[647] Mr. Justice Rehnquist
delivered the opinion of the Court.
The United States seeks to impound 2.4 million acre-feet of water from California’s Stanislaus River as part of its Central Valley Project. The California State Water Resources Control Board ruled that the water could not be allocated to the Government under state law unless it agreed to and complied with various conditions dealing with the water’s use. The Government then sought a declaratory judgment in the District Court for the Eastern District of California to the effect that the United States can impound whatever unappropriated water is necessary for a federal reclamation project without complying with state' law. The District Court held that, as a matter of comity, the United States must apply to the State for an appropriation permit, but that the State must issue the permit without condition if there is sufficient unappropriated water. 403 F. Supp. 874 (1975). The Court of Appeals for the Ninth Circuit affirmed, but held that § 8 of the Reclamation Act of 1902, 32 Stat. 390, as codified, 43 U. S. C. §§ 372, 383, rather than comity, requires the United States to apply for the permit. 558 F. 2d 1347 (1977). We granted certiorari to review the decision of the Court of Appeals insofar as it holds that California cannot condition its allocation of water to a federal reclamation project. 434 U. S. 984 (1977). We now reverse.
[648] I
Principles of comity and federalism, which the District Court and the Court of Appeals referred to and which have received considerable attention in our decisions, are as a legal matter based on the Constitution of the United States, statutes enacted by Congress, and judge-made law. But the situations invoking the application of these principles have contributed importantly to their formation. Just as it has been truly said that the life of the law is not logic but experience, see 0. Holmes, The Common Law 1 (1881), so may it be said that the life of the law is not political philosophy but experience.
The very vastness of our territory as a Nation, the different times at which it was acquired and settled, and the varying physiographic and climatic regimes which obtain in its different parts have all but necessitated the recognition of legal distinctions corresponding to these differences. Those who first set foot in North America from ships sailing the tidal estuaries of Virginia did not confront the same problems as those who sailed flat boats down the Ohio River in search of new sites to farm. Those who cleared the forests in the old Northwest Territory faced totally different physiographic problems from those who built sod huts on the Great Plains. The final expansion of our Nation in the 19th century into the arid lands beyond the hundredth meridian of longitude, which had been shown on early maps as the “Great American Desert,” brought the participants in that expansion face-to face with the necessity for irrigation in a way that no previous territorial expansion had.
In order to correctly ascertain the meaning of the Reclamation Act of 1902, we must recognize the obvious truth that the history of irrigation and reclamation before that date was much fresher in the minds of those then in Congress than it is to us today. “[T]he afternoón of July 23, 1847, was the true date of the beginning of modern irrigation. It was on that afternoon that the first band of Mormon pioneers built a small [649] dam across City Creek near the present site of the Mormon Temple and diverted sufficient water to saturate some 5 acres of exceedingly dry land. Before the day was over they had planted potatoes to preserve the seed.” 1 During the subsequent half century, irrigation expanded throughout the arid States of the West, supported usually by private enterprise or the local community.2 By the turn of the century, however, most of the land which could be profitably irrigated by such small-scale projects had been put to use. Pressure mounted on the Federal Government to provide the funding for the massive projects that would be needed to complete the reclamation, culminating in the Reclamation Act of 1902.3
The arid lands were not all susceptible of the same sort of reclamation. The climate and topography of the lands that constituted the “Great American Desert” were quite different from the climate and topography of the Pacific Coast States. As noted in both United States v. Gerlach Live Stock Co., 339 U. S. 725 (1950), and Ivanhoe Irrigation District v. McCracken, 357 U. S. 275 (1958), the latter States not only had a more pronounced seasonal variation and precipitation than the intermountain States, but the interior portions of California had climatic advantages which many of the intermountain States did not.
“The prime value in our national economy of the lands of summer drought on the Pacific coast is as a source of [650] plant products that require mild winters and long growing seasons. Citrus fruits, the less hardy deciduous fruits, fresh vegetables in winter — these are their most important contributions at present. Rainless summers make possible the inexpensive drying of fruits, which puts into the market prunes, raisins, dried peaches, and apricots. In its present relation to American economy in general, the primary technical problem of agriculture in the Pacific Coast States is to make increasingly more effective use of the mild winters and the long growing season in the face of the great obstacle presented by the rainless summers. To overcome that obstacle supplementary irrigation is necessary. Hence the key position of water in Pacific Coast agriculture.” 4
If the term “cooperative federalism” had been in vogue in 1902, the Reclamation Act of that year would surely have qualified as a leading example of it. In that Act, Congress set forth on a massive program to construct and operate dams, reservoirs, and canals for the reclamation of the arid lands in 17 Western States. Reflective of the “cooperative federalism” which the Act embodied is § 8, whose exact meaning and scope are the critical inquiries in this case:
“[N]othing in this Act shall he construed as affecting or intended to affect or to in any way interfere with the laws of any State or Territory relating to the control, appropriation, use, or distribution of water used in irrigar tion, or any vested right acquired thereunder, and the Secretary of the Interior, in carrying out the provisions of this Act, shall proceed in conformity with such laws, and nothing herein shall in any way affect any right of any State or of the Federal Government or of any landowner, appropriator, or user of water in, to, or from any interstate stream or the waters thereof: Provided, that the [651] right to the use of water acquired under the provisions of this Act shall be appurtenant to the land irrigated, and beneficial use shall be the basis, the measure, and the limit of the right.” 32 Stat. 390 (emphasis added).
