Prepared in Cooperation with the 

Barnegat Bay Partnership

Nutrient Concentrations in Surface Water and Groundwater, 

and Nitrate Source Identification Using Stable Isotope 

Analysis, in the Barnegat Bay-Little Egg Harbor Watershed, 

New Jersey, 2010–11

U.S. Department of the Interior

U.S. Geological Survey

Scientific Investigations Report 2012–5287
Cover: Photo of tea-colored water of Westecunk Creek, Ocean County, New Jersey. (Photograph by Robert Stern)
Nutrient Concentrations in Surface Water 

and Groundwater, and Nitrate Source Identification Using Stable Isotope Analysis, in 

the Barnegat Bay-Little Egg Harbor Watershed, New Jersey, 2010–11

By Christine M. Wieben, Ronald J. Baker, and Robert S. Nicholson 

Prepared in cooperation with the 

Barnegat Bay Partnership

Scientific Investigations Report 2012–5287

U.S. Department of the Interior

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

KEN SALAZAR, Secretary

U.S. Geological Survey

Suzette M. Kimball, Acting Director

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

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reproduce any copyrighted materials contained within this report.

Suggested citation:

Wieben, C.M., Baker, R.J., and Nicholson, R.S., 2013, Nutrient concentrations in surface water and groundwater, 

and nitrate source identification using stable isotope analysis, in the Barnegat Bay-Little Egg Harbor watershed, 

New Jersey, 2010–11: U.S. Geological Survey Scientific Investigations Report 2012–5287, 44 p.
iii

Contents

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

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

Purpose and Scope ..............................................................................................................................5

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

Previous Studies ...................................................................................................................................7

Methods...........................................................................................................................................................9

Streamflow Measurements ................................................................................................................9

Water-Quality-Data Collection ...........................................................................................................9

Surface Water............................................................................................................................10

Groundwater...............................................................................................................................11

Quality Assurance and Quality Control ...........................................................................................13

Water Quality Under Various Conditions in Surface Water and Groundwater.................................13

Surface Water.....................................................................................................................................13

Continuous Water-Quality Data ..............................................................................................13

Temperature ......................................................................................................................13

Specific Conductance......................................................................................................13

pH.........................................................................................................................................16

Dissolved Oxygen .............................................................................................................16

Turbidity..............................................................................................................................16

Nitrogen.......................................................................................................................................17

Total Nitrogen....................................................................................................................17

Nitrate plus Nitrite ............................................................................................................22

Ammonia.............................................................................................................................23

Organic Nitrogen ..............................................................................................................23

Phosphorus.................................................................................................................................24

Dissolved Solids.........................................................................................................................24

Groundwater........................................................................................................................................24

Nitrogen.......................................................................................................................................24

Phosphorus.................................................................................................................................24

Stable Isotope Analysis .....................................................................................................................25

Surface Water............................................................................................................................25

Groundwater...............................................................................................................................33

Summary and Conclusions.........................................................................................................................34

Acknowledgments.......................................................................................................................................36

References Cited..........................................................................................................................................36

Appendix 1. Summary statistics of continuous water-quality data, Barnegat Bay-Little Egg 

Harbor watershed, 2010 ................................................................................................................40
iv

Figures

1. Map showing Barnegat Bay-Little Egg Harbor estuary and watershed with locations 

of selected surface-water-quality stations..............................................................................2

2. Graph showing typical ranges of δ15N and δ18O values of nitrate in water derived 

from atmospheric, fertilizer, soil, and septic and animal-waste sources ...........................4

3. Map showing land use in the Barnegat Bay-Little Egg Harbor watershed, 2007..............6

4. Map showing locations of, and concentrations of nitrate plus nitrite in, five wells 

sampled within the Barnegat Bay-Little Egg Harbor watershed, 2010–11........................12

5. Hydrographs showing continuous water-quality-monitoring data recorded at waterquality stations in the Barnegat Bay-Little Egg Harbor watershed during the 

nongrowing-season sampling event, March 2010 ................................................................14

6. Hydrographs showing continuous water-quality-monitoring data recorded at waterquality stations in the Barnegat Bay-Little Egg Harbor watershed during the 

growing-season sampling event, September–October 2010 ..............................................15

7. Graphs showing streamflow hydrographs and concentrations of total nitrogen, 

nitrate plus nitrite, organic nitrogen, and ammonia in surface-water samples 

collected at water-quality stations in the Barnegat Bay-Little Egg Harbor watershed during the nongrowing-season sampling event, March 2010 ...................................20

8. Graphs showing streamflow hydrographs and concentrations of total nitrogen, 

nitrate plus nitrite, organic nitrogen, and ammonia in surface-water samples 

collected at water-quality stations in the Barnegat Bay-Little Egg Harbor watershed during the growing-season sampling event, September–October 2010 .................21

 9. Graph showing δ15N and δ18O compositions of nitrate in surface-water samples collected at water-quality stations in the Barnegat Bay-Little Egg Harbor watershed, 

March–October 2010, during A, all flow conditions and B, base-flow conditions ..........27

10. Graph showing δ15N compositions of nitrate in surface-water samples collected 

during base flow, first flush, and peak flow at water-quality stations in the Barnegat 

Bay-Little Egg Harbor watershed during the A, nongrowing-season sampling event, 

March 2010, and B, growing-season sampling event, September–October 2010...........28

11. Graph showing δ18O compositions of nitrate in surface-water samples collected 

during base flow, first flush, and peak flow at water-quality stations in the Barnegat 

Bay-Little Egg Harbor watershed during the A, nongrowing-season sampling event, 

March 2010, and B, growing-season sampling event, September–October 2010...........29

12. Graph showing δ15N and δ18O compositions of nitrate in water at water-quality 

stations in the Barnegat Bay-Little Egg Harbor watershed, averaged by sampling 

event and flow condition ...........................................................................................................30

13. Graphs showing A, δ18O values and B, δ15N values in relation to percent urban land 

use (residential plus nonresidential, shown in parentheses) in subbasins for waterquality stations in the Barnegat Bay-Little Egg Harbor watershed....................................31

14. Graphs showing relation between concentrations of water-quality constituents and 

isotope ratios at water-quality stations in the Barnegat Bay-Little Egg Harbor watershed: A, chloride concentration and δ15N value, B, chloride concentration and δ18O 

value, C, potassium concentration and δ15N value, and D, potassium concentration 

and δ18O value..............................................................................................................................32

15. Graph showing δ15N and δ18O compositions of nitrate in groundwater samples 

collected from shallow wells in the Barnegat Bay-Little Egg Harbor watershed, 

2010–11 .........................................................................................................................................33
v

Tables

1. Land-use distributions for selected subbasins of the Barnegat Bay-Little Egg Harbor 

watershed, 2007 ............................................................................................................................7

2. Information for selected streamflow-gaging stations in the Barnegat Bay-Little Egg 

Harbor watershed.......................................................................................................................10

3. Minimum detection and reporting levels for selected water-quality constituents.........10

4. Analytical precision of sensors used in a continuous water-quality monitor (sonde) 

for groundwater and surface-water sampling at stations in the Barnegat Bay-Little 

Egg Harbor watershed, 2010–11...............................................................................................11

5. Concentrations of nutrient species in samples collected from five streams in the 

Barnegat Bay-Little Egg Harbor watershed, 2010.................................................................18

6. Median nutrient concentrations for streams in the Barnegat Bay-Little Egg Harbor 

watershed measured in samples collected for this study (2010), and determined 

from historical water-quality data for 1980–2009 ..................................................................23

7. Concentrations of nutrient species, and values of nitrogen and oxygen stable 

isotope ratios in nitrate, in samples collected from five wells screened in the 

Kirkwood-Cohansey aquifer system in the Barnegat Bay-Little Egg Harbor watershed, 2010–11 ..............................................................................................................................25

8. Values of nitrogen and oxygen stable isotope ratios in nitrate in samples collected 

from five streams in the Barnegat Bay-Little Egg Harbor watershed, 2010......................26

Conversion Factors

Multiply By To obtain

Length

meter (m) 3.281 foot (ft)

kilometer (km) 0.6214 mile (mi)

Area

square kilometer (km2) 247.1 acre

square kilometer (km2) 0.3861 square mile (mi2)

Flow rate

cubic meter per second (m3/s) 35.31 cubic foot per second (ft3/s)

cubic meter per second (m3/s) 22.83 million gallons per day (Mgal/d)

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

°F=(1.8×°C)+32

Specific conductance is given in microsiemens per centimeter at 25 degrees Celsius (μS/cm at 25 °C).

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

Nutrient Concentrations in Surface Water and Groundwater, and Nitrate Source Identification Using Stable 

Isotope Analysis, in the Barnegat Bay-Little Egg Harbor 

Watershed, New Jersey, 2010–11

By Christine M. Wieben, Ronald J. Baker, and Robert S. Nicholson

Abstract

Five streams in the Barnegat Bay-Little Egg Harbor (BBLEH) watershed in southern New Jersey were sampled for 

nutrient concentrations and stable isotope composition under 

base-flow and stormflow conditions, and during the growing 

and nongrowing seasons, to help quantify and identify sources 

of nutrient loading. Samples were analyzed for concentrations 

of total nitrogen, ammonia, nitrate plus nitrite, organic nitrogen, total phosphorus, and orthophosphate, and for nitrogen 

and oxygen stable isotope ratios.

Concentrations of total nitrogen in the five streams 

appear to be related to land use, such that streams in subbasins 

characterized by extensive urban development (and historical agricultural land use)—North Branch Metedeconk and 

Toms Rivers—exhibited the highest total nitrogen concentrations (0.84–1.36 milligrams per liter (mg/L) in base flow). 

Base-flow total nitrogen concentrations in these two streams 

were dominated by nitrate; nitrate concentrations decreased 

during storm events as a result of dilution by storm runoff. 

The two streams in subbasins with the least development—

Cedar Creek and Westecunk Creek—exhibited the lowest 

total nitrogen concentrations (0.16–0.26 mg/L in base flow), 

with organic nitrogen as the dominant species in both base 

flow and stormflow. A large proportion of these subbasins 

lies within forested parts of the Pinelands Area, indicating the 

likelihood of natural inputs of organic nitrogen to the streams 

that increase during periods of storm runoff. Base-flow 

total nitrogen concentrations in Mill Creek, in a moderately 

developed basin, were 0.43 to 0.62 mg/L and were dominated 

by ammonia, likely associated with leachate from a landfill 

located upstream. Total phosphorus and orthophosphate were 

not found at detectable concentrations in most of the surfacewater samples, with the exception of samples collected from 

the North Branch Metedeconk River, where concentrations 

ranged from 0.02 to 0.09 mg/L for total phosphorus and 0.008 

to 0.011 mg/L for orthophosphate.

Measurements of nitrogen and oxygen stable isotope 

ratios of nitrate in surface-water samples revealed that a 

mixture of multiple subsurface sources, which may include 

some combination of animal and septic waste, soil nitrogen, 

and commercial fertilizers, likely contribute to the base-flow 

nitrogen load. The results also indicate that atmospheric 

deposition is not a predominant source of nitrogen transported 

to the BB-LEH estuary from the watershed, although the 

contribution of nitrate from the atmosphere increases during 

stormflow. Atmospheric deposition of nitrate has a greater 

influence in the less developed subbasins within the BB-LEH 

watershed, likely because few other major sources of nitrogen 

(animal and septic waste, fertilizers) are present in the less 

developed subbasins. Atmospheric sources appear to contribute proportionally less of the overall nitrate as development 

increases within the BB-LEH watershed.

Groundwater samples collected from five wells located 

within the BB-LEH watershed and screened in the unconfined Kirkwood-Cohansey aquifer system were analyzed for 

nutrient and stable isotope composition. Concentrations of 

nitrate ranged from not detected to 3.63 mg/L, with the higher 

concentrations occurring in the highly developed northern 

portion of the watershed, indicating the likelihood of anthropogenic sources of nitrogen. Isotope data for the two wells 

with the highest nitrate concentrations are more consistent 

with fertilizer sources than with animal or septic waste. Total 

phosphorus was not detected in any of the wells sampled, and 

orthophosphate was either not detected or measured at very 

low concentrations (0.005–0.009 mg/L) in each of the wells 

sampled. 

Introduction

The Barnegat Bay-Little Egg Harbor (BB-LEH) estuary 

is a shallow, lagoonal-type estuary located along the central 

coast of New Jersey, separated from the Atlantic Ocean by 

a narrow complex of barrier islands (Kennish, 2001). The 

estuary is composed of Barnegat Bay, Manahawkin Bay, and 

Little Egg Harbor (fig. 1). Historically, the estuary has been 

a vital economic and recreational resource, supporting both 
2 Nutrient Concentrations and Nitrate Source Identification, Barnegat Bay-Little Egg Harbor Watershed, NJ, 2010–11

0 6 12 KILOMETERS

0 4 8 MILES

EXPLANATION

Watershed of water-quality

monitoring station

Pinelands area

U.S. Geological Survey

surface-water-quality

monitoring station and number

NEW

JERSEY

01408120

Barnegat Bay-Little 

Egg Harbor watershed

B a r n e g a t

Little E g g

H a r b o r

Manahawkin

Bay

B a y

Westecunk

Creek

01409281

Mill Creek

01409150

Cedar Creek

01408950

01408508

Toms River

01408505

North Branch

Metedeconk River

01408120

74°20' 74°00’

40°

00’

39°

40'

Base from U.S. Geological Survey digital line graph files, 1:24,000

Figure 1. Barnegat Bay-Little Egg Harbor estuary and watershed with locations of selected surface-water-quality stations.
Introduction 3

commercial and recreational fish and shellfish industries, as 

well as boating and tourism. The estuary and adjacent lands 

offer a variety of ecologically important habitats including 

sand beaches and dunes, salt marshes, submerged aquatic 

vegetation beds, shellfish beds, and waterfowl nesting grounds 

(Barnegat Bay National Estuary Program, 2002).

Physical characteristics of the estuary, including its shallow depth and limited outlets for exchange with ocean water 

(poor flushing), render it particularly susceptible to the effects 

of nutrient loading and, over the last few decades, the ecological health of the estuary has deteriorated (Kennish and others, 

2007). In particular, the estuary has experienced increases in 

macroalgal growth, harmful algal blooms, and turbidity, as 

well as oxygen depletion, declines in harvestable fisheries, and 

changes in species composition, including decreases in the 

biomass and size of seagrass beds (Kennish and others, 2007). 

The estuary has been classified as highly eutrophic based on 

the National Oceanographic and Atmospheric Administration 

National Estuarine Eutrophication Assessment (Bricker and 

others, 1999; Bricker and others, 2007). 

Nixon (1995) defined eutrophication as “an increase in 

the rate of supply of organic matter to an ecosystem,” most 

commonly caused by nutrient enrichment. According to 

Liebig’s Law of the Minimum, plant growth is limited by the 

availability of the scarcest resource, not by the total amount 

of resources available (von Liebig, 1855). Phosphorus is 

more often the limiting nutrient for plant growth in freshwater 

systems, whereas nitrogen is more often the limiting nutrient 

in estuaries and coastal ecosystems (Hecky and Kilham, 1988; 

Howarth, 1988). In the case of the BB-LEH estuary, nitrogen 

is the primary limiting nutrient for plant growth, but secondary limitation by phosphorus occurs during periods of high 

nitrogen loading (Seitzinger and others, 2001). As a result, 

eutrophication can be controlled by restricting the loading of 

the primary limiting nutrient (Smith and Bennett, 1999), either 

by reducing nitrogen inputs to the estuary or by increasing 

the flushing rate of water in the estuary in order to decrease 

the frequency and severity of adverse effects attributable to 

eutrophication.

Most point sources of nutrients (for example, municipal and industrial discharges from waste-water treatment 

facilities) have been eliminated from the BB-LEH watershed. Therefore, the main contributors of nutrients and other 

water-quality constituents to the BB-LEH estuary are nonpoint 

sources (NPSs). Constituents from NPSs are transported to 

streams that feed the estuary by groundwater and by surface 

(storm) runoff from diffuse areas or from areas where sources 

of constituents are not easily identified or quantified (Baker 

and Hunchak-Kariouk, 2006). NPS discharges include surface runoff from agricultural, residential, and nonresidential 

developed areas; leachate from septic systems, underground 

storage tanks, and landfills transported by groundwater; and 

atmospheric deposition. NPS contributions to a surface-water 

body are greatly influenced by land use—both current and 

historical—within a subbasin. NPS constituents transported to 

a surface-water body by surface runoff generally are attributed 

to current land use, whereas NPS constituents transported to 

a surface-water body through groundwater may be attributed 

to either current or historical land use, depending on flow 

paths and recharge rates in the contributing drainage area. For 

example, nitrate from agricultural activities can be discharged 

into streams many years after farmland has been converted to 

urban development, as shown by Kauffman and others (2001).

Source identification of nitrogen in the watershed is 

fundamental to developing and prioritizing plans to reduce 

nitrogen inputs to the estuary. Nitrate (NO3

-

) is commonly 

the most abundant form of dissolved nitrogen in both surface 

water and shallow groundwater. Measurements of nitrogen 

and oxygen isotope ratios (15N:14N and 18O:16O, respectively) 

of NO3

-

 in water samples can be used in combination with 

water-chemistry and hydrologic data to help identify the predominant sources of nitrate, and subsequently nitrogen, to the 

estuary—whether it be from atmospheric, inorganic-fertilizer, 

animal- and septic-waste, or natural sources (Kendall and others, 2007). Nitrogen and oxygen isotope ratios are reported as 

delta (δ) values in units of parts per thousand (denoted as ‰, 

or per mil) of 15N or 18O higher or lower than an international 

reference standard. The δ values are computed as 

δ15N or δ18O = (Rsample/Rstandard – 1) * 1,000 , (1)

where 

Rsample and Rstandard represent the ratios of 15N:14N and 18O:16O 

in the sample and standard, respectively.

The δ15N values are reported relative to the ratio in atmospheric air, and the δ18O values are reported relative to the 

Vienna Standard Mean Ocean Water (VSMOW) ratio; both 

reference standards have defined δ values of 0 ‰ (Kendall and 

others, 2007).

