National Water Quality Inventory:
Report to Congress
U.S. Environmental Protection Agency 10/29/2024
EPA Report # 841-R-23-001
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Table of Contents
Summary of National Water Quality 4
Biological Indicators 5
Chemical and Physical Indicators 5
Recreational and Human Health Indicators 5
State and Tribal Results 6
Introduction 7
National Aquatic Resource Surveys 8
Rivers and Streams 10
Key Findings of the National Rivers and Streams Assessment 2018-2019 10
Biological Indicators 10
Chemical Indicators 10
Physical Habitat Indicators 11
Human Health Indicators 11
Regional, State, and Local Results 11
Lakes, Ponds, and Reservoirs 12
Key Findings of the National Lakes Assessment 2017 12
Trophic Indicator 12
Biological Indicators 13
Chemical Indicators 13
Human Health Indicator 13
Physical Habitat Indicators 14
Regional, State, and Local Results 14
Wetlands 15
Key Findings of the National Wetland Condition Assessment 2016 15
Biological Indicators 15
Chemical Indicators 16
Physical Indicators 16
Human Health Indicator 16
Regional, State, and Local Results 16
Coastal Estuaries 17
Key Findings of the National Coastal Condition Assessment 2015 17
Ecological Indicators 17
Human Health Indicators 18
Regional, State, and Local Results 18
Great Lakes Nearshore 19
Key Findings for the Great Lakes Nearshore Waters NCCA 2015 19
Ecological Indicators 19
Human Health Indicators 20
Regional, State, and Local Results 20
Comparisons Across the National Aquatic Resource Surveys 21
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Biological Indicators 21
Chemical Indicators 21
Nutrient Pollution 21
Physical Habitat Indicators 22
Sediment and Soil Quality 22
Vegetation and Disturbance 22
Human Health Indicators 23
Key Stressors Associated with Poor Biological Integrity 23
State 305(b) Assessment and Reporting 25
References 28
Cover Photo: Willow Lake, White River National Forest, Silverthorne, Colorado. Sampled by Great Lakes Environmental Center.
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Executive Summary
2022 marked the 50th anniversary of the Clean Water
Act (CWA), a significant expansion of the first major U.S.
law to address water pollution. One of many CWA
successes to celebrate is the formation of unique
partnership among EPA, states, and Tribes to report on
water quality. Authorized under CWA Section 104 and in
support of CWA Section 305, EPA, states, and Tribes
implement the National Aquatic Resource Surveys
(NARS), a cost-effective program to monitor and assess
the condition of the nation's waters, to evaluate key
stressors, and track changes over time. Whereas in the
1974 Report to Congress EPA reported on 22 major
waterways, because of the NARS partnership this report
now covers 1.5 million miles of rivers and streams, as
well as lakes, coasts, and wetlands (EPA 1974).
This National Water Quality Inventory Report focuses on
the findings of the statistically representative National
Aquatic Resource Surveys. It also summarizes how site-
specific assessment results are reported by the states in
their Integrated Reports under Clean Water Act Sections
305(b). 303(d) and 314 and points to where results at
the state and local scale can be found. While different in
design, methods and goals, these two sources of
information complement each other to support decision
making at the national, state, and local level.
Summary of National Water Quality
National, statistically representative surveys provide
assessments of water quality based on consistent
sampling at randomly selected sites across the United
States. Rotating among water body types, each of the
national surveys are designed to address questions such
as:
What is the condition of the nation's waters?
What are the most widespread problems?
Are conditions improving or getting worse?
This report focuses on results at the national scale. The
surveys use selected indicators to assess the biological,
chemical, and physical condition of waters, as well as
characteristics that pose risks to human health. EPA and
its state and Tribal partners determined that the
indicators align with the survey goals and are
representative at a national scale. The following surveys
are described in this report:
Rivers and Streams: The National Rivers and Streams
Assessment was conducted in 2018-2019. Total extent
of waters assessed was 1,543,290 river miles.
Lakes, Ponds, and Reservoirs: The National
Lakes Assessment was conducted in 2017. Total
extent of waters assessed was 224,916 lakes
and reservoirs.
Wetlands: The National Wetland Condition
Assessment was conducted in 2016. Total extent of
waters assessed was 95,694,241 acres.
Coastal Estuaries: The National Coastal
Condition Assessment was conducted in 2015.
Total extent of estuarine waters assessed was
27,479 square miles.
Great Lakes Nearshore Waters: The Great Lakes were
monitored as part of the National Coastal Condition
Assessment that was conducted in 2015. Total extent
of Great Lakes nearshore waters assessed was 7,118
square miles.
For regional results and more information on the
national statistical surveys, visit the National Aquatic
Resource Surveys Website.
Biological Condition Across Water Types
Rivers &
Streams
Lakes
Wetlands Estuaries Great Lakes
28%
43%
47%
31%
25%
29%
19%
71%
15%
21%
47%
24%
34%
15%
7%
7%
33%
Ĥ Good
Fair Ĥ
Poor
Not Assessed
Figure 1. Using benthic macroinvertebrates, rivers and streams
had the smallest percent of waters in good condition (30%) while
31% of Great Lakes nearshore area, 43% of lakes and 71%
of estuarine square were also in good condition. 47% of wetland
acres were in good condition based on vegetation.
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Biological Indicators
The biology of a water body can be characterized by the
presence, number, and diversity of macroinvertebrates,
fish, vegetation, zooplankton and other organisms.
These indicators provide information about the health
and productivity of ecosystems.
To assess biological condition, each of the surveys used
indicators applicable to the water body type. Based on
information from the most recent reports in the NARS
program the percent of waters in good biological
condition ranged from 28% to 71% depending on the
waterbody type and the indicator.
As part of NARS, the EPA, states, and Tribes also
assessed fish communities in rivers and streams and
zooplankton in lakes finding 35% and 54% were in good
condition, respectively.
Poor biological condition is:
Almost twice as likely in wetlands when heavy
metals are present in soils at elevated
concentrations, phosphorus is high, or natural
vegetation in the surrounding area is altered.
Almost two times more likely in lakes or rivers
and streams when nutrients are high than in
waters where nutrients are not high.
Additional analysis estimates that reducing these
stressors could improve biological condition in 8 to 36%
of waters currently in poor condition.
Chemical and Physical Indicators
In the aquatic environment, a stressor is anything that
can adversely affect the community of organisms
residing there. For NARS, specific chemical and physical
stressor indicators were selected for sampling because
the stressors are widespread, are of potential concern
and can be cost-effectively measured. These indicators
of stress were not intended to be all-inclusive.
NARS results indicate that nutrients and degraded
habitat are pervasive issues impacting our waters across
the country. Excessive levels of phosphorus are reported
in 42% of river and stream miles, 45% of lakes and
approximately 20% of coastal water square miles.
Habitat degradation is also widespread across the
country with 36% of wetland acres, 29% of lakes and
27% of river and stream miles in poor condition.
Recreational and Human Health Indicators
NARS assessments also include information on
microcystin a toxin that can be produced from
cyanobacteria blooms. Recreational exposure is
typically a result of skin contact or accidental ingestion.
Health effects of exposure include skin rashes, eye
irritation, respiratory symptoms, gastroenteritis, and in
severe cases, liver or kidney failure and death. For
NARS, microcystin results were compared to the EPA's
recreational freshwater criteria and swimming advisory
recommendation of 8 ppb. Microcystins were detected
in 21% of lakes but at levels of concern in 2% of lakes,
representing 4,400 lakes across the nation. NARS also
found that microcystins were detected in 9% of river
and stream miles, 8% of wetland acres, and 6% of
coastal square miles but at levels of concern in <1% of
these waters.
When contaminants enter the aquatic environment,
they can accumulate in fish and may reach levels of
concern for people who eat fish. Collection of whole
fish composite samples in the Great Lakes nearshore
waters and in rivers found ali samples had detectable
levels of mercury and polychlorinated biphenyls
(PCBs), and more than 92% of the samples contained
detectable levels of perfluorooctane sulfonate (PFOS).
Fetal or early childhood exposures to mercury can
lead to impaired neurological development, and long-
term exposures among adults can lead to
cardiovascular disease (EPA 2001). PCBs are classified
as a probable human carcinogen and may also lead to
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neurological effects in infants and young children, or
liver disease or reproductive impacts in adults (EPA
1996). PFOS has been linked to immune,
cardiovascular, hepatic (liver), and developmental
health effects, as well as an increased risk of certain
cancers (EPA 2024).