Perhaps because of the cooperative nature of the legislation, and the fact that Congress in the Act merely authorized the expenditure of funds in States whose citizens were generally anxious to have them expended, there has not been a great deal of litigation involving the meaning of its language. Indeed, so far as we can tell, the first case to come to this Court involving the Act at all was Ickes v. Fox, 300 U. S. 82 (1937), and the first case to require construction of § 8 of the Act was United States v. Gerlach Live Stock Co., supra, decided nearly half & century after the enactment of the 1902 statute.5
The New Melones Dam, which this litigation concerns, is part of the California Central Valley Project, the largest reclamation project yet authorized under the 1902 Act.6 The Dam, which will impound 2.4 million acre-feet of water of California's Stanislaus River, has the multiple purposes of flood control, irrigation, municipal use, industrial use, power, recreation, water-quality control, and the protection of fish and wildlife. The waters of the Stanislaus River that will be impounded behind the New Melones Dam arise and flow solely in California.
[652] The United States Bureau of Reclamation, as it has with every other federal reclamation project, applied for a permit from the appropriate state agency, here the California State Water Resources Control Board, to appropriate the water that would be impounded by the Dam and later used for reclamation.7 After lengthy hearings, the State Board found that unappropriated water was available for the New Melones Dam during certain times of the year. Although it therefore approved the Bureau's applications, the State Board attached 25 conditions to the permit. California State Water Resources Control Board, Decision 1422 (Apr. 14, 1973). The most important conditions prohibit full impoundment until the Bureau is able to show firm commitments, or at least a specific plan, for the use of the water.8 The State Board [653] concluded that without such a specific plan of beneficial use the Bureau had failed to meet the California statutory requirements for appropriation.
“The limited unappropriated water resources of the State should not be committed to an applicant in the absence of a showing of his actual need for the water within a reasonable time in the future. When the evidence indicates, as it does here, that an applicant already has a right to sufficient water to meet his needs for beneficial use within the foreseeable future, rights to additional water should be withheld and that water should be reserved for other beneficial uses.” Id., at 16.
II
The history of the relationship between the Federal Government and the States in the reclamation of the arid lands of the Western States is both long and involved, but through it runs the consistent thread of purposeful and continued deference to state water law by Congress. The rivers, streams, and lakes of California were acquired by the United States under the 1848 Treaty of Guadalupe Hidalgo with the Republic of Mexico, 9 Stat. 922. Within a year of that treaty, the California gold rush began, and the settlers in this new land quickly realized that the riparian doctrine of water rights that had served well in the humid regions of the East would not work in the arid lands of the West. Other settlers coming into the intermountain area, the vast basin and range country which lies between the Rocky Mountains on the east and the Sierra Nevada and Cascade Ranges on the west, were forced to the same conclusion. In its place, the doctrine of prior appropriation, linked to beneficial use of the water, arose through local customs, laws, [654] and judicial decisions. Even in this early stage of the development of Western water law, before many of the Western States had been admitted to the Union, Congress deferred to the growing local law. Thus, in Broder v. Water Co., 101 U. S. 274 (1879), the Court observed that local appropriation rights were “rights which the government had, by its conduct, recognized and encouraged and was bound to protect.” Id., at 276.
