small discontinuous patches of kame 

sand and gravel or surficial alluvial deposits (fig. 18) that form 

unconfined aquifers. However, most of these deposits are 

thinly saturated or only seasonally saturated. Therefore, these 

minor aquifers generally are not tapped by wells in the study 

area. These unconfined aquifers include the alluvial Virgil 

Creek floodplain east of the Virgil Creek Dam, kame terraces 

along the valley walls, kame and kame moraine deposits, and 

the alluvial fan complex in the Owego Creek Valley south 

of the Valley Heads Moraine (fig. 6). The dam, completed in 

1998, is used for flood control purposes and does not contain 

water except during high storm-runoff events.

Confined Aquifers and Confining Units

There are three extensive and continuous confined 

sand and gravel aquifers in the study area. These aquifers 

are designated in this report as the upper, middle, and lower 

confined aquifers and are confined by units that have low 

hydraulic conductivity, such as till and lacustrine clay, silt, 

and very fine sand. Most wells in the study area, including 

the production wells for the Village of Dryden, are finished in 

these aquifers.

The upper confined aquifer typically lies 20 to 45 ft 

below land surface and ranges in thickness from 5 to 10 ft, 

but locally it can be as much as 65 ft thick (fig. 18). The 

upper confined aquifer is typically the thinnest of the three 

confined aquifers. The upper confined aquifer underlies a 

thin till confining unit (5 to 20 ft thick) in the northern and 

southern parts of the study area and underlies a thicker till and 

lacustrine silt and clay confining unit (combined thickness 

of 20 to 50 ft) in the central part of the study area (fig. 13). 

Many domestic wells tap the upper aquifer in the central part 

of the study area, as do two Village of Dryden municipal 

wells (TM 202 and TM 204) at the Lake Road well field in the 

northern part of the aquifer (fig. 8).

The middle confined aquifer typically lies from 70 to 

100 ft below land surface and ranges in thickness from 10 

to 15 ft. Locally the aquifer can be as much as 60 ft thick 

(fig. 18). The middle confined aquifer is confined above and 

below by 10 to 40 ft of till throughout the study area (fig. 13). 

Most homeowner wells are finished in the middle confined 

aquifer, as is the Village of Dryden municipal well TM 981 

at the Jay Street pumping station, in the northern part of the 

aquifer (fig. 8).

The lower confined aquifer typically lies from 150 to 

250 ft below land surface. The aquifer ranges in thickness 

from 15 to 25 ft in the northern part of the study area but 

can be more than 50 ft thick in the central part of the study 

area (fig. 18). The extent and thickness of the lower confined 

aquifer are mostly unknown in the southern part of the study 

area because of the lack of deep subsurface data there (fig. 13). 

The lower confined aquifer is confined above by 50 to 80 ft of 

till and lacustrine sediments and is confined below by mostly 

fine-grained lacustrine deposits or low-permeability bedrock 

(fig. 13). The lower confined aquifer is tapped by several 

domestic wells and one Village of Dryden municipal well 

(TM1046 at South Street; figs. 8, 13, and 17).

Bedrock

Generally, water-well drillers do not drill wells more 

than 300 ft deep into bedrock because well yields typically 

decline, and the water typically becomes increasingly more 

mineralized and less potable with increasing depth. Well yields 

generally decline with increasing depth because the density, 

width of openings, and connectivity of water-bearing fractures 

decrease with depth as a result of the diminishing effects of 

weathering and the increasing weight of overlying rock which 

results in fewer, less-open, and less-connected fractures. In 

the southern part of Tompkins County, records from waterwell drillers indicate that 2 to 5 gallons per minute (gal/min) 

typically can be obtained from wells that tap Devonian-age 

sedimentary rocks at most locations, and locally, yields as 

large as 10 to 30 gal/min or as small as less than 1 gal/min are 

obtained (Miller, 2009).

Groundwater Recharge

Recharge is replenishment of water to an aquifer. 

The amount of recharge to an aquifer is important in the 

determination of the long-term availability of groundwater. 

Recharge to confined aquifers is limited because the 

unconfined aquifers are surrounded in large part by confining 

units and typically have only a small portion of the aquifer 

open to the atmosphere that can readily accept recharge 

directly from precipitation. Conversely, recharge is readily 

available to unconfined aquifers because all of the aquifer is 

open to the atmosphere and thus recharge from precipitation 

and losing streams is easier to estimate than in confined 

aquifer settings. The distribution and amount of recharge in the 

study area varies from place to place; the amount of estimated 

recharge used for the input into the numerical groundwaterflow model is discussed in the Boundary Conditions section of 

this report.
30 Geohydrology, Water Quality, and Simulation of Groundwater Flow, Town of Dryden, Tompkins County, New York

Figure 18. Geohydrology across longitudinal geologic cross-section A–A′ in the Virgil Creek and Dryden Lake Valleys, Town of Dryden, 

Tompkins County, and in headwaters of Owego Creek, Town of Harford, Cortland County, New York. Location of line of section shown on 

figure 8. (Available separately at http://pubs.usgs.gov/sir/2013/5070/pdf/sir2013-5070_miller_fig18_11x17.pdf) Dryden Lake outlet

1,250

1,200

1,150

1,100

1,050

1,000

950

900

800

750

700

850

NORTHWEST

FEET

BEND INSECTIONBEND INSECTIONBEND INSECTIONBEND INSECTION

0 10,000 

VERTICAL EXAGGERATION X10

Datum is North America Vertical Datum of 1988

Horizontal distance

Approximate bedrock surface in the center (thalweg) of the valley

EXPLANATION

Alluvium

Lower confined aquifer (sand and gravel)

Middle confined aquifer (sand and gravel)

Upper confined aquifer (sand and gravel)

Upper confined aquifer

Confining units (till and lacustrine very fine sand 

silt and clay)

Kame sand and gravel

Kame moraine (Valley Heads Moraine)

Extensive confined aquifer and confining units Discontinuous unconfined aquifer units (some units 

may be only seasonally saturated

Lower confined a

TM 214

TM 207, TM1046

TM 187

TM 172

TM 163

TM2724

TM2081, TM1676

TM1007 (projected)

TM 993

TM 198 (projected)TM 195 (projected)

TM1695,

TM1699,

TM1700

Dryden L

(kettle la

Virgil Creek

A 

TM1011

These small patches of sand and gravel

(not modeled) have little or no

saturation.

Northern part of study area 
Geohydrology of the Stratified-Drift Aquifer System 31

Figure 18. Geohydrology across longitudinal geologic cross-section A–A′ in the Virgil Creek and Dryden Lake Valleys, Town of Dryden, 

Tompkins County, and in headwaters of Owego Creek, Town of Harford, Cortland County, New York. Location of line of section shown on 

figure 8.—Continued

SECTION

SEISMIC

SECTION A−A’

30,000

1,250

1,200

1,150

1,100

1,050

1,000

950

900

800

750

700

850

SOUTHEAST

20,000 

orizontal distance, in feet

ATION

Water

Bedrock (shale and siltstone)

TM12724

Well and well number- number is assigned 

by U.S. Geological Survey. Well data are in appendix 

at end of report

 units 

Middle confined aquifer

Lower confined aquifer

TM1007 (projected)

TM1010 (projected)

TM2571 (projected)

TM1005

TM 993

Dryden Lake

(kettle lake)

C 75

C 44

Bogs

A’ 

Valley Heads Moraine

Southern part of study area
32 Geohydrology, Water Quality, and Simulation of Groundwater Flow, Town of Dryden, Tompkins County, New York

Figure 19. Geohydrology across geologic cross-section B–B′ at the Virgil Creek Dam, Town of Dryden, New York. Location of line of 

section shown on figure 8.

1,050

1,100

1,150

1,200

1,250

1,300

VERTICAL EXAGGERATION x10

FEET

0

0 50

250 500 FEET

100 METERS

TM1034

TM1032

TM1031

TM1030

TM 997

Datum is North America Vertical Datum of 1988

Virgil

Creek 

B B’

SOUTH NORTH

Berm

Upper and middle aquifers

unconfined beneath Virgil

Creek floodplain

Confining unit (till) 

eroded by 

Virgil Creek 

Bedrock 

(shale and siltstone)

Bedrock 

(shale and siltstone)

EXPLANATION

Unconfined aquifer and confining units

Confined aquifer and confining units

Water

TM1032

Well and well number—number is assigned 

by U.S. Geological Survey. Well data are in appendix 

at end of report

Bedrock (shale and siltstone)

Lower confined aquifer (sand and gravel)

Middle confined aquifer (sand and gravel)

Upper confined aquifer (sand and gravel)

Unconfined aquifer (sand and gravel)

Confining units (till and lacustrine very fine 

sand, silt, and clay)
Geohydrology of the Stratified-Drift Aquifer System 33

Unconfined Aquifer

In general, the principal sources of recharge to 

unconfined aquifers in the study area are (1) direct 

infiltration of precipitation (rain and snow melt) at land 

surface, (2) unchanneled surface and subsurface runoff and 

groundwater inflow from till and bedrock of adjacent upland 

areas, (3) leakage from tributary streams and from Virgil 

Creek in the vicinity of the Virgil Creek Dam (fig. 19), and 

(4) upward leakage from the underlying fine-grained confining 

units (fig. 20). Over areas of sand and gravel, surface runoff 

is generally negligible; therefore, precipitation that is not 

lost to evapotranspiration recharges the unconfined aquifer. 

Unchanneled upland runoff and groundwater inflow from till 

and bedrock typically contribute about 20 percent of the total 

recharge to unconfined stratified-drift aquifers in central New 

York (Miller and others, 1998, 2008; Kontis and others, 2004). 

Recharge from seepage losses in tributary streams is a minor 

source of recharge to the aquifers in this study area because 

most of the major aquifers are confined.

In the Virgil Creek Dam area (the dam normally allows 

creek water to pass without restriction and only holds back 

water during high storm-runoff events), erosion by Virgil 

Creek has cut a 40-ft-deep gorge into the Valley Heads 

Moraine (fig. 19). Test wells TM 997 and TM 998 (fig. 11) 

were drilled at the dam during this study to determine 

(1) whether the upper confining unit had been removed 

by this erosion (thus creating a window where part of the 

upper confined aquifer has become exposed at land surface, 

forming a local unconfined aquifer) and (2) the hydraulic-head 

relation between the stream and aquifer. In unconfined aquifer 

settings, streams are hydraulically connected to the aquifer 

and the hydraulic-head relation between the water level in 

the aquifer and in the stream determines whether the stream 

gains (receives groundwater discharge) or loses (recharges the 

aquifer) water to the aquifer.

Results of the test drilling indicate that the upper 

confining unit (till) was missing at the dam (figs. 11, 14, and 

19) and that there was an unconfined sand and gravel aquifer 

at depths from 0 to 48 ft in the floodplain of Virgil Creek 

(figs. 11, 14, and 19). On November 11, 2005, the water level 

in Virgil Creek was measured and found to be 2.3 ft higher 

than the groundwater level in well TM 998 (well depth of 37 ft 

and finished in the unconfined aquifer, fig. 11), which indicates 

that the stream probably loses water and therefore recharges 

the aquifer. The higher head in the stream than in the aquifer 

may be a result of a series of unlined stream-drop structures 

that were constructed behind the dam for erosion-control 

purposes, and the stream may lose water only close to the 

dam. There were no streamflow measurements made in Virgil 

Creek before the dam was constructed to determine whether 

the stream lost water before it was constructed. To determine 

the amount of stream loss, a set of seepage measurements was 

made in Virgil Creek on May 10, 2007, at a time of average 

annual base flow. The results of the stream measurements 

indicated that the stream lost 1.2 cubic feet per second (ft3

/s) 

(0.78 million gallons per day (Mgal/d)) of water in the reach 

from 1,200 ft upstream from the dam to 220 ft downstream 

from the dam (fig. 12A).

Confined Aquifers

The confined aquifers in the study area are surrounded 

by fine-grained sediments of low hydraulic conductivity that 

impede or slow infiltration of water (recharge) from surface 

sources to the aquifer. In most of the study area, the sources 

of recharge were difficult to identify and amounts of recharge 

were difficult to quantify because the aquifers are overlain 

by confining units and the hydraulic properties, such as 

hydraulic conductivity, are not known. Therefore, the recharge 

conditions in most of the study area are approximated (fig. 20). 

However, one area was an exception: the Virgil Creek Dam 

area described above.

In the northern part of the Dryden Lake Valley, well 

records indicate that the confining units are continuous and 

extensive. Therefore, the confined aquifers receive recharge 

mostly by slow seepage of water through the fine-grained 

drift (till and glaciolacustrine very fine sand, silt, and clay) 

that surround them. Locally along the sides of the valley, the 

confined aquifers either may extend up along the flank of 

the bedrock valley wall, becoming unconfined where they 

crop out at land surface, or are overlain and in contact with 

surficial coarse-grained kame sand and gravel deposits that 

constitute an avenue through which direct precipitation and 

seepage losses from tributary streams (fig. 20A) can enter the 

aquifer. Seepage from adjacent fine-grained sediment may 

be substantial in the vicinity of the large pumping wells for 

the Village of Dryden. Large pumping withdrawals lower 

the water levels and increase the vertical hydraulic gradients 

in the confining units resulting in substantial amounts of 

water flowing through confining layers and into the aquifers 

(fig. 20A). In areas distal from the municipal pumping wells 

and where the confined aquifers are mostly isolated and 

completely surrounded by low-permeability material, the rates 

of flow through the confining units are lower than in proximity 

to pumping wells. Although the rates of flow through 

confining units that are distal from pumping wells are small, 

substantial total amounts of water flow through these units 

and into aquifers because the confining units extend over large 

areas. In this study area, the most isolated confined aquifer is 

the lower confined aquifer.

Most recharge to the confined aquifers occurs at the 

Valley Heads Moraine and outwash plain in the southern 

part of the study area (fig. 6) where there are many icedisintegration features and deposits (kame and kettle 

topography). In this area, the stratigraphy is chaotic because 

the ice surged back and forth and sediments that were on top 

or adjacent to ice collapsed as ice melted. The confining units 

(till) are likely to consist of heterogeneous material (reworked 

sand and gravel mixed with till) and locally to contain 

windows of permeable sediment that can readily transmit 

recharge from precipitation and tributaries that lose water as 
34 Geohydrology, Water Quality, and Simulation of Groundwater Flow, Town of Dryden, Tompkins County, New York

Figure 20. Sources of recharge to aquifers in A, the northern part of the study area and B, the southern part of the study area, 

Tompkins and Cortland Counties, New York.

3

7

9

Southern part of study area—thin unconfined alluvial unit and three extensive and 

continuous confined aquifers

Northern part of the study area—thin alluvial and small kame unconfined 

units and three extensive and continuous confined aquifers

7

7

5

8

Headwater

stream

5

10

2

3

4

4

4

6

6

6

6

Village of

Dryden 

municipal 

production 

wells

7 7 10

Not to scale

Not to scale

B

Edge of valley-fill deposits.

2

7

8

1

Some groundwater seeps into confined aquifers from the 

over- and underlying-confining units, especially where large 

withdrawals increase the vertical gradient into the aquifer.

Lateral contact between fine-grained stratified drift and till 

or bedrock. Groundwater flow across this contact is small. 

Some leakage from till and bedrock along the valley 

walls and valley bottom recharges the confined aquifers. 

In most places, little or no water recharges the confined 

aquifer from streams flowing across the fine-grained 

deposits in the main valley except in the vicinity of the 

Village of Dryden municipal well (TM 204) that taps the 

upper aquifer and is near Virgil Creek—withdrawals from 

this shallow aquifer lower the water levels enough to 

induce recharge from the overlying confining unit and, 

subsequently, from the overlying stream. 

Recharge from precipitation that falls directly over valleyfill sediments.

Water table in the valley-fill deposits.

Confining units may be locally interrupted by "windows" of 

permeable sediment that can readily transmit recharge from 

precipitation and tributaries that lose water as they flow over 

the valley floor. 

4

5

6

10

In areas where the hydraulic head is higher in the underlying 

units than in the surficial alluvium, some groundwater moves 

upward and recharges the surficial alluvium. 

9

3

EXPLANATION

Shale and siltstone

Water table

Fine-grained sediments (lacustrine

fine sand, silt and clay; and till)

Thin alluvial sand and gravel

Upper confined sand and gravel 

aquifer

Middle confined sand and gravel 

aquifer

GEOHYROLOGIC UNITS

Recharge along edge of valley-fill deposits from infiltration 

of precipitation; and groundwater inflow and runoff from 

upland areas that recharge the confined aquifers where they 

crop out at land surface or are in contact with coarse-grained 

kame deposits along the edges of the valley.

1 1

1 1

Lower confined sand and gravel 

aquifer

2

2

Lodgment till

Kame sand and gravel

A
Geohydrology of the Stratified-Drift Aquifer System 35

they flow over the valley floor (fig. 20B). Two wells (TM2001 

and TM2063) on the crest of the Valley Heads Moraine on 

the west side of the valley (fig. 8) penetrated coarse-grained 

material (bouldery gravel that extends from land surface 

to bedrock), indicating that at least the upper confined 

aquifer (and possibly the middle aquifer) is connected to an 

unconfined part of the kame moraine and, therefore, receives 

recharge from direct precipitation and runoff from the valley 

walls over that zone (fig. 20B).

Groundwater Discharge

In the northern part of the study area, groundwater 

discharges to (1) the Village of Dryden municipal wells; 

(2) domestic, nonmunicipal community (mobile home 

parks and apartments), and several commercial wells; and 

(3) a Dryden Lake outlet and Virgil Creek. In addition, some 

groundwater exits as underflow through the three confined 

aquifers at the arbitrary aquifer boundary at the northern end 

of the study area near the northern boundary of the Village 

of Dryden.

In the southern part of the study area, groundwater 

discharges to (1) Dryden Lake, (2) the inlet to Dryden 

Lake, and (3) domestic, commercial, and agricultural wells. 

Throughout the study area, evapotranspiration during the 

growing season reduces the percentage of infiltrated water 

that reaches the water table. Evapotranspiration is estimated 

to range between 19 and 20 inches per year or roughly half of 

the annual precipitation in this area (Kontis and others, 2004, 

plate 1).

Municipal Withdrawals

The largest user of groundwater in the study area is the 

Village of Dryden. The village uses four production wells 

(TM1046, TM 981, TM 202, and TM 204; fig. 8) at three 

pumping stations (South Street, Jay Street, and Lake Road). 

Well TM1046 at the South Street pump station is pumped 

continuously, well TM 981 at the Jay Street pumping station 

is pumped daily but for only several hours per day, and wells 

TM 202 and TM 204 at the Lake Road pumping station 

are pumped irregularly—typically for a few hours a couple 

days a month or during high water-demand periods such as 

during hot summer intervals (Ron Moore, superintendent of 

public works, Village of Dryden, written commun., 2008). 

After water pumped from the municipal wells is used by 

homeowners, organizations, and businesses, most of the water 

is then routed to the sewage treatment plant (200 ft north of 

the northern boundary of the study area; fig. 8) where it is 

treated and discharged into Virgil Creek.

Before 1963, a spring-fed reservoir 1 mi northeast of 

the Village of Dryden (fig. 8) was used to supplement water 

pumped from well TM 207 at the South Street pumping 

station. Well TM 207 is 176 ft deep and screened in the 

lower confined aquifer. In 1964, the spring-fed reservoir was 

discontinued for use because the Tompkins County Health 

Department determined that the springs were susceptible to 

contamination. In 1964, municipal production wells TM 202 

and TM 204 (45 and 51 ft deep, respectively) were installed 

at the Lake Road pumping station to replace the reservoir and 

to meet increasing water demand in the village. Both wells 

were screened in the upper confined aquifer. In 1964, wells 

TM 202 and TM 204 were reported to yield 125 gal/min and 

115 gal/min, respectively. However, yields from the Lake 

Road wells have declined over time. In 1998, the combined 

sustained flow from the two wells was about 140 gal/min 

(Rice and Foster, 1998).

In 1977, municipal production well TM 199 (well depth 

212 ft) was installed at the Jay Street pumping station (fig. 8) 

and yielded 65 gal/min. However, the yield had declined 

from 65 gal/min in 1977 to 20 gal/min by 1986 when it was 

abandoned. The well was used as a production well from 1980 

to 1986 (fig. 21).

In 1986, well TM1046 (fig. 8) was constructed and 

replaced well TM 207 at the South Street pumping station 

and well TM 199 at the Jay Street pumping station, the yields 

from both of which were declining to the point where the 

wells were not producing enough water to meet demand from 

the village. Well TM1046 (180 ft deep) is screened in the 

lower confined aquifer and initially began pumping at a rate of 

about 120 gal/min in1986, but the pumping rate had steadily 

declined to about 77 gal/min by 2008 (fig. 21). The decreased 

pumping rate is believed to be due to encrustation of the 

screen openings, siltation of the aquifer in the vicinity of the 

screen, or both.

To offset the decline of production from well TM1046, 

pumping from well TM 981 (Jay Street pumping station) 

has increased from 1998 through 2008 (fig. 21). In 2008, 

wells TM1046 (South Street pumping station), TM 981 (Jay 

Street pumping station), and TM 204 (Lake Road pumping 

station) supplied 57 percent, 41 percent, and 2 percent of 

the village’s water consumption, respectively. It is estimated 

that the Village of Dryden municipal wells supply water to 

1,832 village residents (U.S. Census, 2000), 3,800 college 

students (residents in dormitories and transients), 1,900 high 

school students, and several small businesses.

The water use for 1963 was reported (Morrell Vrooman 

Engineers, 1964) to be 26.3 million gallons per year (Mgal/yr). 

Since 1970, the Village of Dryden has compiled pumping 

records. The total pumpage from all wells is summarized 

on figure 22. Water use has approximately tripled between 

the early 1970s, when withdrawals ranged between 18 and 

30 Mgal/yr, and from 2000 through 2008, when withdrawals 

ranged between 75 and 85 Mgal/yr (fig. 22). The rate of 

increase of groundwater withdrawal during the 39-year period 

from 1970 to 2008 was about 1.3 Mgal/yr. Water use increased 

substantially in the mid to late 1970s, when Tompkins 

Cortland Community College opened about 1 mi north of 

the village, and during subsequent periods of expansion 

at the college. From 2006 through 2008, the college used 

16 to 17 percent of the water withdrawn by the municipal 
Figure 21. Monthly withdrawals from Village of Dryden, New York, municipal production wells, September 1970 through December 2008, and water 

usage by Tompkins Cortland Community College, 2006 through 2008. Pumping data obtained from the Village of Dryden in 2008.

1234560

Year

1970 

1975 

1980

1985

1990

1995

2000

2005

Monthly pumpage, in millions of gallons 

Well TM 207 operation period 

(South Street pumping station)

Well TM 199 operation period 

(Jay Street pumping station)

Well TM1046 operation period (South Street pumping station)

Well TM 981 operation period 

(Jay Street pumping station)

No record of pumping

at South Street pumping 

station before 1977

EXPLANATION

Well TM1046 (South Street pumping station, finished in the lower confined aquifer)Well TM 207 (South Street pumping station, finished in the lower confined aquifer) Well TM 199 (Jay Street pumping station, finished in the lower confined aqu

Well TM 981 (Jay Street pumping station, finished in the middle confined aq

Wells TM 202 and TM 204 (Lake Road pumping station, finished in the upper confined aquifer)

Tompkins Cortland Community College usage
Geohydrology of the Stratified-Drift Aquifer System 37

Figure 22. Annual withdrawals from the Village of Dryden, New York, municipal production wells from 1970 

through 2008. Pumping data obtained from the Village of Dryden in 2008.

0

1970 1975 1980 1985 1990 1995 2000 2005

Annual water withdrawal, in millions of gallons per year

2008

Year

10

20

30

40

50

60

70

80

90

General trend

production wells. Water use has been greatest during the mid2000s, when it exceeded 80 Mgal/yr in 2004 and 2006. Water 

use decreased slightly in 2007 and 2008 as a result of repair of 

leaks in the water infrastructure and implementation of watersaving fixtures, especially at the college.

Other Withdrawals

Other groundwater withdrawals from the aquifer system 

that are outside the Village of Dryden supply system include 

domestic wells, community supply wells for a mobile home 

community and several apartment complexes, and wells that 

supply water to several small farms (table 1).

About 670 people outside the water distribution system of 

the Village of Dryden depend on water from the Virgil Creek 

and Dryden Lake stratified-drift aquifer system (table 1). 

