MR. JUSTICE STEWART delivered the opinion of the Court.In these three cases, we review a single judgment of the Court of Appeals for the District of Columbia Circuit to Page 420 U. S. 397 determine whether thermal electric power generating plants that draw cooling water from navigable streams are subject to the licensing jurisdiction of the Federal Power Commission under Part I of the Federal Power Act, c. 285, 41 Stat. 1063, as amended, 16 U.S.C. §§ 791a-823.IOn September 20, 1971, two Indian tribes, five individual Indians, and two environmental groups [Footnote 1] (hereinafter the complainants) filed a complaint with the Commission requesting it to require 10 public utility companies located in the Southwestern United States [Footnote 2] to obtain licenses for six fossil-fueled thermal electric generating plants being constructed by the companies along the Colorado River and its tributaries. [Footnote 3]  The plants are part of a projected vast electric power complex, and the energy generated within this new Southwestern Page 420 U. S. 398 power pool will be transmitted in interstate commerce to load centers as far as 600 miles from the sites of the plants.The six plants involved in these cases, like all thermal electric power plants, will require large amounts of water to cool and condense the steam utilized in the process of generating electricity.  See generally 1 FPC, The 1970 National Power Survey I-10-1 to I-10-20.  The water needed for cooling purposes will be obtained by withdrawing substantial quantities of water from the Colorado River system.  The complaint filed with the Commission asserted that it had licensing jurisdiction over the plants pursuant to § 4(e) of Part I of the Federal Power Act, 16 U.S.C. § 797(e), because all six plants are "project works" for the development, transmission, and utilization of power across and along navigable waters, and because two of the plants will use "surplus water" impounded by a Government dam. [Footnote 4]The Commission, on November 4, 1971, issued an order dismissing the complaint for lack of jurisdiction.  The Page 420 U. S. 399 Commission stated that"the legislative history [of the original Federal Water Power Act] shows that it was not intended that the licensing of thermal stations be included.  This construction of the Commission's licensing jurisdiction under Part I of the Federal Power Act has been the longstanding interpretation of the Commission, [and] has been recognized favorably by the Supreme Court."46 F.P.C. 1126, 1127 (citations omitted).Following denial by the Commission of an application for a rehearing, 46 F.P.C. 1307, the complainants filed a petition in the Court of Appeals for the District of Columbia Circuit to review the Commission's order.  The Court of Appeals undertook a scholarly and comprehensive review of the executive and legislative antecedents of the Federal Water Power Act of 1920, and traced in detail the Act's legislative history and the administrative and judicial interpretations of the Act since its passage.  160 U.S.App.D.C. 83, 489 F.2d 1207.  Based on this voluminous material, the Court of Appeals affirmed the Commission's conclusion that thermal electric plants are not "project works" under § 4(e), and that the Commission's licensing jurisdiction under the clause extends only to hydroelectric generating plants.  "Steam plants," the court held, "were purposely omitted from the congressional scheme."  160 U.S.App.D.C. at 107, 489 F.2d  at 1231.  The Court of Appeals also held, however, that the Commission's licensing authority under the "surplus water" clause of § 4(e) is not similarly limited.  The use of "surplus water" for cooling purposes by thermal electric generating plants is sufficient, the court concluded, to bring those plants within the Commission's licensing jurisdiction.  160 U.S.App.D.C. at 111-117, 489 F.2d  at 1235-1241.  Accordingly, the court remanded the case to the Commission to determine in the first instance whether any of the six plants involved in this case fall Page 420 U. S. 400 under that branch of its licensing authority.  Id. at 118, 489 F.2d  at 1242.  We granted the parties' petitions for writs of certiorari to consider the important questions of statutory construction presented by this litigation.  417 U.S. 944.IIThe question whether thermal electric generating plants are subject to the licensing jurisdiction of the Commission involves no issue as to the extent of congressional power under the Commerce Clause.  It is well established that the interstate transmission of electric energy is fully subject to the commerce power of Congress.  FPC v. Union Electric Co., 381 U. S. 90,  381 U. S. 94; Public Utilities Comm'n v. Attleboro Steam & Elec. Co., 273 U. S. 83,  273 U. S. 86; Electric Bond & Share Co. v. SEC, 303 U. S. 419,  303 U. S. 432-433.  And it is equally clear that projects generating energy for interstate transmission, such as the six plants involved in this case, affect commerce among the States and are therefore within the purview of the federal commerce power, regardless of whether the plants generate electricity by steam or hydroelectric power.  