Box 12. Focus on U.S. Water Law and Regulation
There are several different water law regimes in the U.S. The two dominant regimes are the riparian doctrine, applied in most Eastern states (with some permutations on the West coast), and the prior appropriation doctrine, which applies in most states west of the 100th meridian. Under the riparian doctrine, landowners along waterways have “riparian rights” to the natural quantity and quality of flow in the waterway, except as diminished by the “reasonable use” of the water by other riparian landowners. Under riparian doctrine, the right to use the water may be obtained by purchasing land along the waterway.
Under the prior appropriation doctrine, water is allocated in specific amounts for “beneficial use.” Each water right has a priority date that determines its place in the hierarchy of withdrawals, and it maintains the same date even if it is sold to another user. Older water rights have priority over more recently created ones—“first in time, first in right”—and are therefore more valuable. In times of water shortage, holders of “younger” water rights are required to stop withdrawing water from the waterway to ensure that senior rights holders can withdraw the full amount they were allocated. Under prior appropriation, rights to specific amounts of water may be bought and sold by users without the requirement of riparian land ownership. Prior appropriation rights are generally considered stronger property rights than rights established under the riparian doctrine, and have been subjected to buying and selling in a marketplace. In some states, therefore, holders of water rights may benefit from shale development by selling a portion of their right to an operator.
Water rights are also governed by the federal reserved right doctrine, under which American Indian tribes retain rights to water even if those rights were not specifically allocated to them in treaties with the U.S. government; reclamation law, which is a specialized area of federal contract law for federal reclamation projects such as California’s Central Valley Project; and federal regulatory water rights, which are regulatory constraints (such as Endangered Species Act requirements) that often trump other water laws.