U.S. Department of the Interior

U.S. Geological Survey

ESTIMATING SPATIAL VARIABILITY OF RECHARGE IN 

SOUTHERN NEW JERSEY FROM UNSATURATED-ZONE 

MEASUREMENTS

Water-Resources Investigations Report 02-4288
ESTIMATING SPATIAL VARIABILITY OF RECHARGE IN 

SOUTHERN NEW JERSEY FROM UNSATURATED-ZONE 

MEASUREMENTS

By Arthur L. Baehr, Leon J. Kauffman, Kimberlie Perkins, and Bernard T. Nolan

U.S. GEOLOGICAL SURVEY

Water-Resources Investigations Report 02-4288

West Trenton, New Jersey

2003
U.S. DEPARTMENT OF THE INTERIOR

GALE A. NORTON, Secretary

U.S. GEOLOGICAL SURVEY

Charles G. Groat, Director

The use of brand, trade, or firm names in this report is for identification purposes only, 

and does not constitute endorsement by the U.S. Government.

For additional information Copies of this report can be

write to: purchased from:

District Chief

U.S. Geological Survey U.S. Geological Survey

Mountain View Office Park Branch of Information Services

810 Bear Tavern Road Box 25286

West Trenton, NJ 08628 Denver, CO 80225-0286
iii

CONTENTS

Page

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

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

Study area ...................................................................................................................................................... 3

Study methods ............................................................................................................................................... 3

Unsaturated-zone sampling .............................................................................................................. 3

Flow calculation ............................................................................................................................... 8

Recharge estimates ...................................................................................................................................... 22

Uncertainty of calculations............................................................................................................. 22

Flow regime.................................................................................................................................... 25

Mapping spatial trends.................................................................................................................... 25

Summary and conclusions ........................................................................................................................... 30

References cited........................................................................................................................................... 30

ILLUSTRATIONS

Figure 1. The hydrologic cycle in a watershed with various land uses..................................................... 2

2. Location of Glassboro study area, southern New Jersey. .......................................................... 2

3. Location of unsaturated-zone sampling sites, Glassboro study area. ........................................ 4

4. Distribution of (a) all recharge estimates and (b) recharge estimates between 0 and

110 centimeters per year for unsaturated-zone sampling sites, Glassboro study area. ..... 24

5. Relation of flow estimates based on measured hydraulic parameters to flow based on 

estimated hydraulic parameters for six selected unsaturated-zone sampling sites, 

Glassboro study area.......................................................................................................... 26

6. Relation of flow (R) to conductivity (K) for (a) all sands and (b) sands in which flow was 

less than 100 centimeters per year..................................................................................... 27

7. Relation of flow (R) to conductivity (K) for sandy loams....................................................... 28

8. Probability of recharge exceeding 29.2 centimeters per year in the Glassboro study area...... 29

TABLES

Table 1. Unsaturated-zone sampling sites, southern New Jersey ............................................................ 5

2. Moisture content at unsaturated-zone sampling sites ................................................................ 6

3. Unsaturated-zone characteristics at sampling sites, southern New Jersey................................. 9

4. Particle-size distribution in samples from unsaturated-zone sampling sites, southern New 

Jersey ................................................................................................................................. 24

5. Input to and pedotransfer function parameters from the Rosetta program for unsaturatedzone sampling sites, southern New Jersey ........................................................................ 18

6. Summary of flow calculations for unsaturated-zone sampling sites, southern

New Jersey......................................................................................................................... 23

7. Flow calculations for six selected unsaturated-zone sampling sites, southern

New Jersey......................................................................................................................... 26
iv

CONVERSION FACTORS AND ABBREVIATIONS

MULTIPLY BY TO OBTAIN

micron (mm) 0.00003937 inches

centimeter (cm) 0.3937 inches

square kilometer (km2) 0.3861 square miles

cubic centimeter (cm3) 0.061 cubic inches
1

ESTIMATING SPATIAL VARIABILITY OF RECHARGE IN SOUTHERN 

NEW JERSEY FROM UNSATURATED-ZONE MEASUREMENTS

By Arthur L. Baehr, Leon J. Kauffman, Kimberlie Perkins, and Bernard T. Nolan

ABSTRACT

Spatial variability of recharge in southern 

New Jersey was studied by sampling the unsaturated zone at 48 sites distributed over approximately 930 square kilometers. Samples of 

unsaturated-zone sediment were collected during 

the summer and fall of 1996. Unsaturated flow 

was calculated using moisture-content data and 

estimates of conductivity and matric potential 

derived from sediment-size data. Matric forces 

were found to be important at about 70 percent of 

the sites despite the expectation that unsaturated 

flow in a humid climate is gravity driven. Upward 

water movement occurred at about 17 percent of 

the sites. The lower sediment layer at these sites 

consisted of sandy loam, indicating that upward 

movement can occur at depth only where the 

sediments are relatively fine-grained. At the other 

extreme, calculated flow at about 17 percent of the 

sites exceeded 250 centimeters per year. Because 

of the uncertainty inherent in unsaturated-flow 

calculations, the method provides only a scaling of 

recharge variability; however, the median calculated flow of 29.1 centimeters per year compares 

favorably with recharge estimates from previous 

water-budget studies. A map developed by spatial 

analysis of the recharge estimates identified an 

agricultural part of the study area where recharge 

was known to be low relative to recharge in other 

basins.

INTRODUCTION

Recharge, the rate at which water moves 

across the water table, is typically quantified at the 

watershed scale by considering its relation to more 

readily measurable components of the water 

budget. For example, in the case of a surficial 

aquifer,

R = Q0 - Qi + Qp , (1)

where R is recharge, Q0 is stream outflow, Qi is 

stream inflow, and Qp is water use. By using this 

equation, a single value for recharge across the 

watershed can be calculated. This method of estimating recharge is described by Rutledge (1997).

Although an average value of recharge for a 

watershed serves to quantify the bulk movement of 

water through the hydrologic cycle, information on 

its spatial variability is needed to estimate contaminant loading to an aquifer because chemical use 

varies within the watershed (fig. 1). The relation of 

recharge at a particular location to topography, 

stormwater-management practices, and the 

hydraulic properties of the unsaturated zone, 

however, cannot be determined without additional 

data. Soils maps of a watershed, even if available, 

do not characterize unsaturated-zone sediments at 

depths greater than a few feet. Furthermore, the 

moisture content through the unsaturated zone 

generally is unknown.

The U.S. Geological Survey (USGS) 

conducted a study of the unsaturated zone in 

southern New Jersey to estimate the spatial 

variability of recharge to an unconfined aquifer. 

During July 30-October 24, 1996, samples of 

unsaturated-zone sediments were collected during 

the installation of 48 observation wells in the 

Kirkwood-Cohansey aquifer system over an area 

of approximately 930 km2. The installation of the 

observation wells provided an opportunity to map 

unsaturated-zone sediment properties, collect core 

samples for analysis, and obtain one-time 

moisture-content data at these locations. Pedotransfer functions were used to estimate hydraulic 

conductivity and matric potential on the basis of 

sediment size-distribution data. Darcy’s Law was 

applied to compute unsaturated flow within a 

sediment layer encountered below the soil zone at 

each site. These flow values are assumed to 

provide a “snapshot” of spatial variations in 

recharge over the study area. Because the flow 
2

Figure 1. The hydrologic cycle in a watershed with various land uses.

Figure 2. Location of unsaturated-zone sampling sites, 

Glassboro study area.

Ground water

Precipitation

Unsaturated zone

Recharge

Base from U.S. Geological Survey, Wilmington,

Hammonton 1:250,000 quadrangles, 1969,

Universal Transverse Mercator Projection, Zone 18

SUSSEX

KENT

DELAWARE BAY

CAPE MAY

CUMBERLAND

ATLANTIC

SALEM

GLOUCESTER

CAMDEN

MONMOUTH

OCEAN

BURLINGTON

MERCER BUCKS

PHILADELPHIA

DELAWARE

NEW

CASTLE

PENNSYLVANIA

NEW JERSEY

DELAWARE

DELAWARE RIVER

39

30’

40

00’

39

00’

75 30’ 75 00’ 74 30’ 74 00’

A T L

A

N

T I C

O

C

E

A

N

0 10 20 MILES

0 10 20 KILOMETERS

Outcrop area of the KirkwoodCohansey aquifer system

Glassboro study area

EXPLANATION
3

values are based on unsaturated-zone observation, 

they incorporate the effects of variable sediment 

properties and of other factors that can cause 

recharge to vary spatially, such as topography and 

stormwater-management practices.

This report presents the results of the unsaturated-zone study. It includes a summary of unsaturated-zone sediment properties, an evaluation of 

pedotransfer function parameters, and a map of the 

study area showing areas of relatively high and low 

recharge. The results of this study can be used in 

conjunction with land-use information to develop a 

conceptual understanding of the spatial variation of 

movement of chemicals into the KirkwoodCohansey aquifer system.

STUDY AREA

The study area (fig. 2) consists of approximately 930 km2 in the Coastal Plain Physiographic 

Province encompassing Glassboro in southern 

New Jersey (hereafter called the Glassboro study 

area). The population in the study area, estimated 

from census data, was about 50,000 in 1940, 

100,000 in 1960, 180,000 in 1980, and 250,000 in 

2000. Water pumped from the surficial KirkwoodCohansey aquifer system (hereafter called the 

aquifer) has increased in recent years as communities meet the water demands associated with the 

rapid suburban growth. The outcrop of the 

Kirkwood Formation, a confining unit about 30 m 

thick, forms the northwestern boundary of the 

study area and underlies the aquifer, which consists 

of unconsolidated sand and gravel. The aquifer 

thickens to the southeast and is about 75 m thick at 

the southeastern boundary of the study area 

(Zapecza, 1989).

Most of the unsaturated zone is made up of 

the Cohansey Sand, which was was deposited 

during the Miocene Age. Its depositional history is 

one of inner shelf, nearshore, and beach environments during a slow retreat of the sea. The 

sediments of the Cohansey Sand, like those of 

similarly deposited formations of the New Jersey 

Coastal Plain, generally coarsen upward (Zapecza, 

1989). In some areas, the Bridgeton Formation 

overlies the Cohansey Sand. Coarse, pebbly, 

orange sands that were deposited under continental 

conditions during the late Tertiary and Quaternary 

Periods characterize this formation. Where present 

in the study area, the Bridgeton Formation 

generally is less than 3 m thick.

Annual recharge to the aquifer in several 

watersheds in southern New Jersey has been 

estimated by water-budget methods through a 

program of surficial-aquifer studies conducted by 

the USGS (Watt and Johnson, 1992; Watt and 

others, 1994; Johnson and Watt, 1997; Johnson and 

Charles, 1997; Charles and others, 2001). These 

estimates range from 33.1 to 49.3 cm/yr. Average 

annual precipitation in the study area is about 

109.3 cm, of which 25.4, 29.1, 29.1, and 25.8 cm 

falls during winter, spring, summer, and fall 

respectively. Although precipitation is nearly 

evenly distributed throughout the year, the average 

daily temperature varies seasonally (0.8, 11.1, 23.2, 

and 13.7 oC during winter, spring, summer, and 

fall, respectively). Estimated seasonal potential 

evapotranspiration obtained by the Thornthwaite 

method (Thornthwaite and Mather, 1957) is 0.7, 

14.9, 41.5, and 16.2 cm, respectively.