FPC v. Union Electric Co., supra, at  381 U. S. 94-95; see NLRB v. Jones & Laughlin Steel Corp., 301 U. S. 1,  301 U. S. 40-41; Katzenbach v. McClung, 379 U. S. 294,  379 U. S. 301-304.  The only question before us is whether Congress has exercised that power in Part I of the Federal Power Act by requiring a license for the construction and operation of thermal electric power generating plants that withdraw large quantities of water from navigable waters for cooling and other plant purposes.AConsideration of the Commission's statutory licensing authority under Part I of the Federal Power Act must, of course, begin with the language of the Act itself.  Section 4(e), 16 U.S.C. § 797(e), authorizes the Commission Page 420 U. S. 401 to issue licenses to individuals, corporations, or governmental units organized for the purpose of constructing"project works necessary or convenient . . . for the development, transmission, and utilization of power across, along, from, or in any of the streams or other bodies of water over which Congress has jurisdiction . . . or for the purpose of utilizing the surplus water or water power from any Government dam. . . ."Section 23(b) of the Act, 16 U.S.C. § 817, in turn, prohibits the unlicensed construction of such works on any navigable stream as well as the unlicensed utilization of the surplus water from a Government dam for the purpose of developing electric power. [Footnote 5]  "Project" is defined as the complete unit of development of a power plant, 16 U.S.C. § 796(11); and "project works" means the physical structure of a project.  § 796(12).Emphasizing that these provisions do not require that the project works be used to generate "hydroelectric power," but rather merely "power," the complainants assert that the six thermal electric power plants in this case fall squarely within the statutory language defining the Commission's licensing jurisdiction.  Each of the thermal electric facilities undoubtedly qualifies as a "complete unit of development of a power plant."  The physical structure of each "project" therefore must be Page 420 U. S. 402 "project works."  All concede that the plants are located on navigable waters and are engaged in the development of electric power.  Furthermore, water is an integral part of the generation of electricity at the plants, being used to condense the steam which turns the turbines.  The complainants assert that it is "equally indisputable" that the six plants are using "surplus water . . . from [a] Government dam" for the purpose of developing electric power. [Footnote 6]So long as adherence to the literal terms of a statute does not bring about a result completely at variance with the purpose of the statute, the complainants argue, there is no justification for resorting to extrinsic aids such as legislative history to determine congressional intent.  And since modern methods of operating thermal electric power generating plants present an even greater threat to the conservation and orderly development of the power potential in navigable streams than do the operations of hydroelectric projects, [Footnote 7] they argue that recognition of the Commission's licensing jurisdiction over thermal Page 420 U. S. 403 electric plants will actually advance the principal purposes of the Act.The complainants' reliance on the literal language of § 4(e) and on the so-called "plain meaning" rule of statutory construction is not entirely unpersuasive.  But their assertion that thermal electric power plants drawing cooling water from navigable streams are unambiguously included within the Commission's licensing jurisdiction is refuted when § 4(e) is read together with the rest of the Act, as, of course, it must be.  See, e.g., Chemical Workers v. Pittsburgh Glass, 404 U. S. 157,  404 U. S. 185; United States v. Boisdore's Heirs, 8 How. 113,  49 U. S. 122.Section 4(e) itself refers to "dams, water conduits, reservoirs, power houses, transmission lines, or other project works."  The terms that precede "other project works," and which therefore indicate a congressional intent to limit the breadth of that general phrase, see Gooch v. United States, 297 U. S. 124,  297 U. S. 128, refer to features ordinarily associated with hydroelectric facilities.  The definition of "project" in 16 U.S.C. § 796(11) similarly refers to structures normally found in hydroelectric power complexes:  a "project" is the"complete unit of improvement or development, consisting of a power house, all water conduits all dams and appurtenant works and structures (including navigation structures) which are a part of said unit, and all storage, diverting or forebay reservoirs directly connected therewith. . . ."Although the complainants note that a power development utilizing steam as a generating force could have many of the same structures, that possibility only serves to emphasize the ambiguity latent in the seemingly clear language chosen by Congress to define the extent of the Commission's licensing authority.Other provisions of the Act make more apparent the limitations intended by Congress upon the reach of Page 420 U. S. 404 § 4(e).   