In 1850, California was admitted as a State to the Union “on an equal footing with the original States in all respects whatever.” 9 Stat. 452. While § 3 of the Act admitting California to the Union specifically reserved to the United States all “public lands” within the limits of California, no provision was made for the unappropriated waters in California's streams and rivers. One school of legal commentators held the view that, under the equal-footing doctrine, the Western States, upon their admission to the Union, acquired exclusive sovereignty over the unappropriated waters in their streams. In 1903, for example, one leading expert on reclamation and water law observed that “[i]t has heretofore been assumed that the authority of each State in the disposal of the water-supply within its borders was unquestioned and supreme, and two of the States have constitutional provisions asserting absolute ownership of all water-supplies within their bounds.” E. Mead, Irrigation Institutions 372 (1903).9 Such commentators were not without some support from language [655] in contemporaneous decisions of this Court. See S. Wiel, Water Nights in the Western States §§ 40-43, pp. 84t-95 (2d ed. 1908). Thus, in Kansas v. Colorado, 206 U. S. 46 (1907), the Court noted:
“While arid lands are to be found mainly, if not only in the Western and newer States, yet the powers of the National Government within the limits of those States are the same (no greater and no less) than those within the limits of the original thirteen.
“In the argument on the demurrer counsel for plaintiff endeavored to show that Congress had expressly imposed the common law on all this territory prior to its formation into States. . . . But when the States of Kansas and Colorado were admitted into the Union they were admitted with the full powers of local sovereignty which belonged to other States, Pollard v. Hagan, [3 How. 212]; Shively v. Bowlby, [152 U. S. 1]; Hardin v. Shedd, 190 U. S. 508, 519; and Colorado by its legislation has recognized the right of appropriating the flowing waters to the purposes of irrigation.” Id., at 92 and 95.
And see United States v. Rio Grande Dam & Irrig. Co., 174 U. S. 690, 702-703, and 709 (1899).
As noted earlier, reclamation of the arid lands began almost immediately upon the arrival of pioneers to the Western States. Huge sums of private money were invested in systems to transport water vast distances for mining, agriculture, and ordinary consumption. Because a very high percentage of land in the West belonged to the Federal Government, the canals and ditches that carried this water frequently crossed [656] federal land. In 1862, Congress opened the public domain to homesteading. Homestead Act of 1862, 12 Stat. 392. And in 1866, Congress for the first time expressly opened the mineral lands of the public domain to exploration and occupation by miners. Mining Act of 1866, ch. 262, 14 Stat. 251. Because of the fear that these Acts might in some way interfere with the water rights and systems that had grown up under state and local law, Congress explicitly recognized and acknowledged the local law:
“[WJhenever, by priority of possession, rights to the use of water for mining, agricultural, manufacturing, or other purposes, have vested and accrued, and the same are recognized and acknowledged by the local customs, laws, and the decisions of courts, the possessors and owners of such vested rights shall be maintained and protected in the same.” § 9, 14 Stat. 253.
The Mining Act of 1866 was not itself a grant of water rights pursuant to federal law. Instead, as this Court observed, the Act was “ ‘a voluntary recognition of a preexisting right of possession, constituting a valid claim to its continued use.’ ” United States v. Rio Grande Dam & Irrig. Co., supra, at 705. Congress intended “to recognize as valid the customary law with respect to the use of water which had grown up among the occupants of the public land under the peculiar necessities of their condition.” 10 Basey v. Gallagher, 20 Wall. 670, 684 (1875). See Broder v. Water Co., supra, at 276; Jennison v. Kirk, 98 U. S. 453, 459-461 (1879).11
[657] In 1877, Congress took its first step toward encouraging the reclamation and settlement of the public desert lands in the West and made it clear that such reclamation would generally follow state water law. In the Desert Land Act of 1877, Congress provided for the homesteading of arid public lands in larger tracts
“by [the homesteader’s] conducting water upon the same, within the period of three years [after filing a declaration to do so], Provided however that the right to the use of water by the person so conducting the same . . . shall not exceed the amount of water actually appropriated, and necessarily used for the purpose of irrigation and reclamation: and all surplus water over and above such actual appropriation and use, together with the water of all, lakes, rivers and other sources of water supply upon the public lands and not navigable, shall remain and be held free for the appropriation and use of the public for irrigation, mining and manufactuing purposes subject to existing rights.” Ch. 107, 19 Stat. 377 (emphasis added).
This Court has had an opportunity to construe the 1877 Desert Land Act before. In California Oregon Power Co. v. Beaver Portland Cement Co., 295 U. S. 142 (1935), Mr. Justice Sutherland12 explained that, through this language, Congress [658] “effected a severance of all waters upon the public domain, not theretofore appropriated, from the land itself.” Id., at 158. The nonnavigable waters thereby severed were “reserved for the use of the public under the laws of the states and territories.” Id., at 162. Congress’ purpose was not to federalize the prior-appropriation doctrine already evolving under local law. Quite the opposite:
“What we hold is that following the act of 1877, if not before, all non-navigable waters then a part of the public domain became publici juris, subject to the plenary control of the designated states, including those since created out of the territories named, with the right in each to determine for itself to what extent the rule of appropriation or the common-law rule in respect of riparian rights should obtain. For since ‘Congress cannot enforce either rule upon any state,’ Kansas v. Colorado, 206 U. S. 46, 94, the full power of choice must remain with the state. The Desert Land Act does not bind or purport to bind the states to any policy. It simply recognizes and gives sanction, in so far as the United States and its future grantees are concerned, to the state and local doctrine of appropriation, and seeks to remove what otherwise might be an impediment to its full and successful operation. See Wyoming v. Colorado, 259 U. S. 419, 465.” Id., at 163-164.