The estimated total groundwater use for human consumption 

outside the water distribution system of the Village of Dryden 

is about 50,300 gallons per day (gal/d) or 18.4 Mgal/yr based 

on an estimated average water use of 75 gal/d per person for 

self-supplied water systems in New York (Hutson and others, 

2000) multiplied by the estimated 670 people that pump 

from the stratified-drift aquifers. Additional but unknown 

quantities of water are also withdrawn from wells in the 

stratified-drift aquifers from several small farms and small 

commercial facilities. The total withdrawal from the aquifer 

system in 2008 was about 89.0 Mgal/yr (70.6 Mgal/yr from 

the Village of Dryden production wells plus 18.4 Mgal/yr from 

withdrawals outside the village’s distribution system).

Groundwater Levels

Natural changes in aquifer storage, which are exhibited 

by fluctuations in groundwater levels, generally follow 

seasonal patterns. These changes include short periods of 

increased storage during late fall and late winter through 

early spring, when recharge to the aquifer exceeds discharge 

from the aquifer, and long periods of decreased storage from 

late spring through early fall, when discharge generally 

exceeds recharge.

For unconfined aquifers, gravity drainage and filling 

or emptying of void spaces is the dominant mechanism for 

storage change, and generally the storage coefficient (specific 

yield) ranges from about 0.02 where the aquifer includes 
38 Geohydrology, Water Quality, and Simulation of Groundwater Flow, Town of Dryden, Tompkins County, New York

Table 1. Estimated groundwater withdrawals from users outside the Village of Dryden municipal supply 

system and within the Virgil Creek and Dryden Lake valley-fill aquifer system study area, 2008.

Users

Number of 

homes 

or appartment 

units

Average 

persons 

per 

household1

Number 

of persons 

using water

Average use 

per person, 

in gallons 

per day2

Total use, 

in gallons 

per day

Private homes over the aquifer 218 2.32 506 75 37,932

Pleasant Valley Mobil Home Park 49 2.32 114 75 8,526

Keith Lane Appartments 8 2.32 19 75 1,392

Lake Road Apartments 8 2.32 19 75 1,392

Colongeli Apartments 6 2.32 14 75 1,044

Total 289 670 50,286

1

Source: http://www.publicrecordfinder.com/county-public-records/Tompkins-NY.html, accessed July 27, 2010.

2

Estimated from Hutson and others (2000).

fine-grained sediments to 0.35 where the aquifer includes very 

coarse-grained sediments (Freeze and Cherry, 1979). Storage 

changes for confined aquifers are dominated by water and 

sediment compression and expansion, and storage coefficient 

values are much lower than those for unconfined aquifers—

storage coefficients reported for confined stratified-drift 

aquifers in the glaciated Northeast range from 0.01 to 0.0001 

(Crain, 1974; Randall, 2001; Kontis and others, 2004).

Water-level data loggers were installed in four 

observation wells (TM1699 and TM1700 at the Lake Road 

pumping station, fig. 23; TM 207 at the South Street pumping 

station, fig. 24A; and test well TM 993 at Dryden Lake, fig. 

24B). The water levels were recorded in these wells for 1.5 to 

3 years.

At the Lake Road pumping station, the municipal 

production wells (TM 202 and TM 204; fig. 8) pump 

irregularly and for short periods of time (several hours a day 

approximately once a month), and drawdown is represented 

in the hydrograph as downward-pointing spikes on figure 

23. When pumping is conducted at the Lake Road pumping 

station, well TM 204 is typically used. Observation wells 

TM1699 and TM1700 are roughly midway between the 

municipal production wells TM 202 and TM 204 (120 ft from 

the pumping wells; fig. 8). Because the production wells are 

rarely used, the water-level record represents mostly static 

water levels (nonpumping conditions).

During nonpumping conditions at the Lake Road pump 

station, the water levels in wells TM1699 and TM1700 

fluctuated approximately 6 ft per year for the period of 

record (fig. 23). During pumping conditions, the water levels 

declined an additional 3 to 8 ft below the static water level in 

well TM1700 and an additional 2.5 to 6.5 ft below the static 

level in well TM1699. The water levels in observation wells 

TM1699 (depth 71 ft and finished in the middle confined 

aquifer) and TM1700 (depth 41 ft and finished in the upper 

confined aquifer) at the Lake Road pumping station paralleled 

each other, especially during nonpumping conditions when 

the water level in well TM1699 was typically 0.3 ft higher 

than in well TM1700, indicating that there may be hydraulic 

connection between these aquifers in this area with an upward 

hydraulic gradient. Well TM1699 penetrated a thin confining 

unit (an 11-ft-thick till and silt unit; fig. 9) that separates the 

upper confined aquifer from the middle confined aquifer. 

During pumping conditions, the water level in well TM1700 is 

typically 1 to 1.5 ft lower than that in well TM1699 (fig. 23), 

indicating that pumping has more effect on the upper confined 

aquifer than on the middle confined aquifer, which is expected 

because the municipal production wells and observation well 

TM1700 are finished in the upper confined aquifer. These 

minimal hydraulic head differences between the upper and 

middle aquifers may be due to (1) hydraulic connections 

established between the upper and middle confined aquifers 

as a result of poor or improper well construction in one or 

more of the six wells in the well field (for example, grout 

had not been used or was used improperly resulting in the 

two units having been connected through an outer skin of 

permeable drill cuttings adjacent to the casings), (2) the 

unit between the upper and middle aquifers being a leaky 

confining unit (consisting of semipermeable sediments such 

as fine to medium sand), or (3) the confining unit in this area 

having variable thickness and possibly being locally absent, 

which would result in windows where the two aquifer units 

are connected.

At the South Street pumping station, municipal 

production well TM1046 (finished in the lower confined 

aquifer; fig. 8) is pumped continuously except when 

mechanical problems caused the pump to turn off from 1 to 

4 hours periodically (as often as several times a month). When 

the pump is turned off, water levels rise sharply 20 to 25 ft in 

observation well TM 207 (15 ft west of well TM1046), and 

these rises are seen as sharp upward spikes on the hydrograph 

in figure 24A. Except for these short-term water-level spikes 

due to mechanical problems, the water level at TM 207 

represents water levels in the lower confined aquifer under 
Geohydrology of the Stratified-Drift Aquifer System 39

Figure 23. Hydrograph of the altitude of the groundwater levels from June 24, 2005, through May 14, 2008, in observation wells 

TM1699 and TM1700 at the Lake Road pumping station, Village of Dryden, New York. Locations of wells shown on figure 8.

Year

Altitude of groundwater level, in feet above NGVD 1929

1,112

1,114

1,110

1,108

1,102

1,104

1,106

1,100

J A S O N D J F M A M J J A S O N D J F M A M J J A S O N D J F M A M

2005 2006 2007 2008

Water level in well TM1699 typically 

0.3 ft higher than in well TM1700 

during nonpumping conditions

Water level in well TM1700 typically 

1.0 to 1.5 ft lower than in well 

TM1699 during pumping conditions { {

EXPLANATION

Altitude of water level in observation well TM1700 (well depth = 41 feet, 

finished in upper confined aquifer), in feet above NGVD 29 

Altitude of water level in observation well TM1699 (well depth = 71 feet, 

finished in middle confined aquifer), in feet above NGVD 29
40 Geohydrology, Water Quality, and Simulation of Groundwater Flow, Town of Dryden, Tompkins County, New York

Figure 24. Altitude of the water level from observation wells A, TM 207 and B, TM 993. Observation 

well TM 207 at the South Street pumping station, Village of Dryden, New York, has a well depth of 

176 feet, is finished in the lower confined aquifer, and was surveyed between May 19, 2006, and 

September 3, 2007. Observation well TM 993 at Dryden Lake, Town of Dryden, New York, has a well 

depth of 234 feet, is finished in the lower confined aquifer, and was surveyed between June 13, 

2007, and October 2, 2009. Locations of wells shown on figure 8.

Land surface

Land surface

Approximate static water level

2006 2007

JM J A S O N D J F M A M J J A 1,035

1,040

1,045

1,050

1,055

1,060

1,065

1,098

1,105

1,110

1,100

Altitude of groundwater level, in feet above NVGD 1929

No data

No

data

Altitude of groundwater level, in feet above NGVD 1929

2007 2008 2009

J J A S O N D J F M A M J J A S O N D J F M A M J J A S O 1,160

1,168

1,161

1,167

1,166

1,165

1,164

1,163

1,162

A

B

Year

Year

~~ ~~

Altitude of water level in observation well TM 993, in feet avove NGVD 29

Altitude of water level in observation well TM 207, in feet above NGVD 29

EXPLANATION
Geohydrology of the Stratified-Drift Aquifer System 41

pumping conditions. A static water level of 8.5 ft above land 

surface (artesian flowing condition) was measured during 

nonpumping conditions in production well TM1046 when the 

well was drilled in 1986. For the period of water-level record 

(May 19, 2006, through September 3, 2007), the water-level 

fluctuation during pumping in observation well TM 207 was 

3 ft. Assuming that the static water level has remained about 

constant since it was measured in 1986, the pumping of 

municipal production well TM1046 results in drawing down 

the water level in observation well TM 207 approximately 68 

to 71 ft (to altitudes ranging from 1,036 to 1,039 ft).

Observation well TM 993 (fig. 8) is 1.6 mi southeast from 

the Village of Dryden and is finished in the lower confined 

aquifer. For the period of water-level record from June 13, 

2007, through October 2, 2009, the water-level fluctuation 

in observation well TM 993 near Dryden Lake was 5.5 ft 

(fig. 24B), and the water-level data indicate that there were no 

pumping effects from the municipal pumping wells at Dryden. 

For the period of record, the hydraulic head in the well was 

always above the top of the aquifer (171 to 176 ft above the 

top of the aquifer; figs. 15 and 24B), and the water level was 

above land surface for 2 months in 2008, indicating that the 

aquifer was under artesian-flowing conditions during that 

period (fig. 24B). The recharge period (when groundwater 

storage in the aquifer is increasing) is shown by rising 

groundwater levels, which occur mostly during late fall and 

late winter through early spring when plants are dormant and 

evapotranspiration is minimal. Little or no recharge occurs 

during the growing season from late spring through early fall, 

when the rate of evapotranspiration typically exceeds the rate 

of precipitation.

Aquifer Properties

Well response to pumping (yield and drawdown) is a 

function of well construction (pump capacity, casing diameter, 

screen length and opening size, and well development) 

and aquifer properties, such as hydraulic conductivity 

(permeability), storage coefficient, and aquifer thickness. 

Transmissivity is hydraulic conductivity multiplied by aquifer 

thickness; and storativity is storage coefficient multiplied 

by aquifer thickness. Analysis of aquifer-test data allows 

the calculation of transmissivity and storativity, which are 

important to characterize the aquifer system and to develop 

groundwater-flow models.

Aquifer Test at Well TM 981 at the Jay Street 

Pumping Station

An aquifer test was conducted at Village of Dryden 

municipal production well TM 981 (well depth 72 ft) at 

the Jay Street pumping station (figs. 8 and 25) during June 

19–21, 2007. Production well TM 981 was drilled in 1998 

and is the village’s second largest source of groundwater 

(well TM1046 at the South Street pumping station is the 

largest source of groundwater). Well TM 981 is finished in the 

middle confined aquifer, has an 8-inch diameter casing, and 

is screened from 62 to 72 ft. Screen opening size is 40 slot 

(0.04 inch). The pumping rate was 104 gal/min for a 24-hour 

period (the maximum time the Village of Dryden could go 

without water in their delivery system from this well). Water 

that was pumped was routed to a holding tank. Water levels 

were recorded in municipal well TM 981 and in observation 

wells TM1700 and TM1699 at the Lake Road pumping 

station (1,150 ft northeast of the pumping well) and TM 

207 at the South Street pumping station (1,330 ft northwest 

of the pumped well, fig. 25). Wells TM1700 and TM1699 

are finished in the upper and middle confined aquifers, 

respectively. Well TM 207 is finished in the lower confined 

aquifer. Water-level recovery was measured for 24 hours when 

pumping ceased at municipal well TM 981.

The aquifer test was conducted to (1) determine whether 

there is hydraulic connection between the upper, middle, 

and lower confined aquifers and (2) determine the hydraulic 

properties of the middle confined aquifer at the Jay Street 

pumping station. The results of the aquifer test were used to 

input hydraulic conductivity values for the middle aquifer in 

the numerical groundwater-flow model.

During the 24-hour aquifer test, the pumping rate 

ranged from 105 gal/min during the early part of the test to 

103 gal/min during the latter part of the test and averaged 

104 gal/min. The drawdown (difference between static water 

level and pumping water level) in pumped well TM 981 at the 

end of 24 hours of pumping was 19.24 ft. Pumping from well 

TM 981 had no measurable effect on water levels in wells 

TM 207, TM1699, and TM1700; therefore, only the pumpedwell drawdown data were used for quantitative analysis of the 

aquifer hydraulic properties. It should be noted that although 

the village’s production well TM 204 (125 ft north of wells 

TM1700 and TM1699; fig. 25) was inadvertently pumped 

for several hours just before the test (it was turned off when 

discovered), the water levels in wells TM1700 and TM1699 

recovered to with 0.2 ft of static level by the time the aquifer 

test began. Also, there were no effects on water levels in 

observation wells TM1700 and TM1699 during the recovery 

phase of the aquifer test, indicating that pumping from well 

TM 981 had no measurable effect on water levels in wells 

TM1700 and TM1699. Because the pumping of production 

well TM 981 during the aquifer test had no effect on wells 

TM1700 and TM1699, the pumping of production well 

TM 204 until several hours just before the test probably did 

not affect the analysis of the drawdown data of TM 981.

Because of uncertainty on whether the deposits between 

the upper and middle confined aquifers is a nonleaky confining 

unit (comprising sediments of low hydraulic conductivity) 

or is a leaky confining unit (comprising sediments of low to 

moderate hydraulic conductivity), the hydraulic values were 

estimated using two methods of analysis (table 2). Results 

of the aquifer test analysis for a partially penetrating well in 

a confined aquifer using methods by Dougherty and Babu 

(1984) indicated that the transmissivity was 1,560 feet squared 
42 Geohydrology, Water Quality, and Simulation of Groundwater Flow, Town of Dryden, Tompkins County, New York

76°17'45" 76°17'30" 76°17'15"

42°29'

42°28'45"

42°28'30"

0 500 1,000 FEET

0 100 200 METERS

Well pumped for aquifer test Abandonded production well used as observation well for 

aquifer test

Lake Road production well—well finished in the upper 

confined aqifer. Well was not pumped during aquifer test.

U.S. Geological Survey test well 

used for observation well

EXPLANATION

Base from U.S. Geological Survey, 1969, 1:24:000

TM 207 (176 feet deep)

South Street pumping

station

TM 204 (51 feet deep)

Lake Road pumping

station

TM1700 (41 feet deep) 

Lake Road pumping 

station

TM1699 (72 feet deep)

Lake Road pumping

station

TM 981 (72 feet deep)

Jay Street pumping 

station

200 feet between stream

and well TM 981, however 

there is little or no hydraulic 

connection between the 

stream and pumping well 

because of confining units

[

Figure 25. Location of wells in which drawdown was measured for the aquifer test conducted in production 

well TM 981 in the Village of Dryden, New York, during June 19–21, 2007.
Geohydrology of the Stratified-Drift Aquifer System 43

Table 2. Estimated hydraulic values from analyses of aquifer-test data of partially penetrating muncipal well TM 981 

at the Jay Street pumping station, Village of Dryden.

[ft, feet; ft/d, feet per day; ft2/d, feet squared per day]

Method

Casing 

radius, 

in ft

Saturated 

thickness 

(aquifer 

thickness), 

in ft

Transmissivity, 

in ft2

/d

Horizontal 

hydraulic 

conductivity, 

in ft/d 

Storativity1

Well TM 981 (Jay Street)

Method by Dougherty and Babu 

(1984) for confined aquifer 

0.33 18 1,560 87 0.1

Method by Hantush and Jacob 

(1955) and Hantush (1964) for 

leaky confined aquifer

0.33 18 1,730 96 0.1

1

Dimensionless.

per day (ft2/d) and the horizontal hydraulic conductivity was 

87 feet per day (ft/d) based on a saturated thickness of 18 ft 

(table 2). Results of the aquifer test analysis for a partially 

penetrating well in a leaky confined aquifer using methods by 

Hantush and Jacob (1955) and Hantush (1964) indicated that 

the transmissivity was 1,730 ft2/d and the horizontal hydraulic 

conductivity was 96 ft/d based on a saturated thickness of 

18 ft (table 2).

Specific Capacity Test in Test Well TM 993 Near 

Dryden Lake

At the time when well TM 993 (located 450 ft north 

of Dryden Lake; fig. 8) was drilled, it was noted during 

development of the well (at a pumping rate of 45 gal/min) 

that the drawdown was only 0.8 ft, suggesting that a large 

amount of water could be derived from the aquifer at this site. 

To investigate the potential water yield at this site, a brief 

aquifer test (pumping period of 2 hours) was conducted in 

the test well on January 5, 2005. Well TM 993 is 234 ft deep, 

6 inches in diameter, open ended, and finished in coarse gravel 

that makes up the lower confined aquifer at this site. Specific 

capacities (a measure of well yield per unit of drawdown that 

can be used to provide an estimate of the maximum yield for a 

well and well efficiency) were computed for several pumping 

rates from the brief aquifer test. At pumping rates of 100, 200, 

300, and 400 gal/min, the specific capacities were 28, 27, 24, 

and 20 gallons per minute per foot of drawdown, respectively 

(fig. 26). Drawdown was measured in the pumping well (TM 

993) during the 2-hour-long pumping interval, and water-level 

recovery was measured for 4.5 hours afterwards. Drawdown 

at the end of 2 hours of pumping was 20 ft. There were no 

wells nearby that were finished in the lower confined aquifer; 

therefore, drawdown data were only obtainable from the 

pumping well. The results of the specific-capacity test indicate 

that, at this site, the confined aquifer could yield large amounts 

of water (more than 1,000 gal/min) to a properly screened, 

large-diameter pumping well. Specific capacity decreases with 

increasing drawdown because of frictional losses associated 

with the well itself. It is likely that a substantial part of the 

decreasing specific capacity computed for this test at pumping 

rates from 300 to 400 gal/min is due to increasing frictional 

loses as the physical capacity for flow through a 6-inchdiameter casing is approached.

To estimate the potential yield from this site, the 

transmissivity was first estimated from the specific capacity 

data using the modified Theis equation (Bradbury and 

Rothschild, 1985):

( ) 2

2.25 ln 2

4 w w

Q Tt T sp

π s s rS

      =     + −       , 

 (1)

where

T = transmissivity;

Q = well discharge, the volume of water 

discharged over a given time;

s = drawdown in the well;

sw = well loss;

t = pumping time;

rw = well radius;

S = storage coefficient (dimensionless); and

sp = partial penetration.

The solution of equation 1 yields an estimate of T that is corrected for well loss and partial penetration. The T computed 

for the specific capacity test was 142,000 ft2/d 

where 

Q = 400 gal/min, 

s = 20 ft, 

sw = 1,

 t = 2 hours, 

rw = 0.25 ft, and 

S = 0.0002. 
44 Geohydrology, Water Quality, and Simulation of Groundwater Flow, Town of Dryden, Tompkins County, New York

0 50 100 150 200 250 300 350 400 450

Specific capacity, in gallons per minute per foot of drawdown

Pumping rate, in gallons per minute

0

50

40

30

20

10

0

25

20

15

10

5

Drawdown, in feet

Specific capacity

Drawdown

EXPLANATION

Figure 26. Results of specific capacity test in test well TM 993, 450 feet north of Dryden Lake, Town 

of Dryden, New York. Well log and well construction details are shown on figure 15; location of well is 

shown on figure 8.

Using equation 1 to solve for drawdown of a hypothetical 

large pumping well 

where 

T = 142,000 ft2/d, 

Q = 2,000 gal/min, 

t = 2 hours, 

rw = 0.42 ft (10 in.), 

S = 0.0002, and

s = 100 ft.

A drawdown of 100 ft is less than 50 percent of the 

available head (total available head is about 235 ft). Although 

well yield can be defined as the maximum pumping rate 

without lowering the water level in the well below the pump 

intake (Freeze and Cherry, 1979), there is no set definition 

of safe yield. However, the British Columbia Ministry of 

the Environment (2011) suggests that about 70 percent of 

available drawdown is considered safe available drawdown, 

which generally leaves sufficient room in the well for a 

submersible pump and for when groundwater levels are 

lower than average during drought periods. Computation 

of the potential yield using a linear equation may provide 

unreliable results because this computed yield does not 

actually represent the behavior of the well during pumping. 

Using equation 1 for extrapolating the pumping rate beyond 

what is actually observed has risks of overestimating the yield 

and overdesigning the well. The best method to design a well 

would include conducting both constant and step tests using 

a large-diameter screened well (10 to 24 inches in diameter). 

Ideally, the step test would need to be conducted at a discharge 

rate up to the maximum possible. A long aquifer test (more 

than 72 hours) would be needed to accurately determine a 

sustainable yield.

In addition to the specific-capacity test conducted for this 

study, several well-performance tests (drawdown tests) had 

been conducted by hydrologic engineers and drillers in several 

wells in the Village of Dryden since 1946. Because there were 

insufficient data on well construction, data from these tests 

have not been used to compute hydraulic properties of the 

aquifers, such as transmissivity, hydraulic conductivity, and 

storativity. Nevertheless, the sources of these data are listed in 

table 3.

Water Quality

Water-quality samples were collected to characterize 

the chemical quality of surface water and groundwater in 

the study area. On various dates from 2003 through 2005, 

surface-water samples were collected from eight sites, 

including Virgil Creek, the Dryden Lake outlet, and several 

tributaries (fig. 27). On various dates from 2003 through 2009, 

groundwater samples were collected from eight wells (fig. 27). 

Field measurements were made for pH, specific conductance, 
Table 3. Historic well tests from water-supply investigations for the Village of Dryden.[Surveys conducted by various engineering consultants from 1946 through 2000. BLS, below land sufrace; ft, feet; ft3/s, cubic feet per second; gal/d, gallons per day; gal/min, 

gallons per minute; PWS, production well; USGS, U.S. Geological Survey; —, no data; #, number]

Well identifier

USGS 

well site 

name

Year of 

well test

Well 

type

Hole 

depth, 

in ft BLS

Aquifer 

thickness, 

in ft

Screened 

interval, 

in ft BLS

Static 

water level, 

in ft BLS1

Aquifer 

model 

layer

Pumping rate during test

gal/d gal/min ft3/s

South Street, site 12 — 1946 Test 192 7 177–184 +12 3 50,400 35 0.08

South Street supply well2 TM 207 1949 PWS 181 23 169–176 +25 3 — — —

PWS well # 1 (Lake Road)3 TM 202 1964 PWS 45 15 30–45 — 1 — — —Test well (Jay Street)4 TM 199 1977 Test 217 — 193–212 — 3 36,000 25 0.06Kimberly drive test welld TM1015 1978 Test 97 — Open end Flows6 2 317,000 220 0.49

Test well (South Street)3 — 1986 Test — — 173–185 — 3 — — —

Test well (Jay Street)5 — — Test 225 — — — 3 — — —Test well (South Street)4 — 1998 — — — 68–74 — 3 129,000 90 0.20

Lake Street well #24 TM 202 — PWS 51 — — — 1 200,000 140 0.31

Jay Street (initial)4 — — Test — — 170–200 — 3 93,600 65 0.12

Jay Street (final)4 — — — — — — — — 28,800 20 0.04Jay Street suppy well4 TM 981 — PWS 75 — 62–72 — 2 147,000 102 0.23

1Positive values are above land surface.2Survey conducted by Lozier engineers.3Survey conducted by Vrooman engineers.4Survey conducted by Foster, Brayton.5Survey conducted by Parrott-Wolf .6Flowing artesian well.
46 Geohydrology, Water Quality, and Simulation of Groundwater Flow, Town of Dryden, Tompkins County, New York

Figure 27. Location of groundwater and surface-water sampling sites in Virgil Creek and Dryden Lake Valleys, Town of 

Dryden, New York.