Mercury concentrations in fish fillet composite
samples exceeded EPA's national recommended CWA
section 304(a) fish tissue-based water quality criterion
for methylmercury (300 ppb) in 13% of the 6,862
square miles of the assessed Great Lakes nearshore
waters and 26% of the 41,099 river miles comprising
the sampled populations. Fish fillet tissue sample
results in this summary report are compared with the
PCB screening level (12 ppb) for cancer effects
associated with general fish consumers (those who
eat one 8-ounce serving of fish per week).
Exceedances of the EPA's PCB fish tissue screening
level were identified in 45% of the sampled
population of river miles and 79% of the Great Lakes
sampled population. When compared to the PCB
screening level of 2.8 ppb for cancer effects
associated with high-frequency fish consumers, such
as subsistence fishers or some recreational fishers,
exceedances of this screening level were identified in
74% of the sampled population of river miles and
100% of the Great Lakes sampled population) (EPA
2023c and EPA 2021c).
State and Tribal Results
States and Tribes employ a range of approaches to
monitor and collect water quality data to support
protection and restoration decisions at the state, Tribal
and local levels, including submission of water quality
assessment reports to EPA. State and Tribal assessments
are based on data collected using a variety of sampling
methods and parameters, water quality standards,
assessment methods, and time periods. As states submit
their Integrated Reports and Tribes submit their
assessment reports, the information is updated online
at How's My Waterway. How's My Waterway was
designed to make these assessment reports accessible
to the public and present water quality information in
an easy to navigate and interactive format. Water
quality information is displayed on three scales in How's
My Waterway, community, state and Tribal, and
national.
Enterococci are bacteria that are used as indicators of
possible fecal contamination from sources such as
wastewater treatment plant discharges; leaking septic
systems; stormwater runoff; animal waste; and runoff
from pastures, feedlots, and manure storage areas.
Results were compared to an EPA benchmark (1,280
calibrator cell equivalents per 100 milliliters) included
in EPA's recommended recreational criteria document
for protecting human health in ambient waters
designated for swimming (U.S. EPA 2012). Nationally,
enterococci levels were at or below the EPA
benchmark in 99% of estuarine waters and Great
Lakes nearshore waters, and 78% of rivers and
streams.
For information on human health risks in specific
waterbodies, people should check with state, Tribal or
local governments before swimming, boating, or fishing.
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introduction
In recognition of the 50th Anniversary of the Clean Water
Act (CWA), EPA, Congress and the public celebrated the
many benefits of the nation's commitment to clean
water. The CWA established an objective to "restore and
maintain the chemical, physical, and biological integrity of
the Nation's waters." (CWA Sec 101).
Congress included mechanisms for monitoring and
reporting on water quality as a fundamental component
of the CWA. Two sections of the CWA were important
for addressing the information gap: Section 305(b) and
Section 104(a)(5). Section 305(b) calls for states to
submit a "description of the water quality of all
navigable waters; the extent to which all navigable
waters of such State provide for the protection and
propagation of a balanced population of shellfish, fish,
and wildlife, and allow recreational activities in and on
the water." Section 104(a)(5) calls for the development
of a national water quality monitoring and surveillance
system designed to inventory and determine the quality
of all navigable waters in the nation.
The authors of the CWA understood that monitoring
and reporting efforts were critical for knowing now and
in the future how well we are doing to meet the CWA
objective. Along with Sections 104 and 305, there are
additional provisions for monitoring and reporting. For
example, Section 106(e) requires states to implement
monitoring programs as a prerequisite to receiving
grants to administer water quality management
programs; Section 303(d) requires lists of waters that do
not meet state or Tribal water quality standards and do
not have a Total Maximum Daily Load identifying
pollutant reductions needed to meet standards; Section
314 calls for tracking the trophic state of lakes; and
Section 319 includes monitoring of nonpoint sources of
pollution.
Fifty years ago, even twenty years ago, we could not
answer questions such as what extent of waters are
healthy or degraded, how widespread are key stressors,
is water quality getting better or worse, and are we
investing effectively in protection and restoration?
Despite advances in monitoring and assessment
programs, during the first 30 years of CWA
implementation, it was widely recognized that the state
Section 305(b) reports were too disparate to describe
the condition of the Nation's waters. While the state
water quality reports were, and continue to be, valuable
for the individual states, numerous independent and
internal reviews found the differences in methods
across states prevented valid national level reporting.
Even the national newspaper, USA Today, called out the
importance of having data available on the condition of
the nation's environmental resources in article
published September 26, 2002. It reported that EPA was
able to demonstrate progress in improving air quality
but lacked consistent and representative data to report
on the condition of the nation's waters. They pointed
out that "without such data, the public doesn't know
when to celebrate environmental successes, tackle new
threats, or end efforts that throw money down the
drain."
One of many CWA successes to celebrate is the
formation of unique partnership among EPA, states and
Tribes in response to these critiques. Authorized under
CWA Section 104 and in support of CWA Section 305,
this partnership initiated the National Aquatic Resource
Surveys, a cost-effective program to monitor and assess
the condition of the nation's waters, to evaluate key
stressors, and track changes over time. 50 years after
the passage of the CWA, this report celebrates how far
we have come to address the need for information on
the quality of our waters.
Today, this document, the National Water Quality
Inventory: Report to Congress, provides national level
water quality conditions summarizing the results of
statistically-representative, nationally consistent aquatic
resource surveys conducted by the EPA in partnership
with state and Tribal water quality agencies. The report
describes the responsibilities of states and Tribes for
monitoring and assessment reporting and provides links
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to the How's My Waterway website. How's My
Waterway contains summaries of the water quality
assessment reports submitted to EPA and serves water
quality data and information at the community level.
State and Tribal monitoring and assessment reports
provide information needed to support management
decisions under their jurisdictions. This includes setting
water quality standards, monitoring and assessing water
quality, permitting point source discharges, and
developing plans to safeguard and restore water
resources. Under the CWA, each state or Tribe sets its
own water quality standards, including designated uses,
narrative and numeric water quality criteria, and
antidegradation policies. They develop assessment
methodologies and monitoring strategies. These may
differ among states and Tribes. Thus, the assessment
decisions reported by states and Tribes and summarized
in How's My Waterway apply to the individual states or
Tribes. Because of differences across programs there
are challenges associated with using state and Tribal
assessment decisions to compare water quality
conditions among states and Tribes and collectively they
cannot be used for reporting national water quality
conditions and trends
EPA, states, and Tribes along with other federal
agencies, research organizations, and volunteer
scientists employ a wide range of approaches to collect
water quality information for a range of high priority
needs. Much of these data are shared through the
Water Quality Portal so data can be used beyond its
initial purpose and strengthen decision making. The
national surveys and the individual state and Tribal
assessments have different goals and approaches, and
each provides valuable information that contributes to
our overall picture of nationwide water quality as called
for in Section 305(b) of the CWA.
National Aquatic Resource Surveys
Known as the National Aquatic Resource Surveys
(NARS), the statistical surveys summarized in this report
sample monitoring sites using a stratified, randomized
design to provide unbiased estimates of the condition
of the broader population of waters (e.g., rivers and
streams, lakes) throughout the nation. These nationally
consistent surveys, conducted on a five-year cycle,
report on the extent of waters that meet the CWA goals
of supporting healthy biological communities and
recreation. NARS also examines the prevalence of
priority physical and chemical stressors. Detailed results
and data from these surveys are available at National
Aquatic Resource Survey's Website. The surveys are
designed to:
Assess the biological/recreational condition of
the nation's waters at national and broad
regional scales.
Identify the most widespread stressors and
rank them based on the relative associations
between indicators of condition and
indicators of stress.
Track changes in water quality over time.
The statistical design of the national surveys allows
EPA to extrapolate the results from the approximately
1,000 sites sampled each cycle to the entire
population (estuarine waters, Great Lake nearshore
waters, lakes and reservoirs, rivers and streams, and
wetlands). This is a cost-effective means of generating
national or statewide assessments. Consistent
sampling methods ensure that results can be
aggregated into regional and national indicators of
the health of the resource. The survey results
quantify, with documented confidence, water quality
condition across the country and estimate the extent
of waters affected by key stressors. This helps set
priorities for water resource protection and
restoration. Nationally consistent surveys provide a
standardized measure for tracking changes in the
condition of the nation's waters over time and for
evaluating progress in investments to protect and
restore water quality at a broad scale.