See also Gutierres v. Albuquerque Land & Irrig. Co., 188 U. S. 545, 552-553 (1903); Ickes v. Fox, 300 U. S. 82, 95 (1937) ; Brush v. Commissioner, 300 U. S. 352, 367 (1937).
[659] Congress next addressed the task of reclaiming the arid lands of the West 11 years later. The opening of the arid lands to homesteading raised the specter that settlers might claim lands more suitable for reservoir sites or other irrigation works, impeding future reclamation efforts. Congress addressed this problem in the Act of Oct. 2, 1888, 25 Stat. 527, which provided:
“[A] 11 the lands which may hereafter be designated or selected by such United States surveys for sites for reservoirs, ditches or canals for irrigation purposes and all the lands made susceptible of irrigation by such reservoirs, ditches or canals are from this time henceforth hereby reserved from sale as the property of the United States, and shall not be subject after the passage of this act, to entry, settlement or occupation until further provided by law.”
Unfortunately, this language, which had been hastily drafted and passed, had the practical effect of reserving all of the public lands in the West from settlement.13 As a result, “there came a perfect storm of indignation from the people of the West, which resulted in the prompt repeal of the extraordinary [1888] provision.” 29 Cong. Rec. 1955 (1897) (statement of Cong. McRae). In the Act of Aug. 30, 1890, 26 Stat. 391, Congress repealed the 1888 provision except insofar as it reserved reservoir sites. Then, in the Act of Mar. 3, 1891, 26 Stat. 1101, as amended, 43 U. S. C. § 946, Congress provided for rights-of-way across the public lands to be used by “any canal or ditch company formed for the purpose of irrigation.” The apparent purpose of the 1890 and 1891 Acts was to reserve reservoir sites from settlement but to open them for use in reclamation projects.14 As before, Congress expressly indi[660] cated that the reclamation would be controlled by state water law:15
“[T]he right of way through the public lands and reservations of the United States is hereby granted ... for the purpose of irrigation ... , to the extent of the ground occupied by the water of the reservoir and of the canal and its laterals . . . ; Provided, That . . . the privilege herein granted shall not be construed to interfere with the control of water for irrigation and other purposes under authority of the respective States or Territories.” 26 Stat. 1101 (emphasis added).
The Secretary of the Interior, unfortunately, interpreted the 1890 and 1891 Acts as reserving governmentally surveyed reservoir sites from use rather than for use. Congress rectified this interpretation in the Act of Feb. 26, 1897, ch. 335, 29 Stat. 599, which provided:
“[A] 11 reservoir sites reserved or to be reserved shall be open to use and occupation under the right-of-way Act of March third, eighteen hundred and ninety-one. And any State is hereby authorized to improve and occupy such reservoir sites to the same extent as an individual or [661] private corporation, under such rules and regulations as the Secretary of the Interior may prescribe: Provided, That the charges for water coming in whole or part from reservoir sites used or occupied under the provisions of this Act shall always be subject to the control and regulation of the respective States and Territories in which such reservoirs are in whole or part situate.”
The final provision of the 1897 Act was proposed as a floor amendment by Representative, later Speaker, Cannon to expressly preserve States’ control over reclamation within their borders. It was clearly the opinion of a majority of the Congressmen who spoke on the bill, however, that such an amendment was unnecessary except out of an excess of caution.16 According to Congressman Lacey, Chairman of the House Committee on Public Lands and a principal sponsor of the [662]*6621897 Act, the water through which the reclamation would be accomplished
“does not belong to the [Federal] Government. The reservoirs in which the water is stored belong to the Government, but the water belongs to the States and will be controlled by them. The amendment proposed by the gentleman from Illinois [Mr. Cannon] relieves this measure from all possible doubt upon that subject. I think there could be no doubt anyhow, but this amendment takes away the possibility of any question being raised as to the right of the States and Territories to regulate and control the management and the price of the water.” 29 Cong. Rec. 1952 (1897).
