June 19, 2006[*]

Argued February 21, 2006

ON WRIT OF CERTIORARI TO THE UNITED STATES COURT OF APPEALS FOR THE SIXTH CIRCUIT

As relevant here, the Clean Water Act (CWA or Act) makes it unlawful to discharge dredged or fill material into “navigable waters” without a permit, 33 U. S. C. §§1311(a), 1342(a), and defines “navigable waters” as “the waters of the United States, including the territorial seas,” §1362(7). The Army Corps of Engineers (Corps), which issues permits for the discharge of dredged or fill material into navigable waters, interprets “the waters of the United States” expansively to include not only traditional navigable waters, 33 CFR §328.3(a)(1), but also other defined waters, §328.3(a)(2), (3); “[t]ributaries” of such waters, §328.3(a)(5); and wetlands “adjacent” to such waters and tributaries, §328.3(a)(7). “[A]djacent” wetlands include those “bordering, contiguous [to], or neighboring” waters of the United States even when they are “separated from [such] waters . . . by man-made dikes . . . and the like.” §328.3(c).

These cases involve four Michigan wetlands lying near ditches or man-made drains that eventually empty into traditional navigable waters. In No. 04–1034, the United States brought civil enforcement proceedings against the Rapanos petitioners, who had backfilled three of the areas without a permit. The District Court found federal jurisdiction over the wetlands because they were adjacent to “waters of the United States” and held petitioners liable for CWA violations. Affirming, the Sixth Circuit found federal jurisdiction based on the sites’ hydrologic connections to the nearby ditches or drains, or to more remote navigable waters. In No. 04–1384, the Carabell petitioners were denied a permit to deposit fill in a wetland that was separated from a drainage ditch by an impermeable berm. The Carabells sued, but the District Court found federal jurisdiction over the site. Affirming, the Sixth Circuit held that the wetland was adjacent to navigable waters.

Held: The judgments are vacated, and the cases are remanded.

No. 04–1034, 376 F. 3d 629, and No. 04–1384, 391 F. 3d 704, vacated and remanded.

Justice Scalia, joined by The Chief Justice, Justice Thomas, and Justice Alito, concluded:

1. The phrase “the waters of the United States” includes only those relatively permanent, standing or continuously flowing bodies of water “forming geographic features” that are described in ordinary parlance as “streams,” “oceans, rivers, [and] lakes,” Webster’s New International Dictionary 2882 (2d ed.), and does not include channels through which water flows intermittently or ephemerally, or channels that periodically provide drainage for rainfall. The Corps’ expansive interpretation of that phrase is thus not “based on a permissible construction of the statute.” Chevron U. S. A. Inc. v. Natural Resources Defense Council, Inc., 467 U. S. 837, 843. Pp. 12–21.

(a)  While the meaning of “navigable waters” in the CWA is broader than the traditional definition found in The Daniel Ball, 10 Wall. 557, see Solid Waste Agency of Northern Cook Cty. v. Army Corps of Engineers, 531 U. S. 159, 167 (SWANCC); United States v. Riverside Bayview Homes, Inc., 474 U. S. 121, 133, the CWA authorizes federal jurisdiction only over “waters.” The use of the definite article “the” and the plural number “waters” show plainly that §1362(7) does not refer to water in general, but more narrowly to water “[a]s found in streams,” “oceans, rivers, [and] lakes,” Webster’s New International Dictionary 2882 (2d ed.). Those terms all connote relatively permanent bodies of water, as opposed to ordinarily dry channels through which water occasionally or intermittently flows. Pp. 12–15.

(b)  The Act’s use of the traditional phrase “navigable waters” further confirms that the CWA confers jurisdiction only over relatively permanent bodies of water. Traditionally, such “waters” included only discrete bodies of water, and the term still carries some of its original substance, SWANCC, supra, at 172. This Court’s subsequent interpretation of “the waters of the United States” in the CWA likewise confirms this limitation. See, e.g., Riverside Bayview, supra, at 131. And the CWA itself categorizes the channels and conduits that typically carry intermittent flows of water separately from “navigable waters,” including them in the definition of “ ‘point sources,’” 33 U. S. C. §1362(14). Moreover, only the foregoing definition of “waters” is consistent with CWA’s stated policy “to recognize, preserve, and protect the primary responsibilities and rights of the States . . . to plan the development and use . . . of land and water resources . . . .” §1251(b). In addition, “the waters of the United States” hardly qualifies as the clear and manifest statement from Congress needed to authorize intrusion into such an area of traditional state authority as land-use regulation; and to authorize federal action that stretches the limits of Congress’s commerce power. See SWANCC, supra, at 173. Pp. 15–21.