The surveys use selected indicators to assess the
biological, chemical, and physical condition of waters in
the U.S., as well as characteristics that pose risks to
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human health1. Although they do not include all
indicators, EPA and its state and Tribal partners
determined that those selected align with the survey
goals and are representative at a national scale.
To assess water quality, NARS uses two types of
assessment benchmarks. The first type consisted of
fixed benchmarks applied nationally based on values in
the peer-reviewed scientific literature, EPA published
values, or EPA-derived screening levels. For example,
EPA's recommended water quality criteria were used
nationally to classify rivers and streams as above or
below a criterion or benchmark for microcystins,
cylindrospermopsin, enterococci, and mercury.
Similarly, EPA fish tissue screening levels for PCBs,
developed using information on human health risk and
fish consumption rates, were applied for human health
fish fillet tissue indicators. The second type consists of
NARS-specific regional benchmarks.
The NARS assessment benchmarks are not equivalent
to individual state water quality standards and have no
legal effect on state assessment decisions. NARS
condition categories may not correspond to the
categories states and Tribes use when they assess
water quality relative to their specific water quality
standards under the Clean Water Act. For example, a
rating of poor condition under NARS does not
necessarily mean a site is "impaired" as defined by state
and Tribal water quality standards and assessment
protocols.
Throughout this report, percentages reported for a
given indicator apply to the total extent of waters
assessed for the most recent surveys (see Table 1) with
exception of the human health fish fillet indicator, for
which percentages reported apply to the sampled
populations. For example, if wetland condition is
described as poor for 10% of wetlands nationally, this
means that the area estimated to be degraded for that
indicator is 9,564,924 wetland acres.
Table 1. Total Waters Assessed for each waterbody.
Total extent of waters assessed in the National Aquatic
Resource Surveys
Estuaries (square miles)
27,479
Great Lakes Nearshore (square miles)
7,118
Lakes and Reservoirs (number of lakes)
224,916
Perennial Rivers and Streams (miles)
1,543,290
Wetlands (acres)
95,694,241
This report provides information on the quality of the
nation's waters. It does not impose legally binding
requirements on EPA, states, Tribes, other regulatory
authorities, or the regulated community. This
document does not confer legal rights or impose legal
obligations upon any member of the public. This
document does not constitute a regulation, nor does it
change or substitute for any Clean Water Act (CWA)
provision or EPA regulation. EPA could update this
document as new information becomes available. EPA
and its employees do not endorse any products,
services, or enterprises. Mention of trade names or
commercial products in this document does not
constitute an endorsement or recommendation for
use.
1 Per the 2008 Federal Register notice, states and Tribes receive $8,000 per NARS site in their jurisdiction for field and laboratory work.
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Rivers and Streams
NRSA INDICATORS
NRSA used 13 indicators to assess the quality of
rivers and streams:
Biological
Macroinvertebrates
Fish
Chemical
Phosphorous
Nitrogen
Salinity
Physical
In-stream Fish Habitat
Riparian Disturbance
Riparian Vegetative Cover
Streambed sediments
Human Health
Enterococci
Microcystin and Cylindrospermopsin
Fish tissue contaminants
Quality for biological, chemical, and physical
indicators is based on NRSA-specific regional
benchmarks based on the distribution of indicator
values from a set of river and stream reference
sites. Human health indicator ratings are based on
fixed benchmarks based on values in the peer-
reviewed scientific literature or EPA published
values.
Key Findings of the National Rivers and Streams
Assessment 2018-2019
The National Rivers and Streams Assessment 2018-2019
(NRSA) was the third statistical survey of our nation's
flowing waters undertaken by the EPA and its state and
Tribal partners. It provides information on the ecological
condition of the nation's rivers and streams and the key
stressors that affect them, both on a national and an
eco-regional scale.
During the summers of 2018 and 2019, sixty-one EPA,
state and Tribal field crews sampled 1,851 randomly
selected river and stream sites across the country,
representing 1.5 million miles of rivers and streams.
Using standardized field methods, they sampled waters
as large as the Mississippi River and as small as
mountain headwater streams for indicators of water
quality, biological condition, habitat condition, and
recreational suitability. To learn more about the NRSA,
visit National Rivers and Streams Assessment Website.
Biological Indicators
Biological condition is the most comprehensive
indicator of water body health: when the biology of a
stream is healthy, the chemical and physical
components of the stream are also typically in good
condition. Of the nation's river and stream miles, less
than one-third of our river and stream miles (28%) had
healthy biological communities, based on an index that
uses the abundance and diversity of benthic macro-
invertebrates. Macro-invertebrates are bottom-dwelling
aquatic organisms such as dragonfly and stonefly larvae,
snails, worms, and beetles.
Good 28%
Fair 25%
Poor 47%
Good 35%
Poor 30%
NA 15% = 5%
Just over a third (35%) of river and stream
miles had healthy fish communities
Figure 2. Biological condition based on
macroinvertebrates and fish community.
Another index based on fish community scores found
35% of river and stream miles were rated good. Fish
are sensitive indicators of physical and chemical
habitat degradation, environmental contamination,
migration barriers and overall ecosystem
productivity. They need plants, insects and benthic
macroinvertebrates to eat; in- stream and
streambank cover for shelter; high-quality streambed
substrate conditions for spawning; and overhanging
vegetation to shade and cool the water. Fish can avoid
some stressors, unlike macroinvertebrates.
Chemical Indicators
Four chemical indicators were assessed as part of the
NRSA: nutrients (total phosphorus, total nitrogen),
salinity, and acidification. Of these, phosphorus and
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nitrogen are by far the most widespread: 42% percent
of the nation's river and stream miles are rated poor
because of excess levels of phosphorus and 44% are
rated poor because of excess levels of nitrogen. For
both phosphorus and nitrogen more river and stream
miles were in poor condition than in good condition.
The data collected indicate that a finding of poor
biological condition based on benthic
macroinvertebrates was almost twice as likely in rivers
and stream miles rated poor for nutrients, biological
condition could be improved if nutrient condition
changed from poor to fair or good. Most river and
stream miles were not acidic (98%) and in good
condition for salinity (85%).
Physical Habitat Indicators
Four indicators of physical habitat condition were
assessed nationally: in-stream fish habitat, excess
streambed sediments, riparian vegetative cover
(vegetation in the land corridor surrounding the river or
stream), and riparian disturbance (human activities
near the river or stream). Physical habitat indicator
scores revealed that 68% of river and stream miles
were rated good for in-stream fish habitat. In addition,
56% of river and stream miles had good ratings for
riparian vegetation, however, 64% had moderate or
high levels of riparian disturbance. NRSA found that
streambed sediments were in good condition in 57% of
river and stream miles. Human activities that disturb
land can interfere with river and stream sediment
balance by increasing the amount of fine sediment
entering river and stream channels. Benthic
macroinvertebrate condition was almost twice as likely
to be rated poor when sediment levels were rated poor
than when they were rated fair or good.
Human Health Indicators
The survey evaluated river and stream quality compared
to six indicators that provide insight into potential risks to
human health: two algal toxins (microcystins and
cylindrospermopsin), the fecal contamination indicator
enterococci, and contaminants in fish tissue (mercury,
PCBs, and per- and polyfluoroalkyl substances (PFAS)).
Enterococci are bacteria that indicate fecal contamination.
Enterococci exceeded EPA's benchmark in 20% of river and
stream miles. Swimming and recreating in water
contaminated with pathogens could make people ill.
~ Below Ĥ Above Ĥ Not Assessed
Figure 3. Enterococci bacteria are used as a human
health indicator for recreation.
Cyanobacteria can produce a variety of toxins; the rivers
and streams survey measured levels of microcystins and
cylindrospermopsin. Algal toxins were present, but at
very low levels, with minimal recreational human health
concerns. Microcystins and cylindrospermopsin were
detected in 9% and 10% of river and stream miles,
respectively, but did not exceed EPA's criteria
recommendation.
