Transmissivity Estimated From Brief Aquifer Tests of 

Domestic Wells and Compared With Bedrock Lithofacies and 

Position on Hillsides in the Appalachian Plateau of New York

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A. Well CN 511—Test 124

Ratio of residual drawdown (Yg) to

drawdown when pumping stopped (Yp) 

Time since pumping stopped (tg), in seconds

B. Well CN 337—Test 137 

Time since pumping stopped (tg), in seconds

C. Well D 388—Test 128 

Ratio of residual drawdown (Yg) to

drawdown when pumping stopped (Yp) 

Time since pumping stopped (tg), in seconds

D. Well BM 2580—Test 144 

Time since pumping stopped (tg), in seconds

EXPLANATION

Observed data

PICKINGmodel

EXPLANATION

Observed data

PICKINGmodel

EXPLANATION

Observed data

PICKINGmodel

EXPLANATION

Observed data

PICKINGmodel

Scientific Investigations Report 2020–5087

U.S. Department of the Interior

U.S. Geological Survey
Cover. Observed water-level recovery compared to PICKINGmodel type curves for four tests of domestic wells in the 

Appalachian Plateau of New York. Figure 3 of this report.
Transmissivity Estimated From Brief 

Aquifer Tests of Domestic Wells and 

Compared With Bedrock Lithofacies and 

Position on Hillsides in the Appalachian 

Plateau of New York

By Allan D. Randall and Andrew C. Mills

Scientific Investigations Report 2020–5087

U.S. Department of the Interior

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

DAVID BERNHARDT, Secretary

U.S. Geological Survey

James F. Reilly II, Director

U.S. Geological Survey, Reston, Virginia: 2020

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

Suggested citation:

Randall, A.D., and Mills, A.C., 2020, Transmissivity estimated from brief aquifer tests of domestic wells and compared 

with bedrock lithofacies and position on hillsides in the Appalachian Plateau of New York: U.S. Geological Survey 

Scientific Investigations Report 2020–5087, 21 p., https://doi.org/10.3133/sir20205087.

Associated data for this publication:

Randall, A.D., 2020, Field data from brief aquifer tests of domestic wells penetrating bedrock in the Appalachian 

Plateau of New York and best fits to theoretical curves of aquifer properties: U.S. Geological Survey data release, 

https://doi.org/10.5066/P9KLZD9M.

ISSN 2328-0328 (online)
iii

Contents

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

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

Lithofacies Distribution in the Devonian Bedrock of the Appalachian Plateau of New York ...........2

Selection of Wells for Testing......................................................................................................................2

Selection of a Procedure for Analyzing Brief Aquifer Tests of Domestic Wells .................................3

Analysis of 51 Brief Aquifer Tests ...............................................................................................................6

Longer Aquifer Tests of Five Wells ...........................................................................................................10

Comparison of PICKINGmodel to PPC-Recovery ...................................................................................13

Test Results Compared With Bedrock Lithofacies.................................................................................13

Test Results Compared With Position on Hillsides.................................................................................18

Summary........................................................................................................................................................19

References Cited..........................................................................................................................................20

Figures

1. Map of south-central New York showing distribution of three lithofacies within the

Middle and Upper Devonian bedrock of the Appalachian Plateau, and locations of

domestic wells that were tested during this investigation....................................................4

2. Graphs showing observed water-level recovery compared to PICKINGmodel type

curves for tests 111 and 149 of two domestic wells in the Appalachian Plateau of

New York ......................................................................................................................................10

3. Graphs showing observed water-level recovery compared to PICKINGmodel type

curves for tests 124, 128, 137, and 144 of domestic wells in the Appalachian Plateau

of New York..................................................................................................................................11

4. Graphs showing water-level recovery compared to PICKINGmodel type curves

for brief tests 132 and 133 of wells CN 612 and CN 547, respectively, in the

Appalachian Plateau of New York ...........................................................................................12

5. Boxplot showing distribution of transmissivity values for wells penetrating

bedrock in the Catskill-Cattaraugus and Chemung-Hamilton lithofacies in the 

Appalachian Plateau of New York ...........................................................................................18

Tables

1. Well properties and pumping test data for 52 domestic wells penetrating bedrock

in or adjacent to the Susquehanna River Basin in the Appalachian Plateau

of New York....................................................................................................................................7

2. Comparison of analyses of brief pumping tests by PICKINGmodel with analyses of

longer tests by Theis recovery method for four domestic wells penetrating bedrock

in the Appalachian Plateau of New York ................................................................................11

3. Comparison of recovery test results using two methods, for wells penetrating

bedrock in the Appalachian Plateau of New York ...............................................................14

4. Effect of including data beyond early fit to type curve on estimation of 

aquifer properties by PPC-Recovery for wells penetrating bedrock in the

AppalachianPlateau of New York ............................................................................................16

5. Transmissivity as a function of data fit to PICKINGmodel type curves for wells in

two bedrock lithofacies in the Appalachian Plateau of New York.....................................19

6. Variation in transmissivity of bedrock as a function of well position on hillsides in

the Appalachian Plateau of New York ....................................................................................19
iv

Conversion Factors

U.S. customary units to International System of Units

Multiply By To obtain

foot (ft) 0.3048 meter (m)

mile (mi) 1.609 kilometer (km)

square mile (mi2) 2.590 square kilometer (km2) 

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

gallon per minute per foot (gal/min/ft) 12.42 liter per minute per meter (L/min/m)

foot squared per day (ft2/d) 0.09290 meter squared per day (m2/d)

foot squared per second (ft2/s) 0.09290 meter squared per second (m2/s)

Datum

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

(NAVD 88).

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

except in figure 1, where the horizontal datum is the World Geodetic System 1984 datum.

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

Supplemental Information

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, feet 

squared per day (ft2/d), is used for convenience. The computer program used to calculate 

transmissivity generates results in feet squared per second, so this unit also appears in 

the report.

Abbreviation

USGS U.S. Geological Survey
Transmissivity Estimated From Brief Aquifer Tests of 

Domestic Wells and Compared With Bedrock Lithofacies 

and Position on Hillsides in the Appalachian Plateau of 

New York

By Allan D. Randall1 and Andrew C. Mills2

Abstract

Procedures for undertaking and analyzing recovery 

from aquifer tests of 13 to 132 seconds (described in reports 

cited herein) were applied to 51 domestic drilled wells that 

penetrated bedrock outside major valleys in the part of the 

Appalachian Plateau of New York drained by the Susquehanna 

River. Transmissivities calculated from these tests ranged over 

three orders of magnitude in both the Catskill-Cattaraugus 

lithofacies (shales, mudstones, siltstones, medium to coarse 

sandstones, pebbly sandstones) and the Chemung-Hamilton 

lithofacies (shales, mudstones, siltstones, fine to medium 

sandstones). Median transmissivity values were 0.000425 foot 

squared per second (36.7 feet squared per day) in the CatskillCattaraugus lithofacies and 0.00055 foot squared per second 

(47.5 feet squared per day) in the Chemung-Hamilton lithofacies. The distributions of transmissivity values within the 

two lithofacies were likewise similar. The range and median 

values of transmissivity were also nearly the same on lower 

and midlevel hillsides and were only slightly greater on a few 

upper hillsides. Transmissivities estimated from such easily 

arranged and analyzed tests may be appropriate for estimating 

groundwater flux under the small gradients that prevail under 

natural conditions, but not under larger drawdowns and steeper 

gradients near clusters of domestic wells. Four of the 51 wells 

tested were also pumped for 10 to 32 minutes; analysis by the 

Theis recovery method yielded transmissivities consistent with 

the brief tests for 2 wells, but 7 to 9 times smaller for 2 wells.

Transmissivity values estimated by the PICKINGmodel 

were not significantly different from values estimated by an 

automated application of the Picking method (PPC-Recovery) 

at a probability of 95 percent. Transmissivities calculated by 

either method from data for time intervals of 120 seconds or 

less may be of limited practical value because they apply only 

to a small volume of bedrock close to the pumped well.

1

U.S. Geological Survey.

2

Independent consultant, Lower Gwynedd, Pennsylvania.

Introduction

South-central and southwestern New York is an extensive 

upland, termed the Appalachian Plateau, that is composed 

of clastic sedimentary bedrock mantled by glacial till and is 

deeply incised by many valleys. Most of the region drains 

generally southward to the Delaware, Susquehanna, or Allegheny Rivers; the major valleys were widened and deepened 

by continental ice sheets and now contain a few hundred feet 

of sediments deposited by or in meltwater as the ice sheets 

retreated. The northern fringe of the Appalachian Plateau 

drains northward to Lake Ontario or the Mohawk River; major 

valleys here were even more deeply incised by ice and are now 

filled largely with till and fine-grained lacustrine sediments. 

Hydrogeological studies that compiled and analyzed records 

of many wells and test borings concluded that highly productive aquifers composed of sand and gravel are commonly but 

discontinuously present in the south-draining major valleys but 

are less abundant in the north-draining valleys (Randall, 2001).