Kendall and others (2007) described the characteristic 

nitrogen and oxygen isotope compositions of the various 

sources of nitrate (fig. 2). Reported δ15N values of nitrate that 

derive from animal and septic waste span a wide range (0 to 

+25 ‰) but are typically at the higher end of the range (+10 

to +20 ‰) as a result of ammonia volatilization preceding 

nitrification. The δ15N values from synthetic nitrate fertilizer 

samples are commonly within a few per mil of zero, whereas 

those from nitrate that was applied as ammonium fertilizer 

and subsequently nitrified have a broader range (-10 to +5 

‰). Most soil nitrate (formed from the oxidation of organic 

matter) has a δ15N value of +2 to +5 ‰ (Kendall, 1998), but 

the δ15N values tend to be higher when the nitrate is derived 

from animal waste. The δ15N values for atmosphere-derived 

nitrate span a wide range (-15 to +15 ‰). When a multiisotope approach is used, δ18O values can be used to further 

differentiate among nitrate sources. The δ18O values from 

synthetic nitrate fertilizers exhibit a fairly narrow range 

(+17 to +25 ‰); those for nitrate derived from ammonium 

fertilizers tend to be lower (less than +15 ‰), and those for 

atmospherically derived nitrate are consistently high (greater 
4 Nutrient Concentrations and Nitrate Source Identification, Barnegat Bay-Little Egg Harbor Watershed, NJ, 2010–11

-10 

0 

10 

20 

30 

40 

50 

60 

70 

80 

90 

100 

-20 -15 -10 -5 0 5 10 15 

δ15N, in per mil

18O, in per mil

δ

NO3

-

 from NH4

+ in

fertilizer and 

precipitation 

Synthetic NO3

- fertilizer 

Soil NO3

- NO3

- from animal and septic waste

Atmospheric NO3

-

(Denitrifier method) 

20 25

Figure 2. Typical ranges of δ15N and δ18O values of nitrate in water derived from atmospheric, fertilizer, soil, and septic and animalwaste sources. (Modified from Kendall and others, 2007; NO3

-

, nitrate; NH4

+

, ammonium)

than +60 ‰). Therefore, the combined use of nitrogen and 

oxygen isotope ratios can yield information about the sources 

of nitrogen to specific water bodies.

Generally, isotopic signatures of nitrate from different 

sources are brought about by the preferential use of lighter 

isotope fractions of oxygen and nitrogen in biological, physical, and chemical reactions. For example, during denitrification, the lighter isotope (14N) is preferentially utilized, leaving 

a larger fraction of the heavier isotope (15N) in the unreacted 

NO3

-

. Over time and distance in anoxic groundwater, denitrification can result in an increase in the δ15N value of dissolved 

nitrate (while decreasing the total concentration of NO3

-

). 

Conversely, nitrification results in lower values of δ15N in the 

nitrate than in the reactant ammonium. 

Additional information about sources and cycling of 

nitrogen can be gained by relating δ15N and δ18O values to 

concentrations of dissolved solids, such as chloride, potassium, and sodium. For example, Silva (2002) reported that a 

positive correlation between δ15N and chloride concentration 

in samples from two creeks near Austin, Texas, in conjunction 

with higher chloride concentrations and higher δ15N values in 

the base-flow samples, is consistent with nitrate from a sewage 

source. Additionally, a plot showing decreasing dissolved-oxygen concentration with increasing δ15N values in groundwater 

from unsewered areas and the absence of such a relation in 

sewered areas was evidence that nitrate in unsewered areas 

was contributed by septic systems. Relations between stable 

isotope ratios and concentrations of dissolved cations and 

anions were similarly examined in this study to help identify 

nitrogen sources and their relative importance in the BB-LEH 

watershed.

Previous and ongoing investigations have estimated rates 

of nitrogen and phosphorus input to the BB-LEH estuary by 

using limited available hydrologic and water-quality data. 

Although some inputs are well characterized (for example, 

tributaries to the Toms River), nutrient loading from groundwater and other streams in the watershed is not well known. 

More accurate determination of the spatial variability of 

nutrient loading throughout the watershed requires additional 

water-quality and hydrologic data. Data needs identified by 

Wieben and Baker (2009) that would improve the understanding of nutrient inputs to the estuary include surface-waterquality data collected during various seasons and under varying hydrologic conditions (base flow and stormflow) for major 

streams in the watershed; more recent surface-water- and 

groundwater-quality data for the southern portion of the BBLEH watershed, particularly in areas that have experienced a 

substantial increase in urban development in recent years; and 
Introduction 5

shallow groundwater-quality analyses near major streams and 

in the area that contributes direct groundwater discharge to the 

estuary, adjacent coastal wetlands, or minor coastal tributaries. Another data need identified is stable isotope analysis of 

nitrate in surface and groundwater to help identify sources of 

nitrogen to the estuary. This would close a critical data gap, 

and would provide information about the types of control 

measures that might be instituted to reduce nitrogen inputs and 

how to focus and prioritize such measures. In this investigation, these data gaps were addressed by the U.S. Geological 

Survey (USGS) in cooperation with the Barnegat Bay Partnership by collecting hydrologic, water-quality, and stable isotope 

data for major streams and representative groundwater wells 

in the BB-LEH watershed.

Purpose and Scope

This report describes the results of a study to determine the predominant sources of nutrients to the BB-LEH 

estuary. It includes data on streamflow and surface-water 

quality measured in samples collected from five streams or 

their tributaries that discharge to the estuary—North Branch 

Metedeconk River, Toms River, Cedar Creek, Mill Creek, and 

Westecunk Creek—from March to October 2010. Surfacewater-quality samples were collected during periods of base 

flow and stormflow in the growing and nongrowing seasons. 

Although surface-water samples were collected during only 

two precipitation events, water-quality and stable isotope 

data collected during this investigation, in combination with 

data collected previously, provide an assessment of ranges of 

nutrient concentrations in the five streams that together drain 

more than 40 percent of the BB-LEH watershed. The first 

sampling event occurred during a major precipitation event in 

the nongrowing season, from March 12 to15, 2010, following a wet winter. More than 5 inches of rain fell on parts of 

the watershed, and the highest peak flow in 81 years of record 

was recorded at the Toms River near Toms River, New Jersey, 

continuous-record streamflow-gaging station (U.S. Geological 

Survey, 2010). The second sampling event occurred during 

the growing season, from September 27 to October 1, 2010, 

when more than 2.5 inches of rain fell on parts of the watershed. This event followed an extended dry period throughout 

much of New Jersey, and streamflows in the study area were 

considerably lower than during the first storm event. Waterquality samples were collected before and during each storm 

so that water-quality data could be obtained for a variety of 

flow conditions. The water-quality constituents for which concentrations are reported are total nitrogen, nitrate plus nitrite, 

ammonia, organic nitrogen, total phosphorus, and orthophosphate; nitrogen and oxygen stable isotope ratios of nitrate in 

surface-water samples also are presented.

This report also provides water-quality and stable isotope 

ratio data for five wells located within the BB-LEH watershed collected from August 2010 to April 2011. These data 

are useful in quantifying concentrations of nutrients that are 

discharged from the subsurface to streams in the watershed 

and directly to the estuary.

Description of Study Area

The study area lies entirely within the Atlantic Coastal 

Plain physiographic province and includes the drainage basins 

of five streams, or their tributaries, that discharge to the BBLEH estuary—North Branch Metedeconk River, Toms River, 

Cedar Creek, Mill Creek, and Westecunk Creek.

Predominant land uses within the BB-LEH watershed 

vary regionally (fig. 3). The northeastern mainland area is 

highly developed, with both residential and nonresidential 

development, and includes major population centers such 

as Toms River and Lakewood. The southeastern mainland 

area contains several protected wildlife refuge and wildlife 

management areas and is less heavily developed than the 

northeastern portion of the watershed; however, this area has 

undergone a substantial increase in development in recent 

years. The complex of barrier islands on the eastern shore of 

the estuary is heavily developed, with the exception of Island 

Beach State Park. Much of the western portion of the watershed lies within the Pinelands Area; this area is protected 

under the Pinelands Comprehensive Management Plan and is 

characterized by large tracts of forested land and some lowdensity development (Kennish, 2001; Hunchak-Kariouk and 

Nicholson, 2001).

The percentage of land in each land-use category was 

quantified for the BB-LEH watershed and for each of the 

five subbasins, on the basis of the 2007 land-use/land-cover 

digital dataset produced by the New Jersey Department of 

Environmental Protection (2010) (table 1). For the purpose of 

this report, residential development was distinguished from 

nonresidential development (commercial, industrial, and 

transportation-related areas, and military installations). The 

distribution of land use in 2007 within the entire BB-LEH 

watershed was 39.1 percent forested, 24.7 percent wetlands, 

22.3 percent residential development, 7.9 percent nonresidential development, 2.7 percent water, 2.1 percent barren land, 

and 1.2 percent agriculture. The headwaters of the Toms River, 

Cedar Creek, Mill Creek, and Westecunk Creek are in the 

Pinelands Area (fig. 1).

The five subbasins differ in size and extent of development (table 1). The North Branch Metedeconk River subbasin upstream from the sampling station (the northernmost 

subbasin) covers 89.4 square kilometers (km2

) and is the 

most heavily developed. Approximately 42 percent of the 

land cover upstream from the sampling station is developed, 

most (80 percent) of which is residential. Approximately 

20 percent of the subbasin is forested, and 5.2 percent is used 

for agriculture. 

The Toms River subbasin upstream from the sampling 

station extends over 323.6 km2

 and is the largest of the subbasins studied. Approximately 25 percent of the subbasin is 

developed (residential, military installation, and other nonresidential development), 44 percent is forested, and 2.4 percent is 
6 Nutrient Concentrations and Nitrate Source Identification, Barnegat Bay-Little Egg Harbor Watershed, NJ, 2010–11

Mill Creek (01409150)

Westecunk Creek (01409281)

Toms River (01408505)

North Branch Metedeconk River (01408120)

Cedar Creek (01408950)

5.2

1.0

20.5

33.9 0.4 8.5

30.5

1.7

17.0

22.9

3.4

8.5

2.4

44.1

71.5

2.0

18.6

2.7

0.3

3.8

1.1

2.6

8.9

19.1

0.5

65.0

0.2

3.8

0.5

1.9

1.5

18.4

2.0

0.4

75.4

0

0 4 8 MILES

6 12 KILOMETERS

74°40' 74°20'

40°

00’

39°

40'

Base from U.S. Geological Survey digital line graph files, 1:24,000

A T L A N T I C 

 O C E A N

74°00’

EXPLANATION

Land use, 2007

Agriculture

Barren

Forest

Nonresidential urban

Residential urban

Water

Wetlands

Subbasin boundary

Figure 3. Land use in the Barnegat Bay-Little Egg Harbor watershed, 2007. (Land use from the New Jersey Department of Environmental Protection digital data file, 2010; pie charts show land use as a percentage of subbasin area; nonresidential urban land use 

includes commercial, industrial, and transportation related areas, and military installations.)
Introduction 7

Table 1. Land-use distributions for selected subbasins of the Barnegat Bay-Little Egg Harbor watershed, 2007.

[Land use from New Jersey Department of Environmental Protection digital data file, 2010; RR, railroad; totals of land-use percentages may not equal 100.0 

percent due to rounding]

U.S. 

Geological Survey 

station 

number

Station name

Drainage 

area, in 

square 

kilometers

Percentage 

of subbasin 

in the 

Pinelands 

Area

Land use, in percentage of drainage area

Agriculture Barren 

land Forest

Residential 

urban

Nonresidential 

urban1

Wetlands and 

water

01408120 North Branch Metedeconk 

River near Lakewood, NJ 89.4 0.0 5.2 1.0 20.5 33.9 8.5 30.9

01408505 Toms River at park footbridge, 

near Toms River, NJ 323.6 56.6 2.4 3.4 44.1 17.0 8.5 24.6

01408950 Cedar Creek at abandoned RR 

bridge, near Lanoka, NJ 136.1 89.3 0.3 2.0 71.5 3.8 2.7 19.7

01409150 Mill Creek near Manahawkin, 

NJ 26.6 100.0 0.2 2.6 65.0 19.1 3.8 9.4

01409281 Westecunk Creek at Railroad 

Ave, at West Creek, NJ 53.3 80.3 0.4 1.9 75.4 2.0 1.5 18.9

1

Nonresidential urban land use includes commercial, industrial, and transportation-related areas, and military installations.

used for agriculture. More than 50 percent of the subbasin lies 

within the Pinelands Area.

The Cedar Creek subbasin upstream from the sampling 

station covers 136.1 km2 and is primarily undeveloped. Nearly 

90 percent of the subbasin lies within the Pinelands Area, and 

more than 70 percent is forested. Approximately 6.5 percent of 

the subbasin is developed; most development is in the lower 

one-fifth of the subbasin and is a mix of residential and nonresidential development. Less than 0.5 percent of the subbasin 

is used for agriculture.

The Mill Creek subbasin upstream from the sampling 

station covers 26.6 km2 and lies entirely within the Pinelands 

Area. About 65 percent of the subbasin is forested, 23 percent 

is developed, and less than 0.5 percent is agricultural land. 

Most of the development is residential and is located primarily 

north of Route 72.

The southernmost subbasin, Westecunk Creek, covers 

53.3 km2

 upstream from the sampling station and is the least 

developed of the subbasins. Seventy-five percent of the subbasin is forested, and less than 4 percent, most of which is 

downstream from the Pinelands Area boundary, is developed. 

Less than 0.5 percent is agricultural land.

The shallow, unconfined Kirkwood-Cohansey aquifer 

system underlies most of the BB-LEH watershed and thickens 

downdip to the southeast (Zapecza, 1989). The Cohansey Formation is composed primarily of medium- to coarse-grained 

sands, with localized occurrences of silt and clay lenses and 

gravel. The Kirkwood Formation is composed of fine- to 

medium-grained sands with clay and, to a lesser extent, coarse 

to fine gravelly sand (Canace and Sugarman, 2009). The 

sands and gravels of this aquifer system make it an excellent 

source of water supply for communities within the watershed; 

however, the Kirkwood-Cohansey aquifer system is highly 

susceptible to contamination from human activity because 

it generally lacks an overlying confining layer to impede the 

downward movement of contaminants originating at the land 

surface (Watt, 2000). In addition, the predominance of highly 

permeable unconsolidated sands and gravels facilitates the 

migration of contaminants from the land surface to the aquifer 

system (Stackelberg and others, 1997).

Some groundwater enters the BB-LEH estuary as direct 

seepage through estuarine sediments, but most groundwater 

discharges from the Kirkwood-Cohansey aquifer system to 

major streams in the watershed, including the Toms and Metedeconk Rivers, and to other, smaller streams and tributaries 

with eventual release to the estuary. Streams, wetlands, and 

other surface-water bodies are hydraulically well connected 

with the Kirkwood-Cohansey aquifer system; consequently, 

groundwater discharge from the aquifer system accounts for 

a high percentage (71–93 percent) of surface-water flow in 

the watershed and is the largest source of freshwater input to 

the BB-LEH estuary (Watt and others, 1994; Gordon, 2003; 

Nicholson and Watt, 1997).

Previous Studies

Both national- and local-scale studies have focused on 

nutrient concentrations in surface and groundwater. Nutrient 
8 Nutrient Concentrations and Nitrate Source Identification, Barnegat Bay-Little Egg Harbor Watershed, NJ, 2010–11

concentrations in surface- and groundwater samples were 

compiled from water-quality assessments conducted across the 

United States from 1992 through 2001 in 51 major study units 

of the USGS’s National Water‐Quality Assessment (NAWQA) 

Program (Dubrovsky and others, 2010). Concentrations of 

total nitrogen were highest in streams in agricultural areas 

(median, 3.8 milligrams per liter (mg/L)) and urban areas 

(median, 1.5 mg/L). Total nitrogen concentrations downstream 

from relatively undeveloped watersheds generally were low. 

Concentrations of total phosphorus were elevated in streams in 

both agricultural and urban areas, with median concentrations 

of 0.26 and 0.25 mg/L, respectively. Concentrations of ammonia and orthophosphate were similar in streams in agricultural, 

urban, and mixed land-use areas. The relative abundance of 

different chemical forms of nitrogen in streams also is related 

to land use. For example, in streams in the northeastern United 

States, Pellerin and others (2004) found that concentrations 

of dissolved organic nitrogen increase as the percentage of 

wetlands in an area increases, whereas concentrations of dissolved inorganic nitrogen, which is typically dominated by 

nitrate, increase as the percentage of developed (agricultural 

plus urban) land increases.

Dubrovsky and others (2010) report that nitrate concentrations in groundwater were highest (median, 3.1 mg/L) 

in shallow wells beneath agricultural land, intermediate in 

shallow wells beneath urban land (median, 1.4 mg/L), and 

lowest in deep wells in major aquifers. The median concentration of nitrate was substantially higher in oxic groundwater 

(that is, water with dissolved-oxygen concentrations greater 

than 0.5 mg/L) than in groundwater without dissolved oxygen 

within each land-use setting. Wakida and Lerner (2005) 

determined that, under certain conditions, nitrate concentrations in groundwater that underlies urban areas can exceed 

those in groundwater beneath surrounding agricultural areas, 

citing leakage from sewage networks, on-site sewage disposal, 

animal waste, contaminated land, industrial processes, atmospheric deposition, urban fertilizer use, and house building as 

common nonagricultural sources of nitrogen to groundwater.

Trends in nutrient enrichment of rivers in the United 

States from 1975 to 1994 were reported by Alexander and 

Smith (2006). Among 250 streams studied (all with drainage 

areas greater than about 1,000 km2), more streams showed 

decreases in flow-adjusted concentrations of total phosphorus 

and nitrogen than increases, with improvements attributed to 

wastewater-treatment upgrades, phosphate detergent bans, 

and declines in some agricultural sources. However, about 

50 percent of all sites studied and more than 60 percent of 

sites in predominantly agricultural and urban watersheds were 

still classified as eutrophic. Similarly, Sprague and others 

(2009) analyzed trends in nutrient concentrations and loads in 

244 streams across the United States from 1993 to 2003 and 

found that concentrations and trends at most of the sites did 

not change significantly during these years. However, a net 

upward flow-adjusted trend occurred at 33 percent of sites for 

total phosphorus, 21 percent for total nitrogen, and 12 percent 

for nitrate, potentially as a result of phosphorus saturation of 

soils in certain areas, and (or) lag time between anthropogenic 

changes on the land surface and changes in nutrient concentrations in streams. 