The Act itself was originally entitled the Federal Water Power Act, 41 Stat. 1077 (emphasis added); [Footnote 8] and the preamble to the Act specified that one of its primary purposes was the development of water power.  Id. at 1063.  In addition, § 4(a) of the Act, 16 U.S.C. § 797(a), authorizes the Commission to conduct investigations concerning "the water power industry and its relation to other industries and to interstate or foreign commerce" (emphasis added); § 4(g), 16 U.S.C. § 797(g), authorizes the Commission to investigate the proposed occupancy of public lands for the development of electric power and to issue such orders as are necessary "to conserve and utilize the navigation and water power resources of the region" (emphasis added).  Similarly, § 10(a) of the Act, 16 U.S.C. § 803(a), provides that all licenses issued under the Act shall be on the condition that the project adopted will be best adapted to a comprehensive plan "for the improvement and utilization of water power development" (emphasis added).In none of these statutory provisions is there any reference to the development or conservation of steam power, despite the fact that, in 1920, as today, thermal electric generating plants produced the greatest portion of this Page 420 U. S. 405 Nation's electric energy. [Footnote 9]  The explicit references to hydroelectric power, and the absence of any such references to steam power, manifest the limited scope of the Act's underlying purpose:  "the comprehensive development of water power."  FPC v. Union Electric Co., 381 U.S.  at 101.BAlthough the language of § 4(e) itself could nonetheless be interpreted as extending the Commission's licensing jurisdiction to include thermal electric power plants located on navigable streams, the legislative history of the Act conclusively demonstrates that Congress intended to subject to regulation only the construction and operation of hydroelectric generating facilities.In 1918, [Footnote 10] an administration bill prepared by the Secretaries of War, Interior, and Agriculture, containing most of the provisions eventually included in the Federal Water Power Act of 1920, was introduced in Congress.  Page 420 U. S. 406 H.R. 8716, 65th Cong., 2d Sess.  In a letter to Representative T. W. Sims, Chairman of the special House Committee on Water Power, which had held hearings on the bill, the Secretaries made it plain that only hydroelectric projects were intended to be covered by the legislation:"It is understood your committee will take action at an early date upon various proposals which have been made concerning water power legislation.  On account of the conditions now affecting the power industry and the need of maintaining our entire industrial machinery at its highest efficiency, a satisfactory solution of the water power problem is, in our judgment, one of the most important steps for the consideration of this Congress and one which should receive attention at the earliest practicable date.""*    *    *    *" "While the form of bill which has been presented for your consideration is directly concerned with water power development only, an adequate solution of this problem will have a favorable and stabilizing effect upon the whole power industry.  Probably no considerable increase in new water power development can be expected immediately, but legislation is urgently needed in order to put existing water power developments, which have been made under inadequate law, into a position of security which will enable them to make extensions and to meet maturing obligations upon favorable terms.""*    *    *    *" "Water power legislation should have in view not only the maintenance of the rights of the public in the national resources, but also the adequate protection of private capital by which such resources are developed.  The bill before you aims to do Page 420 U. S. 407 both."H.R.Rep. No. 715, 65th Cong., 2d Sess., 29.The committee report on H.R. 8716 reflected the administration's theory that the legislation was designed "to provide for the development of hydroelectric power by private capital."  H.R.Rep. No. 715, supra, at 15. [Footnote 11]  Despite the committee's recommendation, the bill failed to pass the 65th Congress because of a Senate filibuster.  See FPC v. Union Electric Co., 381 U.S. at  381 U. S. 102 n. 18.The administration bill was reintroduced in the 66th Congress.  The House Committee on Water Power again recommended approval to meet "the need for legislation for the development of hydroelectric power. . . ."  H.R.Rep. No. 61, 66th Cong., 1st Sess., 4. [Footnote 12]  The Senate Page 420 U. S. 408 Committee on Commerce also recommended adoption of the bill in view of "the need for or the beneficent results to come from water power development."  S.Rep. No. 180, 66th Cong., 1st Sess., 2.  