The water-yielding potential of bedrock in the uplands 

between the major valleys in the Appalachian Plateau of 

New York has not been systematically appraised. Wetterhall 

(1959) reported that wells penetrating bedrock throughout 

Chemung County averaged 100 feet in depth and 8 gallons 

per minute in yield. Hollyday (1969) analyzed the yield 

distribution of 55 wells less than 400 feet deep that penetrated 

bedrock in the Susquehanna River Basin of New York. Most 

of these wells were in major valleys where bedrock is typically 

overlain by 100 feet or more of glacial sediments, including 

basal gravel aquifers in many places (MacNish and Randall, 

1982) that could help sustain the yield of wells tapping bedrock. Hollyday (1969) reported that 6 of the 55 wells yielded 

less than 10 gallons per minute, and that half of the remaining 

49 wells yielded 60 gallons per minute or more. No studies 

that attempted to calculate the variation in water-transmitting 

capacity of bedrock in this region, or the flux through bedrock into gravel aquifers in major valleys, were identified in 

the literature.
2 Transmissivity Estimated From Brief Aquifer Tests of Domestic Wells in the Appalachian Plateau of New York

The objectives of the study that led to this report were 

to (1) delineate to the extent feasible from the geological 

literature the variation in lithology, particularly grain size, of 

the bedrock in the Appalachian Plateau within or bordering 

the Susquehanna River Basin; (2) select or devise a procedure suitable for undertaking and analyzing brief, minimally 

invasive aquifer tests of domestic wells that tap bedrock; 

(3) test a representative sample of domestic wells that tap 

bedrock in this region, and analyze the test results to estimate 

transmissivity of bedrock at each well site; and (4) ascertain 

whether transmissivity varies as a function of bedrock grain 

size or topographic setting. Objective 2 was fully addressed by 

Klusman (1999, 2004) and Randall and Klusman (2004) and is 

summarized in this report. Objectives 1, 3, and 4 are addressed 

as fully as feasible in this report, which first describes the three 

predominant lithofacies in the upper few hundred feet of bedrock in the Appalachian Plateau of New York and depicts their 

distribution, then explains the criteria used to select the wells 

that were tested during this investigation. The report goes on 

to describe the selection and refinement of the procedure that 

was used to analyze the data from these brief aquifer tests, and 

to compile and interpret test results. Finally, the distribution of 

transmissivity values is compared to bedrock lithofacies and to 

the position of wells on hillsides. 

Lithofacies Distribution in the 

Devonian Bedrock of the Appalachian 

Plateau of New York

 The Middle and Upper Devonian bedrock of the Appalachian Plateau comprises a huge clastic wedge, referred to 

as the “Catskill Delta.” Sediment was transported northwestward across Pennsylvania and New York; both grain size and 

thickness of sediment decrease to the northwest (Sevon, 1985, 

p. 80–81). The principal lithofacies and corresponding depositional environments within the Middle and Upper Devonian 

bedrock of New York (Rickard, 1975) may be summarized as 

follows, from coarsest to finest:

1. Catskill-Cattaraugus lithofacies: Shales, mudstones, 

siltstones, medium to coarse quartz sandstones and subgraywackes, pebbly sandstones; piedmont and alluvial 

floodplain and peritidal environment.

2. Chemung-Hamilton lithofacies: Shales, mudstones, siltstones, fine to medium sandstones, coquinites; laminated 

and crossbedded, abundant marine shelly fauna; diverse 

subtidal shelf and nearshore environments.

3. Portage-Marcellus lithofacies: Shales, mudstones, siltstones, rare fine sandstones and argillaceous limestones; 

open shelf and anaerobic basin environments.

These lithofacies are referred to hereafter in this report 

as the Catskill, Chemung, and Portage lithofacies. They grade 

into one another, and their areal distribution varied with time 

of deposition. No map that delineates in detail the distribution 

of these lithofacies in New York was available to this study. 

However, Rickard (1975, plate 3) graphed their distribution 

in time (formation by formation) and in space (topographic 

quadrangle by quadrangle). Comparison of Rickard’s plate 3 

with the bedrock geologic map of New York (Fisher and 

others, 1970; Rickard and Fisher, 1970) allowed lithofacies 

distribution to be approximately delineated (fig. 1). Also, 

several reports (Pepper and de Witt, 1950, 1951; Pepper and 

others, 1956; Colton and de Witt, 1958; Sutton, 1960; Dugolinsky, 1967) describe variations in lithology west of 76 or 

77 degrees longitude within the Canadaway, West Falls, and 

Sonyea Groups, each of whose surficial extent is delineated 

on the Finger Lakes sheet (Rickard and Fisher, 1970) and 

Hudson-Mohawk sheet (Fisher and others 1970) of the “Geologic Map of New York.” Other reports (Grossman, 1944; 

Williams, 1951; de Witt and Colton, 1959, 1978) similarly 

describe the Genesee Group west of 75 degrees longitude. 

These reports do not include maps of lithofacies distribution 

but do include multiple correlated stratigraphic columns that 

represent exposures, from which the predominant lithofacies 

in particular localities can be inferred. The information in 

these reports allowed some lithofacies boundaries within the 

Upper Devonian (fig. 1) to be placed somewhat more precisely than could be inferred from Rickard’s correlation chart 

(1975, plate 3).

Selection of Wells for Testing

After the boundaries of the Catskill, Chemung, and Portage lithofacies were approximately delineated on the bedrock 

geologic map of New York, those boundaries were sketched 

onto topographic quadrangle maps encompassing the Susquehanna River Basin. Domestic wells suitable for testing were 

selected during field visits in the late 1990s according to the 

following criteria:

1. Sites near lithofacies boundaries were avoided as these 

boundaries were approximately delineated. Sites less 

than 3 miles south of such a boundary were also avoided 

because bedrock dips southward at an average slope of 

51 feet per mile in the central Susquehanna River Basin 

(Wright, 1973, plate 2), such that deep wells near the 

lithofacies boundary might penetrate into the underlying lithofacies. Substantial areas near Oneonta (north 

half of Oneonta and West Davenport 7.5-minute topographic quadrangles, east half of Otego quadrangle) 

were eliminated because the approximate lithofacies 

boundaries were closely spaced, with the Oneonta Formation (Catskill lithofacies) beneath hilltops and three 

formations apparently deemed Chemung lithofacies by 

Rickard (1975) on valley sides.
Selection of a Procedure for Analyzing Brief Aquifer Tests of Domestic Wells 3

2. Sites on ridge crests or near the top of steep slopes were 

avoided. Water levels in these areas fluctuated below the 

bottom of the casing more commonly than elsewhere and 

resulted in unsteady rates of recovery after pumping as 

the water level rose past open fractures or irregularities 

in well diameter. (Static water levels were not measured 

until the date of the test because prior measurement 

would have required a second extended period of nonuse by the homeowner. Therefore, 18 wells with water 

levels below the casing are included in the dataset.)

3. Sites were in uplands, where bedrock is mantled by 

till. Sites low on the sides of major valleys that contain 

outwash deposited by glacial meltwater were avoided 

because water-level recovery might be sustained by 

recharge from a nearby gravel aquifer atop bedrock. 

(The presence of postglacial alluvium beneath floodplains of nearby upland streams, which is typically only 

a few feet thick, was deemed acceptable.) 

4. Clusters of wells were avoided. Each well selected was 

at least 500 feet from any nearby wells whose intermittent pumping might cause water-level fluctuations in the 

tested well (unless the nearby residence was normally 

unoccupied during the day).

5. A record from the well driller listing well depth, casing 

length, tested yield, and other pertinent well properties, 

prepared at the time of well drilling, was available. (For 

several wells, this information was obtained during a 

subsequent visit to the driller.)

6. The well head was accessible, and the homeowner was 

willing to ensure that the pump would operate only 

once, when called for during the test, over a period as 

long as 6 hours. (Scheduling the test when no one was at 

home was most convenient for the homeowner and for 

the test.)

7. Sites tested were widely separated to ensure sampling 

many different segments of each lithofacies.

In Chenango County, most of the wells considered 

for testing were selected from well records published in 

U.S. Geological Survey (USGS) Water-Resources Investigations Report 91–4138 (McPherson, 1993). This report compiled records of many wells drilled in the late 1980s from 

well-completion reports submitted by drillers to the New 

York Department of Environmental Conservation. Most well 

locations (McPherson, 1993, plate 1) were determined by 

searching for the names of well owners on tax-parcel maps. 

Each potential well was visited during the present study before 

selection for testing. Several wells were determined to be 

mislocated by a few hundred feet to a few miles; the latitude, 

longitude, and elevation of each was corrected and entered in 

the USGS National Water Information System database (U.S. 

Geological Survey, 2019; https://waterdata.usgs.gov/nwis).

The original objectives of the present study included testing several wells that penetrated the Portage lithofacies in the 

northwestern part of the Susquehanna River Basin, but lack of 

time and resources prevented completion of this objective.

Selection of a Procedure for Analyzing 

Brief Aquifer Tests of Domestic Wells

Numerous reports have implemented the method of Theis 

(1935) in analyzing transient drawdown around a pumped 

well to calculate aquifer transmissivity and storage, assuming 

well radius is small enough that storage in the well bore could 

be neglected. Papadopulos and Cooper (1967) developed an 

alternative equation that represents drawdown in the pumped 

well while accounting for storage in the well bore and published a lookup table of values of a term needed to solve that 

equation. Picking (1994) presented a procedure for estimating 

aquifer transmissivity and storage by analyzing water-level 

recovery in a pumped well following a brief period of pumping at an unknown constant rate; the only data required are the 

well radius, the times when pumping started and stopped, a 

series of water-level measurements at known times thereafter, 

and a value selected from the lookup table of Papadopulos and 

Cooper (1967). All the data required by Picking’s procedure 

can be readily obtained from measurements during and following a brief episode of pumping of a domestic drilled well that 

taps bedrock.

In conjunction with the present investigation, Klusman (1999) wrote a computer program in Fortran, termed 

PICKINGmodel, that replicates Picking’s procedure, except 

that instead of interpolating between values in a lookup table, 

it directly calculates the values needed, thereby eliminating 

a significant source of error. Klusman (1999) applied that 

program to tests of 14 domestic wells that tap bedrock in 

the Susquehanna River Basin of New York. Klusman (2004) 

described the theoretical basis, application, and limitations 

of the program. Randall and Klusman (2004) explained the 

procedure used for data collection and the advantages of 

this minimally disruptive method of testing domestic wells. 

