Background

This fact sheet summarizes the findings of the National

Water Quality Inventory: 2000 Report, prepared under

Section 305(b) of the Clean Water Act. Section 305(b)

requires that states, territories, and jurisdictions assess

their water quality biennially and report those findings

to the U.S. Environmental Protection Agency (EPA).

EPA then summarizes the findings in a national water

quality inventory. It is important to note that this

report is no longer a Report to Congress, pursuant to

Public Law 104-66, the Federal Reports Elimination

and Sunset Act of 1995. 

To assess water quality, states and other jurisdictions

compare their monitoring results to the water quality

standards they have set for their waters. Water quality

standards consist of three elements: the designated

uses assigned to waters (such as drinking, swimming,

or fishing), criteria to protect those uses (such as

chemical-specific thresholds that should not be

exceeded), and an antidegradation policy intended to

In 2000, states, tribes, territories, and interstate commissions report that about 40% of streams, 

45% of lakes, and 50% of estuaries that were assessed were not clean enough to support uses such as

fishing and swimming (Figure 1). About 33% of U.S. waters were assessed for this national inventory

of water quality. Leading causes of impairment in assessed waters include bacteria, nutrients, metals

(primarily mercury), and siltation (Figure 2). Runoff from agricultural lands, municipal point sources

(sewage treatment plants), and hydrologic modifications (such as channelization, flow regulation, and

dredging) are the primary sources of impairment. Although the United States has made significant

progress in cleaning up polluted waters over the past 30 years, much remains to be done to restore

and protect the nation’s waters.

keep waters that do meet standards from deteriorating

from their current condition.

Findings

In their 2000 reports, states, tribes, territories, and

other jurisdictions assessed approximately 700,000

miles of rivers and 17.34 million acres of lakes, slightly

less area than in their 1998 reports. This decrease is

largely due to the states’ growing reluctance to use

older qualitative data when making water quality

assessments. More often, states are choosing to use

only high quality monitoring data for the purpose of

these assessments. States assessed about 31,000

square miles of estuaries, slightly more than in the last

reporting cycle. Figures 1 and 2 summarize the quality

of assessed river miles, lake acres, and estuary square

miles.

In 2000, mercury was described as a leading cause of

impairment in the nation’s estuaries and lakes. Increasingly, states are moving toward more comprehensive

Water Quality Conditions in the United States

A Profile from the 2000 National Water Quality Inventory

Amount Good but

Total Assessed* Good Threatened Polluted

Waterbody Type Size (% of Total) (% of Assessed) (% of Assessed) (% of Assessed)

Rivers 3,692,830 699,946 367,129 59,504 269,258 

(miles) (19%) (53%) (8%) (39%)

Lakes 40,603,893 17,339,080 8,026,988 1,348,903 7,702,370

(acres) (43%) (47%) (8%) (45%)

Estuaries 87,369 31,072 13,850 1,023 15,676

(sq. miles) (36%) (45%) (<4%) (51%)

*Includes waterbodies assessed as not attainable for one or more uses.

Note: percentages may not add up to 100% due to rounding.

Figure 1. Summary of Quality of Assessed Rivers, Lakes, and Estuaries
examination of fish tissue and are issuing statewide

advisories that restrict the consumption of some fish,

especially for vulnerable segments of the population.

Mercury, which originates from air transport from

power-generating facilities and incinerators, mining,

natural rock weathering, and other sources, was cited

in 2,242 of the 2,838 fishing advisories reported by the

states in 2000.

In addition, the states, tribes, territories, and jurisdictions assessed the quality of ocean and Great Lakes

shoreline miles, wetlands, and ground water.

■ Of the assessed ocean shoreline miles, 14% are

impaired, primarily because of bacteria, oxygen

depletion, and turbidity. Primary sources of pollution

include urban runoff, storm sewers, nonpoint source

runoff, and land disposal of wastes. States assessed

only 6% of the nation’s ocean shoreline miles.

■ States also found that 78% of assessed Great Lakes

shoreline miles are impaired, primarily due to pollutants in fish tissue at levels that exceed standards to

protect human health. States assessed 92% of Great

Lakes shoreline miles.

■ The average annual loss of wetlands has decreased

over the past 40 years to a current estimated loss of

58,500 acres per year. Nine states and tribes listed

sources of recent wetland loss. Leading reasons for

loss are filling and draining, conversion for agricultural uses, residential development, and road construction.

■ Overall, the states found that ground water quality 

is good and can support many different uses.

However, measurable negative impacts have been

detected in some areas and are commonly traced

back to sources such as leaking underground

storage tanks, septic systems, and landfills.

Future Reporting

In an effort to improve the consistency and comprehensiveness of water quality reporting and to streamline the reporting process, EPA is providing states,

territories, and tribes with guidance that recommends

they submit a 2002 Integrated Water Quality Monitoring and Assessment Report to satisfy the requirements

for both Sections 305(b) and 303(d) of the Clean

Water Act (Section 303(d) requires states to identify

impaired waters and develop allocations of the maximum amount of a pollutant each impaired water can

receive and still meet water quality standards). The

guidance is available at http://www.epa.gov/owow/

tmdl/2002wqma.html. EPA anticipates that the development of an Integrated Report will benefit the public

by providing a clearer summary of the water quality

status of the nation's waters and the management

actions necessary to protect and restore them. The

Integrated Report will also enhance the ability of water

quality managers to display, access, and integrate

environmental data and information from all components of the water quality program. 

Rivers and Streams Lakes, Ponds, and Reservoirs Estuaries

Pathogens (Bacteria) Nutrients Metals (Primarily mercury)

Siltation (Sedimentation) Metals (Primarily mercury) Pesticides

Habitat Alterations Siltation (Sedimentation) Oxygen-Depleting Substances

Agriculture Agriculture Municipal Point Sources

Hydrologic Modifications Hydrologic Modifications Urban Runoff/Storm Sewers

Habitat Modifications Urban Runoff/Storm Sewers Industrial Discharges

Figure 2. Leading Causes and Sources* of Impairment in Assessed Rivers, Lakes, and Estuaries

For Further Information

For a copy of the National Water Quality Inventory: 

2000 Report (EPA-841-R-02-001), visit www.epa.gov/305b

or call the EPA’s National Service Center for Environmental Publications at 1-800-490-9198.

Causes Sources

*Excluding unknown, natural, and “other” sources.

United States Environmental Protection Agency

Office of Water (4503F)

EPA-841-F-02-003 • August 2002