Iowa DNR
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Water Quality Assessments

Impaired Waters List

Designated Uses

Segments of streams and rivers in Iowa each have specific designations, based on what they are used for – like recreation, such as swimming or fishing; drinking water; or maintaining a healthy population of fish and other aquatic life. The series of rules that specify what uses should be protected is commonly called the DNR’s water quality standards.

The “presumed” use rule associated with the UAA (Use Assessment and Attainability Analysis) process assumes the Class A1 and Class B(WW-1) use designations, described below, were applicable for every stream or river, unless assessments demonstrated otherwise. The following is a brief description of these and other use designations noted in the standards.

Recreational Uses

Waterbody segments designated for recreational use are protected for uses that involve human contact with the water. Three types of recreational uses are:

Class A1 - Primary contact recreational use: The water’s recreation uses involve full body immersion with prolonged and direct contact with the water, such as swimming and water skiing.

Class A2 - Secondary contact recreational use: Water recreation uses involve incidental or accidental contact with the water, where the probability of ingesting water is minimal, such as fishing and shoreline activities.

Class A3 - Children’s recreational use: Water recreation uses where children’s activities are common, like wading or playing in the water. These waters are commonly located in urban or residential areas where the banks are defined and there is visible evidence of flow.

Aquatic Life Uses

Warm water waterbodies can also be designated to protect aquatic life, such as fish, plants and insects that live in and around the water. Streams that maintain flow throughout the year, or contain sufficient pooled areas during intermittent flow periods to maintain a viable aquatic community, can be designated for aquatic life uses for warm water species. The three warm water uses include:

Class B(WW-1) - Typically large interior and border rivers and the lower segments of medium-size tributary streams capable of supporting and maintaining a wide variety of aquatic life, including game fish.

Class B(WW-2) - Typically smaller, perennially flowing streams capable of supporting and maintaining a resident aquatic community, but lack the flow and habitat necessary to fully support and sustain game fish populations.

Class B(WW-3) - Intermittent stream with non-flowing perennial pools capable of supporting and maintaining a resident aquatic community in harsher conditions. These waters lack the flow and habitat necessary to fully support and sustain a game fish population.

Class B(LW) -These are artificial and natural impoundments with hydraulic retention times and other physical and chemical characteristics suitable to maintain a balanced community normally associated with lake-like conditions .

Iowa also has a small group of cold water waterbodies, many of which are located in the northeast portions of the state. These can also be designated to protect aquatic life, such as fish, plants and insects that live in and around these streams. Waters in which the temperature and flow are suitable can be designated for aquatic life uses for cold water species. The two cold water uses include:

Class B(CW-1) – Waters in which the temperature and flow are suitable for the maintenance Of a variety of cold water species, including reproducing and non-reproducing populations of trout (Salmonidae family) and associated aquatic communities.

Class B(CW-2) – Waters that include small, channeled streams, headwaters, and spring runs that possess natural cold water attributes of temperature and flow. These waters usually do not support consistent populations of trout (Salmonidae family), but may support associated vertebrate and invertebrate organisms.

Drinking Water Uses

Waterbodies that provide or historically have been sources of drinking water are designated as Class C waters. According to EPA guidance, once a waterbody has been a designated Class C source of drinking water, it cannot lose the designation, even if it is no longer used as a source of drinking water.

Class C - Waters which are raw water sources of a potable water supply.

Other Uses

Class HH - Waters in which fish are routinely harvested for human consumption.

OIW - Outstanding Iowa Waters -A surface water that IADNR has classified as an outstanding state resource water in the water quality standards.

This page was created 1/8/2016 1:22:22 PM and was last updated 9/10/2019 12:51:34 PM