0 1 2 MILES

0 1 2 KILOMETERS

76°19' 76°18' 76°17' 76°16' 76°15' 76°14' 76°13' 42°31'

42°30'

42°29'

42°28'

42°27'

42°26'

42°25'

Base from TOPO! 2003 ©National Geographic, scale 1:24,000

TM 993

TM1386

TM1940

TM1046

TM2724

TM 981

TM 170

TM 202

04233680

04233669

1423368620

0423368490

0423368020

0423368010

422827

076162401

TM 993

0423368020

EXPLANATION

Model grid boundary

Stream

Boundary of stratified-drift 

aquifer study area

Base-flow sampling site and site identification number in which 

water-quality sample was collectedAnalyses are in table 4

Well and well site name in which groundwater sample was collected

Analyses are in tables 6 and 7

04233679
Water Quality 47

and water temperature for surface-water samples and 

groundwater samples. The concentrations of 23 constituents, 

including inorganic major ions, nutrients, and radiochemicals 

were measured in surface water; 42 constituents, including 

nutrients, inorganic major ions, and trace elements were 

measured in groundwater samples. All samples were analyzed 

by the USGS National Water Quality Laboratory (NWQL) in 

Denver, Colorado. Analytical results for selected constituents 

are compared with Federal drinking-water standards. The 

standards include maximum contaminant levels (MCLs), 

secondary maximum contaminant levels (SMCLs), and health 

advisories (HAs) established by the U.S. Environmental 

Protection Agency (USEPA; 2006).

Surface Water

A total of 14 surface-water samples were collected 

by USGS personnel during the study period—7 at roughly 

seasonal intervals during base-flow conditions at the Virgil 

Creek streamgage in Dryden (station 0423368620; fig. 27) 

during 2003–4. Additionally, two samples were collected 

in 2004 from two tributaries to Virgil Creek in the study 

area, and four samples were collected in conjunction with 

Dryden Lake (one each from the inlet and outlet and one each 

from two tributaries to the lake). Winter samples collected 

during base flow and non-snowmelt conditions can be an 

approximation of the chemical quality of groundwater because 

microbial activity, which can alter the concentrations of some 

constituents through contact with air and stream biota, is at a 

minimum. For example, microbial activity (associated with 

algal growth in the streams during warm seasons) can change 

dissolved oxygen concentrations or use the nitrogen in the 

water, potentially causing a decrease in nitrate concentrations. 

Results of chemical analyses are presented in table 4, and 

summary statistics for pH and several selected chemical 

constituents are provided in table 5.

Physicochemical Properties

The pH of surface-water samples ranged from 8.1 to 

7.4, with a median value of 7.6 (tables 4 and 5); pH values 

for all 14 samples were within the accepted USEPA SMCL 

range of 6.5 to 8.5 (U.S. Environmental Protection Agency, 

2006). Specific conductance of the samples ranged from 131 

to 402 microsiemens per centimeter (μS/cm) at 25 degrees 

Celsius (°C), with a median value of 306 μS/cm.

Common Inorganic Constituents

The cation detected in the greatest concentration was 

calcium, which ranged from 7.46 to 55.1 milligrams per liter 

(mg/L), with a median value of 40.8 mg/L (tables 4 and 5). 

Magnesium concentrations ranged from 1.59 to 11.1 mg/L, 

with a median of 7.99 mg/L. Calcium and magnesium 

contribute to water hardness, which ranged from 25.2 to 

184 mg/L as calcium carbonate (CaCO3

), with a median 

of 134 mg/L. Sodium concentrations ranged from 3.41 to 

29.3 mg/L, with a median value of 12.0 mg/L. Potassium 

concentrations ranged from 0.45 to 1.50 mg/L, with a median 

value of 1.18 mg/L.

The anion detected in the greatest concentration was 

bicarbonate, the concentration of which ranged from 17 to 

151 mg/L, with a median value of 120 mg/L (tables 4 and 5). 

Chloride concentrations ranged from 4.54 to 50.3 mg/L, with 

a median value of 21.2 mg/L. Sulfate concentrations ranged 

from 7.12 to 17.8 mg/L, with a median value of 12.6 mg/L. 

Silica concentrations ranged from 1.75 to 6.59 mg/L, with 

a median value of 4.54 mg/L. Fluoride concentrations were 

detected in either trace amounts or were below the detection 

limit (0.17 mg/L). None of the inorganic major constituents 

collected from surface-water sites in the study area exceeded 

any Federal or State water-quality standards.

Nutrients

Nitrate was the predominant nitrogen species present 

in all nutrient samples of surface water, ranging from 0.12 

to 5.17 mg/L as nitrogen (table 4). High concentrations 

of nitrogen can cause excessive plant and algal growth in 

streams, depleting oxygen and stressing organisms in their 

aquatic habitat, and it also is a human health concern when 

the concentration is more than 10 mg/L (U.S. Environmental 

Protection Agency, 2006). The concentration of nitrate was 

greater than 2 mg/L in two samples—the tributary to Dryden 

Lake at West Lake Road (USGS station 0423368020) and in 

the tributary to Dryden Lake at East Lake Road near Harford 

(USGS station 04233679)—and may reflect fertilizer use on 

nearby agricultural areas. Orthophosphate concentrations 

were not detected above the reporting limit (0.02 mg/L as 

phosphorus) in any surface-water samples. None of the 

surface-water samples exceeded Federal or State drinkingwater standards for nitrate or nitrite.

Groundwater

Groundwater samples were collected from eight wells—

two finished in the upper confined aquifer, two in the middle 

confined aquifer, and four in the lower confined aquifer 

(locations shown in fig. 27), including three Village of Dryden 

municipal wells (TM 202, TM 981, and TM1046), two test 

wells (TM 993 and TM2724), two domestic wells (TM1386 

and TM1940), and one nonmunicipal community well (mobile 

home park well TM 170). Field measurements were made of 

pH, specific conductance, and water temperature. Samples 

were analyzed for inorganic major ions, nutrients, and trace 

metals by the USGS NWQL in Denver, Colorado. Results 

of chemical analyses are tabulated in tables 6 and 7, and 

summary statistics of selected chemical constituents are in 

tables 5 and 8.
48 Geohydrology, Water Quality, and Simulation of Groundwater Flow, Town of Dryden, Tompkins County, New York

Table 4. Physical properties and concentrations of inorganic major ions, trace metals, and nutrients in surface-water samples from Virgil 

Creek, inlet and outlet to Dryden Lake, and several tributaries, Town of Dryden, New York, 2003–05

[Sampling site locations are shown in figure 27. conf, confined; e, estimated; ft, feet; ft3/s, cubic feet per second; mg/L, milligrams per liter; μg/L, micrograms 

per liter; μS/cm, microsiemens per centimeter at 25 degrees Celsius; Parm code, USGS National Water Information System (NWIS) parameter code; S&G, sand 

and gravel; SH, State Highway; trib., tributary; USGS, U.S. Geological Survey; XX, not available; <, less than; —, not analyzed; CaCO3, calcium carbonate; °C, 

degrees Celsius]

USGS site name: Virgil Creek at SH 13 at Dryden

 Date sampled: 2/11/2003 5/20/2003 8/18/2003 1/13/2004 5/27/2004 6/28/2004 9/14/2004

USGS station identification number: 0423368620

Physicochemical properties Parm 

code Units Values of physical properties

pH (lab) 00403 pH 7.9 7.5 7.5 7.6 7.8 8.1 8.0

Specific conductance (lab) 90095 μS/cm 394 330 339 292 238 365 300

Dissolved oxygen (field) 00300 mg/L 13.2 12.9 10.8 — — — —

Common inorganic constiuents

Hardness, filtered, as CaCO3 00900 mg/L 135 139 150 128 105 164 133

Calcium, filtered 00915 mg/L 40.7 41.4 44.7 38.6 31.9 48.9 40.8

Magnesium, filtered 00925 mg/L 8.15 8.71 9.27 7.78 6.26 10.1 7.49

Potassium, filtered 00935 mg/L 1.43 1.31 1.50 1.14 1.26 1.06 1.28

Sodium, filtered 00930 mg/L 29.3 17.8 13.6 11.4 10.0 15.4 12.3

Alkalinity, filtered as CaCO3 39086 mg/L 92 94 98 94 75 125 107

Bicarbonate, filtered, as CaCO3 00453 mg/L 112 115 128 115 90 151 130

Chlorides, filtered 00940 mg/L 50.3 30.1 24.1 20.5 14.0 26.1 19.4

Fluoride, filtered 00950 mg/L 0.03 <0.17 <0.17 <0.17 <0.17 <0.17 <0.17 

Silica, filtered 00955 mg/L 4.73 1.75 3.78 4.65 4.08 3.06 5.40

Sulfate, filtered 00945 mg/L 17.8 14.2 12.5 12.6 9.14 14.2 9.80

Dissolved solids, dried at 

180°C

70300 mg/L 226 188 198 172 143 208 182

Trace metals

Iron, filtered 01046 μg/L 30.7 60.1 52.9 23.5 108 37.8 29.3

Manganese, filtered 01056 μg/L 34.2 12.0 9.39 11.9 21.4 11.3 8.17

Nutrients

Ammonia, as N, filtered 00608 mg/L 0.04 <0.04 <0.04 <0.04 <0.04 <0.04 <0.04 

Nitrate+nitrite, as N, filtered 00631 mg/L 1.37 0.77 0.74 1.48 0.59 1.01 0.78

Nitrite, as N, filtered 00613 mg/L e0.004 0.008 <0.008 e0.004 0.014 <0.008 <0.008

Ammonia+organic-N, filtered 00623 mg/L 0.15 0.22 0.25 0.12 0.26 0.18 0.20

Ammonia+organic-N, 

unfiltered

00625 mg/L 0.22 0.30 0.29 0.26 0.36 0.22 0.40

Orthophosphate, as P, filtered 00671 mg/L <0.02 <0.02 <0.02 <0.02 e0.01 <0.02 <0.02 

Phosphorus, filtered 00666 mg/L 0.007 0.009 0.008 0.006 0.020 0.007 0.005

Phosphorus, unfiltered 00665 mg/L 0.014 0.021 0.008 0.019 0.042 0.017 0.027

Stream discharge 

Discharge, instantaneous 00061 ft3/s 35 26 19 50 150 16 43

a

U.S. Environmental Protection Agency (USEPA) drinking water advisory taste threshold.

b

New York State Department of Health maximum contaminant level.

c

USEPA secondary maximum contaminant level.
Water Quality 49

Table 4. Physical properties and concentrations of inorganic major ions, trace metals, and nutrients in 

surface-water samples from Virgil Creek, inlet and outlet to Dryden Lake, and several tributaries, Town of 

Dryden, New York, 2003–05.—Continued

Virgil Creek 

2,200 ft 

upstream of 

SH 38 near 

Dryden

Virgil 

Creek at 

Southworth 

Road bridge

Dryden 

Lake outlet 

upstream 

of SH 38 at 

Dryden

Dryden 

Lake inlet 

near Dryden

Dryden 

Lake trib. at 

West Lake 

Road near 

Dryden

Dryden 

Lake trib. 

at East 

Lake 

Road near 

Dryden

Dryden 

Lake trib. at 

East Lake 

Road near 

Harford Drinking 

water 

1/13/2004 8/17/2005 1/13/2004 1/13/2004 1/13/2004 1/13/2004 1/13/2004 standard

04233669 422827 

076162401 0423368490 04233680 0423368020 0423368010 04233679

Values of physical properties

7.9 8.1 7.4 7.6 7.4 7.4 7.4 6.5–8.5c

313 402 241 216 176 131 361 XX

— — — — — — — XX

Common inorganic constiuents

139 184 104 94.2 25.2 58.7 163 XX

42.1 55.1 30.6 27.2 7.46 16.9 47.6 XX

8.23 11.1 6.76 6.23 1.59 4.00 10.8 XX

1.21 1.47 0.91 0.79 0.45 1.03 0.91 XX

11.8 15.5 8.64 7.22 22.3 3.41 11.4 60a

102 118 104 60 14 50 110 250c

124 144 127 73 17 61 134 XX

21.2 27.3 15.4 12.1 35.0 4.54 21.2 XX

<0.17 e0.05 <0.17 <0.17 <0.17 <0.17 <0.17 2.2b

4.95 4.44 4.08 5.63 4.51 4.56 6.59 XX

12.3 13.1 12.7 10.8 7.12 8.01 12.7 250c

182 229 140 134 92 84 213 XX

Trace metals

8.9 e4 44.5 47.2 23.5 68.9 15.7 300b,c

8.45 2.7 27.7 36.6 5.84 25.2 8.06 50c–300b

Nutrients

<0.04 <0.04 <0.04 <0.04 <0.04 <0.04 <0.04 XX

1.77 1.19 1.16 2.17 0.22 0.12 5.17 10a,b

e0.004 <0.008 0.008 <0.008 <0.008 <0.008 e0.005 1a,b

0.12 0.17 0.23 0.10 0.15 0.20 0.20 XX

0.13 0.11 0.20 1.0 0.27 0.32 0.50 XX

<0.02 <0.02 <0.02 <0.02 e0.01 <0.02 <0.02 XX

0.007 0.004 0.006 0.006 0.024 0.016 0.009 XX

0.013 0.005 0.018 0.086 0.05 0.101 0.04 XX

Stream discharge

26.3 — 14.3 5.64 0.25 0.33 2.5 XX
50 Geohydrology, Water Quality, and Simulation of Groundwater Flow, Town of Dryden, Tompkins County, New York

Table 5. Summary statistics for pH and concentrations of major chemical constituents in surface-water and groundwater samples 

collected in the Virgil Creek and Dryden Lake valleys, Town of Dryden, New York, 2003–09.

[All samples filtered. mg/L, milligrams per liter; °C, degrees Celsius; —, no drinking-water standard; CaCO3, calcium carbonate; μS/cm, microsiemens per 

centimeter at 25 degrees Celsius]

Constituent

Drinkingwater 

standard

Number 

of 

surfacewater 

samples

Number 

of 

samples 

exeeding 

limit

Surface-water samples Groundwater samples

Minimum Median Maximum Minimum Median Maximum

pH (field) 6.5–8.5a 14 0 7.4 7.6 8.1 7.0 7.8 8.2

Specific conductance, μS/cm None 14 — 131 306 402 328 419 487

Hardness, mg/L as CaCO3 None 14 — 25.2 134 184 145 200 257

Alkalinity, mg/L as CaCO3 250a 14 0 14 96 125 113 125 161

Common ions

Cations:

Calcium, mg/L None 14 — 7.46 40.8 55.1 39.6 57.8 75.2

Magnesium, mg/L None 14 — 1.59 7.96 11.1 11.2 13.9 17.2

Potassium, mg/L None 14 — 0.45 1.18 1.50 0.55 0.80 2.11

Sodium, mg/L 60a 14 0 3.41 12.0 29.3 4.80 8.70 12.2

Anions:

Bicarbonate, mg/L as CaCO3 None 14 — 17 120 151 138 152 196

Chlorides, mg/L 250a,b 14 0 4.54 21.2 50.3 5.71 17.0 31.7

Silica, mg/L None 14 — 1.75 4.54 6.59 5.44 10.6 13.7

Sulfate, mg/L 250a 14 0 7.12 12.6 17.8 15.8 29.4 49.0

a

U.S. Environmental Protection Agency (USEPA) secondary maximum contaminant level.

b

USEPA drinking water advisory taste threshold.

Physicochemical Properties

The wells that were sampled ranged from 53 to 234 ft 

deep (table 6). The pH of the samples ranged from 7.0 to 

8.2, with a median value of 7.8 (tables 5 and 6); no pH 

measurement was outside the USEPA SMCL range of 6.5 to 

8.5. Specific conductance values of the samples ranged from 

328 to 487 μS/cm, with a median value of 419 μS/cm.

Inorganic Major Ions

No samples exceeded any Federal or State drinking-water 

health advisory standards. The cation that was detected in 

the greatest concentration was calcium, ranging from 39.6 to 

75.2 mg/L, with a median value of 57.8 mg/L (tables 5 and 6). 

Magnesium concentrations ranged from 11.2 to 17.2 mg/L, 

with a median value of 13.9 mg/L. Calcium and magnesium 

contribute to water hardness as CaCO3

, which ranged from 

145 to 257 mg/L, with a median value of 200 mg/L. Five of 

the eight sampled wells yielded water with a hardness greater 

than 180 mg/L, which is classified as very hard, and the 

hardness of the remaining three samples ranged from 145 to 

170 mg/L, which is classified as hard (Hem, 1985).

Sodium concentrations ranged from 4.8 to 12.2 mg/L, 

with a median value of 8.70 mg/L (tables 5 and 6), for the 

eight wells sampled. The median concentration of sodium in 

the four public-supply wells sampled was 8.7 mg/L, which is 

lower than the median concentration of sodium of 19 mg/L 

detected in public-supply wells that tap the glacial aquifer 

systems in the northern United States (Mullaney and others, 

2009). The median concentration of sodium in the four 

domestic and test wells sampled was 8.64 mg/L, which is 

slightly higher than the median concentration of sodium of 

12 mg/L detected in domestic wells that tap the glacial aquifer 

systems in the northern United States.

The anion detected in the greatest concentration was 

bicarbonate, the concentration of which ranged from 129 

to 181 mg/L, with a median value of 152 mg/L (tables 5 

and 6). Bicarbonate values were calculated from alkalinity 

concentrations, which are given in milligrams per liter of 

CaCO3

. Sulfate concentrations ranged from 15.8 to 49 mg/L, 

with a median value of 29.4 mg/L. Alkalinity, which results 

from dissolution of carbonate minerals such as those 

composing limestone and dolomite and is a measure of the 

capacity of water to neutralize acid, had concentrations that 

ranged from 113 to 161 mg/L, with a median of 125 mg/L. 

Alkalinity lower than 100 mg/L can be corrosive under low 
Water Quality 51

pH conditions, and alkalinity greater than 150 mg/L can 

cause scale (lime) buildup in plumbing pipes (Mechenich 

and Andrews, 2004). Chloride concentrations ranged from 

5.71 to 31.7 mg/L, with median value of 17.0 mg/L (tables 

5 and 6). The median concentration of chloride in the four 

public-supply wells sampled was 14.9 mg/L, which is lower 

than the median concentration of 26 mg/L that was detected 

in public-supply wells that tap the glacial aquifer systems 

in the northern United States (Mullaney and others, 2009). 

The median concentration of chloride in the four domestic 

and test wells sampled was 18.3 mg/L, which is slightly 

higher than the median concentration of 12 mg/L that was 

detected in domestic wells that tap the glacial aquifer systems 

in the northern United States (Mullaney and others, 2009). 

Neither chloride nor sulfate exceeded any Federal or State 

drinking-water standards in samples from any of the confined 

aquifer systems.

The major-ion compositions of water from sampled wells 

from this study and from three other valley-fill aquifer systems 

in Tompkins County (Lower Sixmile Creek and Willseyville 

Creek trough, Upper Sixmile Creek and West Branch Owego 

Creek Valleys, and Upper Buttermilk and Danby Creek 

Valleys) are presented for comparison using a piper (trilinear) 

diagram (fig. 28), which shows the relative contributions of 

major cations and anions, on a charge-equivalent basis, to 

the total ion content of the water. Percentage scales along the 

sides of the diagram indicate the relative concentration, in 

milliequivalents per liter, of each major ion. Cations are shown 

in the left triangle, and anions are shown in the right triangle. 

The central diamond integrates the data.

Calcium with some sodium and magnesium generally 

dominate the cation composition; bicarbonate and, in a few 

samples, chloride dominate the anion composition in samples 

from this study area and in most samples from the other three 

stratified-drift aquifers in Tompkins County where data are 

available (fig. 28). The exceptions are two samples that were 

collected in Upper Buttermilk Creek and Danby Creek Valleys 

and two samples that were collected in Upper Sixmile Creek 

and West Branch Owego Creek Valleys, which were sodium 

bicarbonate- to sodium-chloride type waters. The chemistry 

of water from two wells in Upper Sixmile Creek Valley that 

were of a sodium bicarbonate- to sodium chloride-type water 

was a result of enrichment from brackish water in bedrock that 

locally discharges to the valley fill (Miller, 2009). The water 

chemistry in the stratified-drift aquifers in all four study areas 

is similar because the geologic settings of all the areas are 

similar and comprise Valley Heads glacial drift and Devonian 

shales and siltstones.

Nutrients

Groundwater samples from each of the three confined 

aquifers were analyzed for several nitrogen and phosphorus 

species (table 6). Nitrate was present above the reporting 

limit of 0.06 mg/L in only one well (TM1940), which had a 

concentration of 1.78 mg/L. Nitrate concentrations were well 

below the USEPA MCL of 10 mg/L (U.S. Environmental 

Protection Agency, 2006). Nitrate concentrations are relatively 

low in the study area because the major aquifers are confined 

and not subject to direct recharge from the land surface 

where there are sources of nitrate from septic systems and 

fertilizers (agricultural land or golf courses). The impermeable 

upper confining unit impedes chemicals that are applied 

on the land surface from readily infiltrating into the upper 

confined aquifer.

Nitrite was detected in only one well at a concentration 

above the reporting limit of 0.008 mg/L (0.023 mg/L in 

well TM1386). All results of nitrite analyses were below 

the USEPA MCL of 1 mg/L (U.S. Environmental Protection 

Agency, 2006). Ammonia concentrations ranged from an 

estimated 0.02 to 0.12 mg/L as nitrogen. Orthophosphate was 

not detected above the reporting limit (0.02 mg/L) in any 

groundwater samples (table 6).

Trace Elements

Trace elements detected in every sample included 

aluminum, arsenic, barium, boron, iron, lithium, manganese, 

nickel, molybdenum, strontium, uranium, and zinc (table 7). 

The trace elements detected in the greatest concentrations 

were barium, boron, iron, lithium, manganese, and strontium. 

No samples exceeded Federal or State MCLs, but manganese 

was present in concentrations that exceeded the USEPA SMCL 

of 50 micrograms per liter (μg/L) in seven of eight wells 

sampled (table 7). All aluminum concentrations were less 

than 1.9 μg/L. Arsenic concentrations ranged from less than 

0.2 to 9.2 μg/L, with a median of 1.2 μg/L (tables 7 and 8). 

An arsenic concentration of 9.2 μg/L was detected in Village 

of Dryden production well TM 981 at Jay Street, which is 

slightly less than the USEPA MCL for arsenic of 10 μg/L. 

Barium concentrations ranged from 30.3 to 216 μg/L, with 

a median of 146 μg/L. Boron concentrations ranged from 

10 to 24 μg/L, with a median of 15 μg/L; an MCL has not 

been established for boron. Iron concentrations ranged from 

less than 0.6 to 227 μg/L, with a median of 73.8 μg/L. Lead 

was detected in five of eight samples, but none exceeded the 

USEPA MCL (15 μg/L). Lithium concentrations ranged from 

1.85 to 8.92 μg/L, with a median of 6.96 μg/L; an MCL has 

not been established for lithium. Strontium concentrations 

ranged from 75.9 to 415 μg/L, with a median of 176 μg/L; 

an MCL has not been established for strontium. Uranium 

concentrations ranged from 0.357 to 0.797 μg/L, with a 

median of 0.548 μg/L; no samples exceeded the USEPA MCL 

of 30 μg/L.

