About this indicator
Every two years states are required to submit Water Quality Assessment Reports under Sections 305(b) and 303(d) of the Clean Water Act describing the condition of waters in the state. These reports include water quality information on rivers, lakes, estuaries, and coastal waters, and an analysis of the extent to which waters are meeting water quality standards. Waters are assessed as impaired when an applicable water quality standard is not being attained. Impaired waters require a total maximum daily load (TMDL) or alternative restoration plan to reduce pollutant loadings and restore the waterbody. This indicator displays information about the extent of documented nutrient-related impairments of state surface waters (not including Great Lakes, coastal waters, or wetlands). This reflects states’ efforts to implement numeric and/or narrative criteria for nutrients by assessing waters for nutrient pollution and then listing waters as impaired to begin the restoration process. ‘Nutrient-related’ impairments include those from the following parent categories in EPA’s Assessment, TMDL Tracking And ImplementatioN System (ATTAINS) database: nutrients, algal growth, ammonia, noxious aquatic plants, and organic enrichment/oxygen depletion. Data provided in this indicator are for rivers/streams, lakes/reservoirs and bays/estuaries, and help demonstrate:

• The extent to which a state is assessing its waters for nutrient-related parameters,
• The extent of nitrogen and phosphorus pollution in the state, and
• The extent to which the state is working towards restoring nutrient-impaired waters by developing TMDLs or alternative restoration plans.

To obtain more information on which waters have been listed by a state as impaired by nutrients and which of those waters have an associated TMDL, users can visit EPA’s Nitrogen and Phosphorus Pollution Data Access Tool.

• Rivers Assessed as Impaired due to Nutrient-Related Causes
• Lakes Assessed as Impaired due to Nutrient-Related Causes
• Bays/Estuaries Assessed as Impaired due to Nutrient-Related Causes

State river water quality assessment results as reflected in states' most recent Integrated Water Quality Assessment Report or 305(b) Water Quality Assessment Report, and progress towards restoring nutrient-impaired rivers.

Note - "Nutrient-related" impairment includes waters impaired for nutrients, algal growth, ammonia, noxious aquatic plants, and organic enrichment/oxygen depletion. Impaired waters include those from Integrated Reporting Categories 4 (mostly with a TMDL) and 5 (need a TMDL). Values are rounded to the nearest whole number. Therefore, values < 0.5% = 0% and values > 99.5% = 100%. Data pertaining to % of assessed waters that have a nutrient-related impairment are likely an underestimate given that states may not necessarily assess each water for nutrients, specifically.

± These states have not provided the necessary information in their data submission to distinguish between Category 4 and Category 5 impaired waters, therefore these data were not reported.

* In some cases the state erroneously reported a greater # of waters assessed than the total # of waters in the state, resulting in > 100% assessed, as indicated by the 100%*.

Source: State's most recent electronic Integrated Report or 305(b) Report data submitted to the EPA’s Assessment, TMDL Tracking And ImplementatioN System (ATTAINS) website. Date of data pull: 11/4/11

Download the Impaired Rivers data table (excel)(2 pp, 17 K)

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State lake and reservoir water quality assessment results as reflected in states' most Integrated Water Quality Assessment Report or 305(b) Water Quality Assessment Report, and progress towards restoring nutrient-impaired lakes and reservoirs.

Note - "Nutrient-related" impairment includes waters impaired for nutrients, algal growth, ammonia, noxious aquatic plants, and organic enrichment/oxygen depletion. Impaired waters include those from Integrated Reporting Categories 4 (mostly with a TMDL) and 5 (need a TMDL). Values are rounded to the nearest whole number. Therefore, values < 0.5% = 0% and values > 99.5% = 100%. Data pertaining to % of assessed waters with a nutrient-related impairment are likely an underestimate given that states may not necessarily assess each water for nutrients, specifically.

± These states have not provided the necessary information in their data submission to distinguish between Category 4 and Category 5 impaired waters, therefore these data were not reported.

* In some cases the state erroneously reported a greater # of waters assessed than the total # of waters in the state, resulting in > 100% assessed, as indicated by the 100%*.

Source: State's most recent electronic Integrated Report or 305(b) Report data submitted to the EPA’s Assessment, TMDL Tracking And ImplementatioN System (ATTAINS) website. Date of data pull: 11/4/11

Download the Impaired Lakes data table (excel)(2 pp, 17 K)

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State bay/estuary water quality assessment results as reflected in states' most recent Integrated Water Quality Assessment Report or 305(b) Water Quality Assessment Report, and progress towards restoring nutrient-impaired bays/estuaries.

Note - "Nutrient-related" impairment includes waters impaired for nutrients, algal growth, ammonia, noxious aquatic plants, and organic enrichment/oxygen depletion. Impaired waters include those from Integrated Reporting Categories 4 (mostly with a TMDL) and 5 (need a TMDL). Values are rounded to the nearest whole number. Therefore, values < 0.5% = 0% and values > 99.5% = 100%. Data pertaining to % of assessed waters with a nutrient-related impairment are likely an underestimate given that states may not necessarily assess each water for nutrients, specifically.

± These states have not provided the necessary information in their data submission to distinguish between Category 4 and Category 5 impaired waters, therefore these data were not reported.

* In some cases the state erroneously reported a greater # of waters assessed than the total # of waters in the state, resulting in > 100% assessed, as indicated by the 100%*.