On a local scale, several studies have focused on nutrient 

concentrations in groundwater and surface water in and near 

the BB-LEH watershed and on nutrient loading to the estuary. 

Nutrient concentrations representative of undisturbed areas 

of the New Jersey Outer Coastal Plain were provided in an 

investigation of the water quality in McDonalds Branch—a 

stream in a minimally developed basin located in the Pinelands Area immediately west of the BB-LEH watershed (Lord 

and others,1990; Johnsson and Barringer, 1993). In more than 

80 surface-water samples, nitrate concentrations were mostly 

at or below the detection limit (0.04 or 0.44 mg/L, depending on the analytical method). In more than 200 groundwater 

samples, generally nitrate was either not detected or detected 

at less than 0.2 mg/L. This finding is consistent with that 

of Zampella (1994), who found that extremely low nutrient 

availability (typically the median nitrate plus nitrite concentration was less than 0.1 mg/L, and the median total phosphorus 

concentration was less than or equal to 0.03 mg/L) naturally 

characterizes the groundwater and surface-water geochemistry 

of the Pinelands hydrologic system (which spans southern and 

western portions of the BB-LEH watershed) and that nutrient concentrations (as well as pH and specific conductance) 

increased with increasing intensity of land use. Zampella and 

others (2007) investigated the relations between land-use 

patterns and water quality in the Mullica River Basin, which 

is immediately south of the BB-LEH Basin, and found that 

10-percent altered land cover is the threshold at which a significant deviation from reference-site water-quality conditions 

occurs in the Mullica River Basin.

Kauffman and others (2001) used a groundwater-flow 

model with particle tracking to examine the effects of land 

use and travel time on the distribution of nitrate within a 

400-square-mile (1,036 square kilometer) study area near 

Glassboro, New Jersey, southwest of the BB-LEH watershed. 

Simulation results showed that nitrate concentrations were 

highest in agricultural areas and lowest in largely undeveloped areas; that nitrate concentrations in the groundwater will 

remain elevated above background levels for decades even 

if nitrate inputs are immediately halted, as a result of the lag 

time associated with groundwater recharge; and that about 

40 percent of the nitrate in aquifer recharge is lost to denitrification and in-stream processes.

Nicholson and others (2003) reviewed available waterquality data sets and reports for groundwater and surface 

water in or near the Metedeconk River, Toms River, and 

Kettle Creek Basins for 1980–2001. Results of analyses of 

untreated water samples collected from more than 13,000 

private wells during 1983–99 indicated that concentrations of 

nitrate exceeded the Federal and New Jersey State drinkingwater standard of 10 mg/L as nitrogen (N) in 0.5 percent of 

samples analyzed, according to records maintained by the 

Ocean County Health Department (Toms River, New Jersey). A similar analysis of more recent data also found that 
Methods 9

nitrate concentrations in 0.5 percent of wells sampled in 2005 

exceeded 10 mg/L (Wieben, 2007). Trend tests conducted by 

Hickman and Barringer (1999) indicate that flow-adjusted 

concentrations of total nitrate plus nitrite increased at the 

Toms River surface-water-quality station during water years1

1986–95; no trend was identified for total phosphorus. The 

maximum concentration of total nitrate plus nitrite during 

this time period at the Toms River station was 0.95 mg/L 

(Hickman and Barringer, 1999). Although not a health risk in 

drinking water, concentrations of less than 1 mg/L NO3

-

 as N 

can be substantial in an aquatic system and can contribute to 

eutrophic conditions. Trend tests conducted by Hickman and 

Gray (2010) for water years 1998–2007 indicate a continuing 

upward trend of dissolved nitrate plus nitrite concentrations at 

the Toms River station and a decreasing trend in total phosphorus concentrations.

Concentrations and loads of nutrient species in four tributaries to the Toms River were reported by Baker and HunchakKariouk (2006). Water-quality and hydrologic data were 

collected over a 5-year period in four subbasins with different 

degrees of land development. Strong correlations were found 

between the percentage of land development and the loads of 

nutrients contributed by stormwater. Streams in subbasins with 

the least developed land had correspondingly lower concentrations of total nitrogen than streams in the moderate and highly 

developed subbasins.

Estimates of total nitrogen loads to the BB-LEH estuary were made by Hunchak-Kariouk and Nicholson (2001) 

and updated by Wieben and Baker (2009). Available data 

were used to quantify streamflow; average nitrogen concentrations during high- and low-flow conditions; and loading 

from surface water, groundwater, and atmospheric deposition. On the basis of the 2009 estimate, the total annual load 

of nitrogen to the BB-LEH estuary was calculated to be 

650,000 kilograms (kg) N per year. Results of the study indicate that nitrogen transported to the estuary in surface water 

contributes 66 percent of the total nitrogen load, direct groundwater discharge contributes 12 percent, and direct atmospheric 

deposition to the estuary surface contributes 22 percent. Total 

nitrogen yields for basins in the more developed areas (greater 

than 10 percent developed) were about twice those for basins 

in less developed areas (less than 10 percent developed). 

Stable isotope analysis has been developed to help 

identify sources of contaminants in surface-water and groundwater (Kendall and others, 2007; Fry, 2006). Aravena and 

others (1993) used stable nitrogen and oxygen isotope analysis 

to delineate a septic-system effluent plume in groundwater. 

The δ15N values were substantially higher in the septic plume 

than in the surrounding groundwater, which had δ15N values consistent with manure and synthetic fertilizer, and soil 

organic nitrogen. Additional information from δ18O analysis 

1

 A water year is the 12-month period beginning October 1 of any given 

year and extending through September 30 of the following year. The water 

year is designated by the calendar year in which it ends and which includes 

9 of the 12 months. Thus, the year ending September 30, 2007, is called the 

2007 water year.

showed that the presence of nitrate outside the plume is 

consistent with nitrification of ammonium and mineralization 

of organic nitrogen. Anisfeld and others (2007) used δ15N and 

δ18O analysis to estimate the fractions of nitrogen from sewage and atmospheric deposition reaching Long Island Sound 

from two rivers in Connecticut. The δ15N values alone were 

too variable to make this estimation; however, the δ18O values 

were useful for determining the contributions of nitrate from 

atmospheric deposition, and the combination of δ15N and δ18O 

results was used to quantify denitrification and determine the 

isotopic signature of sewage effluent for the study area. Cole 

and others (2006) monitored nitrogen loading and δ15N values 

in groundwater seepage to ponds and estuaries on Cape Cod, 

Massachusetts. Areas with larger populations delivered larger 

nitrogen loads with higher δ15N values. The differences among 

δ15N values were strongly related to the density of septic systems, and much of the nitrogen load originated from nearshore 

(as opposed to inland) areas, implying attenuation of nitrogen 

upgradient from the discharge point.

Methods

The following section describes the methods used to collect streamflow and water-quality data.

Streamflow Measurements

The U.S. Geological Survey (USGS) operates continuous 

streamflow-gaging stations on four of the five streams studied in this investigation—North Branch Metedeconk River, 

Toms River, Cedar Creek, and Westecunk Creek (table 2). 

Streamflow data for these stations were collected at 15-minute 

intervals using an electronic data logger and were retrieved 

from the USGS National Water Information System (NWIS), 

an online database. Additionally, manual (discrete) streamflow measurements were made on Mill Creek and Westecunk 

Creek during base flow and twice during stormflow, nearly 

concurrently with sample collection, to supplement the 

existing record because streamgages either were not present on the stream (Mill Creek) or were far from the sampling 

station (Westecunk Creek). These data are stored in NWIS. 

Streamgages were operated and streamflow records were 

computed in accordance with standard USGS protocols as 

described by Rantz and others (1982).

Water-Quality-Data Collection

Both surface-water and groundwater samples were collected and processed following standard USGS sampling protocols (U.S. Geological Survey, 2006). Samples were analyzed 

for concentrations of nitrogen and phosphorus species, for 

major cations and anions (including chloride, potassium, and 

sodium), and for nitrogen and oxygen stable isotope ratios. 

All samples except those collected for stable isotope analysis 
10 Nutrient Concentrations and Nitrate Source Identification, Barnegat Bay-Little Egg Harbor Watershed, NJ, 2010–11

Table 2. Information for selected streamflow-gaging stations in the Barnegat Bay-Little Egg Harbor watershed.

U.S. Geological 

Survey station 

number

Station name Drainage area, in 

square kilometers Period of record

01408120 North Branch Metedeconk River near Lakewood, NJ 89.4 1973-present

01408500 Toms River near Toms River, NJ 318.6 1929–66; 1967-present

01409000 Cedar Creek at Lanoka Harbor, NJ 138.0 1933–58; 1971; 2003-present

01409280 Westecunk Creek at Stafford Forge, NJ 40.9 1974–88; 2003-present

were analyzed at the USGS National Water Quality Laboratory in Denver, Colorado. Samples collected for stable isotope 

analysis were analyzed at the USGS Reston Stable Isotope 

Laboratory in Reston, Virginia. Detection and reporting levels 

for selected analytes are shown in table 3.

Field parameters measured at the time of sample collection included air temperature, water temperature, barometric 

pressure, pH, specific conductance, dissolved-oxygen concentration, and turbidity. Alkalinity was measured at the USGS 

New Jersey Water Science Center field laboratory in West 

Trenton, New Jersey, following sample collection. 

Surface Water

Surface-water samples were collected at five sites 

(fig. 1) during periods of base flow and stormflow over the 

course of two sampling events. Each of the five surface-water 

sites was sampled three times during each event, yielding 

a total of 30 environmental samples for the surface-water 

portion of the study. The first sampling event occurred 

March 11–15, 2010, during the nongrowing season; the second 

sampling event occurred September 26–October 1, 2010, 

during the growing season. The dates of the growing season, 

April 1 to October 31, and nongrowing season, November 1 

to March 31, were based on the average dates of the first and 

final frosts in New Jersey (Ruffner and Bair, 1977). Hydrographs were monitored by using real-time data from the 

continuous streamflow-gaging stations located within the Barnegat Bay-Little Egg Harbor (BB-LEH) watershed. Base-flow 

samples, represented by the pre-storm portion of the hydrograph, were collected prior to the anticipated storm event. The 

first set of stormflow samples was collected during the initial 

portion of the rising limb of the hydrograph to measure the 

concentration of constituents carried by streams during first 

flush (initial direct runoff). A second set of stormflow samples 

was collected near the peak of the hydrograph.

The streamgage and the water-quality sampling station 

on the North Branch Metedeconk River were collocated. As 

a result of concerns related to site accessibility and safety 

during storm sampling, the Toms River sampling station was 

located approximately 1.9 kilometers (km) downstream from 

the streamgage, the Cedar Creek sampling station was located 

Table 3. Minimum detection and reporting levels for selected water-quality constituents.

 [USGS, U.S. Geological Survey; mg/L, milligrams per liter; N, nitrogen; Cl, chloride; P, phosphorus; K, potassium]

Constituent

USGS 

parameter 

code

Range of dates

Minimum 

detection 

level

Minimum 

reporting 

level

Units

Ammonia 608 10/01/2009–09/30/2011 0.01 0.02 mg/L as N

Ammonia plus organic nitrogen 623 10/01/2009–09/30/2011 0.05 0.10 mg/L as N

Chloride 940 10/01/2009–09/30/2011 0.06 0.12 mg/L as Cl

Nitrate plus nitrite 631 10/01/2009–09/30/2011 0.02 0.04 mg/L as N

Nitrite 613 10/01/2009–09/30/2011 0.001 0.002 mg/L as N

Orthophosphate 671 10/01/2009–09/30/2011 0.004 0.008 mg/L as P

Potassium 935 10/01/2009–09/30/2010 0.032 0.064 mg/L as K

Potassium 935 10/01/2010–09/30/2011 0.022 0.044 mg/L as K

Total phosphorus 665 10/01/2009–09/30/2011 0.01 0.02 mg/L as P
Methods 11

approximately 0.6 km upstream from the streamgage, and the 

Westecunk Creek sampling station was located approximately 

3.2 km downstream from the streamgage. On March 15, 2010, 

flood waters prevented access to the original Toms River 

sampling station (01508505). An alternate sampling station 

(01408508) was established 1.9 km downstream to collect the 

peak sample.

A continuous water-quality monitor (sonde) was 

deployed at each surface-water-quality sampling station to 

collect continuous water-quality data for the duration of the 

sampling events. The continuous monitors were used to measure and record water temperature, pH, specific conductance, 

dissolved-oxygen concentration, and turbidity at 5-minute 

intervals. All measurements were made continuously at each 

sampling station during base flow and stormflow, with the 

exception of Mill Creek; the sonde deployed at Mill Creek 

during the March sampling event was not equipped with a sensor to measure turbidity, so continuous turbidity measurements 

are not available for this storm event for Mill Creek.

Continuous water-quality monitors were deployed at 

the time of base-flow sample collection—prior to the onset 

of precipitation. Monitors were chained to bridge railings, 

tree trunks, or other secure objects and submerged at or near 

the bottom of each stream. Continuous monitors remained in 

the streams to collect data until stormflow-sample collection 

was complete. After the continuous monitors were retrieved, 

recorded data were uploaded to the USGS NWIS database. 

The continuous water-quality monitors were calibrated, 

operated, and maintained in accordance with procedures and 

requirements specified by Wagner and others (2006).

Calibration of all sonde sensors was performed prior 

to, and at the end of, each sampling event according to the 

manufacturer’s recommendations and USGS standard protocols. Three pH standards (4, 7, and 10), three specific 

conductance standards (0, 180, and 500 microsiemens per 

centimeter (μS/cm)), and three turbidity standards (0, 50, 

and 100 Nephelometric Turbidity Units (NTU)) were used to 

check sensor calibration and make adjustments if necessary. 

The dissolved-oxygen sensors were calibrated to 100-percent 

O2

 saturation by using water-saturated laboratory air. The 

temperature sensors were checked by comparing readings with 

those of a certified laboratory thermometer. Analytical precision and reporting levels of the sensors are shown in table 4.

Groundwater

Groundwater samples were collected from five wells 

located within the BB-LEH watershed and screened in the 

Kirkwood-Cohansey aquifer system (fig. 4). Each well was 

sampled once during September 2010–May 2011, yielding a 

total of five environmental samples for the groundwater portion of the study. Four of the wells are located in an area that 

contributes direct groundwater discharge to the estuary, adjacent coastal wetlands, or minor coastal tributaries (HunchakKariouk and Nicholson, 2001). One well (292097) is located 

in an area in which groundwater discharges to a stream—Long 

Swamp Creek—which flows into Toms River, and subsequently into the estuary. Two wells—291277 (53 meters (m) 

deep) and 292097 (24 m deep)— are domestic wells located 

in the northern portion of the watershed in highly urbanized 

areas near Toms River, New Jersey, although there are pockets 

of farmland in the immediate vicinity (less than 200 m) of 

well 291277. Well 290799 (17 m deep) is a municipal supply well located in a moderately developed area of Berkeley 

Township. Well 290743 (18 m deep) is a domestic well in a 

moderately developed area of Ocean Township. Well 291256 

(21 m deep) is a domestic well in a sparsely developed area of 

Little Egg Harbor Township. Temperature, pH, specific conductance, dissolved-oxygen concentration, and turbidity were 

monitored while each well was pumped until measurements of 

all parameters were stable before samples were collected.

Table 4. Analytical precision of sensors used in a continuous water-quality monitor (sonde) for groundwater and surface-water 

sampling at stations in the Barnegat Bay-Little Egg Harbor watershed, 2010–11.

[ ̊C, degrees Celsius; mm Hg, millimeters of mercury; mg/L, milligrams per liter; NTU, nephelometric turbidity units; μS/cm, microsiemens per centimeter at 

25 ̊C; --, not applicable]

Measurement 

(units of measurement) Range Resolution Minimum reporting level

Air temperature ( ̊C) -5 – 60 0.01 -5

Water temperature ( ̊C) -5 – 60 0.01 -5

Barometric pressure (mm Hg) 500 – 800 0.1 500

Dissolved oxygen (mg/L) 0 – 50 0.01 0.0

Turbidity (NTU) 0 – 100 0.1 0.0

Specific conductance (μS/cm) 0 – 1,000 1.0 0.0

pH (standard units) 0 – 14 0.01 --
12 Nutrient Concentrations and Nitrate Source Identification, Barnegat Bay-Little Egg Harbor Watershed, NJ, 2010–11

291256

0.29

290743

< 0.02

290799

< 0.02

292097

2.66

291277

3.63

0 6 12 KILOMETERS

0 4 8 MILES

EXPLANATION

Area that contributes

to direct groundwater

discharge

U.S. Geological Survey wellsampling location, unique well

identifier, and concentration of 

nitrate plus nitrite, in milligrams 

per liter

291277

3.63

B a r n e g a t

Little Egg

Harbor

Manahawkin

Bay

B a y

A T L A N T I C O C E A N

74°20' 74°00’

40°

00’

39°

40'

Base from U.S. Geological Survey digital line graph files, 1:24,000

Figure 4. Locations of, and concentrations of nitrate plus nitrite in, five wells sampled within the Barnegat Bay-Little Egg Harbor 

watershed, 2010–11.
Water Quality Under Various Conditions in Surface Water and Groundwater 13

Quality Assurance and Quality Control

Quality assurance was achieved by following protocols 

as described in the National Field Manual (U.S. Geological 

Survey, 2006). Quality-control samples—field blanks and replicates—were collected at a rate of 20 percent of the number 

of environmental samples over the course of the study, such 

that five fields blanks and two sets of replicate samples were 

collected. Field blanks are used to measure the magnitude of 

contamination that may have been introduced during the collection, processing, shipping, or handling of samples, whereas 

replicate samples are used to characterize the amount of variability associated with sample collection.