In an analysis of contaminants in rivers, mercury, PCBs
and PFOS were detected in over 90% of fish tissue
samples, with exceedances of screening levels varying
by contaminant. Mercury concentrations in fish fillet
composite samples (samples composed of fillet tissue
from multiple fish) were detected in 100% of samples
and concentrations exceeded EPA's recommended
fish tissue-based water quality criterion in 26% of the
41,099 river miles comprising the sampled population
for this indicator. Total PCB concentrations in fish
fillet composite samples were detected in 100% of
samples and concentrations exceeded fish tissue
screening levels for the general consumer in 45% of
the 41,099 river miles comprising the sampled
population for this indicator. People should check for
local health department advisories before eating fish
they have caught.
Regional, State, and Local Results
Regional Results for all indicators can be found at:
Rivers and Streams Dashboard
Rivers and Streams Ecoregional Results
State, Tribal, and local water quality information:
How's My Waterway
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Lakes, Ponds, and Reservoirs
NLA INDICATORS
NLA used 15 indicators to assess the quality of lakes.
These parameters are grouped into four categories:
trophic state, biological, chemical, and physical.
Trophic State
Biological
Chlorophyll a
Benthic macroinvertebrates
Zooplankton
Chemical
Acidification
Atrazine
Algal toxin (Microcystins)
Dissolved Oxygen
Phosphorous
Nitrogen
Physical
Lake drawdown exposure
Lake habitat complexity
Lakeshore disturbance
Riparian vegetation cover
Shallow water habitat
Quality for biological, chemical, and physical
indicators are based on NLA-specific regional
reference conditions. For the algal toxin and atrazine
indicators, analysts used nationally consistent
benchmarks developed by EPA or EPA recommended
water quality criteria.
Key Findings of the National Lakes Assessment
2017
The National Lakes Assessment (NLA) 2017 was the
third statistical survey of the condition of our nation's
lakes, ponds, and reservoirs undertaken by the EPA
and its state and Tribal partners. It provides
information on the ecological condition of the nation's
lakes and the key stressors that affect them, both on a
national and an eco-regional scale.
In the summer of 2017, field crews from EPA, states,
Tribes, and other partners sampled 1,005 randomly
selected lakes across the country. The survey results
represent the state of nearly 225,000 natural and
human- made lakes in the U.S. that are greater than 1
hectare in area and at least one meter deep. Lakes
were sampled for indicators of water quality,
biological condition, habitat condition, and
recreational suitability. For more information on the
NLA, visit the National Lakes Assessment Website.
Trophic Indicator
Trophic state is commonly used for classifying the
biological productivity in lakes. Twenty four percent of
lakes have the highest concentrations of chlorophyll a
and are classified as most disturbed, or hypereutrophic;
45% are eutrophic; 20% are mesotrophic; and 11% have
low levels of chlorophyll a and are classified as
oligotrophic.
Figure 4. Trophic status of lakes across the
country. Nationally eutrophication was
widespread, 24% of lakes were
hypereutrophic and 45% were eutrophic.
The clearest lakes in the oligotrophic and
meso-trophic category made up 11% and
20% of lakes, respectively. The percentage
of lakes in mesotrophic condition declined
from 27% to 20%; this was the only
statistically significant change in trophic
state nationally. In the Upper Midwest
ecoregion, statistically significant changes
in trophic condition included a decline in
lakes in mesotrophic condition (change
from 47% to 31%) and an increase in
hypereutrophic condition (change from
5% to 14%).
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Biological Indicators
Overall, EPA found that 43% of lakes were in good
condition based on benthic macroinvertebrates, 29%
of lakes were in fair condition, and 24% were poor. For
zooplankton (small animals in the water column), 22%
of lakes had poor zooplankton communities and 23% of
lakes had communities in fair condition. Chlorophyll a,
which indicates the amount of microscopic algae and
cyano-bacteria present, was in excess and rated poor
in 45% of lakes. The percentage of lakes in good
chlorophyll a condition decreased significantly, from
46% to 34% since 2012. Nationally, lakes where
phosphorus was elevated, benthic macroinvertebrate
communities (e.g., insect larvae, snails, and clams living
on the lake bottom) were 2.3 times more likely to be in
poor condition. In natural lakes (i.e., excluding
reservoirs), this risk increased to 6.9.
Biological Conditions of Lakes
Based on Macroinvertebrate
Communities
Good
43%
Fair
29%
Poor
24%
4%, Not Assessed
Biological Conditions of Lakes
Based on the Abundance of
Chlorophyll a
Good
34%
Fair
21%
Poor
45%
Chlorophyll a indicates the presence of
algae and cyanobacteria.
Figure 5. Biological condition can be characterized by
the presence, number, and diversity of
macroinvertebrates, algae, vascular plants, and other
organisms.
Chemical Indicators
High nutrient levels are the leading problem in the
nation's lakes. In many lakes, phosphorus is
considered the limiting nutrient; small amounts can
trigger rapid increases in algal growth. Across the
country 45% of lakes had poor levels of phosphorus,
and 46% had poor levels of nitrogen. Lakes with high
levels of phosphorus are more than twice as likely to
have poor conditions for benthic macroinvertebrates.
Atrazine is an agricultural herbicide. It can affect
plant growth and may be toxic to wildlife and
humans. It was detected in 30% of lakes and
measured at levels that exceed screening
benchmarks in 0.5% of lakes (about 1,200 lakes).
Nine percent of lakes have poor dissolved oxygen in
surface waters, insufficient to support aquatic life
(<3mg/L). Lakes with good ratings for dissolved
oxygen in surface waters decreased by 12 percentage
points compared to 2012.
Figure 6. The herbicide atrazine can affect plant
growth and may be toxic to wildlife.
Human Health Indicator
Algae and cyanobacteria
Microcystin
77%
21%
2%
M
Microcystin were detected in
21% of lakes. Levels exceeded
the EPA recreational criterion
in 2% of lakes
Figure 7. The percentage of
lakes where microcystins
were detected decreased,
down from 37% in 2012.
are a natural part of
freshwater ecosystems.
However, some algae
blooms, powered by high
levels of nutrients and
warm temperatures, can
be harmful to people and
animals. The NLA 2017
finds that an algal toxin,
microcystin, was detected
in 21% of lakes, but
concentrations exceeded
EPA's recommended
recreational freshwater
criteria in less than 2% of
lakes.
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Physical Habitat Indicators
For the NLA, physical habitat condition was assessed
based on observation of five indicators: lake
drawdown exposure, lake habitat complexity,
lakeshore disturbance, riparian vegetation cover,
and shallow water habitat. Healthy lakeshore
habitat slows pollution runoff and provides varied
and complex ecological niches for aquatic life. Only
25% of lakes were rated good for lakeshore
disturbance, indicating shoreline alterations were
present in 74% of lakes. Only 3% of lakes had poor
(large) drawdown. The drawdown indicator
measures water levels and their fluctuation. Shallow
water habitat, riparian vegetative cover, and habitat
complexity conditions were rated good in 51% to
65% of lakes. Lakes with good habitat complexity
increased 13 percentage points in 2017.
Regional, State, and Local Results
Regional Results for all indicators can be found at:
National Lakes Assessment Dashboard
National Lakes Assessment Ecoregional Results
State, Tribal, and local water quality information:
How's My Waterway
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Wetlands
Key Findings of the National Wetland
Condition Assessment 2016
The National Wetland Condition Assessment (NWCA)
2016 was the second statistical survey of the
condition of our nation's wetlands. It provides
information on the ecological condition of the
nation's wetlands and the key stressors that affect
them, both on a national and an eco- regional scale.
To learn more about the benefits of wetlands and EPA
activities to protect and restore these vital resources,
visit EPA's wetlands page.
During the spring and summer of 2016, field crews
from EPA, states, Tribes, and other partners sampled
967 randomly selected wetland sites across the
country. The survey represents 95,694,241 acres of
wetlands in the U.S. and encompasses all wetlands,
from the tidal and non-tidal wetlands along our coasts
to the forested swamps, prairie potholes and
meadows of the interior plains. Wetlands were
sampled for vegetation, soils, hydrology, algae, water
chemistry, and potential stressors.
