Justice White
delivered the opinion of the Court.
The issue in this case is whether the Federal Water Pollution Control Act (FWPCA or Act), 86 Stat. 816, as amended, 33 U. S. C. § 1251 et seq. (1976 ed. and Supp. IV), requires a district court to enjoin immediately all discharges of pollut[307]*307ants that do not comply with the Act’s permit requirements or whether the district court retains discretion to order other relief to achieve compliance. The Court of Appeals for the First Circuit held that the Act withdrew the courts’ equitable discretion. Romero-Barcelo v. Brown, 643 F. 2d 835 (1981). We reverse.
I
For many years, the Navy has used Vieques Island, a small island off the Puerto Rico coast, for weapons training. Currently all Atlantic Fleet vessels assigned to the Mediterranean Sea and the Indian Ocean are required to complete their training at Vieques because it permits a full range of exercises under conditions similar to combat. During air-to-ground training, however, pilots sometimes miss land-based targets, and ordnance falls into the sea. That is, accidental bombings of the navigable waters and, occasionally, intentional bombings of water targets occur. The District Court found that these discharges have not harmed the quality of the water.
In 1978, respondents, who include the Governor of Puerto Rico and residents of the island, sued to enjoin the Navy’s operations on the island. Their complaint alleged violations of numerous federal environmental statutes and various other Acts.1 After an extensive hearing, the District Court found [308]*308that under the explicit terms of the Act, the Navy had violated the Act by discharging ordnance into the waters surrounding the island without first obtaining a permit from the Environmental Protection Agency (EPA).2 Romero-Barcelo v. Brown, 478 F. Supp. 646 (PR 1979).
Under the FWPCA, the “discharge of any pollutant” requires a National Pollutant Discharge Elimination System (NPDES) permit. 38 U. S. C. §§ 1311(a), 1323(a) (1976 ed. and Supp. IV). The term “discharge of any pollutant” is defined as
“any addition of any pollutant to the waters of the contiguous zone or the ocean from any point source other than a vessel or other floating craft.” 33 U. S. C. § 1362(12) (emphasis added).
Pollutant, in turn, means
“dredged spoil, solid waste, incinerator residue, sewage, garbage, sewage sludge, munitions, chemical wastes, biological materials, radioactive materials, heat, wrecked [309]*309or discarded equipment, rock, sand, cellar dirt and industrial, municipal, and agricultural waste discharged into water. . . 33 U. S. C. § 1362(6) (emphasis added).
And, under the Act, a “point source” is
“any discernible, confined and discrete conveyance, including but not limited to any pipe, ditch, channel, tunnel, conduit, well, discrete fissure, container, rolling stock, concentrated animal feeding operation, or vessel or other floating craft from which pollutants are or may be discharged. . . .” 33 U. S. C. § 1362(14) (1976 ed., Supp. IV) (emphasis added).
Under the FWPCA, the EPA may not issue an NPDES permit without state certification that the permit conforms to state water quality standards. A State has the authority to deny certification of the permit application or attach conditions to the final permit. 33 U. S. C. § 1341.
As the District Court construed the FWPCA, the release of ordnance from aircraft or from ships into navigable waters is a discharge of pollutants, even though the EPA, which administers the Act, had not promulgated any regulations setting effluent levels or providing for the issuance of an NPDES permit for this category of pollutants.3 Recognizing that violations of the Act “must be cured,” 478 F. Supp., at 707, the District Court ordered the Navy to apply for an NPDES permit. It refused, however, to enjoin Navy operations pend[310]*310ing consideration of the permit application. It explained that the Navy’s “technical violations” were not causing any “appreciable harm” to the environment.4 Id., at 706. Moreover, because of the importance of the island as a training center, “the granting of the injunctive relief sought would cause grievous, and perhaps irreparable harm, not only to Defendant Navy, but to the general welfare of this Nation.”5 Id., at 707. The District Court concluded that an injunction was not necessary to ensure suitably prompt compliance by the Navy. To support this conclusion, it emphasized an equity court’s traditionally broad discretion in deciding appropriate relief and quoted from the classic description of injunc-tive relief in Hecht Co. v. Bowles, 321 U. S. 321, 329-330 (1944): “The historic injunctive process was designed to deter, not to punish.”