Concentrations of water-quality constituents in five field 

blanks were compared to concentrations in corresponding 

environmental samples; two field blanks were collected during 

each of the two storm events, and one was collected at well 

292097. Concentrations of compounds in the field blanks were 

either not detected or acceptable at concentrations less than 

three times those in the corresponding environmental sample, 

with one exception. The concentration of ammonia in the environmental sample collected at well 292097 (0.012 (mg/L) was 

less than the concentration in the corresponding field blank 

(0.017 mg/L); however, both concentrations are below the 

minimum reporting level for this constituent (0.02 mg/L) and 

are considered estimated values.

Two sets of replicate samples were collected at Toms 

River during the first storm event. The first set of replicates—

collected during base flow—had higher concentrations of 

nitrogen (0.84 and 0.83 mg/L total nitrogen) and low variability. The second set of replicates—collected during peak flow—

had lower concentrations (0.53 and 0.47 mg/L total nitrogen) 

and higher variability. This variability may be attributed to the 

high turbidity and suspended solids associated with the flood 

waters. To account for this variability, the average values for 

each set of replicate samples were used in the analysis for this 

report.

Water Quality Under Various 

Conditions in Surface Water and 

Groundwater

Surface Water

Continuous Water-Quality Data

Summary statistics of all continuous water-quality monitoring data are presented in appendix 1. Hydrographs showing 

changes in values of selected water-quality characteristics over 

the course of the sampling events are shown in figures 5 and 6. 

The range of values for each characteristic was normalized to 

a scale of 0 to 1 for graphical comparison.

Temperature

Water temperature in all five streams was dependent on 

season more than streamflow or whether the flow was dominated by base flow or stormflow. Prior to the nongrowingseason storm, mean base-flow temperatures ranged from 

9.1 degrees Celsius (°C) (Cedar Creek) to 10.7 °C (Westecunk 

Creek). Over the course of the nongrowing-season storm, the 

mean water temperature at each site declined 1.3 to 2.3°C with 

the addition of colder rain water. Mean base-flow temperatures 

were substantially higher prior to the growing-season storm 

event, ranging from 16.2°C (Mill Creek) to 19.5°C (Toms 

River). Over the course of the growing-season storm, the mean 

temperature remained unchanged (Toms River), declined by 

about 0.1°C (Cedar Creek), or increased less than 1.5 °C (Mill 

Creek, Westecunk Creek, and North Branch Metedeconk 

River). Data from these two sampling events show that water 

temperature in streams in the Barnegat Bay-Little Egg Harbor 

(BB-LEH) watershed is relatively uniform among streams, is 

not greatly affected by precipitation, and is seasonally controlled such that temperatures are higher during and following 

the summer warm-up. Real-time temperature data collected 

over the 2010 water year for four of the five streams confirm 

the seasonal variability of, and the minor influence of precipitation events on, water temperature, which can in turn, affect 

instream biotic and abiotic reaction rates. 

Specific Conductance

Specific conductance (SC) varied among the five 

streams. Prior to the major nongrowing-season storm, mean 

base-flow SC values were higher at the North Branch Metedeconk River (236 microsiemens per centimeter (μS/cm)) 

and Toms River (107 μS/cm) stations, and lower at the Cedar 

Creek (60 μS/cm), Mill Creek (89 μS/cm), and Westecunk 

Creek (36 μS/cm) stations. A similar pattern was present in 

mean base-flow SC values prior to the minor growing-season 

event, with values being highest in the North Branch Metedeconk River (216 μS/cm), intermediate in the Toms River 

(136 μS/cm), and lowest in the three southern streams (Cedar 

Creek, 44 μS/cm; Mill Creek, 79 μS/cm; and Westecunk 

Creek, 46 μS/cm). Higher concentrations of dissolved solids 

in the two northernmost streams are consistent with higher 

levels of urbanization, road salt and fertilizer applications, and 

atmospheric deposition being potential contributors. Mean SC 

values are lowest in the two least developed subbasins—Cedar 

Creek and Westecunk Creek—large areas of which are in the 

Pinelands Area. Extremely low dissolved-solids and low nutrient levels naturally characterize streams in the Pinelands. 

SC decreased in the North Branch Metedeconk and 

Toms Rivers during the major nongrowing-season storm as 

large quantities of rainwater diluted the higher concentrations 

of dissolved solids found in base-flow water (fig. 5A–B). 

During the minor growing-season storm, SC in the North 

Branch Metedeconk and Toms Rivers decreased similarly 

with increasing streamflow, and then increased as streamflow attenuated (fig. 6A–B). SC in Cedar, Westecunk, and 
14 Nutrient Concentrations and Nitrate Source Identification, Barnegat Bay-Little Egg Harbor Watershed, NJ, 2010–11

 Water-quality parameter

pH

Specific conductance

Turbidity

Streamflow at continuous gaging station

Discrete streamflow measurement

EXPLANATION

0.0

0.2

0.4

0.6

0.8

1.0

3/12 3/13 3/14

0

5

10

15

20

25

30

3/15

A. North Branch Metedeconk River

0.0

0.2

0.4

0.6

0.8

1.0

3/12 3/13 3/14

0.6

0.8

1.0

1.2

1.4

1.6

Gage height (upstream from weir), in meters

3/15

C. Cedar Creek

0.0

0.2

0.4

0.6

0.8

1.0

3/12 3/13 3/14

0

20

30

40

50

60

70

Normalized value of water-quality parameter (dimensionless) 

3/15

B. Toms River

0.0

0.2

0.4

0.6

0.8

1.0

3/12 3/13 3/14

0.0

1.0

1.5

2.0

2.5

3.0

3.5

3/15

E. Mill Creek

0.0

0.2

0.4

0.6

0.8

1.0

3/12 3/13 3/14

0

2

3

4

5

6

7

3/15

D. Westecunk Creek

Date 

Date 

10

3/11

0.5

1

Normalized value of water-quality parameter (dimensionless)

Streamflow, in cubic meters per second 

Streamflow, in cubic meters per second Streamflow, in cubic meters per second 

Figure 5. Hydrographs showing continuous water-quality-monitoring data recorded at water-quality stations in the Barnegat BayLittle Egg Harbor watershed during the nongrowing-season sampling event, March 2010. (The range of values for each water-quality 

parameter was normalized to a scale of 0 to 1 for graphical comparison.)
Water Quality Under Various Conditions in Surface Water and Groundwater 15

 Water-quality parameter

pH

Specific conductance

Turbidity

Streamflow at continuous gaging station

Discrete streamflow measurement

EXPLANATION

0.0

0.2

0.4

0.6

0.8

1.0

9/27 9/28

0.2

0.4

0.8

1.0

1.2

1.4

1.6

A. North Branch Metedeconk River

0.0

0.2

0.4

0.6

0.8

1.0

9/26 9/28 9/30

0.6

0.7

0.8

0.9

1.0

Gage height (upstream from weir), in meters

10/2

C. Cedar Creek

0.0

0.2

0.4

0.6

0.8

1.0

9/28 9/30

0

4

6

8

10

Normalized value of water-quality parameter (dimensionless) 

10/2

B. Toms River

0.0

0.2

0.4

0.6

0.8

1.0

9/29 10/1

0.4

0.8

1.0

1.2

1.4

E. Mill Creek

0.0

0.2

0.4

0.6

0.8

1.0

9/26 9/28

0

0.2

0.4

0.6

0.8

1.0

1.2

9/30

D. Westecunk Creek

Date 

Date 

2

9/27

0.6

Streamflow, in cubic meters per second 

Normalized value of water-quality parameter (dimensionless) 

0.6

Streamflow, in cubic meters per second Streamflow, in cubic meters per second 

Figure 6. Hydrographs showing continuous water-quality-monitoring data recorded at water-quality stations in the Barnegat Bay-Little 

Egg Harbor watershed during the growing-season sampling event, September–October 2010. (The range of values for each waterquality parameter was normalized to a scale of 0 to 1 for graphical comparison.)
16 Nutrient Concentrations and Nitrate Source Identification, Barnegat Bay-Little Egg Harbor Watershed, NJ, 2010–11

Mill Creeks increased as streamflow increased during the 

major nongrowing-season storm (fig. 5C–E), as very low 

concentrations of dissolved solids in base-flow water were 

increased by the addition of dissolved solids carried in storm 

runoff. This pattern also occurred in Cedar and Mill Creeks 

during the minor growing-season storm (fig. 6C, E). The tidal 

control of SC during the smaller storm at Westecunk Creek 

masked any pattern of SC relative to streamflow (fig. 6D). 

These results indicate that dissolved solids in storm runoff 

were sufficiently concentrated to increase SC in the streams of 

the relatively undeveloped southern subbasins, whereas dilution by rainwater was sufficient to reduce SC in the northern, 

more developed subbasins to concentrations lower than those 

in base flow.

pH

The pH varied by site, by streamflow, and by season. The 

highest pH values were measured in the North Branch Metedeconk River, where mean values were consistently greater 

than or equal to 6.10. Cedar Creek, which is fed by groundwater and runoff from the highly acidic Pinelands environment, 

exhibited the lowest pH values; mean values were consistently 

less than 4.60 and were lowest (3.98) during the nongrowingseason event. The pH values at Mill Creek were slightly higher 

than those at the other two southern streams, possibly because 

of a higher percentage of urbanized land in the Mill Creek 

subbasin. Values of pH were greater during base flow than 

during stormflow at all sites for both storm events (fig. 5, 6), 

likely a result of dilution brought on by storm runoff and weak 

buffering capacity, as evidenced by low alkalinity values. 

The pH values varied by season, such that mean pH values 

were greater during the growing-season event than during the 

nongrowing-season event for all sites. Increased biological 

activity during the growing season results in the removal of 

carbon dioxide through photosynthesis, which shifts the carbonate equilibrium and raises the pH. Toms River showed the 

greatest difference in mean pH values among sampling events. 

During the nongrowing-season event, mean base-flow and 

stormflow values were 5.17 and 4.62, respectively; during the 

growing-season event, they were 6.39 and 6.19, respectively. 

The diluting effect of the large volume of rainwater during the 

substantial nongrowing-season event overwhelmed the buffering capacity of this stream, causing a decrease in pH to acidic 

levels.

The pattern of pH variability during storms closely 

resembles that of SC for the North Branch Metedeconk and 

Toms Rivers, except that pH in the Toms River continued to 

decline late in the minor growing-season storm, whereas SC 

increased (fig. 6B). Values of pH decreased with increasing 

streamflow in Cedar, Westecunk, and Mill Creeks during the 

major storm (fig. 5C–E) and at Cedar and Mill Creeks during 

the minor storm (fig. 6C, E). The variability in pH during tide 

cycling at Westecunk Creek masked any pH trend attributable 

to the storm event at this site (fig. 6D).

Dissolved Oxygen

Dissolved oxygen (DO) was at or near saturation values 

at all sites during base flow and stormflow. Mean DO concentrations in base flow ranged from 9.71 milligrams per liter 

(mg/L) (Mill Creek) to 10.60 mg/L (Toms River) prior to the 

nongrowing-season storm, and from 7.83 mg/L (Westecunk 

Creek) to 9.56 mg/L (Cedar Creek) prior to the growing-season storm. Mean DO concentrations for both base- and stormflow were 1 to 3 mg/L higher during the nongrowing-season 

sampling event than during the growing-season event at each 

site. This seasonal difference in DO concentration is attributable to higher saturation concentrations in colder water. DO is 

not a limiting factor for biological processes in these streams, 

nor does it appear to be substantially reduced or augmented by 

instream processes during either the minor growing-season or 

major nongrowing-season events, or during base flow in either 

season. This observation does not preclude the possibility of 

reduced DO concentrations in one or more of these streams in 

upstream reaches, or during extreme low-flow conditions. 

Turbidity

Prior to the nongrowing-season event, mean turbidity 

values were highest at the North Branch Metedeconk River 

station (4.1 Nephelometric Turbidity Units (NTU)) and lowest 

at the Westecunk Creek station (0.5 NTU). Streamflow at the 

North Branch Metedeconk River station was about 2.15 cubic 

meters per second (m3/s) during the nongrowing-season baseflow sample collection, which is substantially higher than typical base flow at this station (0.57–1.4 m3

/s), and likely contributed to the higher turbidity readings at this site. Flow was 

still receding from a major precipitation event that occurred 

during February 23–26, 2010. Prior to the growing-season 

storm event, mean turbidity values during base flow were less 

than 2.0 NTU at all sites, ranging from 1.8 NTU at the Toms 

River station to 0.8 NTU at the Cedar Creek station. Water 

levels at this time were lower than seasonal averages because 

drought conditions had persisted through much of the preceding summer. Flow was entirely from base flow, and in-stream 

turbulence was low. Therefore, the turbidity of streamwater 

was expected to be low. With the exception of Mill Creek, for 

which no data were collected during the nongrowing season, 

turbidity increased over the course of the storm at all stations 

during both the nongrowing- and growing-season events, as 

is evident in figures 5 and 6. Mean turbidity values increased 

most during stormflow at the North Branch Metedeconk River 

station (8–10 NTU) and least at the Westecunk Creek station 

(0.5–2.0 NTU), coincident with the degree of development 

in these subbasins. Mean turbidity values for stormflow were 

higher during the major storm event than during the minor 

event. The two least developed subbasins (Cedar Creek and 

Westecunk Creek) yielded storm runoff with the lowest mean 

turbidity readings.

Turbidity increased during both storms at all sites and 

declined after the streamflow had peaked (figs. 5 and 6). This 

result is important for nutrient loading to the BB-LEH estuary, 
Water Quality Under Various Conditions in Surface Water and Groundwater 17

as suspended-sediment transport occurs principally during 

storm events, and some of the nitrogen and most of the phosphorus is sediment-bound. Other consequences of substantial 

sediment loads to the estuary include light attenuation, which 

inhibits growth of aquatic plants, and sediment deposition on 

the estuary floor, which can reduce DO availability as well as 

bury benthic species to depths at which they cannot survive.

Turbidity values have been used to estimate concentrations of total suspended solids (TSS). Gao and others (2008) 

studied the relation between TSS and turbidity in an irrigationdominated watershed in southeastern California. They found 

that linear functions can be used to relate concentration of 

TSS (mg/L) to turbidity (NTU) for high turbidity values, but 

overpredict TSS for turbidity values less than 30 NTU. They 

determined that a power function can be used to accurately 

estimate TSS values from a wider range of NTU values. Their 

best-fit model was

C = 3.6T 0.8 , (2)

where 

C = TSS (mg/L) and T = turbidity (NTU).

Relations between TSS and turbidity are site-specific. To 

accurately develop and use models to predict TSS from turbidity, data must be collected during varying flow conditions 

over a period of time that includes seasonal variability. TSS 

and turbidity data from 70 samples collected from streams in 

the BB-LEH watershed under various flow conditions were 

reviewed to determine whether a significant relation is evident. 

A power function of

C = 2.1T 0.5 (3)

is described by the data; however, there is much uncertainty 

in the relation (r2=0.4). Although the relation is not reliable 

for estimating TSS from turbidity in the BB-LEH watershed, 

the additional data show that the TSS for the streams sampled 

ranges from about 0 to 20 mg/L, and the turbidity range is 

about 0 to 20 NTU. Additional sampling for TSS analysis, 

especially early in precipitation events, would be needed to 

fully characterize the range of TSS in streams in this watershed. This information would be of value because excessive 

sediment has an adverse effect on the benthic community of 

the estuary, and because phosphorus, which can be the limiting 

nutrient of primary biological production when nitrogen is 

plentiful, is transported in surface water primarily as a particulate sorbate.

Nitrogen

Total Nitrogen

Total nitrogen in natural waters consists primarily of 

nitrite, nitrate, ammonia, and organic nitrogen. Concentrations 

of nitrogen species in water samples from the five streams 

studied are shown in table 5 and in figures 7 and 8. Base-flow 

total nitrogen concentrations at the North Branch Metedeconk 

River station were 1.32 and 1.25 mg/L for the nongrowingand growing-season sampling events, respectively. Total nitrogen concentrations decreased to 0.59 and 0.85 mg/L during the 

nongrowing- and growing-season storm events, respectively. 

In this watershed, total nitrogen concentrations are lower in 

storm runoff than in base flow as a result of dilution by precipitation. Total nitrogen concentrations are substantially higher 

under all flow conditions and seasons in the North Branch 

Metedeconk subbasin than they are in the less developed, 

southern subbasins (Cedar, Mill, and Westecunk Creeks).

The concentration of total nitrogen in samples collected 

during base flow at the Toms River sampling station was 

considerably lower prior to the nongrowing-season event 

(20.84 mg/L) than the growing-season event (1.36 mg/L). The 

large watershed provides substantial surface-water storage, 

resulting in a slow recession of stream discharge to base-flow 

conditions following precipitation events. The nongrowingseason sample was likely lower in total nitrogen than the 

growing-season sample because it was diluted by precipitation from recent storms, whereas the growing-season event 

occurred after a protracted dry period, and all base-flow 

streamwater was derived from groundwater discharge with 

little, if any, dilution from recent precipitation. Total nitrogen 

concentrations initially increased during the first flush of the 

nongrowing-season storm, mostly as a result of increases in 

organic nitrogen. Total nitrogen decreased during both storms, 

again most likely as a result of dilution from precipitation. 

Total nitrogen concentrations in base-flow samples from 

Cedar Creek were 0.23 and 0.26 mg/L for the nongrowingand growing-season sampling events, respectively. Nitrogen 

contributions from groundwater in this mostly undeveloped 

watershed appear to be low all year. Storm-flow concentrations were variable with season and over the course of the 

storm events but generally were lower than concentrations in 

more developed basins. The highest total nitrogen concentration at this site (0.57 mg/L) was measured during the first flush 

of the nongrowing-season event; the concentration declined 

to 0.25 mg/L at peak flow as additional rainwater diluted 

the nitrogen. For the growing-season event, concentrations 

increased to 0.39 mg/L at peak flow from nitrogen transported 

from the watershed in storm runoff, as the amount of precipitation was insufficient to provide a dilution effect.

