Idaho Code § 42-1501
The legislature of the state of Idaho hereby declares that the public health, safety and welfare require that the streams of this state and their environments be protected against loss of water supply to preserve the minimum stream flows required for the protection of fish and wildlife habitat, aquatic life, recreation, aesthetic beauty, transportation and navigation values, and water quality. The preservation of the water of the streams of this state for such purposes when made pursuant to this act is necessary and desirable for all the inhabitants of this state, is in the public interest and is hereby declared to be a beneficial use of such water. The legislature further declares that minimum stream flow is a beneficial use of water of the streams of this state for the purpose of protecting such waters from interstate diversion to other states or by the federal government for use outside the boundaries of the state of Idaho. Minimum stream flows as established hereunder shall be prior in right to any claims asserted by any other state, government agency, or person for out of state diversion. It is, therefore, necessary that authority be granted to receive, consider, approve or reject applications for permits to appropriate water of the streams of this state to such beneficial uses to preserve such water from subsequent appropriation to other beneficial uses under the provisions of chapter 2, title 42, Idaho Code.
Idaho Code § 42-1501