Minimum Streamflows

Idaho's Minimum Stream Flow Program was approved by the Legislature in 1978 to preserve stream flows and lake elevations for public health, safety, and welfare. The minimum stream flow is the amount of flow necessary to preserve desired stream values, including fish and wildlife habitat, aquatic life, navigation and transportation, recreation, water quality, and aesthetic beauty.


Minimum stream flow water rights are held by the Idaho Water Resource Board in trust for Idaho citizens ( Chapter 15, Title 42, Idaho Code). Any person or entity can make a request to the Idaho Water Resource Board to file an application for stream flow on any water body within the state.



To be approved, a minimum stream flow water right must:

  • be in the public interest,
  • not adversely affect senior water rights,
  • represent the minimum flow and not the desirable flow, and
  • be capable of being maintained.

The Idaho Water Resource Board currently holds 291 water rights or permits for minimum stream flows, and 3 water rights for minimum lake levels. These licenses cover 994 miles of Idaho streams, fewer than 2% of the total stream miles in the state.




Billingsley Creek near Hagerman, Idaho.




Elk Creek Falls in the North Fork Clearwater River basin.