Mill Creek samples had lower total nitrogen concentrations than samples from streams in either of the highly developed North Branch Metedeconk and Toms River subbasins 

but higher than those from streams in the mostly undeveloped Cedar and Westecunk Creek subbasins. The Mill Creek 

watershed is moderately (23 percent) developed and contains 

a large municipal landfill, which has been shown to contribute 

2

 Replicate samples were collected at the Toms River station during the first 

sampling event. The average values for each set of replicate samples were 

used in the analysis.
18 Nutrient Concentrations and Nitrate Source Identification, Barnegat Bay-Little Egg Harbor Watershed, NJ, 2010–11 Table 5. Concentrations of nutrient species in samples collected from five streams in the Barnegat Bay-Little Egg Harbor watershed, 2010.—Continued [NG, nongrowing; G, growing; N, nitrogen; P, phosphorus; <, less than; BF, base flow; FF, first flush; PF, peak flow; constituent concentrations in milligrams per liter] U.S. Geological Survey station number Event number Season Date and time Flow condition Total 

N1

Nitrate plus 

nitrite

Ammonia plus 

organic N Ammonia Organic 

N2

Total 

P

Orthophosphate

01408120 1 NG 03/11/10 10:30 BF 1.32 1.05 0.27 0.027 0.24 0.02 0.00801408120 1 NG 03/13/10 09:30 FF 0.88 0.56 0.32 0.026 0.29 0.06 0.00901408120 1 NG 03/14/10 17:00 PF 0.59 0.27 0.32 < 0.010 0.32 0.04 0.01101408120 2 G 09/26/10 10:20 BF 1.25 1.05 0.20 0.010 0.19 0.02 0.01001408120 2 G 09/27/10 12:30 FF 0.90 0.65 0.25 0.122 0.13 0.09 0.00901408120 2 G 09/28/10 10:15 PF 0.85 0.62 0.23 < 0.010 0.23 0.04 0.00901408505 1 NG 303/11/10 12:30 BF 0.83 0.49 0.34 0.088 0.25 < 0.01 < 0.00401408505 1 NG 303/11/10 12:30 BF 0.84 0.49 0.35 0.090 0.26 0.01 < 0.00401408505 1 NG 03/13/10 11:55 FF 1.13 0.43 0.70 0.132 0.57 0.02 < 0.004401408508 1 NG 303/15/10 13:45 PF 0.54 0.14 0.40 0.016 0.38 0.02 0.004401408508 1 NG 303/15/10 13:45 PF 0.47 0.16 0.31 0.013 0.30 0.02 < 0.00401408505 2 G 09/26/10 12:30 BF 1.36 1.16 0.20 0.057 0.14 < 0.01 0.00601408505 2 G 09/28/10 12:10 FF 1.28 1.08 0.20 0.074 0.13 0.02 0.00401408505 2 G 09/30/10 16:25 PF 1.05 0.80 0.25 0.081 0.17 0.03 0.00401408950 1 NG 03/11/10 14:30 BF 0.23 0.06 0.17 < 0.010 0.17 < 0.01 < 0.00401408950 1 NG 03/13/10 14:10 FF 0.57 0.09 0.48 < 0.010 0.48 < 0.01 < 0.00401408950 1 NG 03/14/10 10:50 PF 0.25 0.05 0.20 < 0.010 0.20 < 0.01 < 0.00401408950 2 G 09/26/10 15:35 BF 0.26 0.09 0.17 0.035 0.14 0.01 0.00501408950 2 G 09/27/10 14:10 FF 0.17 0.09 0.08 0.039 0.04 < 0.01 0.00501408950 2 G 10/01/10 12:00 PF 0.39 0.11 0.28 0.033 0.25 0.04 0.00701409150 1 NG 03/11/10 12:30 BF 0.43 0.10 0.33 0.227 0.10 < 0.01 0.00401409150 1 NG 03/13/10 11:30 FF 0.46 0.17 0.29 0.062 0.23 < 0.01 < 0.00401409150 1 NG 03/14/10 18:50 PF 0.27 0.06 0.21 0.054 0.16 < 0.01 < 0.00401409150 2 G 09/27/10 11:10 BF 0.62 0.12 0.50 0.417 0.08 < 0.01 0.00501409150 2 G 10/01/10 10:00 FF 0.65 0.07 0.58 0.205 0.38 < 0.01 < 0.00401409150 2 G 10/01/10 13:45 PF 0.65 0.03 0.62 0.132 0.49 0.01 < 0.004
Water Quality Under Various Conditions in Surface Water and Groundwater 19

Table 5. Concentrations of nutrient species in samples collected from five streams in the Barnegat Bay-Little Egg Harbor watershed, 2010.—Continued[NG, nongrowing; G, growing; N, nitrogen; P, phosphorus; <, less than; BF, base flow; FF, first flush; PF, peak flow; constituent concentrations in milligrams per liter]

U.S. Geological Event Flow Total Nitrate plus Ammonia plus Organic Total Ortho- Survey station Season Date and time Ammonia number condition N1 nitrite organic N N2 P phosphate number

01409281 1 NG 03/11/10 10:30 BF 0.17 0.05 0.12 < 0.010 0.12 < 0.01 0.00401409281 1 NG 03/13/10 09:20 FF 0.25 0.06 0.19 < 0.010 0.19 < 0.01 < 0.004

01409281 1 NG 03/14/10 13:15 PF 0.20 0.03 0.17 < 0.010 0.17 < 0.01 < 0.004

01409281 2 G 09/26/10 17:55 BF 0.16 0.06 0.10 0.013 0.09 < 0.01 0.00601409281 2 G 10/01/10 08:30 FF 0.27 0.07 0.20 0.020 0.18 < 0.01 0.00601409281 2 G 10/01/10 12:50 PF 0.30 0.08 0.22 0.018 0.20 0.01 0.006

1Concentrations of total nitrogen were calculated as the sum of nitrate plus nitrite and ammonia plus organic nitrogen.2Concentrations of organic nitrogen were calculated by subtracting the value for ammonia from the value for ammonia plus organic nitrogen. In cases where the ammonia concentration was less than the 

minimum detection level (MDL), one-half of the MDL for ammonia was used in the calculation.

3Replicate sample collected.4As a result of overbank flooding, peak-flow sample collection on the Toms River was conducted at station number 01408508 for storm event 1.
20 Nutrient Concentrations and Nitrate Source Identification, Barnegat Bay-Little Egg Harbor Watershed, NJ, 2010–11

 Nitrogen species, as nitrogen

Total nitrogen

Nitrate plus nitrite

Organic nitrogen

Ammonia

Ammonia; less than minimum 

detection level

Base-flow sample

First-flush sample

Peak-flow sample

Streamflow

EXPLANATION

0

10

15

20

25

30

3/8 3/17

0.0

0.2

0.6

0.8

1.0

1.2

1.4

North Branch Metedeconk River

Cedar Creek

0

20

40

50

60

70

0.0

0.6

0.8

1.0

1.2

Streamflow, in cubic meters per second 

Toms River

0

3

4

5

6

7

0.00

0.05

0.10

0.15

0.20

0.25

0.30

Westecunk Creek

Date 

0.4

0.4

5

3/11 3/14 3/20

10

30

3/8 3/11 3/14 3/17 3/20

3/8 3/11 3/14 3/17 3/20 3/8 3/11 3/14 3/17 3/20

0.2

1

2

Date 

0.7

1.0

1.1

1.2

1.3

1.4

0.8

0.9

Gage height (upstream from weir), in meters

0.0

0.3

0.4

0.5

0.6

Concentration, in milligrams per liter

0.1

0.2

Streamflow, in cubic meters per second 

Figure 7. Streamflow hydrographs and concentrations of total nitrogen, nitrate plus nitrite, organic nitrogen, and ammonia in surfacewater samples collected at water-quality stations in the Barnegat Bay-Little Egg Harbor watershed during the nongrowing-season 

sampling event, March 2010. (For Toms River, the average of the replicate values (for base flow and peak flow) was plotted for all 

constituents.)
Water Quality Under Various Conditions in Surface Water and Groundwater 21

 Nitrogen species, as nitrogen

Total nitrogen

Nitrate plus nitrite

Organic nitrogen

Ammonia

Ammonia; less than minimum 

detection level

Base-flow sample

First-flush sample

Peak-flow sample

Streamflow

EXPLANATION

0.0

0.5

1.0

1.5

9/23 9/29

0.0

0.2

0.6

0.8

1.0

1.2

1.4

North Branch Metedeconk River

Cedar Creek

Toms River

0.0

0.4

0.6

0.8

1.0

1.2

0.00

0.05

0.10

0.20

0.25

0.30

0.35

Westecunk Creek

Date 

0.4

9/25 9/27 10/1 9/23 9/27 10/1 10/5

0.2

Date 

9/25 9/29 10/3

9/23 9/25 9/27 9/29 10/1 10/3 10/5 9/23 9/25 9/27 9/29 10/1 10/3 10/5

0.15

0.00

0.30

0.40

0.50

0.10

0.20

0.4

0.6

0.7

0.8

0.9

1.0

Gage height (upstream from weir), in meters

0

4

6

8

10

Streamflow, in cubic meters per second 

2

0.0

1.0

1.5

0.5

Concentration, in milligrams per liter

0.5

Streamflow, in cubic meters per second 

Figure 8. Streamflow hydrographs and concentrations of total nitrogen, nitrate plus nitrite, organic nitrogen, and ammonia in surfacewater samples collected at water-quality stations in the Barnegat Bay-Little Egg Harbor watershed during the growing-season sampling 

event, September–October 2010.
22 Nutrient Concentrations and Nitrate Source Identification, Barnegat Bay-Little Egg Harbor Watershed, NJ, 2010–11

nitrogen to the groundwater and to Mill Creek (New Jersey 

Pinelands Commission, 2006a). Base-flow concentrations 

were 0.43 mg/L (nongrowing season) and 0.62 mg/L (growing season). Stormflow concentrations were highest during the 

growing-season event (0.65 mg/L during first flush and peak 

flow). As with the North Branch Metedeconk River, Toms 

River, and Cedar Creek, large amounts of rainwater appear 

to dilute the total nitrogen concentrations during the major 

nongrowing-season storm but, in this case, not during the 

minor growing-season event. 

Total nitrogen concentrations generally were lowest in 

Westecunk Creek, the southernmost stream sampled. The subbasin of this stream is lightly (less than 4 percent) developed. 

Base-flow concentrations were 0.17 and 0.16 mg/L for the 

nongrowing- and growing-season samples, respectively. Total 

nitrogen concentrations increased during both storms, and the 

highest value, 0.30 mg/L, occurred at peak flow during the 

growing-season event. The increase was mostly from organic 

nitrogen, probably from natural sources, which had accumulated on the land surface between storm events from decomposing plant and animal matter and was carried to the stream 

in runoff.

Historical total nitrogen data for 1980–2009 were 

retrieved from the USGS NWIS database for comparison with 

data collected during this investigation to determine whether 

nutrient concentrations in the limited number of samples 

collected are representative of historical data. In cases in 

which historical data for a site were not available in NWIS, 

data from the U.S. Environmental Protection Agency Storage 

and Retrieval (STORET) database were used. For this comparison, growing- and nongrowing-season data were pooled. 

Sample-collection sites varied somewhat from those previously used; therefore, some differences in concentrations were 

expected. The median total nitrogen concentration for each 

stream during base-flow and stormflow conditions is shown in 

table 6. There is relatively close agreement among current and 

historical median total nitrogen concentrations, particularly for 

Cedar, Mill, and Westecunk Creeks. However, median total 

nitrogen concentrations for the North Branch Metedeconk and 

Toms Rivers from the 2010 sampling effort are considerably 

higher than the historical concentrations. These higher concentrations are consistent with studies of water-quality trends, 

which indicate that concentrations of dissolved nitrate plus 

nitrite in both the Metedeconk and Toms River watersheds are 

increasing (Hickman and Barringer, 1999; Hickman and Gray, 

2010).

These data indicate that total nitrogen concentrations in 

these five streams are related to the land use (current or historical) within the subbasin. The basins of the North Branch Metedeconk and Toms Rivers are the most developed subbasins, 

and these streams exhibit the highest concentrations of total 

nitrogen. The Mill Creek subbasin is moderately developed, 

and total nitrogen concentrations in the stream are moderate. 

Cedar Creek and Westecunk Creek have largely undeveloped 

subbasins and have the lowest total nitrogen values. Concentrations in these five streams during precipitation events tend 

to remain unchanged or increase from base-flow values early 

in the storm, but a diluting effect on total nitrogen concentrations later in the storm is observed during major events.

Nitrate plus Nitrite

Nitrite (NO2

-

) typically is absent or is present in small 

concentrations relative to nitrate (NO3

-

) in natural waters 

because it is a thermodynamically unstable intermediate in the 

microbially mediated nitrogen cycle; it is rapidly converted to 

nitrate in oxygenated water and is reduced to ammonia under 

anoxic conditions. Nitrite was either not detected (detection 

limit 0.001 mg/L) or was detected as less than 6 percent of the 

total of nitrate plus nitrite (more typically less than 1 percent) 

in samples collected for this investigation. Therefore, nitrite 

concentrations are not reported separately here, and for the 

purposes of this study, concentrations of nitrate plus nitrite can 

be considered to represent nitrate concentrations.

Nitrate is the most abundant nitrogen species in the 

North Branch Metedeconk River, especially during base flow 

(figs. 7, 8). The base-flow nitrate plus nitrite concentration 

prior to both storms was 1.05 mg/L, which represents approximately 80 percent of the total nitrogen mass during base flow. 

Nitrate plus nitrite concentrations decreased to 0.27 mg/L 

(46 percent of the total nitrogen) during the nongrowing-season storm and to 0.62 mg/L (73 percent of the total nitrogen) 

during the growing-season storm. The contribution of nitrate 

plus nitrite may have been lower during the nongrowingseason storm as a result of a reduced contribution from applied 

inorganic fertilizer or of greater dilution resulting from the 

major precipitation event.

The nitrate plus nitrite concentration in base flow at 

Toms River was 0.49 mg/L (59 percent of the total nitrogen) 

and 1.16 mg/L (85 percent of the total nitrogen) during the 

nongrowing and growing seasons, respectively. This large difference in base-flow nitrate plus nitrite concentration between 

seasons may be explained by the influence of dilution from 

recent recharge on the nongrowing-season sample, and (or) 

it may be the result of a reduced contribution from fertilizer 

application during the nongrowing season. As in the Metedeconk River Basin, nitrate plus nitrite is the dominant nitrogen 

species during base flow, and nitrate plus nitrite concentrations 

(and nitrate as a percentage of total nitrogen) decreased over 

the course of both storms. Nitrate plus nitrite accounted for 

less than 40 percent of the total nitrogen in stormflow samples 

during the nongrowing season and greater than 75 percent during the growing season.

Nitrate plus nitrite was not the predominant nitrogen 

contributor at streams in the three less developed, southern 

watersheds. Base-flow nitrate plus nitrite concentrations 

ranged from 0.05 mg/L (Westecunk Creek) to 0.12 mg/L (Mill 

Creek) and accounted for less than 40 percent of the total 

nitrogen concentration at each of these three sites. Base-flow 

concentrations were slightly higher at all three sites during the 

growing season than during the nongrowing season. Concentrations of nitrate plus nitrite increased or decreased variably 
Water Quality Under Various Conditions in Surface Water and Groundwater 23

Table 6. Median nutrient concentrations for streams in the Barnegat Bay-Little Egg Harbor watershed measured in samples 

collected for this study (2010), and determined from historical water-quality data for 1980–2009.

 [mg/L, milligrams per liter; NB, North Branch; --, not available; <, less than]

Stream Flow

condition

Median total nitrogen 

concentration, in mg/L 

(number of samples)

Median total phosphorus 

concentration, in mg/L 

(number of samples)

Current Historical Current Historical

NB Metedeconk River Base flow 1.29 (2) 0.89 (27) 0.02 (2) 0.04 (27)

NB Metedeconk River Stormflow 0.87 (4) 0.76 (12) 0.05 (4) 0.05 (12)

Toms River Base flow 1.10 (2) 0.83 (37) < 0.01 (2) 0.02 (64)

Toms River Stormflow 1.10 (4) 0.75 (26) 0.02 (4) 0.02 (43)

Cedar Creek Base flow 0.25 (2) < 0.17 (30) < 0.01 (2) < 0.01 (30)

Cedar Creek Stormflow 0.32 (4) < 0.24 (7) < 0.01 (4) < 0.01 (7)

Mill Creek Base flow 0.53 (2) -- < 0.01 (2) 0.02 (3)

Mill Creek Stormflow 0.56 (4) 0.64 (3) < 0.01 (4) --

Westecunk Creek Base flow 0.17 (2) 0.20 (11) < 0.01 (2) 0.01 (11)

Westecunk Creek Stormflow 0.26 (4) 0.26 (4) < 0.01 (4) < 0.02 (2)

over the course of the storms; stormflow concentrations ranged 

from less than 0.05 mg/L (Mill Creek during the growing 

season and Westecunk Creek during the nongrowing season) 

to 0.17 mg/L (Mill Creek during the nongrowing season) and 

accounted for less than 40 percent of the total nitrogen concentration in stormflow samples, except at Cedar Creek during the 

growing season, when it accounted for 53 percent.

Ammonia

Ammonia is present in trace amounts in all streams under 

most flow conditions, except Mill Creek, in which it accounts 

for, on average, 60 percent of the base-flow total nitrogen 

concentration. The base-flow concentration of ammonia was 

0.227 mg/L during the nongrowing season and 0.417 mg/L 

during the growing season at Mill Creek but was less than 

0.100 mg/L at all other streams during base flow. The concentration of ammonia (and ammonia as a percentage of total 

nitrogen) at Mill Creek decreased over the course of both 

storms, indicating dilution by storm runoff. An expansive 

domestic-waste landfill located upstream from the sampling 

point on Mill Creek has been associated with groundwater 

contamination, including high concentrations of ammonia 

(New Jersey Pinelands Commission, 2006a; New Jersey 

Pinelands Commission, 2006b). This is probably the point 

source of most of the ammonia in the Mill Creek samples. The 

Metedeconk and Toms Rivers both exhibited concentrations of 

ammonia greater than 0.100 mg/L during the first flush of one 

storm event.

