What is the 303(d) List of Impaired Waters?

Section 303(d) of the Clean Water Act (CWA) requires that states assess surface waters and compile a list of those that have become polluted to the point that they no longer support their Use Classification (e.g., Fish & Wildlife, Public Water Supply, Swimming & Whole-Body Contact, etc.). This list of impaired waters is known as the 303(d) List.

Every two years, the Alabama Department of Environmental Management (ADEM) releases a list of Alabama’s impaired waterbodies that they find out of the rivers, streams, lakes, and coastlines they assess. A waterbody is considered “impaired” when it does not meet the water quality standard designated for its use classification.

What are water quality standards?

A standard is something we can compare water quality data to in order to know if the quality of that water is good or bad. If water quality data results consistently fail to meet the standards, there may be a chronic problem with water quality.

Some water quality standards are usually based on what conditions are needed for aquatic life to survive. These water quality standards are designed to protect, restore, and maintain water quality.

What is the 303(d) List?

The 303(d) list provides information about a waterbody’s location and size, use classification, and sources and causes of impairments. Below is a small sample from the list, and a breakdown of the information in each column.

To view the Final 2020 303(d) List, go to: http://www.adem.state.al.us/programs/water/wquality/2020AL303dList.pdf

What are use classifications?

Water use classifications are the “reasonable and necessary uses” of a waterbody as defined by the Clean Water Act. Waterbodies can be classified as the following:

  1. Outstanding Alabama Water (OAW)
  2. Public Water Supply
  3. Swimming & Other Whole Body Water-Contact Sports (S)
  4. Shellfish Harvesting
  5. Fish & Wildlife (F&W)
  6. Limited Warmwater Fishery
  7. Agricultural & Industrial Water Supply (A&I)

ADEM has use classification maps (like the map of the Alabama River basin below) available on their website for each major river basin in Alabama.

Waterbodies can have several use classifications. For example, a waterbody can be classified as Fish & Wildlife and Swimming.

In 2020, 443 waterbodies were listed on the Alabama 303(d) list of impaired waters. Out of these, 9 were listed as Outstanding Alabama Waters, 169 for Swimming, 52 for Public Water Supply, 416 for Fish & Wildlife, 12 for Shellfish Harvesting, 3 for Limited Warmwater Fishery, and 4 for Agricultural and Industrial uses.

The Outstanding Alabama Waters are located in the Cahaba River Basin, Coosa River Basin, Mobile River Basin, and Tallapoosa River Basin.

Below is a comparison of the impaired waters listed by each river basin.

What impairments can waterbodies be listed for?

There are many potential causes of impairment in a waterbody. The 2020 list includes the following impairments:

Habitat alterations
Metals (Arsenic, Cyanide, Iron, Lead, Mercury,
and/or Thallium)
Organic enrichment (BOD)
Pesticides (Dieldrin)
PFOS (Perfluorooctanesulfonic acid)
Priority organics (PCBs –
Polychlorinated Biphenyls)

Total Dissolved Solids

There are also many potential sources of impairments. The 2020 list includes the following sources:

Animal feeding operations
Atmospheric deposition
Collection system failure
Contaminated sediments
Crop production (non-irrigated)
Land development
Nonpoint source runoff
On-site wastewater systems
Pasture grazing
Silviculture activities
Sources outside state
Streambank modification
Surface mining
Surface mining – abandoned
Unknown source
Urban runoff
Urban runoff/storm sewers
Wet weather discharge

You can view 303(d) listed streams and waterbodies on Alabama Water Watch’s maps: and selecting to view “ADEM 303 Impaired (2018)” from the map menu.