STUDY METHODS

Unsaturated-zone sediment was sampled at 48 

sites during the installation of shallow-groundwater observation wells in summer and fall 1996 

(fig. 3). Unsaturated flow was calculated using 

moisture-content data and estimates of conductivity and matric potential derived from sedimentsize data.

Unsaturated-Zone Sampling

Site locations were selected at random within 

major land-use categories to assess ambient 

shallow-ground-water quality (Stackelberg and 

others, 1997). Core samples were collected 

throughout the unsaturated zone by driving a 61-

cm-long by 5.1-cm- diameter split-spoon sampler 

with a drill rig hammer. A sediment sample of 

about 30 cm3 was removed from the bottom end of 

each core to obtain values of moisture content and 

bulk density through use of gravimetric methods. 

Sediment layers, evidenced by visible changes in 

color and texture, were noted and the core samples 

were stored. Site locations and unsaturated-zone 

thickness are listed in table 1. Moisture contents as 

a function of depth at the sites are listed in table 2.
4

Figure 3. Location of unsaturated-zone sampling sites, Glassboro study area.

0 5 MILES

0 5 KILOMETERS

39°

30’

39°

45’

75°

75°15’

Study-area boundary

Unsaturated-zone

sampling

EXPLANATION
5

Table 1. Unsaturated-zone sampling sites, southern New Jersey

1Water level measured to determine unsaturated-zone thickness, typically on or shortly after date of well installation.

Site name

Altitude of site 

(meters above

sea level) Latitude Longitude

Unsaturated-zone 

thickness

(meters)

Date of

water-level 

measurement1

AG01 36.6 393415.4 745635.1 4.5 8/06/1996

AG02 42.7 394302.6 751012.4 6.9 8/02/1996

AG03 43.3 393915.5 751220.9 3.6 8/02/1996

AG04 40.2 393627.0 751122.3 3.9 8/06/1996

AG09 38.1 393710.9 751209.8 2.0 9/11/1996

AG10 42.7 393413.2 751416.5 6.4 9/12/1996

AG11 39.6 393541.7 751102.9 2.7 9/12/1996

AG12 37.2 393158.9 751502.2 8.7 9/17/1996

AG13 29.0 393213.1 751556.2 3.4 9/17/1996

AG14 38.1 393051.7 751801.0 7.6 9/20/1996

AG15 26.8 393016.9 750544.0 5.8 10/08/1996

NU01 45.7 394326.7 750457.4 8.5 8/16/1996

NU02 43.3 394342.6 750400.6 2.3 8/16/1996

NU04 36.6 394458.0 750400.3 1.9 8/19/1996

NU06 53.3 394527.1 750039.5 13.1 8/20/1996

NU08 47.2 394338.9 750126.3 6.2 8/21/1996

NU09 44.2 394022.5 745909.1 6.1 8/22/1996

NU11 50.3 394604.5 750033.5 6.7 8/26/1996

NU12 47.2 394734.5 745641.2 2.5 8/27/1996

NU19 44.2 394254.5 745903.0 3.7 11/05/1996

NU21a 53.3 394640.0 745939.0 4.3 9/11/1996

NU22 44.2 394145.5 745913.3 3.0 11/14/1996

NU23 44.2 394154.0 750111.4 1.5 10/18/1996

NU24 42.7 394241.4 750506.2 4.7 9/24/1996

NU27 35.1 394942.0 745508.8 1.3 11/13/1996

NU29 36.6 394442.9 750307.4 2.4 11/06/1996

OU02 34.7 392919.8 750116.7 12.3 9/24/1996

OU03 48.2 394233.3 750136.2 5.4 10/02/1996

OU04 40.2 393917.1 750136.2 4.7 10/02/1996

OU05 22.9 393530.3 745237.8 2.8 10/03/1996

OU06 44.2 394104.1 745930.4 3.5 11/05/1996

OU07 27.4 392929.2 750159.1 4.9 11/21/1996

OU08 47.2 394747.9 745549.1 2.1 10/07/1996

OU10 29.3 392917.7 750036.7 6.4 11/19/1996

OU11 33.5 394351.0 750801.0 2.8 10/31/1996

OU13 39.6 394234.9 750713.4 2.1 10/31/1996

OU14 47.2 394645.5 745919.8 3.1 11/15/1996

OU15 29.0 392827.8 750138.3 8.1 9/16/1997

UN01 42.7 394141.8 745503.7 7.8 8/06/1996

UN02 15.2 392544.9 750507.7 4.3 9/13/1996

UN03 37.5 394023.3 750347.7 2.0 9/18/1996

UN05 38.7 393943.3 750304.9 2.5 10/03/1996

UN06 29.6 393751.8 745512.6 1.7 10/03/1996

UN07 30.2 393029.7 750907.3 4.6 11/2719/96

UN08 34.4 393339.4 745514.5 2.2 10/03/1996

UN09 30.5 393939.3 745341.5 1.1 10/03/1996

UN11 30.5 394710.0 750039.0 4.7 1/15/1996

UN12 25.9 393439.4 750431.0 1.5 11/04/1996
6

Table 2. Moisture content1 at unsaturated-zone sampling sites[--, depth below water table therefore moisture content not determined]

Site 

name

Date of

moisturecontent 

measurement2

Depth (meters below land surface)

0.6 1.2 1.8 2.4 3.0 3.7 4.3 4.9 5.5 6.1 6.7 7.3 7.9 8.5

AG01 7/31/1996 0.13 0.27 0.22 0.25 0.44 0.22 0.26 -- -- -- -- -- -- --AG02 7/31/1996 0.15 0.19 0.10 0.28 0.08 0.12 0.12 0.12 0.09 0.09 0.10AG03 8/01/1996 0.42 0.24 0.10 0.08 0.20 -- -- -- -- -- -- -- -- --AG04 8/01/1996 0.28 0.12 0.16 0.16 0.27 0.24 -- -- -- -- -- -- -- --AG09 9/11/1996 0.09 0.11 -- -- -- -- -- -- -- -- -- -- -- --AG10 9/12/1996 0.30 0.20 0.16 0.11 0.11 0.15 0.13 0.09 0.14 0.26 -- -- -- --AG11 9/12/1996 0.05 0.09 0.07 0.15 -- -- -- -- -- -- -- -- -- --AG12 9/17/1996 0.07 0.13 0.14 0.03 0.16 0.08 0.06 0.08 0.06 0.06 0.23 -- -- --AG13 9/17/1996 0.37 0.17 0.13 0.10 -- -- -- -- -- -- -- -- -- --AG14 9/17/1996 0.33 0.17 0.03 0.13 0.10 0.17 0.04 0.04 0.04 0.03 0.04 -- -- --AG15 9/20/1996 0.10 0.03 0.03 0.14 0.12 0.06 0.06 0.07 0.18 -- -- -- -- --NU01 8/14/1996 0.14 0.13 0.14 0.06 0.09 0.07 0.05 0.08 0.23 0.14 0.13 0.12 0.09 0.11NU02 8/15/1996 0.13 0.04 0.12 -- -- -- -- -- -- -- -- -- -- --NU04 8/19/1996 0.04 0.22 0.32 -- -- -- -- -- -- -- -- -- -- --NU06 8/20/1996 0.09 0.35 0.16 0.07 0.18 0.17 0.17 0.14 0.07 0.11 0.17 0.07 0.06NU08 8/21/1996 0.15 0.10 0.13 0.13 0.10 0.10 0.16 0.11 0.12 0.14 -- -- -- --NU09 8/22/1996 0.24 0.32 0.07 0.05 0.09 0.05 0.08 0.04 -- -- -- -- -- --NU11 8/26/1996 0.05 0.07 0.07 0.05 0.03 0.04 0.03 0.05 0.05 0.03 -- -- -- --NU12 8/27/1996 0.14 0.04 0.06 0.16 -- -- -- -- -- -- -- -- -- --NU19 9/10/1996 0.11 0.21 0.19 0.17 0.14 0.29 -- -- -- -- -- -- -- --NU21a 9/11/1996 0.06 0.10 0.08 0.04 0.05 0.05 0.08 -- -- -- -- -- -- --NU22 9/23/1996 0.10 0.05 0.12 0.16 -- -- -- -- -- -- -- -- -- --NU23 9/23/1996 0.21 0.25 -- -- -- -- -- -- -- -- -- -- -- --NU24 9/24/1996 0.10 0.13 0.12 0.17 0.04 0.13 0.32 -- -- -- -- -- -- --NU27 9/25/1996 0.15 -- -- -- -- -- -- -- -- -- -- -- -- --NU29 10/10/1996 0.11 0.08 0.11 0.10 -- -- -- -- -- -- -- -- -- --OU02 9/24/1996 0.15 0.46 0.17 0.16 0.16 0.16 0.17 0.07 0.10 0.15 0.11 0.14 0.14 0.08OU03 9/25/1996 0.17 0.12 0.14 0.20 0.26 0.23 0.06 -- -- -- -- -- -- --OU04 9/25/1996 0.16 0.21 0.06 0.05 0.14 0.18 0.22 -- -- -- -- -- -- --OU05 9/26/1996 0.03 0.03 0.02 0.14 -- -- -- -- -- -- -- -- -- --
7

1Moisture content (θ) is dimensionless. Its value is calculated as follows:

θ = (W)(BD) where W is the weight of water in the sample divided by the dry weight of the sample and BD is the dry bulk density of the sample (see table 3). If BD is not given for a layer, the value for the adjacent lower layer is used.

OU06

2Moisture content measured on date of well installation.