They also reported values of transmissivity and storage coefficient generated by analyzing 26 brief aquifer tests with 

PICKINGmodel and showed that similar values were obtained 

by the slug-test procedure of Cooper and others (1967) and 

the discrete-kernel procedure of Mishra and Chachadi (1985), 

after minor modifications to accommodate the data from the 

brief aquifer tests. As pointed out by Randall and Klusman 

(2004), permission from homeowners to undertake these minimally disruptive tests of domestic wells is relatively easy to 

obtain because no water is poured into the well (as commonly 

done in slug tests), and the stress on the well is no more than 

occurs many times each day due to normal operation of the 

homeowner’s pump. Also, the period of data collection, during 

which the homeowner can use only water already stored in the 

pressure tank or in buckets, can be as short as 2 hours (1 hour 
4 Transmissivity Estimated From Brief Aquifer Tests of Domestic Wells in the Appalachian Plateau of New York

LIVINGSTON

ALLEGANY

SCHUYLER

PENNSYLVANIA

LAKE ONTARIO

WAYNE

OSWEGO

ONONDAGA

SENECA

CAYUGA

YATES

ONTARIO

MONROE

LIVINGSTON

ALLEGANY

STEUBEN

SCHUYLER

CHEMUNG

TIOGA

CORTLAND

TOMPKINS

PENNSYLVANIA

77 ̊

43 ̊

42 ̊

43 ̊

42 ̊

77 ̊

0 5 10 20 MILES

0 5 10 20 KILOMETERS

EXPLANATION

Catskill-Cattaraugus lithofacies

Chemung-Hamilton lithofacies

Portage-Marcellus lithofacies

Mostly carbonate bedrock

Test-pumped well

Base from U.S. Geological Survey digital data, 2018

Web Mercator Auxiliary Sphere projection, World Geodetic System 1984 datum

Figure 1. Distribution of three lithofacies within the Middle and Upper Devonian bedrock of the Appalachian Plateau, and locations of 

domestic wells that were tested during this investigation.
Selection of a Procedure for Analyzing Brief Aquifer Tests of Domestic Wells 5

32

31

33

34

30

49

48

44

47 46

45

43

41

42

36

27

29

35

39

28 38

40

3

50

37

4

5 1

2

6 7

23

22

24

26 25

9 17

8 15

13 10

11

16 14 21

18 20

19

51

52

12

DELAWARE

FULTON

SULLIVAN

OSWEGO

ONEIDA

HERKIMER

MONTGOMERY

MADISON

OTSEGO

SCHOHARIE

CHENANGO

BROOME

CORTLAND

ONONDAGA

ULSTER

GREENE

PENNSYLVANIA NEW YORK

LEWIS

DELAWARE

FULTON

SULLIVAN

OSWEGO

Oneida Lake

ONEIDA

HERKIMER

MONTGOMERY

MADISON

OTSEGO

SCHOHARIE

CHENANGO

BROOME

CORTLAND

ONONDAGA

ULSTER

GREENE

PENNSYLVANIA NEW YORK

LEWIS

NY

PA

NJ

CT

VT

MA

76 ̊

43 ̊

42 ̊

75 ̊

76 ̊ 75 ̊

43 ̊

42 ̊

Base from U.S. Geological Survey digital data, 2018

Web Mercator Auxiliary Sphere projection, World Geodetic System 1984 datum

Figure 1. Distribution of three lithofacies within the Middle and Upper Devonian bedrock of the Appalachian Plateau, and locations of 

domestic wells that were tested during this investigation.—Continued
6 Transmissivity Estimated From Brief Aquifer Tests of Domestic Wells in the Appalachian Plateau of New York

to document the pre-test water-level trend and 1 hour to pump 

briefly and measure recovery). The current report presents tabulated values of aquifer transmissivity and storage coefficient 

estimated by applying PICKINGmodel to tests of 51 wells 

penetrating bedrock in the uplands of the Appalachian Plateau 

of New York and provides evaluations of the correlation of test 

results with bedrock lithofacies and position on hillsides.

To apply PICKINGmodel, the user estimates a trial value 

of transmissivity and several trial values of alpha (storage 

coefficient), from which the program calculates an array 

of type curves (one for each alpha value). Each type curve 

represents theoretical values of residual drawdown at multiple 

times since pumping stopped, each divided by drawdown at 

the moment pumping stopped (Yg/Yp), that would be expected 

from an aquifer with the postulated value of transmissivity and 

one of the postulated values of storage coefficient. The user 

must also plot a data curve in which each measured residual 

drawdown during recovery (Yg) is divided by drawdown at the 

moment pumping stopped (Yp) and plotted at the time since 

pumping stopped (tg). The type curves and the data curve 

must be plotted on the same graph by using a suitable graphics package; the user can then estimate new trial values of 

transmissivity and alpha to generate new type curves until a 

satisfactory match to the data curve is obtained.

One objective of the selected protocol for brief aquifer tests is to generate values of transmissivity that could be 

applied (individually or averaged among multiple wells) to 

estimate groundwater flux under natural hydraulic gradients. 

Also, if a well is tested, then the test could easily be replicated 

in the future to ascertain whether nearby construction or excavation has affected the yield of that well. These test results 

should not be extrapolated to estimate maximum sustained 

well yield because prolonged or higher-rate pumping would 

likely result in dewatering of shallow fractures and (or) more 

turbulent flow in fractures, which would alter the ratio of 

drawdown to pumping rate.

Analysis of 51 Brief Aquifer Tests

A total of 51 domestic wells penetrating bedrock in the 

Appalachian Plateau, all within or immediately adjacent to 

the Susquehanna River Basin, were test-pumped between 

1996 and 1999 for periods ranging from 13 to 132 seconds, 

following field procedures described by Randall and Klusman 

(2004). For each well tested, the observed record of waterlevel recovery after pump shutdown, expressed as residual 

drawdown divided by drawdown at the time of shutdown, was 

plotted against time in seconds since shutdown and compared 

with several type curves generated by PICKINGmodel (Klusman, 2004) that were based on trial values of transmissivity 

and storage coefficient. The trial values for the type curve 

that most closely matched the observed data are recorded in 

table 1. An additional well in table 1 (well CN 467, test 140) 

was test-pumped only for 10 minutes; that test was analyzed 

by methods described in Kruseman and deRidder (1990). Well 

dimensions are also summarized in table 1. Well locations are 

shown in figure 1. The input template for PICKINGmodel 

calls for pumping time (tp) and recovery time (tg) in seconds 

and trial transmissivity values in feet squared per second, 

which is appropriate for these brief tests. Table 1 reports bestfit transmissivity results in feet squared per second and in feet 

squared per day.

Drawdown and residual drawdown, based on measurements of water level every few seconds during most tests by 

a transducer and data logger and corrected for minor logger 

drift based on periodic taped measurements, are depicted in 

a companion USGS data release (Randall, 2020). Multiple 

spreadsheets and graphs that document which among several 

trial runs of PICKINGmodel best match the observed data are 

also included in the data release.

Table 1 indicates that in 23 of the 51 wells tested, the 

measured water-level recovery closely matched one of the 

trial type curves calculated by PICKINGmodel over the 

entire period of data collection, which was typically 3,500 to 

10,000 seconds (58 to 167 minutes), as illustrated for two tests 

in figure 2. In another 23 wells, however, the measured values 

of residual drawdown matched a type curve for only the initial 

15 to 1,000 seconds. Thereafter, the residual drawdown values 

decreased more gradually than the type curve and generally remained above the type curve to the end of the period 

of data collection, as illustrated for tests 124, 128, and 144 

in figure 3. This behavior might be attributed to the cone of 

depression having expanded into a zone of lesser transmissivity due to decreased aperture or pinch-out of fractures at 

greater distances from the well. One well (OG 382, test 119) 

exhibited behavior like both groups, with drawdown matching 

the type curve for the first 110 seconds then flattening beyond 

1,500 seconds. In four wells, by contrast, the late measured 

values of residual drawdown decreased more rapidly than the 

type curve fitted to the early values and generally reached zero 

residual drawdown 1,000 to 3,000 seconds after shutdown, 

as illustrated for test 137 in figure 3. This behavior could be 

attributed to the cone of depression having expanded into a 

zone of greater transmissivity at greater distances from the 

well. It should be possible to simulate, with an aquifer model 

or with image-well analysis, spatial and temporal variations 

in drawdown around a pumped well resulting from unknown 

variable extent and aperture of fractures, but water-level 

measurements at multiple sites would be needed for calibration. If some mathematical computation has been or could be 

developed to estimate change in effective transmissivity up 

to at least 10,000 seconds (167 minutes) from tests in which 

change in the rate of water-level recovery in the pumped well 

causes the data curve to flatten or steepen over time relative to 

PICKINGmodel type curves, that would enhance the applicability of test results.

As pointed out by Randall and Klusman (2004), these 

brief aquifer tests are easily arranged, undertaken, and analyzed by PICKINGmodel. If replicated at some later date, 

the tests could verify precisely whether any change in well 
Analysis of 51 Brief Aquifer Tests 

7

Table 1. Well properties and pumping test data for 52 domestic wells penetrating bedrock in or adjacent to the Susquehanna River Basin in the Appalachian Plateau of New York.[USGS, U.S. Geological Survey; no., number; ID, identifier; ft, foot; gal/min, gallon per minute; gal/min/ft, gallon per minute per foot; s, second; ft2/s, foot squared per second; ft2/d, foot squared per day]

Map 

no.

(fig. 

1)

Lithofacies USGS well no. National Water Information System site IDa Pump- ing test no.

