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 IWRB in trust for Idaho citizens. Any person or entity can make a request to the IWRB 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 IWRB 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, which is fewer than 2% of the total stream miles in the state.