For more information on the NWCA, see the National
Wetland Condition Assessment Website
Biological Indicators
In 2016, 47%, of wetland area was rated good based
on the vegetation multimetric index. Using another
biological indicator based on the occurrence and
abundance of nonnative plants, EPA found condition
to be good in 57% of wetland area. Nonnative plants
are recognized as indicators of declining ecological
Less than half of wetlands
had healthy vegetation.
condition. Vegetation is a major component of the
biodiversity and structure of wetlands, and it
provides habitat for microbes, insects, amphibians,
reptiles, birds, and mammals.
NWCA INDICATORS
The NWCA uses categories of indicators to assess the
conditions and stressors of wetlands.
Biological
Vegetation Index
Nonnative Plants
Chemical
Soil Heavy Metals
Water Chemistry (Phosphorous
and Nitrogen)
Physical
Vegetation Removal
Vegetation Replacement
Flow Obstruction
Water Addition or Subtraction
Soil Hardening
Surface Modifications
Physical Alterations
Human Health
Microcystins
Biological, chemical, and physical indicators are
evaluated based on reference conditions for
regional, national, or wetland group. For human
health indicators, EPA compared the numeric results
to EPA recommended water quality criteria.
0
Soils were in
good
condition
relative to
the heavy
metal
indicator in
45% of
wetland area
21% of
wetlands are
rated poor
or very poor
due to the
presence of
non-native
plant
species
Figure 8. Non-native species are the most common problem, while measured concentrations of heavy metals were below
background levels across most wetland area. The biological indicator for vegetation was a multi-metric index.
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Chemical Indicators
For wetlands, a soil heavy metals indicator assessed
concentrations of 12 different heavy metals which can
negatively impact ecological function and health.
Thresholds used reflect human disturbance to the site,
not necessarily toxicity. The assessment indicated that
95% of wetland area across the U.S was in good
condition relative to the heavy metals indicator.
Nitrogen and phosphorus conditions were found to be
poor (have excess levels) at 24% and 22% of wetland
area, respectively. However, because many wetlands
do not have surface water present during the NWCA
sampling period, 40% of wetland area was not
assessed for these two indicators. Wetlands that score
poorfor either of the chemical indicators are more
likely to score poor for the vegetation index, than are
wetlands that score fair or good for the chemical
indicators.
Physical indicators
The survey includes information on physical, human-
caused alterations to wetlands that affect vegetation,
hydrology (water levels and the flow of water), or soil.
The NWCA also measures the presence of multiple
alterations at each site using a cumulative indicator
that combines the results of the six indicators. In 2016,
the combined indicator showed that 36% of wetland
area was in poor condition. Physical alteration
indicators for soil hardening and water addition or
subtraction were the most widespread of the
individual physical indicator However, because many
wetlands do not have surface water present during the
NWCA sampling period, 42% of wetland area was not
assessed.
36%
Wetlands rated
poor due to
high levels of
physical
alterations
Figure 9. 36% of wetlands rated poor due to high levels of
physical alterations such as soil hardening, vegetation
replacement and water addition and subtraction,
Human Health Indicator
Microcystins were detected in 8% of wetland area.
Microcystins in wetland waters exceeded the EPA's
recommended recreational freshwater criterion in less
than 1% of wetland area.
Fifty-four percent and 50%, respectively, of wetland
area was in fair or poor condition for these indicators.
Most wetland area was rated good for surface
modification (79%), flow obstruction (74%), vegetation
replacement (69%), and vegetation removal (61%).
Regional, State, and Local Results
Regional Results for all indicators can be found at:
National Wetland Condition Assessment Dashboard
National Wetland Condition Assessment Ecoregional
Results
State, Tribal, and local water quality information:
How's My Waterway
ihm
v.
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Coastal Estuaries
Key Findings of the National Coastal Condition
Assessment 2015
The National Coastal Condition Assessment (NCCA)
2015 reports on the condition of our nation's coastal
estuarine waters and Great Lakes (included in the
following section). It provides information on the
ecological condition of these coastal waters and the
key stressors that affect them, both on a national and
regional basis.
In the summer of 2015, EPA and its partners visited a
total of 1,060 randomly selected sites in 28 coastal
states (excluding Alaska and Hawaii) with 699 sites in
estuaries representing about 27,479 square miles.
Coastal waters were sampled for indicators of water
quality, biological condition, prey fish contaminant
effect on wildlife predators, sediment quality, and
recreational suitability.
For more information on the NCCA, visit The National
Coastal Condition Assessment Website.
Ecological Indicators
Biological condition was overall good, with 71% of
estuarine area in good condition based on the benthic
macroinvertebrate index. From 2005-06 to 2015, the
percentage of area in good condition increased (from
51% to 71%), while "not assessed" area decreased by a
similar margin. Sediment quality in estuaries was
good, based on measures of chemical contaminants
found in sediments and laboratory tests of toxicity.
Seventy-six percent of estuarine area was rated good
nationally, although low levels of metals and polycyclic
aromatic hydrocarbons were widely detected.
Sediments serve as critical indicators of estuarine
condition because they can accumulate contaminants
that may enter the food web via bottom-dwelling
organisms.
High contaminant levels in prey fish could pose a risk
for the food web. Fifteen percent of estuarine area
was rated good, 20% was rated fair, and 55% was
rated poor (10% of the area was not assessed). This
indicator evaluates the extent of water where levels of
contamination in fish might lead to lethal or nonlethal
ecological effects such as reduced reproductive
success in predators. This indicator does not imply risk
to people.
NCCA INDICATORS
The NCCA uses four ecological and three human
health indicators to assess the conditions in estuaries
and bays.
Ecological Indicators
Biological Condition
Eutrophication
Sediment Quality
Ecological Effects of Fish
Tissue Contamination
Human Health Indicators
Enterococci
Microcystin
Mercury in Fish Fillet Plugs
Ecological indicators are evaluated based on NCCA-
specific index score. Eutrophication is based on a
water quality index. Sediment is based on a quality
condition score. For human health indicators, EPA
compared the numeric results to human health
benchmarks.
Figure 10. In estuaries, 71% are healthy based on their
biological communities. A healthy waterbody supports
aquatic communities - such as worms, snails, and clams -
that are sensitive to changes in their environment. 76% of
estuaries have good quality sediments. When present,
contaminants can negatively impact organisms living in
sediments.
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Ecological
Indicators
Biological Condition
Eutrophication Index
Sediment Quality
Ecological Effects of
Contaminated Fish
| Ĥ 71% (7% not assessed)
33% {<1% not assessed)
15% (10% not assessed)
76% (3% not assessed)
Human
Health
Indicators
Microcystes
Entero cocci
Mercury in Fish Fillets
(Plug Samples)
I
100% (0% not assessed)
0%
50%
- 99% (1% not assessed)
' 55% (43% not assessed)
100%
Figure 11. The percent of estuarine area in good condition for NCCA 2015 indicators.
Eutrophication is the most widespread problem in
estuaries. Only 33% of estuarine area was rated good.
Conditions were worst in the Gulf of Mexico region,
where 18% of area was rated good; and best on the
West Coast, where 76% of the area was rated good.
Components of the water quality index include
phosphorus, nitrogen, water clarity, chlorophyll a, and
dissolved oxygen. Low levels of dissolved oxygen and
high nutrient levels associated with eutrophication
can stress or even kiil fish and other aquatic
organisms.
Human Health Indicators
Conditions pose little risk to human health in most
estuaries. Human health indicators were assessed for
Figure 12. in almost all coastal waters, eutrophication
poses the greatest environmental threat. High levels of
nutrients can contribute to algal blooms which affect
recreation and wildlife.
the first time in 2015. In most estuaries, recreational
users faced a low risk of exposure to fecal indicator
bacteria (enterococci) and cyanotoxins (microcystins);
enterococci samples rarely exceeded benchmarks, and
microcystins did not at ail. Note that results for
microcystins do not mean there are never problems-
harmful algal blooms can be short-lived and may
develop and produce toxins quickly, and other toxins
not measured as part of the NCCA may be present.
The NCCA also assessed mercury in plug samples taken
from fish fillet tissue. Mercury was detected in all
estuarine fish fillet plug samples collected but was
above EPA's recommended fish tissue-based water
quality criterion in only 2% of the area. However, 43%
of estuarine area was not assessed due in part to
inability to catch fish of the correct species or size.
People should check for local health department
advisories before participating in aquatic recreation or
eating fish they have caught.