From driller’s report Test data Analysis by PICKINGmodel Topographic 

position on 

hillside

Depth

(ft)

Casing 

length

(ft)

Yield

(gal/

min)

Specific 

capacityb

(gal/min/

ft)

Depth towater at Pumping 

duration

(s)

Transmissivity

(ft2/s)

Transmissivity

(ft2/d)

Data match to 

type curve

(s)d

Storage 

coefficient

Startc Shut- down

1 Catskill CN 139 422527075263601 125 132 16 18 1.65 52.8 56.7 45 0.00045 38.88 F 3–250 0.03 Middle2 Catskill CN 357 422703075310101 141 200 30 -- 0.078 e70.2 76 51 0.0002 17.28 P 1–200 0.0000001 Middle3 Catskill CN 474 422255075344201 117 149 21 7.5 0.0019 8.8 12.1 40 0.00036 31.104 C 5–8,000 0.001 --4 Catskill CN 511 422525075263301 124 100 22 4 0.92 44.2 46.1 25 0.0012 103.68 F 20–150 0.001 Upper5 Catskill CN 516 422539075283801 118 198 23 6 0.2 56.9 61.2 53 0.00032 27.648 C 5–3,500 0.0001 Middle6 Catskill CN 557 422751075300401 120 148 31 12+ 0.8 21.2 25.2 41 0.00045 38.88 C 3–10,000 0.1 Lower7 Catskill CN 577 422850075340801 121 143 115 7 0.097 74 83.2 99 0.00007 6.048 F 70–1,500 0.1 Middle8 Catskill D 349 422148075035301 102 170 30 20 1 68.9 71.7 84 0.0008 69.12 F 6–20 0.1 Middle9 Catskill D 350 421956075082401 101 165 72 10 0.24 21.7 29.2 84 0.00029 25.056 C 6–10,000 0.001 Upper

10 Catskill D 354 422415074564301 110b 90 60 10 1 30.9 33.2 36 0.0004 34.56 F 6–70 0.1 Middle

11 Catskill D 355 422202074585901 113 255 15 3.5 0.3 90 92.3 110 0.0003 25.92 F 15–55fg 0.1 Lower

12 Catskill D 357 422230074595401 105 298 53 8 0.8 41.3 44.7 66 0.00184 158.976 C 6–>2,000 0.00001 Lower13 Catskill D 358 422336074584301 103 173 50 180 3.1 12.9 13.9 66 0.005 432 F 5–40 0.1 Lower14 Catskill D 359 422127074293101 106 115 107 15 0.9 55.3 59.7 66 0.00172 148.608 F 6–200 0.0001 Middle15 Catskill D 366 422152075010801 107b 135 85 -- 0.9 8.7 12.5 95 0.00167 144.288 C 5–>2,400 0.0001 Lower16 Catskill D 367 421945075050401 109b 213 106 -- 1.3 45.7 49.2 68 0.0007 60.48 F 4–60 0.2 Middle17 Catskill D 375 422006075062601 112 165 125 10 0.32 43.6 51.2 132 0.00028 24.192 C 6–800,>3,000 0.01 Middle18 Catskill D 376 421905075015701 111 198 20 3 0.28 39.6 44.6 104 0.00008 6.912 C 1–10,000 0.0001 Middle19 Catskill D 385 421858075052801 122 225 180 9 0.0004 11.8 18.7 74 0.00084 72.576 F 2–950 0.000003 Middle20 Catskill D 388 421830075051001 128 185 10 8 1.2 67.8 71 90 0.0038 328.32 F 7–150 0.000001 Lower21 Catskill D 390 422059074582601 108 180 10 8 0.32 75.9 80.9 54 0.00067 57.888 C 6–>5,400 0.00001 Middle22 Catskill OG 378 422702075161801 116 175 95 5 0.22 9.5 11.7 30 0.0002 17.28 C 6–>7,800 0.001 Lower23 Catskill OG 379 422623075193101 127b 127 87 -- 3.5 8.6 9.9 57 0.0025 216 C 5–3,500 h0.5 Middle24 Catskill OG 380 422617075143901 302b 175 20 -- 0.33 26.3 30.5 58 0.0002 17.28 F 1–150 0.15 Middle25 Catskill OG 381 422528075123301 115 189 61 6 0.4 49.8 51.8 72 0.000205 17.712 C 6–>7,400 0.1 Lower26 Catskill OG 382 422446075151901 119 440 25 -- 0.032 51.4 55.3 i64

0.00001 0.864 F 1–110 0.1

Lower

0.00001 0.864 C 1,500–8,000 0.01

27 Chemung BM2578 421943075523501 145 100 15 5 0.47 12.2 17.2 42 0.0007 60.48 C 1–5,573 0.0001 Lower
8 Transmissivity Estimated From Brief Aquifer Tests of Domestic Wells in the Appalachian Plateau of New York Table 1.

Well properties and pumping test data for 52 domestic wells penetrating bedrock in or adjacent to the Susquehanna River Basin in the Appalachian Plateau of 

New York.—Continued[USGS, U.S. Geological Survey; no., number; ID, identifier; ft, foot; gal/min, gallon per minute; gal/min/ft, gallon per minute per foot; s, second; ft2/s, foot squared per second; ft2/d, foot squared per day]

Map 

no.

(fig. 

1)

Lithofacies USGS well no. National Water Information System site ID a Pump- ing test no.

From driller’s report Test data Analysis by PICKINGmodel Topographic 

position on 

hillside

Depth

(ft)

Casing 

length

(ft)

Yield

(gal/

min)

Specific 

capacityb

(gal/min/

ft)

Depth towater at Pumping 

duration

(s)

Transmissivity

(ft2/s)

Transmissivity

(ft2/d)

Data match to 

type curve

(s)d

Storage 

coefficient

Startc Shut- down

28 Chemung BM2579 421529075584101 146 93 29 20 6.7 7.8 10.5 55 0.002 172.8 F 1–25 0.1 Middle29 Chemung BM2580 422023075560501 144 125 40 -- 2 12.1 14.2 24 0.002 172.8 F 2–43 0.05 Middle30 Chemung C 466 423455075584101 147 197 19 5.5 0.265 35.4 39.9 60 0.0004 34.56 C 1–2,000 0.0001 Middle

31 Chemung C 484 423721076003901 150 104 47 6 0.73 17.2 22.5 99 0.0003 25.92 F 1–70 0.15 Middle

32 Chemung C 504 423822076022801 149 162 20 6 0.46 20.2 23.1 33 0.00035 30.24 C 2–8,000 0.01 Middle

33 Chemung C 536 423537075571601 151 248 55 30 0.64 94.6 97.3 41 0.0004 34.56 F 20–350 0.03 Lower

34 Chemung C 541 423817075540801 148 180 20 7 0.47 62.8 68.2 62 0.00013 11.232 C 1–10,000 0.25 Middle

35 Chemung CN 158 421911075424401 123 198 85 -- 1.16 69.3 74.1 105 0.0018 155.52 F 5–140 0.001 Upper

36 Chemung CN 23 422109075462901 153 190 12 6 0.11 34.8 42.1 107 0.000035 3.024 C 1–5,000 0.05 Lower

37 Chemung CN 331 421259075252101 129 185 93 5 0.4 83.2 91.1 60 0.00025 21.6 C 160–1,800f 0.01 Middle

38 Chemung CN 337 421522075343801 137 223 43 10 0.33 0 5.7 48 0.0005 43.2 P 1–600 0.0001 Lower

39 Chemung CN 352 421713075454101 143 117 24 5 0.13 14.2 19.2 118 0.0001 8.64 C 3–10,000 0.01 Upper

40 Chemung CN 399 421910075323401 126 247 31 3.5 0.23 43 47.8 58 0.00075 64.8 F 3–1,000 0.0000001 Upper

41 Chemung CN 467 422242075492601 140 188 59 10 0.045 17.1 22.9 125 0.00005 4.29 j 0.2 Middle

42 Chemung CN 525 422620075491501 134 173 49 5 0.15 46.9 53.9 80 0.000082 7.0848 F 1–900 0.01 Upper

43 Chemung CN 547 422720075501701 133 150 67 20 12 50.1 51.6 59 0.0335 2894.4 F 3–15 0.00001 Middle

44 Chemung CN 556 422749075454501 139 198 123 17.5 0.6 79.1 83.2 74 0.0006 51.84 F 1–200 0.01 Middle

45 Chemung CN 560 422759075505401 136 175 93 20 4.8 37.7 39.6 43 0.009 777.6 F 1–56 0.001 Upper

46 Chemung CN 578 422850075495001 135 200 170 15 2.5 9 11.7 59 0.008 691.2 C 2–3,300 0.000001 Middle

47 Chemung CN 606 423043075514701 142 116 44.3 10 0.45 41.4 41.9 k13 0.00127 109.728 C 3–1,000 0.002 Middle

48 Chemung CN 612 423108075445701 132 124 32 8 4.7 16.8 l17.8 80 0.008 691.2 C 1–600 0.1 Lower

49 Chemung CN 641 423328075433301 130 197 65 20 2.1 41 44.1 91 0.0034 293.76 C 3–3,500 0.01 Upper50 Chemung CN 69 422011075304701 131 160 68 10+ 0.7 37.2 42.3 71 0.0008 69.12 F 2.5–85 0.01 Middle51 Chemung OG 376 423029074562201 200 169 13 -- 0.28 0.2 2.8 70 0.000098 8.4672 P 10–1,500 0.1 Middle52 Chemung OG 377 423903075002201 100 112 10 -- 0.49 0 3.7 52 0.00043 37.152 P 5–400 0.01 Middle
Analysis of 51 Brief Aquifer Tests 

9

Table 1. Well properties and pumping test data for 52 domestic wells penetrating bedrock in or adjacent to the Susquehanna River Basin in the Appalachian Plateau of New York.—Continued[USGS, U.S. Geological Survey; no., number; ID, identifier; ft, foot; gal/min, gallon per minute; gal/min/ft, gallon per minute per foot; s, second; ft2/s, foot squared per second; ft2/d, foot squared per day]

Map 

no.

(fig. 

1)

Lithofacies USGS well no. National Water Information System site IDa Pump- ing test no.

