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.