Waters Assessed as Impaired due to Nutrient-Related Causes

Photos of assessed and impaired waters

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.

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.

State Rivers assessed (miles) % of river miles assessed Rivers with a nutrient-related impairment (miles) % of assessed rivers that have a nutrient-related impairment % of nutrient-impaired rivers that have all impairments addressed by a TMDL or alternative restoration plan Reporting Cycle (year)
Alabama 10,538 14% 1,146 11% 53% 2010
Alaska 602 0% 15 2% 100% 2010
Arizona 2,764 3% 144 5% 6% 2008
Arkansas 9,979 11% 1,440 14% 2% 2008
California 32,803 16% 13,350 41% ± 2004
Colorado 59,639 56% 281 0% 14% 2010
Connecticut 2,367 41% 2 0% 73% 2010
Delaware 2,506 100% 2208 88% 37% 2006
Florida 10,476 20% 5,587 53% ± 2010
Georgia 13,393 19% 1272 9% 78% 2010
Hawaii 9 0% 5 59% ± 2006
Idaho 60,291 52% 7,160 12% 61% 2008
Illinois 15,424 18% 4430 29% 1% 2006
Indiana 24,070 67% 2,188 9% 0% 2010
Iowa 20,075 28% 304 2% 27% 2010
Kansas 27,408 20% 15,095 55% ± 2008
Kentucky 10,774 22% 1,878 17% 0% 2010
Louisiana 9,484 14% 4,469 47% 27% 2010
Maine 61,795 100% 486 1% 9% 2010
Maryland 6,331 72% 0 0% ± 2002
Massachusetts 2,745 28% 749 27% 2% 2010
Michigan 76,439 100% 2,003 3% 26% 2010
Minnesota 14,558 16% 1,978 14% 2% 2010
Mississippi 3,853 5% 200 5% 80% 2010
Missouri 16,516 32% 1,446 9% ± 2010
Montana 20,242 11% 7,692 38% 3% 2010
Nebraska 8,672 11% 34 0% ± 2010
Nevada 4490 29% 1,007 22% 2% 2006
New Hampshire 16,896 100% 789 5% 7% 2010
New Jersey 18,974 96% 7,864 41% 9% 2010
New Mexico 6,262 6% 1,125 18% 15% 2010
New York 27,280 52% 1,857 7% ± 2010
North Carolina 12,080 32% 242 2% ± 2010
North Dakota 54,606 100% 518 1% 6% 2010
Ohio 52,483 90% 30,427 58% ± 2010
Oklahoma 12,473 16% 2,366 19% 0% 2010
Oregon 46,038 40% 18,959 41% ± 2006
Pennsylvania 86,034 100%* 3,722 4% 0% 2006
Rhode Island 917 65% 53 6% 0% 2010
South Carolina 5,378 18% 559 10% 8% 2010
South Dakota 6,207 7% 408 7% 0% 2010
Tennessee 30,629 50% 3,631 12% 4% 2010
Texas 23,546 12% 2,048 9% 0% 2010
Utah 10,569 12% 968 9% 58% 2010
Vermont 5,555 78% 19 0% 32% 2008
Virginia 17,728 35% 1,941 11% 2% 2010
Washington 1,997 3% 396 20% 0% 2008
West Virginia 18,818 58% 163 1% 3% 2010
Wisconsin 15,132 18% 2,593 17% 45% 2006
Wyoming 7,504 7% 56 1% 0% 2010

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 impairedrivers.xlsx(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.

