Idaho Code § 42-226
The traditional policy of the state of Idaho, requiring the water resources of this state to be devoted to beneficial use in reasonable amounts through appropriation, is affirmed with respect to the ground water resources of this state as said term is hereinafter defined and, while the doctrine of "first in time is first in right" is recognized, a reasonable exercise of this right shall not block full economic development of underground water resources. Prior appropriators of underground water shall be protected in the maintenance of reasonable ground water pumping levels as may be established by the director of the department of water resources as herein provided. In determining a reasonable ground water pumping level or levels, the director of the department of water resources shall consider and protect the thermal and/or artesian pressure values for low temperature geothermal resources and for geothermal resources to the extent that he determines such protection is in the public interest. All ground waters in this state are declared to be the property of the state, whose duty it shall be to supervise their appropriation and allotment to those diverting the same for beneficial use. This act shall not affect the rights to the use of ground water in this state acquired before its enactment.
Any application for a water permit that seeks to transfer ground water outside the immediate ground water basin as defined by the director of the department of water resources for the purpose of irrigating five thousand (5,000) or more acres on a continuing basis or for a total volume in excess of ten thousand (10,000) acre feet per year, the application must first be approved by the director of the department of water resources and then by the Idaho legislature. Each shall give due consideration to the local economic and ecological impact of the project or development so proposed.
Idaho Code § 42-226