After compromise between the House and Senate on matters unrelated to the issue before us, see H.R.Conf.Rep. No. 910, 66th Cong., 2d Sess., this bill was enacted as the Federal Water Power Act of 1920.Although the legislative history of the Act reveals an ambitious attempt by Congress to provide for comprehensive control over a large number of uses of the Nation's water resources, there is simply no suggestion in any of the legislative materials that the bill would authorize the new Commission to license the construction or maintenance of thermal electric power plants.  "The principal use to be developed and regulated in the Act," this Court explained in FPC v. Union Electric Co., supra, at  381 U. S. 99, "was that of hydroelectric power to meet the needs of an expanding economy."  (Emphasis added; footnote omitted.)  See also 381 U.S. at  381 U. S. 115 (Goldberg, J., dissenting).CThe limited scope of the § 4(e) licensing authority, reflected in both the text of the Act and its legislative history, is reinforced by the Commission's consistent interpretation of that authority as not including jurisdiction over the construction and operation of thermal electric power plants.  In its First Annual Report to Congress, the Commission concluded that Congress intended only to give it licensing authority with respect to hydroelectric projects:"On neither the public lands and reservations nor on the waters of the United States is the jurisdiction of the Federal Power Commission as broad as the jurisdiction of Congress.  The latter has authority Page 420 U. S. 409 over all forms of use; the Commission is limited to the consideration of projects designed to produce water power.  Structures or diversions having any other purpose, unless incidental to works constructed for power purposes or a necessary part of a comprehensive scheme of development, are not within the jurisdiction of the Commission."FPC, First Annual Report 51-52 (emphasis added). [Footnote 13]Ever since that first report in 1921, the Commission has consistently maintained the position that its licensing authority extends only to hydroelectric projects. [Footnote 14]  Such a longstanding, uniform construction by the agency charged with administration of the Federal Power Act, particularly when it involves a contemporaneous construction of the Act by the officials charged with the responsibility Page 420 U. S. 410 of setting its machinery in motion, is entitled to great respect.  Trafficante v. Metropolitan Life Ins. Co., 409 U. S. 205,  409 U. S. 210; Udall v. Tallman, 380 U. S. 1,  380 U. S. 16; Power Reactor Development Co. v. Electrical Workers, 367 U. S. 396,  367 U. S. 408.The deference due this longstanding administrative construction is enhanced by the fact that Congress gave no indication of its dissatisfaction with the agency's interpretation of the scope of its licensing jurisdiction when it amended the Act in 1930, c. 572, 46 Stat. 797, [Footnote 15] or when it reenacted the Federal Water Power Act as Part I of the Federal Power Act in 1935. [Footnote 16]  See Saxbe v. Bustos, 419 U. S. 65; Carmmarano v. United States, 358 U. S. 498,  358 U. S. 510-511; Massachusetts Mutual Life Ins. Co. v. United States, 288 U. S. 269,  288 U. S. 273.  Indeed, on several occasions, the Commission has supported legislative proposals to expand its jurisdiction to encompass licensing authority over the construction and operation of thermal electric generating plants, but has been unable to persuade Congress to act favorably on these proposed amendments to the Act.  See 1962 Annual Report 12-13; 1964 Annual Report In 11; 1966 Annual Report 8-9.DThe conclusion that Congress did not intend to give the Commission licensing jurisdiction with respect to Page 420 U. S. 411 thermal electric power plants is also supported by this Court's decision in FPC v. Union Electric Co., 381 U. S. 90.  The Court there sustained the Commission's position that a license was required under the Act to construct a pumped storage hydroelectric plant to be located on a nonnavigable stream.  Although the plant did not affect commerce on navigable waters, its generation of electricity for interstate transmission would affect "the interests of interstate or foreign commerce" within the meaning of § 23(b) of the Act, 16 U.S.C. § 817, the Court held, and therefore a license was required.  The Union Electric Co., arguing that the Commission lacked licensing authority, asserted that there was no difference between the generation of energy by a thermal electric power plant and by a hydroelectric project in terms of impact on interstate commerce that could justify a distinction in jurisdictional treatment.  Accordingly, if impact on commerce in general, rather than on commerce on navigable waters, was the criterion for Commission jurisdiction, argued Union Electric, steam plants as well as its pumped storage hydroelectric plant should be subject to licensing under Part I of the Federal Power Act.The Court found the answer to this argument in the fact that, even though not located on a navigable stream, Union Electric's generating plant produced electricity by harnessing water power:  Unlike Parts II and III o the Federal Power Act,"under which the Commission regulates various aspects of the sale and transmission of energy in interstate commerce, Part I, the original Federal Page 420 U. S. 412 Water Power Act, is concerned with the utilization of water resources and particularly the power potential in water.  