The Court of Appeals for the First Circuit vacated the District Court’s order and remanded with instructions that the court order the Navy to cease the violation until it obtained a permit. 643 F. 2d 835 (1981). Relying on TVA v. Hill, 437 U. S. 153 (1978), in which this Court held that an imminent violation of the Endangered Species Act required injunctive relief, the Court of Appeals concluded that the District Court [311]*311erred in undertaking a traditional balancing of the parties’ competing interests. “Whether or not the Navy’s activities in fact harm the coastal waters, it has an absolute statutory obligation to stop any discharges of pollutants until the permit procedure has been followed and the Administrator of the Environmental Protection Agency, upon review of the evidence, has granted a permit.” 643 F. 2d, at 861. The court suggested that if the order would interfere significantly with military preparedness, the Navy should request that the President grant it an exemption from the requirements in the interest of national security.”6
[310]*310“In fact, if anything, these waters are as aesthetically acceptable as any to be found anywhere, and Plaintiff's witnesses unanimously testified as to their being the best fishing grounds in Vieques.” 478 F. Supp., at 667. “[I]f the truth be said, the control of large areas of Vieques [by the Navy] probably constitutes a positive factor in its over all ecology. The very fact that there are in the Navy zones modest numbers of various marine species which are practically non-existent in the civilian sector of Vieques or in the main island of Puerto Rico, is an eloquent example of res ipsa loquitur.” Id.,
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Justice White
delivered the opinion of the Court.
The issue in this case is whether the Federal Water Pollution Control Act (FWPCA or Act), 86 Stat. 816, as amended, 33 U. S. C. § 1251 et seq. (1976 ed. and Supp. IV), requires a district court to enjoin immediately all discharges of pollut[307]*307ants that do not comply with the Act’s permit requirements or whether the district court retains discretion to order other relief to achieve compliance. The Court of Appeals for the First Circuit held that the Act withdrew the courts’ equitable discretion. Romero-Barcelo v. Brown, 643 F. 2d 835 (1981). We reverse.
I
For many years, the Navy has used Vieques Island, a small island off the Puerto Rico coast, for weapons training. Currently all Atlantic Fleet vessels assigned to the Mediterranean Sea and the Indian Ocean are required to complete their training at Vieques because it permits a full range of exercises under conditions similar to combat. During air-to-ground training, however, pilots sometimes miss land-based targets, and ordnance falls into the sea. That is, accidental bombings of the navigable waters and, occasionally, intentional bombings of water targets occur. The District Court found that these discharges have not harmed the quality of the water.
In 1978, respondents, who include the Governor of Puerto Rico and residents of the island, sued to enjoin the Navy’s operations on the island. Their complaint alleged violations of numerous federal environmental statutes and various other Acts.1 After an extensive hearing, the District Court found [308]*308that under the explicit terms of the Act, the Navy had violated the Act by discharging ordnance into the waters surrounding the island without first obtaining a permit from the Environmental Protection Agency (EPA).2 Romero-Barcelo v. Brown, 478 F. Supp. 646 (PR 1979).
Under the FWPCA, the “discharge of any pollutant” requires a National Pollutant Discharge Elimination System (NPDES) permit. 38 U. S. C. §§ 1311(a), 1323(a) (1976 ed. and Supp. IV). The term “discharge of any pollutant” is defined as
“any addition of any pollutant to the waters of the contiguous zone or the ocean from any point source other than a vessel or other floating craft.” 33 U. S. C. § 1362(12) (emphasis added).
Pollutant, in turn, means
“dredged spoil, solid waste, incinerator residue, sewage, garbage, sewage sludge, munitions, chemical wastes, biological materials, radioactive materials, heat, wrecked [309]*309or discarded equipment, rock, sand, cellar dirt and industrial, municipal, and agricultural waste discharged into water. . . 33 U. S. C. § 1362(6) (emphasis added).
