Strategic Assessment
of Near Coastal Waters
Northeast Case Study
Susceptibility and Status of Northeast Estuaries
to Nutrient Discharges
NOAA/EPATeam
on Near Coastal Waters
July 1988
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Strategic Assessment
of Near Coastal Waters
Northeast Case Study
The Northeast Case Study has been undertaken to illustrate how data being developed in NCAA's
program of strategic assessments can be used for resource assessments of estuaries and near coastal
waters throughout the contiguous USA. It was designed as a pilot project to assist the U.S. Environmental
Protection Agency (EPA) in developing its Strategic Initiative for the Management of Near Coastal Waters.
As part of this initiative, the coastal states and EPA are to identify estuarine and coastal waters that require
management action.
The project began in June 1987 as a cooperative effort by NOAA's Office of Oceanography and Marine
Assessment and EPA's Office of Policy, Planning, and Evaluation and Office of Marine and Estuarine
Protection. The Northeast was selected because NOAA's data bases were more complete for the
estuaries of this region at the time. Offshore areas are not included since information to characterize them
has not been organized for a consistently defined set of spatial units.
Preliminary and interim case study reports were completed in September and November 1987. In these
reports, information was compiled by estuary for seven themes: (1) physical and hydrologic
characteristics; (2) land use and population; (3) nutrient discharges; (4) classified shellfish waters; (5) toxic
discharges and hazardous waste disposal sites; (6) coastal wetlands; and (7) public outdoor recreation
facilities. Most of the information was compiled from NOAA's National Coastal Pollutant Discharge
Inventory, National Estuarine Inventory (Volumes 1 and 2), National Coastal Wetlands Inventory, and
Public Outdoor Recreational Facilities Inventory. However, with the exception of the toxic discharges
chapter in the interim report, only cursory explanations of the data and no data analyses were provided in
the previous reports.
Two chapters, nutrient and toxic discharges to estuaries, will be completed to illustrate fully the extent of
available data, the methods used to develop the data, and the types of analyses that are possible. The
data bases used to compile the information in the report are constantly being updated and improved. For
example, during the course of the project, NOAA analyzed the susceptibility and status of all estuaries
identified in its National Estuarine Inventory to nutrient and toxic discharges. This information, not in the
preliminary and interim drafts of the case study, is emphasized in the chapters on nutrient and toxic
discharges with special attention given to the estuaries in the Northeast. Case studies for other regions
may be completed in the future depending on interest and available resources.
Additional information on NOAA's program of strategic assessments is available from:
Strategic Assessment Branch
Ocean Assessments Division
Office of Oceanography and Marine Assessment
National Ocean Service
National Oceanic and Atmospheric Administration
11400 Rockville Pike
Rockville, Maryland 20852
(301) 443-8921
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Strategic Assessment
of Near Coastal Waters
Northeast Case Study
Chapter 3
Susceptibility and Concentration Status
of Northeast Estuaries to Nutrient Discharges
NOAA/EPA Team on Near Coastal Waters
July 1988
Catherine Warsh, John Paul Tolson, C. John Klein
S. Paul Orlando, Charles Alexander, Forest Arnold
Ruth Chemerys, Kristina Groome, Paul Campanella,
Christine Gimmler, Peter Truitt, Charles Minor
Strategic Assessment Branch
Ocean Assessments Division
Office of Oceanography and Marine Assessment
National Ocean Service
National Oceanic and Atmospheric Administration
Rockville, Maryland
Environmental Results Branch
Office of Policy, Planning,
and Evaluation
U.S. Environmental Protection Agency
Washington, D.C.
Robert Biggs, Elizabeth Zolper, Heather Quinn
Tom DeMoss, Mary Lou Soscia, Kathy Minsch
College of Marine Science
University of Delaware
Newark, Delaware
Office of Marine and Estuarine Protection
U.S. Environmental Protection Agency
Washington, D.C.
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CONTENTS
Page
Introduction 1
Background 2
Screening Analysis of Regional Conditions 2
Susceptibility of the Region's Estuaries to Pollutant Inputs 3
The Nutrient Pollutant Status of the Nation's Estuaries 5
Nutrient Sources, Estimation Methods, and Discharges 8
Nonpoint Sources 11
Point Sources 13
Upstream Sources 14
Simple Comparisons by Estuary 15
Concluding Comments 18
Appendices 19
A. Summaries of the Susceptibility and Pollutant Status of the Region's
Estuaries to Nutrients 19
B. Nutrient Discharges by Season by Estuary 38
C. Nitrogen and Phosphorus Discharges by Source Category 41
D. Accuracy of the Discharge Estimates 43
E. Computing Dissolved Concentration Potential 47
References 49
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INTRODUCTION
This chapter of the Strategic Assessment of Near Coastal Waters: Northeast Case Study is an
assessment of the susceptibility and concentration status of 17 Northeast estuaries to nutrient-
related pollution problems. It is the final version of one of seven chapters in the Case Study and
one of two chapters that will be completed. It first presents background information on the
problems of nutrient overenrichment in estuaries followed by a screening analysis of the
susceptibility and status of estuaries to nutrient discharges and sections on nutrient sources and
discharge estimation methods. The final section is an overview of the region based on simple
comparisons of discharge estimates across estuaries in the region. Appendix A contains one-
page summaries for each estuary that include information on significant physical and hydrologic
features, susceptibility and pollutant status, nutrient discharge estimates, and a narrative to assist
the reader interpret the data. Summary estimates of particular interest are the changes in nitrogen
and phosphorus inputs that would significantly alter the pollutant status of each estuary. Four
additional appendices contain more detailed breakdowns of nutrient discharges by season and by
source, an evaluation of the quality of the discharge estimates, and the method for determining an
estuary's nutrient concentration status and susceptibility to nutrient-related pollution problems.
The susceptibility and concentration status of estuaries to nutrient-related pollutant problems
are recent additions to NOAA's National Estuarine Inventory. They are the syntheses of several
years of work to characterize comprehensively the physical and hydrologic features of the Nation's
estuaries as they affect the retention and distribution of pollutant inputs. Susceptibility and
concentration status are significant additions to the data included in the preliminary and interim
drafts of this case study. This information serves as a screening device for evaluating the
condition of estuaries relative to one another with respect to nutrient inputs and their potential
effects. Public agencies responsible for managing resources, environmental quality, and
activities in these areas can use this information to better direct resources toward estuaries that
require management action. More detailed interpretation of this material is being developed in
two forthcoming NOAA reports: "Estuarine Pollution Susceptibility" and "Estuarine Classification
with Management Application."
Data in the case study are organized by estuarine drainage area (EDA), the land and water
component of an entire watershed that most directly affects an estuary. EDAs are delineated
based on the limits of tidal influence within an estuarine system and the boundaries of U.S.
Geological Survey hydrologic cataloging units. A hydrologic cataloging unit is a geographic area
representing all or part of a surface drainage basin or a distinct hydrologic feature. EDAs generally
coincide with hydrologic cataloging unit(s) that contain the heads of tide and seaward estuarine
boundaries. However, many of the EDAs in the Northeast bisect the hydrologic cataloging units.
The 17 estuaries in the region contain over 26,000 square miles of EDA of which about 3,900
square miles are estuarine surface waters with a volume of 6.5 trillion cubic feet. Fifty-seven
counties fall entirely or in part within one or more of the EDAs. The estuaries receive over 95,000
tons per year of nitrogen and over 18.000 tons of phosphorus from point, nonpoint, and
upstream sources. Only one of these estuaries is estimated to have high concentrations of both
nitrogen and phosphorus based on its dissolved concentration potential and nutrient discharge
received; seven are estimated to have low concentrations. The rest of the estuaries share a mix of
high, medium, and tow concentration values for nitrogen and phosphorus.
The information and analyses in this chapter are not definitive assessments of the condition of
estuaries in the Northeast with respect to nutrient discharges and concentration. As screening
devices, they can only suggest which estuaries are likely to be susceptible to nutrient-related
pollution problems and the order-of-magnitude changes in nutrient discharges that are likely to
affect the nutrient concentration status of these estuaries. This is important in program-level
decision-making when determining which estuaries should receive a more detailed analysis of
their condition or which estuaries should receive priority attention.
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BACKGROUND
Estuaries make up less than one percent of the ocean environment, yet they are the most biologically
productive. Part of this productivity is directly related to nutrient cycling that supports phytoplankton
growth, the base of the food chain. The nutrients nitrogen and phosphorus are essential elements for
the healthy growth of aquatic plants and generally stimulate the productivity of an estuarine system.
However, excess discharges of either or both of these nutrients to receiving waters generally leads to
eutrophication, particularly in estuaries with poor flushing characteristics, and can be a deterrent to growth
and productivity of naturally occurring species. The most visible effect of eutrophication is the massive
blooms of phytoplankton that can clog rivers, reduce light penetration, and emit noxious odors due to the
decay of dead organisms. A major ecological impact of eutrophication is the depletion of dissolved
oxygen (hypoxia) that can occur in bottom waters due to decay of algae as they die and sink. Hypoxia is a
condition that occurs when levels of dissolved oxygen in bottom waters are less than 2 milliliters per liter.
This,' in turn, can lead to mass mortalities of finfish and shellfish. The most recent case in the Northeast
occurred in Long Island Sound during the summer of 1987. Nutrient enrichment, combined with high
temperatures, resulted in massive blooms of phytoplankton (green tide), bottom waters devoid of
dissolved oxygen, and large fish kills. The flushing rate, circulation, stratification, and wind field are all
important factors influencing the duration, magnitude, and extent of eutrophic conditions in estuaries.
Wastes, including excessive nutrients, have entered marine waters for centuries directly or indirectly
by way of rivers, runoff, rainfall, atmospheric deposition, and end-of-pipe discharges. The magnitude of
this problem for Northeast estuaries is illustrated by the nutrient discharge data presented in this chapter.
Until recent years, the oceans seemed to have had the capacity to assimilate thes'e wastes. While this may
still hold true for the deep oceans, this is not the case for estuarine and coastal ocean waters. Increasing
evidence of reduced fish catches, loss of habitats, and degradation in water and sediment quality resulting
from nutrient overenrichment has shown that we are faced with hard management decisions concerning
our ability to limit these discharges.
In a nationwide survey conducted in 1985 to identify the estuarine and coastal areas with eutrophic
and hypoxic conditions around the country (Whitledge, 1985), the western end of Long Island Sound
was classified as an area of priority concern, and Narragansett Bay was classified as a potential problem
area. The western end of the Sound has a history of acute and persistent depressed oxygen, particularly
near the East River. Heavy loading from municipal wastewater treatment plants (WWTPs) in the East River
seems to be responsible for depressed oxygen values throughout the year. In the past, some of the bays
in the western Sound have had serious eutrophication and hypoxic episodes because of the large
amounts of nutrient runoff from the duck farm industry. These conditions have improved as the duck farm
industry has declined. The upper end of Narragansett Bay in Rhode Island shows evidence of recurring
low dissolved oxygen. Circulation is sluggish in this area, and nutrient input is high, but there were
insufficient data to draw any conclusions about the persistence of hypoxic episodes. Other problems,
such as fish kills or high bacteria counts that occurred in high nutrient areas, were also identified. Episodic
events posing little potential for long term impacts, occurred throughout the region. A summary of the
problems that have occurred in the estuaries of the Northeast is given in Table 1.
SCREENING ANALYSIS OF REGIONAL CONDITIONS
This section presents an assessment of the status and susceptibility of 17 estuaries in the Northeast
to nutrient-related pollution problems. A classification scheme was developed for 82 estuaries nationwide
identified in NOAA's National Estuarine Inventory (NEI) to assess the contribution of human activity to
nutrient overenrichment, or eutrophication, in coastal and marine waters (Klein, et al, 1988). The
classification scheme is comprised of three elements: 1) dissolved concentration potential (DCP), the
ability of an estuary to concentrate dissolved substances; 2) particle retention efficiency (PRE), an
estuary's ability to trap suspended particles and their associated pollutants; and 3) concentration status.
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Table 1. Documented water quality problems related to nutrient discharge for the Northeast
Estuary
Problem
Probable Cause
High
Nutrients
low
DO
Fish
Kills
Other
Problems
Severity
Episodic Potential Priority
PassamaquoddyBay x
Narraguagus Bay x
PenobscotBay X
Input tram Ocean X
Combined sewage, high runoff Conform bacteria X
WWTPs X
CasooBay
Merrlmack River
X
X
WWTPs
Industrial discharge
WWTPS
Hlghhydr
sulflde
Massachusetts Bay
Buzzards Bay
Narragansen Bay
Long Island Sound
XXX WWTPs
X X High runoff, high temperature Excessive metals X
X XX High runoff, poor circulation
X X WWTPs. snrmwater. CSOs High chlorophyll
Collform bacteria
X
X
X
Abbreviations: Dissolved oxygen. DO: Municipal wastewater treatment plants. WWTPs; Combined sewer overflows. CSOs.
an inferred level of pollutants in an estuary. Comparisons of these characteristics among estuaries
are valid in a relative sense only and do not reflect actual concentrations of nutrients that may
be found in estuaries. They were derived by using physical and hydrologic data from NOAA's NEI and by
using pollutant discharge estimates from NOAA's National Coastal Pollutant Discharge Inventory (NCPDI).
Dissolved concentration potential, inferred nitrogen and phosphorus concentration status, total nitrogen
and phosphorus discharges, and physical and hydrologic data for the 17 estuaries in the Northeast are
summarized below.
Susceptibility of the Region's Estuaries to Pollutant Inputs. Pollutants exist in estuaries either in dissolved
or paniculate form in the water column or in bottom sediments. Nutrients are generally in dissolved form,
although nitrogen and phosphorus can be associated with sediment particles. The pollutant susceptibility
of an estuary is its relative ability to concentrate both dissolved and participate substances. Pollutant
susceptibility is plotted for each of 82 estuaries included in NOAA's NEI, including 17 in the Northeast
region, based on their dissolved concentration potential and particle retention efficiency (Figure 1)
(discussed below). Class I estuaries are the most susceptible to pollution problems because pollutants
are not readily diluted or flushed and sediment-associated toxic substances are most likely to be trapped
within the estuary. Five estuaries in the region, Muscongus, Gardiners, Narraguagus, Blue Hill, and
Buzzards Bays, are Class I estuaries. Class IX estuaries (none in the Northeast) are the least susceptible to
pollution problems. Other classes of susceptibility such as II and IV, which includes Great Bay and
Merrimack River in the Northeast, have high dissolved concentration potential but low particle retention
efficiency, suggesting that they are more susceptible to dissolved pollutants than sediment-attached
pollutants.
Dissolved concentration potential characterizes the effect of dilution and flushing on a load of a
dissolved pollutant to an estuary. It is interpreted as an average concentration potential throughout an
estuary under steady-state conditions but does not reflect site-specific conditions. DCP values in
conjunction with nutrient discharge estimates were used to determine the concentration status of
nitrogen and phosphorus in the 17 Northeast estuaries.
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DCP was calculated based on a fractional freshwater method for predicting the concentration of a
pollutant (Ketchum. 1955). It was derived from the replacement of the freshwater component of the total
estuary volume due to inflow. Computations for each estuary were based on average annual freshwater
inflow and salinity. An equal pollutant load was assumed to be discharged to all estuaries. This provided a
relative indicator for comparing an estuary's ability to concentrate a pollutant with others. Each nutrient
was treated as a conservative pollutant and assumed to be uniformly distributed within each estuary. A
high DCP indicates low dilution or flushing capability and high susceptibility to impacts from pollutant
inputs. Values between 0.01 and 0.1 milligrams per liter indicates a low DCP; 0.1 to 1.0, medium; and 1.0
to 10.0 high. These categories are based on order-of-magnitude differences in DCP values. The method
of calculating dissolved concentration potential is discussed in Appendix E.
Figure 1. Relative susceptibility classification
10-
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0.01 •
0.001 -
LOW
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BUZ Buzzards Bay
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OCB Cape Cod Bay
B4S Englishman Bay
GAR Gardiners Bay
CRT Great Bay
LIS Long Island Sound
MAS Massachusetts Bay
MER Mernmack River
MUS MuscongusBay
NAR Nairagansett Bay
MS Narraguagus Bay
PAS Passamaquoddy Bay
PEB Penobsoot Bay
SfC SaooBay
SHE SheepscotBay
0.01
0.10 1
Dissolved Concentration Potential (mg/1)
10
Abbreviations: C. Volume of estuary at mean sea level; I. annual volume of freshwater
inflow: mg/l. milligrams per liter
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Of the 17 estuaries in the region, seven have a high DCP; eight, medium; and two, low. Those with a
high DCP, Narraguagus, Blue Hill, Muscongus, Great, Buzzards, and Gardiners bays and Merrimack River,
receive about 18 percent of total nitrogen discharge and about 14 percent of the total phosphorus
discharge in the region. They account for 18 percent of the estuarine resource base in the Northeast as
measured by estuarine surface water area, or about 11 percent as measured by estuary .volume.1 Those
with a low DCP, Sheepscot Bay and Long Island Sound, receive 59 percent of the total nitrogen
discharge and nearly 44 percent of total phosphorus discharge, and comprise over 33 percent of the
estuarine resource base in the region. In general, the estuaries with a high DCP have less volume than
those with medium or low DCP. For example, Muscongus Bay, with the eighth smallest volume, is
estimated to have the highest dissolved pollutant concentration potential in the region, indicating that, on
average, this estuary experiences a relatively low degree of flushing or dilution. Long Island Sound, by
contrast, has the largest volume and a DCP that indicates a system with a high dilution capacity.
Particle retention efficiency (PRE) characterizes the ability of an estuary to trap suspended particles
and their associated pollutants. Toxic substances are generally attached to suspended sediments,
although some forms of nutrients also can be attached. The PRE estimate is based upon an empirical
relationship developed for artificial freshwater impoundments that has been demonstrated to be
applicable to estuaries (Biggs and Howell, 1984). It is inferred from the ratio of estuary volume to the total
annual volume of freshwater that enters an estuary. A high particle retention efficiency indicates high
susceptibility to retaining toxic inputs. The issue of toxic pollutants in estuaries of the Northeast is treated
separately in the chapter on toxic discharges in this case study. The concept of PRE is presented here
because it is an element in determining the overall pollutant susceptibility of estuaries.