Groundwater-Age Dating

Concentrations of chlorofluorocarbons (CFCs) and 

tritium (3

H) can be used to estimate the age of groundwater 

(table 9). CFCs are stable and long-lasting synthetic industrial 

compounds that have been released into the atmosphere since 
Table 6. Physical properties and concentrations of inorganic major ions, nutrients, and tritium in groundwater samples from confined aquifers in the Lake Valleys, Town of Dryden, New York, 2003–09. [Sampling site location is shown in figure 27. conf, confined; e, estimated; ft, feet; mg/L, milligrams per liter; μS/cm, microsiemens per centimeter at 25 degrees Celsius (°C); PInformation System (NWIS) parameter code; USGS, U.S. Geological Survey; PWS, public supply well; S&G, sand and gravel; TU, tritium unit; XX, not available; <, less than; CaCO3, calcium carbonate] Aquifer sampled Upper aquifer Middle aquifer Lower aquifer 

Local name : Lake Street PWS well Domestic well Jay Street PWS well Domestic well South Street PWS well Dryden Lake test well Keith Lane test well 

USGS site name: TM 202 TM1386 TM 981 TM1940 TM1046 TM 993 TM2724 

Date sampled : 7/28/2003 8/31/2005 7/28/2003 8/29/2005 7/28/2003 12/13/2004 12/16/2009 

USGS station identification number: 422857 076172701 422821 076163701 422854 076174201 422821 076161901 422905 076144901 422755 076164801 422812 076172201 

Physiochemical properties Parm code Units Values of physical properties Aquifer type S&G, conf S&G, conf S&G, conf S&G, conf S&G, conf S&G, conf S&G, conf 

Well depth, below land surface 72008 ft 53 68 72 88 180 234 229 

Dissolved oxygen (field) 00300 mg/L 3.4 1.7 4.3 1.2 2.8 — 0.7 

Dissolved oxygen (lab) 62971 mg/L 0.1 — 0.3 — 0.4 0.1 — 

pH (field) 00400 pH 8.1 7.2 8.2 7.8 8.1 7.9 7.0 

Specific conductance (field) 00095 μS/cm 475 416 487 427 328 337 339 

Water temperature 00010 Celsius 10.0 12.4 10.1 11.0 10.7 10.1 7.6 

Common inorganic ions: Concentrations of chemical constituents Hardness, filtered, as CaCO3 00900 mg/L 257 211 246 189 169 145 155 

Calcium, filtered 00915 mg/L 75.2 59.0 70.0 56.7 48.0 39.6 41.6 

Magnesium, filtered 00925 mg/L 16.9 15.3 17.2 11.5 11.9 11.2 12.4 

Potassium, filtered 00935 mg/L 0.73 2.11 0.60 1.07 0.71 0.86 0.55 

Sodium, filtered 00930 mg/L 8.61 6.48 12.2 11.8 8.78 10.8 4.80 

Alkalinity, filtered, as CaCO3 29801 mg/L — 161 — 138 — 115 113 

Bicarbonate, filtered, as CaCO3 29805 mg/L — 196 — 168 — 140 138 

Chlorides, filtered 00940 mg/L 16.7 16.4 31.7 17.3 5.71 19.3 21.6 

Fluoride, filtered 00950 mg/L <0.17 <0.10 <0.17 e0.08 0.24 0.11 0.12 

Silica, filtered 00955 mg/L 10.3 6.83 13.1 5.44 13.7 11.0 11.6 

Sulfate, filtered 00945 mg/L 32.9 31.2 45.4 15.8 26.6 27.5 25.3 

Dissolved solids, at 180 °C 70300 mg/L 280 258 292 242 198 200 186 

Nutrients:Ammonia, as N, filtered 00608 mg/L e0.03 <0.04 0.05 <0.04 0.12 <0.04 e0.019 
Table 6. Physical properties and concentrations of inorganic major ions, nutrients, and tritium in groundwater samples from confined aquifers in the Lake Valleys, Town of Dryden, New York, 2003–09.—Continued[Sampling site location is shown in figure 27. conf, confined; e, estimated; ft, feet; mg/L, milligrams per liter; μS/cm, microsiemens per centimeter at 25 degrees Celsius (°C); PInformation System (NWIS) parameter code; USGS, U.S. Geological Survey; PWS, public supply well; S&G, sand and gravel; TU, tritium unit; XX, not available; <, less than; CaCO3, calcium carbonate]

Aquifer sampled Upper aquifer Middle aquifer Lower aquifer

Local name :

Lake 

Street 

PWS well

Domestic 

well

Jay Street 

PWS well

Domestic 

well

South 

Street 

PWS well

Dryden 

Lake test 

well

Keith Lane 

test well

USGS site name: TM 202 TM1386 TM 981 TM1940 TM1046 TM 993 TM2724 

Date sampled : 7/28/2003 8/31/2005 7/28/2003 8/29/2005 7/28/2003 12/13/2004 12/16/2009 

USGS station identification number: 422857 076172701 422821 076163701 422854 076174201 422821 076161901 422905 076144901 422755 076164801 422812 076172201 

Nutrients Parm code Units Concentrations of nutirents

Nitrate, as N, NO2+NO3, filtered 00631 mg/L <0.060 e0.04 <0.060 1.78 <0.06 <0.060 e0.02 

Nitrite, as N, filtered 00613 mg/L <0.008 0.023 <0.008 <0.008 <0.008 <0.008 <0.002 Ammonia+organic-N, filtered 00623 mg/L e0.06 0.14 e0.08 0.14 0.15 <0.10 e0.06 

Ammonia+organic-N, unfiltered 00625 mg/L e0.09 e0.09 0.11 e0.06 0.16 <0.10 — 

Orthophosphate, as P, filtered 00671 mg/L <0.02 <0.02 <0.02 <0.02 <0.02 <0.02 e0.004 

Phosphorus, filtered 00666 mg/L e0.003 0.015 0.006 <0.004 0.011 0.004 — 

Phosphorus, unfiltered 00665 mg/L e0.003 <0.004 0.006 <0.004 0.011 0.007 — 

Radiochemical, tritium, unfiltered 07000 TU 9.9 — 9.9 — 7.1 11.1 — 

aU.S. Environmental Protection Agency (USEPA) drinking water advisory taste threshold.bUSEPA secondary maximum contaminant level.cNew York State Department of Health maximum contaminant level.
Table 7. Concentrations of trace metals in groundwater samples from confined aquifers in the Virgil Creek and Dryden Lake Valleys, Town of Dryden[Sampling site location is shown in figure 27. conf, confined; USGS, U.S. Geological Survey; e, estimated; μg/L, micrograms per liter; MHP, mobile home park; Parm code, US

tion System (NWIS) parameter code; PWS, public water supply; XX, not available; <, less than; —, not analyzed]

Aquifer sampled: Upper aquifer Middle aquifer Lower aquifer

Local name: Lake Street PWS well Domestic well Jay Street PWS well Domestic well South Street PWS well Dryden Lake test well Keith Lane test well 

USGS station name: TM 202 TM1386 TM 981 TM1940 TM1046 TM 993 TM2724 

Date sampled: 8/23/2005 8/31/2005 7/28/2003 8/29/2005 7/28/2003 12/13/2004 12/16/2009 

USGS station identification number: 422857 076172701 422821 076163701 422854 076174201 422821 076161901 422905 076144901 422755 076164801 422812 076172201 

Trace metals Parm code Units Concentrations of chemical constituents

Aluminum, filtered 01106 μg/L e0.9 e1.1 e0.8 <1.6 e1.2 — e1.9 

Antimony, filtered 01095 μg/L <0.200 0.242 <0.200 <0.200 e0.176 — e0.035 Arsenic, filtered 01000 μg/L 4.7 e0.1 9.2 <0.2 5.9 — 0.59 Barium, filtered 01005 μg/L 176 61.4 216 30.3 179 — 146 Beryllium, filtered 01010 μg/L <0.060 <0.060 <0.060 <0.060 <0.060 — <0.012 Boron, filtered 01020 μg/L 17 10 16 10 24 — — 

Cadmium, filtered 01025 μg/L 0.103 0.118 0.105 0.244 0.232 — <0.020 

Chromium, filtered 01030 μg/L <0.8 e0.02 <0.8 0.04 <0.8 — <0.12 Cobalt, filtered 01035 μg/L 0.117 0.114 0.112 0.117 0.068 — 0.235 

Copper, filtered 01040 μg/L 1.5 4.3 0.5 8.8 0.9 — <1.0 

Iron, filtered 01046 μg/L 70.5 77.2 43.0 <6.0 92.1 105 227 Lead, filtered 01049 μg/L 0.326 0.093 0.104 e0.049 0.296 — e0.015 Lithium, filtered 01130 μg/L 7.84 8.91 8.92 1.85 4.84 — — 

Manganese, filtered 01056 μg/L 152 54.7 173 4.20 144 114 146 

Molybdenum, filtered 01060 μg/L 1.09 e0.263 0.933 <0.400 2.53 — 1.73 

Nickel, filtered 01065 μg/L 1.66 1.44 1.33 1.96 1.17 — 1.20 

Selenium, filtered 01145 μg/L <0.4 <0.4 <0.4 <0.4 0.6 — 0.04 

Silver, filtered 01075 μg/L <0.200 <0.200 <0.200 <0.200 <0.200 — <0.010 Strontium, filtered 01080 μg/L 216 75.9 236 80.5 415 — — 

Thallium, filtered 01057 μg/L <0.040 <0.040 <0.040 <0.040 <0.040 — — 

Vanadium, filtered 01085 μg/L 1.0 0.2 0.8 e0.1 0.9 — — 

Uranium, natural, filtered 22703 μg/L 0.548 0.468 0.741 0.357 0.662 — 0.478 

Zinc, filtered 01090 μg/L 4.3 8.0 2.8 8.6 12.4 — e2.3 

aU.S. Environmental Protection Agency (USEPA) secondary maximum contaminant level.bUSEPA maximum contaminant level.cNew York State Department of Health (NYSDOH) maximum contaminant level.dUSEPA treatment technique.eUSEPA proposed maximum contaminant level.
Water Quality 55

Table 8. Summary statistics for concentrations of trace elements in groundwater samples collected in the Virgil Creek 

and Dryden Lake valleys, Town of Dryden, New York, 2003–09.

[All concentrations are in micrograms per liter (μg/L); e, estimated; <, less than; —, not applicable]

Constituent Drinking-water 

standard

Number of 

samples

Number of 

samples 

exeeding limit

Groundwater samples

Minimum Median Maximum

Aluminum 50a 7 0 <1.6 e1.1 e1.9 

Antimony 6b,c 7 0 <0.200 e0.035 0.242

Arsenic 10b 7 0 <0.2 1.2 9.2

Barium 2,000b,c 7 0 30.3 146 216

Beryllium 4b,c 7 0 <0.012 <0.060 <0.060

Boron None 7 — 10 15 24

Cadmium 5b,c 7 0 <0.020 0.105 0.244

Chromium 100b,c 7 0 <0.12 <0.8 0.04

Cobalt None 7 — 0.068 0.117 0.235

Copper 1,000a 7 0 <1.0 0.900 8.8

Iron 300a,b 8 0 <0.6 73.8 227

Lead 15d 7 0 <0.080 0.093 0.326

Lithium None 7 — 1.85 6.96 8.92

Manganese 50a

–300c 8 7a–0c 4.2 145 222

Molybdenum None 7 — <0.400 0.933 2.53

Nickel None 7 — 1.17 1.44 2.68

Selenium 50b,c 7 0 <0.4 <0.4 0.6

Silver 100b,c 7 0 <0.010 <0.200 <0.200

Strontium None 7 — 75.9 176 415

Thallium None 7 — <0.040 <0.040 <0.040

Vanadium None 7 — e0.1 0.6 1.0

Uranium 30b 7 0 0.357 0.548 0.797

Zinc 5,000a,b 7 0 e2.3 5.4 12.4

a

U.S. Environmental Protection Agency (USEPA) secondary maximum contaminant level.

b

USEPA maximum contaminant level.

c

New York State Department of Health (NYSDOH) maximum contaminant level.

d

USEPA treatment technique.

e

USEPA proposed maximum contaminant level.
56 Geohydrology, Water Quality, and Simulation of Groundwater Flow, Town of Dryden, Tompkins County, New York

Figure 28. Piper diagram illustrating variability in major ion composition of groundwater in Virgil Creek Valley, Lower Sixmile 

Creek and Willseyville Creek trough, Upper Sixmile Creek and West Branch Owego Creek Valleys, and Upper Buttermilk and 

Danby Creek Valleys, Tompkins County, New York.

Percent

Calcium

1 00

8 0

6 0

4 0

2 0

0

 0

 20

 40

 60

 80

 100

0

2 0

4 0

6 0

8 0

1 00

Chloride 

0

2 0

4 0

60

8 0

1 00

10 0

8 0

6 0

4 0

2 0

0 100

 80

 60

 40

 20

 0

0

2 0

4 0

6 0

8 0

1 0 0

0

2 0

4 0

6 0

80

1 0 0

1 0 0

8 0

60

4 0

2 0

0

1 0 0

80

60

40

20

0

EXPLANATION

Virgil Creek and Dryden Lake valleys groundwater sample

Lower Sixmile Creek and Willseyville Creek trough groundwater sample

Upper Sixmile Creek and West Branch Owego Creek valleys groundwater sample

Percent

Percent

Sulfate plus Chloride

Calcium plus Magnesium

Sulfate

Magnesium

Sodium plus Potassium

Bicarbonate

Upper Buttermilk Creek and Danby Creek valleys groundwater sample
Table 9. Apparent groundwater ages from groundwater samples collected from five wells that tap the confined stratified-drift aquifers in the Virgil Creek aTown of Dryden, Tompkins County, New York[3H, tritium; CFC, chlorofluorocarbon; NP, not possible; pptv, parts per trillion; USGS, U.S. Geological Survey; °C, degrees Celsius]

 Sample site 

name and 

location

USGS site 

identification 

number

Sample 

bottle

Recharge 

temperature, 

in °C

 Sampling 

date 

 Calculated atmospheric 

mixing ratio, in pptv Model piston dates Piston flow age, in years

3H, 

in 

tritium 

units

CFC–11 CFC–12 CFC–113 CFC–11 CFC–12 CFC–113 CFC–11 CFC–12 CFC–113 

TM1046, 

Village of Dryden production well at South Street

422905076144901 1 8.1 7/28/2003 20.4 0.0 0.0 1963.5 1940 1955 40 NP NP 7.1 

2 14.8 0.0 0.0 1961.5 1940 1955 42 NP NP

3 9.2 0.0 0.0 1959 1940 1955 45 NP NP

TM 981, 

Village of Dryden production well at Jay Street

422854076174201 1 9.4 7/28/2003 33.3 1.5 0.0 1966 1944.5 1955 38 NP NP 9.9 

2 3.9 0.0 0.0 1955 1940 1955 49 NP NP

3 27.6 1.1 0.0 1965 1943.5 1955 39 NP NP

TM 202, 

Village of Dryden production well at Lake Street

422857076172701 1 10. 7/28/2003 7.3 0.0 0.0 1957.5 1940 1955 46 NP NP 9.9 

2 23.1 0.78 0.0 1964 1942.5 1955 40 NP NP

3 22.2 1.1 0.0 1964 1943.5 1955 40 NP NP

TM 993, 

USGS test well at Dryden Lake

422755076164801 1 4.0 12/13/2004 3.3 7.3 0.0 1954.5 1950 1953 50 55 52 11.1 

2 4.9 4.7 1.1 1956 1948 1958.5 49 57 46

3 4.7 6.5 1.0 1955.5 1949 1957.5 49 56 47

TM 170, 

Pleasant View Mobile Home Park well at Southworth Road

422828076161701 1 8.8 8/17/2005 175.2 2.5 1.2 1980.5 1946 1958.5 25 60 47.1 10.0 

2 89.2 1.2 0.0 1972.5 1944 1953 33 62 52.6

3 20.5 2.3 0.0 1963.5 1946 1953 42 60 52.6
58 Geohydrology, Water Quality, and Simulation of Groundwater Flow, Town of Dryden, Tompkins County, New York

the mid-1940s and are present in precipitation. In North 

America, the air mixing ratios of CFC–11 and CFC–113 

peaked in about 1993 and 1994, respectively, and the CFC–12 

air mixing ratio peaked in mid-1999 (Elkins and others, 1993). 

Concentrations of CFCs in precipitation and those present in 

groundwater recently derived from precipitation correspond to 

that present in the contemporaneous atmosphere. Atmospheric 

CFC concentrations have been recorded since about 1945 

(Plummer and Busenberg, 2000). The comparison of CFC 

concentrations in a water sample to historical records of 

atmospheric CFC concentrations can indicate the year (after 

1945) in which the water entered the water table. However, the 

estimated age of a groundwater sample can also reflect mixing 

of older and younger water within an aquifer.

Recharge temperature is an important component 

in the interpretation of the age of the water, along with 

concentrations of CFCs (Heaton, 1981; Heaton and Vogel, 

1981; Stute and Schlosser, 1999). The recharge temperatures 

calculated for water from three wells in this study ranged from 

4 to 10 °C (table 9).

Tritium is a radioactive isotope of hydrogen with a halflife of 12.32 years (Lucas and Unterweger, 2000). Based on 

releases to the atmosphere from nuclear testing, 3

H can be 

used as a tracer to estimate whether groundwater has been 

recharged before or after 1953. The standard unit of measure 

for 3

H is a tritium unit (TU), in which 1 TU is equivalent 

in terms of radioactivity to 3.2 picocuries per liter (pCi/L). 

The greatest concentrations of 3

H (greater than 500 TU) 

occurred following periods of atmospheric testing of nuclear 

weapons, which began in 1952 and peaked in 1963–4 (Clark 

and Fritz, 1997). Atmospheric concentrations have gradually 

declined since 1963–4, and present-day groundwater typically 

contains less than 1 to 10 TU (Clark and Fritz, 1997). Natural 

(prenuclear age) levels of 3

H in precipitation are on the order 

of 1 to 5 TU. The relative age of the groundwater (time since 

it entered the aquifer and ceased contact with the atmosphere) 

can be estimated through a comparison of the 3

H concentration 

in a water sample with the recorded historical changes in 

concentration in the atmosphere, taking into account the 

half-life decay. Groundwater that does not contain detectable 

3

H (less than 0.8 TU) can be assumed to have been recharged 

before 1953, and groundwater that does contain detectable 3

H 

(more than 0.8 TU) is assumed to contain some component 

of groundwater that was recharged after 1953 (Cordy and 

others, 2000). 

Five samples were collected and analyzed for CFCs, 

dissolved gases, and 3

H to estimate the age of the groundwater 

in the study area. Three samples were collected on July 

28, 2003, from the Village of Dryden municipal wells 

(TM1046, TM 981, and TM 202), one sample was collected 

on December 13, 2004, from the test well at Dryden Lake 

(TM 993), and one sample was collected on August 17, 2005, 

from a mobile home park well at Southworth Road (TM 170). 

Concentrations of 3

H in the five groundwater samples from 

this study ranged from 7.1 to 11.1 TU (table 9). The 3

H 

concentrations were used along with concentrations of CFCs 

to estimate the apparent age of groundwater. The results of the 

age-dating samples are listed in table 9.

Based on the CFC and 3

H analyses for the three Village 

of Dryden production wells, the apparent groundwater ages 

were as follows: before the 1940s to early 1960s for the well 

finished in the lower confined aquifer (TM1046) and early 

1970s or younger for the wells finished in the middle and 

upper confined aquifers (TM 981 and TM 202, respectively). 

The results also indicated that the groundwater sampled from 

the middle and upper confined aquifers were possibly mixtures 

of water of different ages.

The results of the CFC analyses for the test well at 

Dryden Lake (TM 993, lower aquifer) indicated that the 

apparent age of water was late 1940s to late 1950s; however, 

the 3

H concentration of 11.1 TU (table 9) indicated that the 

water was 1970s or later. Samples with values between 5 and 

15 TU indicate that the water probably entered the aquifer 

sometime after 1970. Because of the disagreement of ages 

determined by CFC and the 3

H dating methods, the age of 

water sampled from TM 993 is uncertain.

The results of the CFC analyses for the mobile home park 

well at Southworth Road (TM 170) indicated that the apparent 

age of water was probably mid-1940s or older based on the 

CFC–12 and CFC–113 concentrations. However, the CFC–11 

concentration indicated that the apparent age was mid-1960s 

to early 1980s, but the laboratory noted there may have 

been CFC–11 contamination in this sample (enrichment that 

results in an apparent age younger than in actuality) and that 

the concentrations of CFC–11 in the three samples that were 

analyzed decreased with time, both phenomena suggesting 

the results may not be reliable. The 3

H concentration of 10 TU 

indicated that the water was 1970s or later. It is possible that 

the CFC–12 and CFC–113 concentrations have also decreased 

because they have undergone degradation, which results in 

apparent ages that are older than in actuality. Although there is 

no evidence for aerobic degradation of CFCs in groundwater, 

CFC–11, CFC–12, and CFC–113 can all be degraded in 

sulfate-reducing and methanogenic anaerobic environments 

(Plummer and Busenberg, 2000).

Simulation of Groundwater Flow

The groundwater flow through the stratified-drift aquifer 

system in the Virgil Creek and Dryden Lake Valleys in the 

Town of Dryden and in part of the Owego Creek Valley, 

Town of Harford was simulated using the computer program 

MODFLOW–2000, a three-dimensional, cell-centered, 

finite-difference, saturated-flow model developed by the 

U.S. Geological Survey (McDonald and Harbaugh, 1988). 

Areas that potentially contribute recharge to the Village 

of Dryden municipal production wells were calculated 

using the computer program MODPATH (Pollock, 1989), 

a semianalytical particle-tracking program that uses 
Simulation of Groundwater Flow 59

groundwater heads and fluxes predicted through steady-state 

groundwater-model simulation to trace the flow lines in 

the aquifer.

Model Design

A preprocessing and postprocessing program, 

Groundwater Modeling System (GMS) version 7.1 (build 

date October 11, 2010; Aquaveo, 2010), was used to input 

data for MODFLOW–2000 and MODPATH and generate 

output graphics and statistical analyses. Because the Village of 

Dryden has been withdrawing water for a long period of time 

(since the 1940s) at a relatively small rate (in 2008, the rate 

was 0.192 Mgal/d or 133 gal/min) and the interest of this study 

is in long-term trends rather than seasonal or other short-term 

effects, the aquifer system is assumed to be near steady-state. 

Therefore, a steady-state simulation was used to compute 

the hydraulic-head distribution and groundwater budgets 

and to estimate the rate of groundwater flow. The model was 

calibrated to measured groundwater levels made throughout 

the study area and to flow rates in a reach of Virgil Creek in 

the vicinity of the Virgil Dam.

The model was based on the generalized geologic 

and hydrologic sections presented previously in this report 

(figs. 13, 14, 18, and 19). The model is only a simplified 

representation of actual aquifer conditions because (1) the 

geology is complex, (2) the distribution of hydraulic properties 

is unknown in most of the simulated area, and (3) there is 

a scarcity of geohydrologic data in some parts of the study 

area. However, the model is a valuable tool that can be used 

to better understand how the hydrologic system works and 

to estimate the sources of recharge within areas contributing 

recharge to the Village of Dryden production wells.

Model Grid and Layers

The three confining layers and the three aquifers 

that form the geohydrologic framework of the valley-fill 

deposits (figs. 18 and 19) were represented by six model 

layers (fig. 29). Water-bearing zones in the bedrock were not 

explicitly simulated in the model because (1) studies in other 

areas indicate that the Devonian shales and siltstones transmit 

relatively little groundwater compared with the overlying sand 

and gravel units in this area and (2) there is little information 

on the hydraulic properties of the bedrock or the hydraulichead relation between the bedrock and the unconsolidated 

deposits within the study area.

The model represents an area of 5.4 mi2 and extends from 

5.3 mi southeast of the Village of Dryden to 1.3 mi northwest 

of the Hamlet of Harford (fig. 30A). The model grid included 

159 rows and 73 columns in each of the six layers, with a 

uniform cell size of 200 by 200 ft.

Model layers 1, 3, and 5 represent the upper, middle, 

and lower confining units, respectively (figs. 18, 19, and 29). 

Layers 1 and 3 each represent a 10- to 60-ft-thick till unit, 

whereas layer 5 represents a 60- to 100-ft-thick confining 

unit comprising mostly fine-grained lacustrine sediments and 

some till (figs. 13 and 14). Model layers 2, 4, and 6 (fig. 29) 

represent confined sand and gravel aquifer units (figs. 18 and 

19) of unknown origin. The model does not include surficial 

unconfined units because they are small, discontinuous, and 

thinly saturated; it would have been difficult to prevent these 

cells from becoming dry cells, which would result in model 

instability, and attempting to include these deposits would not 

have substantially improved the results.

Model layers 1 through 6 contain 21,497 active cells. 

Layer thicknesses were initially assigned by using the Solid 

module of GMS to a construct a three-dimensional model of 

stratigraphy using borehole data. Subsequently, the thicknesses 

of model layers in some areas were changed manually upon 

visual inspection of well logs and using geological concepts 

and knowledge of the hydrostratigraphy of other similar 

confined aquifers in the county (Miller, 2009; Miller and 

Karig, 2010).

Boundary Conditions

Several types of boundary conditions that represent 

inflows and outflows of water to and from the aquifer 

system were specified in the model (figs. 29 and 30). Natural 

boundaries were used where possible, but arbitrary boundaries 

were used to limit the northern, southern, and eastern extents 

of the model.

No-Flow Boundaries

No-flow lateral boundaries were used in model layers 1 

through 6 to represent the contact between the aquifer system 

and the shale bedrock at the valley wall. However, a specified 

flux was included to represent a small amount of seepage from 

the adjacent bedrock to the simulated valley-fill units.

Specified-Flux Boundaries

A specified-flux boundary (Recharge package) was used 

to represent direct recharge from precipitation to the upper 

confining unit (layer 1) and to the upper confined aquifer unit 

(layer 2) where the upper confining unit had been removed 

by erosion near the Virgil Creek Dam area (figs. 14 and 19). 