9/26/1996 0.19 0.11 0.09 0.07 0.12 -- -- -- -- -- -- -- -- --

OU07 10/29/1996 0.06 0.15 0.09 0.22 0.19 0.21 -- -- -- -- -- -- -- --OU08 10/07/1996 0.07 0.10 0.27 -- -- -- -- -- -- -- -- -- -- --OU10 10/09/1996 0.13 0.06 0.12 0.10 0.15 0.20 0.19 0.09 0.21 0.16 -- -- -- --OU11 10/23/1996 0.15 0.04 0.12 0.25 -- -- -- -- -- -- -- -- -- --OU13 10/23/1996 0.12 0.21 -- -- -- -- -- -- -- -- -- -- -- --OU14 10/24/1996 0.12 0.11 0.09 0.29 0.29 -- -- -- -- -- -- -- -- --OU15 9/16/1997 0.16 0.15 0.13 0.12 0.08 0.16 0.11 0.18 0.13 -- -- -- --UN01 7/30/1996 -- 0.19 -- -- 0.16 0.18 -- -- 0.12 -- 0.08 -- -- --UN02 9/13/1996 0.01 0.002 0.03 0.03 0.05 -- -- -- -- -- -- -- -- --UN03 9/18/1996 0.09 0.06 0.24 -- -- -- -- -- -- -- -- -- -- --UN05 9/19/1996 0.10 0.19 0.19 0.22 -- -- -- -- -- -- -- -- -- --UN06 9/19/1996 0.12 0.18 -- -- -- -- -- -- -- -- -- -- -- --UN07 9/24/1996 0.12 0.11 0.47 0.25 0.30 0.30 -- -- -- -- -- -- -- --UN08 9/26/1996 0.06 0.06 0.12 -- -- -- -- -- -- -- -- -- -- --UN09 9/26/1996 0.10 -- -- -- -- -- -- -- -- -- -- -- -- --UN11 10/10/1996 0.14 0.14 0.12 0.09 0.07 0.34 0.32 -- -- -- -- -- -- --UN12 10/24/1996 0.09 0.20 -- -- -- -- -- -- -- -- -- -- -- --

Site 

name

Date of

moisturecontent 

measurement2

Depth (meters below land surface)

0.6 1.2 1.8 2.4 3.0 3.7 4.3 4.9 5.5 6.1 6.7 7.3 7.9 8.5

Table 2. Moisture content1 at unsaturated-zone sampling sites, southern New Jersey--Continued
8

To map sediment-size distribution for the 

layers encountered, samples of about 50 cm3 were 

taken from 109 cores. Samples were analyzed by 

optical diffraction using a Coulter LS-230 Particle 

Size Analyzer. This method allows for the partitioning of particle sizes ranging from 0.04 to 

2,000 μm into about 120 bins. Particles larger than 

2,000 μm (gravel) were sieved out and then 

integrated into the size-distribution results. The 

fraction smaller than 2,000 μm was disaggregated 

if necessary with a mortar and rubber-tipped pestle, 

then split with a riffle splitter to obtain appropriate 

random samples for analysis. The material was 

sonicated in suspension for 60 seconds prior to 

each run.

Sediment properties, including layer 

description, bulk density, porosity, and textural 

classification, are summarized in table 3. Particlesize distributions (table 4) were determined from 

samples representing many of the layers. The 

sediments were mostly sands according to textural 

classification. Descriptions of layers in the 

saturated zone between the water table and the 

bottom of the well, where listed, are approximate 

and are based on observations of drill cuttings, not 

core samples. The average unsaturated-zone 

thickness at the 48 sites was 4.4 m.

Flow Calculation

Darcy’s Law for unsaturated-zone flow is as 

follows:

 , (2)

where q is the rate of flow (cm/d), K is the hydraulic conductivity (cm/d), is the matric potential 

(cm), and z is the vertical coordinate (cm), which is 

positive upward. Both K and are functions of 

moisture content, . The matric potential is 

defined according to the model of van Genuchten 

(1980) as follows:

 , (3)

where (1/cm) and n (dimensionless) are curvefitting parameters. The parameter 1/ is referred 

to as the air entry pressure. The relative saturation 

Se is defined as follows:

 , (4)

where r and s are residual and saturated moisture contents, respectively. 

Equation (3) is used in conjunction with the 

pore-size-distribution model of Mualem (1976) to 

yield the van Genuchten-Mualem model (van 

Genuchten, 1980) for K:

 , (5)

where K0 (cm/d) and L (dimensionless) are curvefitting parameters.

Hydraulic properties can be estimated 

indirectly from sediment-texture data with quasiempirical models known as pedotransfer functions. 

The models given by equations (3) and (5) were 

selected from among alternative formulations in 

order to use the pedotransfer functions incorporated in the program and database known as 

Rosetta (U.S. Department of Agriculture, 2002). 

Bulk density and the fractions of sand, silt, and 

clay were input to obtain estimates of the parameters r

, s, , n, K0 , and L for each layer for 

which texture data were collected (table 5). The 

pedotransfer functions are based on neural network 

analyses described by Schaap and Leij (1998), 

Schaap and others (1998), and Schaap and others 

(1999). The Rosetta program is discussed by 

Schaap and others (2001).

q K1 dψ

dz = – – -------

ψ

ψ

θ

ψ

1

α

--- Se

n1n ⁄ ( ) – [ ] – 1

1 n⁄ =

α

α

Se

θ θ – r

θs θr – = ---------------

θ θ

K K0Se

L 1 1Senn1 ⁄ ( ) – [ ] – 1 1n – ⁄ –

⎩ ⎭ ⎨ ⎬ ⎧ ⎫2

=

θ θ α
9

Table 3. Unsaturated-zone characteristics at sampling sites, southern New Jersey

[-- , not measured; BLS, below land surface; m, meters; g/cm3, grams per cubic centimeter]

Site name

Unsaturatedzone 

thickness 

(m)

Layer interval1

Field description2

Textural 

classification3

Bulk 

density

(g/cm3) Porosity4 Top(m BLS)

Bottom

(m BLS)

AG01 4.5 0.0 0.3 topsoil -- -- --

0.3 0.8 tan, coarse loamy sand 1.9 0.30

0.8 2.3 tan, finer sandy loam 1.6 0.41

2.3 7.3 orange sandy loam 1.6 0.41

AG02 6.9 0.0 0.6 topsoil -- -- --

0.6 1.2 orange, coarse sand 1.6 0.40

1.2 5.5 orange, coarse sand 1.7 0.39

5.5 7.6 orange, coarse sand 1.7 0.39

sand 1.6 0.41

AG03 3.6 0.0 0.6 topsoil -- -- --

0.6 1.8 orange, coarse sand 1.5 0.43

1.8 6.7 gray, coarse sand 1.7 0.36

loamy sand 1.7 0.35

AG04 3.9 0.0 0.3 topsoil -- -- --

0.3 2.7 brown sandy loam 1.8 0.33

2.7 6.1 brown loamy sand 2.0 0.27

AG09 2.0 0.0 0.2 topsoil -- -- --

0.2 1.8 orange loamy sand 1.7 0.35

1.8 2.1 gray, medium sand -- -- --

2.1 5.8 orange, medium coarse sand -- -- --

AG10 6.4 0.0 2.1 brown loamy sand 1.6 0.41

2.1 4.9 orange, coarse with gravel sand 1.6 0.42

4.9 9.8 orange, coarse sand 1.6 0.41

AG11 2.7 0.0 0.3 topsoil -- -- --

0.3 1.2 orange sandy loam 1.8 0.34

1.2 2.7 tan, medium with pebbles sand 1.6 0.42

2.7 3.7 orange, medium sandy loam 1.5 0.45

3.7 6.7 white, medium sand -- -- --

AG12 8.7 0.0 0.2 topsoil -- -- --

0.2 1.8 red, clayey sandy loam 1.6 0.39

1.8 2.4 tan, coarse sand 1.6 0.41

2.4 4.6 med. tan sand 1.6 0.39

4.6 11.0 red, fine-medium sand 1.4 0.45

11.0 11.9 brown, medium

AG13 3.4 0.0 0.3 topsoil -- -- --

0.3 3.4 red-brown, coarse sand 1.4 0.49

3.4 6.7 orange, medium sand 1.5 0.45

AG14 7.6 0.0 0.3 topsoil

0.3 2.6 brown loamy sand 1.7 0.36

2.6 4.3 orange, fine-medium sandy loam 1.7 0.38

4.3 5.8 orange, coarse sand 1.5 0.45

5.8 7.0 yellow, medium sand -- -- --

7.0 10.4 orange, medium sand -- -- --
10

AG15 5.8 0.0 0.2 topsoil -- -- --

0.2 0.9 brown, clayey sand -- -- --

0.9 1.7 brown, medium sand -- -- --

1.7 2.7 brown, medium sand 1.6 0.40

2.7 8.8 brown, medium-coarse sand 1.6 0.39

sand 1.7 0.43

sand 1.7 0.40

NU01 8.5 0.0 0.2 topsoil -- -- --

0.2 2.6 loamy sand 1.7 0.37

2.6 3.4 orange fine sand --

3.4 4.9 white, fine sand 1.6 0.39

4.9 7.6 orange sandy loam 1.7 0.40

7.6 10.7 orange sandy loam 1.5 0.44

10.7 12.2 red, coarse sand -- -- --

NU02 2.3 0.0 0.3 topsoil -- -- --

0.3 2.0 tan, medium sand 1.5 0.46

2.0 2.4 fine sand 1.7 0.36

2.4 5.8 coarse sand -- -- --

NU04 1.9 0.0 0.2 topsoil -- -- --

0.2 1.8 brown sandy loam 1.5 0.43

1.8 7.0 yellow, fine sand -- -- --

NU06 13.1 0.0 0.2 topsoil -- -- --

0.2 2.4 orange loamy sand 1.9 0.30

2.4 4.9 orange, medium sand 1.7 0.38

4.9 12.2 brown, fine sand 1.4 0.47

12.2 15.8 orange, medium sand -- -- --

NU08 6.2 0.0 0.2 topsoil -- -- --

0.2 0.6 tan, fine sand -- -- --

0.6 9.1 orange, fine-medium sand 1.5 0.43

sand 1.5 0.44

sand 1.7 0.40

NU09 6.1 0.0 0.3 topsoil -- -- --

0.3 9.4 orange sandy loam 1.8 0.37

Sand 1.4 0.48

NU11 6.7 0.0 0.9 brown, coarse sand -- -- --

0.9 1.4 dark brown, coarse sand -- -- --

1.4 7.3 brown, coarse sand 1.5 0.45

sand 1.5 0.43

NU12 2.5 0.0 0.3 topsoil -- -- --

0.3 5.5 yellow, medium-coarse sand 1.5 0.43

NU19 3.7 0.0 0.3 topsoil -- -- --

0.3 2.4 orange sandy loam 1.5 0.44

2.4 3.7 orange, fine-medium sand -- -- --

3.7 8.8 orange, fine sand -- -- --

Site name

Unsaturatedzone 

thickness 

(m)

Layer interval1

Field description2

Textural 

classification3

Bulk 

density

(g/cm3) Porosity4 Top(m BLS)

Bottom

(m BLS)

Table 3. Unsaturated-zone characteristics at sampling sites, southern New Jersey--Continued
11

