Arizona v. California

delivered the opinion of the Court.

In 1952 the State of Arizona invoked the' original jurisdiction of this Court1 by filing a complaint against' the *551State of California and seven of its public agencies.2 Later, Nevada, New Mexico, Utah, and the United States; were added as parties either voluntarily or on motion.3 The basic controversy in the case is over how much water each State has a legal right to use out of the waters of the Colorado River and its tributaries. After preliminary pleadings, we referred the case to ■ George I. Haight; Esquire, and upon his death in 1955 to Simon H. Rif kind,. Esquire, as Special Master to take evidence, find facts, state- conclusions of law, and recommend a decree, all “subject to consideration, revision, or approval by the Court.”4 The Master conducted a trial lasting from June 14, 1956, to August 28, 1958, during which 340 witnesses were heard orally or by deposition, thousands of exhibits were received, and 25,000 pages of transcript were filled. Following many motions, arguments, and briefs, the Master in a 433-page volume reported his findings, conclusions, and recomménded decree, received by the Court on January 16,1961.5 The case has been extensively briefed here and orally argued twice, the first time about 16 hours, the second, over six. As we see this case, the question of each State’s share of the waters of the Colorado and its tributaries turns on the meaning and the scope of the Boulder Canyon Project Act passed by Congress in *5521928.6 That meaning and scope can be better understood when the Act is set against its background — the gravity of. the Southwest's water problems; the inability of local groups or individual States to deal with these enormous problems; the' continued failure of the States to agree on how to conserve and divide the waters; and the ultimate action by Congress at the request of the States creating a .-great system of dams and public works nationally built, controlled, and operated for the purpose of conserving and distributing the' water.

The Colorado River itself rises in the mountains of Colorado and flows generally in a southwesterly direction for about 1,300 miles through Colorado, Utah, and Arizona and along the Arizona-Nevadá and Arizona-California boundaries, after which it passes into Mexico and empties into the Mexican waters of the Gulf of California. On its way to the sea it receives tributary waters from Wyoming, Colorado, Utah, Nevada, New Mexico, and Arizona. The' river and its tributaries flow in a natural basin almost surrounded by large mountain ranges and drain 242,000 square miles, an area about 900 miles long from north to south and 300 to 500 miles wide from east to west — practically one-twelfth the area of the continental United States excluding Alaska. Much of this large basin is so arid that it is, as it always has been, largely dependent upon managed use of the.waters of the Colorado River System to make it productive and inhabitable. The Master refers to archaeological evidence .that as long as 2,000 years ago the ancient Hohokam tribe built and maintained irrigation canals near what is now Phoenix, Arizona, and that American Indians were practicing irrigation in that region at the time white men first explored it. In the second half of the nineteenth century a group *553of people interested in California’s Imperial Valley conceived plans to divert water from the mainstream of the Colorado to give life and growth to the parched and barren soil of that valley. As the most feasible route was through Mexico, a Mexican corporation was formed and a canal dug partly in Mexico and partly in the United States. Difficulties which arose because the canal was subject to the sovereignty of both countries generated hopes in this country that some day there would be a canal wholly within the United States, an all-American canal.7

During the latter part of the nineteenth and the first part of the twentieth centuries, people in the Southwest continued to seek new ways to satisfy their water needs, which by that time were increasing rapidly/as new settlers moved into this fast-developing region. ,But none of the more or less primitive diversions made from the mainstream of the Colorado conserved enough water to meet the growing needs of the basin. The natural flow of the Colorado was too erratic', the river at many places in canyons too deep, and the engineering and economic hurdles too great for small farmers, larger groups, or even States to build storage dams, construct canals, and install the expensive works necessary for a dependable year-round water supply. Nor were droughts the basin’s only problem; spring floods due to melting snows and seasonal storms were a recurring menace, especially disastrous in California’s Imperial Valley where, even after the Mexican canal provided a more dependable water supply, the threat of flood remained at least as serious as before.. Another troublesome problem was the erosion of land' and the deposit of silt which fouled waters, choked irrigation works, and damaged good farmland and crops.