Groundwater recharge was nonuniformly distributed over the 

model area to the topmost active layer. The average annual 

recharge from direct precipitation was estimated to be 0 inches 

per year (in/yr) in low areas in the northern part of the study 

area where the hydraulic head in the upper aquifer is near or 

above the top of the upper confining unit (rejected recharge 

due to artesian flowing conditions), 2.2 in/yr (0.0005 ft/d) 

where the upper confining unit is above the altitude of the 

hydraulic head in the upper aquifer in the north part of the 

study area, 8.3 in/yr (0.0019 ft/d) where the upper confining 

unit consists of a thin weathered till at land surface in the 

south and central part of the valley, 11 in/yr (0.0025 ft/d) 
60 Geohydrology, Water Quality, and Simulation of Groundwater Flow, Town of Dryden, Tompkins County, New York

Figure 29. Schematic diagrams of the model used in the study of the stratified-drift aquifer system in Virgil Creek and Dryden Lake 

Valleys, Town of Dryden, Tompkins County, New York: A, vertical cross-section of model and representation of hydraulic connections 

between model layers and bedrock valley walls and B, cell dimensions and variables used in computation of flow rates between cells.

Vertical section of model

EXPLANATION

Upper confining unit (layer 1)

Upper confined aquifer (layer 2)

Middle confining unit (layer 3)

Middle confined aquifer (layer 4)

Lower confining unit (layer 5)

Model

layer

1

2

3

4

5

6

Recharge

Upland runoff

(mostly in the 

southern part of

Recharge Recharge the study area)

Lower confined aquifer (layer 6)

No flow

Predominantly horizontal flow within model layer

Hydraulic connections with fractured bedrock 

along valley walls. Seepage from bedrock simulated

with injection wells 

Predominantly vertical flow within model layer

Vertical hydraulic conductivity

K Horizontal hydraulic conductivity

Kv

Cell dimensions and variables used in computation of flow rates.

EXPLANATION

Horizontal flow

Vertical flow

Direction of flow

Cross-sectional area, horizontal flow

Cross-sectional area, vertical flow

QH

AH

QV

200 feet

200 feet

Thickness

is variable

Model cell

QH AH

QV

AV

AV

Upland runoff

(mostly in the 

southern part of

the study area)

A

B

K

K

K

Kv

Kv

Kv
Simulation of Groundwater Flow 61

Figure 30. Boundary conditions in groundwater-flow model in stratified-drift aquifer study area in the Virgil Creek, Dryden Lake, and 

Owego Creek Valleys, Tompkins and Cortland Counties, New York: A, Upper confining unit (model layer 1), B, middle and lower confining 

units (model layers 3 and 5) and upper, middle, and lower confined aquifer units (model layers 2, 4, and 6).

0 1 2 MILES

0 1 2 KILOMETERS

76°19' 76°18' 76°17' 76°16' 76°15' 76°14' 76°13' 42°31'

42°30'

42°29'

42°28'

42°27'

42°26'

42°25'

Base from TOPO! 2003 ©National Geographic, 

scale 1:24,000

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EXPLANATION

Head-dependent boundaries Specified-flux boundaries General head cells (lakes, ponds, 

and wetlands)

River cells (streams and bogs)

Drain cells (bluffs along eroded 

stream gorge)

Well cell that simulates recharge from 

groundwater inflow from bedrock along the 

valley walls and runoff and from unchanneled 

uplands

Well cell that simulates groundwater outflow 

through the southern end of the model

Well cell that simulates groundwater inflow 

through the eastern end of the model

!( Well cell that simulates groundwater outflow 

through the northern end of the model

Boundary of model grid

Boundary of stratified-drift aquifer

A

Hamlet of

Harford
62 Geohydrology, Water Quality, and Simulation of Groundwater Flow, Town of Dryden, Tompkins County, New York

Figure 30. Boundary conditions in groundwater-flow model in stratified-drift aquifer study area in the Virgil 

Creek, Dryden Lake, and Owego Creek Valleys, Tompkins and Cortland Counties, New York: A, Upper confining unit 

(model layer 1), B, middle and lower confining units (model layers 3 and 5) and upper, middle, and lower confined 

aquifer units (model layers 2, 4, and 6).—Continued

0 1 2 MILES

0 1 2 KILOMETERS

76°19' 76°18' 76°17' 76°16' 76°15' 76°14' 76°13' 42°31'

42°30'

42°29'

42°28'

42°27'

42°26'

42°25'

Base from TOPO! 2003 ©National Geographic, 

scale 1:24,000

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EXPLANATION

Head-dependent boundaries

Specified-flux boundaries

River cells in layer 2 where Virgil Creek 

is in a gorge and where layer 1 is absent

(has been removed by erosion)

Well cell that simulates recharge from groundwater inflow from bedrock along the valley 

walls and runoff and from unchannel uplands

Well cell that simulates groundwater outflow 

through the southern end of the model

Well cell that simulates groundwater inflow 

through the eastern end of the model

(! Well cell that simulates groundwater outflow 

through the northern end of the model

Boundary of model grid

Boundary of layers 2 

through 5

Model boundary (layer 6)

B
Simulation of Groundwater Flow 63

where relatively permeable but poorly sorted kame deposits 

lie along the east side of the valley, and 17.5 in/yr (0.004 ft/d) 

at the moraine in the southern part of the study area where 

the upper confining unit consists of heterogeneous material 

(reworked sand and gravel mixed with till consisting of a finegrained matrix) and locally contains windows of permeable 

sediment that can readily transmit recharge from precipitation 

and tributaries that lose water as they flow over the valley 

floor. There was no recharge from precipitation included (1) in 

low-lying areas of the northern part of the study area where 

the hydraulic head is above the top of the upper aquifer and 

upper confining unit, (2) in areas of large ponds and wetlands, 

and (3) where Dryden Lake occupies the valley.

A specified-flux boundary, represented by discharging 

wells (pumped wells), was used to represent the Village of 

Dryden municipal production wells. Pumping is distributed 

between three pumping stations—TM1046 at South 

Street, TM 981 at Jay Street, and TM 202 at Lake Road 

(fig. 25). During 2005–7, the total daily average groundwater 

withdrawal from the village municipal pumping wells was 

about 242,000 gal/d (32,350 cubic feet per day (ft3

/d)); about 

125,000 gal/d (16,700 ft3

/d) was from South Street pumping 

station, about 93,500 gal/d (12,500 ft3

/d) from the Jay Street 

pumping station, and about 23,500 gal/d (3,140 ft3

/d) from 

Lake Road pumping station. Domestic and apartment wells 

were not included as discharging wells because most of that 

pumped water is returned to the groundwater system via 

septic systems.

Although bedrock was not formally represented in 

this model because of the assumption that shale transmits 

relatively little groundwater, a small amount of inflow from 

the bedrock to the valley-fill deposits probably does occur 

(Yager and others, 2001). Therefore a specified flux boundary, 

represented by injection wells, was used in active cells that 

border the bedrock valley walls to represent the groundwater 

inflow from bedrock (layers 1 through 6). In addition to the 

hydraulic gradient and cross-sectional flow area, the amount 

of groundwater flux from the bedrock uplands to the valleyfill geohydrologic units is controlled by the unit that has the 

lowest hydraulic conductivity—that of the weathered and 

fractured bedrock or that of the valley-fill sediments. For the 

confining units, the hydraulic conductivity is lower than that 

of the weathered and fractured shale. A hydraulic conductivity 

value of 2.5 ft/d was used for the study area; the value is based 

on the weathered and fractured bedrock in the Genesee Valley 

of central New York as estimated by Yager and others (2001). 

The horizontal hydraulic conductivity of the upper confining 

unit (weathered till) in this study area is estimated to be 1 ft/d, 

and those of the unweathered middle and lower confining 

units are estimated to be 0.25 ft/d and 0.3 ft/d, respectively. 

Therefore, the groundwater flux from the bedrock uplands is 

controlled, in large part, by the confining units because they all 

have lower hydraulic conductivities than the bedrock. Darcy’s 

law (equation 2) was used to estimate the flux of groundwater 

inflow from the adjacent valley walls into the confining beds 

in the simulated study area:

Q = KIA, (2)

where

Q = discharge, the volume of water discharged 

over a given time;

K = hydraulic conductivity;

I = hydraulic gradient, measured as change in 

height (Δh) over change of length (Δl) or 

rise over run or slope (dimensionless); and

A = cross-sectional flow area.

Using the above equation, the estimated flux into the 

confining units (represented by injection wells in cells along 

the valley walls) ranged from 6 ft3

/d for the middle and lower 

confining units to 25 ft3

/d for the upper confining unit, 

where 

K = 1 ft/d, 0.25 ft/d, and 0.3 ft/d for the upper, 

middle, and confined aquifers, respectively,

I = 0.005 ft/ft, and 

A = 5,000 ft2.

In areas where the aquifers abut the valley walls, the flux 

of groundwater inflow from the adjacent valley walls into the 

confined aquifers is controlled, in large part, by the hydraulic 

conductivity of the weathered bedrock (about 2.5 ft/d), which 

is lower than that of the aquifer units (120 ft/d for the upper 

confined aquifer, 100 to 130 ft/d for the middle confined 

aquifer, and 30 to 300 ft/d for the lower confined aquifer). 

Using Darcy’s equation above, the estimated groundwater 

flux from bedrock into the aquifer units was computed and 

represented in the model by injection wells in cells along the 

valley walls. The computed recharge for a cell along the valley 

wall was 100 ft3

/d for the upper confining unit and ranged 

from 35 to 75 ft3

/d for the middle and lower confining units, 

where 

K = 2.5 ft/d for the bedrock, 

I = 0.005 ft/ft, and 

A ranged from 3,000 to 8,000 ft2.

In some places in the southern part of the study area, 

recharge from upland sources can be more than in the northern 

part of the study area because, in addition to groundwater 

inflow from adjacent bedrock, some unchanneled runoff from 

adjacent hillsides seeps into the upper aquifer where the upper 

confining unit is thin, discontinuous, or absent, such as at some 

kame terraces along the valley walls and at the Valley Heads 

Moraine. The recharge from uplands in the southern part of the 

study area is at least equal to and, in some places, greater than 

that in the northern part of the study area where the confining 

units abut the valley walls and prevent runoff from entering 

the upper aquifer. The maximum recharge to the model from 

the upland areas in the southern part of the study area was 

determined by (1) dividing the uplands into surface-water 

subbasins, (2) determining the drainage area that contributes 

runoff to the valley in each subbasin, (3) multiplying the 

contributing upland area by the average unit-area base flow, 

and (4) dividing this flow by the number of perimeter cells of 
64 Geohydrology, Water Quality, and Simulation of Groundwater Flow, Town of Dryden, Tompkins County, New York

the modeled area adjacent to the subbasin and applying the 

result to these cells. During calibration, the extra recharge 

from unchanneled runoff from adjacent hillsides was reduced 

in the southern part of the study area because simulated water 

levels were too high. The recharge (represented in the model 

by injection wells in cells in layer 2 along the valley walls) 

from upland sources in the southern part of the study area is 

estimated to range from 100 to 200 ft3/d.

A specified-flux boundary, represented by discharging 

wells, was used to simulate groundwater outflow through the 

northern and southern boundaries in the Dryden Lake Valley. 

The flux was initially estimated using Darcy’s law (equation 

2) and then modified during the calibration process. The final 

calibrated groundwater fluxes for the three confined aquifer 

layers—2, 4, and 6—out for each cell at the northern boundary 

of the model are 500 ft3/d, 1,500 ft3/d, and 1,000 ft3/d, 

respectively, and at the southern boundary of the model, 

400 ft3/d, 400 ft3/d, and 1,000 ft3/d, respectively.

A specified-flux boundary, represented by injection wells, 

was used to simulate groundwater inflow into the eastern 

(upgradient) boundary in the Virgil Creek Valley (1,500 ft 

east of the Virgil Creek Dam). The flux was initially estimated 

using Darcy’s law (equation 2) and then modified during the 

calibration process. The final calibrated groundwater fluxes 

for each cell at the eastern boundary of the model for the three 

confined aquifer layers—2, 4, and 6—are 500 ft3/d, 700 ft3/d, 

and 2,000 ft3/d, respectively.

Head-Dependent Boundaries

The General Head package in MODFLOW–2000 was 

used to simulate flow in or out of a cell that represents lakes, 

ponds, and wetlands. General head conditions are specified 

by assigning a head and a conductance to a selected set of 

cells. If the water-table altitude rises above the specified head, 

then water flows out of (discharges from) the aquifer. If the 

water-table altitude falls below the specified head, then water 

flows into (recharges) the aquifer. In both cases, the flow rate 

is proportional to the head difference and the conductance. 

The altitude of the water surface of Dryden Lake was 

determined through leveling. The water-surface altitudes of 

small ponds and wetlands were derived from LiDAR data with 

3.28-ft (1 meter) horizontal resolution and about 1-ft vertical 

accuracy. The conductance (C) for model cells representing 

head-dependent boundaries was computed from the relation:

A C K

l = , (3)

where

C = conductance,

K = hydraulic conductivity,

A = cross-sectional flow area, and

l = length of flow path between cell center and 

model boundary.

Flow between the aquifer and the surface-water body (Q) 

is referred to as a head-dependent flux and is governed by the 

following equation (McDonald and Harbaugh, 1988):

Q = C (H – h), (4)

where

Q = discharge, flow between the aquifer and 

stream;

C = conductance of the streambed material;

H = altitude of head in the stream; and

h = altitude of head in the aquifer.

The River package in MODFLOW–2000 was used to 

simulate flow of water between the upper confining unit and 

streams and, where the upper confining unit was removed in 

the area of the Virgil Creek Dam, between the upper aquifer 

(locally unconfined in this area) and Virgil Creek. The rate at 

which water moves between stream and aquifer is dependent 

on the head difference between the two, as well as on the 

vertical conductance of the streambed material. Stream-stage 

estimates were computed from land-surface altitudes derived 

from leveling at several sites and from LiDAR data (about 1-ft 

vertical accuracy). The thickness and hydraulic conductivity 

of the riverbed were not known, and stream widths were 

approximated between locations where measurements were 

made. The thickness of the riverbed was assumed to be 1 ft. 

The hydraulic conductivity of the riverbed was not measured 

but was estimated to range from 1 to 25 ft/d on the basis of 

values used for other groundwater modeling studies done 

in the northeastern United States (Miller and others, 1998; 

Miller, 2000a; Carleton and Gordon, 2007). Flow between the 

aquifer and the stream is referred to as a head-dependent flux 

and is governed by equations 3 and 4.

The K values for river cells representing flows to and 

from streams were assumed to be as follows:

• 50 ft/d, where Virgil Creek flows on coarse-grained 

alluvium and in a channel that has been dredged and 

reworked in the vicinity of Virgil Creek Dam;

• 1 to 2 ft/d, where Virgil Creek flows on till or alluvium 

downstream from Virgil Creek Dam;

• 1 ft/d, for the inlet and outlet to Dryden Lake;

• 1 to 10 ft/d for tributary streams that lose water 

where they flow on coarse alluvial fans and morainal 

deposits; and

• 0.1 to 0.5 ft/d, for small tributary streams that lose 

water where they flow on kame terraces, alluvium, 

or till.

The ratio A/l in equation 3 was based on the length, width, and 

thickness of the stream channel as follows:
Simulation of Groundwater Flow 65

• cells representing Virgil Creek: 0.125 ft,

• cells representing inlet to Dryden Lake: 0.05 ft,

• cells representing outlet to Dryden Lake: 0.0125 ft, and

• cells representing small tributaries: 0.015 to 0.05 ft.

The Drain package in MODFLOW was used to simulate 

groundwater that seeps out from the till bluffs (layer 1) in 

the eroded gorge cut by Virgil Creek in the vicinity of the 

Virgil Creek Dam (fig. 30A). The Drain package allows water 

to leave the model domain if the head in a cell containing a 

drain is higher than the designated drain stage. Drains are 

active only when the water table in the layer is higher than 

the altitude of the drain. The altitude of the drains used in the 

model ranged from 1,163 ft to 1,211 ft. The model calculates 

the rate of seepage between the drain and the aquifer using the 

following equation (McDonald and Harbaugh, 1988):

Q = C (h – d), (5)

where

Q = discharge, seepage rate;

C = hydraulic conductance of the interface 

between the modeled layer and the drain;

h = altitude of the hydraulic head in the model 

cell; and

d = altitude of the drain.

A C value of 20 ft3/d (computed using equation 3) was 

used in equation 5, where vertical K value was 1 ft/d, A

value was 4,000 ft2

 (thickness of geohydrologic unit of 20 ft 

multiplied by the width of model cell of 200 ft), and the value 

of l was 200 ft.

Model Calibration

The model was calibrated using a combination of 

automated parameter estimation and trial-and-error techniques. 

Simulated and measured water levels throughout the study 

area and loss of streamflow in a reach of Virgil Creek near 

the dam were compared to determine the combination that 

resulted in the lowest cumulative error. The model was 

calibrated using estimated average annual recharge conditions 

and average groundwater withdrawals by the Village of 

Dryden for 2005–7. The average daily pumping rates for 

2005–7 for the Village of Dryden production wells TM1046, 

TM 993, and TM 202 were 125,300 gal/d (16,750 ft3

/d), 

93,900 gal/d (12,550 ft3

/d), and 30,600 gal/d (4,100 ft3/d), 

respectively. Because groundwater has been withdrawn from 

the aquifer system by Village of Dryden production wells 

since the mid-1940s and there are no water-level data for the 

time before pumping began, the model could not be calibrated 

to steady-state, nonpumping conditions.

Model Parameters

Initially 52 model parameters were estimated from 

precipitation records, results of aquifer tests, examination of 

drill cuttings and split-spoon cores during test drilling, and 

interpretation of drillers’ logs. Then 39 (horizontal and vertical 

hydraulic conductivities, recharge, and streambed conductance 

of Virgil Creek in the vicinity of the dam) of the 52 parameter 

values were adjusted using a nonlinear, parameter-estimation, 

inverse model (PEST, version 12.0; Doherty and Hunt, 2010), 

and the remaining 13 parameters (streambed conductance, 

specified flux along the valley walls, and porosity) were 

fixed (table 10). Some parameters (horizontal hydraulic 

conductivities and streambed conductances) were further 

changed when improvements in model results were identified 

through improvement of the sum of the root-mean-squared 

errors. Adjustments continued until the model-computed 

values (residuals) matched the field-observed values to an 

acceptable level of agreement of less than 5 ft. The final 

values of parameters used in the model are given in table 

11 and the zones of horizontal hydraulic conductivity of the 

upper (layer 2), middle (layer 4), and lower (layer 6) confined 

aquifers used in the numerical simulation are shown on 

figure 31.

The model was most sensitive to changes in recharge 

and horizontal hydraulic conductivity in model layers 2 and 

4 (upper and middle confined aquifers, respectively) in the 

northern part of the study area and to bed conductance of 

Virgil Creek in the vicinity of Virgil Creek Dam (figs. 31 

and 32). The model was slightly less sensitive to changes in 

recharge in the central part of the study area and in horizontal 

hydraulic conductivity of layer 6 (lower confined aquifer) and 

vertical hydraulic conductivity of layer 1 (upper confining 

unit) in the northern part of the study area. The model was 

less sensitive to changes in vertical hydraulic conductivity of 

layer 5 and to horizontal hydraulic conductivities of layers 

2, 4, and 6 in the southern part of the study area. The model 

was insensitive to vertical hydraulic conductivity in layer 1 

in the central and southern parts of the study area, to vertical 

hydraulic conductivity of layer 3, and to horizontal hydraulic 

conductivity of layer 6 in the southern part of the study area.

Steady-state simulations were used to produce a model 

that would approximate the water levels for (1) long-term 

average groundwater-level conditions, (2) average municipal 

well pumping rates for 2005–7, and (3) streamflow measured 

in Virgil Creek at the Virgil Creek Dam on May 10, 2007, 

which was near the median annual base-flow conditions 

as determined by a hydrograph-separation analysis of a 

nearby streamgage of similar hydrologic setting. Because 

precipitation was above average for 2005–7, the model was 

calibrated to some heads that represent a slightly wetter than 

average period.
66 Geohydrology, Water Quality, and Simulation of Groundwater Flow, Town of Dryden, Tompkins County, New York

Table 10. Numbers of parameters that represent the stratified-drift aquifer system in the Virgil Creek and Dryden Lake valleys, 

Tompkins County, New York, as estimated and fixed in the nonlinear, parameter-estimation inverse model.

[—, no parameter specified; X, fixed parameter]

Aquifer property

Model layer

1 2 3 4 5 6

Upper 

confining 

unit

Upper 

confined 

aquifer

Middle 

confining 

unit

Middle 

confined 

aquifer

Lower 

confining 

unit

Lower 

confined 

aquifer

Horizontal hydraulic conductivity:

Estimated — 4 — 3 — 12

Fixed — — — — — —

Vertical hydraulic conductivity:

Estimated 7 — 1 — 1 —

Fixed — — — — — —

Recharge, estimated 7 1a — — — —

Streambed conductance, estimated (near dam only) — 3 — — — —

Other fixed head-dependant and specified-flux properties and porosity:

Streambed conductance X — — — — —

Specified flux along valley walls X X X X X X

Porosity X X X X X X

Total:

Estimated (39) 14 8 1 3 1 12

Fixed (13) 3 2 2 2 2 2

a

Recharge specified in area of layer 2 where layer 1 is absent (removed by erosion).
Simulation of Groundwater Flow 67

Table 11. Parameter values estimated for the groundwater-flow model of the stratified-drift aquifer system in the Virgil Creek and 

Dryden Lake Valleys, Tompkins County, New York.

[gal/d, gallons per day; ft/d, feet per day; ft2/d, square feet per day; ft3/d, cubic feet per day; in/yr, inches per year]

Variable Value

Specified-flux boundary:

Recharge package:

Moraine, in/yr (ft/d) 17.5 (0.004)

Backside of moraine, in/yr (ft/d) 3.5–8.3 (0.0008–

0.0019)

Floodplain at Virgil Creek Dam, in/yr (ft/d) 8.8 (0.002)

Well package:

Large withdrawal wells

Village of Dryden South Street pumping station, gal/d (ft3

/d) 125,000 (16,700)

Village of Dryden Jay Street pumping station 93,500 (12,500)

Village of Dryden Lake Road pumping station 23,000 (3,140)

Upland sources of rechargea

Groundwater inflow from adjacent bedrock (represented by injection wells) 

Groundwater inflow into upper confining unit (layer 1) (ft3

/d) 25

Groundwater inflow into the middle (layer 3) and lower confining units (layer 5) (ft3

/d) 6 

Groundwater inflow into upper confined aquifer (layer 2) (ft3

/d) 100

Groundwater inflow into the middle and upper confined aquifers (layers 4 and 6) (ft3

/d) 35–75

Groundwater outflow through confined aquifers at the northern and southern boundaries in the Dryden Lake 

valley

Groundwater fluxes out of each cell at the northern boundary of the model for the three aquifers—layers 2, 4, 

and 6 (ft3

/d)

500, 1,500, 1,000, 

respectively

Groundwater fluxes out of each cell at the southern boundary of the model for the three aquifers—layers 2, 4, 

and 6 (ft3

/d)

400, 400, 1,000, 

respectively

Groundwater inflow through the confined aquifers at the eastern boundary in the Virgil Creek valley

Groundwater fluxes into each cell at the eastern boundary of the model for the three aquifers—

layers 2, 4, and 6 (ft3

/d)

500, 700, 2,000, 

repectively

Head-dependent boundaries:

General-head package:

Vertical hydraulic conductivity of Dryden Lake (ft/d) 250,000

Vertical hydraulic conductivity of small ponds and wetlands (ft/d) 0.01–0.3

River package:

Vertical hydraulic conductivity of Virgil Creek in the vicinity of Virgil Creek Dam (ft/d) 50

Vertical hydraulic conductivity of Virgil Creek downstream of the Virgil Creek Dam (ft/d) 1–2 

Vertical hydraulic conductivity of the inlet and outlet to Drydan Lake (ft/d) 1

Vertical hydraulic conductivity of tributary streams that lose water where they flow on alluvial fans and 

morainal deposits (ft/d)

1–10

Vertical hydraulic conductivity of small tributary streams that lose water where they flow on kame terraces, 

alluvium, or till (ft/d)

0.1–0.5

Drain package, conductance of drain cell (ft2

/d)/(ft) 20

Hydraulic conductivity (ft/d):

Layer 1 (vertical hydraulic conductivity) 1

Layer 2 (horizontal hydraulic conductivity):
68 Geohydrology, Water Quality, and Simulation of Groundwater Flow, Town of Dryden, Tompkins County, New York

Table 11. Parameter values estimated for the groundwater-flow model of the stratified-drift aquifer system in the Virgil Creek and 

Dryden Lake Valleys, Tompkins County, New York.—Continued

[gal/d, gallons per day; ft/d, feet per day; ft3/d, cubic feet per day; in/yr, inches per year]

Variable Value

Moraine 210

Backside of moraine 70–120

Layer 3 (vertical hydraulic conductivity) 0.025

Layer 4 (horizontal hydraulic conductivity) 100–130

Layer 5 (vertical hydraulic conductivity) 0.03

Layer 6 (horizontal hydraulic conductivity):

Southern part (moraine area) 300

Northern part (backside of moraine) 35–200

Model error, root mean square error 3.8

a

Recharge derived from 11.3 square miles of upland area

A hydrograph-separation analysis was not done to 

determine the median annual base flow at the Virgil Creek at 

State Highway 13 streamgage site because of the following 

limitations at that site: (1) a flood-control reservoir (Virgil 

Creek Dam) that slowly releases runoff after a storm, which 

would result in an apparent decrease in surface runoff and 

an apparent increase in base flow, and (2) a short period of 

record (2 years; a long-term station (more than 10 years) is 

more representative of long-term climatological conditions 

than a short-term station and provides a more reliable baseflow estimate because extremes have less weight in the 

determination of base-flow characteristics). Because of these 

limitations, the median annual base flow was computed using 

discharge data from the Sixmile Creek at Bethel Grove, 

New York (USGS station 4233300, not shown on map), 

11 mi southeast of Dryden. The Sixmile Creek at Bethel Grove 

station has more than 10 years of record and contains no dams 

or lakes in the upgradient drainage basin. The Sixmile Creek 

at Bethel Grove and Virgil Creek at State Highway 13 have 

similar-size drainage areas (39 mi2

 and 30 mi2, respectively) 

and similar geologic settings: both drain the backside of 

the Valley Heads Moraine, have predominantly till at land 

surface, and contain multiple confined aquifers (Miller and 

Karig, 2010). The median base flow of Sixmile Creek at 

Bethel Grove, as determined through a hydrograph-separation 

analysis using the HYSEP computer program (Sloto and 

Crouse, 1996), was 36.8 ft3

/s from 1996 to 2007. On the day 

that the seepage measurements were made in Virgil Creek at 

the dam site (May 10, 2007), the flow at the Sixmile Creek at 

Bethel Grove was 39 ft3

/s, which was close to annual median 

base-flow conditions.