NU21a 4.3 0.0 0.3 topsoil -- -- --

0.3 3.0 brown-coarse with pebbles -- -- --

3.0 3.7 orange, very coarse sand 1.7 0.38

3.7 4.3 rose, coarse -- -- --

NU-22 3.0 0.0 0.3 topsoil -- -- --

0.3 0.6 orange, medium sand -- -- --

0.6 1.5 red, medium sand -- -- --

1.5 3.0 yellow sandy loam 1.5 0.46

NU23 1.5 0.0 0.3 topsoil -- -- --

0.3 0.8 red, fine sand -- -- --

0.8 1.5 clayey sandy loam 1.6 0.41

1.5 2.4 orange, sandy clay -- -- --

NU24 4.7 0.0 0.3 topsoil -- -- --

0.3 0.6 orange, medium sand -- -- --

0.6 1.5 red, medium sand 1.4 0.47

1.5 3.7 orange, medium sand 1.5 0.44

3.7 4.7 red, medium sand -- -- --

NU27 1.3 0.0 0.3 topsoil -- -- --

0.3 1.2 brown, medium sand -- -- --

1.2 1.8 black sand 1.7 0.36

1.8 3.0 gray, fine sand -- -- --

3.0 4.3 brown, silty sand -- -- --

NU29 2.4 0.0 0.2 topsoil -- -- --

0.2 5.8 brown, medium sand 1.4 0.49

OU02 12.3 0.0 1.2 brown loamy sand 1.8 0.33

1.2 2.7 red sandy loam 1.7 0.37

2.7 4.0 gray loamy sand 1.7 0.36

4.0 8.8 tan, coarse sand 1.6 0.41

8.8 10.1 tan, medium sand -- -- --

10.1 10.7 gray, coarse sand -- -- --

10.7 15.5 orange fine-medium sand -- -- --

OU03 5.4 0.0 1.8 brown loamy sand 1.5 0.42

1.8 2.4 fine sand -- -- --

2.4 3.4 orange loam 1.9 0.31

3.4 8.5 white sandy loam 1.5 0.46

OU04 4.7 0.0 0.3 topsoil -- -- --

0.3 1.8 brown sand 1.7 0.37

1.8 2.7 tan, coarse sand 1.4 0.47

2.7 6.4 brown sandy loam 1.6 0.40

6.4 7.6 medium-fine sand -- -- --

7.6 8.2 white, coarse sand -- -- --

OU05 2.8 0.0 1.5 gray-black sand 1.7 0.37

1.5 2.4 brown, medium sand -- -- --

2.4 5.8 tan, medium sand -- -- --

Site name

Unsaturatedzone 

thickness 

(m)

Layer interval1

Field description2

Textural 

classification3

Bulk 

density

(g/cm3) Porosity4 Top(m BLS)

Bottom

(m BLS)

Table 3. Unsaturated-zone characteristics at sampling sites, southern New Jersey--Continued
12

OU06 3.5 0.0 0.2 topsoil -- -- --

0.2 1.5 brown sand 1.9 0.29

1.5 4.0 brown loam 1.7 0.37

4.0 6.7 orange, coarse sand -- -- --

OU07 4.9 0.0 0.2 topsoil

0.2 0.9 brown, fine sand 1.6 0.42

0.9 3.4 brown sandy loam 1.5 0.45

3.4 4.9 orange sandy loam 1.5 0.45

4.9 5.8 yellow loam 1.3 0.53

5.8 6.1 brown, medium sand -- -- --

6.1 6.7 brown, sandy clay -- -- --

OU08 2.1 0.0 0.3 topsoil -- -- --

0.3 0.6 black clay -- -- --

0.6 1.5 brown, medium sand -- -- --

1.5 1.8 black sandy loam 1.1 0.59

1.8 5.8 clayey gray sand -- -- --

OU10 6.4 0.0 0.3 topsoil -- -- --

0.3 2.1 brown, coarse sand 1.5 0.43

2.1 2.7 white coarse sand -- -- --

2.7 3.4 orange, medium sand 1.8 0.34

3.4 4.9 white, coarse sand 1.9 0.28

4.9 9.8 yellow, coarse sand -- -- --

OU11 2.8 0.0 0.3 topsoil -- -- --

0.3 2.1 gravelly sand -- -- --

2.1 5.8 orange sandy loam 1.6 0.42

OU13 2.1 0.0 0.3 topsoil -- -- --

0.3 0.8 orange, fine-medium sand -- -- --

0.8 5.2 brown sandy loam 1.4 0.46

brown sandy loam

OU14 3.1 0.0 0.2 topsoil -- -- --

0.2 2.1 brown, coarse sand 1.7 0.38

2.1 5.8 brown medium sand 1.3 0.50

OU15 8.1 0.0 0.3 topsoil -- -- --

0.3 3.0 orange, coarse sand sand 1.7 0.37

3.0 4.3 yellow, medium sand 1.7 0.35

4.3 6.1 orange, fine-medium sand 1.8 0.34

6.1 7.9 red, medium sand -- -- --

7.9 11.3 orange, fine-medium sand -- -- --

UN01 7.8 0.0 0.3 topsoil -- -- --

0.3 3.4 brown,coarse sand -- -- --

3.4 7.8 white, coarse sand 1.7 0.36

UN02 4.3 0.0 0.3 topsoil -- -- --

0.3 4.6 orange, coarse sand 1.7 0.35

4.6 7.9 red, coarse sand -- -- --

Site name

Unsaturatedzone 

thickness 

(m)

Layer interval1

Field description2

Textural 

classification3

Bulk 

density

(g/cm3) Porosity4 Top(m BLS)

Bottom

(m BLS)

Table 3. Unsaturated-zone characteristics at sampling sites, southern New Jersey--Continued
13

1Visual description from field notes. Descriptions of layers in the saturated zone between the water table and the bottom of the

well, where listed, are approximate and are based on observations of drill cuttings, not core samples.

2Color is based on moist-sediment appearance. Layers were identified visually without size-distribution data; therefore, the textural descriptions are useful for comparison of layers at a particular site, but may not be consistent between sites. Only size-distribution data should be used to compare sediments collected at different sites.

3

U.S. Department of Agriculture description based on percent (by weight) of sand, silt, and clay. Textural classification provided 

only if size analysis available (see table 4).

4Porosity was computed from the measured bulk density by assuming a grain density of 2.67 g/cm3.

UN03 2.0 0.0 0.3 topsoil -- -- --

0.3 1.5 brown, medium sand 1.7 0.38

1.5 3.0 brown, silty sand 1.6 0.38

3.0 5.5 yellow, clayey sand -- -- --

UN05 2.5 0.0 0.2 topsoil -- -- --

0.2 2.1 -- -- --

2.1 2.7 orange sandy loam 1.6 0.40

2.7 5.8 orange loam 1.6 0.40

5.8 6.7 yellow, sand -- -- --

UN06 1.7 0.0 0.3 topsoil -- -- --

0.3 4.6 sand 1.6 0.41

UN07 4.6 0.0 0.3 topsoil -- -- --

0.3 1.8 red, medium coarse sand 1.5 0.44

1.8 3.0 white-orange loam 1.4 0.47

3.0 3.7 clayey sand -- -- --

3.7 4.6 red, sand -- -- --

4.6 5.5 orange sand -- -- --

5.5 6.1 brown, medium-coarse sand -- -- --

UN08 2.2 0.0 0.3 topsoil -- -- --

0.3 3.4 brown, medium sand 1.6 0.40

3.4 4.3 fine sand -- -- --

UN09 1.1 0.0 0.3 topsoil -- -- --

0.3 4.0 gray, medium sand 1.7 0.36

UN11 4.7 0.3 4.6 brown, medium sand 1.4 0.49

4.6 6.1 fine-medium sand 1.4 0.46

6.1 7.0 gray, silty sand -- -- --

UN12 1.5 0.0 0.3 topsoil -- -- --

0.3 4.6 brown, coarse sand 1.5 0.44

Site name

Unsaturatedzone 

thickness 

(m)

Layer interval1

Field description2

Textural 

classification3

Bulk 

density

(g/cm3) Porosity4 Top(m BLS)

Bottom

(m BLS)

Table 3. Unsaturated-zone characteristics at sampling sites, southern New Jersey--Continued
14

Table 4. Particle-size distribution in samples from unsaturated-zone sampling sites, southern New Jersey[BLS, below land surface; m, meter; μm, micron; <, less than; >, greater than; rep, replicate sample]

Site name

Sample

depth1

(m BLS)

Percent (by weight) of sample in size range

Clay

(<2μm)

Silt

(2-50 μm)

Very fine 

sand

(50-100 μm)

Fine sand

(100-

250 μm)

Medium 

sand

(250-

500 μm)

Coarse 

sand

(500-

1,000 μm)

Very coarse 

sand

(1,000-

2,000 μm)

Gravel

(>2,000 μm)

2d50

(μm) 3Cu 4Cg

AG01 0.6 3.3 16.0 5.4 14.4 13.3 15.5 11.3 20.9 436 61.0 2.6

1.8 6.0 27.3 6.3 24.9 29.4 5.8 0.2 0.0 176 54.4 1.43.7 8.0 33.3 5.4 26.1 23.2 3.8 0.2 0.0 130 67.9 0.8

AG02 1.2 2.4 11.7 3.9 4.1 4.3 19.8 40.6 13.2 1032 59.6 9.7

2.1 2.2 11.2 4.9 7.0 11.6 22.9 28.7 11.4 762 32.7 4.04.3 1.0 5.4 2.9 4.2 10.8 36.6 34.0 5.2 831 7.5 3.06.1 0.9 4.1 1.6 3.6 8.2 31.9 40.4 9.7 949 4.8 2.3

AG03 1.2 1.2 6.5 3.1 8.3 13.3 28.2 31.6 7.9 784 11.7 2.6

2.4 1.1 4.2 1.8 4.2 13.8 26.0 25.4 23.4 923 6.7 1.53.7 3.5 16.0 5.1 4.4 5.9 20.7 27.1 17.2 833 78.2 5.8

AG04 1.8 4.0 26.6 5.6 10.4 25.0 20.2 7.8 0.5 265 42.2 0.7

3.7 3.6 20.0 6.0 19.9 21.9 14.0 12.7 1.9 237 29.3 2.9

AG09 1.2 2.6 19.7 5.5 8.7 17.9 25.3 17.6 2.8 419 38.1 1.9AG10 1.8 1.9 15.4 5.2 5.3 6.8 22.8 16.3 26.3 882 44.9 4.2

4.3 1.7 10.4 3.1 6.0 16.3 20.8 20.6 21.1 822 30.4 4.06.1 1.1 6.4 2.2 4.2 8.5 32.6 33.8 11.2 877 10.3 3.7

AG11 0.6 4.4 33.3 13.3 11.0 11.1 14.4 6.6 5.9 94 27.5 0.8

1.8 1.1 4.3 2.2 5.5 14.6 38.1 26.1 8.1 759 5.6 2.03.0 5.3 20.8 4.1 12.9 51.8 5.0 0.1 0.0 263 63.4 5.7

AG12 1.2 2.2 22.1 9.5 5.1 8.6 21.0 16.5 14.9 536 45.5 0.4

2.4 0.4 1.8 1.0 2.6 6.5 33.4 54.3 0.0 991 2.6 1.43.7 0.7 2.4 1.2 4.1 9.1 40.3 40.5 1.7 874 3.4 1.74.9 1.9 7.1 4.0 52.7 31.5 2.9 0.0 0.0 210 3.6 1.9