*554It is not surprising that the pressing necessity to transform the erratic and often destructive flow of the Colorado River into a controlled and dependable water supply desperately needed in so many States began tó be talked about and recognized as far more than a purely -local problem which could be solved on a farmer-by-farmer, group-by-group, or even state-by-state basis, desirable as this kind of solution might have been.' The inadequacy of a local solution was recognized in the Report of the All-American Canal Boarc] of the United' States Department of the Interior on July 22, 1919, which detailed the widespread benefits that could be expected from construction by the United States of a large reservoir on the mainstream of the Colorado and an all-American canal to the Imperial Valley.8 Some months later, May 18, 1920, Congress passed a bill offered by Congressman Kinkaid of. Nebraska directing the Secretary of the Interior to make a study and report of diversions which might be made from the Colorado River for irrigation in the Imperial Valley.9 The Fall-Davis Report,10 submitted to Congress in compliance .with the Kinkaid Act, began by declaring, “The control of the floods and' development of the resources of the Colorado River are peculiarly national problems . . .”11 and then went on to give reasons why this was so, concluding with the statement that the job was so big that only the Federal Government could do it.12 Quite naturally, .therefore, the *555Report recommended that the United States construct as a government project not only an alLAmerican canal from the Colorado River to the Imperial Valley but also a dam and reservoir at or near Boulder Canyon.13

The prospect that the United States .would undertake to build as a national project the necessary works to control floods and store river -waters for irrigation was apparently a welcome one for the basin States. But it brought to life strong fears in the northern basin States that additional waters made available by the storage and canal projects might be gobbled up in perpetuity by faster growing lower basin areas, particularly California, before the upper States could appropriate what they believed to be their fair share. These fears were not without foundation,. since the law of prior appropriation prevailed in most of the Western States,14 Under that law the One who first appropriates water and puts it to beneficial use thereby acquires a vested right to continue to divert and use that quantity of water against, all claimants junior to him in point of time.15 “First in time, first in right” is the shorthand expression of this legal principle. In 1922, only four months after the Fall-Davis Report, this Court in Wyoming v. Colorado, 259 U. S. 419, held that the *556doctrine of prior appropriation could be given interstate effect.16 This decision intensified fears of Upper Basin States that they would not get their fair share of Colorado River water.17 In view of California’s '.phenomenal growth, the Upper Basin States had particular reason to fear that California, by appropriating and. using Colorado River water before the upper States, would', under the interstate application of the prior appropriation doctrine, be “first in time” and therefore “first in right.” ' Nor were such fears limited to the northernmost States. Nevada, Utah, and especially Arizona .were all apprehensive that California’s rapid declaration of appropriative claims would deprive them of their just share of basin water available after construction of the proposed United States project. It seemed for a time that these fears would keep the States from agreeing- on any kind of division of the river waters. Hoping to prevent “conflicts” and “expensive litigation” which would hold up or prevent the tremendous benefits expected from extensive federal development of the river,18 the basin States requested and Congress passed an Act on August 19, 1921,- giving the *557States consent to negotiate and enter into a compact for the “equitable division and apportionment ... of the water supply of the Colorado River.” 19

Pursuant to -this congressional authority, the seven States appointed Commissioners who, after negotiating for the better part of a year, reached an agreement at Santa Fe, New Mexico, on November 24, 1922. The ágreement, known as the Colorado River Compact,20 failed to fulfill the hope of Congress that the States would themselves agree on each State’s share of the water. The most the Commissioners were able to accomplish in the Compact was to adopt a compromise suggestion of Secretary of Commerce Herbert Hoovér, specially designated as United States representative.21 This, compromise divides the entire basin into two parts, the Upper Basin and the Lower Basin, separated at a point on the river in northern Arizona known as Lee Ferry. (A map showing the two basins and other points of interest in this controversy is printed as an Appendix facing p./602.) Article III (a) of the Compact apportions to each basin in perpetuity-7,500,000 acre-feet of water 22 a year from the Colorado River System, defined in Article II (a) as “the Colorado River and its tributaries within' the United States of America.” In addition, Article III (b) gives the Lower Basin “the right to increase its beneficial consumptive use23 of such waters by one million acre-féet per annum.” Article III.(c) provides that future Mex*558ican water rights recognized by the United States shall be supplied first out of surplus over and above the aggregate of the quantities specified in (a) and (b), and if this surplus is not enough the deficiency shall be borne equally by the two basins. Article III (d) requires the Upper Basin not to deplete the Lee Ferry flow below an aggregate- of 75,000,000 acre-feet for any 10 consecutive years. Article III (f) and (g) provide a way for further apportionment by a compact of “Colorado River System” waters at any time after October 1, 1963. While these allocations quieted rivalries between the Upper and Lower Basins, major differences between the States in the Lower Basin continued. Failure of the Compact to determine each State’s share of the water left Nevada and Arizona with their fears that the law of prior appropriation would be not a protection but a menace because California-could use that law to get for herself the lion’s share of the waters allotted to the Lower Basin. Moreover, Arizona, because of her particularly strong interest in the Gila, intensely resented the Compact’s inclusion of the Colorado River tributaries in its allocation scheme and was bitterly hostile to having Arizona tributaries,' again particularly the Gila, forced to contribute to the Mexican burden. Largely for these reasons, Arizona alone, of all the States in both basins, refused to ratify the Compact.24

