Water Quality

Water quality standards are established to protect beneficial uses of the state's waters. Beneficial uses are designated for all waters of the state in the Oregon Administrative Rules for water quality standards (Chapter 340, Division 41). In some cases, beneficial uses vary by waterbody or reach. In other cases, uses are designated for all waters in a basin or sub-basin.

Beneficial uses include:    

  • Fish and aquatic life
  • Water contact recreation
  • Fishing
  • Domestic water supply
  • Industrial water supply
  • Boating
  • Irrigation
  • Livestock watering
  • Aesthetic quality
  • Wildlife and hunting​
  • Hydropower
  • Commercial navigation and transportation

Water quality standards include designated beneficial uses  and water quality criteria established to protect the sensitive beneficial uses. For example, the uses most sensitive to dissolved oxygen are fish and aquatic life. Fish and other aquatic organisms need an adequate supply of oxygen in the water to be healthy and productive. In this case, the criteria identify minimal amounts of dissolved oxygen that need to be in the water to protect the fish. In other cases, such as bacteria or some toxic substances, human health is the most sensitive beneficial use. These criteria identify the maximum concentration that may be in the water without risk to aquatic organisms or human health.

The designated uses for each basin may be found in OAR 340-041-0101 through OAR 340-041-0340. Each basin has a designated use rule that shows the uses in tables and maps. Links to each basin’s use rule are provided below. Corresponding tables and maps can be downloaded in PDF format by clicking on the link within the rule. One table identifies all the beneficial uses that are designated within the basin. Additional tables and maps identify categories of fish and aquatic life, shellfish harvesting, and contact recreation, which vary by waterbody. The maps also show where estuarine waters end and freshwater begins in coastal basins.

Designated Beneficial Uses Tables and Maps by Basin