AG13 1.8 1.8 9.4 4.3 11.9 25.7 33.9 10.5 2.4 461 14.5 3.1

3.7 2.4 11.5 6.4 60.0 14.5 4.9 0.4 0.0 156 6.8 3.1

AG14 1.8 2.6 16.1 4.3 7.1 11.1 15.3 16.1 27.5 740 62.4 2.7

3.7 4.5 38.1 19.2 38.2 0.0 0.0 0.0 0.0 64 14.7 1.55.5 0.9 2.7 1.3 2.7 24.8 58.1 9.5 0.0 595 2.1 1.2
15

AG15 1.8 1.0 3.5 5.2 26.4 27.5 22.3 11.3 2.9 337 4.7 0.9

2.4 2.0 10.2 4.2 3.7 7.3 31.5 22.2 18.8 809 27.7 8.53.0 2.2 11.5 3.9 11.7 18.4 25.0 17.6 9.7 531 26.9 3.24.9 1.5 7.4 2.8 9.3 18.5 29.6 21.7 9.2 680 13.7 2.4

NU01 1.8 2.6 17.2 5.3 15.3 23.8 18.4 8.1 9.3 314 23.9 2.8

4.3 0.4 1.6 1.2 3.3 7.9 49.2 35.7 0.8 832 2.5 1.45.5 3.5 27.6 10.5 44.2 2.9 4.7 4.9 1.7 112 16.6 1.86.7 3.5 22.0 13.1 49.7 7.3 3.4 0.1 1.0 113 13.1 3.5

NU02 1.2 1.3 4.4 2.0 6.2 21.1 48.8 15.5 0.6 672 4.7 2.0

2.4 1.1 4.6 2.2 6.0 11.6 27.9 21.1 25.5 883 7.7 2.0

NU04 1.8 3.8 24.0 12.9 49.7 6.0 2.2 0.5 0.8 111 16.0 3.1NU06 1.8 3.8 16.5 6.6 6.5 11.9 23.4 15.8 15.3 575 54.1 1.7

4.3 2.0 9.2 5.6 6.6 8.5 29.8 31.4 6.9 787 23.1 5.67.9 1.4 4.7 3.5 33.5 54.1 2.9 0.0 0.0 249 2.8 1.6

NU08 1.8 1.5 9.8 3.1 3.2 6.7 25.0 34.9 14.0 929 28.5 7.7

3.7 0.7 4.4 2.1 2.4 10.1 30.4 30.8 19.1 948 4.0 1.45.5 1.1 6.5 2.8 3.1 9.4 28.0 32.0 17.1 940 13.1 4.3

NU09 0.6 3.4 23.1 13.2 18.3 10.4 11.9 4.1 15.7 200 16.0 0.6

3.7 1.2 5.8 2.3 7.0 38.1 37.9 6.9 0.8 466 4.8 2.0

NU11 3.7 0.7 3.3 1.3 2.4 6.5 45.9 39.3 0.5 864 2.5 1.4

6.1 0.5 1.8 0.7 1.6 3.4 35.7 53.6 2.7 1010 2.0 1.1

NU12 1.8 0.8 7.6 2.5 8.5 27.1 34.0 18.7 0.7 541 9.4 2.3NU19 1.8 3.5 24.8 3.8 46.2 12.3 1.9 7.5 0.0 156 25.7 3.2NU21a 3.0 1.4 6.2 3.0 3.8 8.8 52.1 23.4 1.3 724 10.0 5.0NU-22 2.4 3.1 26.3 4.1 55.4 9.3 1.7 0.0 0.0 135 19.1 2.3NU23 1.2 5.3 27.1 3.7 29.5 18.9 4.1 10.1 0.5 177 38.0 1.1

Site name

Sample

depth1

(m BLS)

Percent (by weight) of sample in size range

Clay

(<2μm)

Silt

(2-50 μm)

Very fine 

sand

(50-100 μm)

Fine sand

(100-

250 μm)

Medium 

sand

(250-

500 μm)

Coarse 

sand

(500-

1,000 μm)

Very coarse 

sand

(1,000-

2,000 μm)

Gravel

(>2,000 μm)

2d50

(μm) 3Cu 4Cg

Table 4. Particle-size distribution in samples from unsaturated-zone sampling sites, southern New Jersey--Continued
16

NU24 1.2 1.7 12.7 2.2 20.5 24.7 21.6 6.8 9.9 327 20.2 3.5

3.0 1.3 6.2 2.4 13.6 10.6 51.1 14.6 0.0 668 7.9 2.0

NU27 1.2 1.1 7.0 4.0 17.5 18.2 27.5 23.2 1.2 541 10.3 1.2NU29 1.8 1.6 7.6 4.7 14.7 28.6 27.9 5.5 9.2 420 9.5 2.1OU02 0.6 2.4 17.3 5.1 6.7 21.8 24.8 10.2 11.8 449 33.3 4.5

1.8 3.1 23.7 0.7 0.0 0.8 37.9 17.0 16.7 753 78.5 30.83.0 2.0 14.6 6.9 5.3 7.6 34.5 26.7 2.4 690 33.6 4.15.5 1.4 8.0 2.9 2.8 8.8 36.3 32.9 6.9 822 17.8 6.8

OU03 1.2 2.1 18.2 9.0 19.7 43.1 8.0 0.0 0.0 250 14.1 1.8

3.0 5.5 44.9 8.2 15.7 19.6 5.6 0.5 0.0 48 27.8 1.04.3 4.0 18.3 6.7 22.1 41.4 5.2 0.8 1.6 230 28.0 3.6

OU04 1.8 1.5 7.6 2.7 4.7 12.3 30.5 27.6 13.1 786 15.8 4.6

2.4 1.1 5.1 2.4 5.6 17.6 45.8 22.3 0.0 668 5.9 2.43.7 6.4 13.0 1.9 5.9 10.1 26.0 34.6 2.0 752 225.3 25.0

OU05 1.2 0.8 1.6 1.3 19.6 48.7 26.4 1.6 0.0 349 2.4 1.0OU06 1.2 1.4 11.0 4.6 5.7 10.0 19.8 11.4 36.2 870 36.1 4.0

2.4 10.7 47.0 15.5 26.8 0.0 0.0 0.0 0.0 37 26.0 2.5

OU07 0.6 2.2 10.7 2.6 13.3 16.8 18.8 10.1 25.2 574 31.5 3.2

2.4 3.9 27.3 4.7 42.4 12.7 7.1 1.9 0.0 151 25.1 1.52.4 rep 3.6 22.1 4.0 40.5 14.5 8.5 6.4 0.2 171 24.8 5.75.5 8.0 42.8 4.0 33.0 8.1 4.1 0.0 0.0 44 42.0 0.5

OU08 1.8 3.2 30.9 21.9 25.5 10.5 6.4 0.9 0.7 80 10.3 1.7OU10 1.2 0.8 3.9 1.6 3.5 14.8 39.6 28.5 7.2 786 3.7 1.5

3.0 2.2 11.7 4.4 6.1 10.5 40.3 22.0 2.0 664 28.3 7.63.7 1.8 8.7 3.6 4.6 7.4 18.3 12.7 42.8 1370 56.5 3.4

OU11 3.0 5.2 22.0 7.1 27.0 22.8 13.1 1.3 0.8 161 44.4 3.8OU13 1.2 5.6 15.8 10.7 56.5 8.9 2.5 0.0 0.0 124 15.8 5.9

1.2 rep 6.7 15.2 9.4 52.1 10.8 5.1 0.6 0.0 129 25.2 8.5

Site name

Sample

depth1

(m BLS)

Percent (by weight) of sample in size range

Clay

(<2μm)

Silt

(2-50 μm)

Very fine 

sand

(50-100 μm)

Fine sand

(100-

250 μm)

Medium 

sand

(250-

500 μm)

Coarse 

sand

(500-

1,000 μm)

Very coarse 

sand

(1,000-

2,000 μm)

Gravel

(>2,000 μm)

2d50

(μm) 3Cu 4Cg

Table 4. Particle-size distribution in samples from unsaturated-zone sampling sites, southern New Jersey--Continued
17

1 The depth reported is the depth of the bottom of the core sample from which the 30-cm3 sample was collected.

The sample is assumed to be representative of the layer (see table 3) from which it was taken.

2 Grain-size diameter of 50 percent of the sample (by weight) is less than d50.3 Cu = d60/d10 is the uniformity index. If Cu is less than 2, then the sediment is considered uniform. 4 Cg = d302 /(d60d10) is the coefficient of gradation: the higher the value, the more graded the sample (the wider the distribution of particle sizes).

OU14 1.2 0.7 2.7 2.3 13.7 15.4 22.3 21.9 20.8 786 7.4 1.1

2.4 2.5 9.0 4.1 56.4 25.1 3.0 0.0 0.0 183 6.4 3.3

OU15 2.4 2.8 12.3 3.5 5.5 12.8 29.2 27.5 6.5 693 44.5 8.7

3.7 3.0 10.9 3.0 7.8 12.5 17.5 12.7 32.7 790 66.3 4.35.5 1.4 7.3 2.8 12.3 7.6 19.9 22.6 26.2 921 18.1 2.4

UN01 5.5 1.7 5.8 2.3 6.6 20.0 36.9 19.8 6.7 638 7.5 2.4UN02 1.8 0.4 1.1 0.7 2.5 16.1 45.8 23.8 9.7 766 2.5 1.1UN03 1.2 0.7 2.9 1.8 6.9 22.4 34.5 7.3 23.4 653 4.0 1.3

2.4 1.1 3.2 5.0 24.1 34.3 30.7 1.6 0.0 340 4.4 1.1

UN05 2.4 3.5 24.4 5.7 16.0 42.4 8.1 0.0 0.0 240 36.3 1.7

3.7 7.6 45.7 6.6 28.3 7.2 3.7 0.8 0.0 36 30.7 0.5

UN06 1.2 0.9 4.3 7.1 16.6 26.8 35.4 8.4 0.6 439 6.9 1.4UN07 1.2 1.1 5.9 3.8 6.0 15.6 39.1 26.6 1.8 685 9.9 3.4

2.4 9.6 51.7 12.0 22.9 3.8 0.0 0.0 0.0 27 23.0 0.9

UN08 1.2 0.6 1.7 1.7 13.0 32.2 43.2 6.6 0.8 495 3.4 1.2UN09 1.2 1.5 7.1 4.4 18.6 30.1 29.4 7.7 1.2 382 7.5 1.6UN11 1.2 1.3 3.4 4.2 54.5 28.0 8.2 0.3 0.0 190 2.3 1.0

2.4 1.7 3.2 5.3 65.1 20.1 4.6 0.0 0.0 172 2.1 1.0

UN12 1.2 0.5 1.1 0.5 2.3 28.3 56.1 8.6 2.4 600 2.1 1.1

Site name

Sample

depth1

(m BLS)

Percent (by weight) of sample in size range

Clay

(<2μm)

Silt

(2-50 μm)

Very fine 

sand

(50-100 μm)

Fine sand

(100-

250 μm)

Medium 

sand

(250-

500 μm)

Coarse 

sand

(500-

1,000 μm)

Very coarse 

sand

(1,000-

2,000 μm)

Gravel

(>2,000 μm)