Seeking means which would permit ratification by all seven basin States, the Governors of those States met at Denver in 1925 and again in 1927. As a result of these meetings the Governors of the upper States suggested, as a fair apportionment of water among the Lower Basin States, that out of the average annual delivery of water at *559Lee Ferry required by the Compact — 7,500,000 acre-feet— Nevada be given 300,000 acre-feet, Arizona 3,000,000, and California 4,200,000, and that unapportioned waters, subject to reapportionment after 1963, be shared equally by Arizona and California. Each Lower Basin State would have “the exclusive beneficial consumptive use of such tributaries within its boundaries before the same empty into thé main stream,” except that Arizona tributary waters in excess of '1,000,000 acre-feet could under some circumstances be subject to diminution by reason of a United States treaty with Mexico. This proposal foundered because California held out for 4,600,000 acre-feet instead of 4,200,000 25 and because Arizona held out for complete exemption of its tributaries from any part of the Mexican burden.26

Between 1922 and 1927 Congressman Philip Swing and Senator Hiram Johnson, both of California, made three attempts to have Swing-Johnson bills enacted, authorizing construction of a dam in the canyon section of the Colorado River and an all-American canal.27 These bills would have carried put the original Fall-Davis Report’s recommendations that the river problem be recognized and treated as national, not local. Arizona’s Senators and Congressmen, still insisting upon a definite guaranty of water from the. mainstream,-, bitterly fought these proposals because they failed to provide for exclusive use of her own tributaries, particularly the Gila, and for exemption of these tributaries from the Mexican burden.

*560Finally, the fourth Swing-Johnson bill passed both Houses and became the Boulder Canyon Project Act of December 21, 1928, 45 Stat. 1057. The Act authorized the Secretary of the Interior to construct, operate, and maintain a dam and other works in order to control floods, improve navigation, regulate the river’s flow, store and distribute waters for reclamation and other beneficial uses, and generate electrical power.28 The projects authorized by the Act were the same as those provided for in the prior defeated measures, but in other significant respects the Act was strikingly different. The earlier bills •had offered no method whatever of apportioning the waiters among the States of the Lower Basin. The Act as finally passed did provide such a method, and, as we view it, the method chosen was a complete statutory apportionment intended to put an end to the long-standing dispute over Colorado River waters. To protect the Upper Basin against California should Arizona still refuse to ratify the Compact,29 § 4 (a) of the Act as finally passed provided that, if fewer than seven States ratified within six months, the Act should not take effect unless six States including California ratified and unless California, by its legislature, agreed “irrevocably and unconditionally . . . as an express covenant” to a limit on its annual consumption of Colorado River water of “four million four hundred thousand acre-feet of the waters apportioned to the lower *561basin States by paragraph (a) of Article III of the Colorado River compact, plus not more than one-half of any excess or surplus waters unapportioned by said compact.” Congress in the same section showed its continuing desire to have California, Arizona, and Nevada settle their own differences by authorizing them to make an agreement apportioning to Nevada 300,000 acre-feet, and to Arizona 2,800,000 acre-feet plus half of any surplus waters unap-portioned by the Compact. The permitted agreement also was to allow Arizona exclusive use of the Gila River, wholly free from any Mexican obligation, a. position Arizona had taken from the beginning. Sections-5 and 8 (b) of the Project Act made provisions for the sale of the stored waters. The Secretary of the Interior was authorized by § 5 “under such general regulations as he may prescribe, to contract for the storage of water in said reservoir and for the delivery thereof at such points on the river and on said canal as may be agreed upon, for irrigation and domestic uses . . . .” Section 5 required these contracts to be “for permanent service” and further provided, “No person shall have or be entitled to have the use for any purpose of the water stored as aforesaid except by contract made as herein stated.” Section 8 (b) provided that the Secretary’s contracts would be subject to any compact dividing the benefits of the water between Arizona, California, and Nevada, or any two of them, approved by Congress on or before January 1, 1929, but that any such compact approved after that date should be “subject to all contracts, if any, made by the Secretary of the Interior under section 5 hereof prior to the date of such approval and consent by Congress.”