Regional, State, and Local Results
Regional Results for all indicators can be found at:
National Coastal Condition Assessment Dashboard
National Coastal Condition Assessment Ecoregional
Results
State, Tribal, and local water quality information:
How's My Waterway
National Water Quality Inventory
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Great Lakes Nearshore
NCCA INDICATORS for the Great Lakes
Key Findings for the Great Lakes Nearshore
Waters NCCA 2015
The National Coastal Conditions Assessment (NCCA)
2015 was the second statistical survey of the condition
of our nation's Great Lakes (and coastal embayment
waters included in the previous section). It provides
information on the ecological condition of the Great
Lakes nearshore waters and the key stressors that
affect them, both on a system and lake basis.
In the summer of 2015, EPA and its partners visited a
total of 361 randomly selected sites in the Great Lakes,
representing about 7,118 square miles of nearshore
waters. The Great Lake nearshore sites were sampled
for indicators of water quality, biological condition,
prey fish contaminant effect on wildlife predators,
sediment quality, and recreational suitability. For more
information on the NCCA, visit the National Coastal
Condition Assessment Website.
Ecological Indicators
In 2015, 31% of Great Lakes nearshore area was in
good biological condition; it should be noted a similar
proportion was not assessed for this indicator.
Sediments are critical indicators of condition because
they can accumulate contaminants and may enter the
food web via bottom-dwelling organisms. Almost two-
thirds of the nearshore area in the Great Lakes was in
good condition based on sediment quality. Overall,
62% of nearshore area was in good condition for
sediment quality, with 21% of area not assessed.
Difficulty in collecting samples for analysis of biological
condition and sediment quality was a problem in the
Great Lakes. Areas with hard lake bottoms or invasive
mussel colonies often prevented crews from collecting
a sample, limiting the ability to determine condition in
many areas.
High contaminant levels in prey fish in the Great Lakes
could pose a risk for the food-web. The levels of
contaminants in prey fish in 66% of the Great Lakes
nearshore area could lead to adverse ecological effects,
such as stunted growth or reduced reproduction, in
sensitive fish and wildlife that eat them. This indicator
assesses contaminants that at low levels may cause
effects in predators. It does not imply risk to people.
Four ecological and three human health indicators to
assess the conditions in the Great Lakes nearshore.
Ecological Indicators
Biological Condition
Eutrophication
Sediment Quality
Ecological Effects of Fish
Tissue Contamination
Human Health
Enterococci
Microcystin
Contaminants in Fish Fillet
Ecological indicators are evaluated based on NCCA-
specific index score. Eutrophication is based on a
water quality index. Sediment is based on a quality
condition score. For human health indicators, EPA
compared the numeric results to human health
benchmarks.
Eutrophication occurs when excess nutrients are
present in water. Eutrophication can trigger harmful
algal blooms. Sources of excess nutrients include
urban and agricultural runoff, leaking septic systems,
and discharge from wastewater treatment plants.
Figure 13. Twenty-four percent of Great Lakes waters have
excess nutrients. While nutrients are important, having too
many nutrients can lead to problems that reduce fishing,
recreational, and tourism opportunities.
Eutrophication is a persistent problem in the Great
Lakes with 46% of the nearshore area in fair or poor
condition; Lake Erie experienced the most
eutrophication, with 77% of the nearshore waters in
fair or poor condition. Reduced water clarity and
elevated total phosphorus were the drivers behind
poor condition.
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Good
Fair
Great Lakes
54%
Lake Superior
Lake Michigan
Lake Huron
Lake Erie |H~23%
Lake Ontario
62%
62% _
1 48%
61%
0%
50
100
0%
22%
30%
15%
- 36%
17%
- 24%
50
Poor
24%
4- 8%
23%
17%
15% '
Ĥ 60%
100 0%
50
Not Assessed
<1%
0%
<1%
0%
0%
0%
100 0%
50
More than 60% of the nearshore area in Lake
Michigan, Lake Ontario and Lake Superior was in
good condition.
Overall, Lake Erie had 60% of its nearshore
area in poor condition and only 17% and 23%
in fair and good condition, respectively.
100
Figure 14. Eutrophication occurs when excess nutrients are present in water. Eutrophication can trigger harmful algal blooms.
Sources of excess nutrients include urban and agricultural runoff, leaking septic systems, and discharge from wastewater treatment
plants.
Human Health Indicators
At the time of sampling in 2015, human health
indicators indicated low risk in most of the Great
Lakes. Enterococci concentrations in 2015 were below
the EPA's recommended benchmark in 99% of the
Great Lakes nearshore area.
In the Great Lakes, an analysis of mercury, PCBs and
PFOS indicated that all were present in all composite
fish fillet tissue samples, with exceedances varying by
contaminant. Mercury concentrations in fish fiilet
composite samples exceeded EPA's recommended
fish tissue-based water quality criterion in 13% of the
6,862 square miles comprising the sampled
population for this indicator. Total PCB concentrations
in fish fiilet composite samples exceeded the fish
tissue screening level for cancer effects for the
general consumer in 79% of the sampled population
for this indicator. People shouid check for local health
department advisories before eating fish they have
caught.
Microcystins were detected in 31% of nearshore area.
All microcystin samples but one (in Lake Erie) were at
concentrations below the EPA's recommended
recreational freshwater criterion.
Regional, State, and Local Results
Regional Results for all indicators can be found at:
National Coastal Condition Assessment Dashboard
National Coastal Condition Assessment Ecoregional
Results
State, Tribal, and local water quality information:
How's My Waterway
National Water Quality Inventory
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Comparisons Across the National
Aquatic Resource Surveys
Each of these assessments includes information on
biological, chemical, and physical indicators. While the
specific indicators chosen are those most suited to
each waterbody type and are not exactly the same,
looking across these assessments provides a broad
picture of the overall health of waters across the
country.
Biological Indicators
Benthic macroinvertebrates are widely used in the U.S.
and globally to assess biological condition. Each of the
national surveys for rivers and streams, lakes,
estuaries, and Great Lakes nearshore waters used
benthic macroinvertebrate indices appropriate to the
aquatic resource types. The wetlands survey used a
vegetation index to assess biological condition. Figure
15 compares information from the most recent
reports in the NARS program. Estuarine waters had the
most area in good condition at 71%, followed by
wetlands with 47%, and lakes with 43%.
Biological Condition Across Water Types
Rivers &
Streams
Lakes
Wetlands Estuaries Great Lakes
28%
43%
47%
31%
25%
29%
19%
71%
15%
21%
47%
24%
34%
15%
7%
7%
33%
Ĥ Good
Fair Ĥ Poor
Not Assessed
Figure 15. Biological condition for coastal waters, lakes, rivers,
and streams is based on benthic macroinvertebrates; for
wetlands based on plants. For the Great Lakes, it is important to
note the large percent of unassessed waters. Data Source: NARS
2015-2019.
Chemical Indicators
Nutrient Pollution
NARS reports all present information about nutrient
concentrations in the nation's waters, although the
benchmarks for good, fair, poor vary by resource type
and region of the country. The rivers and streams,
lakes, and wetlands surveys compare nutrient levels to
regional reference conditions. The NCCA reports on
nitrogen and phosphorus separately and includes
them as two of four parameters that comprise
regional eutrophication indices. All the surveys found
nutrients to be a widespread stressor, with less than
half scoring good for nitrogen or phosphorus. Results
for the eutrophication index find that 33% of estuarine
Phosphorous Across Water Types
Rivers &
Streams
Lakes
Wetlands Estuaries Great Lakes
36%
41%
25%
13%
33%
44%
23%
14%
22%
47%
29%
42%
45%
40%
17%
23%
Ĥ Good
Fair
Ĥ Poor Not Assessed
Figure 16. Phosphorus is an essential nutrient in the
environment, but excess phosphorus is widespread in rivers,
streams, and lakes. Data Source: NARS 2015-2019
waters and 54% of Great Lakes nearshore waters were
in good condition.
In appropriate quantities, phosphorus is necessary for
healthy, productive ecosystems. However, in excess
quantities, phosphorus can lead to water quality
problems such as eutrophication and harmful algal
growth. Some aquatic resources, such as wetlands,
naturally serve as sinks for phosphorus found in
sediments or dissolved in water. Since phosphorus
National Water Quality Inventory
21
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generally occurs in small quantities in the natural
environment, even small increases can negatively
affect water quality and biological condition. Figure 16
compares results for phosphorus across surveys.
