DOCTRINE OF EQUITY
The doctrine of equity is a principle of inter-jurisdictional water allocation developed by the U.S. Supreme Court in response to interstate water conflicts. It is a doctrine of necessity because of the juxtaposition of the legal theory allowing each state to develop its own form of water law against the physical reality that streams flow from one state to another. The doctrine states that when there is a disagreement over the water use of an interstate stream, the court must fashion an equitable apportionment of the water that serves the needs of water users in both states. Equitable apportionment of the water is not based on any mathematical formula but on a fair consideration of all the interests involved.
The doctrine originated in the Great Plains, where water flows not only from west to east but also from appropriation water law jurisdictions to riparian water law jurisdictions. Water allocation and consumptive uses of water by an upstream state have significant consequences when downstream states seek to use water of the same stream. Such was the case with the states of Colorado and Kansas. In 1901 Kansas sued Colorado on behalf of water users of the Arkansas River in western Kansas, alleging that Colorado, through its appropriation law, had encouraged its citizens to consume the water of the Arkansas to the detriment of the people in Kansas. Colorado countered, maintaining that as an independent state it had the right to use all the water it needed, even to the detriment of Kansas residents. By 1904, the case, Kansas v. Colorado, had reached the U.S. Supreme Court. In 1907 the Supreme Court rejected both positions. Justice David Brewer, a native of Kansas, wrote the court's opinion. While the Court did not find that Colorado had injured residents of southwestern Kansas to any great degree, it did establish the principle of the "equality of right," which fashioned a remedy requiring courts to ensure each state an equitable opportunity to use interstate stream water. This balancing of relative economic advantages continues to determine decisions on interstate water disputes.
See also LAW: Brewer, David.
Theron Josephson Ferris State University
Dunbar, Robert G. Forging New Rights in Western Water. Lincoln: University of Nebraska Press, 1983.
Hutchins, W. A. Water Rights in the Nineteen Western States. Washington DC: Government Printing Office, 1974.
Trelease, Frank J., and George A. Gould. Cases and Materials on Water Law, 4th ed. St. Paul MN: West Publishing Company, 1986.