The Project Act became effective on June 25, 1929, by Presidential Proclamation,30 after six States, including California, had ratified the Colorado River Compact and *562the California legislature had accepted the limitation of 4,400,000 acre-feet31 as required by the Act. Neither the three States nor any two of them ever entered into any apportionment compact as authorized by §§ 4 (a) and 8 (b). After the construction of Boulder Dam the Secretary of the Interior, purporting to act under the authority of the Project Act, made contracts with various water users in California for 5,362,000 acre-feet, with Nevada for 300,000 acre-feet, and with Arizona for 2,800,000 acre-feet of water from that stored at Lake Mead.

The Special Master appointed by this Court found that the Colorado River Compact, the law of prior appropriation, and the doctrine of equitable apportionment — by which doctrine' this Court in the absence of statute resolves interstate claims according to the equities — do not control the issues in this case. The Master concluded that, since the Lower Basin States had failed to make a corppact to allocate the waters among themselves as authorized by §§ 4 (a) and 8 (b), the Secretary’s contracts with the States had within the statutory scheme of §§ 4 (a), 5, and 8 (b) effected an apportionment of the waters of the mainstream which, according to the Master, were the only waters to be apportioned under the Act. The Master further held • that, in the event of a shortage of water making it impossible for the Secretary to supply all the water due California, Arizona, and Nevada under their contracts, the burden of the shortage must be borne by each State in proportion to her share of the first 7,500,000 acre-feet allocated to the Lower Basin, that is, — by California, — by Arizona, and by Nevada, without regard to the law of prior appropriation.

Arizona, Nevada, and the United States support with. few exceptions the analysis, conclusions, and becommen-*563dations of the Special Master’s report. These parties agree that Congress did not leave division of the waters to an equitable apportionment by this Court but instead created a comprehensive statutory scheme for the allocation of mainstream waters. Arizona, however, believes that the allocation formula established by the Secretary’s contracts was in fact the formula required by the Act. The United States, along with California, thinks the Master should not have invalidated the provisions of the Arizona and Nevada water contracts requiring those States to deduct from their allocations any diversions of water above Lake Mead which reduce the flow into that lake.

California is in basic disagreement with almost all of the Master’s Report. She argues that the Project Act, like the Colorado River Compact, deals with the entire Colorado River System, not just the mainstream. This would mean that diversions within Arizona and Nevada of tributary waters flowing in those States would be charged against their apportionments and that, because tributary water would be added to the mainstream water in computing the first 7,500,000 acre-feet available to the States, there would be a greater likelihood of a surplus, of which California gets one-half. The result of California’s argument would be much more water for California and much less for Arizona. California also argues that the Act neither allocates the Colorado River waters nor gives the Secretary authority to make an allocation. Rather she takes the position that the judicial’doctrine of equitable apportionment giving full interstate effect to the traditional western water law of prior appropriation should determine the rights of the parties to the water. Finally, California claims that in any event the Act does not control in time of shortage. Under such circumstances, she says, this Court should divide the waters according to the doctrine of equitable apportionment or *564the law of prior appropriation, either of which, she argues, should result in protecting her prior uses.

Our jurisdiction to entertain this suit is not challenged and could not well be since Art. Ill, § 2, of the Constitution gives this Court original jurisdiction of actions in which States are parties. In exercising that jurisdiction, we are mindful of this Court’s often expressed preference that, where possible, States settle their controversies by “mutual accommodation and agreement.” 32 Those cases and others33 make it clear, however, that this Court does have a serious responsibility to adjudicate cases where there are actual, existing controversies over how interstate streams should be apportioned among States. This case is the most recent phase of a continuing controversy over the water of the Colorado River, which the States despite repeated efforts have been unable to settle. Resolution of this dispute’requires a determination of what apportionment, if any, is made by the Project Act and what powers are conferred by the Act upon the Secretary of the Interior. Unless many of the issues presented here are adjudicated, the conflicting claims of the parties will continue, as they do now, to raise serious doubts as to the extent of each State’s right to appropriate water from the Colorado River System for existing or new uses. In this situation we should and do exercise our jurisdiction.

I.

