Water right

A water right is a property interest, separable from the land in most western states, and it is defined by a bundle of attributes rather than a single number: source, point of diversion, place of use, quantity, beneficial use, priority date and legal status. Change any one of them and you usually need state approval.

Because the right is separable, land and water can and often do trade independently. This is what makes a water-rights market possible, and also what makes buying land without checking the water underneath it a recurring and expensive mistake.