2.  A wetland may not be considered “adjacent to” remote “waters of the United States” based on a mere hydrologic connection. Riverside Bayview rested on an inherent ambiguity in defining where the “water” ends and its abutting (“adjacent”) wetlands begin, permitting the Corps to rely on ecological considerations only to resolve that ambiguity in favor of treating all abutting wetlands as waters. Isolated ponds are not “waters of the United States” in their own right, see SWANCC, supra, at 167, 171, and present no boundary-drawing problem justifying the invocation of such ecological factors. Thus, only those wetlands with a continuous surface connection to bodies that are “waters of the United States” in their own right, so that there is no clear demarcation between the two, are “adjacent” to such waters and covered by the Act. Establishing coverage of the Rapanos and Carabell sites requires finding that the adjacent channel contains a relatively permanent “wate[r] of the United States,” and that each wetland has a continuous surface connection to that water, making it difficult to determine where the water ends and the wetland begins. Pp. 21–24. 3.Because the Sixth Circuit applied an incorrect standard to determine whether the wetlands at issue are covered “waters,” and because of the paucity of the record, the cases are remanded for further proceedings. P. 39.

Justice Kennedy concluded that the Sixth Circuit correctly recognized that a water or wetland constitutes “navigable waters” under the Act if it possesses a “significant nexus” to waters that are navigable in fact or that could reasonably be so made, Solid Waste Agency of Northern Cook Cty. v. Army Corps of Engineers, 531 U. S. 159, 167, 172 (SWANCC), but did not consider all the factors necessary to determine that the lands in question had, or did not have, the requisite nexus. United States v. Riverside Bayview Homes, Inc., 474 U. S. 121, and SWANCC establish the framework for the inquiry here. The nexus required must be assessed in terms of the Act’s goals and purposes. Congress enacted the law to “restore and maintain the chemical, physical, and biological integrity of the Nation’s waters,” 33 U. S. C. §1251(a), and it pursued that objective by restricting dumping and filling in “waters of the United States,” §§1311(a), 1362(12). The rationale for the Act’s wetlands regulation, as the Corps has recognized, is that wetlands can perform critical functions related to the integrity of other waters—such as pollutant trapping, flood control, and runoff storage. 33 C. F. R. §320.4(b)(2). Accordingly, wetlands possess the requisite nexus, and thus come within the statutory phrase “navigable waters,” if the wetlands, alone or in combination with similarly situated lands in the region, significantly affect the chemical, physical, and biological integrity of other covered waters understood as navigable in the traditional sense. When, in contrast, their effects on water quality are speculative or insubstantial, they fall outside the zone fairly encompassed by the term “navigable waters.” Because the Corps’ theory of jurisdiction in these cases— adjacency to tributaries, however remote and insubstantial—goes beyond the Riverside Bayview holding, its assertion of jurisdiction cannot rest on that case. The breadth of the Corps’ existing standard for tributaries—which seems to leave room for regulating drains, ditches, and streams remote from any navigable-in-fact water and carrying only minor water-volumes toward it—precludes that standard’s adoption as the determinative measure of whether adjacent wetlands are likely to play an important role in the integrity of an aquatic system comprising navigable waters as traditionally understood. Absent more specific regulations, the Corps must establish a significant nexus on a case-by-case basis when seeking to regulate wetlands based on adjacency to nonnavigable tributaries, in order to avoid unreasonable applications of the Act. In the instant cases the record contains evidence pointing to a possible significant nexus, but neither the agency nor the reviewing courts considered the issue in these terms. Thus, the cases should be remanded for further proceedings. Pp. 1–30.

Scalia, J., announced the judgment of the Court, and delivered an opinion, in which Roberts, C. J., and Thomas and Alito, JJ., joined. Roberts, C. J., filed a concurring opinion. Kennedy, J., filed an opinion concurring in the judgment. Stevens, J., filed a dissenting opinion, in which Souter, Ginsburg, and Breyer, JJ., joined. Breyer, J., filed a dissenting opinion.