The Nutrient Pollution Status of the Region's Estuaries. Figures 2 and 3 show the estimated nitrogen
and phosphorus concentration status for the Northeast estuaries. Concentration status is interpreted as
the relative condition of estuaries with respect to nutrient load and DCP and identifies those estuaries that
would most likely benefit or suffer from changes in nutrient discharge. Both DCP and discharge are
shown on a log-log scale. Diagonal lines on the figures show regions of relatively low, medium, and high
concentrations. These concentrations are useful for describing potential nutrient problems from
discharges from human activities. They do not account for nutrients made available by recycling within an
estuary, atmospheric deposition, or oceanic inputs, which, in some cases, may be substantial. In each
figure, the slope of the concentration zones demonstrates that estuaries with low nitrogen loadings, such
as Gardiners Bay, can achieve medium concentrations given a high DCP. Estuaries with a relatively high
nitrogen loading, like Sheepscot Bay, may exhibit low concentration if they have a low DCP.
Concentration values of less than 0.1 milligram per liter of nitrogen and 0.01 of phosphorus indicate a low
nutrient concentration status; 0.1 to 1.0 for nitrogen and 0.01 to 0.1 for phosphorus, a medium
concentration status; and greater than 1.0 for nitrogen and 0.1 for phosphorus, a high concentration
status.
These approximate the values developed for the Chesapeake Bay Environmental Quality
Classification Scheme (U.S. EPA, 1983a). This scheme relates levels of nutrients (among other
parameters) to observed resources. A low concentration status supports maximum diversity of benthic
resources, submerged aquatic vegetation, and fisheries; medium concentration supports moderate
diversity and results in reduction of submerged aquatic vegetation, and occasionally high chlorophyll
levels; high concentration results in a significant reduction in resource diversity, loss of submerged
aquatic vegetation, frequently high levels of chlorophyll and occasional red tide or algal blooms.
The best way to assess the condition of estuaries based on concentration status is to determine their
relative position in Figures 2 and 3 and to estimate the approximate amount of discharge required to
change their classification, keeping in mind the log-tog scale used to show nutrient discharge and DCP.
(The amount and percentage change in nitrogen and phosphorus discharge necessary to move each
estuary in the region from one concentration status classification to the next higher or lower classification
is given in the individual estuary summaries in Appendix A.)
1 Estuarine resource base can be measured by any number of estuarine characteristics.
Estuarine surface area is used here because it is an easily understood and highly visible estuarine
attribute.-
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Figure 2. Nitrogen concentration status
1.000,000
0.01
0.1
Dissolved Concentration Potential (mg/1)
Concentration (mg/l)
LOW MEDIUM HIGH
S3 Less than 0.1 HO Greater than 0.1 D Greater than 1
and Less than 1
Figure 3. Phosphorus concentration status
100.000
10,000
f
I
PAS
NRS
BHB
PEB
MUS
SHE
CAS
SAC
CRT
MER CD
MAS am
CCS
BUZ
MAR mn
GAR mmn
us mn
1000 -
100 -
0.01
Dissolved Concentration Potential (mg/l)
Concentration (mg/l)
LOW MEDIUM HIGH
li Less than 0.01 M Greater than 0.01 D Greater than 0.1
and Less than 0.1
PAS
BJ3
NRS
BHB I
PEB nnnu
MUS BBS
SHE BSB
GAS imiiii
SAC
CRT
rvER
MAS
CCB
BUZ mnn
MAR mm
LIS DUD
6
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Generally, estuaries with a low concentration status and low DCP require addition of nutrients
significantly greater than estuaries with a medium or high DCP to achieve a high concentration.
Sheepscot Bay. for example, would require an increased phosphorus load of more than 10,000 tons per
year before it could be classified as an estuary with high concentration status according to this scheme.
Estuaries with a low concentration status but high DCP, such as Blue Hill, Muscongus, and Narraguagys
bays, are probably not experiencing systemic problems of overenrichment. However, each would require
an increase of as little as 1,000 tons per year phosphorus to reach a high concentration status and
perhaps experience an overenrichment condition. To change the nitrogen concentration status of Long
Island Sound (low DCP) from medium to low would require a decreased discharge of nearly 32,000 tons
per year. However, to change an estuary with a high DCP with the same concentration status, such as
Gardiners Bay, would require a reduction of only about 400 tons per year. In general, estuaries with a low
DCP are less sensitive to changes in concentration status due to changes in nutrient inputs.
The concentration status of most estuaries in the region is similar for both nitrogen and phosphorus
(Table 2). Most estuaries that have a low nitrogen concentration status also have a low phosphorus
concentration status. The Merrimack River is the only system with a high concentration status for both,
accounting for nearly 9 percent of the phosphorus discharge and over 10 percent of the nitrogen
discharge in the region. However, it comprises less than one percent of the estuarine resource base as
defined by estuarine surface area. Massachusetts Bay is the only other system with a high concentration
status for phosphorus and represents an additional 24 percent of the discharge from the region into this
water body. Four estuaries with medium concentration status for nitrogen and phosphorus-Long Island
Sound, Narragansett, Gardiners, and Penobscot bays-receive 65 percent nitrogen and 56 percent
phosphprus discharge and account for nearly 52 percent of the estuarine resource base in the region.
Seven estuaries-Saco, Sheepscot, Blue Hill, Muscongus, Englishman, Narraguagus, and
Passamaquoddy Bays-share a low concentration status for both nitrogen and phosphorus. Collectively,
they account for about 11 percent of the nitrogen discharge, 5 percent of phosphorus, and about 16
percent of the estuarine resource base in the region.
Table 2. Summary of physical and hydrologic characteristics, dissolved concentration potential, nutrient discharges, and concentration status
Estwiy
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361
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165
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Anthropogenic contributions of nutrients alter the natural balance of the nutrient cycle and have
become a major concern in coastal and estuarine waters. A serious problem in assessing the extent of
eutrophication in these waters is the absence of quantitative and standardized long-term data on nutrient
discharges to marine waters and long-term measurements of nutrient concentrations within waterbodies
themselves. However, in absence of these data, pollutant susceptibility and inferred concentration status
provide a reasonable first cut at ranking estuaries according to their susceptibility to pollution effects. This
characterization distinguishes estuaries that have greater or lesser capacity to moderate pollutant inputs
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based upon dilution and flushing. This is important in establishing management strategies and program
priorities for estuaries that exhibit various degrees of responsiveness to pollutant inputs.
The remainder of the chapter contains the nutrient discharge estimates to the 17 estuaries in the
region and information on the sources of discharge and methods used to estimate discharge. This is
important background information necessary to understand the data used in determining nutrient
concentration status.
NUTRIENT SOURCES, ESTIMATION METHODS, AND DISCHARGES
Figure 4 shows estimated total nitrogen and phosphorus discharges by estuarine drainage area (EDA)
for each estuary. The estimates include organic and inorganic forms of each nutrient and are estimated as
"total nitrogen" and "total phosphorus" and are taken from NOAA's National Coastal Pollutant
Discharge Inventory (NCPDI). The estimates are based on a combination of monitored and estimated
data, circa 1982. Annual discharge estimates for each nutrient by source category are listed in Table 3;
seasonal estimates are presented in Appendix B; estimates by source categories are listed in Appendix C.
Discharge estimates by source categories are only for the coastal county portion of an EDA. Discharges
for those portions of the EDA outside the coastal county boundary and for the area outside of the EDA are
reflected in the upstream source discharge estimates. No estimates were made of nutrients contributed
by atmospheric deposition or exchange between estuaries and ocean through surface transport seaward
and bottom transport landward. For the 17 estuaries in the Northeast, 12 percent of the estimated
nutrient discharges are from nonpoint sources; 41 percent are from point sources, and 46 percent are
from upstream sources.
The methods used to estimate nutrient discharges for each category are described briefly below.
Detailed explanations of the estimation methods are contained in the NCPDI Methods Documents
available from NOAA's Strategic Assessment Branch (1987). Selected information used to estimate
nutrient discharges such as land area, precipitation, fertilizer applications, and number of WWTPs is
provided as background information in Table 4. An assessment of the quality of discharge estimates and
background information is given in Appendix D.
Estimates represent "end-ol-plpe" point source discharges and nonpoint runoff Into rivers, streams,
and creeks that eventually may enter the estuary. They do not take Into account the transport, deposition,
and chemical cycling of nitrogen and phosphorus In the water column which affect ambient levels of
nutrients In estuaries. A direct connection Is not made between nutrient discharge estimates and ambient
concentrations In an estuary. However, the estimates do reflect the net addition of nutrients from human
activities and are Important for evaluating the relative contributions of different sources (Table 5).
Natural Sources. Natural sources of nitrogen and phosphorus are runoff from forests, wetlands,
natural soil erosion, atmospheric and oceanic exchange, groundwater, and weathering. Both the nitrogen
and phosphorus cycles are open systems in marine waters. Biological processes of uptake, decay, and
regeneration determine the concentrations of these nutrient compounds, and physical factors, such as
sinking of dead organisms and upwelling, determine the distribution. Phosphorus is generally the limiting
nutrient in freshwater and nitrogen is the limiting nutrient in seawater; estuaries represent a transition
zone from fresh to seawater.
Both nitrogen and phosphorus occur in organic and inorganic forms. Nitrogen is found in water as
dissolved molecular nitrogen and as inorganic and organic compounds. The inorganic forms of nitrogen
are nitrate, nitrite, and ammonia-nitrate being the most abundant. Organic nitrogen compounds are either
dissolved or paniculate forms. Inorganic phosphate occurs primarily as orthophosphate in sea water.
Another inorganic form found only in estuarine waters is polyphosphate ions from detergents (Riley and
Chester, 1971). Organic phosphorus in marine waters is also found in dissolved or paniculate forms and
is derived mostly from decomposition and excretion of marine organisms.
8
-------
Passamaquoddy Bay
ft
Englishman Bay
Narraguagus Bay
Blue Hill Bay
Penobscol Bay
MusoongusBay
SheepscotBay
Casco Bay
Discharge in Coastal Counties
(tons/year)
Great Bay
Mernmack River
Less than 1.000
1.000 to 7.500
Massachusetts Bay
Cape Cod Bay
SSl 7.500 to 15,000
[i|!| Greater than 15.000
Upstream Source
Inland EDA Boundary
- Narragansett Bay
Gardners Bay
figure 4. Nitrogen and phosphorus discharge in the coastal county portion of estuarine drainage areas, drca 1982
The methods used to calculate discharges from urban (NOAA, I987d) and nonurban (NOAA, 1987a)
sources are described briefly below. Land use data common to both categories were derived from the
USGS Land Use and Land Cover (LU/LC) Classification System (Anderson et al, 1976) and the U.S.
Department of Agriculture's (USDA) Soil Conservation Service 1982 National Resource Inventory (USDA,
1982). Precipitation and other weather data were obtained from the National Weather Service.
-------
Table 3. Nutrient discharges to Northeast estuaries (tons per year) • drca 1982
Otur
ToU
WWTP»
Induity
Tetri
PooMnoquoddyB*
EnSrtminBn
Nmgu.gu.Bn
BhMWI Bay
PvnoMoot Bey
MumngnBqr
BhupieolBty
CM.BV
SuoBn
Cntl Boy
HwnnAdi Hivor
MMOMhuioaBoy
CopoCodBr,
BUM* Boy
MfragonMll Boy
QoRinor>B>y
Long blond Sou*
M
os
02
it
M
27
251
107
M
IM
U
64
3
U
145
tH
1.027
6 19
1 IS
i a
i to
4 147
2 0
14 12
11 30
2 2
7 4
4 0
1 271
0 0
1 0
17 1
4 0
30 Ot
00
42
20
77
143
17
100
270
133
227
531
1.440
100
124
1.303
103
1.030
14 1
7 2
3
13
23
3
32
4S
22
30
M
230 40
17
20
217
20
000
102 10
124 10
03 0
107 14
352 20
44 0
474 40
007 00
in 24
307 43
014 N
1.014 240
111 17
101 21
1.711 234
341 33
0.020 020
10 11
17 12
0 0
30 21
77 07
13 10
07 02
400 273
140 101
230 103
1.310 814
0.100 3.044
207 100
300 111
2.470 1.540
021 301
10.022 4.000
04 0
10 1
0 0
10 2
M 4
1 0
10 0
143 140
17 10
13 7
37 2
IS 1
0 0
0 0
Ml 4
10 10
1.071 20
IK 13
27 11
11 0
40 21
170 01
14 10
77 12
701 411
100 110
241 100
1.347 BIO
0.101 1.040
207 100
101 103
2.001 1.544
044 407
10.001 0.000
0 0
0 0
0 0
0 0
7.200 OH
0 0
1.100 041
0 0
070 OS
0 0
1.1SO 722
0 0
0 0
0 0
0 0
0 0
24.027 1.000
204 32
101 21
100 12
I5S 37
7.000 77S
00 tS
1.741 041
1.410 471
1.2S4 IM
040 203
10.1H 1.020
7.000 4.001
100 10S
401 210
4.S74 1.770
•85 440
00.140 7.S27
320
174
110
102
0.001
71
1.312
t.000
1.440
04]
11.730
12.000
505
015
0.352
1.42S
07.070
tool
3.667 121 goo
0.000 1.105 02 1 12.020 1.524
11.000 12.020 2.150 21J 0X230 12.040
49,122 1.005
05.207 10.200 1I1.SSO
AbbnMtaMM Ninon. N; Phoophonio. P: MunW* xulM.lv twnnl pint., WWTPo
Table 4. Factors Influencing nutrient discharges to Northeast estuaries • circa 1982
Could
EM County (1)
PooMnoqMxMyBoy(l
EngUthm.fi Boy
NmguogwBoy
BluoHO Boy
PoMbocoiBoy
Hmoongu.Boy
ShoopoMBoy
CoonBoy
SoeoBoy
OioolBoy
Uommock Him
MouochuMttBoy
OtoCodBqr
BuuordoBoy
NarragmMtt Boy
Qordnor. Boy
Long hind Sound
TaM (4)
) 1.320
700
372
000
2.700
404
0.030
070
1.723
000
2.177
1.004
213
334
1.151
203
0.003
20.170
1.220
700
372
507
002
404
020
027
530
030
005
1.004
213
354
1.151
203
2.773
11.407
(02)
(100)
(100)
(07)
(35)
(100)
(to)
(04)
(05)
(30)
(100)
(100)
(100)
(100)
(100)
(40)
-
Winter S
11 2
105
105
00
04
102
00
00
00
04
07
00
too
11 0
100
124
100
04(4)
•ling Bumnm Fol
02
SO
00
01
oo
03
00
107
87
0 3
02
02
01
00
00
11 3
105
00
14 0
123
123
104
11 1
131
17 0
127
137
13 0
14 0
10 0
100
14 4
too
too
10 7
130
00
87
07
00
07
00
7 1
74
78
00
102
00
11 2
121
11 1
07
77
02
long Turn
Ang Anmiol
442
442
442
....
400
....
....
400
41 0
400
411
440
41 7
421
433
410
" ™ " "
427
Foniior AppOooOn to
CaMlal &•«••• JlMMAMrt IM
Cooraf Count*
fa EDA
0
1
1
2
11
0
7
17
10
10
7
0
2
3
20
4
72
201
N
170
122
its
74
300
220
072
020
818
400
404
220
7
400
1.031
250
0.045
12.221
70
58
81
33
172
100
200
233
227
100
130
00
2
113
307
03
1,001
3.020
ToMfa
EDA
100
122
113
74
2.700
220
3.000
000
058
too
1.100
220
7
400
1.032
288
0.045
10.220
K
03
OS
51
33
1.214
too
1.704
200
200
003
144
00
2
IIS
300
04
1.001
0.070
AohnMoino Eogjomo Dnmoao Ano. EDA. Mtaon. M Phooohomo. P. WWTPo. WoMowokv MoMwit otank
(I) NumtamhpirnOiwMnipmnlolMriEDA.
(2) Fortbnr Appfotoi to pnMWdhr EDA not IndudM fa eoMHI count*.
(1) EOA tad VMOYM IK* Mix). Cmdm ponton olEOA
(4) Pnapitelln vahiM wo rang* nbn
-------
Nonpolnt Sources. Nonpoint source discharge is the transport of dissolved and paniculate materials to
surface waters via surface runoff from precipitation. The nutrients are transported to surface waterbodies
through direct overland flow, storm sewers, and stream channels. Nonpoint discharges are divided into
four categories: agriculture, forest, urban, and other. Nonpoint source discharge has been estimated to
account for 50 percent of water pollution in the USA (Barton, 1978). In addition to estimated discharges in
the coastal county portion of Northeast estuaries, significant nonpoint source discharge is also reflected in
the upstream source category. In the Northeast, six estuarine systems are estimated to receive more than
500 tons/year of nutrient discharges from nonpoint sources in coastal counties or about 89 percent of the
total discharge. Three receive greater than 1,500 tons/year accounting for 70 percent of the total. Urban
and agriculture lands are the major contributors to nonpoint source discharges, the estimated discharge
from urban lands being approximately twice that of agriculture lands (Figure 5).
Table 5. Nutrient sources for marine waters
Nutrient
Phosphorus
Inorganic
Organic
Species
Sources
Nitrogen
Inorganic
Organic
Nitrate
Nitrite
Ammonia
Dissolved
Particulate
Rain, fertilizers, nitrification of nitrite
Bacterial nitrification from ammonia, nitrate reduction
Rain, sewage, animal excretion, bacterial reduction
Sewage, plant tissue
Sewage, excretion, organism death
Orthophosphate Sewage, autolysis, rock weathering, animal excretion, fertilizers
Polyphosphate Detergents (found in estuarine waters)
Dissolved Sewage, plant tissue, excretion of extracellular metabolites
Particulate Organism death, excretion
Agriculture. Agriculture includes irrigated and non-irrigated cropland and pasture land. These areas are
most likely to yield high nutrient discharges due to the exposure of soil for farming practices. In addition to
the nutrients naturally occurring in the organic portion of the soils, fertilizers are applied to the land
surfaces and are readily available for runoff. Factors that influence the amount of runoff and discharge of
nutrients are soil cover, soil moisture and texture, mode of fertilizer application, management practices,
precipitation pattern, and slope. These vary within a watershed between sites and may change with time
for a single plot of land.
