Part II–Designated Uses and Criteria

Dissolved Oxygen

Fresh water designated uses and criteria

Statutory Authority: Chapters 90.48 and 90.54 RCW. 03-14-129 (Order 02-14), § 173-201A-200, filed 7/1/03, effective 8/1/03.

(d) Aquatic life dissolved oxygen (D.O.) criteria. The D.O. criteria are measured in milligrams per liter (mg/L). Table 200 (1)(d) lists the 1-day minimum D.O. for each of the aquatic life use categories.


Table 200 (1)(d) Aquatic Life Dissolved Oxygen Criteria in Fresh Water


Lowest 1-Day Minimum
Char Spawning and Rearing 9.5 mg/L
Core Summer Salmonid Habitat 9.5 mg/L
Salmonid Spawning, Rearing, and Migration 8.0 mg/L
Salmonid Rearing and Migration Only 6.5 mg/L
Non-anadromous Interior Redband Trout 8.0 mg/L
Indigenous Warm Water Species 6.5 mg/L


  1. When a waterbody's D.O. is lower than the criteria in Table 200 (1)(d) (or within 0.2 mg/L of the criteria) and that condition is due to natural conditions, then human actions considered cumulatively may not cause the D.O. of that water body to decrease more than 0.2 mg/L.
  2. For lakes, human actions considered cumulatively may not decrease the dissolved oxygen concentration more than 0.2 mg/L below natural conditions.
  3. Concentrations of D.O. are not to fall below the criteria in the table at a probability frequency of more than once every ten years on average.
  4. D.O. 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.


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Last updated October 2007