Idaho constitution
Article XV
Section 5

Whenever more
than one person has settled upon, or improved land with the view of receiving water
for agricultural purposes, under a sale, rental, or distribution thereof, as in the last
preceding section of this article provided, as among such persons, priority in time
shall give superiority of right to the use of such water in the numerical order of
such settlements or improvements; but whenever the supply of such water shall not
be sufficient to meet the demands of all those desiring to use the same, such priority
of right shall be subject to such reasonable limitations as to the quantity of water
used and times of use as the legislature, having due regard both to such priority of
right and the necessities of those subsequent in time of settlement or improvement,
may by law prescribe.