And, under the Act, a “point source” is
“any discernible, confined and discrete conveyance, including but not limited to any pipe, ditch, channel, tunnel, conduit, well, discrete fissure, container, rolling stock, concentrated animal feeding operation, or vessel or other floating craft from which pollutants are or may be discharged. . . .” 33 U. S. C. § 1362(14) (1976 ed., Supp. IV) (emphasis added).
Under the FWPCA, the EPA may not issue an NPDES permit without state certification that the permit conforms to state water quality standards. A State has the authority to deny certification of the permit application or attach conditions to the final permit. 33 U. S. C. § 1341.
As the District Court construed the FWPCA, the release of ordnance from aircraft or from ships into navigable waters is a discharge of pollutants, even though the EPA, which administers the Act, had not promulgated any regulations setting effluent levels or providing for the issuance of an NPDES permit for this category of pollutants.3 Recognizing that violations of the Act “must be cured,” 478 F. Supp., at 707, the District Court ordered the Navy to apply for an NPDES permit. It refused, however, to enjoin Navy operations pend[310]*310ing consideration of the permit application. It explained that the Navy’s “technical violations” were not causing any “appreciable harm” to the environment.4 Id., at 706. Moreover, because of the importance of the island as a training center, “the granting of the injunctive relief sought would cause grievous, and perhaps irreparable harm, not only to Defendant Navy, but to the general welfare of this Nation.”5 Id., at 707. The District Court concluded that an injunction was not necessary to ensure suitably prompt compliance by the Navy. To support this conclusion, it emphasized an equity court’s traditionally broad discretion in deciding appropriate relief and quoted from the classic description of injunc-tive relief in Hecht Co. v. Bowles, 321 U. S. 321, 329-330 (1944): “The historic injunctive process was designed to deter, not to punish.”
The Court of Appeals for the First Circuit vacated the District Court’s order and remanded with instructions that the court order the Navy to cease the violation until it obtained a permit. 643 F. 2d 835 (1981). Relying on TVA v. Hill, 437 U. S. 153 (1978), in which this Court held that an imminent violation of the Endangered Species Act required injunctive relief, the Court of Appeals concluded that the District Court [311]*311erred in undertaking a traditional balancing of the parties’ competing interests. “Whether or not the Navy’s activities in fact harm the coastal waters, it has an absolute statutory obligation to stop any discharges of pollutants until the permit procedure has been followed and the Administrator of the Environmental Protection Agency, upon review of the evidence, has granted a permit.” 643 F. 2d, at 861. The court suggested that if the order would interfere significantly with military preparedness, the Navy should request that the President grant it an exemption from the requirements in the interest of national security.”6
[310]*310“In fact, if anything, these waters are as aesthetically acceptable as any to be found anywhere, and Plaintiff's witnesses unanimously testified as to their being the best fishing grounds in Vieques.” 478 F. Supp., at 667. “[I]f the truth be said, the control of large areas of Vieques [by the Navy] probably constitutes a positive factor in its over all ecology. The very fact that there are in the Navy zones modest numbers of various marine species which are practically non-existent in the civilian sector of Vieques or in the main island of Puerto Rico, is an eloquent example of res ipsa loquitur.” Id., at 682 (footnote omitted).
[311]*311Because this case posed an important question regarding the power of the federal courts to grant or withhold equitable relief for violations of the FWPCA, we granted certiorari, 454 U. S. 813 (1981). We now reverse.
I-H I — I
It goes without saying that an injunction is an equitable remedy. It “is not a remedy which issues as of course,” Harrisonville v. W. S. Dickey Clay Mfg. Co., 289 U. S. 334, 337-338 (1933), or “to restrain an act the injurious consequences of which are merely trifling.” Consolidated Canal [312]*312Co. v. Mesa Canal Co., 177 U. S. 296, 302 (1900). An injunction should issue only where the intervention of a court of equity “is essential in order effectually to protect property rights against injuries otherwise irremediable.” Cavanaugh v. Looney, 248 U. S. 453, 456 (1919). The Court has repeatedly held that the basis for injunctive relief in the federal courts has always been irreparable injury and the inadequacy of legal remedies. Rondeau v. Mosinee Paper Corp., 422 U. S. 49, 61 (1975); Sampson v. Murray, 415 U. S. 61, 88 (1974); Beacon Theaters, Inc. v. Westover, 359 U. S. 500, 506-507 (1959); Hecht Co. v. Bowles, supra, at 329.
