Water Quality

Turbidity rulemaking
Note: DEQ has postponed this rulemaking. We will notify interested parties once we resume the rulemaking.


Turbidity measures the “cloudiness” of water using the penetration of light through water. Increased levels of turbidity are caused by matter 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 for regulatory purposes, can cause public drinking water treatment systems to shut down and increase operation and maintenance costs. 

Turbidity technical review

DEQ prepared a review summarizing the scientific literature and data on the effect of turbidity on beneficial uses.  The document may, in the future, assist DEQ in developing a revised turbidity criteria based on the best available science.  The document was reviewed by a panel of scientific experts with expertise in stream, lake, estuarine ecology, hydrology and aquatic biology.


Aron Borok, 503-229-5050, toll-free in Oregon at 800-452-4011, ext. 5050