Congressman Lacey’s statement found reflection in contemporaneous decisions of this Court holding that, with limited exceptions not relevant to reclamation, authority over intrastate waterways lies with the States. In United States v. Rio Grande Dam & Irrig. Co., for example, New Mexico’s authority to adopt a prior appropriation system of water rights for the Rio Grande River was challenged. The Court unhesitatingly held that “as to every stream within its dominion a State may change [the] common law rule and permit the appropriation of the flowing waters for such purposes as it deems wise.” 174 U. S., at 702-703. The Court noted that there are two limitations to the State’s exclusive control of its streams — reserved rights “so far at least as may be necessary for the beneficial uses of the government property,” id., at 703, and the navigation servitude. The Court, however, was careful to emphasize with respect to these limitations on the States’ power that, except where the reserved rights or navigation servitude of the United States are invoked, the State has total authority over its internal waters. “Unquestionably the State . . . has a right to appropriate its waters, and the United States may not question such appropriation, unless thereby the navigability of the '[river] be disturbed.” Id., at 709.
[663] Similarly, in Kansas v. Colorado, 206 U. S. 46 (1907), the United States claimed that it had a right in the Arkansas River superior to that of Kansas and Colorado stemming from its power “to control the whole system of the reclamation of arid lands.” The Court disagreed and held that state reclamation law must prevail. The United States, of course, could appropriate water and build projects to reclaim its own public lands. “As to those lands within the limits of the States, at least of the Western States, the National Government is the most considerable owner and has power to dispose of and make all needful rules and regulations respecting its property.” Id., at 92. But federal legislation could not “override state laws in respect to the general subject of reclamation.” Ibid. “[E]ach State has full jurisdiction over the lands within its borders, including the beds of streams and other waters.” Id., at 93. With respect to the question that had been presented in Rio Grande Dam & Irrig. Co., the Court reaffirmed that each State “may determine for itself whether the common law rule in respect to riparian rights or that doctrine which obtains in the arid regions of the West of the appropriation of waters for the purposes of irrigation shall control. Congress cannot enforce either rule upon any State.” 206 U. S., at 94.
Ill
It is against this background that Congress passed the Reclamation Act of 1902. With the help of the 1891 and 1897 Acts, private and state reclamation projects had gone far toward reclaiming the arid lands,17 but massive projects were now needed to complete the goal and these were beyond the means of private companies and the States. In 1900, therefore, all of the major political parties endorsed federal funding of reclamation projects. While the Democratic Party’s platform specified none of the attributes of a federal program other than to recommend that it be “intelligent,” [664] K. Porter & D. Johnson, National Party Platforms 115 (2d ed. 1961), the Republicans specifically recommended that the reclamation program “reserv[e] control of the distribution of water for irrigation to the respective States and territories.” Id., at 123. In his first message to Congress after assuming the Presidency, Theodore Roosevelt continued the cry for national funding of reclamation and again recommended that state law control the distribution of water.18
As a result of the public demand for federal reclamation funding, a bill was introduced into- the 57th Congress to use the money from the sale of public lands in the Western States to build reclamation projects in those same States. The projects would be built on federal land and the actual construction and operation of the projects would be in the hands'of the Secretary of the Interior. But the Act clearly provided that state water law would control in the appropriation and later distribution of the water. As originally introduced, § 8 of the Reclamation Act provided: 19
“[N]othing in this act shall be construed as affecting or intended to affect or to in any way interfere with [665] the laws of any State or Territory relating to the control, appropriation, use, or distribution of water used in irrigation; but State and Territorial laws shall govern and control in the appropriation, use, and distribution of the waters rendered available by the works constructed under the provisions of this act: Provided, That the right to the use of water acquired under the provisions of this act shall be appurtenant to the land irrigated, and beneficial use shall be the basis, the measure, and the limit of the right.”
From the legislative history of the Reclamation Act of 1902, it is clear that state law was expected to control in two important respects. First, and of controlling importance to this case, the Secretary would have to appropriate, purchase, or condemn necessary water rights in strict conformity with state law. According to Representative Mondell, the principal sponsor of the reclamation bill in the House, once the Secretary determined that a reclamation project was feasible and that there was an adequate supply of water for the project, “the Secretary of the Interior would proceed to make the appropriation of the necessary water by giving the notice and complying with the forms of law of the State or Territory in which the works were located.” 35 Cong. Rec. 6678 (1902) (emphasis added). The Secretary of the Interior could not take any action in appropriating the waters of the state streams “which could not be undertaken by an individual or corporation if it were in the position of the Government as regards the ownership of its lands.” H. R. Rep. No. 794, 57th Cong., 1st Sess., 7-8 (1902). Thus, in response to the [666] statement of an opponent to the bill that the Secretary would be allowed to condemn water even if in violation of state law, Representative Mondell briskly responded:
“Whereabouts does the gentleman find any such provision as he is arguing? Whereabouts in the bill is there anything that attempts to give the Federal Government any right to condemn or to take any water right or do anything which an individual could not do? Will the gentleman point out any place or any provision for the Federal Government to do anything that I could not do if I owned the public land?
