Assessment of Waters of the State Program


  • Every two years water quality data from the DEQ’s monitoring networks and any other readily available data is compiled into an integrated report (IR) which describes the current condition of the State’s waters.
  • The IR is a comprehensive assessment of the State’s water quality, which includes the requirements of sections 305(b) and 303(d) (list of impaired waters) of the Clean Water Act.

A waterbody is considered impaired and placed on the 303(d) list if it does not attain water quality criteria and/or support designated uses. Water quality criteria and designated uses are contained in APC&EC Rule 2. The Office of Water assesses the attainment of criteria and support of designated uses by applying its' comprehensive Assessment Methodology to water quality and biological data.

Water quality data from stream and lake sampling sites are considered during the development of the 303(d) list. Evaluated water quality data are collected by multiple entities, including: DEQ ; other state, federal, and local government agencies; and private entities. Data collected and analyzed under a QAPP that meets or exceeds DEQ’s or the United States Geological Survey’s quality assurance/quality control protocols are considered.

Waterbodies are classified into the following categories:

  • Category 1
    Attains all water quality standards for all designated uses; categorized by existence of a Total Maximum Daily Load (TMDL) or not for one or more constituents:
    • 1a. Attaining all water quality criteria and supporting all designated uses, no use is threatened. No TMDL exists for any constituents.
    • 1b. Attaining all water quality standards for all designated uses; however, a TMDL remains in place for one or more constituents.
  • Category 2
    Available data and/or information indicate that some, but not all of the designated uses are supported.
  • Category 3
    Insufficient data and/or information are available to make a use support determination:
    • 3a. No data available.
    • 3b. Insufficient data available.
      • Data do not meet all quality requirements outlined in this assessment methodology;
      • Waters in which the data are questionable because of Quality Assurance and/or Quality Control (QA/QC) procedures and/or the Assessment Unit (AU) requires confirmation of impairment before a TMDL is scheduled.
      • Where limited available data and/or information indicate potential impacts or downward trends in water quality, the following water bodies in Category 3 may be prioritized (on a case-by-case basis) for additional investigation: waters designated as ERW, ESW, or NSW; domestic water supplies; and waters located in known karst areas.
  • Category 4
    Water quality standards are not attained for one or more designated uses but the development of a TMDL is not required because:
    • 4a. A TMDL has been completed for the listed parameter(s); or
    • 4b. Other management alternatives are expected to result in the attainment of the water quality standard; or
    • 4c. Non-support of the water quality standard is not caused by a pollutant.
  • Category 5
    The waterbody is impaired, or one or more water quality standards may not be attained. Waterbodies in Category 5 will be prioritized as:
    • High
      • Truly impaired; develop a TMDL or other corrective action(s) for the listed parameter(s).
    • Medium
      • Waters currently not attaining standards, but may be de-listed with future revisions to APC&EC Rule 2, the state water quality standards; or
      • Waters which are impaired by point source discharges and future permit restrictions are expected to correct the problem(s).
    • Low
      • Waters currently not attaining one or more water quality standards, but all designated uses are determined to be supported; or
      • There is insufficient data to make a scientifically defensible decision concerning designated use support. Where more data and/or information are needed to verify the need for TMDL development or other corrective action(s) for the listed parameter(s), the following waterbodies in Category 5 may be prioritized (on a case-by-case basis) for additional investigation: waters designated as ERW, ESW, or NSW; domestic water supplies; and waters located in known karst areas; or
      • Waters DEQ assessed as unimpaired, but were assessed as impaired by EPA.
    • Alt
      • Waters where alternative restoration approaches may be more immediately beneficial or practicable in achieving water quality standards than pursuing the TMDL approach in the near-term.

Draft 303d List - Online Maps

2018 Impaired Waterbodies – 303(d) List

2016 Impaired Waterbodies – 303(d) List

About the 2016 Maps

To assist with the review process, DEQ has created maps by county depicting the waters included on the Draft 2016 303(d) list. The maps were creating using a subset of the streams from the USGS National Hydrography Dataset (NHD) Medium Resolution (1:100,000) Flowline.

  • Waters included on the Draft 2016 303(d) list in Category 5 are represented by purple lines and polygons.
  • Waters included on the Draft 2016 303(d) list in Category 4a are represented by black dashed lines and orange polygons.
  • Waters included on the Draft 2016 303(d) list in Category 1b are represented by yellow lines and polygons.

Draft 2014 Impaired Waterbodies – 303(d) List

About the 2014 Maps

To assist with the review process, DEQ has created maps depicting the waters included on the Draft 2014 303(d) list by county. The maps were created using a subset of the streams from the USGS National Hydrography Dataset (NHD) Medium Resolution (1:100,000) Flowline electronic mapping layer.

  • Streams included on the Draft 2014 303(d) list in Category 5 are represented by purple lines and lakes included on the Draft 2014 303(d) list in Category 5 are represented as light purple polygons.
  • Streams included in Draft 2014 Category 4a are represented by dashed black lines and lakes included in Draft 2014 Category 4a are represented by tan polygons.
  • There are occasions in which a waterbody may be included on the Draft 2014 list in both Category 5 and Category 4a; therefore, these waters will have a dashed or hashed overlay with a purple underlay.

Draft 2012 Impaired Waterbodies – 303(d) List

About the 2012 Maps

To assist with the review process, DEQ has created maps by county depicting the waters included on the Draft 2012 303(d) list. The maps were creating using a subset of the streams from the USGS National Hydrography Dataset (NHD) Medium Resolution (1:100,000) Flowline.

  • Waters included on the Draft 2012 303(d) list in Category 5 are represented by purple lines and shapes.
  • Waters included on the Draft 2012 303(d) list in Category 4a are represented by yellow lines and polygons.
  • The yellow lines representing the 2012 Draft Category 4a streams have been offset in order to be able to view the instances when a stream segment is listed in both Category 5 and Category 4a.

You can access a map in jpeg format by clicking the county name below. A complete list of all county maps in PDF format is also available.

2000 Impaired Waterbodies – 303(d) List