Nitrogen and phosphorus discharge estimates for agriculture lands are based on two sources: 1)
soluble nitrogen and phosphorus from chemical fertilizers; and 2) organically bound nitrogen and
phosphorus in sediment discharges. The predominant source of nutrient discharges from agriculture in
the Northeast are from chemical fertilizers. Actual discharge data for these nutrients were estimated by
determining the annual fertilizer use in each coastal county, based on information from state and county
extension agents of the USDA and the percent of fertilizer applied each season. Total cropland acreage
for each coastal county and corresponding USGS cataloging units were computed using USGS land use
data. Fertilizer application was then distributed according to the percent of total cropland in each
cataloging unit. Runoff for each nutrient was determined by multiplying the amount of fertilizer applied by
an average runoff coefficient developed from field plot studies. Separate runoff coefficients were used
for conventional and conservation tillage.
To estimate runoff of organically bound nitrogen and phosphorus from sediment discharges, the
Simulator for Water Resources from Rural Basins model (SWRRB), developed by the USDA (Dalton,
Dalton and Newport, 1984; Williams and Nicks, n.d.), was used. This is a daily simulation model used to
estimate moisture accounting and applied to average site conditions by crop at the subbasin level to
model runoff and soil erosion. It predicts tons per acre sediment yield by crop type under different soil
credibility, slope, cover, and management conditions. The sediment-attached nutrient discharges
11
-------
determined by calculating soil erosion using the SWRRB model were multiplied by an enrichment ratio
(soils enriched with a pollutant and equal to the ratio of the concentration of the pollutant in the eroded soil
to the concentration of the pollutant in situ) and the percent organic matter of dominant soil type being
modeled.
Figure 5. Nutrient discharges by source category for the Northeast
60000
o
soooo
40000
30000
20000
10000
• Nitrogen
CD Phosphorus
Agriculture Forest Urban Other POTWs Industry Upstream
Nonpoint
Point
Nutrient discharge from agricultural lands in the coastal counties make up about 26 percent of the
nonpoint source estimates. For the coastal county portion of the EDAs, Long Island Sound receives the
largest input of nutrients from agricultural lands. However, a closer took at those portions of the EDAs not
contained within the coastal county and the fertilizer applications prorated to those agriculture lands
outside the coastal counties (Table 4) shows that discharges from this category are potentially far greater
than estimated and should be reflected in large upstream estimates. This appears to be the case for
Penobscot Bay, Sheepscot Bay, and the Merrimack River. In each case, the prorated fertilizer applications
outside the EDA is 7, 6, and 2 times that applied within the coastal county. Casco and Narragansett bays
receive the second largest inputs from agriculture discharges from the coastal counties. The amounts are
small compared to Long Island Sound. However, eutrophication problems are documented in both of
these bays, particularly Narragansett Bay.
Forest. Forest lands can be either deciduous, coniferous, or mixed, with soil cover ranging from good to
poor. Forests generally undergo very small amounts of natural erosion with little or no effects on estuarine
environments. The nutrient contributions to surrounding waterbodies is small in comparison to agriculture
or urban sources unless forests are intensely managed to produce wood products.
The SWRRB simulation model was used to calculate runoff for nutrient discharges from forest lands.
The runoff is organic, sediment-attached nitrogen and phosphorus; these nutrients are bound to the soil
particles and transported in the solid phase with eroded sediment. Nutrient discharge from forest land is
tow compared to the other nonpoint source categories. The heavy vegetation of forests stabilizes soils,
reducing soil erosion and providing efficient forest nutrient cycling and tow nutrient discharge from surface
runoff.
Nutrient discharges from forest lands for the Northeast are small compared to other categories. The
estimated total nutrient discharge from forest lands is only 2 percent of the total for the nonpoint source
category primarily from the EDAs in Maine. Runoff from forest lands is a minor source of nutrient
discharges to Long Island Sound. Forest land constitutes the dominant land use for most of the EDAs in
Maine, with less than 5 percent land area used for urban. The largest nutrient contribution from forest land
is in the Penobscot Bay EDA.
12
-------
Urban. Although urban runoff has been recognized for many years as a significant source of water
degradation, pollution from this source remains difficult to measure. This is due to the intermittent and
highly variable nature of storm events, the land use diversity in urban areas, and the varied sewer systems
in an area. Urban areas greater than 2,500 population were considered in this analysis. There are five land
use categories for urban areas: 1) commercial, 2) residential, 3) industrial, 4) mixed, and 5) open. The
urban source category is divided into two subcategories: Combined sewer overflows (CSOs) and non-
combined sewer overflows (Non-CSOs). Combined sewers convey both sanitary sewage and stormwater
runoff. When the capacity of the WWTP and conveyance system serving these combined sewers is
exceeded, the resultant overflow of untreated sewage and stormwater becomes an important discharge.
CSO is a major problem in many older urban areas, particularly in the Northeast. Non-CSOs are those
urban areas with separate storm sewers and sanitary systems.
Runoff from urban areas is a function of precipitation, the extent of impermeable surfaces, and the
type of stormwater collection system. For each urban area, runoff coefficients were computed to estimate
the amount of water that runs off the surface of an urban land use type given a unit of precipitation. Runoff
coefficients were than applied to the time pattern and amount of precipitation to estimate the amount of
stormwater runoff typically discharged to surface waterbodies in the spring, summer, fall, winter, and over
the entire year. The amount of pollutants contained in the runoff were estimated using data obtained from
EPA's National Urban Runoff Program (US EPA, 1983b). The discharge estimates of any given urban
area equaled the seasonal runoff volume by land use type times the specific nutrient concentration value.
The runoff volume was computed daily and aggregated by season. These were then summed for each
EDA for each season to give an annual discharge.
CSO discharges are calculated as part of urban runoff, but are treated somewhat differently because
stormwater entering a waterbody may be processed through a WWTP or may by-pass it and be discharged
directly to receiving waters without treatment. It is this excess CSO volume and associated nutrient load
that is considered as the CSO discharge. Discharge estimates are computed by multiplying the estimated
volume of overflow by typical pollutant concentrations that are specific to CSOs. These concentrations
were averaged from a number of regional studies. Because a sewer system receives flow over a time
interval (depending on the intensity and duration of a rain event, precipitation, runoff) combined sewer
stormwater flow and CSO are calculated in half-hour time steps instead of daily intervals for general urban
runoff. These, in turn, are added for the day, season, and ultimately, the year.
Urban land nutrient discharge estimates are about 72 percent of the total nonpoint source estimate.
The Long Island Sound EDA has the greatest input; 25 percent of the land use in this EDA is urban land
area. Massachusetts Bay and Narragansett Bay rank second and third, respectively, in amount of nutrient
discharge from urban land. Twenty five percent of the land use in the Narragansett Bay EDA is designated
as urban, and 53 percent of the Massachusetts Bay EDA is urban lands.
Other. Other lands include rangeland and brushland. Nutrient discharges come from natural sources and
from some fertilizer application. The discharge from this category is low and almost negligible in
comparison to the other nonpoint sources in the region. This is due to the limited area of this land use
type. Other lands make up approximately 1 percent of the total land area in the Northeast and nutrient
discharges account for 0.1 percent of nonpoint estimates.
Range and brushland are treated similarly to agriculture and forest lands using the SWRRB daily
simulation model to calculate nutrient discharge from runoff. Ground cover for other lands is basically
grasses and brush, and less amounts of fertilizers are applied.
Point Sources. Point sources are those WWTPs and industrial facilities that are land based and discharge
wastewater directly to surface water through a pipe or similar conveyance on a regular basis. The
discharge estimates in this category are marked by their low variability in both.flow and pollutant
concentration.
Point source discharge estimates for WWTPs and industrial facilities were based on measured or
estimated flow data times a measured or estimated nutrient concentration (NOAA, 1987b). Estimating
loads when monitored data were not available required development of: 1) a comprehensive list of point
source discharges in the region and their associated wastewater flow volumes; 2) characteristic
13
-------
information, such as level of treatment, industry operation levels, and seasonal discharges (where
available); and 3) typical nutrient concentrations based upon industry type.
Estimates of flow were obtained from the Discharge Monitoring Reports (DMR) or from regional and
Federal data bases listing NPDES permitted flow, design flow, or estimated average flow for a facility. The
Federal data base used for WWTPs was the 1982 EPA Construction Grants Needs Survey (U.S. EPA,
1985), and for industrial facilities, the EPA Permit Compliance System and the Industrial Facilities
Discharge file was used.
Pollutant concentrations for WWTPs were obtained from: 1) EPA's Forty-City Study that presents
data on the occurrence and fate of conventional and toxic pollutants collected from 1978 to 1980 for 50
WWTPs; 2) EPA's Four-City Study that presents pollutant concentrations from residential, commercial,
and industrial sources; and 3) information supplied by EPA's Municipal Environmental Research
Laboratory. Pollutant discharge concentrations for each industrial category were obtained from the EPA
industry status sheets of effluent characteristics for selected industrial point source categories. For
industries not covered in the status sheets, concentrations were derived from EPA Effluent Guideline
Development Documents (U.S. EPA, 1986), studies of specific industrial categories, and concentration
estimates developed by NOAA based on a survey of DMR data.
Wastewater Treatment Plants. WWTPs are facilities that receive and treat wastewater from residential,
commercial, and industrial sources. Over 200 WWTPs account for 90 percent of point source nutrient
discharges in coastal counties in Northeast estuaries. WWTPs can be either major or minor. Major plants
discharge over one million gallons per day of wastewater, and minor plants discharge less that one million
gallons per day. Long Island Sound, Massachusetts Bay, Narragansett Bay, and the Merrimack River
basins have the largest inputs of nutrients from WWTPS. Population densities are also the greatest for
these areas.
Sources of phosphorus in domestic wastewater are human excrement, synthetic laundry detergents,
and water treatment chemicals. Industrial wastes that are typically high in phosphorous and generally
discharged through WWTPs include fertilizer production plants, feedlots, meat processing and packing,
milk processing, commercial laundries, and some food processing wastes. Primary sources of nitrogen
are from urea, feces, and other organic matter. Industrial wastewater discharges that are high in nitrates
are feedlots, fertilizer production, meat processing, milk processing, petroleum refineries, coking facilities,
synthetic fiber plants, and industries that clean with ammonia containing compounds.
Industries. Industrial operations are defined by a series of four-digit Standard Industrial Classification (SIC)
codes that classify industrial facilities according to their types of products and activities. These codes
classify industrial facilities according to their types of products and activities. The four-digit SIC code is the
basic classification unit used in NOAA's NCPDI to define typical pollutant concentrations. The pollutants
are discharged directly to streams and rivers in the EDA and are separate from industrial pollutants
discharged to WWTPs. The discharges come from production processes, contact cooling water, non-
contact cooling water, or any combination of these. Industrial facilities are diverse and complex depending
on the type of industry and are the largest overall contributor of pollutant discharges other than nutrients,
such as petroleum hydrocarbons or metals. Nutrient discharges from industrial sources are small
compared to WWTPs and nonpoint urban runoff. Industrial discharges total about 5 percent of point
source discharges in coastal counties. The primary industrial contributions come from the Long Island
Sound, Narragansett Bay, and Casco Bay EDAs.
Upstream Sources. Estimates were made for upstream riverine sources with an annual average flow in
excess of 1,000 cubic feet per second. While all other sources of discharges in the NCPDI are located
within the coastal counties, upstream sources, when present, account for that portion of the total point,
nonpoint, and natural pollutant loads to the estuary that originates from outside the coastal counties.
Upstream sources also reflect concentrations after transport, chemical transformations, and settling
behind dams upstream of the coastal counties. For the Northeast, significant amounts of nitrogen are
from upstream sources. They contribute less total phosphorus, ranking second to WWTPs (Figure 5).
Five estuarine systems in the Northeast have significant nutrient discharges from upstream sources.
14
-------
Nutrient discharges from upstream riverine sources are computed as the product of the seasonal flow
and seasonal nutrient concentration (NOAA, 1987c). Stream discharge data were obtained from annual
USGS State Water Resources Data Reports (Smith and Alexander, 1983). Ambient water quality data
were obtained from the USGS National Stream Quality Accounting Network (NASQAN) and other USGS
and state water quality monitoring stations. Ideally, flow and concentration data would be available for each
stream at its point of entry to the coastal counties. In practice, gages were not always located at this point
nor were complete water quality data always available. In some cases, estimates were based on values
from nearby streams with similar flows and from land use characteristics, or were prorated using drainage
area information.
SIMPLE COMPARISONS BY ESTUARY
Comparisons of pollutant discharge data among the estuaries in the Northeast can be made from
several different perspectives to assess the extent of the nutrient problem. Figures 6 and 7 illustrate the
relative contribution of point, nonpoint, and upstream sources to the total discharge to each estuary.
Tables 6 and 7 emphasize the nitrogen and phosphorus discharge per unit of estuarine surface area
ranked in descending order by estuary. Also, the cumulative regional percentage by estuary of the total
nitrogen and total phosphorus discharge are presented along with the cumulative regional percentage of
total estuarine surface area and population. Organized in this way, the data provide information on how
much of the resource base and population in the study area is being affected by nutrient discharge.
Tables 8 and 9 rank order the estuaries by the amount of estuarine surface area to illustrate how much of
the estuarine resource base in the region is accounted for by discharges of nitrogen and phosphorus and
population.
In the Northeast, 58 percent of the estuarine resource base receives approximately 96 percent of
nitrogen loading and 93 percent of phosphorus loading from point, nonpoint, and upstream sources.
Approximately 94 percent of the population lives in these areas. The most densely populated areas, the
Massachusetts Bay, Narragansett Bay. and Long Island Sound EDAs, are included in the systems
receiving large nutrient discharges. The greatest source of nitrogen discharges in the Northeast is from
upstream sources, and for phosphorus, WWTPs (Figure 5). Urban runoff is the primary source of nitrogen
loading for those estuaries without an upstream source. Due to its relatively large discharge and small
surface area, the Merrimack River receives the largest annual load of nutrients per square mile. It
represents 0.2 percent of the estuarine resource base and 10 percent of total loading. Long Island
Sound, on the other hand, has the largest estuarine surface area and receives the largest nutrient
loading, but ranks fifth in surface area affected by nitrogen loading and seventh for phosphorus. Even
though this body of water is large with a large dilution, the loading is significant enough that eutrophication
problems have been documented in the western portion of the Sound. Massachusets Bay, with a
population density of 1,681 per square mile, ranks second in surface area affected by phosphorus
discharge and sixth in nitrogen discharge. The land area around Massachusetts Bay is highly urbanized,
and nutrient discharges come primarily from urban runoff and WWTPs. Urban runoff and WWTPs are also
primary sources of nutrients in Narragansett Bay. Some of the other estuarine systems, such as Saco Bay
and Great Bay, which fall in the top five for surface area affected by nutrient input, have relatively small
nutrient discharges, but also small surface areas. Upstream sources for nitrogen and phosphorus
discharges are important inputs to Penobscot and Sheepscot bays, the Merrimack River, and Long Island
Sound. The remainder of the 17 estuaries receive less than 10 tons per year per square mile of nitrogen
discharge and less than 2 tons per year per square mile of phosphorus discharge, which affects
approximately 3 percent or less of the estuarine resource base.
15
-------
Figure 6. Nitrogen discharges by source by estuary
Estuary
Tons/Year
Passamaquoddy Bay
Englishman Bay
Nairaguagus Bay
Blue Hill Bay
Penobscot Bay
Muscongus Bay
Sheepscot Bay
Casco Bay
Saco Bay
Great Bay
Memmack River
Massachusetts Bay
Cape Cod Bay
Buzzards Bay
Narragansett Bay
Gardiners Bay
Long Island Sound
0 200 400 600 800 1000 1200 1400 1600 1800 2000 2200 2400 2600
Figure 7. Phosphorus discharges by estuary
Estuary
Tons/Year
Passamaquoddy Bay
Englishman Bay
Narraguagus Bay
Blue Hill Bay
Penobscot Bay
Muscongus Bay
Sheepscot Bay
Casco Bay
Saco Bay
Great Bay
Menimack River
Massachusetts Bay
Cape Cod Bay
Buzzards Bay
Narragansen Bay
Gardiners Bay
Long Island Sound
Nonpobn
Point
Upstream
0 100 200 300 400 500 600 700 800 900 1000 1100 1200 1300
16
-------
Table 6. Nitrogen discharge by estuary ranked by discharge per square mile of esUianne surface water
M*rrlm*ck River
BnienirjBtBiy
Sago Bay
OreatBay
long Ktand Sound
Inoiiartirititt ft~f
Nanaganeetl Bay
,. n^
OordknenBey
BuzzordiBay
Engkinman Bay
Poawnaaada/Bay
MnaguagutBBf
Bue Nil Bay
MneanguoBey
Cap. Cod B%
RogtarMTeMa
Otterargo
(tons/year)
10.111
6.741
1.254
640
50.146
7.995
4.574
7.608
1.418
985
469
151
294
106
155
56
380
95.287
Quarters* Percent ol Cumuuov*
(lone/yr /tq ml ) Regional TaM Total
(ESA)
16852 106 106
64 9
73 6
42 7
39.1 S
22.0
27.7
21 6
a.*
S.O
2.1
2.0
1.5
i a
0.8
0.7
2 19 8
3 21 1
21 8
74 4
82 a
•76
958
67 3
88 3
96 6
99 0
tt 3
894
•• 5
•• 6
1000
24 100
Surface AIM
(eq ml)
6
103
17
15
1.261
364
165
361
164
197
226
76
157
70
115
72
646
3.939
Parcenef
Regional ToM
02
26
04
0 4
325
2
2
.2
2
0
a
•
0
a
19
1 8
139
100
OurnJatw
TOM
0 2
28
3 2
3 6
36 1
45 3
485
S6.7
626
679
736
75 6
796
61 3
643
66 1
100 0
Denetty
(tq rrt at EDA)
441
62
61
227
963
1.681
1.070
62
257
661
557
12
11
18
26
• 0
552
422
POBUll
ToM In EDA
(tnutandt)
9*1
362
105
200
5.485
2.021
1.232
171
216
138
107
10
IS
7
16
24
117
11.277
•ton
Percent of
Regional ToM
a 6
3 2
0 9
1 8
488
179
10 •
1.5
1 •
1 2
1 7
0 1
0 1
0 1
0 1
02
1 0
100
CunuMv*
ToM
• S
11 7
12 7
14 4
83 1
81 0
•1 9
93 4
95 4
966
98 3
•a 4
•a s
98 6
96 7
90 0
100 0
Abbrartaaont tq ml. equorn meio. EDA. MUrino arekiag* MM. ESA. Eaurin* urtaoe area.