State Lakes/reservoirs assessed (acres) % of lakes/reservoirs assessed in the state Lakes/reservoirs with a nutrient-related impairment (acres) % of assessed lakes/reservoirs that have a nutrient-related impairment % of nutrient-impaired lakes/reservoirs that have all impairments addressed by a TMDL or alternative restoration plan Reporting Cycle (year)
Alabama 430.976 88% 81,740 19% 53% 2010
Alaska 5,981 0% 1,137 19% 73% 2010
Arizona 114,976 34% 4,895 4% 9% 2008
Arkansas 64,778 13% 6,513 10% 71% 2008
California 1,051,246 50% 473,954 45% ± 2004
Colorado 155,399 95% 10,211 7% 0% 2010
Connecticut 30,438 47% 3,719 12% 7% 2010
Delaware 2,954 100% 2,594 88% 69% 2006
Florida 1,124,399 54% 919,000 82% ± 2010
Georgia 349,375 82% 6,932 2% 20% 2010
Hawaii No data No data No data No data No data 2006
Idaho 223,244 48% 150,119 67% 9% 2008
Illinois 146,732 47% 131,114 89% 3% 2006
Indiana 231,083 162% 23,408 10% ± 2010
Iowa 178,265 88% 28,736 16% 34% 2010
Kansas 255,902 100% 207,460 81% ±  
Kentucky 219,418 96% 9,485 4% 0% 2010
Louisiana 668,847 62% 89,605 13% 22% 2010
Maine 1,984,170 100%* 36,533 2% 76% 2010
Maryland 18,676 24% 0 0% ± 2002
Massachusetts 85,056 56% 19,826 23% 22% 2010
Michigan 872,179 98% 6,048 1% 3% 2010
Minnesota 3,758,412 84% 480,679 14% 1% 2010
Mississippi 36,807 7% 0 0% 0% 2008
Missouri 290,442 99% 167,979 58% ± 2020
Montana 533,651 63% 180,267 34% 2% 2010
Nebraska 138,672 50% 105,220 76% ± 2010
Nevada 299,148 54% 54,765 18% ± 2006
New Hampshire 185,273 100% 47,215 25% 0% 2010
New Jersey 47,846 66% 16,640 35% 17% 2010
New Mexico 62,978 6% 10,007 16% 0% 2010
New York 535,659 68% 151,206 28% ± 2010
North Carolina 176,466 57% 71,951 41% ± 2010
North Dakota 700,259 98% 140,550 20% 3% 2010
Ohio 21,134 100%* 0 0% ± 2010
Oklahoma 604,594 58% 424,172 70% ± 2010
Oregon 138,358 22% 126,335 91% ± 2006
Pennsylvania No data No data No data No data No data 2006
Rhode Island 15,582 75% 2,385 15% 54% 2010
South Carolina 127,397 31% 23,638 19% 0% 2010
South Dakota 135,577 18% 11,322 8% 0% 2010
Tennessee 565,543 99% 38,066 7% ± 2010
Texas 1,461,997 73% 25,998 2% 0% 2010
Utah 468,877 97% 150,431 32% 18% 2010
Vermont 229,722 100% 139,927 61% 8% 2008
Virginia 112,677 75% 47,165 42% 0% 2010
Washington 464,530 100%* 37,031 8% 0% 2008
West Virginia 13,199 59% 96 1% 100 2010
Wisconsin 678,111 36% 260,011 38% 90% 2006
Wyoming 18,924 6% 15 0% 0% 2010

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 impairedlakes.xlsx(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.

State Bays/estuaries assessed (mi2) % of bays/estuaries assessed in the state Bays/estuaries with a nutrient-related impairment (mi2) % of assessed bays/estuaries that have a nutrient-related impairment % of nutrient-impaired bays/estuaries that have all impairments addressed by a TMDL or alternative restoration plan Reporting Cycle (year)
Alabama 734 100%* 0 0% 0% 2010
Alaska 31 0% 1 2% 100% 2010
California 904 42% 30 3% ± 2004
Connecticut 612 100% 305 50% 59% 2010
Delaware 30 7% 29 98% 10% 2006
Florida 5,317 100%* 1,795 32% ± 2010
Georgia 63 7% 14 22% 100% 2010
Hawaii 36 65% 30 83% ± 2006
Louisiana 4,954 65% 858 17% 22% 2010
Maine 156 5% 1 0% ± 2010
Maryland 2,499 99% 0 0% ± 2002
Massachusetts 247 99% 53 21% 21% 2010
Mississippi No data No data No data No data No data 2010
New Hampshire 99 100% 14 14% 0% 2010
New Jersey 740 97% 158 21% 9% 2010
New York 1,222 80% 152 12% ± 2010
North Carolina 2,932 94% 133 5% ± 2010
Oregon No data No data No data No data No data 2006
Rhode Island 159 100% 49 31% 0% 2010
South Carolina 588 100%* 14 2% 23% 2010
Texas 6,011 100%* 614 10% 0% 2010
Virginia 2,301 92% 2,096 91% 0% 2010
Washington No data No data No data No data No data 2008

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 impairedestuaries.xlsx(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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