Prior Appropriation Doctrine

The Prior Appropriation Doctrine is a legal principle used in water rights, mainly in the western United States. It allocates water based on "first in time, first in right." This means that the first person to divert and use a specific water source has the priority to that water for their needs, even if they are downstream from others. Unlike riparian rights, which tie water access to land ownership, this doctrine emphasizes the actual use of water, encouraging efficient and beneficial use while protecting existing rights from being diminished by later users.