Part II–Designated Uses and Criteria


Fresh water designated uses and criteria

The following uses are designated for protection in fresh surface waters of the state. Use designations for water bodies are listed in WAC 173-201A-600 and 173-201A-602.

(1) Aquatic life uses. Aquatic life uses are designated based on the presence of, or the intent to provide protection for, the key uses identified below in (a). It is required that all indigenous fish and nonfish aquatic species be protected in waters of the state in addition to the key species described below.

(a) The categories for aquatic life uses are:

  1. Char spawning and rearing. The key identifying characteristics of this use are spawning or early juvenile rearing by native char (bull trout and Dolly Varden), or use by other aquatic species similarly dependent on such cold water. Other common characteristic aquatic life uses for waters in this category include summer foraging and migration of native char; and spawning, rearing, and migration by other salmonid species.
  2. Core summer salmonid habitat. The key identifying characteristics of this use are summer (June 15 – September 15) salmonid spawning or emergence, or adult holding; use as important summer rearing habitat by one or more salmonids; or foraging by adult and sub-adult native char. Other common characteristic aquatic life uses for waters in this category include spawning outside of the summer season, rearing, and migration by salmonids.
  3. Salmonid spawning, rearing, and migration. The key identifying characteristic of this use is salmon or trout spawning and emergence that only occurs outside of the summer season (September 16 - June 14). Other common characteristic aquatic life uses for waters in this category include rearing and migration by salmonids.
  4. Salmonid rearing and migration only. The key identifying characteristic of this use is use only for rearing or migration by salmonids (not used for spawning).
  5. Non-anadromous interior redband trout. For the protection of waters where the only trout species is a non-anadromous form of self-reproducing interior redband trout (O. mykis), and other associated aquatic life.
  6. Indigenous warm water species. Protection for waters where the dominant species under natural conditions would be temperature tolerant indigenous nonsalmonid species.

Examples include dace, redside shiner, chiselmouth, sucker, and northern pikeminnow.

(b) General criteria. General criteria that apply to all aquatic life fresh water uses are described in WAC 173-201A-260 (2)(a) and (b), and are for:

  1. Toxic, radioactive, and deleterious materials. (ii) Aesthetic values.

(c) Aquatic life temperature criteria. Except where noted, water temperature is measured by the 7-day average of the daily maximum temperatures (7-DADMax). Table 200 (1)(c) lists the temperature criteria for each of the aquatic life use categories.

Table 200 (1)(c) Aquatic Life Temperature Criteria in Fresh Water

Category Highest 7-DADMax
Char Spawning 9°C (48.2°F)
Char Spawning and Rearing 12°C (53.6°F)
Salmon and Trout Spawning 13°C (55.4°F)
Core Summer Salmonid Habitat 16°C (60.8°F)
Salmonid Spawning, Rearing, and Migration 17.5°C (63.5°F)
Salmonid Rearing and Migration Only 17.5°C (63.5°F)
Non-anadromous Interior Redband Trout 18°C (64.4°F)
Indigenous Warm Water Species 20°C (68°F)


  1. When a water body's temperature is warmer than the criteria in Table 200 (1)(c) (or within 0.3°C (0.54°F) of the criteria) and that condition is due to natural conditions, then human actions considered cumulatively may not cause the 7-DADMax temperature of that water body to increase more than 0.3°C (0.54°F).
  2. When the background condition of the water is cooler than the criteria in Table 200 (1)(c), the allowable rate of warming up to, but not exceeding, the numeric criteria from human actions is restricted as follows:
    1. Incremental temperature increases resulting from individual point source activities must not, at any time, exceed 28/(T+7) as measured at the edge of a mixing zone boundary (where "T" represents the background temperature as measured at a point or points unaffected by the discharge and representative of the highest ambient water temperature in the vicinity of the discharge).
    2. Incremental temperature increases resulting from the combined effect of all nonpoint source activities in the water body must not, at any time, exceed 2.8°C (5.04°F).
  3. Temperatures are not to exceed the criteria at a probability frequency of more than once every ten years on average.
  4. Spawning and incubation protection. The department has identified water bodies, or portions thereof, which require special protection for spawning and incubation in Ecology publication 06-10-038 (also available on Ecology’s website). This publication indicates where and when the following criteria are to be applied to protect the reproduction of native char, salmon, and trout:
  5. For lakes, human actions considered cumulatively may not increase the 7-DADMax temperature more than 0.3°C (0.54°F) above natural conditions.
  6. Temperature measurements should be taken to represent the dominant aquatic habitat of the monitoring site. This typically means samples should:
    1. Be taken from well mixed portions of rivers and streams.
    2. Not be taken from shallow stagnant backwater areas, within isolated thermal refuges, at the surface, or at the water's edge.
  7. The department will incorporate the following guidelines on preventing acute lethality and barriers to migration of salmonids into determinations of compliance with the narrative requirements for use protection established in this chapter (e.g., WAC 173-201A-310(1), 173-201A-400(4), and 173-201A-410 (1)(c)).

    The following site-level considerations do not, however, override the temperature criteria established for waters in subsection (1)(c) of this section or WAC 173-201A-602:
    1. Moderately acclimated (16-20°C, or 60.8-68°F) adult and juvenile salmonids will generally be protected from acute lethality by discrete human actions maintaining the7-DADMax temperature at or below 22°C (71.6°F) and the 1-day maximum (1-DMax) temperature at or below 23°C (73.4°F).
    2. Lethality to developing fish embryos can be expected to occur at a 1-DMax temperature greater than 17.5°C (63.5°F).
    3. To protect aquatic organisms, discharge plume temperatures must be maintained such that fish could not be entrained (based on plume time of travel) for more than two seconds at temperatures above 33°C (91.4°F) to avoid creating areas that will cause near instantaneous lethality.
    4. Barriers to adult salmonid migration are assumed to exist any time the 1-DMax temperature is greater than 22°C (71.6°F) and the adjacent downstream water temperatures are 3°C (5.4°F) or more cooler.
  8. Nothing in this chapter shall be interpreted to prohibit the establishment of effluent limitations for the control of the thermal component of any discharge in accordance with 33 U.S.C. 1326 (commonly known as section 316 of the Clean Water Act).


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Last updated October 2007