In relation to this central concern of the Act, the distinction between a hydroelectric project and a steam plant is obvious and meaningful, although both produce energy for interstate transmission."381 U.S. at  381 U. S. 110 (footnotes omitted).  See also id. at  381 U. S. 115 (Goldberg, J., dissenting):"The legislative history here, however, establishes to my satisfaction that [Congress] has required licenses of neither steam plants nor the type of hydroelectric plant here involved, and in light of this legislative history, I agree with the Court of Appeals that Congress intended that a license be required only where the interests of commerce on navigable waters are affected."(Footnote omitted.)IIIFor the above reasons, we agree with the conclusion of the Court of Appeals that the structures composing thermal electric power plants are not "project works" required to be licensed by the Commission.  The Court of Appeals went on to hold, however, that the surplus water clause of § 4(e) authorizes the Commission to license the use of such water not only for the development of hydroelectric energy, but also for cooling purposes in thermal electric power plants, finding that the surplus water provision was intended to serve broader interests than the project works clause of the same subsection of the Act."It reflects an explicit concern with utilizing water resources to defray the cost of waterway improvements as well as a concern with comprehensive water resource management.  It empowers the FPC to license the use of either 'surplus water' or 'water power' from any Government dam, and thus is not limited to the mere leasing of excess Government water power. . . .  [T]he addition of the words 'surplus water' in [§ 4(e)] Page 420 U. S. 413 was intended to afford the FPC a broad licensing authority over federally controlled waters. . . .   The FPC could license either the use of 'water power' -- i.e., electricity actually generated by the Government -- or the use of 'surplus water' for the private generation of water power or other purposes."160 U.S.App.D.C. at 116-117, 489 F.2d  at 1240-1241.  We cannot agree with this conclusion of the Court of Appeals with respect to the "surplus water" clause of § 4(e), because we can find no support for it in the text, in the legislative history, or in the administrative interpretation of Part I of the Federal Power Act.The original title, preamble and text of Part I of the Federal Power Act provide strong evidence that Congress intended to restrict the Commission's licensing jurisdiction with respect to the power industry to the construction and maintenance of hydroelectric facilities.  See supra at  420 U. S. 403-404.  Nothing in the language of the Act suggests that the surplus water clause was designed to be an exception to the Act's limited scope and purpose. [Footnote 17]  Similarly, from 1921 to the present, the Commission has consistently interpreted its licensing authority as being "limited to the consideration of projects designed to produce water power."  FPC First Annual Report 51.  See supra at  420 U. S. 408-409.  No exception has ever been recognized Page 420 U. S. 414 by the Commission for thermal electric power plants using surplus water from Government dams.The Court of Appeals' own extensive analysis of the general background and legislative history of the Federal Water Power Act conclusively demonstrates that Congress intended the Act as a whole, not merely the project works clause, to subject to regulation only that segment of the power industry involving the construction and operation of hydroelectric generating facilities.  See 160 U.S.App.D.C. at 91-109, 489 F.2d  at 1211233; cf. supra at  420 U. S. 405-408.  More importantly, the legislative history pertaining to the surplus water clause itself indicates that that clause, like the rest of the Act, relates to the conservation and development of only hydroelectric power.The phrase "surplus water or water power from any Government dam" had its origins in legislation enacted during the late 19th and early 20th centuries, conferring on the Secretary of War the authority to lease at individual dam sites excess water for power development. [Footnote 18]  The term "surplus water" in those statutes always referred to its use for the development of water power. [Footnote 19] Page 420 U. S. 415In 1914, the Adamson bill, H.R. 16053, 63d Cong., 2d Sess., was introduced to amend the Dam Act, 34 Stat. 386, by providing for the comprehensive regulation of water power development on navigable streams.  Section 14 of the bill, the antecedent of § 4(e)'s surplus water clause, authorized the Secretary of War to lease"the right to develop power from the surplus water over and above that required for navigation at any navigation dam now or hereafter constructed . . . and owned by the United States. . . ."51 Cong.Rec. 11415.  