Delaware Basin High Quality Designated Uses Viewer



After Congress passed the Clean Water Act, states were required to designate uses for each waterbody. The designated uses for each state may be general, such as recreation and aquatic life, or they can be more specific, such as swimming and cold water fishery.

Designated uses are human uses and ecological conditions that states recognize officially in their water quality standards. States must designate one or more uses for each water body.

A water body’s designated uses must fully represent existing and potential uses. Not every existing use of a water must be individually designated, but the designated uses must be broad enough and require strong enough protections for all existing uses.

A state’s designated uses must include recreation and aquatic life. (40CFR131.10(a)) States may also designate other human uses such as fish consumption, shellfish harvesting and drinking water supply.

How does this play out in the Delaware basin?

New York, Pennsylvania, New Jersey and the Delaware River Basin Commission all have designated uses for the waters in the Delaware River Basin.

River Network has compiled selected DESIGNATED USE CLASSES for the Delaware River Basin states of NY, NJ, PA and DE into this interactive map. This tool is intended to help groups working in the Basin on restoration and protection projects by providing information that can help prioritize locations and identify important characteristics for monitoring and tracking progress.

Existing and designated uses

 The Clean Water Act makes an important distinction between “existing” and “designated” uses.

Existing uses are 1) those that have occurred at any time since 1975, when the CWA regulations regarding use designation were established, regardless of whether they have been designated (40CFR131.3(e)), and 2) uses for which the necessary quality has been attained, whether or not the use is being made (EPA WQS Handbook, 4.4). For example, if a river’s water quality is good enough for swimming, it is an existing use even if people don’t engage in it.

Designated uses are those uses that have been officially recognized by the state in water quality standards, whether or not they are being attained (40CFR131.3(f)).

Not every existing use needs to be listed as a designated use, but all existing uses must be protected by the designated uses. For example, if people swim and boat in a water body, designating that waterbody for swimming may be sufficient to protect the water quality for both existing uses. If water bodies are being used for purposes that require better water quality than the current designated uses require then “the state shall revise its standards to reflect the uses actually being attained” (40CFR131.10(i)).

Aquatic life uses

The EPA gives special emphasis to protecting aquatic life in its Water Quality Standards Handbook (August 1994) and tis publication “Questions and Answers on Antidegradation,” December 1983.

“Water quality should be such that it results in no mortality and no significant growth or reproductive impairment of resident species… Any lowering of water quality below this full level of protection is not allowed …The fact that sport or commercial fish are not present does not mean that the water may not be supporting an aquatic life protection function. An existing aquatic community composed entirely of invertebrates and plants, such as may be found in a pristine alpine tributary stream, should still be protected whether or not such a stream supports a fishery. ”