	Introduction

Although allocation of water resources is generally a matter of state law, the federal government may also allocate water rights. Because federal reserved water rights under the Winters doctrine often have not been quantified but are generally senior to other water rights, the rights of more junior water users can be affected significantly, when these federal rights are exercised. It analyzes the scope of these rights, including the water sources that may be used to fulfill the rights and the quantification standards courts commonly use to clarify the rights. The report also examines the effect of the McCarran Amendment, through which Congress authorized state courts to adjudicate Indian reserved water rights. The Winters Doctrine of Reserved Water Rights

In Winters , the Supreme Court examined tribal rights to water associated with the Fort Belknap Reservation located in what would later become Montana. Scope of Winters Rights

Under the Winter s doctrine, the priority and extent of Indian reserved water rights is affected by the purposes of the Indian reservation, the date when the Indian reservation was created, the quantification of water sufficient to accomplish those purposes, and the sources of water that may be used to fulfill the particular water rights. Effect on State Water Allocation

Although the federal government may act under a number of constitutional authorities to regulate water, in most instances it has deferred to the states. States either adhere to a riparian or prior appropriation system of water allocation. Other states, typically the drier western states, use a prior appropriation system of water rights. It is unclear, however, whether the primary purpose standard the Supreme Court adopted when applying Winters in non-Indian reserved water rights cases governs Indian reserved water rights. As discussed later in this report, courts quantify the amount of Indian reserved water rights based on the purposes of the reservation. In other words, an Indian reserved water right cannot trump senior rights that existed at the time of reservation. The court instead offered a number of potential factors for consideration in the quantification: 1) the tribe's history of and cultural need for water; 2) the nature of the land and associated resources of the reservation; 3) the tribe's economic status and the proposed economic development to the extent that they involve a need for water; 4) historic reliance of the tribe on water for the proposed purpose; and 5) the tribe's current and projected population. Adjudication of Indian Reserved Water Rights

Indian reserved water rights are subject to adjudication by federal and state courts. Federal courts have historically been authorized via federal question jurisdiction to determine Indian reserved water rights under the Winters doctrine.
Although the federal government has authority to regulate water, it typically defers to the states to allocate water resources within the state. The federal government maintains certain federal water rights, though, which exist separate from state law. In particular, federal reserved water rights often arise in questions of water allocation related to federal lands, including Indian reservations. Indian reserved water rights were first recognized by the U.S. Supreme Court in Winters v. United States in 1908. Under the Winters doctrine, when Congress reserves land (i.e., for an Indian reservation), Congress also reserves water sufficient to fulfill the purpose of the reservation.
As the need for water grows with the development of new industries and growing populations, the tension arising from the allocation of scarce water resources highlights the difficulties that often surround reserved water rights, particularly in the western states. Western states generally follow some form of the prior appropriation system of water allocation. The prior appropriation system allocates water to users based on the order in which water rights were properly acquired. Because Indian reserved water rights date back to the government's reservation of the land for the Indians, these water rights often pre-date other water users' claims. Although the prior appropriation system's reliance on seniority provides a degree of certainty to water allocation, Indian reserved water rights may not have been quantified at the time of reservation. Because Winters did not dictate a formula to determine the quantity of water reserved, courts apply different standards to quantify tribal reserved water rights. As a result, other water users may not know whether, or the extent to which, Indian reserved water rights have priority. Because of these uncertainties, Indian reserved water rights are often litigated or negotiated in settlements and related legislation.
This report will examine the creation of Indian reserved water rights under the Winters doctrine. It will analyze the scope of the doctrine, including the purposes for which the water right may be claimed and the sources from which the water may be drawn. It will also discuss various quantification standards that courts have used in attempting to clarify Indian reserved water rights. Finally, it will examine the effect of the McCarran Amendment, through which Congress extended jurisdiction to state courts to hear disputes involving Indian reserved water rights.