The report of the House Committee on Interstate and Foreign Commerce [Footnote 20] and congressional debate on § 14 plainly indicate that only water power uses of surplus water were to be regulated. [Footnote 21]  Steam power was mentioned only as a competing Page 420 U. S. 416 source of electric energy, with no consideration given to its regulation. [Footnote 22]Section 14 was amended on the floor of the House to limit the duration of the leases authorized to 50 years.  The amendment also changed the surplus water language of the section so that it closely resembled the language later adopted in the Federal Water Power Act:  amended § 14 authorized"leases for the use of surplus water and water power generated at dams and works constructed wholly or in part by the United States in the interest of navigation. . . ."51 Cong.Rec. 1325 (emphasis added).  The change in language was not intended to broaden the scope of the surplus water clause.  See id. at 13257.The Senate Commerce Committee reported out a substitute bill, S. 6413, 63d Cong., 2d Sess., rather than the amended Adamson bill.  Like the House bill, S. 6413, containing another version of a surplus water clause, [Footnote 23] was directed only to"[t]he question of water power development by the construction of dams across navigable streams and the improvement of navigation in connection with water power development."S.Rep. No. 846, 63d Cong., 3d Sess., 1 (emphasis added).  Neither bill, however, was enacted during the 63d Congress.Similar bills were introduced in the 64th and 65th Congresses.  Again, nothing in the language or reports on any of that proposed legislation indicated that the licensing authority to be created would extend to the Page 420 U. S. 417 use of "surplus water" by steam plants.  Section 10 of the Shields bill, S. 3331, 64th Cong., 1st Sess., for example, authorized the Secretary of War to ease "the right to utilize the surplus water power over and above that required for navigation at any navigation dam now or hereafter constructed. . . ."  53 Cong.Rec. 2198.  The House Committee on Interstate and Foreign Commerce struck S. 3331 in its entirety and substituted a new bill.  Section 19 of that bill, identical to § 14 of the amended Adamson bill that had been passed by the House in 1914, authorized the Secretary of War"to enter into leases for the use of surplus water and water power generated at dams and works constructed wholly or in part by the United States in the interests of navigation. . . ."H.R.Rep. No. 404, 64th Cong., 1st Sess., 6.  The committee report explained that"[s]ection 19 regulates the method to be pursued by the War Department in leasing the power at dams erected in whole or in part by the Government itself."Id. at 11.  The section, stated the committee,"continues the method existing as to Government dams for many years, under which the War Department has satisfactorily regulated and leased surplus water at a number of such structures."Ibid.  The "method existing," of course, provided for the lease of surplus water at individual dams for the purpose of water power development.The administration bill considered initially by the 65th Congress, H.R. 8716, 65th Cong., 2d Sess., which as amended by that Congress and the 66th Congress, became the Federal Water Power Act of 1920, contained a surplus water clause that paralleled the provisions of the earlier bills.  Section 4(d) of that bill, now § 4(e) of the Federal Power Act, authorized the Federal Power Commission to issue licenses"for the purpose of utilizing the surplus water or water power over and above that Page 420 U. S. 418 required for navigation at any navigation dam now or hereafter constructed . . . and owned by the United States. . . ."H.R.Rep. No. 715, 65th Cong., 2d Sess., 23.  No explanation was given for substitution of the disjunctive "or" for the conjunctive "and" in the phrase "surplus water or water power," but there is nothing to indicate that the change was designed to expand the scope of surplus water licensing authority beyond that contemplated by the earlier proposed legislation.  To the contrary, testimony given during the extensive hearings conducted by the special House Committee on Water Power reflected the general understanding that the Commission's licensing jurisdiction would be limited to hydroelectric facilities. [Footnote 24]The administration bill, as already noted, see supra at  420 U. S. 407, was reintroduced in the 66th Congress, and was enacted without any material changes in the surplus water clause as the Federal Water Power Act of 1920.  As the Court of Appeals observed, see 160 U.S.App.D.C. at 112-113, 489 F.2d  at 1236-1237, little relevant legislative history concerning the meaning of the surplus water clause was generated during the 66th Congress.  Page 420 U. S. 419 Nevertheless, the general history of the Act demonstrates that the legislators viewed the bill as primarily regulating the development of hydroelectric power.  