From driller’s report Test data Analysis by PICKINGmodel Topographic 

position on 

hillside

Depth

(ft)

Casing 

length

(ft)

Yield

(gal/

min)

Specific 

capacityb

(gal/min/

ft)

Depth towater at Pumping 

duration

(s)

Transmissivity

(ft2/s)

Transmissivity

(ft2/d)

Data match to 

type curve

(s)d

Storage 

coefficient

Startc Shut- down

aSite ID consists of degrees, minutes, and seconds of latitude (6 digits) followed by degrees, minutes, and seconds of longitude (7 digits) followed by a serial number to distinguish multiple wells at 

the same location (01 for each well in this table).

bWater-level recovery between first 2 or 3 measurements after shutdown, extrapolated to rate in 1 minute, times 1.5 gallons per foot (in 6-inch casing), divided by distance from prepumping water 

level to midpoint of recovery interval.

cIn most tests, water level at start of pumping was rising slowly in response to earlier pumping in that well or wells nearby. Water levels are reported to the nearest 0.1 ft below land surface.dData match to type curve: C, complete match throughout measured range of recovery data; F, data curve flattens (slopes more gently than type curve) beyond range listed; P, data curve plunges 

(slopes much more steeply than type curve) beyond range listed.

eDepth to water measured July 31, 1998, immediately before test. On May 14, 1998, depth to water was 64.0 feet, and a small amount of water entered at about 53 feet.fNo data logger; water level measured manually with electric tape.gPoor match to PICKINGmodel type curve.hA storage coefficient of 0.5 is implausible for fractured bedrock, but other analytical methods also indicate large storage. Perhaps a sand lens atop bedrock sustains well yield?iDrawdown and recovery were briefly slowed by draining and refilling of a cavity between 53.8 and 54.1 depth. Pumping time was reduced by 20 seconds and segments of the recovery hydrograph 

before and after the cavity were merged to allow PICKINGmodel analysis.

jPICKINGmodel not used. Transmissivity and storage coefficient are from analysis of subsequent 10-minute test. Sediment 4 to 6 feet thick on bottom of well may have restricted yield from a

near-basal fracture.

kActual duration of pumping was 56 seconds. However, an apparent cavity at or slightly below the end of the casing slowed drawdown and recovery in this depth interval. Therefore, analysis was 

limited to the first 13 seconds of drawdown merged with the (much later) recovery within the casing.

lDepth to water was stable for 20 seconds immediately before shutdown due to smaller pumping rate as pressure tank filled.
10 Transmissivity Estimated From Brief Aquifer Tests of Domestic Wells in the Appalachian Plateau of New York

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

1 10 100 1,000 10,000 100,000

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

1 10 100 1,000 10,000

Ratio of residual drawdown (Yg) to

drawdown when pumping stopped (Yp) 

Time since pumping stopped (tg), in seconds

A. Well D 376—Test 111

Time since pumping stopped (tg), in seconds

Ratio of residual drawdown (Yg) to

drawdown when pumping stopped (Yp) 

B. Well C 504—Test 149 

EXPLANATION

Observed data

PICKINGmodel

EXPLANATION

Observed data

PICKINGmodel

Figure 2. Observed water-level recovery 

compared to PICKINGmodel type curves for 

tests 111 and 149 of two domestic wells in 

the Appalachian Plateau of New York. Test 

data fit type curves over the entire range of 

data collection.

performance has occurred. Transmissivity values computed 

from these tests may be suitable for estimating flow under 

natural gradients, including flow through bedrock to valley-fill 

aquifers. They would not be suitable for estimating maximum 

sustainable yield to individual wells or well clusters because 

about half the tests in this study documented reductions in 

recovery rate and transmissivity within a few minutes of the 

start of stress, presumably due to constrictions in water-yielding fractures several feet or more from the pumped well. Prolonged pumping stress from individual wells or overlapping 

stresses within well clusters could be expected to intersect 

more flow boundaries and to dewater some shallow fractures.

Longer Aquifer Tests of Five Wells

Four of the 51 wells that were pumped briefly for analysis 

by PICKINGmodel and one additional well (CH 467, test 140) 

were pumped for longer periods of 10 to 32 minutes, shortly 

before or after a brief test analyzed by PICKINGmodel. These 

longer tests were analyzed by the Theis recovery method 

(Kruseman and deRidder, 1990, p. 194–195). Transmissivities 

calculated from the longer tests, as well as the data timespans 

from which the transmissivities were calculated, are compared 

with results from PICKINGmodel in table 2.

Transmissivities calculated from the brief test and the 

longer test of well 143 are nearly identical, and for wells 

132 and 133 the brief tests and the longer tests seem reasonably consistent (albeit for different reasons). The measured 

water-level recovery from brief test 132 fits a PICKINGmodel type curve closely throughout the timespan of measured recovery, as shown in figure 4. (During brief test 132, 

the logger was set to record water levels only at 5-second 

intervals, but manual graphing of the data allowed estimation of the shutdown time to the nearest second, also values 

of tg and Yg/Yp at four times during the first 10 seconds of 
Longer Aquifer Tests of Five Wells 11

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

1 10 100 1,000 10,000 1 10 100 1,000 2,000

1 10 100 1,000 10,000

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

1 10 100 1,000 10,000

A. Well CN 511—Test 124

Ratio of residual drawdown (Yg) to

drawdown when pumping stopped (Yp) 

Time since pumping stopped (tg), in seconds

B. Well CN 337—Test 137 

Time since pumping stopped (tg), in seconds

C. Well D 388—Test 128 

Ratio of residual drawdown (Yg) to

drawdown when pumping stopped (Yp) 

Time since pumping stopped (tg), in seconds

D. Well BM 2580—Test 144 

Time since pumping stopped (tg), in seconds

EXPLANATION

Observed data

PICKINGmodel

EXPLANATION

Observed data

PICKINGmodel

EXPLANATION

Observed data

PICKINGmodel

EXPLANATION

Observed data

PICKINGmodel

Figure 3. Observed water-level recovery compared to PICKINGmodel type curves for tests 124, 128, 137, and 144 of domestic wells in 

the Appalachian Plateau of New York. Early test data fit type curves, but later test data slope more gently (tests 124, 128, and 144) or 

more steeply (test 137) than the type curve matched to the early data.

Table 2. Comparison of analyses of brief pumping tests by PICKINGmodel with analyses of longer tests by Theis recovery method for 

four domestic wells penetrating bedrock in the Appalachian Plateau of New York.

[ft2/s, foot squared per second; α, alpha; t/t’, time since start of pumping divided by time since start of recovery]

Parameters measured Test 132 Test 133 Test 135 Test 143

PICKINGmodel

Duration of pumping (seconds) 80 59 59 125

Duration of measured recovery (seconds) 2,480 3,780 3,800 10,000

Transmissivity (ft2

/s) 0.008 0.0335 0.008 0.0001

Storage coefficient (α) 0.1 0.00001 0.000001 0.01

Duration of data fit to type curve (seconds) 1–600 and more 3–18 (above curve 18 to 

1,000 and beyond)

2 to 3,300 3 to 10,000

Theis recovery method

Duration of pumping (seconds) 780 615 638 1,920

Duration of measured recovery (seconds) 7,970 18,285 3,760 12,045

Transmissivity (ft2

/s) 0.0061 0.0115 0.00093 0.00014

Timespan of straight-line portion of graph 

of residual drawdown versus t/t’ whose 

slope defines transmissivity (seconds)

30–7,970 20–165 (steeper curved 

line 165–1,125)

22–72 1,486–6,048
12 Transmissivity Estimated From Brief Aquifer Tests of Domestic Wells in the Appalachian Plateau of New York

1 10 100 1,000 10,000

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

1 10 100 1,000 10,000

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

Ratio of residual drawdown (Yg) to

drawdown when pumping stopped (Yp) 

Time since pumping stopped (tg), in seconds

A. Well CN 612—Test 132 

Ratio of residual drawdown (Yg) to

drawdown when pumping stopped (Yp) 

Time since pumping stopped (tg), in seconds

B. Well CN 547—Test 133 

EXPLANATION

Observed data

PICKINGmodel

EXPLANATION

Observed data

PICKINGmodel

Figure 4. Water-level recovery compared 

to PICKINGmodel type curves for brief tests 

132 and 133 of wells CN 612 and CN 547, 

respectively, in the Appalachian Plateau of 

New York. These wells were later test-pumped 

for 10 to 13 minutes.

recovery.) Transmissivity estimated by PICKINGmodel from 

brief test 132 differs by only a factor of 1.3 from transmissivity calculated from recovery measurements over the entire 

timespan of data collection during the longer test (table 2). 

PICKINGmodel accounts for storage of water in the well bore 

(Klusman, 2004), which may allow a more accurate interpretation of water-level rise measured in the pumped well during 

the first several seconds of recovery than allowed by the Theis 

recovery method, which assumes the diameter of the well to 

be infinitely small (Kruseman and deRidder, 1990, p. 56). 

The measured recovery from brief test 133 matched a 

PICKINGmodel type curve for only the first 18 seconds of 

recovery, then gradually departed from that type curve and 

remained above it throughout the remainder of the period of 

data collection (fig. 4). This behavior might be attributed to 

a transition to smaller transmissivity values a short distance 

outward from the well, caused by narrowing or pinch-out 

of one or more water-yielding fractures—and, indeed, the 

transmissivity estimated from data for 20 to 165 seconds of 

recovery in the longer test is about one-third of the transmissivity estimated by PICKINGmodel from data for 3–17 seconds of recovery.

Transmissivity estimated by PICKINGmodel from 

brief test 135 is 8.6 times the transmissivity estimated from 

a 10.6-minute test of the same well by the Theis recovery 

method (table 2). Brief tests of other wells were not supplemented by 10 to 30-minute tests, chiefly because nearly all 

the wells tested were used for domestic water supply; minimizing the interruption of service was often helpful in obtaining permission from the homeowner to test.
Test Results Compared With Bedrock Lithofacies 13

Comparison of PICKINGmodel to PPCRecovery

Mills (2010, 2019) devised a computer program, termed 

PPC-Recovery, which is also based on the procedure of Picking (1994) and can be used to analyze brief recovery tests. 