Model Fit

Hydraulic heads computed from the steady-state 

simulation were compared with the water-table altitudes 

measured in 57 wells (fig. 33), and groundwater discharges 

computed from the steady-state simulation were compared 

with base flow estimated from stream discharge measured at 

Virgil Creek on May 10, 2007 (fig. 12A). A set of calibration 

targets was created to provide feedback on the magnitude, 

direction (high or low), and spatial distribution of the 

calibration error. Water-level residuals (measured minus 

simulated water-level altitudes) for the stratified-drift aquifer 

system are shown on figures 33 and 34 and table 12. The 

calibration target (fig. 33) is drawn such that the height of the 

target is equal to twice the confidence interval (plus interval 

on top, minus interval on bottom). The center of the target 

corresponds to the observed value. The top of the target 

corresponds to the observed value plus the interval and the 

bottom corresponds to the observed value minus the interval. 

The colored bar represents the error. If the bar lies entirely 

within the target (plus or minus (±) 5 ft), the color bar is 

drawn in green. A simulated head within the ±5-ft confidence 

interval was considered a good agreement with the measured 

value because the average annual fluctuation of water levels 

in the aquifers in the study area ranges from 5 to 6 ft (figs. 23 

and 24B) and the water-level measurements used to calibrate 

the model (that were taken during various seasons and years) 

would be within ±5 ft of representing long-term average 

annual water-level conditions. Therefore, a model calibration 

target of less than a 5-ft residual is a reasonable goal, and the 

residual plots for heads indicate that the model simulates the 
Simulation of Groundwater Flow 69

0 1 2 MILES

0 1 2 KILOMETERS

0 1 2 MILES

0 1 2 KILOMETERS

0 1 2 MILES

0 1 2 KILOMETERS

76°17'

76°15'

76°17'

76°15'

42°29'

42°27'

42°29'

42°27'

76°17'

76°15'

42°29'

42°27'

76°17'

76°15'

42°29'

42°27'

76°17'

76°15'

42°29'

42°27'

76°17'

76°15'

42°29'

42°27'

75

120

70

210

100

130

30 50

100 200

80

120

300

30

EXPLANATION

Extent of the upper confined aquifer (layer 2) Hydraulic-conductivity zones—Number is horizontal

hydraulic value, in feet per day. Extent of the middle confined aquifer (layer 4)

Extent of the lower confined aquifer (layer 6)

Figure 31. Zones of horizontal hydraulic conductivity of the A, upper, B, middle, and C, lower confined aquifers used in the numerical 

simulation of groundwater flow in the stratified-drift aquifer system in Virgil Creek and Dryden Lake Valleys, Tompkins County, New York.
70 Geohydrology, Water Quality, and Simulation of Groundwater Flow, Town of Dryden, Tompkins County, New York KH4_140 KH4_130 KH2_80 RIV_420 KH2_90 RIV_410 RCH_300 RIV_400 KH6_180 RCH_310 KH6_190 KH6_200 RCH_330 RCH_320 KV1_10 KH6_280 RCH_360 KH6_210 KH6_250 KH6_230 KH6_220 KH6_290 RCH_350 KV5_160 RCH_340 KH2_100 KH4_150 KH6_170 RCH_370 KH2_110 KH6_240 KH6_260 KH6_270 KV3_120 KV1_20 KV1_30 KV1_40 KV1_60 

KV1_70 KV1_50 

COMPOSITE SENSITIVITIES, DIMENSIONLESS

0

200

400

600

800

1,000

MODEL PARAMETER

Figure 32. Composite sensitivity of groundwater-flow model output to changes in input parameters, stratified-drift aquifer system 

in the Virgil Creek, Dryden Lake, and Owego Creek Valleys, Tompkins and Cortland Counties, New York. KH, horizontal hydraulic 

conductivity; KV, vertical hydraulic conductivity; RCH, recharge; and RIV, river. Single-digit number following KH, KV, RCH, and RIV 

designates model layer number; underscore followed by a number designates subareas within a model layer.

groundwater-flow system reasonably well (fig. 33). Residual 

plots for heads show little bias in model error with the mean 

residual near zero (fig. 34).

A simulated head within the 10-ft confidence interval 

(±5 ft of the target) was considered a good agreement with 

the measured value (observation sites shown with green 

bars in fig. 33). A simulated head between the 10- and 20-ft 

confidence intervals (more than ±5 ft but less than ±10 ft) 

was considered a moderate agreement with the measured 

value (observation sites shown with yellow bars in fig. 33). 

A simulated head greater than the 20-ft confidence intervals 

(greater than ±10 ft of the target) would have been considered 

a poor agreement, and the bar would have been drawn in 

red. All 57 well observations (figs. 33 and 34; table 12) were 

less than the 20-ft confidence interval (±10 ft of the target). 

Of the 57 observation sites (green bars in fig. 33), 46 were 

entirely within 100 percent of the 10-ft confidence interval 

(plus or minus 5 ft of the target), and 11 were between 100 and 

200 percent of the confidence interval (±5 to 10 ft of the target, 

shown as yellow bars in fig. 33). The moderate agreement 

at the 11 sites that were between 100 and 200 percent of 

the confidence interval may be a result of inaccurately 

reported data, such as wrong well location (erroneous latitude 

and longitude coordinates or wrong reported address) or 

erroneous measured or reported water-level measurements. 

Alternatively, the moderate agreement may be a result of local 

geohydrologic heterogeneities or complexities that the model 

does not include because glacial stratigraphy is typically 

complex and the numerical groundwater-flow model is a 

simple representation of the groundwater-flow system of the 

study area.

Model calibration was considered satisfactory when 

(1) simulated heads were less than ±10 ft of the measured 

heads and (2) the root-mean-square error (a statistical 

measure of the magnitude of a varying quantity, which is 

especially useful when variations are positive and negative 

between differences of measured and simulated heads) for 

all observation wells was less than 4 ft (the root-mean-square 

error for the final model was 3.8 ft, table 12). However, the 

model-computed loss of discharge (0.89 ft3

/d) for Virgil Creek 

near the dam was less than the loss (1.19 ft3

/d) as measured 

on May 10, 2007. The root-mean-square error for water levels 

in the upper, middle, and lower confined aquifers (model 

layers 2, 4, and 6) were 4.3, 3.7, and 2.3, respectively. Most 
Simulation of Groundwater Flow 71

Figure 33. Groundwater-level residuals for simulated heads in the numerical groundwater-flow model of the stratified-drift 

aquifer system in Virgil Creek and Dryden Lake Valleys, Town of Dryden, Tompkins County, New York.

TM 166

TM 162

TM 160 TM 163 TM 159

TM 168

TM2094

TM2081 TM1676

TM 150

TM 153

TM 154

TM 162

TM2406 TM 146

TM 157

INSET MAP

0 0.5 1 MILE

0 0.5 1 KILOMETER

76°19' 76°18' 76°17' 76°16' 76°15' 76°14' 76°13' 42°31'

42°30'

42°29'

42°28'

42°27'

42°26'

42°25'

!.

!.

!.

!.

!.

!.

!.!.

!.

!.

!.

!.

!.

!. !.

!.

!.

!.!.!.!. !.

!.!.!.

!.!. !. !.

!.!.

!.

!.

!.

!.

!.

!.

!. !.

!.

!. !.

!.

!.

!.!.

!.

!.

!.

!.

!. !. !. !.

!.

!.

!.

!.

!.

!.

!. !.

!. !.

!.

!. !.

!.

!.

!.

!.

!.

!.

EXPLANATION

Grid frame

Model boundary

Observation well and well site name used to calibrate groundwater

flow model

TM 214

Calibration target

Error {

Observed minus interval

Observed value

Computed value

Observed plus interval

{

If the bar lies entirely within 100 percent of the target

(error of plus or minus 5 feet), the bar is drawn in green.

If the bar is between 100 and 200 percent of the target

(error is more than plus or minus 5 feet and less

than plus or minus 10 feet), the bar is drawn in

yellow. If the error were greater than 200 percent

(error is greater than plus or minus 10 ft)

the bar would be drawn in red.

TM 214

TM 199

TM 981

TM 204

TM1699

TM1050

TM2480

TM2256

TM1014 TM1000

TM 203

TM 198

TM 187

TM 184

TM1940

TM 192

TM1031

TM1032

TM 997

TM 998 TM1033

TM1887

TM2509

TM 135

TM1386

TM1012

TM2724

TM1011 TM 141

TM 145

TM 143

TM 993

TM1010

TM2571

C 44

C 75

C 88

C 609

TM 133

TM 195
72 Geohydrology, Water Quality, and Simulation of Groundwater Flow, Town of Dryden, Tompkins County, New York

Figure 34. Plots showing residuals for simulated heads in the numerical groundwater-flow model, showing 

relation between A, simulated and observed values and B, simulated values and residuals.

1,060 1,080 1,100 1,120 1,140 1,160 1,180 1,200 1,220

-5

0

5

10

15

-15

-10

1,060 1,080 1,100 1,120 1,140 1,160 1,180 1,200 1,220

1,040

1,060

1,080

1,100

1,120

1,140

1,160

1,180

1,200

1,220

OBSERVED HEADS, IN FEET

SIMULATED HEADS, IN FEET

SIMULATED HEADS, IN FEET

RESIDUALS, IN FEET

A

B
Simulation of Groundwater Flow 73

Table 12. Measured and simulated water levels in wells open to the stratified-drift aquifers in the Virgil 

Creek, Dryden Lake, and Owego Creek Valleys, Towns of Dryden and Harford, Tompkins and Cortland Counties, 

New York.

[NGVD29, National Geodetic Vertical Datum of 1929; TM, Tompkins County well; C, Cortland County well]

Well name Model layer

Water level altitude in feet above NGVD29 Residual 

(measured minus 

simulated) 

in feet above NGVD29

Measured Simulated

TM 133 4 1,175.0 1,171.3 3.7

TM 135 4 1,164.0 1,164.4 -0.4

TM 141 4 1,156.0 1,157.6 -1.6

TM 143 4 1,159.0 1,156.7 2.3

TM 145 4 1,150.0 1,154.8 -4.8

TM 146 2 1,160.0 1,154.0 6.0

TM 150 4 1,158.3 1,148.5 9.8

TM 152 4 1,148.7 1,149.1 -0.4

TM 153 4 1,152.3 1,151.4 0.9

TM 154 4 1,152.8 1,150.3 2.5

TM 157 2 1,150.7 1,143.9 6.8

TM 159 2 1,137.4 1,139.9 -2.5

TM 160 2 1,134.6 1,139.5 -4.9

TM 162 4 1,137.6 1,142.6 -5.0

TM 163 2 1,134.8 1,138.1 -3.3

TM 166 2 1,128.0 1,137.5 -9.5

TM 168 2 1,136.4 1,136.6 -0.2

TM 184 2 1,131.1 1,130.6 0.5

TM 187 4 1,121.3 1,126.7 -5.4

TM 192 2 1,120.6 1,119.0 1.6

TM 195 2 1,113.3 1,112.8 0.5

TM 198 4 1,110.8 1,113.3 -2.5

TM 199 6 1,111.7 1,111.0 0.7

TM 203 2 1,115.0 1,118.1 -3.1

TM 204 2 1,107.0 1,107.4 -0.4

TM 214 4 1,064.0 1,069.4 -5.4

TM 993 6 1,163.7 1,161.5 2.2

TM 981 4 1,104.3 1,106.3 -2.0

TM 997 6 1,189.4 1,192.5 -3.1

TM 998 4 1,195.8 1,194.9 0.9

TM1000 2 1,093.5 1,098.6 -5.1

TM1010 4 1,164.0 1,161.6 2.4

TM1011 2 1,164.0 1,157.3 6.7

TM1012 2 1,147.0 1,148.6 -1.6

TM1014 2 1,081.0 1,087.0 -6.0

TM1031 4 1,193.4 1,192.9 0.5

TM1032 2 1,195.7 1,197.6 -1.9
74 Geohydrology, Water Quality, and Simulation of Groundwater Flow, Town of Dryden, Tompkins County, New York

Table 12. Measured and simulated water levels in wells open to the stratified-drift aquifers in the Virgil Creek, 

Dryden Lake, and Owego Creek Valleys, Towns of Dryden and Harford, Tompkins and Cortland Counties, New 

York.—Continued

[C, Cortland County well; NGVD29, National Geodetic Vertical Datum of 1929; TM, Tompkins County well]

Well name Model layer

Water level altitude in feet above NGVD29 Residual 

(measured minus 

simulated) 

in feet above NGVD29

Measured Simulated

TM1033 2 1,191.3 1,194.9 -3.6

TM1050 1 1,083.0 1,080.5 2.5

TM1386 2 1,159.6 1,157.2 2.4

TM1676 2 1,150.4 1,147.9 2.5

TM1699 4 1,110.8 1,111.8 -1.0

TM1700 2 1,110.4 1,108.3 2.1

TM1887 4 1,174.5 1,172.9 1.6

TM1940 4 1,163.0 1,167.0 -4.0

TM2081 6 1,154.1 1,157.5 -3.4

TM2094 4 1,135.0 1,144.8 -9.8

TM2256 1 1,116.0 1,118.4 -2.4

TM2406 4 1,151.0 1,152.7 -1.7

TM2480 1 1,127.0 1,125.9 1.1

TM2509 4 1,167.0 1,167.3 -0.3

TM2571 2 1,161.0 1,169.2 -8.2

TM2724 6 1,155.9 1,154.8 1.1

C 44 4 1,205.3 1,206.9 -1.6

C 75 2 1,211.3 1,208.1 3.2

C 88 2 1,206.2 1,208.9 -2.7

C 609 4 1,200.0 1,201.1 -1.1

Median -0.4

Mean -0.8

Maximum 9.8

Minimum -9.8

Root mean square error 3.8

observation wells were in the upper and middle confined 

aquifers (25 and 26 observation wells, respectively). Only five 

observation wells were in the lower confined aquifer.

Water-level residuals (measured minus simulated 

water-level altitudes) for the stratified-drift aquifers are listed 

in table 12. Statistics were calculated for the water-level 

residuals, including median (-0.4 ft), mean (-0.8 ft), rootmean-square error (3.8 ft), maximum (9.8 ft), and minimum 

(-9.8 ft). Of the water-level residuals, 33 percent are less than 

zero, 24 percent are greater than zero, and 50 percent range 

from -2 to 2 ft.

Model Applications

The model was used as a tool to (1) better understand the 

groundwater-flow system in the stratified-drift aquifer system 

in Virgil Creek and Dryden Lake Valleys in Tompkins County, 

(2) estimate the areas contributing recharge to the production 

wells in the Village of Dryden in the northern part of the study 

area and to a hypothetical pumping well at the site of test well 

TM2724 near Keith Lane in the central part of the study area 

(location shown in fig. 8), and (3) compute a water budget.
Simulation of Groundwater Flow 75

Groundwater-Flow Directions

The numerical groundwater-flow model outputs cellby-cell water levels from which maps of the potentiometric 

surfaces of the aquifers can be made and used to show the 

direction of groundwater flow. The distribution of water 

levels and the generalized groundwater-flow directions 

(shown by arrows) in plan view for the three confined 

aquifers (model layers 2, 4, and 6) are shown on figures 

35A, B, and C, respectively. The distribution of water 

levels and the generalized groundwater-flow directions in a 

longitudinal hydrologic sectional view are shown on figure 36. 

The direction of groundwater flow is perpendicular to 

potentiometric contours.

North of the drainage divide separating the Dryden 

Lake Valley from the Owego Creek Valley, the horizontal 

component of groundwater flow in the upper and middle 

aquifers is generally to the northwest (figs. 35A, B). In the 

Virgil Creek Valley, the horizontal component of groundwater 

flow in the upper and middle confined aquifers initially flows 

westward from the eastern boundary of the model to the 

junction of Virgil Creek Valley with Dryden Lake Valley, 

where it then flows to the northwest (figs. 35A, B).

The horizontal and vertical components of groundwaterflow directions in the upper and middle confined aquifers 

are locally controlled by the distribution of surface-water 

bodies such as Dryden Lake, Virgil Creek downstream from 

the dam, and the stream that drains Dryden Lake (figs. 35A, 

B, and 36), which are groundwater-discharge zones. In the 

central part of the study area, most groundwater in the upper 

and middle confined aquifers discharges into these surfacewater bodies listed above. In the northern part of the study 

area, groundwater discharges to Virgil Creek, to the Village 

of Dryden production wells TM 981 (which taps the middle 

confined aquifer) and TM 202 and TM 204 (which tap the 

upper confined aquifer), and as underflow out through the 

northern boundary of the study area.

In the Dryden Lake Valley, the horizontal component 

of groundwater flow in the lower confined aquifer is 

predominantly to the northwest from the drainage divide 

in the southern part of the study area to the northern end 

of the model (figs. 35C and 36), where some groundwater 

discharges to the Village of Dryden production well TM1046 

at the South Street pumping station and the remainder 

discharges as underflow out through the northern boundary 

of the study area. In the Virgil Creek Valley, the horizontal 

component of groundwater flow in the lower confined aquifer 

is predominantly westward from the eastern boundary of the 

model to the junction of Virgil Creek Valley with Dryden Lake 

Valley, where it then flows to the northwest and leaves the 

study area as underflow out through the northern boundary of 

the study area (figs. 35C and 36).

The general vertical component of groundwater flow in 

the aquifer system is downward in the southern part (where 

large amounts of recharge occur at the Valley Heads Moraine), 

upward southwest of Dryden Lake in the central part (a major 

discharge area), and slightly upward in most of the northern 

part of the study area, except near the northern boundary, 

where flow is predominantly horizontal (fig. 36).

Areal Extent of the Zones of Groundwater 

Contribution to the Village of Dryden Municipal 

Production Wells

The areal extent of the zones of groundwater contribution 

to three Village of Dryden municipal production wells 

TM 202, TM 981, and TM1046 and to one hypothetical well 

at test well site TM2724 near Keith Lane were delineated 

through MODPATH, a particle-tracking program that 

computes three-dimensional flow paths using the output 

from the steady-state MODFLOW–2000 program. These 

delineations provide the Village of Dryden, the Town 

of Dryden, and Tompkins County with the approximate 

boundaries of the parts of the aquifer system that need to be 

managed to protect the water quality of this drinking-water 

resource. The MODPATH particle-tracking analyses were 

done with simulations that assumed average annual recharge 

conditions and average pumping conditions for 2005–7. 

During 2005–7, the average daily pumping rates for the 

Village of Dryden production wells TM1046, TM 981, and 

TM 202 were 125,300 gal/d (16,750 ft3

/d or 87 gal/min), 

93,900 gal/d (12,550 ft3

/d or 65 gal/min), and 30,600 gal/d 

(4,100 ft3

/d or 21 gal/min), respectively. Although the daily 

average pumping rate for TM 202 (which was pumped 

intermittently for 2005–7) was 30,600 gal/d (4,100 ft3

/d or 

21 gal/min), for the purposes of determining the areal extent 

of the zones of groundwater contribution under conditions that 

the well would be used more regularly, a simulated pumping 

rate of 72,000 gal/d (9,600 ft3

/d or 50 gal/min) was used 

(pump capacity is estimated to range from 50 to 60 gal/min). 

The simulated pumping rate for the hypothetical well was 

288,000 gal/d (38,500 ft3

/d or 200 gal/min). Backward 

tracking simulations were used to track imaginary particles 

starting from the pumping wells to where the recharge enters 

the aquifer system. The average traveltime for groundwater 

flow in the aquifers was estimated using a porosity of 0.3 

(30 percent) for sand and gravel, which is an assumed median 

aquifer porosity used for other stratified-drift model studies 

in upstate New York (Zarriello, 1993; Coon and others, 

1997; Miller, 1998). Porosity was held constant at 0.3 for the 

entire system; any variability in porosity, which likely occurs 

because of the complex glacial geology, will change the 

calculated traveltimes.

Plan views of the areal extent of the zones of 

groundwater contribution to Village of Dryden production 

wells TM 202 (Lake Road pumping station, finished in the 

upper confined aquifer) and TM 981 (Jay Street pumping 

station, finished in the middle confined aquifer) are shown 

on figure 37. The areal extent of the zones of groundwater 

contribution to production wells TM 202 and TM 981 are 

0.51 mi2

 and 0.94 mi2, respectively. The areal extent of the 
76 Geohydrology, Water Quality, and Simulation of Groundwater Flow, Town of Dryden, Tompkins County, New York

Figure 35. Distribution of hydraulic head computed by steady-state simulation for the stratified-drift aquifer system in 

Virgil Creek and Dryden Lake Valleys in Tompkins County and the headwaters of Owego Creek Valley in Cortland County, 

New York: A, upper confined aquifer (model layer 2), B, middle confined aquifer (model layer 4), and C, lower confined 

aquifer (model layer 6).

0 1 2 MILES

0 1 2 KILOMETERS

76°19' 76°18' 76°17' 76°16' 76°15' 76°14' 76°13' 42°31'

42°30'

42°29'

42°28'

42°27'

42°26'

42°25'

Base from TOPO! 2003 ©National Geographic, 

scale 1:24,000

EXPLANATION

Grid frame

Model boundary

Upper confined aquifer (model layer 2)

1,190 Potentiometric contour Contour interval 5 feet. Datum is National Geodetic Vertical Datum 

of 1929. Arrow indicates direction of groundwater flow.

Groundwater

divide

A

1,080

1,090

1,100

1,110

1,120

1,130

1,140

1,150

1,070

1,160

1,170

1,180

1,190

1,200

1,210

1,170

1,180

1,190

1,210

1,200

1,160
Simulation of Groundwater Flow 77

Figure 35. Distribution of hydraulic head computed by steady-state simulation for the stratified-drift aquifer system in 

Virgil Creek and Dryden Lake Valleys in Tompkins County and the headwaters of Owego Creek Valley in Cortland County, 

New York: A, upper confined aquifer (model layer 2), B, middle confined aquifer (model layer 4), and C, lower confined 

aquifer (model layer 6).—Continued

0 1 2 MILES

0 1 2 KILOMETERS

76°19' 76°18' 76°17' 76°16' 76°15' 76°14' 76°13' 42°31'

42°30'

42°29'

42°28'

42°27'

42°26'

42°25'

Base from TOPO! 2003 ©National Geographic, 

scale 1:24,000

EXPLANATION

Grid frame

Model boundary

Middle confined aquifer (model layer 4)

1,190 Potentiometric contour Contour interval 5 feet except noted differently near drainage 

divide. Datum is National Geodetic Vertical Datum of 1929. Arrow indicates direction of 

groundwater flow.