Allocation of Water Among the States and Distribution to Users.

iWe have concluded, for reasons to be stated, that Congress in passing the Project Act intended to and did *565create its own comprehensive scheme for. the apportionment among California, Arizona, and Nevada of the Lower Basin’s share of the mainstream waters of the Colorado River, leaving each State its tributaries. Congress decided that a fair division of the first 7,500,000 acre-feet of’ such mainstream waters would give 4,40.0,000 acre-feet to California, 2,800,000 to Arizona, and 300,000 to Nevada; Arizona and California would each get one-half of any surplus. Prior approval was therefore given in the Act for a tri-state compact to incorporate these terms. The States, subject to subsequent congressional approval, were also permitted to agree on a compact with different terms. Division of the water did not, however, depend on the States’ agreeing to a compact, for Congress gave the Secretary of the Interior adequate authority to accomplish the division. Congress did this by giving the Secretary power to make contracts for the delivery of water and by providing that no person could have water without a contract.

A. Relevancy of Judicial Apportionment and Colorado River Compact. — We agree’ with the Master that apportionment of the Lower Basin waters of the Colorado River is- not controlled by the doctrine of equitable apportionment or by the Colorado River Compact. It is true that the Court has used the doctrine of equitable apportionment to decide river controversies between States.34 But in those cases Congress had not made any statutory apportionment. In this case, we have decided that Congress has provided its own method for allocating among the Lower Basin States the mainstream water to which they are entitled under the Compact. Where Congress has so exercised its constitutional power over waters, courts have no power to substitute their own notions of an “equitable apportionment” for the apportionment chosen by Con*566gress. Nor does the Colorado River Compact control this case. Nothing in that Compact purports to divide water among the Lower Basin States nor in any way to affect or control any future apportionment among those States or any distribution of water within a State. That the Commissioners were able to accomplish even a division of water between the basins is due to what is generally known as the “Hoover Compromise.”

“Participants [in the Compact negotiations] have stated that the negotiations would have broken up but for Mr. Hoover’s proposal: that the Commission limit its efforts to a division of water between the upper basin and the lower basin, leaving to each basin the future internal allocation of its share.” 35

And in fact this is all the Compact did. However, the Project Act, by referring to the Compact in several places, does make the Compact relevant to a limited extent. To begin with, the Act explicitly approves the Compact and thereby fixes a division of the waters between the basins which must be respected. Further, in several places the Act refers to terms contained in the Compact. For example, § 12 of the Act adopts the Compact definition of “domestic,” 36 and § 6 requires satisfaction of “present' perfected rights” as used in the Compact.37 Obviously, therefore, those particular terms, though originally formulated only for the Compact’s allocation of water between basins, are incorporated into the Act and are made applicable to the Project Act’s allocation among Lower Basin *567States. The Act also declares that' the Secretary of the Interior and the United States in the construction, operation, and maintenance of the dam and other works and in the making of contracts shall be subject to and controlled by the Colorado River Compact.38 These latter references to the Compact are quite different from the Act’s adoption of Compact terms. Such references, unlike the explicit adoption of terms, were, used only to show that the Act and its provisions were in no way to upset, alter, or affect the Compact’s congressionally approved division of water between the basins. They were not intended to make the Compact and its provisions control or affect the Act’s allocation among and distribution of water within the States of the Lower Basin. Therefore, we look to the Compact for terms specifically incorporated in the Act, and we would also look to it to resolve disputes between the Upper and Lower Basins, were any involved in this case. But no such questions are here. We must determine what apportionment and delivery scheme in the Lower Basin has been effected through the Secretary’s contracts. For that determination, we look to the Project Act alone.

B. Mainstream Apportionment. — The congressional scheme of apportionment cannot be understood without knowing what water Congress wanted apportioned. Under California’s view, which we reject, the first 7,500,000 acre-feet of Lower Basin water, of which California has agreed to use only 4,400,000, is made up of both mainstream and tributary water, not just mainstream water. Under the view of Arizona, Nevada, and the United States, with which we agree, the tributaries are not included in the waters to be divided but remain for the exclusive use of each State. Assuming 7,500,000 acre-*568feet or more in the mainstreám and 2,000,000 in the tributaries, California would get 1,000,000 acre-feet more if the tributaries are included and Arizona 1,000,000 less.39

California’s argument that the Project Act, like the Colorado River Compact, deals with the main river and all its tributaries rests on § 4 (a) of the Act, which limits California to 4,400,000 acre-feet “of the waters apportioned to the lower basin States by paragraph (a) of Article III of the Colorado River compact, plus not more than one-half of any excess or surplus waters unappor-tioned by said compact . . . .” And Article III (a), referred to by § 4 (a), apportioned in perpetuity to the Lower Basin the use of 7,500,000 acre-feet of water per annum “from the Colorado River System,” which was defined in the Compact as “that portion of the Colorado River and its tributaries within the United States of America.”

