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Water Quality Standards for Conventional Parameters

Water quality for parameters such as dissolved oxygen (D.O.), pH, turbidity, nutrients and temperature are often referred to as conventional parameters. These parameters are present at some level in healthy functioning aquatic ecosystems, but may impair uses if they are too high or too low.

Parameter specific information

Oregon's Bacteria Standards - OAR 340-041-0009

On Aug. 17, 2016, the Environmental Quality Commission approved revisions to Oregon's water quality standards for bacteria to protect people who recreate in coastal waters. EPA approved the revised standards under the Clean Water Act on Nov. 17, 2017. Exposure to high levels of bacteria from swimming and other full immersion water contact recreation is associated with increased gastrointestinal illness. The bacteria standards also protect people who eat shellfish.

In addition to revising the bacteria criteria for coastal recreation waters, the 2016 rule revisions clarify where freshwater and coastal recreation and shellfish harvesting uses occur in coastal estuaries and, therefore, where the different bacteria criteria (E. coli, enterococcus, or fecal coliform) apply.

Additional resources

The Oregon Health Authority's Oregon Beach Monitoring Program issues beach advisories based on a Beach Action Value. Information is available on the OBMP web page.


Low dissolved oxygen levels can impair aquatic life.

Additional resources

For additional information about application of the DO standard, see the “Additional Resources for Conventional Parameters" section at the bottom of the page.​

pH is a measure of hydrogen ion concentration in water. High or low pH can impair aquatic life. Oregon's pH water quality standards for freshwater are basin specific. For additional memos and documents regarding pH, see the “Additional Resources for Conventional Parameters" section at the bottom of the page.


Turbidity measures the “cloudiness" of water using the penetration of light through water. Increased levels of turbidity are caused by sediment and other matter suspended in the water column. Scientific literature indicates that turbidity reduces growth of aquatic plants and interferes with the ability of fish to catch prey. Increased turbidity levels also reduce the desirability of waters for recreational uses. High levels of suspended sediment, usually measured as turbidity , can interfere with public drinking water treatment and increase operation and maintenance costs. 

DEQ prepared a summary of the scientific literature on the effect of turbidity on beneficial uses.  The document was reviewed by a panel of scientific experts with expertise in stream, lake, estuarine ecology, hydrology and aquatic biology.

Additional resources


Oregon has several water quality standards that address excessive algal and plant growth which may impair waters. Excess algal growth can lead to decreased dissolved oxygen, impairment of drinking water sources, and toxic harmful algal blooms.

Chlorophyll is a pigment compound that gives plants and algae a green color. Oregon uses chlorophyll a action values to identify waterbodies where excessive blooms may impair beneficial uses.

Nuisance Phytoplankton Growth Standards​ -OAR 340-041-0019 

Oregon also addresses excessive algae and plant growth and the nutrient levels that may cause them using the statewide narrative criteria.  Toxic harmful algal blooms are also addressed using the narrative standard in conjunction with Oregon Health Authority drinking water health advisory levels. 

Statewide Narrative Standards – OAR 340-041-0007

Excess nutrients (phosphorus and/or nitrogen) can result in excess algal growth in aquatic ecosystems that can impair beneficial uses, such as aquatic life and recreation. While Oregon does not have numeric phosphorus or nitrogen numeric criteria, Oregon does employ other nutrient reduction strategies.​