Organic Nitrogen

In general, concentrations of organic nitrogen appear to 

be greater in the more developed than in the less developed 

subbasins; however, the ratio of organic nitrogen to total 

nitrogen is greater in the less developed subbasins. Although 

average base-flow concentrations of organic nitrogen are 

higher in the North Branch Metedeconk (0.22 mg/L) and 

Toms (0.20 mg/L) Rivers than in the other streams, the ratio 

of organic nitrogen to total nitrogen is much lower in base 

flow (less than 35 percent) than in the other streams sampled. 

Septic and sewage effluent and organic fertilizers are potential 

sources of organic nitrogen in developed areas that are less 

prevalent in undeveloped areas. For both the North Branch 

Metedeconk and Toms Rivers, concentrations of organic 

nitrogen in both base-flow and stormflow samples were higher 

during the nongrowing season than during the growing season, 

with nongrowing-season stormflow proportions reaching 54 

and 67 percent at the Metedeconk and Toms River stations, 

respectively.

Organic nitrogen is the dominant species of nitrogen 

in nearly all samples collected from Cedar and Westecunk 

Creeks, and in all stormflow samples collected from Mill 

Creek (where nitrogen in base flow is dominated by ammonia). The average base-flow concentration of organic nitrogen, 

0.16 mg/L at Cedar Creek and 0.11 mg/L at Westecunk Creek, 

accounted for more than 50 percent of the total nitrogen in 

base flow at these sites. Stormflow concentrations generally 

were greater than those in base flow and, in some cases, made 

up more than 75 percent of the total nitrogen in stormflow 
24 Nutrient Concentrations and Nitrate Source Identification, Barnegat Bay-Little Egg Harbor Watershed, NJ, 2010–11

samples from Cedar, Mill, and Westecunk Creeks. The subbasins of these streams are the least developed, and more 

than 80 percent of their area lies within the Pinelands Area, 

indicating natural inputs of organic nitrogen to the streams that 

increase during periods of storm runoff. 

Phosphorus

Total phosphorus and orthophosphate were either 

not detected or measured at very low concentrations in 

surface-water samples (table 5). North Branch Metedeconk 

River samples had the highest levels of total phosphorus 

(0.02–0.09 mg/L) and orthophosphate (0.008–0.011 mg/L). 

Total phosphorus was not detected at levels above 0.04 mg/L 

as P in samples from all other streams. Orthophosphate was 

detected at very low but measurable concentrations more 

frequently during the growing season sampling event. The 

absence of substantial concentrations of phosphorus in the 

samples collected indicates that the streams may be phosphorus-limited under some conditions.

Like total nitrogen data, historical phosphorus data for 

1980 to 2009 (table 6) were retrieved from NWIS or from 

STORET when NWIS data were not available. Median 

phosphorus concentrations from the current study are in 

close agreement with historical data for all streams studied, 

with phosphorus either not detected or measured at very low 

concentrations. North Branch Metedeconk River is the only 

stream in which reportable concentrations of phosphorus 

were detected, either in samples collected for this study or in 

historic data.

Dissolved Solids

In general, concentrations of dissolved solids (including 

major ions such as chloride (Cl-) and potassium (K+)) in base 

flow were highest in samples collected at the North Branch 

Metedeconk River station (greater than 42 mg/L for Cl- and 

greater than 2.3 mg/L for K+), followed by the Toms River 

station (greater than 20 mg/L for Cl-

 and greater than 1.2 mg/L 

for K+). For the North Branch Metedeconk and Toms Rivers, 

concentrations of Cl- and K+ were highest during base flow 

and decreased during stormflow, indicating dilution by storm 

runoff. Higher values at North Branch Metedeconk River 

during the nongrowing-season sampling event than during the 

growing-season event, as well as an increase in Cl- values at 

Toms River during the first flush of the nongrowing-season 

event, may be related to the application of road salt during winter months; however, the pattern of higher values of 

Cl- and K+ during base flow than during stormflow at North 

Branch Metedeconk River is not season-dependent and 

indicates the likelihood of a source other than road salt for the 

elevated dissolved-solids concentrations at this site.

Concentrations of dissolved solids in base flow were 

lowest in samples collected at the Cedar and Westecunk Creek 

stations (less than 11 mg/L for Cl-

 and less than 0.6 mg/L for 

K+). These streams have the least developed subbasins in the 

study area, and the natural characteristics of waters within 

these subbasins, including low concentrations of dissolved 

solids, remain relatively undisturbed. Although concentrations 

of Cl- and K+ at these two stations were consistently low (less 

than 15 mg/L) under all flow conditions, higher concentrations 

of Cl- and K+ tended to occur during stormflow, indicating an 

influx of dissolved solids with storm runoff.

Groundwater

Nitrogen

Concentrations of nitrogen species in water samples 

from the five wells (fig. 4) are shown in table 7. The two 

wells farthest north (291277 and 292097) have total nitrogen 

concentrations of 3.66 and 2.69 mg/L as nitrogen, respectively, 

99 percent of which is in the form of nitrate. Total nitrogen 

concentrations in wells 290799 and 290743, both of which 

are located in moderately developed coastal areas, were less 

than 0.07 mg/L, with concentrations of nitrate plus nitrite not 

detected. The southernmost well (291256) had a total nitrogen 

concentration of 0.32 mg/L, with a nitrate plus nitrite concentration of 0.29 mg/L. Concentrations of ammonia plus organic 

nitrogen were less than the minimum detection level (MDL) 

for all samples (table 3).

Historical water-quality measurements made by using 

sampling and analytical conditions comparable to those used 

in the current study were available for two of these wells in 

the USGS NWIS database. Well 291277 was sampled previously in 1998 with a nitrate plus nitrite concentration of 

1.77 mg/L and in 2006 with a nitrate plus nitrite concentration 

of 3.33 mg/L. With the most recent nitrate plus nitrite value of 

3.63 mg/L, and all three samples having been collected under 

oxic conditions, nitrate concentrations at this site appear to be 

increasing; however, additional sample-analysis data would 

be helpful for confirming this apparent trend. Well 290743 

was last sampled in 1982 and had a nitrate plus nitrite concentration of 0.13 mg/L. The concentration in the most recent 

sample was less than the MDL. Dissolved oxygen levels at 

wells 290743 and 290799 during this sampling event were 

extremely low (0.2–0.3 mg/L). The anoxic environment may 

have led to nitrate losses through denitrification, contributing 

to the nondetects in samples from these two wells.

Phosphorus

Total phosphorus was not found at detectable concentrations in any of the wells sampled. These results are to be 

expected because phosphorus tends to adsorb to sediments and 

typically is not found in the dissolved phase in groundwater. 

Orthophosphate was not detected in either of the two northernmost wells, which have the most heavily developed contributing areas. Extremely low concentrations (0.005–0.009 mg/L) 

were measured in the other three wells. Overall, phosphorus in 
Water Quality Under Various Conditions in Surface Water and Groundwater 25

Table 7. Concentrations of nutrient species, and values of nitrogen and oxygen stable isotope ratios in nitrate, in samples collected 

from five wells screened in the Kirkwood-Cohansey aquifer system in the Barnegat Bay-Little Egg Harbor watershed, 2010–11.

[N, nitrogen; P, phosphorus; <, less than; --, not available; constituent concentrations in milligrams per liter]

U.S.Gelogical 

Survey station 

number

Date

Well 

depth, in 

meters

Water use Total 

N1

Nitrate 

plus 

nitrite

Ammonia 

plus 

organic N

Total 

P

Orthophosphateδ15N, in 

per mil

δ180, in 

per mil

290743 09/01/2010 18 Domestic < 0.07 < 0.02 < 0.05 < 0.01 0.009 -- --

290799 09/14/2010 17 Public supply < 0.07 < 0.02 < 0.05 < 0.01 0.009 -- --

291256 09/22/2010 21 Domestic 0.32 0.29 < 0.05 < 0.01 0.005 6.00 4.07

291277 05/17/2011 53 Domestic 3.66 3.63 < 0.05 < 0.01 < 0.004 5.09 3.17

292097 04/28/2011 24 Domestic 2.69 2.66 < 0.05 < 0.01 < 0.004 4.12 2.07

1

Concentrations of total nitrogen were calculated as the sum of nitrate plus nitrite and ammonia plus organic nitrogen. In cases where both constituent 

concentrations were less than the minimum detection limit (MDL), the concentration of total nitrogen is less than the sum of the MDLs. In cases where one 

constituent concentration was less than the MDL, one-half of the MDL for that constituent was used in the calculation. Total nitrogen values may differ from 

those reported in the National Water Information System database.

the groundwater represented by these five samples would not 

contribute substantially to the phosphorus concentrations and 

loads in surface water were this water to discharge to streams 

in the watershed.

Stable Isotope Analysis

Surface Water

Values of δ18O and δ15N for all surface-water samples collected (table 8, figure 9A) are indicative of mixing of nitrogen 

within the watershed from multiple sources. Many of the data 

points are clustered within the overlapping fields of nitrogen 

originating from soil and animal and septic waste; several 

points are just outside the common ranges for nitrogen from 

synthetic and ammonium fertilizers. None of the points fall 

within or near the typical range of δ18O values for atmospheric 

nitrate, indicating that the atmosphere is not a predominant 

source of nitrogen in the streams sampled. Generally, δ18O values were higher, and δ15N values were lower, during stormflow 

than during base flow.

On a plot of the relation between δ18O and δ15N values for 

base-flow samples (fig. 9B), all points fall within the overlapping fields of nitrogen originating from soil and animal and 

septic waste, and just outside the common range for nitrogen 

from ammonium in fertilizer and precipitation. This observation indicates that a mixing of nitrogen from multiple subsurface sources carried in groundwater likely contributes to 

the base-flow nitrogen load. Over the two sampling events, 

δ15N values ranged from +6.04 to +9.29 per mil (‰) during 

base flow; the highest base-flow δ15N value for both sampling 

events was measured in a sample from Westecunk Creek. The 

δ15N values ranged from +4.88 to +10.21 ‰ during stormflow (first flush and near peak). The wider range of values 

during stormflow indicates that mixing was slightly greater 

during stormflow than during base flow. There was an overall decrease in δ15N values at all sites over the course of the 

nongrowing-season storm (fig. 10A) and at Cedar and Westecunk Creeks during the growing-season storm (fig. 10B). The 

lower δ15N values indicate a greater influence of nitrogen that 

originated as atmospheric nitrate, as ammonium in fertilizer or 

precipitation, as synthetic nitrate fertilizer, or some combination thereof, and a smaller influence of nitrogen from animal 

and septic waste during stormflow than during base flow. The 

higher δ15N isotopic signature at Westecunk Creek, coupled 

with the presence of a nearby wastewater-pumping facility and 

a sewage odor documented during sampling, is consistent with 

sewage effluent as a source of nitrogen input to this stream. 

However, the nitrate concentration within this subbasin was 

very low (less than 0.1 mg/L); therefore, any contribution 

from sewage is minimal.

Over the two sampling events, δ18O values ranged from 

+1.03 to +10.85 ‰ during base flow and from +2.05 to 

+19.61 ‰ during stormflow (first flush and near peak), again 

indicating a greater mixing of sources during stormflow. Much 

of the variation in the δ18O values during stormflow occurred 

during the first storm event, during which a substantial amount 

of precipitation fell on the watershed. There was an overall increase in δ18O values at all sites over the course of the 

nongrowing-season storm (fig. 11A), and, to a lesser degree, 

at all sites except Mill Creek during the growing-season storm 

(fig. 11B). The higher δ18O values during stormflow indicate 

a greater influence of nitrogen from the atmosphere during 

stormflow than during base flow.

In general, there was a shift from higher δ15N and 

lower δ18O values during base-flow conditions to lower δ15N 

and higher δ18O values as the storms progressed and flows 

increased. This pattern is shown in a plot of the average δ15N 
26 Nutrient Concentrations and Nitrate Source Identification, Barnegat Bay-Little Egg Harbor Watershed, NJ, 2010–11

Table 8. Values of nitrogen and oxygen stable isotope ratios in nitrate in samples collected from five streams in the Barnegat 

Bay-Little Egg Harbor watershed, 2010.

[NG, nongrowing; G, growing; BF, base flow; FF, first flush; PF, peak flow]

U.S. Gelogical 

Survey station 

number

Event 

number Season Date and time Flowcondition

δ15N, in 

per mil

δ180, in 

per mil

01408120 1 NG 03/11/10 10:30 BF 6.91 3.65

01408120 1 NG 03/13/10 09:30 FF 5.98 8.86

01408120 1 NG 03/14/10 17:00 PF 4.98 6.70

01408120 2 G 09/26/10 10:20 BF 8.30 2.56

01408120 2 G 09/27/10 12:30 FF 7.06 5.96

01408120 2 G 09/28/10 10:15 PF 7.96 5.21

01408505 1 NG 103/11/10 12:30 BF 6.90 3.36

01408505 1 NG 103/11/10 12:30 BF 7.07 3.28

01408505 1 NG 03/13/10 11:55 FF 6.54 6.81

2

01408508 1 NG 103/15/10 13:45 PF 5.55 9.90

2

01408508 1 NG 103/15/10 13:45 PF 6.14 11.52

01408505 2 G 09/26/10 12:30 BF 6.04 1.03

01408505 2 G 09/28/10 12:10 FF 6.29 2.05

01408505 2 G 09/30/10 16:25 PF 6.41 2.22

01408950 1 NG 03/11/10 14:30 BF 7.19 5.86

01408950 1 NG 03/13/10 14:10 FF 6.63 17.88

01408950 1 NG 03/14/10 10:50 PF 5.93 16.95

01408950 2 G 09/26/10 15:35 BF 6.81 3.98

01408950 2 G 09/27/10 14:10 FF 6.74 9.81

01408950 2 G 10/01/10 12:00 PF 5.10 8.78

01409150 1 NG 03/11/10 12:30 BF 6.90 5.28

01409150 1 NG 03/13/10 11:30 FF 5.72 9.15

01409150 1 NG 03/14/10 18:50 PF 4.88 14.61

01409150 2 G 09/27/10 11:10 BF 7.05 10.85

01409150 2 G 10/01/10 10:00 FF 6.76 7.65

01409150 2 G 10/01/10 13:45 PF 6.76 9.02

01409281 1 NG 03/11/10 10:30 BF 9.29 9.49

01409281 1 NG 03/13/10 09:20 FF 10.21 19.61

01409281 1 NG 03/14/10 13:15 PF 5.40 16.42

01409281 2 G 09/26/10 17:55 BF 8.50 6.98

01409281 2 G 10/01/10 08:30 FF 7.38 8.65

01409281 2 G 10/01/10 12:50 PF 6.24 8.50

1

Replicate sample collected.

2

As a result of overbank flooding, peak-flow sample collection on the Toms River was conducted at station number 01408508 for storm event 1.
Water Quality Under Various Conditions in Surface Water and Groundwater 27

B

A

Base flow−nongrowing season

First flush−nongrowing season

Peak flow−nongrowing season

Base flow−growing season

First flush−growing season

Peak flow−growing season

EXPLANATION

-10 

0 

10 

20 

30 

40 

50 

60 

70 

80 

90 

100 

-20 -15 -10 -5 0 5 10 15 

δ15N, in per mil 

18O, in per mil

δ

NO3

- from NH4+ in

fertilizer and 

precipitation 

Synthetic NO3

- fertilizer 

NO3

- from animal and septic 

waste

Atmospheric NO3

-

(Denitrifier method) 

20 25

-10 

0 

10 

20 

30 

40 

50 

60 

70 

80 

90 

100 

NO3

- from NH4+ in

fertilizer and 

precipitation 

Synthetic NO3

- fertilizer 

Soil NO3

-

NO3

- from animal and septic 

waste

Atmospheric NO3

-

(Denitrifier method) 

Soil NO3

-

Figure 9. δ15N and δ18O compositions of nitrate in surface-water samples collected at water-quality stations in the Barnegat Bay-Little 

Egg Harbor watershed, March–October 2010, during A, all flow conditions and B, base-flow conditions. (NO3

-

, nitrate; NH4

+

, ammonium)
28 Nutrient Concentrations and Nitrate Source Identification, Barnegat Bay-Little Egg Harbor Watershed, NJ, 2010–11

B

8

12

11

10

9

7

6

4

A

5

15N, in per mil

δ

8

12

11

10

9

7

6

4

Base flow First flush Peak flow

5

15N, in per mil

δ

North Branch Metedeconk River

Toms River

Cedar Creek

EXPLANATION

Mill Creek

Westecunk Creek

Figure 10. δ15N compositions of nitrate in surface-water samples collected during base flow, first flush, and peak flow at water-quality 

stations in the Barnegat Bay-Little Egg Harbor watershed during the A, nongrowing-season sampling event, March 2010, and B, growingseason sampling event, September–October 2010.
Water Quality Under Various Conditions in Surface Water and Groundwater 29

B

10

20

15

5

0

A

18O, in per mil 

δ

10

20

15

5

0

Base flow First flush Peak flow

18O, in per mil 

δ

North Branch Metedeconk River

Toms River

Cedar Creek

EXPLANATION

Mill Creek

Westecunk Creek

Figure 11. δ18O compositions of nitrate in surface-water samples collected during base flow, first flush, and peak flow at water-quality 

stations in the Barnegat Bay-Little Egg Harbor watershed during the A, nongrowing-season sampling event, March 2010, and B, growingseason sampling event, September–October 2010.
30 Nutrient Concentrations and Nitrate Source Identification, Barnegat Bay-Little Egg Harbor Watershed, NJ, 2010–11

and δ18O values for each of the sampling events (fig. 12). The 

pattern is more apparent for the nongrowing-season storm 

event—likely a result of the extreme hydrologic conditions at 

the time of sample collection, with substantial precipitation 

and flooding conditions during the first storm event resulting 

in a clearly visible pattern, and drought conditions followed by 

a less substantial rainfall resulting in a dampened pattern for 

the second event. 