Results for total phosphorus find that 44% of the Great
Lakes nearshore and 41% of lakes score good followed
by estuaries, wetlands and rivers and streams.
Physical Habitat Indicators
Sediment and Soil Quality
Soil and sediment quality is measured in the
wetlands, coastal, and Great Lakes surveys. The NCCA
found that the majority of estuarine and Great Lake
nearshore sediments were in good condition (76%
and 62%, respectively) based on measures of
chemical contaminants found in sediments and
laboratory tests of toxicity. Additionally, the wetlands
assessment found concentrations of heavy metals
were below background levels across most wetland
area. The assessment indicated that 95% of wetland
area across the U.S was in good condition, 3% was in
fair, and 2% was in poor.
Vegetation and Disturbance
The disturbance indicators reflect the extent and
intensity of direct human alteration of the lakeshore,
riparian area, or wetland itself. These disturbances
Human Disturbance
Rivers &
Streams Wetlands Lakes
36%
18%
25%
44%
45%
42%
22%
36%
29%
I Good Fair
Poor Not
Figure 17. Indicators of Human Disturbance. The disturbance
indicator reflects the extent and intensity of direct human
alteration. Examples of human disturbance in the riparian area
include roads, pavement and cleared lots, buildings, pipes,
parks or maintained lawns, trash, pastures and rangeland, row
crops, dams, and logging or mining operations. This indicator
was not assessed for the NCCA. Data Source: NARS 2016-2019.
National Water Quality Inventory
22
can range from minor changes, such as the removal of
a few trees to develop a picnic area, to major
alterations, such as the construction of a large
residential complex or mining operations. The effects
of development on water quality include excess
erosion and sedimentation, flow alteration, increased
temperature, loss of native plants, alteration or loss
of vegetation structure and complexity, and
modifications to sediment types. These impacts can
negatively affect fish, wildlife, and other aquatic
communities. They can diminish recreational
opportunities and pose public health risks where
there is increased potential for flooding or formation
of harmful algal blooms. Figure 17 compares results
for extent and intensity of human disturbance across
the surveys. For lakes, 25% were rated good (had low
levels of human disturbance), 45% were in fair
condition, and 29% were in poor condition. Results
were similar for rivers and streams with, 36%, 42%,
and 22% rated good, fair, and poor, respectively. For
wetlands, 18% of wetland area were rated good, 44%
were in fair, and 36% were in poor condition.
Healthy, multilayered vegetation in the riparian
corridor can provide a buffer from the effects of
human disturbance in several ways: by slowing
runoff; filtering nutrients and sediments; reducing
streambank erosion; providing shade, which keeps
water cool and reduces algae growth; and supplying
leaf litter, branches, and logs that serve as food,
shelter, and habitat for fish and other aquatic
organisms. Analysts assessed riparian vegetative
cover by summing the amount of cover provided by
three layers of vegetation: the ground layer, woody
shrubs, and canopy trees. Just over half of lakes
(51%) had high (good) levels of riparian vegetation
cover; 26% had low (poor) cover. For rivers and
streams, 56% of river and stream miles were rated
good, 17% were rated fair, and 24% were rated poor
for riparian vegetative cover.
Human activities can also interfere with river and
stream sediment balance by increasing the amount
of fine sediment entering river and stream channels,
filling in the spaces between cobbles and rocks
which is an important benthic habitat. NRSA
scientists analyzed the extent to which excess fine
sediments occurred in rivers and streams, focusing
on conditions indicating lower-than- expected
streambed stability and higher excess
sedimentation. In 2018-19 streambed sediments
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were in good condition in 57% of river and stream
miles, fair condition in 23%, and in poor condition in
20%.
Human Health Indicators
Human health indicators generally indicated more
coastal waters were in good condition than other
types of water- bodies. Enterococci data from the
NCCA showed that 99% of both estuary and Great
Lakes nearshore area were below the EPA criterion
for recreational exposure. For river and stream miles
78% were below the criterion in the 2018-19 survey, a
13-point improvement from 2013-14.
Microcystin Detected
Rivers &
Streams
Lakes
Wetlands Estuaries Great Lakes
63%
77%
50%
8%
37%
0.10%
19%
2%
2%
42%
0.10%
94%
69%
6%
0.0%
31%
0.05%
Ĥ Non-Detect Detected Ĥ Above Benchmark Ĥ Not Assessed
Figure 18. Microcystin Detections Across Water Body Types.
Microcystins (algal toxins) results were compared to the EPA's
recreational water quality criterion and swimming advisory
recommendation of 8 ppb (U.S. EPA 2019). Data Source: NARS
2015-2019.
All the NARS reports assessed waters for
microcystins, one class of cyanotoxins. Health effects
of exposure include skin rashes, gastroenteritis and in
severe cases, liver or kidney failure and death.
Microcystins were detected below benchmark levels
in 6% of estuarine area, 8% of wetland area, 21% of
lakes, 31% of nearshore Great Lakes waters, and 9%
of river and stream miles. When values are compared
to EPA' recreational freshwater criterion of 8 ppb,
exceedances of the microcystins criterion were rare
across all waters. Lakes had the highest exceedance
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rate with about two percent, or 4,400 lakes exceeding
the microcystins criterion.
Two of the NARS reports assessed fish tissue
contaminants for human health using both fish fillet
plugs and composite fish fillet tissue. Mercury was
detected at low levels in all fish fillet plug samples,
exceeding EPA's recommended fish tissue-based
water quality criterion in 2% of estuarine area, 6% of
the Great Lakes nearshore area, and 7% of river and
stream miles. However, a lot of waters were
unassessed because fish were not present or too
small to collect plug samples (65% of river and
stream miles, 43% of estuarine area, and 29% of
Great Lakes nearshore area). In addition to mercury,
the composite fish fillet tissue analysis included
PCBs and PFOS. There was no statistically significant
decrease in the extent of rivers with PCBs in fish
tissue above the EPA screening level for cancer
effects between these two river surveys nor was
there a statistically significant change in the extent
of rivers with mercury in fish tissue above the EPA
recommended criterion for methylmercury.
There was a statistically significant decrease in the
Great Lakes nearshore area with PCBs in fish tissue
above the EPA screening level between the 2010 and
2015 Great Lakes surveys. There were no statistically
significant changes in the extent of Great Lakes
nearshore area with mercury in fish tissue above the
EPA criterion.
Key Stressors Associated with Poor Biological
Integrity
Restoring water quality requires not only an
understanding of current condition and change over
time, but also of stressors associated with degraded
biological condition and the extent to which
reducing those stressors can improve conditions.
This knowledge can help decision makers prioritize
stressors for reduction.
To address these questions at the national and
regional level, EPA performed three calculations for
each stressor.
1. First, EPA determined the extent of
waterbodies in poor condition for each
stressor. This is the relative extent.
2. Then, EPA evaluated the extent to which
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poor biological condition was more likely
when a stressor or indicator was rated
poor. This is the relative risk.
3. Lastly, EPA combined the relative extent and
relative risk values for each indicator into a
single value that provides an estimate of the
potential improvement that could be achieved
by reducing or eliminating the stressor. This is
the attributable risk.
For benthic macroinvertebrates in rivers and streams,
salinity was the stressor with the highest relative risk
estimate nationally (1.8). That is, rivers and streams
with salinity in poor condition were 1.8 times more
likely to rate poor for benthic macroinvertebrates
than waters that weren't poor for salinity. Phosphorus
and nitrogen showed relative risks of 1.7 and 1.5,
respectively, indicating rivers and streams rated poor
for nutrients were more likely to rate poor for
biological condition.
Combining the relative extent and relative risk values
for each indicator into a single value provides us with
attributable risk. Attributable risk analysis for rivers
and streams shows that reducing nutrients could result
in the greatest benefit to biological condition at the
national scale. If poor condition were improved to fair
or good for nutrients, the percentage of river and
stream miles with poor benthic macroinvertebrate
condition could be reduced by approximately 20%.