Arizona argues that the Compact apportions between basins only the waters of the mainstream, not the mainstream and the tributaries. We need not reach that question, however, for we have concluded that whatever waters the Compact apportioned the Project Act itself déalt only with water of the mainstream. In the first place, the Act, in § 4 (a), states that the California limitation, which is in reality her share of the first 7,500,000 acre-feet of Lower Basin water, is on “water of and from the Colorado River,” not of and from the “Colorado River System.” But more importantly, the negotiations among the States and the congressional debates leading to the passage of the Project Act clearly show that the language used by Congress in the Act was meant to refer to mainstream waters only. Inclusion qf the tributaries in the Compact was natural in view of the upper States’ strong feeling that the Lower Basin *569tributaries should be made to share the burden of any obligation to deliver water to Mexico which a future treaty might impose.. But when it came to an apportionment among the Lower Basin States, the Gila, by far the most important Lower Basin tributary, would not logically be included, since Arizona alone of the States could effectively use that river.40 Therefore, with minor exceptions, the proposals and counterproposals over the years, culminating in the Project Act, consistently provided for division of the mainstream only, reserving the tributaries to each State’s exclusive use.

The most important negotiations among the States, which in fact formed the basis of the debates leading to passage of the Act, took place in 1927 when the Governors of the seven basin States met at Denver in an effort to work out an allocation- of the Lower Basin waters acceptable to Arizona, California, and Nevada. Arizona and California made proposals,41 both of which suggested giving Nevada 300,000 acre-feet out of the mainstream of the Colorado River and reserving to each State the exclusive use of her own tributaries. Arizona proposed that all remaining mainstream water be divided equally between herself and California, which would, give each State 3,600,000 acre-feet out of the first 7,500,000 acre-feet of mainstream water. California rejected the proposed ' equal division of the water, suggesting figures that would result in her getting about 4,600,000 out of the 7,500,000. The Governors of the four Upper Basin States, trying to bring Arizona and California together, asked each State to reduce its demands and suggested this compromise: Nevada 300,000 acre-feet, Arizona 3,000,000,.and California *5704,200,000.42 These allocations were to come only out of the mainstream, that is, as stated by the Governors, out of "the average annual delivery of water to be provided by the states of the upper division at Lees Ferry, under the terms of the Colorado River Compact.” The Governors’ suggestions, like those of the States, explicitly reserved to each State as against the other States the exclusive use of her own tributaries. Arizona agreed to the Governors’ proposal, but she wanted it made clear that her tributaries were to be exempted from any Mexican obligation.43 California rejected the whole proposal, insisting that she must have 4,600,000 acre-feet from the mainstream, or, as she put it, “from the waters to be provided by the States of the upper division at Lee Ferry under the Colorado River' compact.”'44 Neither in the States’ original offers, nor in the Governors’ suggestions, nor in the States’ responses was the “Colorado River System” — mainstream plus tributaries — ever used as the basis for Lower Basin allocations; rather, it was always mainstream water, or the water to be delivered by the upper States at Lee Ferry, that is to say, an annual average of 7,500,000 acre-feet of mainstream water.

With the continued failure of Arizona and California to reach accord, there was mounting impetus for a congressional solution. A Swing-Johnson bill containing no limitation on California’s uses finally passed the House in 1928 over objections by Representatives from Arizona and Utah.45 .When the bill reached the Senate, it was amended in committee to provide that the Secretary in his water delivery contracts must limit California to 4,600,000 ■ acre-feet “of the water allocated to the lower basin by *571the Colorado River compact . . . and one-half of the unallocated, excess, and/or surplus water . . . .”46 On the floor, Senator Phipps of Colorado proposed an amendment which would allow the Act to go into effect without any limitation on California if seven States ratified the Compact; if only six States ratified and if the California Legislature accepted the limitation,- the Act could still become effective.47 Arizona’s Senator Hayden had already proposed an amendment reducing California’s share to 4,200,000 acre-feet (the Governors’ proposal), plus half of the surplus, leaving Arizona exclusive use of the Gila free from any Mexican obligation,48 but this the Senate rejected.49 Senator Bratton of New Mexico, noting that only 400,000 acre-feet kept Arizona and California apart, immediately suggested an amendment by which they would split the difference, California getting 4,400,000 acre-feet “of the waters apportioned to the lower basin States by the Colorado River compact,” plus half of the surplus.50 It was this Bratton amendment that became part of the Act as passed,51 which had been amended on the floor so that the limitation referred to waters apportioned to the Lower Basin “by paragraph (a) of Article III of the Colorado River compact,” instead of waters apportioned “by the Colorado River compact.” 52

