In the American legal system, prior appropriation water rights is the doctrine that the first person to take a quantity of water from a water source for "beneficial use" (agricultural, industrial or household) has the right to continue to use that quantity of water for that purpose. Subsequent users can take the remaining water for their own use if they do not impinge on the rights of previous users. The doctrine is sometimes summarized, "first in time, first in right". Prior appropriation rights do not constitute a full ownership right in the water, merely the right to withdraw it, and can be abrogated if not used for an extended period of time.
Origin Water is very scarce in the Western United States and so must be allocated sparingly, based on the productivity of its use. The prior appropriation doctrine developed from Spanish (and later Mexican) civil law and differs from the riparian water rights that apply in the rest of the United States. The appropriation doctrine originated in Gold-Rush–era California, when miners sought to acquire water for mining operations. In the 1855 case of Irwin v. Phillips, Matthew Irwin diverted a stream for his mining operation. Shortly afterward, Robert Phillips started a mining operation downstream and eventually tried to divert the water back to its original streambed. The case was taken to the California Supreme Court, which ruled for Irwin.
Nature of the right The legal details of prior appropriation vary from state to state. Under the prior appropriation system, the right is initially allotted to those who are "first in time of use"; these rights of withdrawal can then trade on the open market, like other property. For water sources with many users, a government or quasi-government agency is usually charged with overseeing allocations. Allocations involving water sources that cross state borders or international borders can be quite contentious, and are generally governed by federal court rulings, interstate agreements and international treaties. A claim of prior appropriation must prove four sub-claims: diversion (that the water had been withdrawn), priority (that the withdrawer had diverted water prior to the other claimant), intent (that the water had been withdrawn by design), and beneficial use (that the water was put to a publicly-acceptable end). If proved, the initial person to use a quantity of water from a water source for a beneficial use has the right to continue to use the same quantity of water for the same purpose. Subsequent users can use the remaining water for their own beneficial purposes provided that they do not impinge on the rights of previous users; this is the priority element of the doctrine. But neither can a senior user change the manner (i.e., location) in which they appropriate water to the detriment of a junior user. These Preservation of Conditions were granted to the second user after Farmers Highline Canal & Reservoir Co. v. City of Golden, 272 P.2d 629 (Colo. 1954). A senior water user could, for example, only have been using the water during a particular season. Then the purchaser of the water right could only use the water in the same season as when the right was established. In addition, the state may put additional conditions on the use of the water right to prevent polluting or inefficient uses of water. Beneficial use is commonly defined as agricultural, industrial or household use. The doctrine has historically excluded ecological purposes, such as maintaining a natural body of water and the wildlife that depends on it, but some jurisdictions now accept such claims. The extent to which private parties may own such rights varies among the states. Each water right has a yearly quantity and an appropriation date. Each year, the user with the earliest appropriation date (known as the "senior appropriator") may use up to their full allocation (provided the water source can supply it). Then the user with the next earliest appropriation date may use their full allocation and so on. In cases of water shortages, prior-appropriation does not require a senior user to utilize less water than usual. Therefore, during times of drought, users with junior appropriation dates might not receive their full allocation or even any water at all. When a water right is sold, it retains its original appropriation date. Only the amount of water historically consumed can be transferred if a water right is sold. For example, if alfalfa is grown using flood irrigation, the amount of the return flow may not be transferred, only the amount that would be necessary to irrigate the amount of alfalfa historically grown. Prior appropriation rights are subject to certain adverse possession-type rules to reduce speculation. Withdrawal rights can be lost or shrunk over time if unused for a certain number of years, or if a litigant can demonstrate that the water's use is not beneficial. Abandonment of a water right is rare, but occurred in Colorado in a case involving the South Fork of San Isabel Creek in Saguache County.
Interaction with other allocation methods In some states, junior upstream water users may take water from downstream users, as long as they return the water in comparable quantity and quality. California and Texas grant waterfront property owners water allocations prior to any other users, in a hybrid system with riparian water rights. In Oregon, landowners have rights to water on their own land at a certain time at which it is then incorporated into the appropriation system.
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