Idaho constitution
Article XV
Section 3

The right to
divert and appropriate the unappropriated waters of any natural stream to beneficial
uses, shall never be denied, except that the state may regulate and limit the use
thereof for power purposes. Priority of appropriation shall give the better right as
between those using the water; but when the waters of any natural stream are not
sufficient for the service of all those desiring the use of the same, those using the
water for domestic purposes shall (subject to such limitations as may be prescribed
by law) have the preference over those claiming for any other purpose; and those
using the water for agricultural purposes shall have preference over those using the
same for manufacturing purposes. And in any organized mining district those using
the water for mining purposes or milling purposes connected with mining, shall have
preference over those using the same for manufacturing or agricultural purposes.
But the usage by such subsequent appropriators shall be subject to such provisions
of law regulating the taking of private property for public and private use, as
referred to in section 14 of article I of this Constitution.