Prior appropriation is a legal doctrine used in water rights management, primarily in the western United States. It operates on the principle of "first in time, first in right," meaning that the first person to divert water from a source for beneficial use has the right to continue using that water, even if others later seek to use it. Under this system, water rights are typically granted based on the amount of water used and the duration of that use. This encourages individuals and businesses to utilize water efficiently, as unused rights can be lost or forfeited over time.