PPC-Recovery also requires the user to estimate several transmissivity and alpha values and to supply an array of tg and 

Yg/Yp data values; then the program automatically compares 

the type curve defined by each pair of transmissivity and alpha 

values with the array of data values and calculates the sum 

of the residuals squared for each such match. This method 

eliminates the subjective judgement inherent in visual curvematching and evaluates multiple alternative transmissivity 

and alpha options in less time than a single set of type curves 

can be calculated by PICKINGmodel, graphed, and evaluated. 

As part of this study, however, half of the brief aquifer tests 

conducted had already been evaluated (Randall and Klusman, 

2004) using PICKINGmodel. Also, visual displacement of 

the latter part of some type curves from PICKINGmodel data 

curves, discussed in the report section “Analysis of 51 Brief 

Aquifer Tests,” provided some insight into the potential factors 

influencing the drawdown curve that would not be obvious 

from the test results (sum of residuals squared) provided by 

PPC-Recovery. Accordingly, PICKINGmodel was used to 

analyze all aquifer tests in this report. 

Subsequently, as a verification check, field measurements 

for most tests were analyzed with the PPC-Recovery program; 

transmissivities calculated by PICKINGmodel and PPCRecovery for the tests in table 3 differed by 0 to 58 percent, 

with a median percentage difference of 8 percent and a mean 

of 14 percent. The pairs of transmissivities differed by less 

than 20 percent for 36 of the 50 tests. Application of the sign 

test (Gilbert, 1987) to all of these tests indicated that the transmissivity estimates by PICKINGmodel were not significantly 

different from estimates by PPC-Recovery at a probability of 

95 percent.

As explained in the section “Analysis of 51 Brief 

Aquifer Tests,” for 23 of the wells test-pumped for this study, 

PICKINGmodel generated type curves that fit the entire 

range of water-level recovery measurements, over as many 

as 10,000 seconds. These tests are identified by the letter C in 

the column “Range of data, in seconds, that fit a type curve” 

in table 3. Transmissivities calculated by PICKINGmodel 

and PPC-Recovery differed by less than 20 percent for 16 of 

these 23 tests. PICKINGmodel estimates were higher than 

PPC-Recovery estimates for 9 tests, lower for 12 tests, and 

equal for 2 tests. For another 23 tests, identified by the letter “F” in table 3, only the first 18 to 1,500 seconds of data 

fit a PICKINGmodel type curve; thereafter, the data curve 

sloped more gently than the type curve. For these 23 tests, 

PICKINGmodel estimates of transmissivity were higher than 

PPC-Recovery estimates for 10 tests, lower for 12 tests, and 

equal for 1 test; estimates differed by less than 20 percent for 

20 of these 23 tests. Application of the sign test (Gilbert, 1987) 

individually to the “C” and “F” subsets indicated that transmissivity estimates by PICKINGmodel were not significantly 

different from estimates by PPC-Recovery, at a probability of 

95 percent. For each of the tests in table 3, PPC-Recovery was 

constrained to analyze data from the same time interval that 

was analyzed by PICKINGmodel. The closely comparable 

results demonstrate that the two methods are mathematically 

consistent. However, transmissivities calculated by either 

method from data for time intervals of 120 seconds or less 

may be of limited practical value because they apply only to a 

small volume of bedrock close to the pumped well.

The data for 10 of the 23 “F” type tests, in which only the 

first 18 to 204 seconds fit a PICKINGmodel type curve, were 

further analyzed by applying the PPC-Recovery method to 

5 or 6 alternative time intervals during recovery. For each well 

tested, at least 10 data points were analyzed, and the data in 

table 4 are listed in order of increasing length of time analyzed. For each of these wells, as the analyzed time interval 

lengthened, the calculated transmissivity decreased somewhat, 

while the sum of residuals squared per data point increased, 

which indicates a progressively slightly poorer fit of the longer 

arrays of data to the best-fit PPC-Recovery type curves. These 

results are interpreted to indicate that (1) the cone of depression had expanded into a zone of lower transmissivity, in 

agreement with the interpretation of PICKINGmodel results 

in the text, and (2) as longer timespans encompassed a greater 

proportion of low-transmissivity bedrock, type curves computed from single transmissivity values became less able to 

fit both early and late recovery data, so the sums of squared 

residuals per data point increased.

Results demonstrate that when PPC-Recovery is applied 

to the same data interval as PICKINGmodel, the resulting estimates of transmissivity and storage are generally quite similar. 

This similarity indicates that the two procedures are computationally consistent and provides independent verification that 

PICKINGmodel is a mathematically sound adaptation of the 

procedure devised by Picking (1994).

Test Results Compared With Bedrock 

Lithofacies

Of the 52 wells tested, 26 penetrated bedrock assigned 

to the Catskill lithofacies, while 26 penetrated the Chemung 

lithofacies. The distributions of transmissivity values calculated for wells in these two lithofacies are shown in figure 5. 

Both distributions are similar, although 15 percent of the 

transmissivity values in the Chemung lithofacies exceeded 

0.005 foot squared per second, which was the largest value 

in the Catskill lithofacies. The median value among all wells 

tested was 0.000425 foot squared per second in the Catskill 

lithofacies and 0.00055 foot squared per second in the 

Chemung lithofacies. Application of the Wilcoxon rank sum 

test (U.S. Environmental Protection Agency, 2006) indicated 

that at a probability of 95 percent these two median values 
14 Transmissivity Estimated From Brief Aquifer Tests of Domestic Wells in the Appalachian Plateau of New York

Table 3. Comparison of recovery test results using two methods, for wells penetrating bedrock in the Appalachian Plateau of 

New York.

[ft, foot; ft2/s, foot squared per second]

U.S. 

Geological 

Survey well 

number

Pumping 

test number

Well 

depth 

(ft)

Analysis by PICKINGmodel Analysis by PPC-Recoveryb

Percent 

difference in 

transmissivity 

between two 

methods

Transmissivity

(ft2/s)

Storage

coefficient 

Range of data, 

in seconds, 

that fit a type 

curvea

Transmissivity

(ft2/s)

Storage

coefficient 

Sum of 

residuals 

squared per 

data point

OG 377 TEST 100 112 0.000430 0.01 P 5–400 0.00044 0.01 0.000030 2.3

D 350 TEST 101 165 0.000290 0.001 C 6–9,700 0.00027 0.002 0.000051 6.9

D 349 TEST 102 170 0.0008 0.1 F 6–24 0.00079 0.1 0.000080 1.3

D 358 TEST 103 173 0.005 0.1 F 6–42 0.0050 0.008 0.00015 0.0

D 357 TEST 105 298 0.00184 0.00001 C 6–>2,000c 0.0029 0.00000001 0.0000017 58

D 359 TEST 106 115 0.00172 0.0001 F 6–200 0.0016 0.0002 0.0000076 7.0

D 366 TEST 107b 135 0.00167 0.0001 C 5–>2,400c 0.0019 0.00002 0.000012 14

D 390 TEST 108 180 0.00067 0.00001 C 6–>5,400 0.00064 0.00002 0.0000024 4.5

D 367 TEST 109b 213 0.0007 0.2 F 4–64 0.00081 0.1 0.000047 16

D 354 TEST 110b 90 0.0004 0.1 F 6–70 0.00041 0.1 0.000058 2.5

D 376 TEST 111 198 0.00008 0.0001 C 1–10,000 0.000075 0.0001 0.000011 6.3

D 375 TEST 112 165 0.00028 0.01 C 6–800 0.00028 0.01 0.000013 0.0

OG 381 TEST 115 189 0.000205 0.1 C 6–>7,400c 0.000208 0.01 0.000015 1.5

OG 378 TEST 116 175 0.0002 0.001 C 6–>7,800c 0.00016 0.004 0.000013 20

CN 474 TEST 117 149 0.00036 0.001 C 5–8,000 0.00036 0.001 0.000007 0.0

CN 516 TEST 118 198 0.00032 0.0001 C 5–3,500 0.00036 0.00002 0.000011 13

OG 382 TEST 119 440 0.00001 0.1 F 4–110 0.000012 0.08 0.000023 20

CN 557 TEST 120 148 0.00045 0.1 C 3–9,400 0.00047 0.1 0.000047 4.4

CN 577 TEST 121 143 0.00007 0.1 F 70–1,500 0.000069 0.1 0.000045 1.4

D 385 TEST 122 225 0.00084 0.000003 F 2–950 0.0011 0.00000006 0.000046 31.0

CN 158 TEST 123 198 0.0018 0.001 F 5–140 0.0015 0.01 0.000073 17

CN 511 TEST 124 100 0.0012 0.001 F 20–150 0.0013 0.0008 0.000037 8.3

CN 139 TEST 125 132 0.00045 0.03 F 3–250 0.00041 0.06 0.000023 8.9

CN 399 TEST 126 247 0.00075 0.0000001 F 4–1,000 0.0010 0.0000000004 0.000079 33

OG 379 TEST 127b 127 0.0025 0.2 C 5–3,500 0.0027 0.1 0.00011 8.0

D 388 TEST 128 185 0.0038 0.000001 F 7–150 0.0041 0.0000004 0.000015 7.9

CN 331 TEST 129 185 0.00025 0.01 C 160–1,800 0.00027 0.008 0.0000080 8.0

CN 641 TEST 130 197 0.0034 0.01 C 3–3,500 0.0032 0.02 0.0000034 5.9

CN 69 TEST 131 160 0.0008 0.01 F 2.5–86 0.00069 0.02 0.0000034 14

CN 612 TEST 132 124 0.008 0.1 C 1–600 0.0082 0.1 0.000036 2.5

CN 547 TEST 133 150 0.0335 0.00001 F 3–18 0.032 0.00001 0.000040 4.5

CN 525 TEST 134 173 0.000082 0.01 F 3–900 0.000087 0.008 0.000021 6.1

CN 578 TEST 135 200 0.008 0.000001 C 2–3,300 0.010 0.00000001 0.000083 25

CN 560 TEST 136 175 0.009 0.001 F 1–70 0.0091 0.002 0.00029 1.1

CN 337 TEST 137 223 0.0005 0.0001 P 1–600 0.00076 0.0000002 0.000022 52

CN 556 TEST 139 198 0.0006 0.01 F 3–200 0.00053 0.02 0.0000088 12
Test Results Compared With Bedrock Lithofacies 15