Source: State's most recent electronic Integrated Report or 305(b) Report data submitted to the EPA’s Assessment, TMDL Tracking And ImplementatioN System (ATTAINS) website. Date of data pull: 11/4/11

Download the Impaired Estuaries data table (excel)(2 pp, 15 K)

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Source of data

1. U.S. EPA. 2011. Water Quality Assessment and Total Maximum Daily Loads Information: Assessment, TMDL Tracking And ImplementatioN System (ATTAINS).

Data source information
This indicator includes data submitted by states to EPA under sections 305(b) and 303(d) of the Clean Water Act, and which were obtained from EPA’s Assessment, TMDL Tracking and ImplementatioN System (ATTAINS) website. The source of the information available in the ATTAINS database are electronic data submitted by states, which can be data from an Integrated Water Quality Assessment Report (recommended by EPA) or from a 305(b) Water Quality Assessment Report.

In Integrated Water Quality Assessment Reports, each assessed waterbody or waterbody segment is listed in one of the five following categories (collectively these are the 305b data):

• Category 1 – Attaining all designated uses
• Category 2 – Attaining some designated uses, and insufficient or no data information to determine if remaining uses are attained
• Category 3 – Insufficient or no data and information to determine if any use is attained
• Category 4- Impaired or threatened for one or more uses but not needing a TMDL because –

  a) TMDL has been completed
  b) Expected to meet standards
  c) Not impaired by a pollutant

• Category 5 – Impaired or threatened by pollutant(s) for one or more designated uses and requiring a TMDL. These are the waters entered onto a states’ 303(d) list.

In 305(b) Water Quality Assessment Reports, assessed waters are categorized according to the degree to which they support their designated uses:

• Good water quality – fully supporting or fully supporting but threatened
• Fair water quality – partially supporting (impaired)
• Poor water quality – not supporting (impaired)

Data in this indicator on waters assessed as impaired due to nutrient-related causes include all Category 4 and 5 waters from Integrated Reports, and fair/partially supporting or poor/not supporting waters from 305(b) Reports.

What to consider when using these data

• In ATTAINS, the most recent reporting cycle year varies by state and can be as far back as 2002. Data for each state are current as of the year listed in the column “Reporting Cycle (year)” within the data tables. Note that the data are static and not automatically linked to ATTAINS updates.
• The total size (length or area) of waters assessed as impaired was filtered to exclude double counting (i.e., waters listed as impaired for multiple nutrient-related causes were only counted once in this dataset).
• The % of nutrient-impaired waters that have all impairments addressed by a TMDL or alternative restoration plan could not be calculated for states that do not submit 1) an Integrated Report and/or 2) TMDL IDs with their 305(b) data. For states that submit separate 305(b) and 303(d) Reports, TMDL data and 303(d) data (impaired waters needing a TMDL) are not true subsets of the 305(b) data on assessments of waters, and so often do not correlate with the 305(b) data, making comparisons not possible. As a result, it is not known whether impaired waters from these states’ 305(b) Reports have an associated TMDL (Category 4a in the Integrated Report) or need a TMDL (Category 5 in the Integrated Report). For states that haven’t submitted TMDL IDs with their 305(b) data, it is not known if an impaired water with a specific nutrient-related cause is in Category 4a (TMDL completed) for that cause. In both of these cases, all impaired waters from a state’s 305(b) data will evaluate to a Category 5 by the ATTAINS data system. In this indicator, the % of nutrient-impaired waters that have all impairments addressed by a TMDL or alternative restoration plan is not entered for states that don’t submit an Integrated Report or supporting data such as TMDL IDs correlating to their 305(b) data (and is indicated by ‘±’ in the data tables). However, users can browse states’ websites and/or contact such states for any relevant information they may be able to provide.
• Data in this indicator do not include impairment or assessment information for coastal waters or for the Great Lakes, since both are listed in miles instead of square miles.
• The inclusion of waters listed for organic enrichment/oxygen depletion may provide a slight overestimate of nutrient impaired waters. Low dissolved oxygen levels are typically an indirect effect of nitrogen and phosphorus pollution; however, in some cases, the cause of low dissolved oxygen concentrations may be due to factors other than nutrient enrichment.
• Some states may not fully monitor/assess waters for nutrient-related parameters, resulting in an underestimation of the actual extent of assessed waters impaired by nitrogen and phosphorus pollution in these states. Documentation of nutrient-impaired waters indicates that a state has developed numeric or narrative criteria for nutrient-related pollution, or implements a general narrative criterion.

References and links to other data sources

1. Dubrovsky, N.M., Burow, K.R., Clark, G.M., Gronberg, J.M., Hamilton P.A., Hitt, K.J., Mueller, D.K., Munn, M.D., Nolan, B.T., Puckett, L.J., Rupert, M.G., Short, T.M., Spahr, N.E., Sprague, L.A., and Wilber, W.G. 2010. The quality of our Nation’s waters—Nutrients in the Nation’s streams and groundwater, 1992–2004: U.S. Geological Survey Circular 1350.

2. Shipp, A. and Cordy, G.E. 2002. The USGS role in TMDL assessments: U.S. Geological Survey Fact Sheet 130-01.

3.U.S. EPA. Overview of impaired waters and total maximum daily loads program.

4. U.S. EPA. Ask Waters data query tool.

5. U.S. EPA. WATERS Geospatial Data Downloads site.

6. U.S. EPA. Reach Address Database (RAD) Download tool.

7. U.S. Geological Survey. National Water Quality Assessment Program (NAWQA): State assessments of beneficial uses and impaired waters.

8. U.S. EPA. Monitoring, Assessment and Reporting Guidelines.

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