“Mr. RAY of New York. Do you say there is nothing in this bill that provides for condemnation?
“Mr. MONDELL. The bill provides explicitly that even an appropriation of water can not be made except under State law.” 35 Cong. Rec. 6687 (1902) (emphasis added).20
[667] Second, once the waters were released from the Dam, their distribution to individual landowners would again be controlled by state law. As explained by Senator Clark of Wyoming, one of the principal supporters of the reclamation bill in the Senate, “the control of waters after leaving the reservoirs shall be vested in the States and Territories through which such waters flow.” Id., at 2222. As Senator Clark went on to explain:
“[I]t is right and proper that the various States and Territories should control in the distribution. The conditions in each and every State and Territory are different. What would be applicable in one locality is totally and absolutely inapplicable in another. ... In each and every one of the States and Territories affected, after a long series of experiments, after a due consideration of conditions, there has arisen a set of men who are especially qualified to deal with local conditions.
“Every one of these States and Territories has an accomplished and experienced corps of engineers who for years have devoted their energies and their learning to a solution of this problem of irrigation in their individual localities. To take from these experienced men, to take from the legislatures of the various States and Territories, the control of this question at the present time would be something little less than suicidal. They are the men qualified to deal with the question, the laws are written upon their statute books and read of all men, and in every one of these States and Territories the laws have been passed that most diligently regard the rights of the settler and of the farmer . . . .” Ibid.
As Representative Sutherland, later to be a Justice of this Court, succinctly put it, “if the appropriation and use were not under the provisions of the State law the utmost confusion would prevail.” Id., at 6770. Different water rights in [668] the same State would be governed by different laws and would frequently conflict.21
A principal motivating factor behind Congress’ decision to [669] defer to state law was thus the legal confusion that would arise if federal water law and state water law reigned side by side in the same locality. Congress also intended to “folio [w] the well-established precedent in national legislation of recognizing local and State laws relative to the appropriation and distribution of water.” Id., at 6678 (Cong. Mondell). As Representative Mondell noted after reviewing the legislation discussed in Part II of this opinion: “Every act since that of April 26, 1866, has recognized local laws and customs appertaining to the appropriation and distribution of water used in irrigation, and it has been deemed wise to continue our policy in this regard.” Id., at 6679.22
Both sponsors and opponents of the Reclamation Act also expressed constitutional doubts as to Congress' power to override the States’ regulation of waters within their borders. Congress was fully aware that the Supreme Court had “in [670] several decisions recognized the right of the State to regulate and control the use of water within its borders.” Ibid. (Cong. Mondell). According to the House Report, “Section 8 recognizes State control over waters of nonnavigable streams such as are used in irrigation.” H. R. Rep. No. 794, 57th Cong., 1st Sess., 6 (1902) (emphasis added).23
IV
For almost half a century, this congressionaily mandated division between federal and state authority worked smoothly. No project was constructed without the approval of the Secretary of the Interior, and the United States through this official preserved its authority to determine how federal- funds should be expended. But state laws relating to water rights were observed in accordance with the congressional directive contained in § 8 of the Act of 1902. In 1958, however, the first of two cases was decided by this Court in which private landowners or municipal corporations contended that state water law had the effect of overriding specific congressional directives to the Secretary of the Interior as to the operation of federal reclamation projects. In Ivanhoe Irrigation District v. McCracken, 357 U. S. 275, the Supreme Court of California decided that [671] California law forbade the 160-acre limitation on irrigation water deliveries expressly written into § 5 of the Reclamation Act of 1902, and that therefore, under § 8 of the Reclamation Act, the Secretary was required to deliver reclamation water without regard to the acreage limitation. Both the State of California and the United States appealed from this judgment, and this Court reversed it, saying:
“Section 5 is a specific and mandatory prerequisite laid down by the Congress as binding in the operation of reclamation projects, providing that ‘[n]o right to the use of water . . . shall be sold for a tract exceeding one hundred and sixty acres to any one landowner . . . .’ Without passing generally on the coverage of § 8 in the delicate area of federal-state relations in the irrigation field, we do not believe that the Congress intended § 8 to override the repeatedly reaffirmed national policy of § 5.” 357 U. S., at 291-292.
