Idaho Code § 42-222
When the nature of use of the water right is to be changed to municipal purposes and some or all of the right will be held by a municipal provider to serve reasonably anticipated future needs, the municipal provider shall provide to the department sufficient information and documentation to establish that the applicant qualifies as a municipal provider and that the reasonably anticipated future needs, the service area and the planning horizon are consistent with the definitions and requirements specified in this chapter. The service area need not be described by legal description nor by description of every intended use in detail, but the area must be described with sufficient information to identify the general location where the water under the water right is to be used and the types and quantity of uses that generally will be made.
When a water right or a portion thereof to be changed is held by a municipal provider for municipal purposes, as defined in section 42-202B, Idaho Code, that portion of the right held for reasonably anticipated future needs at the time of the change shall not be changed to a place of use outside the service area, as defined in section 42-202B, Idaho Code, or to a new nature of use.
The director of the department of water resources shall examine all the evidence and available information and shall approve the change in whole, or in part, or upon conditions, provided no other water rights are injured thereby, the change does not constitute an enlargement in use of the original right, the change is consistent with the conservation of water resources within the state of Idaho and is in the local public interest as defined in section 42-202B, Idaho Code, the change will not adversely affect the local economy of the watershed or local area within which the source of water for the proposed use originates, in the case where the place of use is outside of the watershed or local area where the source of water originates, and the new use is a beneficial use, which in the case of a municipal provider shall be satisfied if the water right is necessary to serve reasonably anticipated future needs as provided in this chapter. The director may consider consumptive use, as defined in section 42-202B, Idaho Code, as a factor in determining whether a proposed change would constitute an enlargement in use of the original water right. The director shall not approve a change in the nature of use from agricultural use where such change would significantly affect the agricultural base of the local area. The transfer of the right to the use of stored water for irrigation purposes shall not constitute an enlargement in use of the original right even though more acres may be irrigated, if no other water rights are injured thereby. A copy of the approved application for change shall be returned to the applicant and he shall be authorized upon receipt thereof to make the change and the original water right shall be presumed to have been amended by reason of such authorized change. In the event the director of the department of water resources determines that a proposed change shall not be approved as provided in this section, he shall deny the same and forward notice of such action to the applicant by certified mail, which decision shall be subject to judicial review as hereafter set forth. Provided however, minimum stream flow water rights may not be established under the local public interest criterion, and may only be established pursuant to chapter 15, title 42, Idaho Code.
Idaho Code § 42-222