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Protecting stream flows

State law requires that enough water is kept in streams and rivers to protect and preserve instream resources and values such as fish, wildlife, recreation, aesthetics, water quality, and navigation. One of the most effective tools for protecting streamflows is to set instream flows, which are flow levels adopted into rule. Instream flows cover nearly half of the state’s watersheds and the Columbia River.

About instream flows

Instream flows are an element of water and river management — finding ways to maintain healthy and diverse ecosystems that are part of Washington’s high quality of life, while sustaining basic life functions and economies.

Setting instream flows protects the river from new withdrawals that would harm instream resources. Instream flows do not put water in the streams and do not affect existing (senior) water rights.

Setting instream flows in rule is a complex process, involving:

  • Scientific flow studies to determine what flow levels are needed to preserve the uses and values of individual rivers and streams.
  • Developing methods to allow for future development.
  • Working with local agencies, tribes, businesses, environmental groups, and concerned citizens throughout the rule development and adoption process.
How do instream flows work?
Why is protecting streamflows important?
How are instream flow levels chosen?
Why not set instream flows lower than existing stream flows?
Why are instream flows sometimes higher than the flow in the stream?
How could instream flows affect me?
Why is groundwater use affected by an instream flow rule?