2d50

(μm) 3Cu 4Cg

Table 4. Particle-size distribution in samples from unsaturated-zone sampling sites, southern New Jersey--Continued
18

Table 5. Input to and pedotransfer function parameters from the Rosetta program for unsaturated-zone sampling sites, southern New Jersey[m BLS, meters below land surface; g/cm3, grams per cubic centimeter; m, meters; cm, centimeters; μm, microns cm/d, centimeters per day; <, less than; 

>, greater than; rep, replicate sample]

Site name

Sample 

depth

(m BLS)

Bulk 

density

(g/cm3)

Input data (percent by weight)1 Pedotransfer function parameters2

Clay

(<2 μm)

Silt

(2-50 μm)

Sand

(>50 μm)

θr

(cm3/cm3)

θs

(cm3/cm3)

α

log10

(1/cm)

n

log10

3Ks

log10

(cm/d)

Ko

log10

(cm/d)

L

(dimensionless)

AG01 0.6 1.9 3.3 16.0 80.7 0.036 0.283 -1.288 0.231 1.578 1.575 -1.110

1.8 1.6 6.0 27.3 66.7 0.034 0.348 -1.382 0.156 1.590 1.385 -1.2493.7 1.6 8.0 33.3 58.7 0.035 0.345 -1.516 0.144 1.440 1.192 -1.171

AG02 1.2 1.6 2.4 11.7 85.8 0.041 0.349 -1.380 0.349 2.236 1.545 -0.867

2.1 1.7 2.2 11.2 86.5 0.041 0.337 -1.377 0.356 2.222 1.548 -0.8724.3 1.7 1.0 5.4 93.7 0.047 0.336 -1.452 0.508 2.681 1.440 -0.8676.1 1.6 0.9 4.1 95.4 0.049 0.357 -1.479 0.561 2.859 1.427 -0.882

AG03 1.2 1.5 1.2 6.5 92.4 0.048 0.378 -1.448 0.498 2.753 1.438 -0.881

2.4 1.7 1.1 4.2 94.6 0.047 0.325 -1.462 0.513 2.684 1.430 -0.8573.7 1.7 3.5 16.0 80.5 0.037 0.318 -1.308 0.242 1.789 1.568 -1.050

AG04 1.8 1.8 4.0 26.6 69.4 0.030 0.296 -1.203 0.139 1.339 1.549 -1.720

3.7 2.0 3.6 20.0 76.4 0.033 0.264 -1.233 0.183 1.282 1.592 -1.305

AG09 1.2 1.7 2.6 19.7 77.6 0.034 0.315 -1.269 0.216 1.705 1.599 -1.122AG10 1.8 1.6 1.9 15.4 82.7 0.039 0.360 -1.351 0.306 2.168 1.605 -0.877

4.3 1.6 1.7 10.4 87.9 0.043 0.366 -1.403 0.399 2.442 1.513 -0.8506.1 1.6 1.1 6.4 92.5 0.047 0.363 -1.449 0.500 2.713 1.433 -0.883

AG11 0.6 1.8 4.4 33.3 62.2 0.028 0.300 -1.244 0.119 1.291 1.463 -2.035

1.8 1.6 1.1 4.3 94.7 0.050 0.370 -1.474 0.548 2.862 1.417 -0.8933.0 1.5 5.3 20.8 73.9 0.038 0.390 -1.396 0.196 1.969 1.486 -0.950

AG12 1.2 1.6 2.2 22.1 75.6 0.033 0.338 -1.290 0.212 1.815 1.593 -1.076

2.4 1.6 0.4 1.8 97.8 0.052 0.366 -1.502 0.620 3.042 1.467 -0.8743.7 1.6 0.7 2.4 96.9 0.050 0.345 -1.490 0.580 2.915 1.430 -0.8734.9 1.4 1.9 7.1 91.0 0.047 0.370 -1.442 0.463 2.633 1.430 -0.875

AG13 1.8 1.4 1.8 9.4 88.7 0.045 0.426 -1.384 0.371 2.666 1.619 -0.794

3.7 1.5 2.4 11.5 86.2 0.043 0.389 -1.394 0.356 2.429 1.551 -0.830
19

AG14 1.8 1.7 2.6 16.1 81.3 0.037 0.325 -1.314 0.265 1.895 1.598 -0.986

3.7 1.7 4.5 38.1 57.5 0.028 0.317 -1.395 0.130 1.404 1.320 -1.5395.5 1.5 0.9 2.7 96.4 0.051 0.376 -1.492 0.589 2.977 1.435 -0.889

AG15 1.8 1.6 1.0 3.5 95.6 0.049 0.351 -1.480 0.558 2.857 1.418 -0.884

2.4 1.6 2.0 10.2 87.8 0.044 0.369 -1.406 0.395 2.444 1.506 -0.8503.0 1.7 2.2 11.5 86.3 0.040 0.320 -1.364 0.341 2.116 1.566 -0.8904.9 1.7 1.5 7.4 91.1 0.045 0.340 -1.427 0.451 2.519 1.464 -0.863

NU01 1.8 1.7 2.6 17.2 80.2 0.036 0.330 -1.309 0.255 1.886 1.601 -0.997

4.3 1.6 0.4 1.6 98.1 0.051 0.348 -1.501 0.608 2.997 1.452 -0.8665.5 1.7 3.5 27.6 68.9 0.030 0.325 -1.276 0.157 1.562 1.511 -1.3866.7 1.5 3.5 22.0 74.6 0.035 0.366 -1.343 0.205 1.908 1.542 -1.015

NU02 1.2 1.5 1.3 4.4 94.3 0.051 0.401 -1.465 0.531 2.907 1.443 -0.877

2.4 1.7 1.1 4.6 94.3 0.047 0.325 -1.458 0.508 2.668 1.437 -0.856

NU04 1.8 1.5 3.8 24.0 72.1 0.034 0.363 -1.352 0.188 1.840 1.502 -1.066NU06 1.8 1.9 3.8 16.5 79.7 0.036 0.282 -1.280 0.214 1.503 1.561 -1.167

4.3 1.7 2.0 9.2 88.7 0.043 0.337 -1.403 0.398 2.351 1.504 -0.8597.9 1.4 1.4 4.7 93.9 0.050 0.406 -1.456 0.517 2.896 1.458 -0.868

NU08 1.8 1.5 1.5 9.8 86.9 0.044 0.374 -1.410 0.419 2.529 1.503 -0.851

3.7 1.5 0.7 4.4 94.9 0.050 0.384 -1.471 0.557 2.921 1.445 -0.8875.5 1.7 1.1 6.5 92.4 0.045 0.336 -1.438 0.482 2.600 1.456 -0.863

NU09 0.6 1.8 3.4 23.1 73.5 0.032 0.302 -1.227 0.168 1.480 1.575 -1.383

3.7 1.4 1.2 5.8 93.0 0.049 0.420 -1.428 0.479 2.875 1.520 -0.839

NU11 3.7 1.5 0.7 3.3 96.0 0.051 0.400 -1.475 0.574 3.007 1.472 -0.876

6.1 1.5 0.5 1.8 97.7 0.052 0.379 -1.502 0.620 3.062 1.473 -0.877

NU12 1.8 1.5 0.8 7.6 91.5 0.046 0.377 -1.434 0.483 2.711 1.463 -0.873NU19 1.8 1.5 3.5 24.8 71.7 0.034 0.369 -1.360 0.186 1.882 1.501 -1.045NU21a 3.0 1.7 1.4 6.2 92.4 0.046 0.340 -1.443 0.481 2.608 1.440 -0.869NU22 2.4 1.5 3.1 26.3 70.5 0.033 0.377 -1.380 0.179 1.937 1.484 -1.025

Site name

Sample 

depth

(m BLS)

Bulk 

density

(g/cm3)

Input data (percent by weight)1 Pedotransfer function parameters2

Clay

(<2 μm)

Silt

(2-50 μm)

Sand

(>50 μm)

θr

(cm3/cm3)

θs

(cm3/cm3)

α

log10

(1/cm)

n

log10

3Ks

log10

(cm/d)

Ko

log10

(cm/d)

L

(dimensionless)

Table 5. Input to and pedotransfer function parameters from the Rosetta program for unsaturated-zone sampling sites, southern New Jersey--Continued
20

NU23 1.2 1.6 5.3 27.1 66.7 0.034 0.354 -1.377 0.156 1.633 1.397 -1.243NU24 1.2 1.4 1.7 12.7 85.7 0.042 0.406 -1.372 0.336 2.485 1.621 -0.813

3.0 1.5 1.3 6.2 92.3 0.048 0.382 -1.450 0.495 2.761 1.434 -0.882

NU27 1.2 1.7 1.1 7.0 91.7 0.045 0.325 -1.425 0.456 2.503 1.479 -0.852NU29 1.8 1.4 1.6 7.6 90.6 0.047 0.426 -1.400 0.413 2.759 1.576 -0.810OU02 0.6 1.8 2.4 17.3 80.2 0.035 0.303 -1.281 0.239 1.724 1.607 -1.069

1.8 1.7 3.1 23.7 73.2 0.032 0.323 -1.263 0.181 1.631 1.563 -1.2503.0 1.7 2.0 14.6 83.4 0.038 0.324 -1.330 0.300 2.003 1.607 -0.9285.5 1.6 1.4 8.0 90.6 0.045 0.363 -1.430 0.457 2.594 1.456 -0.869

OU03 1.2 1.5 2.1 18.2 79.7 0.037 0.365 -1.336 0.262 2.084 1.614 -0.911

3.0 1.9 5.5 44.9 49.6 0.026 0.276 -1.293 0.095 0.992 1.350 -2.8294.3 1.5 4.0 18.3 77.7 0.038 0.391 -1.370 0.228 2.099 1.565 -0.898

OU04 1.8 1.7 1.5 7.6 90.9 0.044 0.331 -1.421 0.442 2.467 1.479 -0.856

2.4 1.4 1.1 5.1 93.8 0.050 0.412 -1.445 0.508 2.903 1.485 -0.8583.7 1.6 6.4 13.0 80.4 0.040 0.322 -1.350 0.221 1.714 1.459 -1.106

OU05 1.2 1.7 0.8 1.6 97.6 0.050 0.333 -1.496 0.582 2.914 1.425 -0.860OU06 1.2 1.9 1.4 11.0 87.6 0.040 0.276 -1.372 0.356 1.954 1.594 -0.863

2.4 1.7 10.7 47.0 42.3 0.036 0.315 -1.732 0.136 0.990 0.892 -0.987

OU07 0.6 1.6 2.2 10.7 86.8 0.043 0.360 -1.398 0.379 2.364 1.520 -0.853

2.4 1.5 3.9 27.3 68.7 0.033 0.372 -1.400 0.172 1.858 1.435 -1.0482.4 rep 1.5 3.6 22.1 74.1 0.035 0.361 -1.336 0.200 1.864 1.535 -1.0485.5 1.3 8.0 42.8 49.3 0.041 0.399 -1.981 0.183 1.812 0.683 -0.039

OU08 1.8 1.1 3.2 30.9 65.9 0.035 0.455 -1.607 0.152 2.368 1.288 -0.551OU10 1.2 1.5 0.8 3.9 95.2 0.050 0.382 -1.477 0.564 2.934 1.437 -0.890

3.0 1.8 2.2 11.7 85.3 0.040 0.308 -1.346 0.313 1.991 1.572 -0.9383.7 1.9 1.8 8.7 89.3 0.042 0.274 -1.405 0.383 2.044 1.548 -0.833

OU11 3.0 1.6 5.2 22.0 72.2 0.037 0.364 -1.361 0.183 1.782 1.470 -1.099

Site name

Sample 

depth

(m BLS)

Bulk 

density

(g/cm3)

Input data (percent by weight)1 Pedotransfer function parameters2

Clay

(<2 μm)

Silt

(2-50 μm)

Sand

(>50 μm)

θr

(cm3/cm3)

θs

(cm3/cm3)

α

log10

(1/cm)

n

log10

3Ks

log10

(cm/d)

Ko

log10

(cm/d)

L

(dimensionless)

Table 5. Input to and pedotransfer function parameters from the Rosetta program for unsaturated-zone sampling sites, southern New Jersey--Continued
21

1Fractions of coarse, medium, and fine sand are provided in table 2 for descriptive purposes; however, only the total sand fraction, along with silt and clay fractions and bulk density, 

was input to the Rosetta program.