Where plaintiff and defendant present competing claims of injury, the traditional function of equity has been to arrive at a “nice adjustment and reconciliation” between the competing claims, Hecht Co. v. Bowles, supra, at 329. In such cases, the court “balances the conveniences of the parties and possible injuries to them according as they may be affected by the granting or withholding of the injunction.” Yakus v. United States, 321 U. S. 414, 440 (1944). “The essence of equity jurisdiction has been the power of the Chancellor to do equity and to mould each decree to the necessities of the particular case. Flexibility rather than rigidity has distinguished it.” Hecht Co. v. Bowles, supra, at 329.
In exercising their sound discretion, courts of equity should pay particular regard for the public consequences in employing the extraordinary remedy of injunction. Railroad Comm’n v. Pullman Co., 312 U. S. 496, 500 (1941). Thus, the Court has noted that “[t]he award of an interlocutory injunction by courts of equity has never been regarded as strictly a matter of right, even though irreparable injury may otherwise result to the plaintiff,” and that “where an injunction is asked which will adversely affect a public interest for whose impairment, even temporarily, an injunction bond cannot compensate, the court may in the public interest withhold relief until a final determination of the rights of the parties, though the postponement may be burdensome to the [313]*313plaintiff.” Yakus v. United States, supra, at 440 (footnote omitted). The grant of jurisdiction to ensure compliance with a statute hardly suggests an absolute duty to do so under any and all circumstances, and a federal judge sitting as chancellor is not mechanically obligated to grant an injunction for every violation of law. TVA v. Hill, 437 U. S., at 193; Hecht Co. v. Bowles, 321 U. S., at 329.
These commonplace considerations applicable to cases in which injunctions are sought in the federal courts reflect a “practice with a background of several hundred years of history,” Hecht Co. v. Bowles, supra, at 329, a practice of which Congress is assuredly well aware. Of course, Congress may intervene and guide or control the exercise of the courts’ discretion, but we do not lightly assume that Congress has intended to depart from established principles. Hecht Co. v. Bowles, supra, at 329. As the Court said in Porter v. Warner Holding Co., 328 U. S. 395, 398 (1946):
“Moreover, the comprehensiveness of this equitable jurisdiction is not to be denied or limited in the absence of a clear and valid legislative command. Unless a statute in so many words, or by a necessary and inescapable inference, restricts the court’s jurisdiction in equity, the full scope of that jurisdiction is to be recognized and applied. ‘The great principles of equity, securing complete justice, should not be yielded to light inferences, or doubtful construction.’ Brown v. Swann, 10 Pet. 497, 503 . . . .”
In TVA v. Hill, we held that Congress had foreclosed the exercise of the usual discretion possessed by a court of equity. There, we thought that “[o]ne would be hard pressed to find a statutory provision whose terms were any plainer” than that before us. 437 U. S., at 173. The statute involved, the Endangered Species Act, 87 Stat. 884, 16 U. S. C. § 1531 et seq., required the District Court to enjoin completion of the Tellico Dam in order to preserve the snail [314]*314darter, a species of perch. The purpose and language of the statute under consideration in Hill, not the bare fact of a statutory violation, compelled that conclusion. Section 7 of the Act, 16 U. S. C. § 1536, requires federal agencies to “insure that actions authorized, funded, or carried out by them do not jeopardize the continued existence of [any] endangered species ... or result in the destruction or modification of habitat of such species which is determined ... to be critical.” The statute thus contains a flat ban on the destruction of critical habitats.