For lakes, total phosphorus was the stressor with the
highest relative risk estimate nationally (2.3). That is,
lakes with poor ratings for phosphorus were about 2.3
times more likely to have poor benthic
macroinvertebrate condition. Atrazine detection,
dissolved oxygen, total nitrogen, and shallow water
habitat had relative risks of 2.0 or greater. Calculating
attributable risk, EPA found that reducing phosphorus
and nitrogen could result in the greatest benefit to
benthic macroinvertebrate condition nationally. If
poor phosphorus condition were improved to fair or
good, a 36% reduction in poor benthic
macroinvertebrate condition could occur. For
nitrogen, the improvement in poor benthic
macroinvertebrate condition could be 32%.
For wetlands, the indicators for heavy metals in
soils, phosphorus, vegetation removal and
vegetation replacement had relative risks of 2.0.
That is, wetlands rated poor for these stressors or
indicators were twice as likely to have poor
vegetation condition. Calculating attributable risk at
the national scale EPA found that reducing total
phosphorus in wetland waters could result in the
greatest benefit to biological condition. If wetland
areas rated poor for phosphorus were improved to
fair or good condition, a 27% reduction in poor
vegetation condition could occur. Reductions in
nitrogen could reduce poor vegetation condition by
23%.
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State 305(b) Assessment and
Reporting
States, territories, and Tribes have primary
responsibility to implement the CWA to protect waters
in their state. This includes setting water quality
standards, monitoring and assessing water quality,
permitting point source discharges, and developing
plans and taking action to safeguard and restore water
resources.
Targeted, site-specific monitoring and assessments
provide information states need to support
management decisions at watershed and local scales
(e.g., whether a specific water meets its water quality
standards, what the sources contributing to
degradation are, etc.) for the individual waters that
are monitored. Site-specific water quality assessment
helps the state set local priorities and implement
actions for restoring degraded waters. States also
incorporate statistical survey designs into their
monitoring programs as a complement to their site-
specific monitoring. While site-specific monitoring
focuses on waters that are priorities either for
protection or restoration, state surveys provide
broader context of the condition of all state waters.
The methods states use to monitor and assess their
waters - including what they monitor, how they
monitor, and how they interpret and report their
findings - vary from state to state and within individual
states over time. Thus, the assessment decisions
reported by states and Tribes and summarized in
How's My Waterway while valuable for each state and
Tribe individually, cannot be used to compare water
quality conditions among states and Tribes or be
combined to report national water quality conditions
and trends or compare the impacts of specific causes
or sources of impairment over time.
Under the CWA, each state or Tribe sets its own water
quality standards, including designated uses, narrative
and numeric water quality criteria, and
antidegradation policies. After assembling monitoring
data from all available sources, states compare
monitoring results to their water quality standards and
make assessment decisions on the status of their
waters. Good waterbodies are those that fully support
the water quality standards and designated uses
assessed.
Regional Highlight: Vermont's Lakes
The nationally consistent, statistically representative
NARS provide unique data sets to look for patterns
across the country. One pattern that emerged, was the
loss of high-quality waters, specifically waters with the
lowest levels of nutrients, across the US. These
findings, published in Stoddard et al 2016, prompted
scientists working at Vermont Department of
Environmental Quality to take a new look at the state
and volunteer monitoring long-term data sets. When
they looked at their long-term phosphorus trends,
sorting by the rate of the change since 1980, they saw
a strong pattern of increasing phosphorus in the
highest quality oligotrophic and mesotrophic lakes.
The data, presented in Figure 18, also showed
encouraging trends for decreasing phosphorus in some
many eutrophic lakes, an indication that investments in
nutrient controls at lower quality lakes were paying off.
40-Year Spring Total Phosphorus Trends on Vermont Lakes
Oligotrophic
Mesotrophic
Eutrophic
Figure 19. Trends in total phosphorous (TP) and trophic state
of lakes in Vermont.
The state also examined the data they collected for
statewide lakes assessment survey in partnership with
the NARS National Lakes Assessment in 2007 and 2012
The results presented in Figure 19 show a statistically
significant loss of lakes in the highest quality 'good'
category of lakes with low levels of phosphorus. This
was accompanied by increases in the fair and poor
categories.
The data demonstrating that lakes experiencing the
greatest increases in nutrients are the higher quality,
clear water oligotrophic and mesotrophic lakes is
informing analysis of options to protect these lakes
across the state. One challenge for lake managers is
that the nutrient concentrations in many of the lakes
are well within the state water quality standards,
which means conditions could continue to deteriorate
before triggering corrective action.
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Threatened waterbodies support the standards but
may exhibit a deteriorating trend. Impaired
waterbodies are unable to support one or more of the
water quality standards.
The following are broad categories of Designated Uses
that states and Tribes may include in their water
quality standards. These are used to summarize state
305(b) reports and Tribal assessment reports in How's
My Waterway.
Swimming: EPA, states, and Tribes monitor
and assess water quality to keep you safe
while swimming, wading, or boating.
Eating Fish: EPA, states, and Tribes monitor
and assess water quality to determine if fish
and shellfish are safe to eat.
Aquatic Life: EPA, states, and Tribes
monitor and assess water quality to
determine the impact of impairments on
plants and animals living in the water.
Drinking Water: EPA, states, and Tribes
assess drinking water quality and compare to
state and national drinking water metrics.
As states submit water quality assessment decisions in
their Integrated 303(d)/305(b) Reports, the
information is loaded into the How's My Waterway
database which presents state-scale survey results
with site-specific assessments for a more complete
story on water quality. Use the links provided on the
map in Figure 19 to see the most recent water quality
assessment results submitted by states under Clean
Water Act Section 305(b).
!İl
#
H
Regional Highlight: Vermont's Lakes (Continued)
Figure 20. Change in Vermont Lakes' Total Phosphorous
(TP) Conditions from 2007 to 2012 based on Statewide
NARS Data and Northern Appalachian Region Thresholds.
These analyses compelled a number of lake
associations on the oligotrophic lakes with declining
water quality to petition the state to upward
reclassify them to A1 waters. If reclassified, these
lakes would be held to the most stringent nutrient
standards in Vermont's nutrient criteria, public
policy makers in Vermont to pursue revisions to
water quality standards that will increasing
protections for these waterbodies and ensure
ensuring their ability to provide for healthy aquatic
communities and support recreational activities for
future generations.
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Figure 19. Links to state 305(b) water quality inventory results.
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References
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Washington, DC: World Bank, https://doi.org/10.1596/978-1-4648-1459-4
Keiser, D. A., Kling, C. L., & Shapiro, J. S. (2019). The low but uncertain measured benefits of US water quality policy.
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Keiser, D. A., & Shapiro, J. S. (2019). US water pollution regulation over the past half century: burning waters to
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Methylmercury. EPA 823-R-01-001. https://www.epa.gov/sites/default/files/2020-
01/documents/methylmercury-criterion-2001.pdf
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Nation's Estuarine and Nearshore Great Lakes Waters. EPA 841-R-21-001. https://www.epa.gov/national-
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U.S. Environmental Protection Agency. (2021b) Increasing Attention to Community Water System Compliance. EPA
310-F-21-002. https://www.epa.gov/sites/default/files/2021-04/documents/complianceadvisorv-
communitvwatersvstemncigeneral.pdf
U.S. Environmental Protection Agency. 2021c. National coastal condition assessment 2015 technical support
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U.S. Environmental Protection Agency. (2022). National Lakes Assessment: The Third Collaborative Survey of Lakes in
the United States. EPA 841-R-22-002. EPA, Office of Water & Office of Research and Development.
https://nationallakesassessment.epa.gov/webreport
U.S. Environmental Protection Agency. (2023a). National Rivers and Streams Assessment 2018-2019: A Collaborative
Survey. EPA 841-R-23-002. https://www.epa.gov/national- aquatic-resource-survevs/nrsa
U.S. Environmental Protection Agency. (2023b). National Wetland Condition Assessment 2016: The Second
Collaborative Survey of Wetlands in the United States. EPA 841-R-23-003. https://www.epa.gov/national-
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U.S. Environmental Protection Agency. (2024). Final Human Health Toxicity Assessment for Perfluorooctane Sulfonic
Acid (PFOS) and Related Salts. EPA 815-R-24-007. https://www.epa.gov/svstem/files/documents/2024-
04/main final-toxicity-assessment-for-pfos 2024-04-09-refs-formatted 508c.pdf
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