Five years later, in City of Fresno v. California, 372 U. S. 627 (1963), this Court affirmed a decision of the United States Court of Appeals for the Ninth Circuit holding that § 8 did not require the Secretary of the Interior to ignore explicit congressional provisions preferring irrigation use over domestic and municipal use.24
[672] Petitioners do not ask us to overrule these holdings, nor are we presently inclined to do so.25 Petitioners instead ask us to hold that a State may impose any condition on the “control, appropriation, use, or distribution of water” through a federal reclamation project that is not inconsistent with clear congressional directives respecting the project. Petitioners concede, and the Government relies upon, dicta in our cases that may point to a contrary conclusion. Thus, in Ivanhoe, the Court went beyond the actual facts of that case and stated:
“As we read § 8, it merely requires the United States to comply with state law when, in the construction and operation of a reclamation project, it becomes necessary for it to acquire water rights or vested interests therein. . . . We read nothing in § 8 that compels the [673] United States to deliver water on conditions imposed by the State.” 357 U. S., at 291-292.
Like dictum was repeated in City of Fresno, supra, at 630, and in this Court’s opinion in Arizona v. California, 373 U. S. 546 (1963), where the Court also said:
“The argument that § 8 of the Reclamation Act requires the United States in the delivery of water to follow priorities laid down by state law has already been disposed of by this Court in Ivanhoe Irr. Dist. v. McCracken, . . . and reaffirmed in City of Fresno v. California .... Since § 8 of the Reclamation Act did not subject the Secretary to state law in disposing of water in [Ivanhoe], we cannot, consistently with Ivanhoe, hold that the Secretary must be bound by state law in disposing of water under the Project Act.” Id., at 586-587.
While we are not convinced that the above language is diametrically inconsistent with the position of petitioners,26 or that it squarely supports the United States, it undoubtedly goes further than was necessary to decide the cases presented to the Court. Ivanhoe and City of Fresno involved conflicts between § 8, requiring the Secretary to follow state law as to water rights, and other provisions of Reclamation Acts that placed specific limitations on how the water was to be distributed. Here the United States contends that it may ignore state law even if no explicit congressional directive conflicts with the conditions imposed by the California State Water Control Board.27
[674] In Arizona v. California, the States had asked the Court to rule that state law would control in the distribution of water from the Boulder Canyon Project, a massive multistate reclamation project on the Colorado River.28 After reviewing the legislative history of the Boulder Canyon Project Act, 43 U. S. C. § 617 et seq., the Court concluded that because of the unique size and multistate scope of the Project, Congress did not intend the States to interfere with the Secretary’s power to determine with whom and on what terms water contracts would be made.29 While the Court in rejecting the States’ claim repeated the language from Ivanhoe and City of Fresno as to the scope of § 8, there was no need for it to reaffirm such language except as it related to the singular legislative history of the Boulder Canyon Project Act.
But because there is at least tension between the above-quoted dictum and what we conceive to be the correct reading of § 8 of the Reclamation Act of 1902, we disavow the dictum to the extent that it would prevent petitioners from imposing conditions on the permit granted to the United States which are not inconsistent with congressional provisions authorizing the project in question. Section 8 cannot be read to require the Secretary to comply with state law only when it becomes necessary to purchase or condemn vested water rights. That [675] section does, of course, provide for the protection of vested water rights, but it also requires the Secretary to comply with state law in the “control, appropriation, use, or distribution of water.” Nor, as the United States contends, does § 8 merely require the Secretary of the Interior to file a notice with the State of his intent to appropriate but to thereafter ignore the substantive provisions of state law. The legislative history of the Reclamation Act of 1902 makes it abundantly clear that Congress intended to defer to the substance, as well as the form, of state water law. The Government’s interpretation would trivialize the broad language and purpose of §8.
Indeed, until recently, it has been the consistent position of the Secretary of the Interior and the Bureau of Reclamation, who are together responsible for executing the provisions of the Reclamation Act of 1902, that in appropriating water for reclamation purposes the Bureau must comply with state law. The Bureau’s operating instructions, for example, provide:
“State and Federal law and policy establish the framework for project formulation. Project 'plans must comply with State legal provisions or priorities for beneficial use of water .... In some cases, . . . State laws . . . have been modified to meet specific conditions in the authorization of particular projects.” U. S. Department of Interior, Bureau of Reclamation, Reclamation Instructions § 116.3.1 (1959) (emphasis added).