Table 3. Comparison of recovery test results using two methods, for wells penetrating bedrock in the Appalachian Plateau of 

New York.—Continued

[ft, foot; ft2/s, foot squared per second]

U. S. 

Geological 

Survey well 

number

Pumping 

test number

Well 

depth 

(ft)

Analysis by PICKINGmodel Analysis by PPC-Recoveryb Percent 

difference in 

transmissivity 

between two 

methods

Transmissivity

(ft2/s)

Storage

coefficient 

Range of data, 

in seconds, 

that fit a type 

curvea

Transmissivity

(ft2/s)

Storage

coefficient 

Sum of 

residuals 

squared per 

data point

CN 357 TEST 141 200 0.0002 0.0000001 P 4–200d 0.00028 0.0000000001 0.0000035 40

CN 606 TEST 142 116 0.00127 0.002 C 3–1,000 0.0012 0.004 0.000078 5.5

CN 352 TEST 143 117 0.0001 0.01 C 3–9,800 0.000095 0.01 0.000013 5.0

BM2580 TEST 144 125 0.002 0.05 F 3–43 0.0017 0.1 0.000042 15

BM2578 TEST 145 100 0.0007 0.0001 C 1–5,600 0.00086 0.000008 0.000011 23

BM2579 TEST 146 93 0.002 0.1 F 1–25 0.0030 0.08 0.000046 50

C 466 TEST 147 197 0.0004 0.0001 C 1–2,000 0.00048 0.00002 0.000027 20

C 541 TEST 148 180 0.00013 0.25 C 1–10,000 0.00017 0.1 0.00034 31

C 504 TEST 149 162 0.00035 0.01 C 2–7,600 0.00034 0.01 0.000063 2.9

C 484 TEST 150 104 0.0003 0.15 F 1–70 0.00034 0.1 0.000020 13

C 536 TEST 151 248 0.0004 0.03 F 20–370 0.00037 0.06 0.000084 7.5

CN 23 TEST 153 190 0.000035 0.05 C 1–5,000 0.000027 0.1 0.000012 23

OG 376 TEST 200 169 0.000098 0.1 P 10–1,500 0.000093 0.1 0.000053 5.1

OG 380 TEST 302b 175 0.0002 0.15 F 3–150 0.00024 0.08 0.000032 20

Median: 8.0

Mean: 14

aC = Data curve fits type curve over entire data range. F = Data curve flattened (sloped more gently than type curve) beyond listed range.

P = Data curve plunged (sloped more steeply than type curve) beyond listed range.

bPPC-Recovery was applied to the same data range as was reported for the analysis by PICKINGmodel.

cRecovery nearly complete at end of range.

dData curve plunged during time period 220–2,000 seconds, then flattened during the time period 2,000–10,000 seconds.
16 Transmissivity Estimated From Brief Aquifer Tests of Domestic Wells in the Appalachian Plateau of New York

Table 4. Effect of including data beyond early fit to type curve on estimation of aquifer properties by PPC-Recovery for wells 

penetrating bedrock in the Appalachian Plateau of New York.

[ft2/s, foot squared per second, -- fit of data to PICKINGmodel type curves not optimal over this time range]

Pumping 

test number 

and analysis 

number

Analysis by PICKINGmodel Analysis by PPC-Recovery

Transmissivity

(ft2/s)

Storage

coefficient

Transmissivity

(ft2/s)

Storage

coefficient

Time range,

in seconds

Number of 

points

Sum of

residuals 

squared 

 Sum of residuals 

squared per

data point

TEST 102-1 0.0008 0.1 0.00079 0.1 6–24 4 0.000320 0.0000800

TEST 102-2 -- -- 0.00045 0.08 6–216 36 0.041350 0.0011486

TEST 102-5 -- -- 0.00045 0.1 6–228 38 0.045400 0.0011900

TEST 102-6 -- -- 0.00037 0.1 6–669a 77 0.167900 0.0022000

TEST 102-3 -- -- 0.00036 0.1 6–1,014 90 0.230750 0.0025639

TEST 102-4 -- -- 0.00034 0.1 6–6,204 179 0.439150 0.0024534

TEST 103-1 0.005 0.1 0.0050 0.008 6–42 7 0.001020 0.0001457

TEST 103-5 -- -- 0.0044 0.04 6–60 10 0.002000 0.0002000

TEST 103-6 -- -- 0.0041 0.08 6–84a 14 0.003300 0.0002300

TEST 103-2 -- -- 0.0041 0.1 6–102 17 0.005230 0.0003076

TEST 103-3 -- -- 0.0035 0.1 6–624 49 0.073400 0.0014980

TEST 103-4 -- -- 0.0033 0.1 6–1,674 66 0.100800 0.0015273

TEST 106-5 -- -- 0.0021 0.00001 6–96 16 0.000032 0.0000020

TEST 106-6 -- -- 0.0016 0.0002 6–198a 33 0.000240 0.0000100

TEST 106-1 0.00172 0.0001 0.0016 0.0002 6–204 34 0.000260 0.0000076

TEST 106-2 -- -- 0.0012 0.0040 6–702 89 0.007180 0.0000807

TEST 106-3 -- -- 0.0011 0.0100 6–1,812 141 0.016730 0.0001187

TEST 106-4 -- -- 0.0011 0.0100 6–6,552 202 0.024210 0.0001199

TEST 109b-1 0.0007 0.2 0.00081 0.1 4–64 11 0.000520 0.0000473

TEST 109b-5 -- -- 0.00063 0.1 4–202 34 0.039700 0.0011700

TEST 109b-2 -- -- 0.00057 0.1 4–310 47 0.091630 0.0019496

TEST 109b-6 -- -- 0.00050 0.1 4–610a 67 0.241800 0.0036090

TEST 109b-3 -- -- 0.00044 0.1 4–1,030 95 0.471320 0.0049613

TEST 109b-4 -- -- 0.00039 0.1 4–8,170 216 1.067270 0.0049411

TEST 110b-1 0.0004 0.1 0.00041 0.1 6–72 12 0.000690 0.0000575

TEST 110b-5 -- -- 0.00034 0.1 6–222 37 0.016100 0.0004300

TEST 110b-2 -- -- 0.00031 0.1 6–384 51 0.040670 0.0007975

TEST 110b-6 -- -- 0.00028 0.1 6–729a 74 0.126400 0.0017000

TEST 110b-3 -- -- 0.00027 0.1 6–1,014 92 0.203630 0.0022134

TEST 110b-4 -- -- 0.00026 0.1 6–1,514 175 0.469730 0.0026842

TEST 123-5 -- -- 0.00180 0.002 5–110 22 0.001200 0.0000530

TEST 123-1 0.0018 0.001 0.0015 0.01 5–140 26 0.002040 0.0000785

TEST 123-6 -- -- 0.0013 0.04 5–220a 44 0.006500 0.0001500

TEST 123-2 -- -- 0.0011 0.1 5–895 125 0.098450 0.0007876

TEST 123-3 -- -- 0.0010 0.1 5–2,940 241 0.294580 0.0012223

TEST 123-4 -- -- 0.0010 0.1 5–16,695 456 0.462730 0.0010148
Test Results Compared With Bedrock Lithofacies 17

Table 4. Effect of including data beyond early fit to type curve on estimation of aquifer properties by PPC-Recovery for wells 

penetrating bedrock in the Appalachian Plateau of New York.—Continued

[ft2/s, foot squared per second, -- fit of data to PICKINGmodel type curves not optimal over this time range]

Pumping 

test number 

and analysis 

number

Analysis by PICKINGmodel Analysis by PPC-Recovery

Transmissivity

(ft2/s)

Storage

coefficient

Transmissivity

(ft2/s)

Storage

coefficient

Time range, 

in seconds

Number of 

points

Sum of

residuals 

squared 

 Sum of residuals 

squared per

data point

TEST 133-1 0.0335 0.00001 0.033 0.00001 3–18 4 0.000160 0.0000400

TEST 133-5 -- -- 0.026 0.002 3–48b 10 0.003700 0.0003700

TEST 133-2 -- -- 0.026 0.02 3–103 21 0.013865 0.0006602

TEST 133-3 -- -- 0.032 0.1 3–303 57 0.051956 0.0009115

TEST 133-4 -- -- 0.032 0.1 3–1,003 111 0.101334 0.0009129

TEST 136-5 -- -- 0.012 0.00006 1–46b 10 0.001700 0.0001700

TEST 136-1 0.009 0.001 0.0099 0.0006 1–61 13 0.002720 0.0002092

TEST 136-2 -- -- 0.0094 0.04 1–506 76 0.053450 0.0007033

TEST 136-3 -- -- 0.0070 0.1 1–1,416 136 0.079950 0.0005879

TEST 136-4 -- -- 0.0075 0.1 1–7,726 307 0.111164 0.0003621

TEST 146-1 0.002 0.1 0.0030 0.08 1–25 25 0.001140 0.0000456

TEST 146-5 -- -- 0.0027 0.1 1–28 28 0.001600 0.0000570

TEST 146-2 -- -- 0.0025 0.1 1–101 49 0.020680 0.0004220

TEST 146-6 -- -- 0.0025 0.1 1–131a 55 0.032000 0.0005800

TEST 146-3 -- -- 0.0022 0.1 1–981 150 0.150846 0.0010056

TEST 146-4 -- -- 0.0022 0.1 1–6,581 314 0.207292 0.0006602

TEST 150-1 0.0003 0.15 0.00033 0.1 1–70 70 0.001380 0.0000197

TEST 150-2 -- -- 0.00027 0.1 1–200 187 0.060505 0.0003236

TEST 150-5 -- -- 0.00027 0.1 1–226 208 0.084900 0.0004100

TEST 150-3 -- -- 0.00023 0.1 1–804 381 0.415778 0.0010913

TEST 150-6 -- -- 0.00022 0.1 1–984a 415 0.509400 0.0012000

TEST 150-4 -- -- 0.00021 0.1 1–2,549 529 0.822220 0.0015543

a

Time in seconds to achieve 80-percent recovery.