Groundwater

divide

B

1,080

1,090

1,100

1,110

1,120

1,130

1,140

1,150

1,070

1,160

1,170

1,180

1,190

1,200

1,170

1,180

1,190

1,205

1,207

1,207

1,200

1,160
78 Geohydrology, Water Quality, and Simulation of Groundwater Flow, Town of Dryden, Tompkins County, New York

Figure 35. Maps showing distribution of hydraulic head computed by steady-state simulation for the stratified-drift aquifer 

system in Virgil Creek and Dryden Lake Valleys in Tompkins County and the headwaters of Owego Creek Valley in Cortland 

County, New York. A, Upper confined aquifer (model layer 2). B, Middle confined aquifer (model layer 4). C, Lower confined 

aquifer (model layer 6).

0 1 2 MILES

0 1 2 KILOMETERS

76°19' 76°18' 76°17' 76°16' 76°15' 76°14' 76°13' 42°31'

42°30'

42°29'

42°28'

42°27'

42°26'

42°25'

Base from TOPO! 2003 ©National Geographic, 

scale 1:24,000

EXPLANATION

Grid frame

Model boundary

Lower confined aquifer (model layer 6)

1,190 Potentiometric contour Contour interval 5 feet. Datum is National Geodetic Vertical 

Datum of 1929. Arrow indicates direction of groundwater flow.

Groundwater

divide

Cone of depression for Village of Dryden 

production well TM1046 at the South Street 

pumping station

C

1,080

1,090

1,100

1,110

1,120

1,130

1,140

1,150

1,070

1,170

1,180

1,190

1,200

1,170

1,180

1,190

1,195

1,160
700800900

1,0001,1001,2001,3001,400

EXPLANATION

Lower confined aquifer Middle confined aquifer Upper confined aquifer Confining units

Bedrock (shale and siltstone)

Aquifer units Confining units

1,190 Potentiometric contour Contour interval 5 fe

Vertical Datum of 1929. Arrow indicates directio

FEET

Water

Water tableGroundwater divide

1,190 1,195 1,175 1,165 1,160

1,1701,155

1,140 1,1451,150 1,120 1,125 1,130 1,135 1,115

1,105

1,100

1,095

1,090 1,085 1,080 1,075 1,075

1,110

1,180 1,185

0 5,000 10,000 15,000 20,000 25

VERTICAL EXAGGERATION x16

Datum is North America Datum of 1929

A

Dryden

Lake

Valley Heads Moraine

Bog

Village of 

Dryden

FEET 

Figure 36. Groundwater flow in a longitudinal hydrologic cross-section A–A’ in the central part of the numerical groundwater model study area, T

Tompkins County, and Town of Harford, Cortland County, New York. Location of line of section shown on figure 8.
80 Geohydrology, Water Quality, and Simulation of Groundwater Flow, Town of Dryden, Tompkins County, New York

0 1 2 MILES

0 1 2 KILOMETERS

76°19' 76°18' 76°17' 76°16' 76°15' 76°14' 76°13' 42°31'

42°30'

42°29'

42°28'

42°27'

42°26'

42°25'

Base from TOPO! 2003 ©National Geographic, 

scale 1:24,000 EXPLANATION

Grid frame

Model boundary

Areal extent of the zone of groundwater 

contribution to the Village of Dryden 

production well TM 202 at Lake Street

Contour interval is the time, in years, for 

groundwater to travel to the well. 

10 Areal extent of the zone of groundwater 

contribution to the Village of Dryden 

production well TM 981 at Jay Street

Contour interval is the time, in years, for 

groundwater to travel to the well. 

10

10

TM 202

TM 981

20

30

10

20

30

40

Groundwater

divide

Daisy Hollow Brook

Figure 37. The estimated areal extent of the zones of groundwater contribution and time of travel to Village of Dryden production 

wells TM 202, which is finished in the upper confined aquifer (model layer 2), and TM 981, which is finished in the middle confined 

aquifer (model layer 4), in the Dryden Lake and Virgil Creek Valleys, Tompkins County, New York.
Simulation of Groundwater Flow 81

zone of groundwater contribution to well TM 202 extends 

2.2 mi southeast into the Virgil Creek Valley, while the areal 

extent of the zone of groundwater contribution to well TM 981 

extends 3.8 mi south in the Dryden Lake Valley. The furthest 

starting points for pathlines that simulate flow to well TM 202 

(Lake Road production well) are where Virgil Creek loses 

water to (recharges) the upper aquifer near the Virgil Creek 

Dam. Model results indicate that it takes approximately 30 

years for groundwater to flow from the eastern end of the 

model boundary (in the vicinity of the Virgil Creek Dam) 

to pumping well TM 202. The furthest starting points for 

pathlines that simulate flow to well TM 981 (Jay Street 

production well) are near the groundwater divide between 

the Susquehanna River Basin and Great Lakes Basin in 

the southern part of the Dryden Lake Valley. Model results 

indicate that it takes approximately 40 years for groundwater 

to flow from the southern end of the model boundary (near the 

groundwater divide between the Susquehanna River Basin and 

Great Lakes Basin) to pumping well TM 981.

The plan view of the areal extent of the zone of 

groundwater contribution to the Village of Dryden municipal 

production well TM1046 (South Street pumping station, 

finished in the lower confined aquifer) is shown on figure 38. 

The areal extent of the zone of groundwater contribution 

to this well is 1.4 mi2

 and extends 2.4 mi southeast into the 

Dryden Lake Valley and 0.5 mi east into the Virgil Creek 

Valley. In the Dryden Lake Valley, the furthest starting points 

for pathlines that simulate flow to production well TM1046 are 

at Daisy Hollow Brook and the groundwater divide between 

the Susquehanna River and Great Lakes Basins. In the Virgil 

Creek Valley, the furthest starting points for pathlines that 

simulate flow to production well TM1046 are at Virgil Creek 

at the Virgil Creek Dam area. The actual zone of groundwater 

contribution may extend beyond the southern model boundary; 

however, there were insufficient data on the flow conditions 

in the lower confined aquifer in the southern part of the study 

area to determine whether that is the case.

As development increases in the Town of Dryden, the 

need for more water will increase. One potential location 

for a production well is at test-well site TM2724 (on the Jim 

Schug trail near Keith Lane in the central part of the study 

area), where relatively thick aquifer units were encountered. 

A particle-tracking analysis was conducted for a hypothetical 

well finished in the lower confined aquifer at this site and for 

existing Village of Dryden municipal production well TM1046 

at the South Street pumping station, also finished in the lower 

confined aquifer. Plan views of the zones of groundwater 

contribution to Village of Dryden municipal production well 

TM1046 and to a hypothetical well at test-well site TM2724 

are shown on figure 39. The simulated pumping rate for 

the Village of Dryden municipal production well TM1046 

was 125,300 gal/d (87 gal/min), and the simulated pumping 

rate for the hypothetical well at test-well site TM2724 was 

288,000 gal/d (200 gal/min). The zones of groundwater 

contribution to municipal production well TM1046 and to 

a hypothetical well pumped at test-well site TM2724 are 

1.2 mi2

 and 0.86 mi2, respectively. The zone of groundwater 

contribution for municipal production well TM1046 extends 

4 mi down the eastern part of the Dryden Lake Valley and 

0.5 mi into Virgil Creek Valley, while the zone of groundwater 

contribution for the hypothetical well near Keith Lane extends 

3.4 mi down the western part of the Dryden Lake Valley. 

The results of the simulation with municipal production well 

TM1046 and the hypothetical well (both finished in the lower 

confined aquifer) indicate that the wells would interfere with 

one another. With the simulated hypothetical well pumping at 

a rate of 200 gal/min, the zone of groundwater contribution for 

municipal production well TM1046 shifted 500 ft to the east 

(figs. 38 and 39).

In the Dryden Lake Valley, the furthest starting points 

for pathlines that simulate flow to well TM1046 are at Daisy 

Hollow Brook and at the groundwater divide between the 

Susquehanna River and Great Lakes Basins (fig. 37). In the 

Virgil Creek Valley, the furthest starting points for pathlines 

that simulate flow to well TM1046 are at Virgil Creek at the 

Virgil Creek Dam area (fig. 39). In the Dryden Lake Valley, 

the furthest starting points for pathlines that simulate flow 

to the hypothetically pumped well (TM2724) are at the 

groundwater divide between the Susquehanna River and Great 

Lakes Basins (fig. 39). The actual areal extent of the zone of 

groundwater contribution may extend beyond the southern 

model boundary; however, there are not sufficient data on the 

flow conditions in the lower confined aquifer in the southern 

part of the study area to corroborate this hypothesis.

Water Budget

The water budget for simulated average annual, steadystate conditions with three simulated discharging wells 

representing the Village of Dryden municipal production 

wells is given in table 13. The model-computed water budget 

indicated that the sources of recharge to the confined aquifer 

system are precipitation that falls directly on the valley-fill 

sediments (40 percent of total recharge), stream leakage 

(35.5 percent), seepage from wetlands and ponds (12 percent), 

unchanneled runoff and groundwater inflow from the uplands 

(8.5 percent), and groundwater underflow into the eastern end 

of the modeled area (4 percent).

Most groundwater discharges to surface-water bodies 

(table 13), including (1) streams (33 percent of total 

discharge), (2) Dryden Lake (33 percent), and (3) wetlands 

and ponds (10 percent), but some groundwater discharges 

(4) as underflow out the northern end (11 percent) and 

southern end (4 percent) of the simulated area, (5) to simulated 

pumping wells (4.5 percent), and (6) to drains that represent 

seepage from the bluffs exposed in the gorge in the vicinity 

of the Virgil Creek Dam (4.5 percent). More water discharges 

as underflow out of the northern end of the study area than 

the southern end because the majority of recharge occurs in 

the Virgil Creek and Dryden Lake parts of the system and the 

simulated groundwater divide is close to the surface-water 

divide near the southern end of the study area.
82 Geohydrology, Water Quality, and Simulation of Groundwater Flow, Town of Dryden, Tompkins County, New York

0 1 2 MILES

0 1 2 KILOMETERS

76°19' 76°18' 76°17' 76°16' 76°15' 76°14' 76°13' 42°31'

42°30'

42°29'

42°28'

42°27'

42°26'

42°25'

Base from TOPO! 2003 ©National Geographic, 

scale 1:24,000

EXPLANATION

Grid frame

Model boundary (layers 1 through 5)

Areal extent of the zone of groundwater contribution to Village of Dryden 

production well TM 1046 at South StreetContour interval is the time, in 

years, for groundwater to travel to the well. 

10

Model boundary (layer 6)

TM1046

10

20

20

30

Groundwater

divide

Daisy Hollow Brook

Figure 38. The estimated areal extent of the zone of groundwater contribution and time of travel to Village of Dryden 

production well TM1046, which is finished in the lower confined aquifer (model layer 6), in the Dryden Lake and Virgil Creek 

Valleys, Tompkins County, New York.
Simulation of Groundwater Flow 83

Figure 39. Estimated areal extent of the zones of groundwater contribution and time of travel to Village of Dryden 

production well TM1046, which is finished in the lower confined aquifer (model layer 6), and to a hypothetical well at testwell site TM2724 near Keith Lane, also finished in the lower confined aquifer, in the Dryden Lake and Virgil Creek Valleys, 

Tompkins County, New York.

0 1 2 MILES

0 1 2 KILOMETERS

76°19' 76°18' 76°17' 76°16' 76°15' 76°14' 76°13' 42°31'

42°30'

42°29'

42°28'

42°27'

42°26'

42°25'

Base from TOPO! 2003 ©National Geographic, 

scale 1:24,000

EXPLANATION

Grid frame

Model boundary

(layers 1 through 5)

Areal extent of the zone of groundwater 

contribution to Village of Dryden production 

well TM1046 at South StreetContour interval 

is the time, in years, for groundwater to

travel to the wells. 

10 Areal extent of the zone of groundwater 

contribution to hypothetical well at test 

well site TM2724 near Keith Lane

Contour interval is the time, in years, for 

groundwater to travel to the wells. 

10

Model boundary (layer 6)

Groundwater

divide

10 20

TM1046

20

25

10

TM2724

20

Daisy Hollow Brook

Keith Lane
84 Geohydrology, Water Quality, and Simulation of Groundwater Flow, Town of Dryden, Tompkins County, New York

Table 13. Simulated water budget for the stratified-drift aquifer system in the Virgil Creek and Dryden Lake Valleys, 

Town of Dryden, Tompkins County, and in part of the Owego Creek Valley, Town of Harford, Cortland County, New York

[ft3/d, cubic feet per day; ft3/s, cubic feet per second

Inflow volume, 

in ft3

/d

Inflow volume, 

in ft3/s Percent

Recharge

Precipitation that falls directly over the valley-fill 

sediments

286,500 3.32 40

Upland sources:

Seepage losses from streams 253,200 2.93 35.5

Unchanneled runoff and underflow from uplands 60,300 0.69 8.5

Leakage from wetlands and ponds 87,900 1.02 12

Groundwater underflow entering Virgil Creek valley 27,500 0.32 4

Total 715,400 8.28 100

Discharge

Streams 233,000 2.70 33

Dryden Lake 237,600 2.75 33

Groundwater flow out ends of the modeled area:

Northern end 78,200 0.90 11

Southern end 31,900 0.37 4

Wetlands and ponds 70,500 0.82 10

Pumping wells 32,000 0.37 4.5

Drains along the Virgil Creek gorge near the dam 32,200 0.37 4.5

Total 715,400 8.28 100

Model Limitations

The numerical simulations of the stratified-drift aquifer 

system in Virgil Creek and Dryden Lake Valleys in Tompkins 

County and a small part of the headwaters in Owego Creek 

Valley in Cortland County offer a means of examining 

geohydrologic features that affect groundwater flow and 

the areal extent of the zones of groundwater contribution 

to several large pumping wells. However, to appraise the 

reliability of these simulations requires additional field data 

to refine the calibration and verify the model. Specifically, 

more wells would be needed to obtain head information in 

the aquifer for model calibration, to determine the thickness 

of the geohydrologic units, and to conduct additional aquifer 

tests that would be needed to estimate hydraulic properties. 

Although large amounts of recharge are believed to occur 

through windows in the confining units in the southern part of 

the study area (this assumption was made to match observed 

heads with modeled simulated heads), it has not been verified 

by field evidence. To confirm this hypothesis that windows 

in the confining units are present, a number of closely spaced 

wells would need to be drilled or large open pits would need to 

be excavated (similar to sand and gravel mines).

The use of the model as a quantitative predictive tool 

would be inappropriate without further data acquisition 

and calibration. The model at its present stage would be 

considered useful for estimating the general effects of changes 

in hydraulic values and boundary conditions on the size 

and shape of the areal extent of the zones of groundwater 

contribution. The accuracy of the flow lines generated by 

the particle-tracking program (MODPATH) depends largely 

on how realistically the flow model represents the system. 

The limitations inherent in modeling due to the uncertainty 

of parameter values and boundary conditions need to be 

considered if the model is to be used effectively.

Because the steady-state calibration period (2005–7) 

included years of above-average precipitation, the model 

was calibrated to pumping rates and some water levels that 

represent a wet cycle. The steady-state model results would 

change in drier years; for example, water levels would be 

lower and simulated areal extent of the zones of groundwater 

contribution would be larger during dry years.

For the three Village of Dryden production wells 

TM1046, TM 981, and TM 202, the age of groundwater 

was simulated by calculating the time of travel along the 
Summary 85

simulated flow paths back to the point of recharge and by 

CFC and 3

H-age dating methods. The ages determined from 

a CFC measurement at the Village of Dryden production well 

TM1046 at South Street (finished in the lower aquifer, layer 

6) range from more than 60 to 40 years (earlier than 1940s to 

early 1960s; table 9), and from a 3

H-age measurement it was 

about 35 years (late 1950s; table 9). The simulated time of 

travel calculated from the Village of Dryden production well 

TM1046 at South Street back to the point of recharge is a little 

more than 30 years (fig. 38), which is considered a good match 

with the 3

H age (about 35 years) but less of a good match with 

the CFC age (60 to 40 years).

The ages determined from CFC measurements at Village 

of Dryden production wells TM 981 at Jay Street (finished 

in the middle aquifer, layer 4 in model) and at Village of 

Dryden production well TM 202 at Lake Road (finished in 

the upper confined aquifer, layer 2 in model) range from more 

than 60 years to approximately 40 years (from mid-1940s 

to mid-1960s) and from 60 to approximately 40 years (early 

1940s to mid-1960s), respectively. The simulated times of 

travel that were computed for wells TM 981 and well TM 202 

(fig. 38) were approximately 40 and 30 years, respectively. 

However, the CFC ages for wells TM 981 and TM 202 may 

not be reliable because these ages differed substantially 

from 3

H-age measurements of 30 years or younger for both 

wells (early 1970s or younger; table 9) and because the CFC 

laboratory reported that these samples possibly were affected 

by mixing of waters of different ages. Therefore, because 

of the reasons stated above and because of the wide range 

in measured ages and inherent uncertainties of age-dating 

techniques, the CFC ages were not used to calibrate the 

numerical groundwater model.

Summary

In 2002, the U.S. Geological Survey, in cooperation 

with the Tompkins County Planning Department and the 

Town of Dryden, began a study of the stratified-drift aquifer 

system in the Virgil Creek and Dryden Lake Valleys in the 

Town of Dryden, Tompkins County, New York. Because this 

area is undergoing increasing development and the aquifers 

underlying the valleys are the most used in the county, this 

study was undertaken to characterize the geohydrology of the 

stratified-drift aquifer system in the Virgil Creek and Dryden 

Lake Valleys and provide the geohydrologic data needed 

by the Town of Dryden and Tompkins County to develop 

a strategy to manage and protect their water resources. In 

this study area, there are three extensive confined sand and 

gravel aquifers (upper, middle, and lower confined aquifers) 

that are tapped by most wells. The Dryden Lake Valley is 

a glaciated valley oriented parallel to the direction of ice 

movement. Erosion by ice extensively widened and deepened 

the valley, truncated bedrock hillsides, and formed a nearly 

straight, U-shaped bedrock trough. The maximum thickness 

of the valley fill in the central part of the Dryden Lake Valley 

is about 400 ft. The Virgil Creek Valley in the eastern part 

of the study area underwent less severe erosion by ice than 

the Dryden Lake Valley, hence it has a bedrock floor that is 

several hundred feet higher in altitude than that in the Dryden 

Lake Valley and contains less than 150 ft of sediments.

The sources and amounts of recharge were difficult 

to identify in most areas because the confined aquifers are 

overlain by confining units. However, near the Virgil Creek 

Dam, the upper confined aquifer crops out at land surface in 

the floodplain of a gorge eroded by Virgil Creek, and this is 

where the aquifer receives large amounts of recharge from 

precipitation that directly falls over the aquifer and from 

seepage losses from Virgil Creek. The results of streamflow 

measurements in Virgil Creek in the gorge indicated that 

the stream lost 1.2 cubic feet per second (ft3

/s; 0.78 million 

gallons per day) of water in the reach extending from 

1,200 feet (ft) upstream from the dam to 220 ft downstream 

from the dam.

Large amounts of recharge also replenish the aquifer 

system in the southern part of the study area at the Valley 

Heads Moraine, which consists of heterogeneous sediments 

that include coarse-grained outwash and kame sediments as 

well as zones that contain till with a fine-grained matrix. In 

this area, the till probably contains zones of coarse-grained 

material that form local windows of permeable sediment. 

These windows are where local large amounts of recharge 

(from precipitation that directly falls over the aquifer and from 

seepage losses from tributaries that flow over the valley floor) 

replenish the aquifers.

Most groundwater in the northern part of the study area 

discharges to the Village of Dryden municipal production 

wells, to the outlet to Dryden Lake, to Virgil Creek, and as 

groundwater underflow that exits the northern boundary of 

the study area. Most northward-flowing groundwater in the 

southern part of the study area discharges to Dryden Lake, 

to the inlet to Dryden Lake, to homeowner, nonmunicipal 

community wells (a mobile home park and several 

apartments), and to commercial wells. Most of this pumped 

water is eventually returned to the groundwater system via 

septic systems. In the southern part of the study area, most 

of the southward-flowing groundwater discharges to the 

headwaters of Owego Creek and to agricultural wells, and 

some exits as groundwater underflow out of the southern 

boundary of the study area.

The largest user of groundwater in the study area is the 

Village of Dryden. It is estimated that Village of Dryden 

production wells supply water to about 1,800 village residents, 

3,800 college students, 1,900 high school students, and several 

small businesses. Water use in the village has approximately 

tripled since the early 1970s, when withdrawals ranged 

between 18 and 30 million gallons per year (Mgal/yr), to 

2000 through 2008, when withdrawals ranged between 75 and 

85 Mgal/yr. The estimated groundwater use by homeowners, 

nonmunicipal communities, and small commercial facilities 

outside the Village of Dryden service area is estimated to be 
86 Geohydrology, Water Quality, and Simulation of Groundwater Flow, Town of Dryden, Tompkins County, New York

about 18.4 Mgal/yr, but much of this pumped water is returned 

to the groundwater system via septic systems.

For this investigation, an aquifer test was conducted at 

the Village of Dryden production well TM 981 (well depth 

72 ft and finished in the middle aquifer) at the Jay Street 

pumping station during June 19–21, 2007. The aquifer test 

consisted of pumping production well TM 981 at 104 gallons 

per minute (gal/min) over a 24-hour period. The drawdown in 

well TM 981 at the end of 24 hours of pumping was 19.2 ft. 

Results of the aquifer-test analysis for a partially penetrating 

well in a confined aquifer indicated that the transmissivity 

was 1,560 feet per day (ft/d), and the horizontal hydraulic 

conductivity was 87 ft/d, based on a saturated thickness of 

18 ft.

During 2003–5, surface-water samples were collected 

at eight sites, including Virgil Creek, Dryden Lake outlet, 

and several tributaries. During 2003–9, groundwater samples 

were collected from eight wells, including three municipal 

production wells, two test wells, and three domestic wells. 

Calcium dominates the cation composition and bicarbonate 

dominates the anion composition in most groundwater 

and surface-water samples, and none of the common 

inorganic constituents collected exceeded any Federal or 

State water-quality standards. Concentrations of calcium in 

groundwater samples ranged from 39.6 to 75.2 milligrams 

per liter (mg/L). Hardness ranged from hard to very hard. 

Sodium values ranged from 4.8 to 12.2 mg/L. Bicarbonate 

concentrations ranged from 138 to 196 mg/L, with a median 

of 152 mg/L, followed by sulfate and chloride, concentrations 

of which ranged from 15.8 to 49 mg/L and 5.71 to 

31.7 mg/L, respectively.

Results from a three-dimensional, finite-difference, 

groundwater-flow model were used to compute a water budget 

and to estimate the areal extent of the zones of groundwater 

contribution to the Village of Dryden municipal production 

wells. The model-computed water budget indicated that 

the sources of recharge to the confined aquifer system are 

precipitation that falls directly on the valley-fill sediments 

(40 percent of total recharge), stream leakage (35.5 percent), 

seepage from wetlands and ponds (12 percent), unchanneled 

runoff and groundwater inflow from the uplands (8.5 percent), 

and groundwater underflow into the eastern end of the model 

area (4 percent). Most groundwater discharges to surfacewater bodies, including Dryden Lake (33 percent), streams 

(33 percent), and wetlands and ponds (10 percent). In addition, 

some groundwater discharges as underflow out of the southern 

and northern ends of the model area (15 percent), to simulated 

pumping wells (4.5 percent), and to drains that represent 

seepage from the bluffs exposed in the gorge in the vicinity of 

the Virgil Creek Dam (4.5 percent).

The areal extent of the zones of groundwater contribution 

to three Village of Dryden municipal production wells 

TM 202, TM 981, and TM1046 and to one hypothetical well 

at test-well site TM2724 near Keith Lane were delineated 

through the software program MODPATH. These delineations 

provide the Village of Dryden, the Town of Dryden, and 

Tompkins County with the approximate boundaries of the 

parts of the aquifer system that need to be managed in order 

to protect the water quality of this drinking-water resource. 