2See equations 3, 4, and 5.3The Rosetta program also can be used to estimate the saturated conductivity for the sediment, Ks. Ks is estimated independently from Ko, which is a curve-fitting parameter.

OU13 1.2 1.4 5.6 15.8 78.7 0.042 0.418 -1.401 0.223 2.195 1.552 -0.833

1.2 rep 6.7 15.2 78.1 0.043 0.404 -1.417 0.225 2.087 1.493 -0.862

OU14 1.2 1.7 0.7 2.7 96.4 0.049 0.339 -1.483 0.566 2.874 1.428 -0.871

2.4 1.3 2.5 9.0 88.5 0.046 0.428 -1.392 0.363 2.642 1.603 -0.788

OU15 2.4 1.7 2.8 12.3 84.9 0.040 0.332 -1.362 0.320 2.092 1.561 -0.903

3.7 1.7 3.0 10.9 86.1 0.041 0.313 -1.367 0.324 2.038 1.543 -0.9185.5 1.8 1.4 7.3 91.4 0.044 0.309 -1.419 0.436 2.387 1.502 -0.836

UN01 5.5 1.7 1.7 5.8 92.3 0.046 0.323 -1.439 0.457 2.511 1.447 -0.856UN02 1.8 1.7 0.4 1.1 98.6 0.049 0.319 -1.498 0.590 2.922 1.448 -0.832UN03 1.2 1.7 0.7 2.9 96.3 0.049 0.336 -1.481 0.560 2.847 1.428 -0.867

2.4 1.6 1.1 3.2 95.7 0.049 0.343 -1.481 0.551 2.830 1.413 -0.877

UN05 2.4 1.6 3.5 24.4 72.2 0.033 0.345 -1.313 0.185 1.743 1.524 -1.150

3.7 1.6 7.6 45.7 46.7 0.033 0.324 -1.695 0.144 1.243 0.972 -0.921

UN06 1.2 1.6 0.9 4.3 94.8 0.049 0.360 -1.473 0.549 2.845 1.423 -0.888UN07 1.2 1.5 1.1 5.9 93.0 0.048 0.387 -1.452 0.510 2.816 1.442 -0.881

2.4 1.4 9.6 51.7 38.7 0.042 0.362 -2.078 0.193 1.431 0.511 -0.059

UN08 1.2 1.6 0.6 1.7 97.5 0.051 0.354 -1.500 0.602 2.990 1.438 -0.877UN09 1.2 1.7 1.5 7.1 91.2 0.044 0.320 -1.422 0.438 2.436 1.483 -0.850UN11 1.2 1.4 1.3 3.4 95.3 0.052 0.425 -1.451 0.525 2.982 1.506 -0.845

2.4 1.4 1.7 3.2 95.0 0.052 0.405 -1.477 0.542 2.942 1.431 -0.877

UN12 1.2 1.5 0.5 1.1 98.3 0.053 0.382 -1.508 0.633 3.100 1.485 -0.872

Site name

Sample 

depth

(m BLS)

Bulk 

density

(g/cm3)

Input data (percent by weight)1 Pedotransfer function parameters2

Clay

(<2 μm)

Silt

(2-50 μm)

Sand

(>50 μm)

θr

(cm3/cm3)

θs

(cm3/cm3)

α

log10

(1/cm)

n

log10

3Ks

log10

(cm/d)

Ko

log10

(cm/d)

L

(dimensionless)

Table 5. Input to and pedotransfer function parameters from the Rosetta program for unsaturated-zone sampling sites, southern New Jersey--Continued
22

RECHARGE ESTIMATES

For each site, unsaturated flow was calculated 

from moisture-content data collected when the well 

was installed (table 6). The depth for which flow 

was calculated was selected such that the moisturecontent gradient could be calculated from data 

associated with a single layer. For the 48 sites, the 

average depth for which flow was calculated was 

3.1 m below land surface. The average unsaturated-zone thickness was 4.4 m; therefore, 

although the flow values generally were calculated 

for layers deep in the unsaturated zone, they were 

not calculated precisely at the water table. 

Although the computed flows technically are not 

recharge estimates, they are herein referred to as 

such and collectively are assumed to provide a 

measure of spatial recharge variability. In some 

cases, the calculation of the moisture-content 

gradient was determined to be unreliable and the 

recharge estimate was assumed to equal the 

conductivity. A positive value for recharge corresponds to downward flow to the aquifer; a negative 

value indicates upward water movement.

The median recharge rate (table 6) was 

29.1 cm/yr (27 percent of average annual precipitation). As cited above, estimates of annual 

recharge to the aquifer based on water-budget 

calculations range from 33.1 to 49.3 cm/yr. 

Although there are uncertainties in the calculations 

(discussed below), the median compares favorably 

to the reported range; therefore, this approach to 

scaling recharge and its variability has an appropriate central tendancy. The moisture-content 

measurements were made during summer and fall, 

when potential evapotranspiration is highest. The 

recharge estimates vary considerably across the 

study area (fig. 4). The range from 6.5 to 

74.2 cm/yr contains the middle third of the 

estimates and corresponds to 6 to 68 percent of the 

average annual precipitation rate. Recharge 

estimates for approximately 17 percent of the sites 

were very high--in excess of 250 cm/yr (2.3 times 

the average annual precipitation rate)--whereas at 

the other extreme, about 17 percent of the recharge 

estimates were negative, indicating upward 

movement. The interval 0 < R < 110 cm/yr 

(bounded above by a value approximately equal to 

the average annual precipitation of 109.3 cm/yr) 

contains about 58 percent of the recharge estimates 

(fig. 4 inset).

Uncertainty of Calculations

Calculations of flow in unsaturated porous 

media are inherently uncertain because of the 

nonlinear dependence of K and ψ on moisture 

content and difficulty in measuring these hydraulic 

properties. The use of the Rosetta program introduces additional uncertainty because the data used 

to derive the functional relations are for sediment 

collected elsewhere. To evaluate the application of 

the Rosetta model, six sediment samples (AG02, 

AG12, AG14, AG15, NU01, and NU08) were 

selected for direct measurement of K and ψ and 

recalculation of recharge.

The steady-state centrifuge method (Nimmo 

and others, 1987; Conca and Wright, 1998) was 

used to measure K and ψ for the six samples 

selected. Samples for analysis were obtained by 

subcoring the original 5.1-cm (2-inch) cores to 

obtain an intact sample 4.9 cm long and 3.2 cm in 

diameter. Steady-state unsaturated flow is 

achieved relatively quickly through use of 

centrifugal force to drive flow. If appropriate flow 

rates controlled by a metering pump are chosen, K 

can be determined over a range of moisture 

contents. The measurements start from saturation 

and each step in the sequence produces data for a 

point on the drying curve. For each step, steady 

flow is verified by observing that moisture content 

and flux through the sample are constant. The 

moisture content is determined by weighing the 

sample between runs. The matric potential, ψ,

associated with K and θ at the end of a steady-state 

run was measured with a nonintrusive touch tensiometer; however, measurements of ψ near the field 

moisture content were obtainable only for samples 

AG02 and NU08 because the presence of pebbles 

in samples AG12, AG14, AG15, and NU01 

prohibited the measurement of ψ at values near the 

field moisture content.
23

Table 6. Summary of flow calculations for unsaturated-zone sampling sites, southern New Jersey

[θ, moisture content; K, conductivity; dψ/dz, matric potential gradient; R, recharge; m, meters; BLS, below 

land surface; cm/yr, centimeters per year; --, unreliable moisture content gradient]

1

 R = -q (eq. 2) unless θ < θr in which case R=0 is assumed. R = K is assumed if dψ/dz is unavailable.

Site name

Flow depth 

(m BLS)

Unsaturatedzone 

thickness 

(m) Ratio

θ

(dimensionless)K

(cm/yr)

dψ/dz 

(dimensionless)R1

(cm/yr)

