Surface water quality: designated uses
Designated uses, sometimes called “beneficial uses,” describe uses specified in our water quality standards for each water body or water body segment. Water quality criteria — designed to protect the designated uses — are used to assess the general health of Washington surface waters and set permit limits.
Designated uses for waters of the state
We protect the state's waters for four groups of designated uses:
|Aquatic life uses
|Water supply uses
Marine and fresh waters have designated uses assigned in a “use-based” format, where individual water bodies are assigned individual uses.
Designated uses for marine waters
Marine water designated uses and criteria for the protection of marine surface waters of the state are described in WAC 173-201A-210. The designated uses assigned to specific marine water bodies are described in WAC 173-201A-610 and 173-201A-612.
Designated uses for fresh waters
Finding designated uses and criteria for rivers and streams is slightly more complex because most designations rely on specific salmon species and spawning cycles which occur in the stream.
To find the designated use(s) for rivers and streams, refer to WAC 173-201A-600 and 602 of the water quality standards.
Table 602 lists specific water bodies, organized by Water Resource Inventory Area (WRIA) and the uses assigned to those waters. Many waters are not specifically named. Those water bodies not specially named have their uses assigned through general designation rules WAC 173-201A-600.
For each named water body, Table 602 lists the designated aquatic life uses with the most stringent criteria.
- Example: char spawning/rearing has a more stringent and protective temperature criteria than salmonid spawning/rearing. If both uses are designated — or could exist in the water body — the more protective char spawning/rearing designated use and criteria will apply.
Table 602 footnotes
The footnotes in Table 602 are special conditions for some water bodies. The special conditions are criteria for some parameters that apply only to the waters specified — these criteria footnotes override the criteria in Table 602.
- Note: If a listing has a footnote the special conditions only apply to those waters with that footnote number. If there is a special condition at the bottom of a WRIA and there is no footnote reference, that special condition applies to all waters in the WRIA.
Supplemental spawning and incubation
After identifying the uses and criteria for a specific water body, the Supplemental Spawning and Incubation Protection for Salmonid Species maps are used to check for possible additional temperature criteria, which may be necessary during some parts of the year.
If the supplemental spawning temperature criteria are colder than other applicable criteria, the supplemental spawning criteria apply. The Supplemental Spawning and Incubation maps also provide additional spawning and incubation temperature criteria for salmon, trout, and char spawning time-frames.