*572Statements made throughout the debates make it quite clear ..that Congress intended the 7,500,000 acre-feet it was allocating, and out of which California was limited to 4,400,000, to be mainstream water only. In the first place, the basin Senators expressly acknowledged as the starting point for their debate the Denver Governors’ proposal that specific allocations be made to Arizona, California, and Nevada from the mainstream, leaving the tributaries to the States! For example, Senator Johnson, leading spokesman for California, and Senator Hayden, leading spokesman for Arizona, agreed that the Governors’ recommendations could be used as “a basis for discussion.”53 Hayden went on to observe that the Committee amendment would give California the same 4,600,000 acre-feet she had sought at Denver.54 Later, Nevada’s Senator Pittman stated that the committee “put the amount in there that California demanded before the four governors at Denver,” and said that the Bratton amendment would split the 400,000 acre-feet separating the Governors’ figure and the Committee’s figure.55 All the leaders in the debate — Johnson, Bratton, King, Hayden, Phipps, and Pittman — expressed a common understanding that • the key issue separating Arizona and California was the difference of 400,000 acre-feet,56 precisely the same 400,000 acre-feet of mainstream water *573that had separated the States at Denver. Were we to sustain California’s argument here that tributaries must be included, California would actually get more than she was willing to settle for at Denver.

That the apportionment was from the mainstream only is also strongly indicated by an analysis of the second paragraph of § 4 (a) of the .Act. There Congress authorized Arizona, Nevada, and California to make a compact allocating to Nevada 300,00.0 acre-feet and .to Arizona 2,800,000 plus one-half of the surplus, which,' with California’s 4,400,000 and half of the surplus, would under California’s interpretation of the Act exhaust the Lower Basin waters, both mainstream and tributaries. But Utah and New Mexico, as Congress knew, had interests in Lower Basin tributaries which Congress surely would have protected in some way had it meant for the tributaries of those two States to be included in the water to be divided among Arizona, Nevada, and California. We cannot believe that Congress would have permitted three States to divide among themselves water belonging to five States. Nor can we believe that the representatives of Utah and New Mexico would have sat quietly by and acquiesced in a congressional attempt to include, their tributaries in waters given the other three States. ■

Finally, in considering California’s claim to share in the tributaries of other States, it is important that from the beginning of the discussions and negotiations which led to the Project Act, Arizona consistently claimed that she must have sole use of the Gila, upon which her existing economy depended.57 Arizona’s claim was supported by the fact that only she and New Mexico could effectively use the Gila waters, which not only entered the Colorado *574River too close to Mexico to be of much use to any other State but also was reduced virtually to a trickle in the hot Arizona summers before it could reach the Colorado. In the debates the Senators consistehtly acknowledged that the tributaries — or at least the waters of the Gila, the only major Arizona tributary — were excluded from the allocation they were making. Senator Hayden, in response to questions by Senator Johnson, said that the California Senator was correct in stating that the Senate had seen fit to give Arizona 2,800,000 acre-feet in addition to all the water in the Gila.58 Senator Johnson had earlier stated, “[I]t is only the main stream, Senators will recall, that has been discussed,” and one of his arguments in favor of California’s receiving 4,600,000 acre-feet rather than 4,200,000 was that Arizona was going to keep all her tributaries in addition .to whatever portion of the •main river was allocated to her.59 Senator Johnson also argued that Arizona should bear more than half the Lower Basin’s Mexican burden because in addition to the 2,800,000 acre-feet allotted her by the Act she would get the Gila, which he erroneously estimated at 3,500,000 acre-feet.60 Senator Pittman, who had sat in on the Governors’ conference, likewise understood that the water was being allocated from “the main Colorado River.” 61 And other interested Senators similarly distinguished between the mainstream and the tributaries.62 While the debates, extending over a long period of years, undoubtedly contain statements which support inferences in conflict with those we have drawn, we are persuaded by the legislative history as a whole that the Act was not intended to give *575California any claim to share in the tributary waters of the other Lower Basin States.