It was conceded in Hill that completion of the dam would eliminate an endangered species by destroying its critical habitat. Refusal to enjoin the action would have ignored the “explicit provisions of the Endangered Species Act.” 437 U. S., at 173. Congress, it appeared to us, had chosen the snail darter over the dam. The purpose and language of the statute limited the remedies available to the District Court; only an injunction could vindicate the objectives of the Act.
That is not the case here. An injunction is not the only means of ensuring compliance. The FWPCA itself, for example, provides for fines and criminal penalties. 33 U. S. C. §§ 1319(c) and (d). Respondents suggest that failure to enjoin the Navy will undermine the integrity of the permit process by allowing the statutory violation to continue. The integrity of the Nation’s waters, however, not the permit process, is the purpose of the FWPCA.7 As Congress explained, the objective of the FWPCA is to “restore and maintain the chemical, physical, and biological integrity of the Nation’s waters.” 33 U. S. C. § 1251(a).
[315]*315This purpose is to be achieved by compliance with the Act, including compliance with the permit requirements.8 Here, however, the discharge of ordnance had not polluted the waters, and, although the District Court declined to enjoin the discharges, it neither ignored the statutory violation nor undercut the purpose and function of the permit system. The court ordered the Navy to apply for a permit.9 It temporarily, not permanently, allowed the Navy to continue its activities without a permit.
In Hill, we also noted that none of the limited “hardship exemptions” of the Endangered Species Act would “even remotely apply to the Tellico Project.” 437 U. S., at 188. The prohibition of the FWPCA against discharge of pollutants, in contrast, can be overcome by the very permit the Navy was ordered to seek.10 The Senate Report to the 1972 [316]*316Amendments explains that the permit program would be enacted because “the Committee recognizes the impracticality of any effort to halt all pollution immediately.” S. Rep. No. 92-414, p. 43 (1971). That the scheme as a whole contemplates the exercise of discretion and balancing of equities militates against the conclusion that Congress intended to deny courts their traditional equitable discretion in enforcing the statute.
Other aspects of the statutory scheme also suggest that Congress did not intend to deny courts the discretion to rely on remedies other than an immediate prohibitory injunction. Although the ultimate objective of the FWPCA is to eliminate all discharges of pollutants into the navigable waters by 1985, the statute sets forth a scheme of phased compliance. As enacted, it called for the achievement of the “best practicable control technology currently available” by July 1, 1977, and the “best available technology economically achievable” by July 1, 1983. 33 U. S. C. § 1311(b). This scheme of phased compliance further suggests that this is a statute in which Congress envisioned, rather than curtailed, the exercise of discretion.11
[317]*317The FWPCA directs the Administrator of the EPA to seek an injunction to restrain immediately discharges of pollutants he finds to be presenting “an imminent and substantial endangerment to the health of persons or to the welfare of persons.” 33 U. S. C. § 1364(a) (1976 ed., Supp. IV). This rule of immediate cessation, however, is limited to the indicated class of violations. For other kinds of violations, the FWPCA authorizes the Administrator of the EPA “to commence a civil action for appropriate relief, including a permanent or temporary injunction, for any violation for which he is authorized to issue a compliance order . . . .” 33 U. S. C. § 1319(b).12 The provision makes clear that Congress did not [318]*318anticipate that all discharges would be immediately enjoined. Consistent with this view, the administrative practice has not been to request immediate cessation orders. “Rather, enforcement actions typically result, by consent or otherwise, in a remedial order setting out a detailed schedule of compliance designed to cure the identified violation of the Act.” Brief for Petitioners 17. See Milwaukee v. Illinois, 451 U. S. 304, 320-322 (1981). Here, again, the statutory scheme contemplates equitable consideration.
Both the Court of Appeals and respondents attach particular weight to the provision of the FWPCA permitting the President to exempt federal facilities from compliance with the permit requirements. 33 U. S. C. § 1323(a) (1976 ed., Supp. IV).13 They suggest that this provision indicates congressional intent to limit the court’s discretion. According to respondents, the exemption provision evidences Congress’ determination that only paramount national interests justify failure to comply and that only the President should make this judgment.
