States generally apply the following legal principles:

Doctrine of Prior Appropriation
  • Also known as the Colorado doctrine, or "first in time, first in right."
  • No one entity can own the water in a stream.
  • All persons, corporations, and municipalities have the right to use the water for beneficial purposes.
  • A "senior appropriator" acquires a priority right of the water before any other appropriations are made.
  • "Junior appropriators" have a right to the water after the "senior appropriator" has fulfilled his/her need.
  • Individual states have determined their own administration on water rights and priority dates for the end user.
  • An appropriative right depends upon continued use of the water and may be lost as a result of nonuse.
  • Prior appropriation rights can generally be sold or transferred.
  • Long-term storage is permissible and common.

Doctrine of Riparian Rights
  • Also known as the eastern water law.
  • Riparian water rights occur as a result of land ownership.
  • In most cases, nonriparian landowners have no rights to the use of surface water.
  • Every owner of land bordering a stream has the right to make reasonable use of the water.
  • The water may be used as it passes through the property of the landowner but cannot be unreasonably detained or diverted.
  • The water used must be returned to the stream from which it was obtained.
  • Regulation is generally determined by "reasonable use" and is further determined by state water laws.
  • Rights cannot be lost as a result of nonuse.
  • Rights are indefinite in duration.

Modified Riparian Rights
  • Adopts principals of both western and eastern water laws.
  • These water rights are unique to Iowa.

Federal Reserved Water Rights
  • Also known as the Indian reserved water rights.
  • When Congress reserved land for Indian reservations, Congress also reserved water to fulfill the needs of the reservation.
  • Tribal rights to water are almost always senior to other claimants.
  • Western water officials must be aware of the Winters doctrine when planning for a stable allocation of water upon which all parties can rely.
  • Water claims of local Indian tribes must be satisfied prior to appropriation of western water rights.