Nothing in the record of the debates indicates that Congress intended the surplus water clause to create an exception to the limited scope and purpose of the Act or that it viewed that clause as embodying a meaning different from that of the virtually identical surplus water provisions contained in earlier legislative proposals.The Court of Appeals based its contrary conclusion in large part on the fact that the Federal Water Power Act repealed the statutory authority for the Waterways Commission, created by the Rivers and Harbors Act of 1917.  40 Stat. 269.  The court stated that"the newly created Federal Power Commission took over the planning and coordinating responsibilities of the Waterways Commission, which included consideration of a spectrum of water uses not related to water power."160 U.S.App.D.C. at 115-116, 489 F.2d  at 1239-1240 (footnote omitted).  The court concluded from this transfer of responsibilities that the Federal Water Power Act reflected a concern with comprehensive water resource management and that the surplus water clause was intended to provide a basis for expanding governmental supervision of general water resource development and use.  Id. at 116-117, 489 F.2d  at 1240-1241.Although it is true that § 29 of the Federal Water Power Act, 41 Stat. 1077, did expressly repeal the statutory authority for the Waterways Commission, it seems evident that that repeal was not intended to transfer all of that Commission's functions to the new Federal Power Commission.  The House debates clearly indicate that the Waterways Commission authority was repealed largely because that Commission was not, in fact, a functioning agency, and in order to prevent any possible conflict between Page 420 U. S. 420 it and the new FPC.  There is no indication of any purpose to transfer the Waterways Commission's jurisdiction to the FPC.  E.g., 58 Cong.Rec. 2250-2251 (remarks of Rep. Anderson).  In fact, a proposed amendment that would have provided for such a transfer of authority was never actually introduced in the Senate.  See 59 Cong.Rec. 1173-1176 (remarks of Sens. Ashurst, Fletcher, and Ransdell).  Those functions of the Waterways Commission not expressly given to the new FPC or transferred to other agencies were thus simply eliminated by § 29. [Footnote 25]Moreover, the responsibilities which the Waterways Commission did possess from 1917 to 1920, although quite broad, were investigatory, not regulatory.  The Commission was authorized"to secure the necessary data, and to formulate and report to Congress . . . a comprehensive plan or plans for the development of waterways and the water resources of the United States for the purposes of navigation and for every useful purpose, and recommendations for the modification or discontinuance of any project herein or heretofore adopted."Rivers and Harbors Act of 1917, § 18, 40 Stat. 269.  Accordingly, even if it could be concluded that the Waterways Commission's powers had been inherited by the FPC, that conclusion would not support recognition of Commission licensing jurisdiction over thermal electric power plants using "surplus water" for cooling purposes. [Footnote 26] Page 420 U. S. 421Contrary to the suggestion of the complainants, a reading of the surplus water provision as referring only to hydroelectric plants utilizing surplus water or water power from Government dams does not render that clause nugatory.  First, a license to construct and operate project works does not automatically authorize use of surplus water from a Government dam.  Where a project will use surplus water, the Commission may properly require a second license, which may impose additional charges or operational conditions on the licensee.  Cf. Alabama Power Co., 34 F.P.C. 1108; California Oregon Power Co., 13 F.P.C. 1, 12-13, supplemental opinion, 15 F.P.C. 14, 18-21, petition for review dismissed, 99 U.S.App.D.C. 263, 239 F.2d 426.  Second, facilities constructed under a congressional grant issued prior to enactment of the Federal Water Power Act are exempted by § 23(b) of the Act, 16 U.S.C. § 817, from the requirement of Page 420 U. S. 422 securing a "project works" license from the Commission during the life of the original works.  See Northwest Paper Co. v. FPC, 344 F.2d 47.  However, if such a project should seek to utilize surplus water from a Government dam built subsequent to June 10, 1920, a surplus water clause license would be required.  Finally, it is by no means irrational for Congress to provide the Commission with alternative, albeit sometimes coextensive, bases of jurisdiction, so that it can proceed on the strength of one where the existence of the other may be unclear.IVThe complainants finally argue that, even though it may have been proper 50 years ago to construe the Commission's licensing jurisdiction as limited to hydroelectric projects, such a construction does great violence to the policies central to the Federal Power Act in the light of modern conditions.  