The δ18O values by site, in order of least to most developed subbasin, are shown in figure 13A. Areas with a greater 

percentage of development typically have a greater percentage 

of impervious surface, and subsequently a greater percentage 

of precipitation reaching streams by way of storm runoff than 

do less developed areas. If atmospheric nitrate is an important 

source of nitrogen, there would be a positive relation between 

δ18O values and impervious cover, such that higher δ18O 

values occur in areas with a greater percentage of impervious cover (Silva and others, 2002). However, the lowest δ18O 

values were measured at the Toms River and North Branch 

Metedeconk River stations, and 10 of the 12 samples collected at these two sites had δ18O values less than the median 

(+8.075 ‰) for all samples collected. The nitrate concentrations in base-flow samples from these two sites were high; 

therefore, it would take a substantial amount of nitrate from 

the atmosphere to have an effect on the isotopic signature of 

nitrate in water from these two sites. The results indicate that 

although atmospheric deposition may contribute nitrate to 

these two subbasins, it is not a predominant source. Instead, it 

appears that nitrate from atmospheric sources contributes proportionally less of the overall nitrate as development increases 

within the BB-LEH watershed. No relation between δ15N and 

percent urban land use is apparent (fig. 13B).

In contrast, the highest δ18O values were measured 

in samples collected from Cedar and Westecunk Creeks, 

particularly during stormflow. Because these subbasins are less 

developed and have a lower percentage of impervious cover 

than do the Toms and Metedeconk River subbasins, the results 

indicate that atmospheric deposition of nitrate has a greater 

influence on these less developed subbasins within the BBLEH watershed, likely because they contain few other major 

sources of nitrogen. Because the nitrate concentrations in base 

flow within the less developed subbasins are low, even a small 

contribution of nitrogen from the atmosphere has a substantial effect on the isotopic signature. Nitrate concentrations in 

samples from the less developed subbasins are low (less than 

0.2 mg/L); therefore, the contribution from the atmosphere is 

minimal.

A comparison of concentrations of dissolved solids 

such as Cl-

 and K+ with isotope ratios can provide additional 

information about the likelihood of the relative importance 

of specific sources of nitrogen within a watershed. In a plot 

of the relation between concentrations of Cl- and δ15N values, 

it is evident that higher Cl- concentrations at North Branch 

Metedeconk correspond to higher δ15N values for both storm 

events (fig. 14A); a positive relation during both storm events 

is also shown at the North Branch Metedeconk River station 

for K+ concentrations and δ15N values (fig. 14C). The coincidence of higher δ15N values with higher concentrations of 

dissolved solids, specifically in samples collected from the 

North Branch Metedeconk River during base flow, is likely 

a consequence of the higher degree of development within 

the subbasin. Higher values of δ15N and Cl- concentrations 

are consistent with a sewage, animal waste, or septic source 

(Silva and others, 2002; Mullaney and others, 2009). Within 

the North Branch Metedeconk River subbasin, sewage inputs 

could stem from leaky sewer pipes and septic systems associated with current and recent urban land use and (or) from 

animal waste associated with documented poultry farming that 

0

2

4

6

8

10

12

14

March,

base flow

March,

first flush

March,

peak flow

September,

base flow

September,

first flush

September,

peak flow

Sampling event and flow condition 

15N and 

δ 18O, in per mil 

δ

δ15N

δ18O 

Figure 12. δ15N and δ18O compositions of nitrate in water at water-quality stations in the Barnegat Bay-Little Egg Harbor watershed, 

averaged by sampling event and flow condition.
Water Quality Under Various Conditions in Surface Water and Groundwater 31

Westecunk

Creek

01409281

(3.5)

Cedar

Creek

01408950

(6.5)

Mill

Creek

01409150

(22.9)

Toms

River 

01408505

(25.5)

North Branch

Metedeconk

River

01408120

(42.4)

B

10

20

15

5

0

A

Delta 

δ18O, in per mil 

6

10

8

4

Delta 

δ15N, in per mil 

Nongrowing season, base flow

Nongrowing season, stormflow

EXPLANATION

Growing season, base flow

Growing season, stormflow

0 10 20 30 40

Percent

Figure 13. A, δ18O values and B, δ15N values in relation to percent urban land use (residential plus nonresidential, shown in parentheses) in subbasins for water-quality stations in the Barnegat Bay-Little Egg Harbor watershed.
32 Nutrient Concentrations and Nitrate Source Identification, Barnegat Bay-Little Egg Harbor Watershed, NJ, 2010–11

3.5

3.0

2.5

2.0

1.5

1.0

0.5

0.0

20

60

50

40

30

10

0

A

Potassium concentration, in milligrams per liter 

0 5 10 15 0 5 10 15 20 25

Chloride concentration, in milligrams per liter 

B

C D

North Branch Metedeconk River, nongrowing season

North Branch Metedeconk River, growing season

Toms River

Cedar Creek

Mill Creek

Westecunk Creek

EXPLANATION

δ15N, in per mil 18 δ O, in per mil

Figure 14. Relation between concentrations of water-quality constituents and isotope ratios at water-quality stations in the Barnegat 

Bay-Little Egg Harbor watershed: A, chloride concentration and δ15N value, B, chloride concentration and δ18O value, C, potassium 

concentration and δ15N value, and D, potassium concentration and δ18O value.
Water Quality Under Various Conditions in Surface Water and Groundwater 33

was historically prominent in the region (Ocean County Agriculture Development Board, 2008). Clear relations between 

Cl- or K+ concentrations and δ15N values are not evident for 

Toms River and Mill Creek; at Cedar and Westecunk Creeks, 

Cl- and K+ concentrations are consistently low and do not vary 

with changes in δ15N values. 

 In plots of the relation of Cl- and K+ concentrations to 

δ18O values (fig. 14B, D), samples collected at North Branch 

Metedeconk River show a pattern in which higher concentrations of dissolved solids correspond to lower δ18O values. A 

similar pattern between dissolved-solids concentrations and 

δ18O values is evident for Toms River, although dissolvedsolids concentrations are generally lower than those at the 

North Branch Metedeconk River station. This pattern indicates 

the dilution of dissolved-solids concentrations in the stream 

when the influence of precipitation is great. Low concentrations of dissolved solids during periods of precipitation are to 

be expected because atmospheric deposition does not typically 

contain large amounts of dissolved solids. At Cedar and Westecunk Creeks, concentrations of Cl-

 and K+ are consistently 

low and do not vary with changes in δ18O values. Like δ15N 

values, δ18O values at Mill Creek show no clear relation with 

dissolved-solids concentrations, possibly as a result of a mixture of influences from recent development and undeveloped, 

undisturbed forested land within the Mill Creek subbasin.

Overall, the variability in δ15N and δ18O values and 

coincident variability in Cl- and K+ concentrations are strong 

evidence that the nitrate in these streams (at least in the Toms 

and Metedeconk Rivers) derives from a mixture of sources.

Groundwater

In a plot of δ18O as a function of δ15N values for groundwater samples (fig. 15), the δ15N values are in the overlapping 

range of nitrogen originating from fertilizer, soil, and and 

animal and septic waste sources. Although five wells were 

sampled, nitrate concentrations in samples from two of the 

wells (290743 and 290799) were below the level necessary to 

conduct nitrogen and oxygen stable isotope analyses; therefore, results of stable isotope analyses are reported for only 

-10 

0 

10 

20 

30 

40 

50 

60 

70 

80 

90 

100 

-20 -15 -10 -5 0 5 10 15 

δ15N, in per mil

18O, in per mil

δ

NO3

- from NH4+ in

fertilizer and 

precipitation 

Synthetic NO3

- fertilizer 

Soil NO3

-

NO3

- from animal and septic waste

Atmospheric NO3

-

(Denitrifier method) 

20 25

291256

EXPLANATION

U.S. Geological Survey well number

291277 292097

Harbor watershed, 2010–11. (NO3

-

, nitrate; NH4

+

, ammonium)

Figure 15. δ15N and δ18O compositions of nitrate in groundwater samples collected from shallow wells in the Barnegat Bay-Little Egg 
34 Nutrient Concentrations and Nitrate Source Identification, Barnegat Bay-Little Egg Harbor Watershed, NJ, 2010–11

three wells. Well 292097 with a nitrate plus nitrite concentration of 2.66 mg/L had a δ15N value of + 4.12 ‰, and well 

291277 with a nitrate plus nitrite concentration of 3.63 mg/L 

had a δ15N value of + 5.09 ‰ (table 7). Both of these wells 

are located in the northern portion of the watershed in highly 

developed areas; there are small pockets of farmland in 

the immediate vicinity of well 291277. The relatively high 

concentration of nitrate plus nitrite in these wells compared 

to those in wells in the less developed subbasins is indicative 

of anthropogenic sources of nitrogen, and the low to moderate δ15N values, particularly at well 292097, are more consistent with fertilizer sources than with animal or septic waste, 

although the observed range of δ15N values is indicative of 

a mixing of nitrogen sources. The fact that well 292097 had 

a high nitrate plus nitrite concentration, is relatively shallow, discharges to a major stream, and had a δ15N signature 

more characteristic of fertilizer indicates that a portion of 

the nitrogen measured in streams may have originated as 

nitrogen-based fertilizer and been discharged to the stream in 

groundwater. Additional sampling of shallow groundwater is 

necessary to verify this hypothesis. Well 291256 had a δ15N 

value of +6.00 ‰, indicating a slightly greater influence from 

animal and septic waste sources than at the northern two wells. 

However, the nitrate plus nitrite concentration at this site 

(0.29 mg/L) is low; therefore, any contribution from animal 

or septic waste is minimal. The δ18O values for samples from 

each of these three wells is low (+2.07 to +4.07 ‰), indicating 

that atmospheric nitrate is not a major contributor of nitrogen 

to the water in these wells and not a major source of nitrogen 

within the underlying aquifer.

Summary and Conclusions

The Barnegat Bay-Little Egg Harbor (BB-LEH) estuary 

is a shallow, lagoonal-type estuary located along the central 

coast of New Jersey, separated from the Atlantic Ocean by a 

narrow complex of barrier islands. Physical characteristics 

of the estuary, including its shallow depth and poor flushing, render it particularly susceptible to the effects of nutrient 

loading; consequently, the ecological health of the estuary has 

deteriorated over the last few decades. Most point sources of 

nutrients have been eliminated from the BB-LEH watershed; 

therefore, the main contributors of nutrients to the BB-LEH 

estuary are nonpoint sources that can be attributed to either 

current or historical land uses.

The U.S. Geological Survey, in cooperation with the 

Barnegat Bay Partnership, sampled five streams and five 

wells in the BB-LEH watershed for determination of nutrient 

concentrations and stable isotope composition to help quantify 

and identify sources of nutrient loading to the estuary. From 

March to October 2010, streamflow and surface-water-quality 

data were collected in five streams or tributaries to the estuary—North Branch Metedeconk River, Toms River, Cedar 

Creek, Mill Creek, and Westecunk Creek. Surface-waterquality samples were collected during periods of base flow and 

stormflow over two sampling events, one each in the growing 

and nongrowing seasons. 

Concentrations of total nitrogen in these five streams 

appear to be related to land use, such that streams in subbasins 

characterized by extensive urban development (and historical 

agricultural land use)—North Branch Metedeconk and Toms 

Rivers—exhibited the highest total nitrogen concentrations 

(0.84–1.36 milligrams per liter (mg/L) in base flow). The 

two streams in subbasins with the least development—Cedar 

Creek and Westecunk Creek—exhibited the lowest total nitrogen concentrations (0.16–0.26 mg/L in base flow).

Base-flow total nitrogen concentrations in the highly 

developed North Branch Metedeconk and Toms River subbasins were dominated by nitrate (59–85 percent of total nitrogen); nitrate concentrations decreased during storm events as 

a result of dilution by storm runoff. The contribution of nitrate 

plus nitrite at these two sites was generally lower during the 

nongrowing-season event than during the growing-season 

event, which may be explained by the influence of dilution 

from recent recharge on the nongrowing-season sample, dilution from the larger precipitation event, or a reduced contribution from fertilizer application during the nongrowing season.

Ammonia is present in trace amounts under most flow 

conditions in all streams except Mill Creek. In Mill Creek, 

ammonia makes up, on average, 60 percent of the base-flow 

total nitrogen concentration. Elevated concentrations of 

ammonia in this stream are likely associated with leachate 

from a landfill located upstream.

Organic nitrogen is the dominant species of nitrogen 

in nearly all samples collected from Cedar and Westecunk 

Creeks, and in all stormflow samples collected from Mill 

Creek (base flow at this site is dominated by ammonia). 

Stormflow concentrations of organic nitrogen generally were 

greater than those in base flow and, in some cases, made 

up more than 75 percent of the total nitrogen in stormflow 

samples from Cedar, Mill, and Westecunk Creeks. The subbasins of these streams are the least developed and a large 

proportion (more than 80 percent) of their areas lies within the 

Pinelands Area, indicating the likelihood that natural inputs 

of organic nitrogen to the streams increase during periods of 

storm runoff.

Total phosphorus and orthophosphate were not detected 

in most of the surface-water samples, with the exception of 

those collected from the North Branch Metedeconk River, 

where concentrations ranged from 0.02 to 0.09 mg/L for total 

phosphorus and 0.008 to 0.011 mg/L for orthophosphate. The 

absence of substantial concentrations of phosphorus in the 

samples collected indicates that the streams may be phosphorus-limited under some conditions.

Measurements of nitrogen and oxygen stable isotope 

ratios (15N:14N and 18O:16O) of nitrate in surface-water samples 

revealed that a mix of subsurface sources, including animal 

and septic waste, soil nitrogen, and commercial fertilizers, 

likely contributes to the base-flow nitrogen load. The results 

also indicate that atmospheric deposition is not a predominant 

source of nitrogen transported to the BB-LEH estuary from the 
Summary and Conclusions 35

watershed, although this does not preclude the possibility of 

substantial contribution of atmospheric nitrate directly to the 

estuary surface. The contribution of nitrate in the watershed 

from the atmosphere increases during stormflow. Over the two 

sampling events, δ15N values ranged from +6.04 to +9.29 per 

mil (‰) during base flow. There was an overall decrease in 

δ15N values at all sites over the course of the nongrowing-season storm, and at the Cedar and Westecunk Creek sites during 

the growing-season storm. The lower δ15N values indicate a 

greater influence of nitrogen that originated as atmospheric 

nitrate, as ammonium in fertilizer or in precipitation, as 

synthetic nitrate fertilizer, or some combination thereof, and a 

smaller influence of animal and septic waste during stormflow 

than during base flow.

Over the two sampling events, δ18O values ranged from 

+1.03 to +10.85 ‰ during base flow and from +2.05 to 

+19.61 ‰ during stormflow. Overall, δ18O values increased at 

all sites over the course of the nongrowing-season storm and 

increased, although to a lesser degree, at all sites except Mill 

Creek during the growing-season storm. The higher δ18O values during stormflow indicate a greater influence of nitrogen 

from the atmosphere during stormflow than during base flow. 

The highest δ18O values occurred at Cedar and Westecunk 

Creeks during stormflow. The results indicate that atmospheric 

deposition of nitrate has a greater influence on these less 

developed subbasins within the BB-LEH watershed, likely 

because there are few other major sources of nitrogen (animal 

and septic waste, fertilizers) in the less developed subbasins. 

Nitrate from atmospheric sources appears to contribute proportionally less of the overall nitrate as development increases 

within the BB-LEH watershed. The nitrate concentrations 

in base-flow samples from the North Branch Metedeconk 

and Toms River basins were high; therefore, it would take a 

substantial amount of nitrate from the atmosphere to affect the 

isotopic signature of nitrate in water from these two sites.

The shift from higher δ15N and lower δ18O values during 

base-flow conditions to lower δ15N and higher δ18O values as 

the storms progress and flows increase is greatest in the subbasins with the lowest nitrate concentrations, which is to be 

expected if atmospheric nitrate is responsible for this pattern. 

The pattern is more apparent for the nongrowing-season storm 

event, likely as a result of the extreme hydrologic conditions 

at the time of sample collection brought on by substantial 

precipitation and flooding conditions.

Dissolved-solids concentrations and isotope ratios were 

compared to help provide additional information about the 

likelihood of the occurrence of specific sources of nitrogen within a watershed. Concentrations of dissolved solids 

(chloride (Cl-) and potassium (K+)) in base flow were highest 

in samples collected at the North Branch Metedeconk River 

station (greater than 42 mg/L for Cl- and greater than 2.3 mg/L 

for K+). The North Branch Metedeconk River was the only site 

at which there was a strong correlation between dissolved-solids concentrations and stable isotope ratios. In general, higher 

Cl- and K+ concentrations in the North Branch Metedeconk 

River correspond to higher δ15N values. Higher δ15N values 

and higher Cl- concentrations are both consistent with a sewage, animal waste, or septic source.

In addition to the surface-water samples, groundwater 

samples were collected from five wells located within the 

BB-LEH watershed and screened in the unconfined KirkwoodCohansey aquifer system. Concentrations of nitrate plus nitrite 

ranged from not detected to 3.63 mg/L, with higher concentrations occurring in the highly developed northern portion of the 

watershed. In the two wells in which the nitrate concentration 

was not detected, dissolved-oxygen levels were extremely low 

(0.2–0.3 mg/L), indicating an anoxic environment that may 

have led to nitrate losses through denitrification. The two wells 

with the highest nitrate concentrations had low δ15N values 

of +4.12 and +5.09 ‰. The relatively high concentration of 

nitrate plus nitrite in these wells compared to those in wells in 

the less developed subbasins indicates anthropogenic sources 

of nitrogen, and the low to moderate δ15N values, particularly 

at well 292097, are more consistent with fertilizer sources than 

with animal or septic waste. Total phosphorus was not found 

at detectable concentrations in any of the wells sampled, and 

orthophosphate was either not detected or measured at very 

low concentrations (less than 0.010 mg/L).