Table 7. Nitrogen discharge by estuary ranked by percent of regional estuanne resource base
Eotuary
long Mend Sound
Capo Cod Be/
Haaituiairiifle)
PengbeeatBoy
Buzzard* Bay
OananonBey
NarregenHtl Bay
CoagoBay
PBBumaqjoddyBay
Blue Hill Bay
Cneeracarjey
Engrariflwi Boy
MncongueBey
Narraguegut Bay
SacoBay
(•eat Bay
Mmlmack River
ReoonelToM*
Emartne ntoource Bate
Surface ATM
(*q ml)
1.281
548
384
361
226
197
165
164
157
115
103
76
72
70
17
15
6
3.939
Percent of
Refer* ToM
325
9.2
• 2
sa
S.O
4.2
4.2
40
29
26
1 •
1.8
1.6
04
04
02
100
Cumulalv*
TOM
325
464
557
64 6
706
756
79 6
640
660
808
•35
•54
•73
•90
995
998
1000
DMfUTQS
(tera/yoor)
50.148
380
7.995
7.806
469
985
4.574
1.416
294
155
6.741
151
58
106
1.254
640
10.111
95.267
Nnrogm Otteharg* PapuMon
Ottenarat
39
1
22
22
2
5
28
g
2
1
• S
2
1
2
74
43
1.685
24
Percental
) Reajena) Teta)
526
04
64
82
OS
1 0
4 a
1 S
03
02
92
02
0 1
0 1
1 3
07
10 6
100
CunUatv*
TaM
626
530
61 4
696
701
71 1
759
774
777
779
67 1
872
873
874
667
at 4
100 0
Donnty
(eq rrt)
•63
552
1.661
62
SS7
681
1.070
257
11
28
62
12
60
18
61
227
441
422
Total In EDA
(tnouMndt)
5.485
117
2.021
171
117
138
1.232
216
16
16
362
10
24
7
105
200
• 61
11.277
Pereeraof
RegoMTeM
46 6
1 0
17 •
1 S
1 7
1.2
10 •
1 •
0 1
0 1
3 2
0 1
02
0 1
0 •
1 8
6 5
100
CunUalvt
ToM
466
49 7
• 7 6
69 1
70 B
72 1
•3 0
84 9
65 1
652
68 4
665
887
88 a
89 7
91 S
100 0
AetreiMon* aq ml., aquaro moot. EDA, Mtjorino drama* traa. ESA. Eeurlne tutors* oroa.
Table 8. Phosphorus discharge by estuary ranked by discharge per square mile of estuarlne surface water
Estuary
Phoapnorut Dnerarge
Obcnarga Dtarurg* Parcomar CunUaOv*
(loni/yoer) (tont/yr /tq ml ) Regional ToM TaM
Merrtmack River
Or*al Bey-
San Bay
Lang Mend Sound
Can Bey
deration Bey
PencbtcotBay
Buttardk Bar
Cape Cod Bay
MAConguoBe,
PaMTiaojDoayBa/
Narreguagui Bay
1.626
203
4.091
1.776
1(5
641
7.527
471
440
776
216
185
37
23
15
32
12
(ESA)
271.3
13.5
11.*
10.8
11 5
6.2
S.9
29
22
2.1
0.9
0.3
0.3
0.3
02
02
0.2
• •
1.1
22.4
• 7
1 1
35
41 2
26
24
42
1 2
1 0
02
0 1
0 1
02
0 1
• 9
100
324
42 1
43 2
48 7
879
•OS
•2 •
•72
•8 3
99 3
996
tt 7
888
999
1000
Ettuarino Rotaureo Bat*
Surface An*
(eq ml)
6
IS
364
165
17
103
1.261
164
197
361
228
546
115
76
72
157
70
Percent ol
Regan* ToM
02
04
9 2
4 2
04
26
32 5
4 2
50
92
SB
13.9
2 9
1 B
1 6
4 0
i a
CunuMv*
TOM
02
98
94
140
144
170
485
537
St 7
679
736
67 6
90 5
924
94 2
98 2
100 0
Oonttty
(tq rrt of EOA)
441
227
1.661
1.070
61
• 2
963
257
661
62
657
552
26
12
60
11
18
PapuMon
TOM m EOA
(tiouaandt)
961
200
2.021
1.232
105
362
6.465
216
136
171
197
117
16
10
24
IS
7
Percent ol
RogtarMToM
65
1 6
179
10 9
09
32
488
1 9
1 2
1 S
1 7
1 0
0 1
0 1
02
0 1
0 1
CumuMv*
TaM
a s
28 2
26.4
39 1
40 1
43 3
• 1 9
•3 a
•S 1
•a a
98 3
994
995
•9 6
99 a
99 9
1000
18.269
4 6
100
3.939
100
422
11.277
100
MbmUaam aq no. oauora man. EOA. oabarina draVtag* ana, ESA. EfMrino ourtoe* oroa.
17
-------
Table 9. Phosphorus discharge by estuary ranked by percent of regional estuanne resource base
Eatiury
RaMMi OHdurgt
ToM
(torn/few) (ton«/yr Itq ml)
Dmlty TOM to EDA Pranl tf
ton!) (thouurxfe) FtegMToM
TeM
Long Mmd Sow*
MuurtWMOiB*
Buzurdt Biy
QvdkMft Bar
NvngcnMBBqr
CBOiBqr
aw HHI BW
Sr~T^'T"^~^r
MjuenguiBiy
Nmpugw Bqr
OraMBqr
Mcntiiuck Rhnr
1.211
541
364
361
226
197
165
164
167
115
103
76
72
70
I 7
15
6
325
13 9
92
8.2
6.*
SO
4.2
42
4 0
1.9
2.6
1.9
1.6
04
04
02
325
46 4
557
64 6
706
75 6
79 6
64 0
88 0
909
93 5
954
97 3
99 0
99 5
99 8
100 0
7.527
115
4.091
775
216
440
1.776
471
12
37
641
23
15
12
196
203
1.626
59
03
11 2
21
09
22
106
29
02
0 3
6 2
0 3
02
02
11 5
13 6
271 3
41 2
1 0
22 4
4 2
1 2
2 4
9 7
26
02
02
3 5
0 1
0 1
0 1
1 1
1 1
8 9
41 i
42
64
66
70
72
12
14
14
IS
16
66
SO
86
90
91
100
963
552
1.661
62
657
661
1.070
2S7
11
26
62
12
60
18
61
227
441
5.485
117
2.021
171
197
138
1.232
211
15
16
112
10
24
7
105
200
961
41 1
1 0
179
1 1
1 7
1 2
109
1 9
0 1
0 1
1 2
0 1
9 2
0 1
0 9
1 I
1 5
416
49 7
871
•9 1
709
72 1
130
149
15 1
162
11 4
11 5
617
11 1
197
91 6
1000
3.939
100
11.219
4 1
100
422
11.277
100
nH. squv* mil... EDA. «tu-1» ••"•» -••. ESA. Earn* ~l»o. «u
CONCLUDING COMMENTS
This report illustrates that the "strategic level" information developed on the susceptibility of an
estuary to pollutant concentration, nutrient discharge, and nutrient concentration status are useful for
suggesting which of the 17 estuaries in the Northeast may be experiencing nutrient- related pollution
problems and the predominant source of the nutrient discharge. With this type of information developed
in a consistent and comprehensive manner across estuaries, it may now be possible to plan better which
estuaries or sources of pollutant inputs should receive priority attention or emphasis in Federal and state
programs designed to improve or maintain the quality of the Nation's estuarine waters.
However, this information is not designed to provide definitive answers on controls or management
practices It is important to emphasize that users review and understand the assumptions, methods, and
accuracy of the information in this report. Developing this information for use on national and regional
scales required the use of many simplifying assumptions to account for the behavior of estuanes and to
estimate the levels of nutrient discharges to them. This report is only the first step in addressing the
questions of how to improve or maintain water quality of the Nation's estuaries.
18
-------
Appendix A. Summaries of the Susceptibility and Concentration Status
of Northeast Estuaries to Nutrient Discharges
Strategic Assessment
of Near Coastal Waters
Northeast Case Study
NOAA/EPA Team
on Near Coastal Waters
19
-------
PHYSICAL CHARACTERISTICS
Dimensions
Volume (cu. ft.)
Surface Area (sq. mi.)
Average Daily Inflow (cfs)
Estuarine Drainage Area (sq. mi.)
EDA within coastal counties
EDA outside coastal counties
EDA Total
Ruvial Drainage Area (sq. mi.)
Total Drainage Area (sq. mi.)
Pollution Susceptibility
Dissolved Concentration Potential (mg/l)
Particle Retention Efficiency (C/l)
11
3.15x10
157
6,200
1,376
1,824
3,200
NA
3,200
Cone Class
0.27 (M)
1.61 (H)
NUTRIENT CHARACTERISTICS
Estimated Loadings
(tons/year)
Point
Nonpoint
Upstream
Total
Nitrogen
102
192
0
294
Phosphorus
13
19
0
32
Predicted Concentration Status
(load in tons/year)
To Change Cone. Class.
Concentration Increase by Decrease by
mg/l Class Load % Load %
Nitrogen
Phosphorus
0.008
0.001
(L)
(L)
3,471 1,181
344 1,077
NA
NA
NA
NA
Abbreviations: cfs, cubic feet per second; mg/l, milligrams per
liter; NA, not applicable; L, low; M, medium; H, high; C/l,
volume/inflow.
1.01 Passamaquoddy Bay
ME,NB
Land Use
1
Nitrogen
Phosphorus
m Agriculture
0 Forest
EU Urban
H Range & Other Nonurban
Point Sources1
I Wastewater Trt. Plants
@ Industrial Facilities
Nonpoint Sources1
H Agriculture
0 Forest
M Urban
H Other Nonurban
Upstream Sources
n
1 Data based on coastal county portion of EDA.
INTERPRETATION
Passamaquoddy Bay is estimated to have a medium
susceptibility for concentrating dissolved substances.
This concentration potential combined with a low
nitrogen loading should result in a low nitrogen
concentration within the estuary. Similarly, the
concentration potential combined with the low
phosphorus loading should result in a low phosphorus
concentration. Based upon its low nutrient loading,
Passamaquoddy Bay should retain its present
characteristics. The N/P molecular ratio of the loading
(20.3) suggests the importance of phosphorus as a
potential limiting nutrient in the system.
Strategic Assessment Branch
Ocean Assessments Division
Office of Oceanography and Marine Assessment
National Ocean Service
National Oceanic and Atmospheric Administration
Office of Marine and Estuarine Protection
Office of Water
U.S. Environmental Protection Agency
20
-------
1.02 Englishman Bay
ME
PHYSICAL CHARACTERISTICS
Land Use
1
Dimensions
Volume (cu. ft.)
Surface Area (sq. mi.)
Average Daily Inflow (cfs)
Estuarine Drainage Area (sq. mi.)
EDA within coastal counties
EDA outside coastal counties
EDA Total
Fluvial Drainage Area (sq. mi.)
Total Drainage Area (sq. mi.)
Pollution Susceptibility
Dissolved Concentration Potential (mg/l)
Particle Retention Efficiency (C/l)
7.97 x1010
76
1,600
883
0
883
NA
883
Cone Class
0.92 (M)
1.58 (H)
NUTRIENT CHARACTERISTICS
Estimated Loadings
(tons/year)
Point
Nonpoint
Upstream
Total
Nitrogen
27
124
0
151
Phosphorus
13
10
0
23
Predicted Concentration Status
(load in tons/yr)
To Change Cone. Class.
Concentration Increase by Decrease by
mg/l Class Load % Load %
Nitrogen 0.014 (L) 939 622 NA NA
Phosphorus 0.002 (L) 86 374 NA NA
Abbreviations: cfs, cubic feet per second; mg/l, milligrams per
liter; NA, not applicable; L, tow; M, medium; H, high; C/l,
volume/inflow.
Nitrogen
Phosphorus
M Agriculture
E3 Forest
EH Urban
H Range & Other Nonurban
Point Sources
• Wastewater Trt. Plants
@ Industrial Facilities
Nonpoint Sources1
H Agriculture
0 Forest
Durban
IS Other Nonurban
Upstream Sources
D
1 Data based on coastal county portion of EDA.
INTERPRETATION
Englishman Bay is estimated to have a medium
susceptibility for concentrating dissolved substances.
This concentration potential combined with a low
nitrogen loading should result in a low nitrogen
concentration within the estuary. Similarly, the
concentration potential combined with the low
phosphorus loading should result in a low phosphorus
concentration. Based upon its low nutrient loading,
Englishman Bay should retain its present characteristics
despite its medium to high susceptibility to concentrate
dissolved substances. For N/P molecular ratios of in the
range of 10-20, determination of the limiting nutrient is
particularly difficult. However, the N/P molecular ratio of
the loading (14.5) suggests the importance of nitrogen
as a potentially limiting nutrient in the system.
Strategic Assessment Branch
Ocean Assessments Division
Office of Oceanography and Marine Assessment
National Ocean Service
National Oceanic and Atmospheric Administration
Office of Marine and Estuarine Protection
Office of Water
U.S. Environmental Protection Agency
21
-------
PHYSICAL CHARACTERISTICS
Dimensions
Volume (cu. ft.) 6.33 x1010
Surface Area (sq. mi.) 70
Average Daily Inflow (cfs) 900
Estuarine Drainage Area (sq. mi.)
EDA within coastal counties 416
EDA outside coastal counties 0
ED A Total 416
Fluvial Drainage Area (sq. mi.) NA
Total Drainage Area (sq. mi.) 416
Pollution Susceptibility
Cone Class
Dissolved Concentration Potential (mg/l) 1.54 (H)
Particle Retention Efficiency (C/l) 2.23 (H)
NUTRIENT CHARACTERISTICS
Estimated Loadings
(tons/year)
Point
Nonpoint
Upstream
Total
Nitrogen
13
93
0
106
Phosphorus
6
6
0
12
Predicted Concentration Status
(load in tons/year)
To Change Cone. Class.
Concentration Increase by Decrease by
mg/l Class Load % Load %
Nitrogen 0.016 (L) 544 513 NA NA
Phosphorus 0.002 (L) 53 442 NA NA
Abbreviations: ds, cubic feet per second; mg/l, milligrams per
liter; NA, not applicable; L, low; M, medium; H, high; C/l,
volume/inflow.
1.03 Narraguagus Bay
ME
Land Use
Phosphorus
Agriculture
Forest
urban
Range & Other Nonurban
Nitrogen Point Sources1
• Wastewater Trt. Plants
£3 Industrial Facilities
Nonpoint Sources1
El Agriculture
E3 Forest
Durban
Q Other Nonurban
Upstream Sources
D
1 Data based on coastal county portion of EDA.
INTERPRETATION
Narraguagus Bay is estimated to have a high
susceptibility for concentrating dissolved substances.
This concentration potential combined with a low
nitrogen loading should result in a low nitrogen
concentration within the estuary. Similarly, the
concentration potential combined with the low
phosphorus loading should result in a low phosphorus
concentration. Based upon its low nutrient loading,
Narraguagus Bay should retain its present characteristics
despite its high susceptibilty to concentrate dissolved
substances. For N/P molecular ratios in the range of 10-
20, determination of the limiting nutrient is particularly
difficult. However, the N/P molecular ratioof the loading
(19.6) suggests the importance of phosphorus as a
potentially limiting nutrient in the system.
Strategic Assessment Branch
Ocean Assessments Division
Office of Oceanography and Marine Assessment
National Ocean Service
National Oceanic and Atmospheric Administration
Office of Marine and Estuarine Protection
Office of Water
U.S. Environmental Protection Agency
22
-------
1.04 Blue Hill Bay
ME
11
PHYSICAL CHARACTERISTICS
Dimensions
Volume (cu. ft.) 2.41x10
Surface Area (sq. mi.) 115
Average Daily Inflow (cfs) 1,300
Estuarine Drainage Area (sq. mi.)
EDA within coastal counties 800
EDA outside coastal counties 25
EDA Total 825
Fluvial Drainage Area (sq. mi.) NA
Total Drainage Area (sq. mi.) 825
Pollution Susceptibility
Cone Class
Dissolved Concentration Potential (mg/l) 1.03 (H)
Particle Retention Efficiency (C/l) 5.88 (H)
NUTRIENT CHARACTERISTICS
Land Use
1
Nitrogen
Phosphorus
m Agriculture
0 Forest
El Urban
ES Range & Other Nonurban
Point Sources1
• Wastewater Trt. Plants
ESI Industrial Facilities
Nonpoint Sources1
H Agriculture
E Forest
D Urban
H Other Nonurban
Upstream Sources
D
Estimated Loadings
(tons/year)
Point
Nonpoint
Upstream
Total
Nitrogen
48
107
0
155
Phosphorus
23
14
0
37
Predicted Concentration Status
(load in tons/year)
To Change Cone. Class.
Concentration Increase by Decrease by
mg/l Class Load % Load %
Nitrogen 0.016 (L) 815 526 NA NA
Phosphorus 0.004 (L) 60 162 NA NA
Abbreviations: cfs, cubic feet per second; mg/l, milligrams per
liter; NA. not applicable; L. low; M, medium; H, high; C/l,
volume/inflow.
1 Data based on coastal county portion of EDA.
INTERPRETATION
Blue Hill Bay is estimated to have a high susceptibility for
concentrating dissolved substances. This concentration
potential combined with a low nitrogen loading should
result in a low nitrogen concentration within the estuary.
Similarly, the concentration potential combined with the
low phosphorus loading should result in a low
phosphorus concentration. Based upon its low nutrient
loading, Blue Hill Bay should retain its present
characteristics despite its high susceptibility to
concentrate dissolved substances. The N/P molecular
ratio of the loading (9.3) suggests the importance of
nitrogen as a potentially limiting nutrient in the system.
Strategic Assessment Branch
Ocean Assessments Division
Office of Oceanography and Marine Assessment
National Ocean Service
National Oceanic and Atmospheric Administration
Office of Marine and Estuarine Protection
Office of Water
U.S. Environmental Protection Agency
23
-------
1.05 Penobscot Bay
ME
PHYSICAL CHARACTERISTICS
Dimensions
Volume (cu. ft.)
Surface Area (sq. mi.)
Average Daily Inflow (cfs)
Estuarine Drainage Area (sq. mi.)
EDA within coastal counties
EDA outside coastal counties
EDA Total
Fluvial Drainage Area (sq. mi.)
Total Drainage Area (sq. mi.)