Although, in 1920, steam plants supplied the bulk of the Nation's electric power and, as today, those plants were water-cooled, [Footnote 27] the complainants point to the tremendous growth in size and efficiency of the modern thermal electric power complex and the concomitant increase during the past half-century in the quantity of water used by steam plants and change in the nature of that usage. [Footnote 28]  Because the cooling Page 420 U. S. 423 water used by the six plants involved in this case will be evaporated, rather than returned to the river system, [Footnote 29] those plants will withdraw permanently up to 250,000 acre feet of water annually from the Colorado River system -- more water than was used by all the steam plants in the United States in 1920. [Footnote 30]  Unless such uses are regulated by subjecting them to the licensing jurisdiction of the Commission, the complainants argue, private power interests will succeed in appropriating the power potential in public waters, the very evil the Federal Water Power Act was designed to eliminate.  Whatever the merits of the complainants' argument as a matter of policy, it is properly addressed to Congress, not to the courts.  The legislative history of the Federal Water Power Act conclusively demonstrates that, in 1920, Congress intended to provide for the orderly development of the power potential of the Nation's waterways only through the licensing of hydroelectric projects.  And in Page 420 U. S. 424 1935; when the Act was reenacted as Part I of the Federal Power Act, Congress chose not to expand the licensing authority of the Commission despite the fact that, in Parts II and III of the Act, giving the Commission regulatory authority over various aspects of the transmission and sale of electric energy in interstate commerce, Congress treated the source of the energy and the method of generation as immaterial.  See FPC v. Union Electric Co., 381 U.S. at  381 U. S. 110.  Moreover, several times in recent years, the Commission has sought an expansion of its licensing jurisdiction to include thermal electric power generating plants, but Congress has failed to approve any of these proposals.It may well be that the "obvious" distinction, recognized by Congress in 1920, in 1935, and in subsequent years of inaction, and by this Court in the Union Electric case, supra, at  381 U. S. 110, between utilization of water resources by a hydroelectric project and a thermal electric power plant is no longer viable.  But until Congress changes the licensing provisions of Part I of the Federal Power Act, it is our duty to apply the statute as it was written and has been construed for the past 54 years.For the foregoing reasons, the judgment before us is vacated, and the cases are remanded to the Court of Appeals with directions to enter a judgment affirming the Commission's dismissal of the complaint for lack of jurisdiction.It is so ordered
U.S. Supreme CourtChemehuevi Tribe of Indians v. FPC, 420 U.S. 395 (1975)Chemehuevi Tribe of Indians v. Federal Power CommissionNo. 73-1380Argued January 13, 1975Decided March 3, 1975*420 U.S. 395SyllabusUnder § 4(e) of Part I of the Federal Power Act, the Federal Power Commission (FPC) is authorized to issue licenses to individuals, corporations, or governmental units organized for the purpose of constructing"project works necessary or convenient . . . for the development, transmission, and utilization of power across, along, from, or in any of the streams or other bodies of water over which Congress has jurisdiction . . or for the purpose of utilizing the surplus water or water power from any Government dam. . . ."Section 23(b) prohibits the unlicensed construction of such works on any navigable stream, as well as the unlicensed utilization of such surplus water for the purposes of developing electric power.Held:  These provisions of Part I of the Act giving the FPC licensing jurisdiction over hydroelectric facilities do not also confer such jurisdiction over thermal electric power plants.  Pp.  420 U. S. 400-422.(a) The structures constituting thermal electric power plants are not "project works" within the meaning of § 4(e), as is clear from the language of that provision when read together with the rest of the Act (none of whose provisions refers to the development or conservation of steam power), the Act's legislative history (which manifests a congressional intent to regulate only hydroelectric generating facilities), the FPC's consistent interpretation of its authority as not including jurisdiction over thermal electric power plants, and this Court's decision in FPC v. Union Electric Co., 381 U. S. 90.  Pp.  420 U. S. 400-412.(b) The surplus water clause of § 4(e) does not authorize FPC licensing of water used for cooling purposes in thermal electric power plants, nothing in the Act's language or legislative history disclosing any congressional intent that that clause should serve any broader interests than the project works clause.  And, contrary Page 420 U. S. 396 to the Court of Appeals' holding, the Act does not vest the FPC with all the responsibilities that, prior legislation had given to the Waterways Commission, responsibilities that, in any case did not include licensing the use of surplus water by steam plants.  Pp.  420 U. S. 412-422.160 U.S.App.D.C. 83, 489 F.2d 1207, vacated and remanded.STEWART, J., delivered the opinion of the Court, in which all other Members joined except DOUGLAS, J., who took no part in the consideration or decision of the cases.