Through the collection of hydrologic, water-quality, and 

stable isotope data for major streams, streams with little available data, and representative wells in the BB-LEH watershed, 

this study addressed several key data gaps in the understanding of nutrient dynamics in the watershed. The collection of 

surface-water data from subbasins with varying degrees of 

development and under varying hydrologic conditions allows 

for a more accurate determination of the spatial and temporal 

variability of nutrient loading throughout the watershed than 

could have been made previously. Stable isotope analyses 

revealed that a mixture of subsurface sources of nitrate from 

some combination of animal and septic waste, soil nitrogen, 

and commercial fertilizers likely contributes to the baseflow nitrogen load, and that atmospheric deposition is not a 

predominant source of nitrogen transported to the estuary from 

the watershed. The analysis of samples collected at downstram 

locations on five major streams in this study improved current 

understanding of nitrogen concentrations and sources on a 

broad scale for a large portion of the watershed. One limitation of the sampling design is that the contributing area for the 

surface-water samples contained a mixture of land uses and, 

therefore, a mixture of nitrogen sources. Future monitoring 

efforts may include stable isotope sampling in smaller subbasins dominated by single land uses to improve understanding of the relation between specific land uses and their isotopic 

signatures within the watershed. Analysis of such samples 

would help to further characterize the relative importance 

of terrestrial nitrate sources—animal and septic waste, soil 

nitrogen, and commercial fertilizers—and aid in prioritizing 

strategies for reducing nutrient loads such as controlling development, reducing application of commercial fertilizers, and 

implementing stormwater management.

Given that many of the higher concentrations of nitrate 

were measured in groundwater samples and in surface-water 
36 Nutrient Concentrations and Nitrate Source Identification, Barnegat Bay-Little Egg Harbor Watershed, NJ, 2010–11

samples collected during base flow, effective monitoring 

strategies would include extensive groundwater sampling, 

as recent information on nutrient concentrations in shallow 

groundwater is extremely limited. Additionally, sampling 

along groundwater flow paths would provide information 

about the role of denitrification in the system.

Acknowledgments

The authors gratefully acknowledge the many members 

of the U.S. Geological Survey (USGS) New Jersey Water 

Science Center who participated in data collection, often during adverse weather conditions. Special thanks are extended 

to USGS employees Anna Deetz, Michael DeLuca, Heather 

Heckathorn, Pamela Reilly, Robert Reiser, Daniel Skulski, 

and Nicholas Smith for their contributions to the water-quality 

sampling effort, and to Robert Atkinson, Eric Lindbloom, 

Donald Storck, and Blaine White, also of the USGS, for their 

contributions to the streamgaging effort.

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Appendix

Appendix 1. Summary statistics of continuous water-quality data, Barnegat Bay-Little Egg Harbor watershed, 2010.
40 Nutrient Concentrations and Nitrate Source Identification, Barnegat Bay-Little Egg Harbor Watershed, NJ, 2010–11

Appendix 1. Summary statistics of continuous water-quality data, Barnegat Bay-Little Egg Harbor watershed, 2010.—Continued

[ ̊C, degrees Celsius; μS/cm, microsiemens per centimeter at 25 ̊C; mg/L, milligrams per liter; NTU, nephelometric turbidity units; --, not available]

Statistic Temperature

( ̊C)

Specific 

conductance 

(μS/cm)

pH

Dissolved 

oxygen 

(percent of 

saturation)

Dissolved 

oxygen 

(mg/L)

Turbidity 

(NTU)

01408120 North Branch Metedeconk River near Lakewood, NJ, nongrowing season, March 2010, base flow

Lowest value 8.4 234 6.46 88.9 10.13 3.4

1st quartile 9.0 236 6.53 89.3 10.21 3.8

Mean 9.5 236 6.53 90.6 10.35 4.1

Median 9.5 236 6.54 89.9 10.32 4.1

3rd quartile 10.0 236 6.54 92.0 10.49 4.3

Highest value 10.1 241 6.54 93.7 10.65 8.8

Number of observations 327 327 327 327 327 327

Standard deviation 0.5 1 0.01 1.6 0.17 0.5

01408120 North Branch Metedeconk River near Lakewood, NJ, nongrowing season, March 2010, stormflow

Lowest value 6.7 87 5.82 84.5 10.20 3.9

1st quartile 7.2 97 5.84 86.6 10.35 9.3

Mean 7.5 148 6.10 87.2 10.45 14.1

Median 7.4 124 5.90 87.0 10.43 14.4

3rd quartile 7.9 186 6.47 87.4 10.50 17.8

Highest value 8.8 277 6.56 89.9 10.79 38.7

Number of observations 832 832 832 832 832 832

Standard deviation 0.5 59 0.30 0.9 0.13 5.5

01408120 North Branch Metedeconk River near Lakewood, NJ, growing season, September–October 2010, base flow

Lowest value 18.6 216 6.58 85.5 7.99 1.0

1st quartile 18.8 216 6.63 86.8 8.08 1.2

Mean 18.9 216 6.67 88.2 8.19 1.4

Median 19.0 216 6.68 88.4 8.19 1.4

3rd quartile 19.1 217 6.72 89.5 8.29 1.5

Highest value 19.1 217 6.79 90.3 8.35 7.1

Number of observations 201 201 201 201 201 201

Standard deviation 0.2 0 0.05 1.5 0.11 0.5

01408120 North Branch Metedeconk River near Lakewood, NJ, growing season, September–October 2010, stormflow

Lowest value 18.5 145 6.34 80.3 7.34 1.3

1st quartile 19.1 168 6.45 81.8 7.44 6.3

Mean 19.5 183 6.51 83.3 7.66 10.0

Median 19.4 183 6.50 83.1 7.62 9.5

3rd quartile 20.0 195 6.56 84.9 7.87 13.5

Highest value 20.2 236 6.69 85.9 8.03 39.2

Number of observations 374 374 374 374 374 369

Standard deviation 0.6 20 0.08 1.6 0.22 5.8
Appendix 1 41

Appendix 1. Summary statistics of continuous water-quality data, Barnegat Bay-Little Egg Harbor watershed, 2010.—Continued

[ ̊C, degrees Celsius; μS/cm, microsiemens per centimeter at 25 ̊C; mg/L, milligrams per liter; NTU, nephelometric turbidity units; --, not available]

Statistic Temperature

( ̊C)

Specific 

conductance 

(μS/cm)

pH

Dissolved 

oxygen 

(percent of 

saturation)

Dissolved 

oxygen 

(mg/L)

Turbidity 

(NTU)

01408505 Toms River at park footbridge, near Toms River, NJ, nongrowing season, March 2010, base flow

Lowest value 8.9 106 5.10 90.7 10.40 0.8

1st quartile 9.0 107 5.15 92.0 10.45 1.0

Mean 9.5 107 5.17 92.6 10.60 1.1

Median 9.5 107 5.18 92.4 10.60 1.0

3rd quartile 10.0 107 5.19 93.6 10.68 1.0

Highest value 9.8 108 5.22 94.7 10.90 5.8

Number of observations 353 353 353 353 353 353

Standard deviation 0.2 0 0.02 1.0 0.10 0.4

01408505 Toms River at park footbridge, near Toms River, NJ, nongrowing season, March 2010, stormflow

Lowest value 7.4 67 4.31 84.6 10.10 1.7

1st quartile 8.0 71 4.32 85.6 10.15 4.0

Mean 8.0 85 4.62 87.4 10.30 6.3

Median 7.9 77 4.35 86.1 10.20 7.0

3rd quartile 8.0 99 5.00 88.3 10.50 8.0

Highest value 9.2 111 5.41 94.3 11.20 10.8

Number of observations 1,390 1,390 1,390 1,390 1,390 1,387

Standard deviation 0.4 15 0.39 2.7 0.30 2.1

01408505 Toms River at park footbridge, near Toms River, NJ, growing season, September–October 2010, base flow

Lowest value 19.1 135 6.32 86.5 8.00 1.4

1st quartile 19.3 136 6.35 87.5 8.07 1.7

Mean 19.5 136 6.39 90.3 8.30 1.8

Median 19.4 136 6.39 90.2 8.29 1.8

3rd quartile 19.7 137 6.43 93.2 8.53 1.9

Highest value 19.7 138 6.48 95.1 8.71 3.8

Number of observations 201 201 201 201 201 201

Standard deviation 0.2 1 0.04 2.8 0.22 0.3

01408505 Toms River at park footbridge, near Toms River, NJ, growing season, September–October 2010, stormflow

Lowest value 17.5 119 5.64 85.7 7.71 1.8

1st quartile 19.2 126 6.16 86.6 7.95 2.8

Mean 19.5 130 6.19 87.6 8.04 4.4

Median 19.5 129 6.28 86.9 8.01 3.2

3rd quartile 19.8 134 6.30 88.0 8.13 5.4

Highest value 20.5 141 6.34 93.1 8.53 16.5

Number of observations 1,492 1,492 1,492 1,492 1,492 1,492

Standard deviation 0.6 5 0.17 1.6 0.17 2.3
42 Nutrient Concentrations and Nitrate Source Identification, Barnegat Bay-Little Egg Harbor Watershed, NJ, 2010–11

Appendix 1. Summary statistics of continuous water-quality data, Barnegat Bay-Little Egg Harbor watershed, 2010.—Continued

[ ̊C, degrees Celsius; μS/cm, microsiemens per centimeter at 25 ̊C; mg/L, milligrams per liter; NTU, nephelometric turbidity units; --, not available]

Statistic Temperature

( ̊C)

Specific 

conductance 

(μS/cm)

pH

Dissolved 

oxygen 

(percent of 

saturation)

Dissolved 

oxygen 

(mg/L)

Turbidity 

(NTU)

01408950 Cedar Creek at abandoned RR bridge, near Lanoka, NJ, nongrowing season, March 2010, base flow

Lowest value 7.8 59 4.05 87.9 10.08 0.7

1st quartile 8.6 60 4.06 88.2 10.17 0.8

Mean 9.1 60 4.07 90.8 10.47 1.4

Median 9.2 60 4.06 89.6 10.33 0.9

3rd quartile 9.6 60 4.07 92.7 10.69 1.5

Highest value 9.7 61 4.17 106.7 12.59 6.4

Number of observations 307 307 307 307 307 307

Standard deviation 0.5 0 0.02 3.2 0.38 1.6

01408950 Cedar Creek at abandoned RR bridge, near Lanoka, NJ, nongrowing season, March 2010, stormflow

Lowest value 6.8 59 3.92 90.3 10.72 0.9

1st quartile 7.4 61 3.95 92.9 11.13 2.3

Mean 7.6 69 3.98 94.1 11.24 4.2

Median 7.6 67 3.96 94.0 11.21 3.1

3rd quartile 7.9 73 3.99 94.8 11.36 5.3

Highest value 8.4 91 4.12 99.7 11.75 28.7

Number of observations 1,402 1,402 1,402 1,402 1,402 1,399

Standard deviation 0.4 9 0.04 1.9 0.21 3.0

01408950 Cedar Creek at abandoned RR bridge, near Lanoka, NJ, growing season, September–October 2010, base flow

Lowest value 19.0 43 4.52 99.9 9.15 0.5

1st quartile 19.3 43 4.54 102.5 9.44 0.6

Mean 19.4 44 4.57 103.8 9.56 0.8

Median 19.4 44 4.57 104.0 9.56 0.7

3rd quartile 19.5 44 4.58 105.2 9.69 0.9

Highest value 19.6 45 4.70 106.2 9.84 1.9

Number of observations 229 229 229 229 229 229

Standard deviation 0.1 1 0.03 1.5 0.15 0.2

01408950 Cedar Creek at abandoned RR bridge, near Lanoka, NJ, growing season, September–October 2010, stormflow

Lowest value 16.4 45 4.06 105.6 9.79 0.5

1st quartile 19.1 46 4.36 109.9 10.10 0.9

Mean 19.3 54 4.42 112.8 10.40 2.8

Median 19.6 47 4.50 112.7 10.43 1.5

3rd quartile 19.8 56 4.52 115.8 10.59 2.6

Highest value 20.6 87 4.79 119.8 11.11 52.3

Number of observations 1,496 1,496 1,496 1,496 1,496 1,493

Standard deviation 1.0 13 0.18 3.3 0.31 4.5
Appendix 1 43

Appendix 1. Summary statistics of continuous water-quality data, Barnegat Bay-Little Egg Harbor watershed, 2010.—Continued

[ ̊C, degrees Celsius; μS/cm, microsiemens per centimeter at 25 ̊C; mg/L, milligrams per liter; NTU, nephelometric turbidity units; --, not available]

Statistic Temperature

( ̊C)

Specific 

conductance 

(μS/cm)

pH

Dissolved 

oxygen 

(percent of 

saturation)

Dissolved 

oxygen 

(mg/L)

Turbidity 

(NTU)

01409150 Mill Creek near Manahawkin, NJ, nongrowing season, March 2010, base flow

Lowest value 8.9 81 5.61 78.9 9.03 --

1st quartile 9.3 84 5.68 82.4 9.42 --

Mean 9.7 89 5.69 85.5 9.71 --

Median 9.4 89 5.69 84.6 9.64 --

3rd quartile 10.3 93 5.70 87.0 9.86 --

Highest value 10.6 100 5.81 113.0 12.64 --

Number of observations 398 398 398 398 398 --

Standard deviation 0.6 6 0.02 5.0 0.50 --

01409150 Mill Creek near Manahawkin, NJ, nongrowing season, March 2010, stormflow

Lowest value 8.0 50 4.72 78.9 9.18 --

1st quartile 8.3 54 4.89 82.2 9.64 --

Mean 8.4 90 5.05 84.0 9.84 --

Median 8.5 74 4.96 83.9 9.83 --

3rd quartile 8.7 122 5.20 85.8 10.04 --

Highest value 8.9 181 5.61 90.4 10.60 --

Number of observations 739 739 739 739 739 --

Standard deviation 0.2 39 0.26 2.3 0.28 --

01409150 Mill Creek near Manahawkin, NJ, growing season, September–October 2010, base flow

Lowest value 15.1 78 5.70 79.6 7.74 0.3

1st quartile 15.7 79 5.82 80.8 7.92 0.5

Mean 16.2 79 5.83 81.9 8.06 0.9

Median 16.4 79 5.84 81.7 8.00 0.6

3rd quartile 16.7 80 5.85 82.5 8.20 0.9

Highest value 16.8 80 5.87 86.3 8.52 6.3

Number of observations 723 723 723 723 723 723

Standard deviation 0.0 0 0.00 0.0 0.00 0.0

01409150 Mill Creek near Manahawkin, NJ, growing season, September–October 2010, stormflow

Lowest value 15.6 73 5.25 69.3 6.54 1.1

1st quartile 17.4 76 5.54 73.3 6.91 2.3

Mean 17.6 80 5.56 75.7 7.23 3.9

Median 17.9 79 5.58 74.7 7.08 3.3

3rd quartile 18.2 84 5.64 78.8 7.54 5.1

Highest value 18.6 95 5.79 84.4 8.38 12.9

Number of observations 398 398 398 398 398 398

Standard deviation 0.0 0 0.00 0.0 0.00 0.0
44 Nutrient Concentrations and Nitrate Source Identification, Barnegat Bay-Little Egg Harbor Watershed, NJ, 2010–11

Appendix 1. Summary statistics of continuous water-quality data, Barnegat Bay-Little Egg Harbor watershed, 2010.—Continued

[ ̊C, degrees Celsius; μS/cm, microsiemens per centimeter at 25 ̊C; mg/L, milligrams per liter; NTU, nephelometric turbidity units; --, not available]

Statistic Temperature

( ̊C)

Specific 

conductance 

(μS/cm)

pH

Dissolved 

oxygen 

(percent of 

saturation)

Dissolved 

oxygen 

(mg/L)

Turbidity 

(NTU)

01409281 Westecunk Creek at Railroad Ave, at West Creek, NJ, nongrowing season, March 2010, base flow

Lowest value 9.0 34 4.37 86.9 9.51 0.3

1st quartile 10.1 35 4.42 87.5 9.60 0.4

Mean 10.7 36 4.42 88.4 9.82 0.5

Median 10.6 35 4.43 88.0 9.86 0.4

3rd quartile 11.3 36 4.44 88.5 9.98 0.6

Highest value 12.0 39 4.46 91.5 10.30 4.3

Number of observations 457 457 457 457 457 457

Standard deviation 0.8 1 0.02 1.2 0.23 0.3

01409281 Westecunk Creek at Railroad Ave, at West Creek, NJ, nongrowing season, March 2010, stormflow

Lowest value 7.3 39 4.08 82.2 9.51 0.8

1st quartile 8.2 40 4.10 84.0 9.82 1.5

Mean 8.4 47 4.14 84.9 9.95 2.5

Median 8.5 46 4.13 84.5 9.93 2.1

3rd quartile 8.7 55 4.14 85.6 10.09 3.1

Highest value 9.6 56 4.37 88.2 10.33 14.9

Number of observations 1,259 1,259 1,259 1,259 1,259 1,258

Standard deviation 0.5 7 0.06 1.4 0.20 1.4

01409281 Westecunk Creek at Railroad Ave, at West Creek, NJ, growing season, September–October 2010, base flow

Lowest value 18.2 41 5.18 77.2 7.26 1.0

1st quartile 19.0 44 5.23 81.5 7.53 1.2

Mean 19.3 46 5.27 84.9 7.83 1.3

Median 19.3 46 5.27 84.1 7.76 1.3

3rd quartile 19.7 49 5.30 87.1 8.06 1.4

Highest value 20.0 55 5.46 95.8 8.80 4.5

Number of observations 986 986 986 986 986 986

Standard deviation 0.4 3 0.05 4.2 0.38 0.3

01409281 Westecunk Creek at Railroad Ave, at West Creek, NJ, growing season, September–October 2010, stormflow

Lowest value 19.4 42 5.04 77.2 7.02 1.3

1st quartile 19.9 46 5.16 80.3 7.26 1.5

Mean 20.3 51 5.19 83.9 7.58 1.8

Median 20.5 50 5.19 83.5 7.49 1.7

3rd quartile 20.6 53 5.22 86.5 7.83 2.0

Highest value 21.0 70 5.29 92.0 8.32 3.8

Number of observations 338 338 338 338 338 338

Standard deviation 0.5 5 0.04 4.2 0.37 0.4
Prepared by the West Trenton Publishing Service Center

For additional information, write to:

Director

U.S. Geological Survey

New Jersey Water Science Center

Mountain View Office Park

810 Bear Tavern Rd., Suite 206

West Trenton, NJ 08628

or visit our Web site at:

http://nj.usgs.gov/
Wieben and others—Nutrient Concentrations and Nitrate Source Identification, Barnegat Bay-Little Egg Harbor Watershed, NJ, 2010–11—Scientific Investigations Report 2012–5287