Pollution Susceptibility
Dissolved Concentration Potential (mg/l)
Particle Retention Efficiency (C/l)
Land Use
1
7.25 x1011
361
16,100
1,106
2,054
3,160
6,250
9,410
Cone Class
0.13 (M)
1.43 (H)
NUTRIENT CHARACTERISTICS
Estimated Loadings
(tons/year)
Point
Nonpoint
Upstream
Total
Nitrogen
176
352
7,280
7,808
Phosphorus
61
28
686
775
Predicted Concentration Status (mg/l)
Concentration
mg/l Class
To Change Cone. Class.
Increase by Decrease by
Load % Load %
Nitrogen
Phosphorus
0.104
0.010
(M)
(M)
67
6,
.091
715
859
866
318
26
4
3
Abbreviations: cfs, cubic feet per second; mg/l, milligrams per
liter; NA, not applicable; L, tow; M, medium; H, high; C/l,
volume/inflow.
Nitrogen
Phosphorus
m Agriculture
EZ Forest
H Urban
Q Range & Other Nonurban
Point Sources1
• Wastewater Trt. Plants
E2 Industrial Facilities
Nonpoint Sources1
H Agriculture
E Forest
Durban
Q Other Nonurban
Upstream Sources
D
1 Data based on coastal county portion of EDA.
INTERPRETATION
Penobscot Bay is estimated to have a medium
susceptibility for concentrating dissolved substances.
This concentration potential combined with a medium
nitrogen loading should result in a medium nitrogen
concentration within the estuary. Similarly, the
concentration potential combined with the medium
phosphorus loading should result in a medium
phosphorus concentration. Based upon its present
nutrient loading and its susceptibility to concentrate
dissolved substances, Penobscot Bay should exhibit
those characteristics associated with both low and
medium nutrient concentration. The N/P molecular ratio
of the loading (22.3) suggests the importance of
phosphorus as a potentially limiting nutrient in the
system.
Strategic Assessment Branch
Ocean Assessments Division
Office of Oceanography and Marine Assessment
National Ocean Service
National Oceanic and Atmospheric Administration
Office of Marine and Estuarine Protection
Office of Water
U.S. Environmental Protection Agency
24
-------
PHYSICAL CHARACTERISTICS
Dimensions
Volume (cu. ft.)
Surface Area (sq. mi.)
Average Daily Inflow (cfs)
Estuarine Drainage Area (sq. mi.)
EDA within coastal counties
EDA outside coastal counties
EDA Total
Fluvial Drainage Area (sq. mi.)
Total Drainage Area (sq. mi.)
Pollution Susceptibility
Dissolved Concentration Potential (mg/l)
Particle Retention Efficiency (C/l)
8.55 x1010
72
600
346
0
346
NA
346
Cone Class
2.25 (H)
4.52 (H)
NUTRIENT CHARACTERISTICS
Estimated Loadings
(tons/year)
Point
Nonpoint
Upstream
Total
Nitrogen
14
44
0
58
Phosphorus
10
5
0
15
Predicted Concentration Status
(load in tons/year)
To Change Cone. Class.
Concentration Increase bv Decrease by
mg/l Class Load % Load %
Nitrogen 0.013 (L) 387 667 NA NA
Phosphorus 0.003 (L) 29 196 NA NA
Abbreviations: cfs, cubic feet per second; mg/l, milligrams per
liter; NA, not applicable; L, low; M, medium; H, high; C/l,
volume/inflow.
1.06MuscongusBay
ME
Land Use1
Nitrogen
Phosphorus
m Agriculture
0 Forest
El Urban
Q Range & Other Nonurban
Point Sources1
I Wastewater Trt. Plants
E3 Industrial Facilities
Nonpoint Sources1
H Agriculture
0 Forest
El Urban
H Other Nonurban
Upstream Sources
D
Data based upon coastal county portion of EDA.
INTERPRETATION
Muscongus Bay is estimated to have a high susceptibility
for concentrating dissolved substances. This
concentration potential combined with a low nitrogen
loading should result in a low nitrogen concentration
within the estuary. Similarly, the concentration potential
combined with the low phosphorus loading should result
in a low phosphorus concentration. Based upon its low
nutrient loading, Muscongus Bay should retain its
present characteristics despite 'its high susceptibility to
concentrate dissolved substances. The N/P molecular
ratio of the loading (8.6) suggests the importance of
nitrogen as a potentially limiting nutrient in the system.
Strategic Assessment Branch
Ocean Assessments Division
Office of Oceanography and Marine Assessment
National Ocean Service
National Oceanic and Atmospheric Administration
Office of Marine and Estuarine Protection
Office of Water
U.S. Environmental Protection Agency
25
-------
PHYSICAL CHARACTERISTICS
Dimensions
Volume (cu. ft.)
Surface Area (sq. mi.)
Average Daily Inflow (cfs)
Estuarine Drainage Area (sq. mi.)
EDA within coastal counties
EDA outside coastal counties
EDA Total
Fluvial Drainage Area (sq. mi.)
Total Drainage Area (sq. mi.)
Pollution Susceptibility
Dissolved Concentration Potential (mg/l)
Particle Retention Efficiency (C/l)
1.18 x1011
103
17,600
984
5,166
6,150
3,920
10,070
Cone Class
0.09 (L)
0.21 (M)
NUTRIENT CHARACTERISTICS
Estimated Loadings
(tons/year)
Point
Nonpoint
Upstream
Total
Nitrogen
77
474
8,190
8.741
Phosphorus
52
46
543
641
Predicted Concentration Status
(load in tons/year)
To Change Cone. Class.
Concentration Increase by Decrease by
mg/l Class Load % Load %
Nitrogen 0.077 (L) 2,607 30 NA NA
Phosphorus 0.006 (L) 494 77 NA NA
Abbreviations: cfs, cubic feet per second; mg/l, milligrams per
liter; NA, not applicable; L, low; M, medium; H, high; C/l,
volume/inflow.
Land Use
1
Nitrogen
Phosphorus
1.07 Sheepscot Bay
ME, NH
m Agriculture
E3 Forest
EH Urban
Q Range & Other Nonurban
Point Sources1
I Wastewater Trt. Plants
E3 Industrial Facilities
Nonpoint Sources1
M Agriculture
0 Forest
Durban
H Other Nonurban
Upstream Sources
D
1 Data based on coastal county portion of EDA.
INTERPRETATION
Sheepscot Bay is estimated to have a low susceptibility
for concentrating dissolved substances. This
concentration potential combined with a medium
nitrogen loading should result in a low nitrogen
concentration within the estuary. Similarly, the
concentration potential combined with the medium
phosphorus loading should result in a low phosphorus
concentration. Based upon its present nutrient loading
and its susceptibility to concentrate dissolved
substances, Sheepscot Bay should exhibit those
characteristics associated with both low and medium
nutrient concentration. The N/P molecular ratio of the
loading (30.2) suggests the importance of phosphorus
as a potentially limiting nutrient in the system.
Strategic Assessment Branch
Ocean Assessments Division
Office of Oceanography and Marine Assessment
National Ocean Service
National Oceanic and Atmospheric Administration
Office of Marine and Estuarine Protection
Office of Water
U.S. Environmental Protection Agency
26
-------
PHYSICAL CHARACTERISTICS
Dimensions
Volume (cu. ft.)
Surface Area (sq. mi.)
Average Daily Inflow (cfs)
Estuarine Drainage Area (sq. mi.)
EDA within coastal counties
EDA outside coastal counties
EDA Total
Fluvial Drainage Area (sq. mi.)
Total Drainage Area (sq. mi.)
Pollution Susceptibility
Dissolved Concentration Potential (mg/l)
Particle Retention Efficiency (C/l)
1.91
11
x10
164
2,100
974
185
1,159
NA
1,159
Cone Class
0.61 (M)
2.89 (H)
NUTRIENT CHARACTERISTICS
Loadings
(tons/year)
Point
Nonpoint
Upstream
Total
Nitrogen
751
667
0
1,418
Phosphorus
413
58
0
471
Predicted Concentration Status
(load in tons/year)
To Change Cone. Class.
Concentration Increase by Decrease bv
mg/l Class Load % Load %
Nitrogen 0.087 (L) 213 15 NA NA
Phosphorus 0.029 (M) 1,160 246 308 65
Abbreviations: cfs, cubic feat per second; mg/l, milligrams per
liter; NA, not applicable; L, low; M, medium; H, high; C/l,
volume/inflow.
1.08 Casco Bay
ME
Land Use1
Nitrogen
Phosphorus
m Agriculture
0 Forest
Durban
C9 Range & Other Nonurban
Point Sources1
• Wastewater Trt. Plants
E3 Industrial Facilities
Nonpoint Sources1
Hi Agriculture
E3 Forest
Durban
H Other Nonurban
Upstream Sources
D
1 Data based on coastal county portion of EDA.
INTERPRETATION
Casco Bay is estimated to have a medium susceptibility
for concentrating dissolved substances. This
concentration potential combined with a low nitrogen
loading should result in a low nitrogen concentration
within the estuary. Similarly, the concentration potential
combined with the medium phosphorus loading should
result in a medium phosphorus concentration. Based
upon its present nutrient loading and its medium
susceptibility to concentrate dissolved substances,
Casco Bay should exhibit those characteristics
associated with both low and medium nutrient
concentration and may be most sensitive to increased
nitrogen loading. The N/P molecular ratio of the loading
(6.7) suggests the importance of nitrogen as a potentially
limiting nutrient in the system.
Strategic Assessment Branch
Ocean Assessments Division
Office of Oceanography and Marine Assessment
National Ocean Service
National Oceanic and Atmospheric Administration
Office of Marine and Estuarine Protection
Office of Water
U.S. Environmental Protection Agency
27
-------
PHYSICAL CHARACTERISTICS
Dimensions
Volume (cu. ft.)
Surface Area (sq. mi.)
Average Daily Inflow (cfs)
Estuarine Drainage Area (sq. mi.)
EDA within coastal counties
EDA outside coastal counties
EDA Total
Fluvial Drainage Area (sq. mi.)
Total Drainage Area (sq. mi.)
Pollution Susceptibility
Dissolved Concentration Potential (mg/l)
Particle Retention Efficiency (C/l)
10
1.53 x10
17
3,600
549
1,221
1,771
NA
1,771
Cone Class
0.45 (M)
0.13 (M)
NUTRIENT CHARACTERISTICS
Estimated Loadings
(tons/year)
Point
Nonpoint
Upstream
Total
Nitrogen
186
193
875
1,254
Phosphorus
116
24
55
195
Predicted Concentration Status
(load in tons/year)
To Change Cone. Class.
Concentration Increase by Decrease by
mg/l Class Load % Load %
Nitrogen 0.057 (L) 949 76 NA NA
Phosphorus 0.009 (L) 25 13 NA NA
Abbreviations: cfs, cubic feet per second; mg/l, milligrams per
liter; NA, not applicable; L, low; M, medium; H, high; C/l,
volume/inflow.
1.09 Saco Bay
ME, NH
Land Use
1
Nitrogen
123 Forest
Durban
E3 Range & Other Nonurban
Point Sources1
I Wastewater Trt. Plants
@ Industrial Facilities
Nonpoint Sources1
Phosphorus
1
Forest
urban
Other Nonurban
Upstream Sources
Data based on coastal county portion of EDA.
INTERPRETATION
Saco Bay is estimated to have a medium susceptibility for
concentrating dissolved substances. This concentration
potential combined with a low nitrogen loading should
result in a low nitrogen concentration within the estuary.
Similarly, the concentration potential combined with the
tow phosphorus loading should result in a low phoshorus
concentration. Based upon its susceptibility to
concentrate dissolved substances and its present
nutrient loading, Saco Bay should exhibit those
characteristics associated with both low and medium
nutrient concentration and be moderately sensitive to
changes in nutrient concentration. For N/P molecular
ratios in the range of 10-20, determination of the limiting
nutrient is particularly difficult. However, the N/P
molecular ratio of the loading (14.2) suggests the
importance of nitrogen as a potential limiting nutrient in
the system.
Strategic Assessment Branch
Ocean Assessments Division
Office of Oceanography and Marine Assessment
National Ocean Service
National Oceanic and Atmospheric Administration
Office of Marine and Estuarine Protection
Office of Water
U.S. Environmental Protection Agency
28
-------
PHYSICAL CHARACTERISTICS
Dimensions
Volume (cu. ft.)
Surface Area (sq. mi.)
Average Daily Inflow (cfs)
Estuarine Drainage Area (sq. mi.)
EDA within coastal counties
EDA outside coastal counties
EDA Total
Fluvial Drainage Area (sq. mi.)
Total Drainage Area (sq. mi.)
Pollution Susceptibility
Dissolved Concentration Potential (mg/l)
Particle Retention Efficiency (C/l)
4.75 x109
15
2,000
903
47
950
NA
950
Cone Class
1.54 (H)
0.08 (L)
NUTRIENT CHARACTERISTICS
Estimated Loadings
(tons/year)
Point
Nonpoint
Upstream
Total
Nitrogen
243
397
0
640
Phosphorus
160
43
0
203
Predicted Concentration Status
(load in tons/year)
To Change Cone. Class.
Concentration Increase by Decrease by
mg/l Class Load % Load %
Nitrogen
Phosphorus
0.098
0.031
(L)
(M)
11
448
2
221
NA
138
NA
68
Abbreviations: cfs, cubic feet per second; mg/l, milligrams per
liter; NA, not applicable; L, low; M. medium; H, high; C/l,
volume/inflow.
Land Use
1
Nitrogen
Phosphorus
1.10 Great Bay
ME, NH
m Agriculture
^ Forest
0 Urban
Q Range & Other Nonurban
Point Sources1
• Wastewater Trt. Plants
@ Industrial Facilities
Nonpoint Sources1
HI Agriculture
^ Forest
Durban
H Other Nonurban
Upstream Sources
D
Data for coastal county portion of EDA.
INTERPRETATION
Great Bay is estimated to have a high susceptibility for
concentrating dissolved substances. This concentration
potential combined with a low nitrogen loading should
result in a low nitrogen concentration within the estuary.
Similarly, the concentration potential combined with the
medium phosphorus loading should result in a medium
phosphorus concentration. Based upon its present
nutrient loading and its high susceptibility to
concentratedissolved substances, Great Bay should
exhibit those characteristics associated with both low and
medium nutrient concentration and should be sensitive
to changes in that concentration. The N/P molecular
ratio of the loading (7.0) suggests the importance of
nitrogen as a potentially limiting nutrient in the system.
Strategic Assessment Branch
Ocean Assessments Division
Office of Oceanography and Marine Assessment
National Ocean Service
National Oceanic and Atmospheric Administration
Office of Marine and Estuarine Protection
Office of Water
U.S. Environmental Protection Agency
29
-------
1.11 Merrimack River
NH,MA
PHYSICAL CHARACTERISTICS
Land Use
1
Dimensions
Volume (cu. ft.)
Surface Area (sq. mi.)
Average Daily Inflow (cfs)
Estuarine Drainage Area (sq. mi.)
EDA within coastal counties
EDA outside coastal counties
EDA Total
Fluvial Drainage Area (sq. mi.)
Total Drainage Area (sq. mi.)
Pollution Susceptibility
Dissolved Concentration Potential (mg/l)
Particle Retention Efficiency (C/l)
2.08 x 109
6
8,400
690
1,610
2,300
2,680
4,980
Cone Class
1.01 (H)
0.01 (L)
NUTRIENT CHARACTERISTICS
Estimated Loadings
(tons/year)
Point
Nonpoint
Upstream
Total
Nitrogen
1,347
614
8,150
10,111
Phosphorus
816
90
722
1,628
Predicted Concentration Status
(load in tons/year)
To Change Cone. Class.
Concentration Increase by Decrease by
mg/l Class Load % Load %
Nitrogen 1.022 (H) NA NA 222 2
Phosphorus 0.165 (H) NA NA 639 39
Abbreviations: cfs, cubic feet per second; mg/l, milligrams per
liter; NA, not applicable; L, low; M. medium; H, high; C/l,
volume/inflow.
Nitrogen
Phosphorus
m Agriculture
£2 Forest
LI Urban
B Range & Other Nonurban
Point Sources1
• Wastewater Trt. Plants
0 Industrial Facilities
Nonpoint Sources1
HI Agriculture
E2 Forest
El Urban
0 Other Nonurban
Upstream Sources
Data based on coastal county portion of EDA.
INTERPRETATION
Merrimack River has high susceptibility for concentrating
dissolved substances. This concentration potential
combined with a high nitrogen loading should result in a
high nitrogen concentration within the estuary. Similarly,
the concentration potential combined with the high
phosphorus loading should result in a high phosphorus
concentration. Based upon its high nutrient loading.
Merrimack River should exhibit those characteristics
associated with both high and medium nutrient
concentration. However, due to its high concentration
potential, the estuary should be sensitive to changes in
nutrient concentrations. For N/P molecular ratios in the
range of 10-20, determination of the limiting nutrient is
particularly difficult. However, the N/P molecular ratio of
the loading (13.8) suggests the importance of nitrogen
as a potentially limiting nutrient in the system.
Strategic Assessment Branch
Ocean Assessments Division
Office of Oceanography and Marine Assessment
National Ocean Service
National Oceanic and Atmospheric Administration
Office of Marine and Estuarine Protection
Office of Water
U.S. Environmental Protection Agency
30
-------
1.12 Massachusetts Bay
MA
PHYSICAL CHARACTERISTICS
Land Use1'2
Dimensions
Volume (cu. ft.)
Surface Area (sq. mi.)
Average Daily Inflow (cfs)
Estuarine Drainage Area (sq. mi.)
EDA within coastal counties
EDA outside coastal counties
EDA Total
Fluvial Drainage Area (sq. mi.)
Total Drainage Area (sq. mi.)
Pollution Susceptibility
Dissolved Concentration Potential (mg/l)
Particle Retention Efficiency (C/l)
7.85 x1011
364
2,900
1,178
24
1,202
NA
1,202
Cone Class
0.27 (M)
8.58 (H)
NUTRIENT CHARACTERISTICS
Estimated Loadings
(tons/year)
Point
Nonpoint
Upstream
Total
Nitrogen
6,181
1,813
0
7,994
Phosphorus
3,846
245
0
4,091
Predicted Concentration Status
(load in tons/year)
To Change Cone. Class.
Concentration Increase by Decrease bv
mg/l Class Load % Load %
Nitrogen 0.215 (M)
Phosphorus 0.110 (H)
28,636 358 4,331 54
NA NA 428 10
Abbreviations: cfs, cubic feet per second; mg/l, milligrams per
liter; NA, not applicable; L, low; M, medium; H, high; C/l,
volume/inflow.