AG01 2.4 4.5 0.54 0.25 56.3 -0.06 59.7

AG02 6.1 6.9 0.89 0.09 102.2 -0.04 106.1

AG03 2.4 3.6 0.68 0.08 67.4 -0.16 77.9

AG04 2.4 3.9 0.63 0.16 19.4 0.13 16.8

AG09 1.2 2.0 0.61 0.11 14.9 1.88 -13.0

AG10 4.3 6.4 0.67 0.13 162.3 -0.09 176.9

AG11 1.8 2.7 0.67 0.07 23.2 -0.37 31.6

AG12 6.1 8.7 0.70 0.06 3.3 0.50 1.7

AG13 2.4 3.4 0.72 0.06 1.3 -2.37 4.3

AG14 5.5 7.6 0.72 0.04 0.0 -- 0.0

AG15 4.9 5.8 0.84 0.07 9.5 0.52 5.6

NU01 6.7 8.5 0.79 0.13 11.7 0.44 5.6

NU02 1.8 2.3 0.80 0.12 281.6 -- 281.6

NU04 1.2 1.9 0.63 0.22 53.2 -- 53.2

NU06 7.6 13.1 0.58 0.06 1.7 -1.72 4.7

NU08 5.5 6.2 0.88 0.12 253.5 0.05 240.9

NU09 4.4 6.1 0.73 0.08 30.7 -- 30.7

NU11 5.5 6.7 0.82 0.05 0.0 -- 0.0

NU12 1.8 2.5 0.74 0.06 8.6 -- 8.6

NU19 1.8 3.7 0.50 0.19 19.2 -0.42 27.3

NU21a 3.0 4.3 0.71 0.05 0.4 -- 0.4

NU22 2.4 3.0 0.81 0.16 6.1 4.05 -18.5

NU23 1.2 1.5 0.83 0.25 54.2 1.21 -11.5

NU24 2.4 4.7 0.52 0.17 689.5 0.24 526.8

NU27 0.6 1.3 0.47 0.15 395.9 -0.21 478.9

NU29 1.8 2.4 0.76 0.11 79.1 0.65 27.5

OU02 7.9 12.3 0.64 0.14 298.7 0.01 297.1

OU03 3.7 5.4 0.68 0.23 554.1 -0.14 634.4

OU04 3.0 4.7 0.65 0.14 36.3 -- 36.3

OU05 1.8 2.8 0.65 0.02 0.0 -- 0.0

OU06 1.8 3.5 0.53 0.09 0.0 -65.04 0.5

OU07 3.0 4.9 0.62 0.19 54.0 -0.30 73.1

OU08 1.2 2.1 0.59 0.10 0.0 225.01 -1.8

OU10 4.3 6.4 0.67 0.19 1753.1 -0.05 1,835.0

OU11 1.8 2.8 0.66 0.12 1.6 -- 1.6

OU13 1.2 2.1 0.58 0.21 75.4 -- 75.4

OU14 1.8 3.1 0.60 0.09 133.5 -0.13 151.1

OU15 5.5 8.1 0.68 0.13 279.6 -0.18 330.8

UN01 6.7 7.8 0.86 0.08 30.4 -0.20 36.5

UN02 3.0 4.3 0.71 0.05 0.0 -- 0.0

UN03 1.2 2.0 0.61 0.06 10.0 -0.68 16.7

UN05 1.8 2.5 0.73 0.19 20.4 0.08 18.7

UN06 1.2 1.7 0.71 0.18 1054.9 0.23 812.1

UN07 3.7 4.6 0.79 0.30 27.7 0.30 19.4

UN08 1.2 2.2 0.55 0.06 7.7 0.03 7.4

UN09 0.6 2.2 0.27 0.10 77.9 -- 77.9

UN11 3.0 4.7 0.65 0.07 24.1 -0.34 32.3

UN12 0.6 1.5 0.41 0.09 148.6 -- 148.6

Median 2.4 3.8 0.67 0.11 29.06 29.14
24

Figure 4. Distribution of (a) all recharge estimates and (b) recharge estimates 

between 0 and 110 centimeters per year for unsaturated-zone sampling sites, 

Glassboro study area.

0

0.05

0.10

0.15

0.20

0.25

0 < R < 15

15 < R < 30

30 < R < 45

45 < R < 60

60 < R < 75

75 < R < 90

90 < R < 110

A

B

0

0.1

0.2

0.3

0.4

0.5

< 0 (evapotranspiration)

0 < R < 50

50 < R < 100

100 < R < 150

150 < R < 200

200 < R < 250

R > 250

FRACTION OF DATA IN INTERVAL

Recharge (R), in centimeters per year

FRACTION OF DATA IN INTERVAL

Recharge (R), in centimeters per year
25

The flow calculations are summarized in table 

7 and figure 5. Linear interpolation was used to 

obtain values of K and ψ for field moisture 

contents between experimental points. Experimental values for ψ near the field moisture content 

were not attainable at some sites; in these cases, the 

conductivity values were plotted. The estimates 

vary considerably; in particular, the Rosetta-based 

estimates for sites AG02 and NU08 were much 

higher than the estimates based on measured 

values. The estimates, however, compare 

favorably in that both indicated relatively low 

recharge for four sites (AG12, (AG14, AG15, and 

NU01) and relatively high recharge for two sites 

(AG02 and NU08). Because of the uncertainty in 

flow calculations, the recharge estimates for 48 

sites based on the Rosetta model provide only a 

scaling of recharge that allows site estimates to be 

ranked only into broad categories such as low, 

moderate, and high recharge.

Flow Regime

Unsaturated flow is gravity-dominated if

 , (6)

where is a specified relative error. If flow is 

gravity-dominated, then it can be approximated by 

conductivity because matric-potential gradients are 

negligible. For all sites where R and K were calculated in sand, flow is gravity-dominated if 

R > 100 cm/yr (fig. 6). The inset in figure 6 is 

rescaled to illustrate that matric forces must be 

considered in the flow calculations for the sites for 

which R < 100 cm/yr.

For the sites for which both R and K were 

calculated in sandy loams, matric forces are significant for the entire range of R (fig. 7). In particular, 

matric forces dominate gravity where the net 

movement of water is upward (R < 0). Upward 

water movement was not observed at any of the 

sites where the recharge calculation was made for 

sands (fig. 6). This finding indicates that net water 

loss from the aquifer can occur only at sites where 

the water table is located in sediment that is finer 

than sand.

Mapping Spatial Trends

If discernible, spatial trends in recharge at a 

watershed scale could be used in conjunction with 

land-use information to identify areas susceptible 

to contamination. Because the recharge estimates 

are categorical in nature, it is appropriate to 

consider maps based on transformed recharge 

estimates. If the value 0 is assigned to an estimated 

recharge less than the median (29.1 cm/yr) and the 

value 1 is assigned to an estimated recharge greater 

than the median, then the map showing the probability of exceeding the median recharge (fig. 8) is 

obtained by kriging the indicator transform.

The area of lower expected recharge plotted in 

the southwestern part of the study area is mostly 

agricultural land within the Cohansey River Basin. 

Annual average recharge in this basin has been 

estimated to be 37.1 cm/yr (Charles and others, 

2001), which is the 25th percentile within the range 

(33.1–49.3 cm/yr) of reported recharge estimates 

based on water-budget studies. This finding is 

consistent with the recharge calculations, as the 

area is one where recharge can be expected to be 

R K– less than the regional median (fig. 8).

R ------------- < δ

δ
26

Table 7. Flow calculations for six selected unsaturated-zone sampling sites, southern New Jersey

[m BLS, meters below land surface; θ, moisture content; K, conductivity; dψ/dz, matric potential gradient; q, flow; 

cm/yr, centimeters per year; --, measurement not possible]

1Measurement of ψ not possible near field moisture content for samples AG14, AG15, NU01, and NU08; 

therefore, q is assumed to equal K for comparison purposes.

Figure 5. Relation of flow estimates based on measured hydraulic parameters to flow based on 

estimated hydraulic parameters for six selected unsaturated-zone sampling sites, Glassboro study area.

Site name

Depth

(m BLS)

θ

(dimensionless)

Flow calculation

With Rosetta program With measured values1

K

(cm/yr)

dψ/dz 

(dimensionless)q

(cm/yr)

K

(cm/yr)

dψ/dz 

(dimensionless)q

(cm/yr)

AG14 5.5 0.04 0.0 -- 0.0 0.2 -- 0.2

AG12 6.1 0.06 3.3 0.5 1.7 9.4 0.12 8.3

AG15 4.9 0.07 11.7 0.52 5.6 1.8 -- 1.8

NU01 6.7 0.13 10.0 0.44 5.6 0.0 -- 0.0

AG02 6.1 0.09 102.2 -0.04 106.1 35.7 -0.40 50.0

NU08 5.5 0.12 253.5 0.05 240.9 39.2 -- 39.2

0

10

20

30

40

50

60

0 50 100 150 200 250 300

FLOW ESTIMATE BASED ON MEASURED

HYDRAULIC PARAMETERS,

IN CENTIMETERS PER YEAR

FLOW BASED ON ESTIMATED HYDRAULIC PARAMETERS,

IN CENTIMETERS PER YEAR
27

Figure 6. Relation of flow (R) to conductivity (K) for (a) all sands and 

(b) sands in which flow was less than 100 centimeters per year.

0

10

20

30

40

50

60

70

80

90

0 10 20 30 40 50 60 70 80 90

B

0

100

200

300

400

500

600

0 100 200 300 400 500 600

1:1 line

25-percent error bound

K, IN CENTIMETERS PER YEAR

R, IN CENTIMETERS PER YEAR

A

K, IN CENTIMETERS PER YEAR

R, IN CENTIMETERS PER YEAR
28

Figure 7. Relation of flow (R) to conductivity (K) for sandy loams.

-50

-30

-10

10

30

50

70

0 10 20 30 40 50 60 70 80

K, IN CENTIMETERS PER YEAR

R, IN CENTIMETERS PER YEAR

1:1 line

25-percent error bound
29

Figure 8. Probability of recharge exceeding 29.2 centimeters per year in the Glassboro study area.

0 5 MILES

0 5 KILOMETERS

39¡

30’

39¡

45’

75¡

75¡15’

Study-area boundary

Monitoring site

EXPLANATION

PROBABILITY

Less than 0.5

Greater than 0.5
30

SUMMARY AND CONCLUSIONS

Traditional water-budget methods can be used 

to obtain average values of recharge for a 

watershed, but information on variations in 

recharge over the watershed is needed to determine 

chemical loading to ground water. One approach 

for estimating recharge variability is to collect 

samples of unsaturated-zone sediment at sites 

throughout the watershed, estimate hydraulic 

properties, and calculate unsaturated flow. This 

method was applied by sampling the unsaturated 

zone at 48 sites over an area of approximately 

930 km2 in southern New Jersey during the 

summer and fall of 1996.

Unsaturated flow at the 48 sites was calculated at a median depth below land surface of 0.67 

times the unsaturated-zone thickness. The calculated flow was assumed to equal recharge. The 

median recharge for the 48 sites was 29.1 cm/yr 

(27 percent of the average annual precipitation 

rate); this value compares favorably to estimates of 

annual recharge to the aquifer based on waterbudget studies, which range from 33.1 to 

49.3 cm/yr. The moisture content was measured 

during the summer and fall, when recharge would 

be expected to be lower than its annual average 

because of greater-than-average evapotranspiration.

Estimates of recharge varied across the study 

area, with the middle third of the values falling 

between 6.5 and 74.2 cm/yr (6 to 68 percent of the 

annual precipitation rate). The flow calculations, 

however, are uncertain as a result of the nonlinearity of conductivity and matric-potential 

functions and the application of Rosetta-derived 

pedotransfer functions to these particular 

sediments. The overall method, however, does 

provide a scaling of recharge variability that allows 

the sites to be ranked in broad categories, such as 

low, moderate, and high recharge.

Despite the general perception that unsaturated flow in a humid climate such as that of 

southern New Jersey is gravity-driven, matric 

forces were found to be important in the movement 

of water through the unsaturated zone at about 70 

percent of the sites for which R < 100 cm/yr. At 

15 percent of the sites, matric forces caused water 

to move upward (R < 0), but only in fine-grained 

sediments such as sandy loams (not in sand).

A map developed by kriging the indicator 

transform was used to delineate parts of the study 

area where recharge was more likely or less likely 

to exceed the median. The map was consistent in 

identifying a largely agricultural part of the study 

area where recharge previously was found to be 

low relative to recharge in other basins for which 

water budgets had been developed.

The method used here provides data needed to 

define the role of unsaturated-zone geology in 

recharge variability. The study is limited, however, 

because moisture content was determined only 

during a single season. Repeated measurements of 

moisture content throughout the year would allow 

determination of the nature of spatial variability 

during the other seasons.

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