C. The Project Act’s Apportionment and Distribution Scheme. — The legislative history, the language of the Act, and the scheme established by the Act for the storage and delivery of water convince us also that Congress intended to provide its own method for a complete apportionment of the mainstream water among Arizona, California, and Nevada.

First, the legislative history. In hearings on the House bill that became the Project Act, Congressman Arentz of Nevada, apparently impatient with the delay of this much needed project, told the committee on January 6, 1928, that if the States could not themselves allocate the water, “there must be some power which will say to California ‘You can not take any more than this amount and the balance is allocated to the other States.’ ” 63 Later, May 25, 1928, the House passed the bill,64 but it did not contain any allocation scheme. When the Senate took up that bill in December, pressure mounted swiftly for amendments that would provide a workable method for apportioning the waters among the Lower Basin States and distributing them to users in the States. The session convened on December 3, 1928, on the fifth the Senate took up the bill,65 nine days later the bill with significant amendments passed the Senate,66 four days after that the House concurred in the Senate’s action,67 and on the twenty-first the President signed the bill.68 When the bill first reached the Senate floor', it had *576a provision, added in committee, limiting California to 4,600,000 acre-feet-,69 and Senator Hayden on December 6 proposed reducing that share to 4,200,000.70 The next day, December 7, Mr. Pittman, senior Senator from Nevada, vigorously argued that Congress should settle the matter without delay. He said,

“What is the difficulty? We have only minor questions involved here. There is practically nothing involved except a dispute between the States of Arizona and California with regard to the division of the increased water that will be impounded behind the proposed dam; that is all. ... Of the 7,500,000 acre-feet of water let down that river they have gotten together within 400,000 acre-feet. They have got to get together, and if they do not get together Congress should bring them together.” 71

The day after that, December 8, New Mexico’s Senator Bratton suggested an amendment splitting the difference between the demands of Arizona and California by limiting California to 4,400,000 acre-feet.72 On the tenth, reflecting the prevailing sense of urgency for decisive action, Senator Bratton emphasized that this was not a dispute limited simply to two States:

“The two States have exchanged views, they have negotiated, they have endeavored to reach an agreement, and until now have been unable to do so. This controversy does not affect those two States alone. It affects other States in the Union and the Government as well.

“Without undertaking to express, my views either way upon the subject, I do think that if the two *577States are unable to agree upon a figure then that we, as a disinterested and friendly agency, should pass a bill which, according to our combined judgment, will justly and equitably settle the controversy. I suggested 4,400,000 acre-feet with that in view. I still hold to the belief that somewhere between the two figures we must fix the amount, and that this difference of 400,000 acre-feet should not be allowed to bar and preclude the passage of this important measure dealing with the enormous quantity of 15,000,000 acre-feet of water and involving seven States as Well as the Government.” 73

The very next day, December 11, this crucial amendment was adopted,74 and on the twelfth Senator Hayden pointed out that the bill settled the dispute over Lower Basin waters by giving 4,400,000 acre-feet to California and 2,800,000 to Arizona:

“One [dispute] is how the seven and a half million acre-feet shall be divided in the lower basin. The Senate' has settled that by a vote — that California may have 4,400,000 acre-feet of that water. It follows logically that if that demand is to be conceded, as everybody agrees, the remainder is 2,800,000 acre-feet for Arizona. That settles that part of the controversy.” 75

On the same day, Senator • Pittman, intimately familiar with the whole water problem,76 summed up the feeling *578of the Senate that the bill fixed a limit on California and “practically allocated” to Arizona her share of the water:

“The Senate has already determined upon the division of water between those States. How? It has determined how much water California may use, and the rest of it is subject to use by Nevada ánd Arizona. Nevada has already admitted that it can use only an insignificant quantity, 300,000 acre-feet. That leaves the rest of it to Arizona. As the bill now stands it is just as much divided as if they had mentioned Arizona and Nevada and the amounts they are to get ... .

“As I understand this amendment, Arizona to-day has practically allocated to it 2,800,000 acre-feet of water in the main Colorado Rivér.” 77

The Senator went on to explain why the Senate had found it necessary to set up its own plan for allocating the water:

“Why do we-not leave it to California to say how much water she shall take out of the river or leave it to Arizona to say how much water she shall take out of the river? It is because it happens to become a duty of the United States Senate to settle this matter, and that is the reason.” 78

Not only do the closing days of the debate show that Congress intended an apportionment among the States