The areal extent of the zones of groundwater contribution to 

Village of Dryden municipal production wells TM 202 (Lake 

Road pumping station, finished in the upper confined aquifer) 

and TM 981 (Jay Street pumping station, finished in the 

middle confined aquifer) are 0.5 square mile (mi2

) and 0.9 mi2, 

respectively. The areal extent of the zone of groundwater 

contribution to well TM 202 extends 2.2 miles (mi) southeast 

into the Virgil Creek Valley, whereas the areal extent of the 

zone of groundwater contribution to TM 981 extends 3.8 mi 

south in the Dryden Lake Valley. The areal extent of the zone 

of groundwater contribution to production well TM1046 

(South Street pump station) is 1.4 mi2

 and extends 2.4 mi into 

Dryden Lake Valley and 0.5 mi into Virgil Creek Valley. The 

areal extent of the zone of groundwater contribution of the 

hypothetical well at test-well site TM2724 near Keith Lane 

(which was identified as a potential future municipal-well 

site) is 0.86 mi2

 and extends 3.4 mi down the western part of 

the Dryden Lake Valley. The results of the simulation with 

municipal production well TM1046 and the hypothetical well 

pumping (both finished in the lower confined aquifer) indicate 

that there would be well interference (the lowering of the 

water level in one well due to pumping of another well). Also, 

the simulated pumping of the hypothetical well at a rate of 

200 gal/min altered the zone of groundwater contribution for 

municipal production well TM1046 by shifting its zone 500 ft 

to the east. 

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This page has been left blank intentionally.
Appendix 1 91

Appendix 1. Selected Wells in the Stratified-Drift Aquifer System in Virgil Creek 

and Dryden Lake Valleys, Tompkins County, and in Owego Creek Valley, Cortland 

County, New York
Table 1–1. Selected wells in the stratified-drift aquifer system in Virgil Creek and Dryden Lake Valleys, Tompkins County, and in Owego Creek Valley, [ft, feet; gal/min, gallons per minute; S&G, sand and gravel; --, no data; >, greater than; WL, water level] Well site name Date drilled Well depth, in ft Depth of casing, in ft Casing diameter, in inches Altitude land surface, in ft Aquifer type (aquifer layer) Water level below land surface, in ft Altitude water level, in ft Date water level measured Depth to bedrock, in ft Altitude top of bedrock, in ft Reporte

yield, in gal/min 

TM 125 11/6/1980 180 50 6 1,308 Shale -- -- -- 50 1,258 10 

TM 133 10/23/1961 52 52 6 1,160 S&G (middle) 25 1,135 10/23/1961 -- -- 24 TM 134 6/5/1973 171 45 6 1,215 Shale -- -- -- 45 1,170 5 TM 135 5/16/1905 82 82 6 1,240 Sand (middle) 76 1,164 5/16/1905 -- -- 5 TM 138 10/16/1974 82 82 6 1,175 S&G (lower) -- -- -- -- -- 15 TM 141 -- 79 79 6 1,206 S&G (middle) 50.6 1,155.4 10/25/1985 -- -- -- TM 143 9/22/1980 102 102 6 1,200 S&G (middle) 41 1,159 9/22/1980 -- -- 30 

TM 144 7/7/1963 267 31 6 1,230 Shale 135 1,095 7/7/1963 31 1,199 5 

TM 145 10/15/1961 98 98 6 1,200 S&G (middle) 50 1,150 10/15/1961 -- -- 24 

TM 146 1972 42 42 6 1,188 S&G (upper) 24 1,164 10/16/1984 -- -- -- 
Table 1–1. Selected wells in the stratified-drift aquifer system in Virgil Creek and Dryden Lake Valleys, Tompkins County, and in Owego Creek Valley, [ft, feet; gal/min, gallons per minute; S&G, sand and gravel; --, no data; >, greater than; WL, water level]

Well site 

name

Date 

drilled

Well 

depth, 

in ft

Depth 

of 

casing, 

in ft

Casing 

diameter, 

in inches

Altitude 

land 

surface, 

in ft

Aquifer type 

(aquifer layer)

Water 

level 

below 

land 

surface, 

in ft

Altitude 

water 

level, 

in ft

Date 

water 

level 

measured

Depth to 

bedrock, 

in ft

Altitude 

top of 

bedrock, 

in ft

Reported 

yield, 

in 

gal/min

TM 149 5/16/1978 157 157 6 1,145 S&G (lower) -- Flows -- -- -- 20 TM 150 9/6/1968 58 58 6 1,179.5 S&G (middle) 21.2 1,158.3 10/29/1985 -- -- 15 TM 152 10/28/1968 69 69 6 1,184.7 S&G (middle) 36 1,148.7 10/28/1968 -- -- 13 TM 153 4/29/1966 62 62 6 1,189.6 S&G (middle) 37.3 1,152.3 10/17/1985 -- -- 20 TM 154 3/29/1968 78 78 6 1,195.8 S&G (middle) 43 1,152.8 3/29/1968 -- -- 20 

TM 156 4/24/1975 62 40 6 1,200 Shale -- -- 4/24/1975 40 1,160 12 

TM 157 9/16/1967 65 65 6 1,203.7 S&G (upper) 53 1,150.7 10/25/1985 -- -- 20 

TM 159 10/17/1968 99 99 6 1,167 S&G (middle) 29.6 1,137.4 10/29/1985 -- -- 15 
Table 1–1. Selected wells in the stratified-drift aquifer system in Virgil Creek and Dryden Lake Valleys, Tompkins County, and in Owego Creek Valley, [ft, feet; gal/min, gallons per minute; S&G, sand and gravel; --, no data; >, greater than; WL, water level] Well site name Date drilled Well depth, in ft Depth of casing, in ft Casing diameter, in inches Altitude land surface, in ft Aquifer type (aquifer layer) Water level below land surface, in ft Altitude water level, in ft Date water level measured Depth to bedrock, in ft Altitude top of bedrock, in ft Reporte

yield, in gal/min 

TM 160 4/7/1971 43 43 6 1,151 S&G (upper) 16.4 1,134.6 10/29/1985 -- -- 25 TM 161 6/28/1971 57 57 6 1,245 S&G (upper) -- -- -- -- -- 20 TM 162 5/4/1970 113 113 6 1,162 S&G (middle) 24.4 1,137.6 10/30/1985 -- -- -- 

TM 163 5/1/1970 42 42 6 1,152.2 S&G (upper) 17.4 1,134.8 10/29/1985 -- -- 12 TM 164 5/7/1970 160 79 6 1,335 Shale 9 1,326 5/7/1970 79 1,256 6 

TM 166 8/17/1970 40 40 6 1,154 S&G (upper) 26 1,128 8/17/1970 -- -- 12 

TM 168 3/24/1971 31 31 6 1,150.4 S&G (upper) 14 1,136.4 3/24/1971 -- -- 30 

TM 169 8/21/1976 185 60 6 1,305 Shale 65 1,240 8/21/1976 60 1,245 5 

TM 170 8/29/1980 104 104 6 1,175 S&G (lower) Flows -- -- -- -- 20 

TM 171 4/12/1971 98 98 6 1,150 S&G (middle) -- -- -- -- -- 20 
Table 1–1. Selected wells in the stratified-drift aquifer system in Virgil Creek and Dryden Lake Valleys, Tompkins County, and in Owego Creek Valley, [ft, feet; gal/min, gallons per minute; S&G, sand and gravel; --, no data; >, greater than; WL, water level]

Well site 

name

Date 

drilled

Well 

depth, 

in ft

Depth 

of 

casing, 

in ft

Casing 

diameter, 

in inches

Altitude 

land 

surface, 

in ft

Aquifer type 

(aquifer layer)

Water 

level 

below 

land 

surface, 

in ft

Altitude 

water 

level, 

in ft

Date 

water 

level 

measured

Depth to 

bedrock, 

in ft

Altitude 

top of 

bedrock, 

in ft

Reporte

yield, 

in 

gal/min

TM 172 4/15/1972 97 97 6 1,137 S&G (middle) -- -- -- -- -- 30 

TM 174 3/31/1984 175 80 6 1,275 Shale 65 1,210 3/31/1971 75 1,200 -- 

TM 177 4/2/1975 62 62 6 1,180 S&G (upper) 5 1,175 4/2/1975 -- -- 20 TM 178 5/7/1970 52 52 6 1,255 Gravel 

(uplands)

25 1,230 5/7/1970 -- -- 15 

TM 179 4/14/1971 57 57 6 1,275 Gravel 

(uplands)

32 1,243 4/14/1971 -- -- 45 

TM 184 3/1/1967 50 50 6 1,164.1 S&G (upper) 33 1,131.1 3/1/1967 -- -- 15

TM 187 10/31/1980 92 92 6 1,139.3 S&G (middle) 18 1,121.3 10/31/1980 -- -- 25 

TM 189 12/15/1983 53 53 6 1,150 S&G (lower) 20 1,130 12/15/1983 -- -- 30 

TM 192 1965 97 97 6 1,157.6 S&G (middle) 37 1,120.6 8/1/1965 -- -- 24

TM 193 9/21/1978 96 96 6 1,127 S&G (middle) 14 1,113 9/21/1978 -- -- 15 

TM 195 8/14/1978 52 52 6 1,133.3 S&G (upper) 20 1,113.3 8/14/1978 -- -- 15 
Table 1–1. Selected wells in the stratified-drift aquifer system in Virgil Creek and Dryden Lake Valleys, Tompkins County, and in Owego Creek Valley, [ft, feet; gal/min, gallons per minute; S&G, sand and gravel; --, no data; >, greater than; WL, water level] Well site name Date drilled Well depth, in ft Depth of casing, in ft Casing diameter, in inches Altitude land surface, in ft Aquifer type (aquifer layer) Water level below land surface, in ft Altitude water level, in ft Date water level measured Depth to bedrock, in ft Altitude top of bedrock, in ft Reporte

yield, in gal/min 

TM 198 9/13/1978 103 103 6 1,126.8 S&G (middle) 16 1,110.8 9/13/1978 -- -- 30 

TM 199 3/7/1977 217 217 -- 1,105.7 S&G (lower) -6 1,111.7 6/4/1905 -- -- 50 

TM 202 1963 53 41 -- 1,100 S&G (upper) -- -- -- -- -- 100 

TM 203 1978 47 47 6 1,135 S&G (upper) 29 1,106 10/16/1984 -- -- -- 

TM 204 1964 51 39 -- 1,114.5 S&G (upper) 7.5 1,107 -- -- -- 115 
Table 1–1. Selected wells in the stratified-drift aquifer system in Virgil Creek and Dryden Lake Valleys, Tompkins County, and in Owego Creek Valley, [ft, feet; gal/min, gallons per minute; S&G, sand and gravel; --, no data; >, greater than; WL, water level]

Well site 

name

Date 

drilled

Well 

depth, 

in ft

Depth 

of 

casing, 

in ft

Casing 

diameter, 

in inches

Altitude 

land 

surface, 

in ft

Aquifer type 

(aquifer layer)

Water 

level 

below 

land 

surface, 

in ft

Altitude 

water 

level, 

in ft

Date 

water 

level 

measured

Depth to 

bedrock, 

in ft

Altitude 

top of 

bedrock, 

in ft

Reporte

yield, 

in 

gal/min

TM 207 1949 176 169 8 1,090 S&G (lower) Flows -- -- -- -- 85 TM 214 1/25/1972 67 67 -- 1,076 S&G (upper) 12 1,064 1/25/1972 -- -- 48 

TM 981 8/17/1998 72 62 8 1,111 S&G (middle) 6.7 1,104.3 6/13/2007 -- -- 104 
Table 1–1. Selected wells in the stratified-drift aquifer system in Virgil Creek and Dryden Lake Valleys, Tompkins County, and in Owego Creek Valley, [ft, feet; gal/min, gallons per minute; S&G, sand and gravel; --, no data; >, greater than; WL, water level] Well site name Date drilled Well depth, in ft Depth of casing, in ft Casing diameter, in inches Altitude land surface, in ft Aquifer type (aquifer layer) Water level below land surface, in ft Altitude water level, in ft Date water level measured Depth to bedrock, in ft Altitude top of bedrock, in ft Reporte

yield, in gal/min 

TM 993 12/9/2004 234 234 6 1,167 S&G (lower) 2.82 1,163.7 12/13/2004 -- -- 400 TM 997 11/17/2005 84 110 6 1,209 S&G (lower) 19.6 1,189.4 11/21/2005 109 1,100 5 TM 998 11/17/2005 37 37 6 1,209 S&G (upper) 13.2 1,195.8 11/21/2005 -- -- -- 

TM1000 7/12/1996 35 -- -- 1,100.5 S&G (upper) 7 1,094 7/9/1996 -- -- -- TM1005 6/21/1984 103 -- -- 1,230 S&G (middle) -- -- -- -- -- -- 

TM1006 6/12/1970 71 71 1,188 S&G (middle) 23 1,165 6/15/1984 -- -- -- TM1007 6/19/1984 88 -- -- 1,168 Till -- -- -- -- -- -- 
Table 1–1. Selected wells in the stratified-drift aquifer system in Virgil Creek and Dryden Lake Valleys, Tompkins County, and in Owego Creek Valley, [ft, feet; gal/min, gallons per minute; S&G, sand and gravel; --, no data; >, greater than; WL, water level]

Well site 

name

Date 

drilled

Well 

depth, 

in ft

Depth 

of 

casing, 

in ft

Casing 

diameter, 

in inches

Altitude 

land 

surface, 

in ft

Aquifer type 

(aquifer layer)

Water 

level 

below 

land 

surface, 

in ft

Altitude 

water 

level, 

in ft

Date 

water 

level 

measured

Depth to 

bedrock, 

in ft

Altitude 

top of 

bedrock, 

in ft

Reporte

yield, 

in 

gal/min

TM1010 4/15/1985 102 -- -- 1,162 S&G (middle) Flows 1,164 4/15/1985 -- -- -- TM1011 11/12/1987 92 -- -- 1,213 S&G (upper) 49 1,164 11/12/1987 -- -- -- TM1012 11/13/1987 73 -- -- 1,177 S&G (middle) 30 1,147 11/13/1987 -- -- -- TM1013 4/12/1985 106 -- -- 1,180 Till -- -- -- -- -- -- TM1014 6/22/1984 73 -- -- 1,092 S&G 

(unconfined)

11 1,081 6/22/1984 -- -- -- 
Table 1–1. Selected wells in the stratified-drift aquifer system in Virgil Creek and Dryden Lake Valleys, Tompkins County, and in Owego Creek Valley[ft, feet; gal/min, gallons per minute; S&G, sand and gravel; --, no data; >, greater than; WL, water level] Well site name Date drilled Well depth, in ft Depth of casing, in ft Casing diameter, in inches Altitude land surface, in ft Aquifer type (aquifer layer) Water level below land surface, in ft Altitude water level, in ft Date water level measured Depth to bedrock, in ft Altitude top of bedrock, in ft Reported yield, in gal/min 

TM1015 5/15/1978 95 95 6 1,120 S&G (middle) Flows (+3.8) 1,123.8 5/15/1978 -- -- -- 

TM1016 -- 170 170 6 1,095 S&G (lower) Flows -- -- -- -- 30 TM1030 7/14/1987 44 -- -- 1,234.5 S&G (upper) 24 1,210.5 7/14/1987 -- -- -- TM1031 7/14/1987 70 -- -- 1,200.2 S&G (middle) 6.8 1,193.4 7/14/1987 -- -- -- TM1032 7/27/1987 69 -- -- 1,202.9 S&G (upper) 7.2 1,195.7 7/27/1987 -- -- -- 

TM1033 7/21/1987 71 -- -- 1,198.5 S&G (upper) 7.2 1,191.3 7/21/1987 -- -- -- TM1034 7/28/1987 30 -- -- 1,242.5 S&G (upper) 22 1,220.5 7/28/1987 -- -- -- TM1046 1986 180 155 12 1,098 S&G (lower) +8.5 1,116.6 1986 -- -- 90 TM1050 9/9/2010 12 -- -- 1,087 S&G (unconfined) 4 1,083 9/9/2010 -- -- -- 
Table 1–1. Selected wells in the stratified-drift aquifer system in Virgil Creek and Dryden Lake Valleys, Tompkins County, and in Owego Creek Valley[ft, feet; gal/min, gallons per minute; S&G, sand and gravel; --, no data; >, greater than; WL, water level]

Well site 

name

Date 

drilled

Well 

depth, 

in ft

Depth 

of 

casing, 

in ft

Casing 

diameter, 

in inches

Altitude 

land 

surface, 

in ft

Aquifer type 

(aquifer layer)

Water 

level 

below 

land 

surface, 

in ft

Altitude 

water 

level, 

in ft

Date 

water 

level 

measured

Depth to 

bedrock, 

in ft

Altitude 

top of 

bedrock, 

in ft

Reported 

yield, 

in 

gal/min

TM1334 7/11/2001 115 43 6 1,224 Shale 40 1,184 7/11/2001 43 1,181 3 

TM1374 8/13/2001 57 57 6 1,180 S&G (middle) 18 1,162 8/13/2001 -- -- 15 TM1384 9/5/2001 78 78 6 1,130 S&G (outside 

study area)

10 1,120 9/5/2001 -- -- 20 

TM1386 9/7/2001 68 68 6 1,207.3 S&G (upper) 47.7 1,159.6 8/29/2005 -- -- 30 TM1432 1/10/2002 48 48 6 1,171 S&G 

(unconfined)

30 1,141 1/10/2002 -- -- 20 

TM1524 7/6/2002 129 20 6 1,205 Shale 26 1,179 7/6/2002 20 1,195 2 

TM1543 7/28/2002 110 23 6 1,268 Shale 17 1,251 7/28/2002 23 1,245 10 

TM1580 8/21/2002 140 58 6 1,530 Shale 58 1,472 8/21/2002 58 1,472 7 TM1629 10/30/2002 140 79 6 1,170 Shale 70 1,100 10/30/2002 79 1,091 4 

TM1676 5/8/2003 50 50 6 1,170.6 S&G (middle) 20.2 1,150.4 5/19/2009 -- -- 7 

TM1695 5/27/2003 396 300 6 1,115 Shale 7.3 1,107.7 5/27/2003 387 728 -- 
Table 1–1. Selected wells in the stratified-drift aquifer system in Virgil Creek and Dryden Lake Valleys, Tompkins County, and in Owego Creek Valley, [ft, feet; gal/min, gallons per minute; S&G, sand and gravel; --, no data; >, greater than; WL, water level] Well site name Date drilled Well depth, in ft Depth of casing, in ft Casing diameter, in inches Altitude land surface, in ft Aquifer type (aquifer layer) Water level below land surface, in ft Altitude water level, in ft Date water level measured Depth to bedrock, in ft Altitude top of bedrock, in ft Reporte

yield, in gal/min 

TM1699 5/28/2003 72 72 4 1,114.9 S&G (middle) 4.07 1,110.8 6/10/2003 -- -- -- 

TM1700 5/29/2003 41 41 6 1,115.2 S&G (lower) 4.82 1,110.4 6/10/2003 -- -- -- 

TM1725 7/31/2003 240 76 6 1,257 Shale 6 1,251 7/31/2003 76 1,181 5 

TM1735 8/8/2003 360 111 6 1,247 Shale 65 1,182 8/8/2003 111 1,136 2 

TM1779 9/24/2003 79 79 6 1,205 S&G (upper) -- -- -- -- -- 10 TM1855 5/21/2004 110 23 6 1,235 Shale 10 1,225 5/21/2004 6 

TM1887 7/13/2004 78 78 6 1,234.5 S&G (middle) 60 1,174.5 7/13/2004 -- -- 20 

TM1920 9/24/2004 90 90 6 1,105 S&G (outside study area) 50 1,055 9/24/2004 -- -- 12 

TM1940 11/2/2004 88 88 6 1,224.5 S&G (middle) 61.5 1,163 8/29/2005 -- -- 15 

TM1965 12/22/2004 49 49 6 1,120 S&G (upper) 30 1,090 12/22/2004 -- -- 10 

TM2001 4/25/2005 296 101 6 1,283.5 Shale 93 1,190.5 4/25/2005 96 1,188 4 

TM2020 5/14/2005 260 28 6 1,400 Shale 50 1,350 5/14/2005 28 1,372 4 

TM2063 8/1/2005 300 88 6 1,290 Shale 85 1,205 7/28/2005 88 1,202 2 
Table 1–1. Selected wells in the stratified-drift aquifer system in Virgil Creek and Dryden Lake Valleys, Tompkins County, and in Owego Creek Valley, [ft, feet; gal/min, gallons per minute; S&G, sand and gravel; --, no data; >, greater than; WL, water level]

Well site 

name

Date 

drilled

Well 

depth, 

in ft

Depth 

of 

casing, 

in ft

Casing 

diameter, 

in inches

Altitude 

land 

surface, 

in ft

Aquifer type 

(aquifer layer)

Water 

level 

below 

land 

surface, 

in ft

Altitude 

water 

level, 

in ft

Date 

water 

level 

measured

Depth to 

bedrock, 

in ft

Altitude 

top of 

bedrock, 

in ft

Reported 

yield, 

in 

gal/min

TM2070 9/8/2005 52 52 6 1,192 S&G (upper) 7 1,185 9/8/2005 -- -- 12 TM2081 8/17/2005 164 164 6 1,173.4 S&G (lower) 19.3 1,154.1 8/17/2005 -- -- 15 TM2094 9/19/2005 70 70 6 1,184 S&G (middle) 49 1,135 9/19/2005 -- -- 12 TM2103 7/21/2005 300 44 6 1,260 Shale -- -- -- 35 1,225 2 TM2118 10/28/2005 200 120 6 1,160 Clay -- -- -- -- -- -- 

TM2256 8/16/2006 30 30 6 1,122 S&G 

(unconfined)

8 1,114 8/16/2006 12 

TM2406 7/19/2007 69 69 6 1,186 S&G (middle) 35 1,151 7/19/2007 -- -- 20 

TM2444 9/10/2007 104 99 6 1,244 Shale 85 1,159 9/10/2007 99 1,145 10 TM2480 12/19/2007 60 60 6 1,169 S&G (upper) 42 1,127 12/19/2007 -- -- 6 

TM2509 4/30/2008 98 98 6 1,247 S&G (middle) 80 1,167 4/30/2008 -- -- 10 
Table 1–1. Selected wells in the stratified-drift aquifer system in Virgil Creek and Dryden Lake Valleys, Tompkins County, and in Owego Creek Valley, [ft, feet; gal/min, gallons per minute; S&G, sand and gravel; --, no data; >, greater than; WL, water level] Well site name Date drilled Well depth, in ft Depth of casing, in ft Casing diameter, in inches Altitude land surface, in ft Aquifer type (aquifer layer) Water level below land surface, in ft Altitude water level, in ft Date water level measured Depth to bedrock, in ft Altitude top of bedrock, in ft Reporte

yield, in gal/min 

TM2571 8/20/2008 60 60 6 1,206 S&G (upper) 45 1,161 8/20/2008 -- -- 60 TM2724S 12/16/2009 95 95 6 1,147.9 S&G (middle) Flows 1,154.9 12/16/2009 -- -- 100 TM2724D 12/16/2009 229 229 6 1,147.9 S&G (lower) Flows 1,155.9 12/16/2009 218 930 >100 C 44 12/1970 65 0 -- 1,216 Sand (upper) 10.8 1,205.3 4/11/1983 -- -- -- C 57 -- 204 204 6 1,231.9 Sand (lower) 46.8 1,185.2 8/7/1980 -- -- -- 

C 75 04/06/1974 38 35 -- 1,224 S&G (middle) 12.7 1,211.3 4/6/1974 -- -- -- 

C 88 11/1978 51 41 -- 1,238.4 S&G (upper) 32.2 1,206.2 11/16/1978 -- -- -- C 122 5/8/1974 40 38 -- 1,237.7 Sand (upper) 29.8 1,207.9 5/8/1974 -- -- -- C 123 5/8/1974 12 9 -- 1,237.7 S&G (unconfined) -- -- -- -- -- -- 

C 609 9/10/2002 68 68 6 1,245 S&G (middle) 45 1,200 9/10/2002 -- -- 10 
Prepared by the Pembroke Publishing Service Center

For additional information write to:

New York Water Science Center

U.S. Geological Survey

30 Brown Rd.

Ithaca, NY 14850

Information requests:

(518) 285-5602

or visit our Web site at:

http://ny.water.usgs.gov
Miller and Bugliosi—Geohydrology of the Stratified-Drift Aquifer System in the Town of Dryden, Tompkins County, New York—Scientific Investigations Report 2013–5070

Village

of 

Dryden

N

Dryden

Lake

Upper confined aquifer

Middle confined aquifer

Lower confined aquifer

W. Br. Owego C reek

Virgil Creek

Dryden

Lake

In let

Flow

Flow

Flow

Flow

Dryden

Lake

Outlet