Nitrogen
Phosphorus
m Agriculture
E3 Forest
Durban
Q Range & Other Nonurban
Point Sources1
I Wastewater Trt. Plants
H Industrial Facilities
Nonpoint Sources1'2
M Agriculture
E2 Forest
Durban
H Other Nonurban
Upstream Sources
D
1 Data based on coastal county portion of EDA.
2 Data based on Boston Bay land use from National Estuarine
Inventory, Volume 2.
INTERPRETATION
Massachusetts Bay is estimated to have a medium
susceptibility for concentrating dissolved substances.
This concentration potential combined with a medium
nitrogen loading should result in a medium nitrogen
concentration within the estuary. Similarly, the
concentration potential combined with the high
phosphorus loading should result in a high phosphorus
concentration. Based upon its present nutrient loading,
Massachusetts Bay should exhibit those characteristics
associated with both medium and high nutrient
concentration and may be somewhat less responsive to
nutrient reduction due to its concentration potential. The
N/P molecular ratio of the loading (5.3) suggests the
importance of nitrogen as a potential limiting nutrient in
the system.
Strategic Assessment Branch
Ocean Assessments Division
Office of Oceanography and Marine Assessment
National Ocean Service
National Oceanic and Atmospheric Administration
Office of Marine and Estuarine Protection
Office of Water
U.S. Environmental Protection Agency
31
-------
PHYSICAL CHARACTERISTICS
Dimensions
Volume (cu. ft.) 1.18 x1012
Surface Area (sq. mi.) 548
Average Daily Inflow (cfs) 1,800
Estuarine Drainage Area (sq. mi.)
EDA within coastal counties 771
EDA outside coastal counties 0
EDA Total 771
Fluvial Drainage Area (sq. mi.) NA
Total Drainage Area (sq. mi.) 771
Pollution Susceptibility
Cone Class
Dissolved Concentration Potential (mg/l) 0.69 (M)
Particle Retention Efficiency (C/l) 20.75 (H)
NUTRIENT CHARACTERISTICS
Estimated Loadings
(tons/year)
Point
Nonpoint
Upstream
Total
Nitrogen
267
113
0
380
Phosphorus
168
17
0
185
Predicted Concentration Status
(load in tons/year)
To Change Cone. Class.
Concentration Increase bv Decrease by
mg/l Class Load % Load %
Nitrogen
Phosphorus
0.026
0.013
(L)
(M)
1
1
,074
,269
283
686
NA
40
NA
21
Abbreviations: cfs, cubic feet per second; mg/l, milligrams per
liter; NA, not applicable; L, low; M, medium; H, high; C/l,
volume/inflow.
1.13 Cape Cod Bay
MA
Land Use
1
Nitrogen
Phosphorus
H Agriculture
0 Forest
Durban
S3 Range & Other Nonurban
Point Sources1
• Wastewater Trt. Plants
B9 Industrial Facilities
Nonpoint Sources1
M Agriculture
EJ Forest
D Urban
H Other Nonurban
Upstream Sources
D
1 Data based on coastal county portion of EDA.
INTERPRETATION
Cape Cod Bay is estimated to have a medium
susceptibility for concentrating dissolved substances.
This concentration potential combined with a low
nitrogen loading should result in a low nitrogen
concentration within the estuary. Similarly, the
concentration potential combined with the medium
phosphorus loading should result in a medium
phosphorus concentration. Based upon its ability to
concentrate dissolved substances, Cape Cod Bay
should retain those characteristics associated with
medium and low concentration but should be sensitive
to changes in concentration resulting from changes in
nutrient loads. The N/P molecular ratio of the loading
(4.6) suggests the importance of nitrogen as a potentially
limiting nutrient in the system.
Strategic Assessment Branch
Ocean Assessments Division
Office of Oceanography and Marine Assessment
National Ocean Service
National Oceanic and Atmospheric Administration
Office of Marine and Estuarine Protection
Office of Water
U.S. Environmental Protection Agency
32
-------
PHYSICAL CHARACTERISTICS
Dimensions
Volume (cu. ft.)
Surface Area (sq. mi.)
Average Daily Inflow (cfs)
Estuarine Drainage Area (sq. mi.)
EDA within coastal counties
EDA outside coastal counties
EDA Total
Fluvial Drainage Area (sq. mi.)
Total Drainage Area (sq. mi.)
Pollution Susceptibility
Dissolved Concentration Potential (mg/l)
Particle Retention Efficiency (C/l)
2.15 x1011
228
1,200
576
0
576
NA
576
Cone Class
1.04 (H)
5.68 (H)
NUTRIENT CHARACTERISTICS
Estimated Loadings
(tons/year)
Point
Nonpoint
Upstream
Total
Nitrogen
306
163
0
469
Phosphorus
193
23
0
216
Predicted Concentration Status
(load in tons/year) „
To Change Cone. Class.
Concentration Increase bv Decrease bv
mg/l Class Load % Load %
Nitrogen 0.049 (L) 491 105 NA NA
Phosphorus 0.023 (M) 744 344 120 56
Abbreviations: cfs, cubic feet per second; mg/l, milligrams per
liter; NA, not applicable; L, low; M, medium; H, high; C/l,
volume/inflow.
1.14 Buzzards Bay
MA
Land Use
1
Nitrogen
Phosphorus
m Agriculture
EZ Forest
Durban
H Range & Other Nonurban
Point Sources1
• Wastewater Trt. Plants
E9 Industrial Facilities
Nonpoint Sources1
EH Agriculture
0 Forest
D Urban
Q Other Nonurban
Upstream Sources
D
1 Data based on coastal county portion of EDA.
INTERPRETATION
Buzzards Bay is estimated to have a high susceptibility
for concentrating dissolved substances. This
concentration potential combined with a low nitrogen
loading should result in a low nitrogen concentration
within the estuary. Similarly, the concentration potential
combined with the medium phosphorus loading should
result in a medium phosphorus concentration. Based
upon its present nutrient loading and its high
susceptibility to concentrate dissolved substances,
Buzzards Bay should exhibit those characteristics
associated with both low and medium nutrient
concentration and should be sensitive to changes in that
concentration. The N/P molecular ratio of the loading
(4.8) suggests the importance of nitrogen as a potentially
limiting nutrient in the system.
Strategic Assessment Branch
Ocean Assessments Division
Office of Oceanography and Marine Assessment
National Ocean Service
National Oceanic and Atmospheric Administration
Office of Marine and Estuarine Protection
Office of Water
U.S. Environmental Protection Agency
33
-------
1.15 Narragansett Bay
MA, Rl
PHYSICAL CHARACTERISTICS
Land Use
1
Dimensions
Volume (cu. ft.)
Surface Area (sq. mi.)
Average Daily Inflow (cfs)
Estuarine Drainage Area (sq. mi.)
EDA within coastal counties
EDA outside coastal counties
EDA Total
Fluvial Drainage Area (sq. mi.)
Total Drainage Area (sq. mi.)
Pollution Susceptibility
Dissolved Concentration Potential (mg/l)
Particle Retention Efficiency (C/l)
1.39x1011
165
3,200
1,330
0
1,330
451
1,781
mg/l Class
0.52 (M)
1.38 (H)
NUTRIENT CHARACTERISTICS
Nitrogen
Phosphorus
m Agriculture
^ Forest
Durban
Q Range & Other Nonurban
Point Sources1
I Wastewater Trt. Plants
@ Industrial Facilities
Nonpoint Sources1
H Agriculture
£] Forest
D Urban
H Other Nonurban
Upstream Sources
Estimated Loadings
(tons/year)
Point
Nonpoint
Upstream
Total
Nitrogen
2,861
1,713
0
4.574
Phosphorus
1,544
234
0
1,778
Predicted Concentration Status
(load in tons/year)
To Change Cone. Class.
Concentration Increase by Decrease by
mg/l Class Load % Load %
Nitrogen 0.239 (M)
Phosphorus 0.093 (M)
14,563 318 2,660 58
136 8 1,587 89
Abbreviations: cfs, cubic feet per second; mg/l, milligrams per
liter; NA, not applicable; L, low; M, medium; H, high; C/l,
volume/inflow.
Data based on coastal county portion of EDA.
INTERPRETATION
Narragansett Bay is estimated to have a medium
susceptibility for concentrating dissolved substances.
This concentration potential combined with a medium
nitrogen loading should result in a medium nitrogen
concentration within the estuary. Similarly, the
concentration potential combined with the medium
phosphorus loading should result in a medium
phosphorus concentration. Based upon its present
nutrient loading, Narragansett Bay should retain those
characteristics associated with medium concentration
despite its susceptibility to concentrate dissolved
substances. The N/P molecular ratio of the loading (5.7)
suggests the importance of nitrogen as a potentially
limiting nutrient in the system.
Strategic Assessment Branch
Ocean Assessments Division
Office of Oceanography and Marine Assessment
Nationai Ocean Service
National Oceanic and Atmospheric Administration
Office of Marine and Estuarine Protection
Office of Water
U.S. Environmental Protection Agency
34
-------
PHYSICAL CHARACTERISTICS
Dimensions
Volume (cu. ft.) 1.11x1011
Surface Area (sq. mi.) 197
Average Daily Inflow (cfs) 700
Estuarine Drainage Area (sq. mi.)
EDA within coastal counties 400
EDA outside coastal counties 0
EDA Total 400
Fluvial Drainage Area (sq. mi.) NA
Total Drainage Area (sq. mi.) 400
Pollution Susceptibility
Cone Class
Dissolved Concentration Potential (mg/l) 1.77 (H)
Particle Retention Efficiency (C/l) 5.03 (H)
NUTRIENT CHARACTERISTICS
Estimated Loadings
(tons/year)
Point
Nonpoint
Upstream
Total
Nitrogen
644
341
0
985
Phosphorus
407
33
0
440
Predicted Concentration Status
(load in tons/year)
To Change Cone. Class.
Concentration Increase by Decrease by
mg/l Class Load % Load %
Nitrogen 0.175 (M)
Phosphorus 0.078 (M)
4,652 472
124 28
421
384
43
87
Abbreviations: cfs, cubic feet per second; mg/l, milligrams per
liter; NA, not applicable; L, low; M, medium; H, high; C/l.
volume/inflow.
1.16 Gardners Bay
NY
Land Use
1
Nitrogen
Phosphorus
M Agriculture
E2 Forest
Durban
Q Range & Other Nonurban
Point Sources1
• Wastewater Trt. Plants
0 Industrial Facilities
Nonpoint Sources1
H Agriculture
0 Forest
D Urban
H Other Nonurban
Upstream Sources
1 Data based on coastal county portion of EDA.
INTERPRETATION
Gardners Bay is estimated to have a high susceptibility
for concentrating dissolved substances. This
concentration potential combined with a medium
nitrogen loading should result in a medium nitrogen
concentration within the estuary. Similarly, the
concentration potential combined with the medium
phosphorus loading should result in a medium
phosphorus concentration. Based upon its present
nutrient loading, Gardiners Bay should retain its medium
concentration status. However this status should be
sensive to changes in nutrient loadings because of its
high concentration potential. The N7P molecular ratio of
the loading (5.3) suggests the importance of nitrogen as
a potentially limiting nutrient in the system.
Strategic Assessment Branch
Ocean Assessments Division
Office of Oceanography and Marine Assessment
Nationai Ocean Service
National Oceanic and Atmospheric Administration
Office of Marine and Estuarine Protection
Office of Water
U.S. Environmental Protection Agency
35
-------
1.17 Long Island Sound
NY, CT, MA
PHYSICAL CHARACTERISTICS
Land Use
Dimensions
Volume (cu. ft.)
Surface Area (sq. mi.)
Average Daily Inflow (cfs)
Estuarine Drainage Area (sq. mi.)
EDA within coastal counties
EDA outside coastal counties
EDA Total
Fluvial Drainage Area (sq. mi.)
Total Drainage Area (sq. mi.)
Pollution Susceptibility
Dissolved Concentration Potential (mg/l)
Particle Retention Efficiency (C/l)
2.14 x1012
1,281
30,000
3,543
3,687
7,230
10,010
17,240
Cone Class
0.05 (L)
2.32 (H)
NUTRIENT CHARACTERISTICS
Estimated Loadings
(tons/year)
Point
Nonpoint
Upstream
Total
Nitrogen
19,993
5,528
24,627
50.148
Phosphorus
5,000
628
1,899
7,527
Predicted Concentration Status
(load in tons/year)
To Change Cone. Class.
Concentration Increase by Decrease by
mg/l Class Load % Load %
Nitrogen 0.273 (M) 133,72826731,760 63
Phosphorus 0.041 (M) 10,861 144 5,688 76
Abbreviations: cfs, cubic feet per second; mg/l, milligrams per
liter; NA, not applicable; L, low; M, medium; H, high; C/l,
volume/inflow.
Nitrogen
Phosphorus
IH Agriculture
0 Forest
H Urban
Q Range & Other Nonurban
Point Sources1
I Wastewater Trt. Plants
E9 Industrial Facilities
Nonpoint Sources1
M Agriculture
E3 Forest
Q Urban
H Other Nonurban
Upstream Sources
Data based on coastal county portion of EDA.
INTERPRETATION
Long Island Sound has low susceptibility for
concentrating dissolved substances. This concentration
potential combined with a high nitrogen loading should
result in a medium nitrogen concentration within the
estuary. Similarly, the concentration potential combined
with the high phosphorus loading should result in a
medium phosphorus concentration. Based upon its low
susceptibility to concentrate dissolved substances,
Long Island Sound should exhibit those characteristics
associated with medium nutrient concentration despite
significant changes in nutrient loadings. For N/P
molecular ratios in the range of 10-20, determination of
the limiting nutrient is particularly difficult. However, the
N/P molecular ratio of the loading (14.8) suggests the
importance of nitrogen as a potentially limiting nutrient in
the system.
Strategic Assessment Branch
National Ocean Service
National Oceanic and Atmospheric Administration
Office of Marine and Estuarine Protection
Office of Water
U.S. Environmental Protection Agency
36
-------
Appendices B through E
Strategic Assessment
of Near Coastal Waters
Northeast Case Study
NOAA/EPA Team f
on Near Coastal Waters
37
-------
Appendix B. Nutrient Discharges by Season by Estuary (tons per year) - circa 1982
Estuary
Source
Nitrogen
Winter Spring Summer Fall
Total
Phosphorus
Winter Spring Summer
Fall
Total
Passamaquoddy Bay
Englishman Bay
Nanaguagus Bay
Blue Hill Bay
PenobseotBay
MuscongusBay
Agriculture
CMVAB*.
rorvBi
Urban
Other
WWTPs
Industry
Uostream
Total
Agriculture
Forest
Urban
Other
WWTPs
Industry
Upstream
Total
»
Agriculture
Forest
Urban
Other
WWTPs
Industry
Upstream
Total
Agriculture
Forest
Urban
Other
WWTPs
Industry
Upstream
Total
Agriculture
g_..— — »
rOrBoI
Urban
Other
WWTPs
Industry
Upstream
Total
Agriculture
Forest
Urban
Other
WWTPs
Industry
Total
31.6
13.7
22.1
0.3
4.8
19 4
0 0
91.8
24.B
11.5
12.5
1.0
4.4
1.1
0 0
55.3
23.3
8.2
8.0
1.4
2.1
O.S
0 0
39.5
8.2
7.7
22.7
2.0
7.9
1.9
0.0
48.4
18.8
82.0
40.5
1.8
80.4
18.3
1 310 0
1.491.5
7.8
0.1
5.0
0.1
3.5
0.0
0 0
16.5
40.1
4.8
24.8
0.2
4.8
22.3
0 0
96.9
30.8
3.0
11.7
0.8
4.4
3.3
0.0
63.8
29.0
1.8
20.2
0.8
3.0
1 3
0 0
55 9
7.7
2 0
21.2
1.1
7.9
e.o
0 0
48.0
31.1
58.8
39.9
1.0
20.4
29.2
3 550 0
3.730.5
13.7
0.0
5.0
0.1
3.5
0.1
0.0
22.4
12.6
0.1
24.4
0.1
4.7
21.3
0.0
63.2
8.9
0.3
10.9
0.3
4.3
3.1
0 0
27.6
8.4
0.1
17.8
0.4
2.8
1.1
0 0
30.6
2.2
0.2
19.7
0.6
7.7
5.6
0.0
36.0
7.7
5.2
38.4
0.6
20.1
27.4
90S 0
1.002.2
4.9
0.0
2.4
0.0
3.4
0.1
0 0
10.6
0.6
0.0
15.0
0.0
4.6
20.8
0.0
40.8
0.6
0.0
7.3
0.1
3.7
1.9
0.0
13.5
0.4
0.0
2.1
0.2
1.8
0.1
0.0
4.5
0.1
0.0
13.3
0.3
6.6
3.4
0.0
23.8
0.4
0.0
25.S
0.3
16 3
22.8
1 .520 0
1.565.2
0.2
0.0
16.9
0.0
2.9
0.0
0.0
20.1
84.8
18.6
86.3
0.6
18.8
83.8
0.0
292.8
65.0
14.8
42.4
2.0
16.7
9.3
0.0
150.1
61.2
7.9
46.1
2.7
9.6
3.0
0 0
130.6
16.2
9.8
76.9
4.0
30.2
16.9
0.0
154.2
57.7
148.0
142.3
3.6
77.2
97.7
7.285 0
7.809.4
26.6
0.1
29.4
0.1
13.3
0.3
0 0
69.8
0.3
0.0
3.6
0.0
3.3
0.1
0.0
7.4
0.2
0.0
2.0
0.0
3.1
0.1
5.4
0.2
0.0
4.0
0.0
3.6
0.1
0 0
7.9
0.1
0.0
3.6
0.0
5.6
0.2
0 0
9.5
0.2
1.0
3.0
0.0
9.8
0.2
36 0
49.9
0.0
0.0
0.7
0.0
2.7
0.0
0.0
3.4
4.0
0.0
3.7
0.0
3.2
0.1
0 0
1 1.0
2.8
0.0
1.9
0.0
3.1
0.2
6.0
2.6
0.0
1.0
0.0
0.5
0.0
0 0
4.2
0.7
0.0
3.4
0.0
5.6
0.4
0.0
10.1
4.1
1.0
3.8
0.0
10.6
0.4
243 0
262.8
2.0
0.0
0.8
0.0
2.7
0.0
0.0
5.4
0.3
0.0
2.6
0.0
3.1
0.0
0 0
5.8
0.2
0.0
1.8
0.0
3.0
0.2
5.2
0.2
0.0
3.0
0.0
0.7
0.0
0 0
4.0
0.1
0.0
3.2
0.0
S.4
0.4
0 0
9.1
0.2
0.0
2.6
0.0
0.4
0.4
79 0
91.5
0.2
0.0
0.8
0.0
2.6
0.0
0 0
3.6
0.0
0.0
2.6
0.0
3.1
0.0
0 0
5.6
0.0
0.0
1 2
0.0
2.6
0.1
3.9
0.0
0.0
1.6
0.0
0.6
0.0
0 0
2.4
0.0
0.0
2.1
0.0
4.7
0.2
0 0
7.1
0 0
0.0
1.8
0.0
8 9
0.2
327.0
337.8
0.0
0.0
0.3
0.0
2.2
0.0
0.0
2.5
4.5
0.0
12.5
0.0
12.6
0.3
0 0
29.8
3.3
0.0
6.8
0.0
11.7
0.7
0.0
22.5
3.1
0.0
9.8
0.0
5.5
0.1
0.0
18.5
0.8
0.0
12.4
0.0
21.2
1.3
0 0
35.7
4.5
2 0
11.2
0.0
38.4
1.1
685.0
742.0
2.2
0.0
2.7
0.0
10.1
0.0
00
14.9
Abbreviation: WWTPs. Wastewater treatment plants.