"The Reclamation Act recognizes the interests and rights of the States in the utilization and control of their water resources and requires the Bureau, in carrying out provisions of the Act, to proceed in conformity with State water laws. Since the construction of a reservoir and the subsequent storage and release of water for beneficial purposes normally entails stream regulation, it is necessary to reach an understanding with the States regarding [676] reservoir operating limitations.” Id., § 231.5.1 (1957) (emphasis added).
With respect to the Central Valley Project, the Bureau advised Congress that “ '[reclamation law . . . recognizes State water law and rights thereunder’ ” and that “Bureau filings on water are subject to State approval.” 95 Cong. Rec. A961 (1949).30
Indeed, until the unnecessarily broad language of the Court’s opinion in Ivanhoe, both the uniform practice of the Bureau of Reclamation and the opinions of the Court clearly supported petitioners’ argument that they may impose any condition not inconsistent with congressional directive. In holding that the United States was not an indispensable party in Nebraska v. Wyoming, 295 U. S. 40 (1935), this Court observed:
“[T]he Secretary of the Interior, pursuant to the [1902] Act, applied to the state engineer of Wyoming and obtained from him permission ... to appropriate waters, and was awarded a priority date. . . . All of the acts of the Reclamation Bureau in operating the reservoirs so as to impound and release waters of the river are subject to the authority of Wyoming.
“The bill alleges, and we know as matter of law [citing § 8 of the 1902 Reclamation Act], that the Secretary and his agents, acting by authority of the Reclamation Act and supplementary legislation, must obtain permits and priorities for the use of water from the State of Wyoming [677] in the same manner as a private appropriator or an irrigation district formed under the state law.” Id., at 42-43.
Ten years later, in its final decision in Nebraska v. Wyoming, 325 U. S. 589 (1945), the Court elaborated on its original observation:
“All of these steps make plain that [the Reclamation] projects were designed, constructed and completed according to the pattern of state law as provided in the Reclamation Act. We can say here what was said in Ickes v. Fox, [300 U. S. 82 (1937)]: ‘Although the government diverted, stored and distributed the water, the contention of petitioner that thereby ownership of the water or water-rights became vested in the United States is not well founded. Appropriation was made not for the use of the government, but, under the Reclamation Act, for the use of the land owners; and by the terms of the law and of the contract already referred to, the water-rights became the property of the land owners, wholly distinct from the property right of the government in the irrigation works. . . . The government was and remained simply a carrier and distributor of the water . . . , with the right to receive the sums stipulated in the contracts as reimbursement for the cost of construction and annual charges for operation and maintenance of the works.’
“We have then a direction by Congress to the Secretary of the Interior to proceed in conformity with state laws in appropriating water for irrigation purposes. We have a compliance with that direction. . . .” Id., at 613-615.
The United States suggests that, even if the Congress of 1902 intended the Secretary of the Interior to comply with state law, more recent legislative enactments have subjected reclamation projects “to a variety of federal policies that leave no room for state controls on the operation of a project or on [678] the choice of uses it will serve.” 31 Brief for United States 89. While later Congresses have indeed issued new directives to the Secretary, they have consistently reaffirmed that the Secretary should follow state law in all respects not directly inconsistent with these directives. The Flood Control Act of 1944, 58 Stat. 888, for example, which first authorized the New Melones Dam, provides that it is the “policy of the Congress to recognize the interests and rights of the States in determining the development of watersheds within their borders and likewise their interests and rights in water utilization and control.” Perhaps the most eloquent expression of the need to observe state water law is found in the Senate Report on the McCarran Amendment, 43 U. S. C. § 666 (a), which subjects the United States to state-court jurisdiction for general stream adjudications:
“In the arid Western States, for more than 80 years, the law has been the water above and beneath the surface of the ground belongs to the public, and the right to the use thereof is to be acquired from the State in which it is found, which State is vested with the primary control thereof.
“Since it is clear that the States have the control of water within their boundaries, it is essential that each and every owner along a given water course, including the United States, must be amenable to the law of the State, [679] if there is to be a proper administration of the water law as it has developed over the years.” S. Rep. No. 755, 82d Cong., 1st Sess., 3, 6 (1951).
V
Because the District Court and the Court of Appeals both held that California could not impose any conditions whatever on the United States’ appropriation permit, those courts did not reach the United States’ alternative contention that the conditions actually imposed are inconsistent with congressional directives as to the New Melones Dam. Nor did they reach California’s contention that the United States is barred by principles of collateral estoppel from challenging the consistency of the permit conditions. Assuming, arguendo, that the United States is still free to challenge the consistency of the conditions, resolution of their consistency may well require additional factfinding. We therefore reverse the judgment of the Court of Appeals and remand for further proceedings consistent with this opinion.
Reversed and remanded.