We do not construe the provision so broadly. We read the FWPCA as permitting the exercise of a court’s equitable discretion, whether the source of pollution is a private party or a federal agency, to order relief that will achieve compliance with the Act. The exemption serves a different and complementary purpose, that of permitting noncompliance by federal agencies in extraordinary circumstances. Executive Order No. 12088, 3 CFR 243 (1979), which implements the exemption authority, requires the federal agency requesting such an exemption to certify that it cannot meet the applicable pollution standards. “Exemptions are granted by the President only if the conflict between pollution control standards and crucial federal activities cannot be resolved through the development of a practicable remedial program.” Brief for Petitioners 26, n. 30.
[319]*319Should the Navy receive a permit here, there would be no need to invoke the machinery of the Presidential exemption. If not, this course remains open. The exemption provision would enable the President, believing paramount national interests so require, to authorize discharges which the District Court has enjoined. Reading the statute to permit the exercise of a court’s equitable discretion in no way eliminates the role of the exemption provision in the statutory scheme.
Like the language and structure of the Act, the legislative history does not suggest that Congress intended to deny courts their traditional equitable discretion. Congress passed the 1972 Amendments because it recognized that “the national effort to abate and control water pollution has been inadequate in every vital aspect.” S. Rep. No. 92-414, p. 7 (1971). The past failings included enforcement efforts under the Rivers and Harbors Appropriation Act of 1899 (Refuse Act), 33 U. S. C. § 401 et seq. The “major purpose” of the 1972 Amendments was “to establish a comprehensive long-range policy for the elimination of water pollution.” S. Rep. No. 92-414, supra, at 95. The permit system was the key to that policy. “The Amendments established a new system of regulation under which it is illegal for anyone to discharge pollutants into the Nation’s waters except pursuant to a permit.” Milwaukee v. Illinois, supra, at 310-311; see generally EPA v. California ex rel. State Water Resources Control Board, 426 U. S. 200 (1976). Nonetheless, “[i]n writing the enforcement procedures involving the Federal Government the Committee drew extensively . . . upon the existing enforcement provisions of the Refuse Act of 1899.” S. Rep. No. 92-414, supra, at 63. Violations of the Refuse Act have not automatically led courts to issue injunctions. See Reserve Mining Co. v. EPA, 514 F. 2d 492, 535-538 (CA8 1975); United States v. Rohm & Haas Co., 500 F. 2d 167, 175 (CA5 1974), cert. denied, 420 U. S. 962 (1975); United States v. Kennebec Log Driving Co., 491 F. 2d 562, 571 (CA1 1973), on remand, 399 F. Supp. 754, 759-760 (Me. 1975).
[320]*320III
This Court explained in Hecht Co. v. Bowles, 321 U. S. 321 (1944), that a major departure from the long tradition of equity practice should not be lightly implied. As we did there, we construe the statute at issue “in favor of that interpretation which affords a full opportunity for equity courts to treat enforcement proceedings ... in accordance with their traditional practices, as conditioned by the necessities of the public interest which Congress has sought to protect.” Id,., at 330. We do not read the FWPCA as foreclosing completely the exercise of the court’s discretion. Rather than requiring a district court to issue an injunction for any and all statutory violations, the FWPCA permits the district court to order that relief it considers necessary to secure prompt compliance with the Act. That relief can include, but is not limited to, an order of immediate cessation.
The exercise of equitable discretion, which must include the ability to deny as well as grant injunctive relief, can fully protect the range of public interests at issue at this stage in the proceedings. The District Court did not face a situation in which a permit would very likely not issue, and the requirements and objective of the statute could therefore not be vindicated if discharges were permitted to continue. Should it become clear that no permit will be issued and that compliance with the FWPCA will not be forthcoming, the statutory scheme and purpose would require the court to reconsider the balance it has struck.
Because Congress, in enacting the FWPCA, has not foreclosed the exercise of equitable discretion, the proper standard for appellate review is whether the District Court abused its discretion in denying an immediate cessation order while the Navy applied for a permit. We reverse and remand to the Court of Appeals for proceedings consistent with this opinion.
It is so ordered.