Idaho Code § 42-1505
In his direction and control of the distribution of water from the streams of this state under the provisions of chapter 6, title 42, Idaho Code, the director shall consider any approved application for appropriation of minimum stream flow filed under the provisions of this act as a water right with priority date as of the date of receipt in the office of the director of a complete application. Water shall not be deemed to be available to fill any water right of later priority date if diversion of such water would result in a decrease in the flow of the stream or level of the lake below the minimum stream flow or minimum lake level specified in said approved application for appropriation of minimum stream flow at the locations described in said approved application.
Idaho Code § 42-1505