38
-------
Appendix B (continued)
Estuary
Source
Winter Spring Summer Fan
Total
Winter Spring Summer
FaD
Total
SheepscotBay
SaooBay
Great Bay
Memmack River
Mas
Agriculture
Forest
Urban
Other
WWTPe
Industry
UDStream
Total
Agriculture
Forest
Urban
Other
WWTPs
Industry
Uostream
Total
Agriculture
Forest
Urban
Other
WWTPs
Industry
Total
Agriculture
Forest
Urban
Other
WWTPs
Industry
'Total
ver Agriculture
Forest
Urban
Other
WWTPs
Industry
Total
i Bay Agriculture
Forest
Urban
Other
WWTPs
Industry
Total
79.0
20.6
41.1
0.5
18.0
2.0
1 459 0
1.620.1
184.9
23.4
79.0
0.0
103.0
81.0
0 0
471.4
23.9
1.8
26.8
0.0
39.5
9.1
216.0
317.2
96.2
3.2
83.5
0.0
60.2
2.8
0.0
225.8
36.0
0.0
1S3.0
0.0
342.0
9.0
2.880.0
7.9
123.3
449.2
14.4
1 .803. 1
4.0
0.0
2.201.9
100.4
9.0
57.5
0.5
18.0
2.7
3 gso 0
4.136.0
102.0
4.9
87.0
0.0
104.0
84.0
0 0
381.9
20 4
0.4
42.5
0.0
39 6
9.4
453 0
565.3
37.9
0.0
53.0
0.0
80.7
2.8
154.4
31.0
0.0
86.0
0.0
345.0
10.0
3.982.0
22.2
2.7
316.7
2.7
1.603.1
3.7
1.951.1
70.2
3.0
59.6
0.0
17.3
2.7
1 231 0
1.383.7
77.2
2.9
78.0
0.0
100.0
83.0
0 0
339.1
13.9
0.2
43.5
0.0
38.2
9.3
1030
208.1
28.8
0.0
71.2
0.0
58.5
2.8
0 0
181.2
15.0
0.0
175.0
0.0
333.0
9.0
2.172.0
19.1
142.7
447.7
20.0
1.603.1
4.4
0.0
2.237.0
3.6
0.0
28.8
0.0
15.3
2.0
1 555 0
1.604.4
3.8
0.0
40.0
0.0
67.0
81.0
0 0
21 1.8
0.4
0.0
21.5
0.0
32.7
9.1
103 0
166.7
1.4
0.0
40.3
0.0
50.2
2.6
0 0
94.7
2.0
0.0
118.0
0.0
288.0
9.0
1.097.0
4.8
2.5
235.3
2.3
1.358.4
3.4
0 0
1.604.5
263.1
32.6
186.6
1.0
68.6
9.4
8.195.0
8.746.2
367.9
31.3
282.0
0.0
394.0
329.0
0.0
1.384.2
88.8
2.4
134.3
0.0
160.1
38.8
8750
1.257.3
184.2
3.2
227.9
0.0
229.8
11.0
0 0
638.0
84.0
0.0
630.0
0.0
1.308.0
37.0
8.1540
53.8
271.2
1.448.9
30.4
8.165.7
16.6
0.0
7.994.5
1.0
0.0
8.4
0.0
13.9
0.0
131.0
152.3
1.9
0.0
13.0
0.0
69.0
33.0
0.0
116.9
0.2
0.0
4.5
0.0
26.7
3.7
50
0.7
0.0
10.5
0.0
40.3
1.7
0 0
53.1
0.0
0.0
86.0
0.0
213.0
0.0
1720
0.0
1.5
78.8
0.0
999.5
0.3
0 0
1.079.9
12.6
0.0
10.1
0.0
13.9
0.0
217.0
253.5
10.0
0.0
11.0
0.0
70.0
33.0
0.0
124.5
2.1
0.0
6.2
0.0
26.6
3.7
40.0
78.8
5.8
0.0
6.3
0.0
40.3
1.7
0.0
55.8
4.0
0.0
13.0
0.0
218.0
0.0
3030
3.1
0.0
64.5
0.0
999.5
0.3
0.0
1.057.4
1.8
0.0
10.1
0.0
13.2
0.0
84.0
108.9
1.0
0.0
13.0
0.0
87.0
33.0
0.0
1 14.0
0.1
0.0
8.5
0.0
25.5
3.7
4 0
39.7
0.7
0.0
11.0
0.0
39.2
1.7
0.0
0.0
0.0
28.0
0.0
207.0
0.0
134.0
0.0
1.3
89.1
0.0
999.6
0.3
0 0
1.070.2
0.0
0.0
3.4
0.0
11.9
0.0
112.0
127.2
0.0
0.0
7.0
0.0
58.0
33.0
0.0
96.0
0.0
0.0
2.8
0.0
21.5
3.7
60
34 0
0.0
0.0
6.1
0 0
33.7
1.7
00
0.0
0.0
19.0
0.0
178.0
0.0
113 0
0.0
0.0
38.4
0.0
845.8
0.3
0.0
882.5
15.0
0.0
29.9
0.0
52.9
0.0
544.0
641 .9
13.3
0.0
44.0
0.0
284.0
132.0
0.0
453.3
2.4
0.0
19.9
0.0
100.6
14.8
55.0
192.6
7.0
0.0
35.9
0.0
153.4
8.6
0 0
4.0
0.0
88.0
0.0
813.0
0.0
722.0
3.1
2.8
238.6
0.0
3.844.3
1.2
00
39
-------
Appendix B (continued)
Estuary
Source
Nitrogen
Phosphorus
Winter Spring Summer Fan Total
Winter Spring Summer
Fall
Total
Cape Cod Bay
Buzzards Bay
Norragansett Bay
Gardners Bay
Long Island Sound
Agriculture
Forest
Urban
Other
WWTPs
Industry
Upstream
Total
Agriculture
Forest
Urban
Other
WWTPs
Industry
Upstream
Total
Agriculture
Forest
Urban
Other
WWTPs
Industry
Upstream
Total
Agriculture
Forest
Urban
Other
WWTPs
Industry
Upstream
Total
Agriculture
Forest
Urban
Other
WWTPs
Industry
Upstream
Total
0.5
0.2
33.8
1.4
70.1
0.0
0 0
105.9
a.e
OM
. J
38.8
1 1
80.4
0.0
0.0
127.4
90.0
1.0
431.0
2.0
646.0
97.0
0 0
1.267.0
69.5
0.0
0.0
81.7
164.6
3.6
0.0
299.4
693.0
18.0
1.050.0
0.0
4.512.0
238.0
7.060.0
13.571.0
1.4
0.0
18.2
0.0
70.5
0.0
0 0
90.2
21.7
20.9
0.0
80.9
0 0
0.0
123.5
156.0
0.0
206.0
0.0
6S1.0
97.0
0.0
1.110.0
34.0
0.0
0.0
42.S
165.4
3.9
0 0
245.9
421.0
5.0
760.0
0.0
5.126.0
269.0
9.491 0
16.072.0
0.4
0.0
30.5
0.0
68.1
0.0
0 0
99.0
6.2
35.0
0.0
78.1
0.0
0.0
119.2
74.0
0.0
4S2.0
1.0
629.0
97.0
0 0
1.253.0
52 6
0.0
0.0
52.8
159.8
4.1
0 0
269.4
670.0
38.0
1.306.0
1.0
4.934.0
276.0
5.579 0
12.804.0
0.2
0.0
25.4
0.0
58.5
0.0
0 0
84.1
3.7
29.1
0.0
67.1
0.0
0 0
99.9
28.0
0.0
278.0
0.0
540.0
97.0
0 0
941.0
1.7
OM
.u
0.0
23.6
137.4
3.7
0.0
166.5
43.0
0.0
527.0
0.0
4.344.0
281 0
2,522 0
7.717.0
2.8
0.2
107.9
1.4
287.2
0.0
0.0
379.2
38.4
123.8
1.1
306.5
0.0
0.0
470.1
346.0
1.0
1.367.0
3.0
2.466.0
388.0
0 0
4.571.0
158.0
OM
.U
0.0
180.5
827.3
15.3
0 0
981.1
1.827.0
61.0
3.843.0
1.0
18.916.0
1.064.0
24.6S2.0
50.164.0
0.0
0.0
5.6
0.0
44.1
0.0
0 0
49.6
0.0
On
.w
8.4
0.0
50.5
0.0
0.0
56.8
1.0
0.0
70.0
0.0
403.0
1.0
0.0
476.0
0.6
0.0
10.2
102.3
3.8
0.0
116.9
6.0
0.0
173.0
0.0
1.187.0
4 0
527 0
1.897.0
0.2
0.0
2.9
0.0
44.5
0.0
0 0
47.6
2.5
On
• U
3.3
0.0
51.0
0.0
0 0
56.8
15.0
0.0
33.0
0.0
406.0
1.0
0.0
455.0
2.3
0.0
6.8
103.1
3.8
0.0
116.1
23.0
0.0
121.0
0.0
1.479.0
4.0
653.0
2.280.0
0.0
0.0
4.9
0.0
42.9
0.0
0 0
47.8
0.0
On
• U
5.6
0.0
49.3
0.0
0 0
54.9
1.0
0.0
72.0
0.0
392.0
1.0
0 0
466.0
0.9
0.0
8.5
99.9
3.8
0 0
113.1
6.0
0.0
215.0
0.0
1.263.0
4.0
424 0
1.932.0
0.0
0.0
4.2
0.0
36.9
0.0
0 0
41.2
0.0
On
• U
4 8
0.0
42.4
0.0
0 0
47 2
0.0
0.0
43 0
0 0
336.0
1.0
0.0
380.0
0 0
0.0
3 7
65.5
3.8
0 0
93.0
0.0
0.0
86.0
0.0
1.022.0
4.0
295 0
1.407.0
0.2
0.0
17.6
0.0
168.4
0.0
0 0
186.2
2.5
On
.u
20.2
0.0
193.2
0.0
0.0
215.6
17.0
0.0
218.0
0.0
1.537 0
4.0
0.0
1.778 0
3.7
0.0
29.2
390.9
15.3
0 0
439 2
35.0
0.0
595.0
0.0
4.971.0
16.0
1.899.0
7.516.0
40
-------
Appendix C. Nitrogen and Phosphorus Discharges by Source Category
Table C1 Nitrogen docharge by nonpont. point. and upstream spume category by estuary Cons P* »•") • area 1988
Estuary
Total
Nonpoinl
Port
Drscharge Estuary Total
PessarraquodtfyBay
Englishman Bay
Narraguagvs Bay
Blue Hill Bay
PenobseotBay
Muscongus Bay
SheepseotBay
CasooBay
SaooBay
Great Bay
Merrimack River
Massachusetts Bay
Cape Cod Bay
Buzzards Bay
Narragansen Bay
Gardners Bay
Long Island Sound
Regnral Totals
Estuiry
294
151
108
155
7.808
58
8.741
1.418
1.254
840
10.111
7.995
380
489
4.574
985
50.148
95.287
Total
192
124
93
107
352
44
474
667
193
397
614
1.814
113
183
1.713
341
5.528
12.929
65
62
88
89
4
76
5
47
15
82
6
23
30
35
37
35
11
14
t of
Discharge Estuary Total
102
27
13
48
178
14
77
751
186
243
1.347
6.181
287
306
2.681
644
19.993
33.236
35
18
12
31
2
24
1
S3
15
36
13
77
70
65
83
65
40
35
Upstream
Estuame Resource Base
Percent of
Discharge Estuary Total
0
0
0
0
7.280
0
8.190
0
875
0
8.150
0
0
0
0
0
24.627
49.122
0
0
0
0
94
0
94
0
70
0
61
0
0
0
0
0
49
52
Surface Area
Percent of
(aq mi) Regional Total
157
76
70
115
361
72
103
164
17
15
6
364
548
228
165
197
1.281
3.939
2
4 2
0 4
0 4
0 2
9 2
139
5 8
42
50
325
100
Agrfcuaura
Percent of
Dbchsrgs Emery Ton! Otadi
Forest
Percent of
•rge Estuary Total
ObcM
Urban
Percent ef
rot Esaury Total
Olaetianj
Otier
Percen q it)
Percent of
Regional Total
Pieumsouooay Bay
EngUinmin Bay
Nor.gu.gui Bay
Blue Hdl Bay
PenobscMfJay
UusoongusBay
Sheepscoiasy
Cisco Bay
Sara Bay
Grail Bay
Ueirlinack River
Muuetuwtts Bay
Cap* Cod Bay
BunirdiBiy
NimgansM Bay
Gardners Biy
Long Uland Sour*
1»2
124
93
107
392
44
474
6«7
1*3
197
614
1.SI4
113
163
1.713
341
5.S26
80
85
62
16
69
27
253
367
56
166
63
54
3
38
345
158
1.827
45
52
67
IS
17
61
S3
65
30
42
14
3
3
23
20
46
33
t
1
1
1
14
I
3
3
27
6
» to
» 12
1 •
9 9
7 42
) 0
I 7
9 4
t 1
1
0
IS
0
0
0
0
1 1
86
42
20
77
143
17
136
270
133
227
S31
1.449
108
124
1.383
163
3.639
4S
34
22
72
41
39
4O
40
69
87
60
30 4
96
70
30
54
«O
157
76
70
tts
361
72
163
164
17
IS
6
364
S48
226
16S
197
1.261
4 0
1 9
1 6
2 9
9 2
1 6
2 6
4 2
0 4
0 4
0 2
9 2
13 9
6 6
4 2
5 0
32 S
Regional Touts
12.929
3.667
28
6.600
67
62
3.939
Table C3 Nrtrooon oont source discharoe b
Estuary
v cateoorv bv eat
uarv (tona oar i
Total Wastewster Treatment Plants
Percent of
reer)
Industry
Estuame Resource Base
Pereont of Surface ATM Percent of
Drschsrge Eatuary Total Dscnsrge Estuary Total
Passamaqueddy Bay
Englishman Bay
Namguagua Bay
Blue H9I Bay
PenobscoiBay
Muscongus Bay
ShoapaeotBay
CasooBay
SacoBay
0 real Bay
Merrimack River
Massachusetts Bay
Caps Cod Bay
Buzzards Bay
NarraganaoB Bay
Gardinera Bay
Long Island Sound
102
27
13
48
176
14
77
751
186
243
1.347
6.181
287
306
2.861
644
19,993
16
17
8
30
77
13
67
408
149
230
1.310
6.166
267
306
2.470
828
18.922
18
63
62
63
44
93
87
54
80
97
97
100
100
100
86
98
95
84
10
5
18
99
1
10
343
37
13
37
15
0
0
391
18
1.071
62
37
38
37
56
7
13
48
20
3
3
0
0
0
14
2
5
(aq ml) Ragranal Total
157
76
70
115
381
72
103
184
17
15
8
364
546
228
165
197
1.281
4
1
1
2
9
1
2
4.
0
0
0
9
13
5
4
5
32
Regional Totals
33.236
31.068
94
2.150
3.939
100
41
-------
Appendix C (continued)
Table C4 Phosphorus discharge by nenpoml, pomt. and upstream source e»l«qory by estuary (tons per year) • ore* 1962
Estuary
Total
NonpoM
Percent ol
Discharge Estuary Total
Passamaquoddy Bay
Englishman Bay
Narraguagua Bay
Blue Hill Bay
PenobsootBay
Museongus Bay
ShoepacotBay
CascoBay
San Bay
Great Bay
Mernmack River
Massachusetts Bay
Cape Cod Bay
Buzzards Bay
Nairagsnsett Bay
Gardiner* Bay
Long Wand Sound
Regional Totals
32
23
12
37
775
15
641
471
195
203
1.628
4.091
185
218
1.778
440
7.527
18.269
Time C5 PKosDhoru* nonpoM olsehsros by eal
Estuary
Total
Disci
19
10
8
14
28
5
48
58
24
43
90
246
17
23
234
33
828
1.524
leoorv bv ectuarv Rons i
Agrleukure
Percent of
woe Eatiary Tots)
59
43
50
38
4
33
7
12
12
21
8
6
9
11
13
8
8
8
Mr year)
Otscr
Pont
Upstream
Percent of Per
Discharge Estuary Total
13
13
6
23
61
10
52
413
116
160
816
3.845
168
193
1.544
407
5.000
12.840
Forest
Percent ol
large Estuary Total
41
57
SO
62
1
67
1
68
59
79
50
94
91
89
87
92
66
70
Ofcjehsrg
Estuanno Resour
cent el Surface Area
Dacharge Estuary Total
0
0
0
0
686
0
543
0
55
0
722
0
0
0
0
0
1.898
3.905
IMsn
Percent ol
e Estoary Total
0
0
0
0
88
0
65
0
26
0
44
0
0
0
0
0
25
21
0
Hacharge
DS Base
Percen ol
(aq mi ) Regional Total
157
76
70
115
381
72
103
184
17
15
8
384
548
228
185
197
1,281
3.939
tier
Percent of
Estuary Total
40
1 9
1 8
28
92
1 8
26
42
0 4
0 4
02
92
13 9
58
42
50
325
100
Eskarine Resource Base
Surface Area Percent ol
(sq ml) Regional Total
PaaeanwaiedayBey
En^ufwnijn Bey
Narraguegu* Bey
Bue Hi! Bay
PenabeoMBsy
MusconousBay
Shoopseataay
Caaoo Bay
SecoBsy
Great Bay
Merrtmack River
MasaachJseasBay
Cape Cod Bay
Buzzards Bay
Narraganaett Bay
Gardner* Bay
Long Island Sound
19
Id
d
14
28
S
46
58
24
43
• 0
246
17
23
234
33
628
S
3
3
t
4
2
14
13
2
7
4
3
0
3
17
4
38
26
30
60
7
14
4d
30
22
8
16
4
1
0
13
7
12
6
14
7
3
13
23
3
32
48
22
36
16
239
17
20
217
29
SIB
74
70
60
93
82
60
70
78
• 2
14
66
97
0
87
93
66
94
187
76
70
118
361
72
103
164
17
16
6
364
S46
228
165
197
1.281
4 0
1 9
1 8
29
92
1 6
26
42
04
04
62
92
139
58
42
5 0
12 5
Rogtonal Totate
1.524
123
1.395
92
3.939
100
Table C6 Phosphorus polr
Eetuary
Pasaarnaejuoddy Bay
Englishman Bay
Narraguagua Bay
Blue Hill Bay
PenobsootBay
MuscofiQua Bay
ShaepacM Bay
CascoBay
SaooBay.
