Colorado Water Law as Customary Law: The South Platte and Arkansas River Basins

Abstract

"This paper tells the story of a particular manifestation of customary law - the 'Colorado Doctrine'. The Colorado Doctrine is based on the principle of prior appropriation. Prior appropriation allocates water on the basis of first in time, first in right. The person making the first appropriation of water from a stream holds rights to a portion of the water senior to all subsequent appropriators. The next person in time to appropriate water from that same stream holds rights to a portion of the water senior to all subsequent appropriators, but not to the first appropriator. Under such an allocation rule, if water is scarce, appropriators do not equally share in reductions, instead, the rights of senior appropriators are satisfied and junior appropriators are foreclosed. The justification for this is that in times of shortage, if all were to share equally in reductions no one would receive sufficient water to serve their purposes. Instead, it is better that at least some be served."