b

Utilizing at least 10 points; exceeds 80-percent recovery.
18 Transmissivity Estimated From Brief Aquifer Tests of Domestic Wells in the Appalachian Plateau of New York

0.1

0.01

0.001

0.0001

0.00001

Lithofacies

Log(10) transmissivity, in feet squared per second

CatskillCattaraugusChemungHamilton

EXPLANATION

Maximum value

75th percentile

50th percentile

(median)

25th percentile

Minimum value—Excluding far out value

Mean

One or more data values

Far-out value—Value is below the 25th percentile

by more than 1.5 times the interquartile range

from the top to bottom of the box

26

26 26

Number of transmissivity values

Figure 5. Distribution of transmissivity values for wells 

penetrating bedrock in the Catskill-Cattaraugus and ChemungHamilton lithofacies in the Appalachian Plateau of New York.

are statistically the same. In each lithofacies, the median 

transmissivity calculated for wells where only early recovery 

data match a PICKINGmodel type curve exceeds the median 

transmissivity calculated for wells where the entire data array 

matches a type curve (table 5).

The values of transmissivity calculated from these tests 

are not based on measurements of dimensions or flow rates 

in water-yielding fractures; instead, these values describe a 

uniform granular porous aquifer that would transmit the same 

amount of water that is able to flow to the pumped wells 

through scattered bedrock fractures. Also, the static water level 

in a well that penetrates more than one water-yielding fracture 

will be a dynamic function of the heads and dimensions of 

these fractures and may differ from the water table prior to 

well construction.

Test Results Compared With Position 

on Hillsides

The Appalachian Plateau of New York is a region of 

substantial relief, where ridge crests are commonly about 

1,000 feet above the floors of major valleys. To evaluate the possibility that topographic position may correlate 

with well yield, the 52 tests analyzed during this investigation were classified into three categories by examination of 

topographic maps.

1. Upper hillsides, where elevation of the well site is much 

closer to the elevation of nearby ridge crests or hilltops 

than to the elevation of the nearest reach of the upland 

stream that drains several square miles including the 

site. (The selection of wells for testing excluded sites 

on ridge crests or at the top of steep valley walls, so that 

water-level fluctuations during the test would generally 

be within the casing, hence rates of recovery would not 

be subject to irregularities due to variations in borehole 

diameter or fractures in the bedrock within the interval 

of fluctuation.)

2. Lower hillsides, where the well site is much closer in 

elevation to the channel of a nearby tributary stream that 

drains several square miles than to nearby ridge crests. 

The deeper parts of these wells are generally below 

stream grade. Some nearby tributaries have alluvial 

floodplains 100 to 300 feet wide, but none of the wells 

tested bordered major valleys that contain outwash gravels deposited by glacial meltwater.

3. Middle hillsides, where elevation of the well site is 

intermediate between categories 1 and 2. Many of these 

middle hillsides are slightly incised by tiny headwater 

streams that lack alluvial floodplains recognizable on 

topographic or soils maps.
Summary 19

Table 5. Transmissivity as a function of data fit to PICKINGmodel type curves for wells in two bedrock lithofacies in the Appalachian 

Plateau of New York.

[ft2/s, foot squared per second; ft2/d, foot squared per day]

Lithofacies Category of data fit to PICKINGmodel type curve Number 

of wells

Median transmissivity 

value for type curves 

fitted to datasets

ft2

/s ft2/d

CatskillCattaraugus

A. All wells tested 26 0.000425 36.17

B. Wells where all residual drawdown data values match a type curve (fig. 2) 12 0.00034 29.4

C. Wells where only early residual drawdown values match a type curve, while later 

values decrease more slowly with time

13 0.0007 60.5

D. Wells where later data values decrease more rapidly than type curve 1 0.0002 17.3

ChemungHamilton

A. All wells tested 26 0.00055 47.5

B. Wells where all residual drawdown data values match a type curve (fig. 2) 11 0.0004 34.6

C. Wells where only early residual drawdown values match a type curve, while later 

values decrease more slowly with time

11 0.008 691.2

D. Wells where later data values decrease more rapidly than type curve 3 0.00043 37.2

The median transmissivity for each of these categories is 

presented in table 6, which indicates that water-transmitting 

fractures in bedrock are slightly more abundant, or more open, 

on the upper hillsides than on the middle and lower hillsides. 

However, results of individual well tests range far above and 

below the median values in each hillside category, and only 

eight test sites were classified as “upper hillsides.” A KruskalWallis statistical test (U.S. Environmental Protection Agency, 

2009) concluded that median transmissivity values for the 

three hillside categories are statistically indistinguishable at a 

probability of 95 percent. The median transmissivity value in 

each of the three topographic categories was compared with 

medians of the other two categories by a Wilcoxon rank sum 

test; the three medians were statistically equal at a probability of 95 percent. These tests demonstrate that hillside position does not have a strong influence on water-transmitting 

properties of the uppermost few hundred feet of bedrock in 

this region.

Table 6. Variation in transmissivity of bedrock as a function of 

well position on hillsides in the Appalachian Plateau of New York.

[ft2/s, foot squared per second; ft2/d, foot squared per day]

Position on 

hillside

Number

of

tests

Transmissivity

Range

(ft2

/s)

Median

(ft2/s)

Range

(ft2/d)

Median

(ft2/d)

Upper hillside 8 0.00008 

to 0.009

0.001 6.91

to 777

86.4

Middle hillside 29 0.00005 

to 0.0335

0.00055 4.32

to 2,894

47.5

Lower hillside 14 0.000035 

to 0.008

0.0006 3.02

to 691

51.8

Summary

Water-level recoveries from brief (13–132 seconds) 

episodes of pumping 51 domestic drilled wells that penetrate 

till-mantled bedrock in the Appalachian Plateau of southcentral New York were analyzed by applying a computer 

program termed PICKINGmodel. In each well tested, water 

levels were recorded frequently from the moment of pump 

shutdown until the water level approached the extrapolated 

pre-test trend. A data curve of time since shutdown in relation to residual drawdown (expressed as a ratio to drawdown 

at shutdown) was plotted and compared to a series of type 

curves, each calculated by PICKINGmodel from trial values 

of transmissivity and storage. For 23 of the tests, a type curve 

was selected that matched the observed data exactly or nearly 

so throughout the range of data collection. For 23 other tests, 

however, the selected type curve matched only the early data 

(as little as 15 to as much as 1,000 seconds), after which the 

observed residual drawdown decreased more slowly than 

the type curve, which indicates that the cone of depression 

may have expanded into a region of lesser transmissivity. In 

four tests, the late residual drawdown data values decreased 

more quickly than the type curve that matched the early 

data, which indicates that the cone of depression may have 

expanded into a region of greater transmissivity. Analysis of 

longer aquifer tests (10 to 32 minutes) of four of these wells 

by the Theis recovery method yielded transmissivity estimates 

0.12 to 1.4 times the transmissivity estimates from PICKINGmodel analysis of these wells.

Transmissivity estimated by PICKINGmodel from 

these tests ranged over three orders of magnitude in both the 

Catskill-Cattaraugus lithofacies (shales, mudstones, siltstones, 

medium to coarse sandstones, pebbly sandstones) and the 
20 Transmissivity Estimated From Brief Aquifer Tests of Domestic Wells in the Appalachian Plateau of New York

Chemung-Hamilton lithofacies (shales, mudstones, siltstones, 

fine to medium sandstones). Median transmissivities were 

similar (0.000425 foot squared per second in the Catskill lithofacies and 0.00055 foot squared per second in the Chemung 

lithofacies), as were the distributions of transmissivity values 

in each lithofacies. Hillside position (upper, middle, and lower 

hillsides) likewise had little influence on water-transmitting 

properties in this region. Results of these easily arranged and 

analyzed test procedures may be appropriate for calculating 

groundwater flux under the low gradients that prevail under 

natural conditions, but not under the larger drawdowns and 

steeper gradients that prevail near clusters of domestic wells. 

Transmissivities calculated by PICKINGmodel from data 

for time intervals of 120 seconds or less may be of limited 

practical value because they apply only to a small volume of 

bedrock close to the pumped well. If a computation could be 

developed to estimate an effective transmissivity from late 

recovery data that depart from PICKINGmodel type curves 

that fit the earlier data, brief aquifer tests such as described in 

this report might be more widely applicable. 

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For more information about this report, contact:

Director, New York Water Science Center

U.S. Geological Survey

425 Jordan Road

Troy, NY 12180–8349

dc_ny@usgs.gov

(518) 285–5602

or visit our website at

https://www.usgs.gov/centers/ny-water

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Pembroke Publishing Service Center
Randall and Mills—Transmissivity Estimated From Brief Aquifer Tests of Domestic Wells in the Appalachian Plateau of New York—SIR 2020–5087

ISSN 2328-0328 (online)

https://doi.org/10.3133/sir20205087