Gnat Bay
Marrlmack River
Massachusetts Bay
Cape Cod Bay
Buzzards Bay
Narraganeen Bay
Gardners, Bay
Long Island Sound
it source discha
Total V
13
13
6
83
61
10
52
413
116
160
816
3.845
166
193
1.544
407
5.000
roe bv cateoon
Vaatewaler Tre
Discharge
13
12
B
21
67
10
52
273
101
153
814
3.844
168
193
1.540
391
4.960
I by estuary (tone
aimer* Plants
Percen of
Estuary Total
100
92
100
91
03
100
100
66
87
96
100
100
100
100
100
06
100
per vear)
Ind
Discharge
0
1
0
2
4
0
0
140
IS
7
2
1
0
0
4
16
20
ustry
Percen of
Estuary Total
0
34
13
4
0
0
0
0
0
4
0
EstuartneRe
Surface Area
(sq. ml.)
157
76
70
115
361
72
103
164
17
IS
6
384
548
226
165
107
1.261
source Base
Percent of
Regional Total
4.0
1.9
1.8
2.0
9.2
1.8
2.6
4.2
0.4
0.4
0.2
0.2
13.9
5.8
4.2
5.0
32.5
Regional Totals
12.840
12.628
08
212
3.939
100
42
-------
Appendix D. Accuracy of the Discharge Estimates
Inherent in any data set are limitations on quality and accuracy. The nutrient discharge data presented
in this report were based on a number of factors and assumptions discussed below. Source categories
differ in their complexity and in the amount and accuracy of data available to verify discharge estimates.
Discharge estimates will vary by season, precipitation, terrain, land use, and economic activity. Point
sources are generally less complex and variable than nonpoint and upstream sources. Nutrient
concentrations from point source discharges are easier to obtain and measure, and hence, have higher
quality estimates. Within the point source categories, wastewater treatment plants are easier to
characterize than industrial facilities, and within the industrial category, simple industries (such as cement
or glass) are easier to characterize than more complex industries (such as petrochemicals). In nonpoint
source categories, better estimates are available for crop land than forestland. Urban storm runoff and
combined sewer overflows are highly variable, have limited data, and are difficult to characterize. Upstream
sources have the most variability, and the relationship between flow and pollutant load is not well captured
in the NCPDI estimates.
The data range in quality from excellent to highly speculative and are a function of discharge variability
and data availability. A five-point scale was used covering certain ranges of accuracy to assess data quality,
as shown in Table 01. The discharge variability ranges from low to high depending on whether it is from an
end-of-pipe constant discharge (low) or from land runoff (high).
Table D1. Data Quality Assessment - Accuracy of nutrient discharge data
Data Quality Discharge Variability Error Range (%) Data Availability
(1) Excellent Low ±10-20 Good
(2) Good Moderate ±20-50 Good to Moderate
(3) Fair Moderate to High ±50-100 Limited
(4) Poor High 100 Limited to None
(5) Unknown High 100 Limited to None
Depending upon the type of source discharges within an estuarine system, the quality of the
estimates may vary. For example, a system whose nutrient loads were dominated by WWTPs and
agriculture may have more accurate discharge estimates than one dominated by upstream riverine inputs
and urban runoff. Table D2 shows the relative differences in data quality between source categories and
nutrient discharge data, and Table D3 shows the relative quality of the factors used in estimating nutrient
loadings.
The quality of background data in Table 4 ranges from excellent to fair depending on the accuracy of
records, age of data, and minor variations that occur at the site-specific level. These are reliable data and
are easily measured. These data are used in calculating nutrient discharge by source category. Some
errors are introduced when the data may be averaged or prorated for input to the estimation procedure.
For example, rainfall may be averaged over a time interval of occurrence, or population or fertilizer
application may be prorated over a given land area. The accuracy of the estimates will depend on the
reliability of the background data in combination with the source category, pollutant, and the time and
space scale considered.
43
-------
Table D2. Data Quality Assessment - Discharges by source category for the Northeast
Source Category
Non point
Agriculture
Forest
Urban
Other
Point
WWTPs
Industry
Upstream
Upstream
Nitrogen Phosphorus Comments
Annual Seasonal Annual Seasonal
2-3 3-5 2-3 3-4 Flow and erosion modeled, dally simulation, nitrogen and phosphorus
data (ram fertilizer, discharge highly variable
3.4 3-5 3.4 3-4 Modeled soil erosion similar to cropland, lunoff less known or studied
than agriculture land
3.4 3-5 3-4 3-5 Flow Is modeled, dally simulation and WWTP capacity, bypass assump-
tions are conservative, nutrient toad highly variable
2.3 3.5 2-3 3-5 Modeled similar to agriculture and forest land, erosion a function of
ground cover, highly variable
1-2 1-2 1-2 1-2 Row and nutrient levels fairly constant by treatment levels, nitrogen
and phosphorus often not permitted, actual discharge may vary
1-3 2-3 2-3 2-3 Greater variation In seasonal How. nutrient levels, and treatment
performance, nitrogen and phosphorus often not permitted
2-5 3-5 2-5 3-5 Flow data more regularly collected than nutrient concentrations, high
short term variability, monitoring often misses major storm activity
Numerical Ratings: 1. Excellent: 2. Good; 3. Fair; 4. Poor; 5. Unknown
Abbreviation: WWTPs. wastawaier treatment plants.
Nonpolnt Source Discharges. The quality of data for nonpoint sources ranges from good to unknown and
is a function of the accuracy of the various parameters used in calculation discharges. Site-specific
variations in land use types, soils, fertilizer applications, precipitation, and runoff coefficients are
represented by basin drainage. This assumes implicitly that for such an area, the factors most important for
the calculation of sediment and nutrient discharges do not vary significantly and are well represented by
average values. This may not always be valid because of the variability in soil type, topography,
management practices, and ground cover. Hence, discharge estimates for these categories vary in quality
as a result site variability.
Agriculture. Fertilizer application rates were based on the best available data to date. Soluble nitrogen
and phosphorus discharges were generalized based on state records of use and fertilizer sales. Lands
such as nurseries, golf courses, and urban lawns were excluded. A fixed percentage of applied nutrients
was assumed lost to surface runoff. Actual percentages vary and are not well represented by a single
value. Variability, resulting from application rates and timing, mode of application, fertilized crop types,
storm events, and physical characteristics of the fertilized areas, was not considered. However,
conservation versus conventional tillage was considered.
The validity of the SWRRB model was tested using several watersheds in a study conducted by the
Chesapeake Bay Program. The model was found to be accurate to ±30 -100 percent for runoff and ±30 -
150 percent for soil erosion. While this is within the state-of-the-art for nonpoint source modeling, it
indicates that these estimates are highly variable and difficult to model accurately.
Forest. The data quality range from fair to unknown. Less detailed information is available for forestland,
and little is known about runoff or credibility. The amount of ground cover in a deciduous forest will vary
and will affect the amount of rainfall energy reaching the ground due to the presence of forest litter. Little
has been done on the leaching of nutrients from decaying plants. The process is slow and can be
considered negligible in relation to nutrient discharges from eroding of soil.
44
-------
Table D3. Data Quality Assessment - Background data
Background Data Annual Seasonal
Category
Comments
Precipitation
Land Use 2 - 3
Population 1 - 2
Fertilizer Use 2-3
Fertilizer 2
Seasonality
Number of WWTPs 1
Number of
Industrial Plants
Planting and
Harvesting dates
1 Orographic differences between sites in hilly areas, especially in
New England
N/A Variations in age of data and population changes in region since data
collected (particularly Maine and Cape Cod)
N/A Some errors in proration to estuarine drainage areas and in rapidly
growing areas
N/A Variations between states in accuracy of records; errors introduced
in prorating sales to crop acreage
2 • 3 Runoff coefficient based on average of field studies; some errors
introduced at site-specific level
N/A Publicly owned facility characteristics contained in EPA Needs
Survey
N/A Plants listed through NPDES permit programs; some minor or
intermittent dischargers may have been omitted
1 Determined by regional temperature regimes; some annual variation
between sites or crops
Numerical Ratings: 1. Excellent; 2. Good; 3, Fair
Abbreviations: WWTPs. Wastewater treatment plants; NPDES. National pollution discharge elimination system;
N/A. not applicable
Urban. The estimate of runoff volumes depends upon the quality of the land use data, precipitation data.
and runoff coefficients. The accuracy of the calculated estimates of urban storm runoff volumes and
loadings depends upon the overall accuracy of the runoff volume estimates and the use of average
pollutant concentrations. The amount of urban areas served by CSOs was taken from the Needs Survey
(EPA, 1982), is up to date, and is the best single source of these data.
Precipitation and weather data are from NOAA. Readings are taken continuously with state-of-the-art
instrumentation, and the data are considered good quality with a good density of weather stations. Land
use data from the USGS LU/LC program are 6 to 12 years old and are the best available on a national basis.
Runoff coefficients are based on EPA-conducted studies on runoff/rainfall relationships for impervious
areas. A 90 percent confidence interval was determined for each area, and a median runoff coefficient
calculated (EPA, 1983b). These data are considered good quality. Some error is introduced when
different runoff coefficients are applied to site-specific land use mixes. Certain land uses, such as
construction and mining operations, were not accounted for by urban definition and are not included in
nonurban runoff methodology. Even though construction work is temporary, large sediment loads are
nearly always associated with it.
Nutrient concentration estimates are the weakest link in urban runoff discharge estimates. The data
do not reflect local storm variability. The variation within storms is not reflected in the calculated discharge.
However, use of averaged concentrations is an accepted technique to avoid overestimation of the initial
discharge.
45
-------
Point Source Discharges. Point source data are the most accurate and range in quality from excellent to
fair. The accuracy and completeness of these data are a function of the quality of flow and concentration
data. Estimated flows and permit limits produce less accurate estimates than measured values.
Wastewater Treatment Plants. Flow data from WWTP discharge pipes are generally accurate and more
easily measured. WWTPs receive fairly constant inflows and have storage facilities for flow equalization.
The discharge estimation procedure assumes the same number of operating days and similar discharge
patterns for all facilities for all seasons. Nitrogen and phosphorus concentrations are generally estimated
based on similar treatment efficiency and technology for WWTPs. They are not subject to discharge
permits so that detailed information is not available. The data, however, are considered generally good,
with the best available for major WWTPs.
Industry. Industrial flow from major facilities is usually measured, and hence, the data are generally
accurate. Flow data from minor facilities is either estimated or based on design flow. These data are
considered a good estimate of wastewater discharge volumes. Nutrient discharges are either monitored
or estimated based on similar facilities with similar flow volumes. Industrial discharges, however, vary
seasonally and between industries and may introduce some error.
Upstream. Loadings calculated from this source category are classed in the good to unknown range.
Flow from upstream sources is highly variable and seasonal. Nutrient data are also not always available,
and in some cases, no flow or discharge data were available. Estimates were made for these streams
based on values from nearby streams with similar flows and land use characteristics for which monitored
data were available.
Flow information is generally collected on a regular basis but not always at the point of entry into an
EDA. A problem with respect to the accuracy of upstream discharge estimates is the spatial overlap
between the NCPDI study area and the NEI study area. In cases where the EDA extends beyond the
coastal county boundary, nutrient discharge data may be underestimated. The EDA extends beyond ten
estuarine systems in the Northeast. In cases where the EDA is fully within the coastal county, the nutrient
discharge data may be overestimated. This would apply to seven estuarine systems for the region.
Although this may only slightly affect overall nutrient discharge totals for a particular estuary, these spatial
considerations need to be taken into account when using these data.
46
-------
Appendix E. Computing Dissolved Concentration Potential
The approach used to develop the dissolved concentration potential estimates (Ketchum, 1955)
assumes that pollutant behavior can be inferred by the knowledge of how freshwater inflow is flushed
from the estuary and diluted by seawater. The average salinity concentration in an estuary is assumed to
be indicative of the concentration of a conservative pollutant in the system. The physical forces of tide.
freshwater inflow, and wind affect the distribution of a pollutant in an estuary as they do in freshwater.
The OOP estimate assumes that an initial concentration of a pollutant is equal to the pollutant load per
unit time divided by total average daily freshwater inflow. This initial concentration is multiplied by the ratio
of the volume of freshwater to seawater in an estuary to arrive at a DCP estimate. This is represented as:
DCP= Cinjtx Freshwater Fraction (y
where: Cjnit = pollutant loading rate / freshwater inflow
fQ = volume of freshwater / volume of seawater.
For purposes of comparison, an equal pollutant load is assumed to be discharged to all estuaries
identified in NOAA's National Estuarine Inventory (NEI), including the 17 in the Northeast. This enables a
direct comparison of the flushing and dilution characteristics as they affect potential pollutant
concentrations. The same approach is used with actual loadings to estimate concentrations to
characterize present status.
The DCP estimate is determined for average annual conditions of freshwater inflow and salinity. The
latter represents the mix of fresh and salt water within an estuary as it is affected by freshwater inflow, wind,
tide, and adjacent shelf dynamics. Volumes of fresh and salt water are estimated for the three salinity
zones (tidal fresh: 0-0.5ppt, mixing zone: 0.5-25ppt; seawater zone: > 25ppt) as depicted for each
estuary in the NEI Volume 1 and summed to obtain system totals.
The method assumes vertical and lateral mixing. The DCP estimate has limited utility in estuaries
where salinity stratification persists for significant periods. In addition, the DCP calculation is highly
dependent on the existence and accuracy of a freshwater signal in the average annual salinity structure.
As a consequence, the DCP estimate has little meaning in systems where average annual salinity
approaches that of seawater such as in Cape Cod Bay. Table 1 shows the DCP estimate, volume, average
daily freshwater inflow, average annual salinity, intra-annual salinity variability (as per NEI Vol.1), and
degree of stratification
The DCP estimate is most sensitive to the average annual salinity, and is dependent on the accuracy
to which average salinity can be estimated. In addition, sensitivity increases as the average annual salinity
of the system increases. Figure 1 shows the proportionately greater effect that a percent increase in the
average annual salinity will have on a percent change in DCP. For example, an estuary having a 25ppt
average annual salinity with a 10 percent over estimation in average annual salinity would have a
corresponding 30 percent change in DCP. In contrast, a system with the same 10 percent error but
whose average annual salinity is 20ppt would realize only a 10 percent change in its DCP. The percent
change in the DCP estimate is depicted for increases in salinity, since this provides a greater effect on
DCP estimates when compared to similar percent decreases. This is due to overall sensitivity of the DCP
calculation to higher average annual salinities as mentioned previously.
Estuaries whose average annual salinities are in excess of 25ppt, however, tend to be more stable
and less susceptible to errors in salinity. This is because the overriding influences on salinity are oceanic
(i.e. tidal). They exhibit a greater degree of predictability compared to estuaries dominated by freshwater
inflows. Errors in estimating the average annual salinity for these estuaries in excess of 10% are unlikely.
In comparison, estuaries with an average annual salinity of less than I5ppt are less stable and are
susceptible to greater errors in salinity determination. However, the overall effect on the DCP estimate in
these cases is minimized because the DCP estimate is not as sensitive to average annual salinities at the
lower ranges.
47
-------
Table E1. Selected physical charateristlcs and dissolved concentration potential for the Nation's estuaries.
Estuary Dissolved Volume
Concentration
Potential 10
mg/l cubic feet
Passamaquoddy Bay
Englishman Bay
Narraguagus Bay
Blue Hill Bay
Penobscot Bay
Muscongus Bay
Sheepscot Bay
Casco Bay
Saco Bay
Great Bay
Merrimack River
Massachusetts Bay
Cape Cod Bay
Buzzards Bay
Narragansett Bay
Gardiners Bay
Long Island Sound
0.266
0.918
1.538
1.031
0.134
2.249
0.088
0.613
0.454
1.536
1.011
0.273
0.688
1.042
0.523
1.774
0.054
315.3
79.7
63.3
241.1
724.6
85.5
118.4
191.3
15.3
4.7
2.1
785.0
1177.8
215.0
139.1
111.1
2190.0
FW Inflow
Avg. Daily
lOOOcfs
6.2
1.6
0.9
1.3
16.1
0.6
17.6
2.1
3.6
2.0
8.4
2.9
1.8
1.2
3.2
0.7
30.0
Salinity
Average Intra-annual
Annual variability
PPt
27.7
28.2
28.5
28.7
26.1
28.6
28.0
28.8
27.7
23.2
5.6
30.5
29.0
28.9
27.6
29.0
27.7
M
M
H
H
H
M
H
M
H
H
M
L
L
M
M
L
M
Stratification
3-Mo. Hi Flow
Strat. Class.
MS
HS
HS
HS
HS
HS
HS
MS
HS
MS
MS
VH
VH
VH
VH
VH
VH
3-Mo. Lo Row
Strat. Class.
MS
MS
HS
HS
MS
MS
MS
VH
HS
VH
VH
VH
VH
VH
VH
VH
VH
Abbreviations: mg/l, milligrams per liter; cfs, cubic feet per second; FW, freshwater;
ppt, parts per thousand; 3-Mo., 3 month; strat. class., stratification classification
Figure E1. Sensitivity of DCP estimate
100% 1
80
60
40
20
0
10 15 20 25
Average Annual Salinity (parts per thousand)
48
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