Justice Scalia announced the judgment of the Court, and delivered an opinion, in which The Chief Justice, Justice Thomas, and Justice Alito join.

In April 1989, petitioner John A. Rapanos backfilled wetlands on a parcel of land in Michigan that he owned and sought to develop. This parcel included 54 acres of land with sometimes-saturated soil conditions. The nearest body of navigable water was 11 to 20 miles away. 339 F. 3d 447, 449 (CA6 2003) (Rapanos I) . Regulators had informed Mr. Rapanos that his saturated fields were “waters of the United States,” 33 U. S. C. §1362(7), that could not be filled without a permit. Twelve years of criminal and civil litigation ensued.

The burden of federal regulation on those who would deposit fill material in locations denominated “waters of the United States” is not trivial. In deciding whether to grant or deny a permit, the U. S. Army Corps of Engineers (Corps) exercises the discretion of an enlightened despot, relying on such factors as “economics,” “aesthetics,” “recreation,” and “in general, the needs and welfare of the people,” 33 CFR §320.4(a) (2004).[1] The average applicant for an individual permit spends 788 days and $271,596 in completing the process, and the average applicant for a nationwide permit spends 313 days and $28,915—not counting costs of mitigation or design changes. Sunding & Zilberman, The Economics of Environmental Regulation by Licensing: An Assessment of Recent Changes to the Wetland Permitting Process, 42 Natural Resources J. 59, 74–76 (2002). “[O]ver $1.7 billion is spent each year by the private and public sectors obtaining wetlands permits.” Id., at 81. These costs cannot be avoided, because the Clean Water Act “impose[s] criminal liability,” as well as steep civil fines, “on a broad range of ordinary industrial and commercial activities.” Hanousek v. United States, 528 U. S. 1102, 1103 (2000) (Thomas, J., dissenting from denial of certiorari). In this litigation, for example, for backfilling his own wet fields, Mr. Rapanos faced 63 months in prison and hundreds of thousands of dollars in criminal and civil fines. See United States v. Rapanos, 235 F. 3d 256, 260 (CA6 2000).

The enforcement proceedings against Mr. Rapanos are a small part of the immense expansion of federal regulation of land use that has occurred under the Clean Water Act— without any change in the governing statute—during the past five Presidential administrations. In the last three decades, the Corps and the Environmental Protection Agency (EPA) have interpreted their jurisdiction over “the waters of the United States” to cover 270-to-300 million acres of swampy lands in the United States—including half of Alaska and an area the size of California in the lower 48 States. And that was just the beginning. The Corps has also asserted jurisdiction over virtually any parcel of land containing a channel or conduit—whether man-made or natural, broad or narrow, permanent or ephemeral— through which rainwater or drainage may occasionally or intermittently flow. On this view, the federally regulated “waters of the United States” include storm drains, roadside ditches, ripples of sand in the desert that may contain water once a year, and lands that are covered by floodwa-ters once every 100 years. Because they include the land containing storm sewers and desert washes, the statutory “waters of the United States” engulf entire cities and immense arid wastelands. In fact, the entire land area of the United States lies in some drainage basin, and an endless network of visible channels furrows the entire surface, containing water ephemerally wherever the rain falls. Any plot of land containing such a channel may potentially be regulated as a “water of the United States.”

I

Congress passed the Clean Water Act (CWA or Act) in 1972. The Act’s stated objective is “to restore and maintain the chemical, physical, and biological integrity of the Nation’s waters.” 86 Stat. 816, 33 U. S. C. §1251(a). The Act also states that “[i]t is the policy of Congress to recognize, preserve, and protect the primary responsibilities and rights of States to prevent, reduce, and eliminate pollution, to plan the development and use (including restoration, preservation, and enhancement) of land and water resources, and to consult with the Administrator in the exercise of his authority under this chapter.” §1251(b).

One of the statute’s principal provisions is 33 U. S. C. §1311(a), which provides that “the discharge of any pollutant by any person shall be unlawful.” “The discharge of a pollutant” is defined broadly to include “any addition of any pollutant to navigable waters from any point source,” §1362(12), and “pollutant” is defined broadly to include not only traditional contaminants but also solids such as “dredged spoil, . . . rock, sand, [and] cellar dirt,” §1362(6). And, most relevant here, the CWA defines “navigable waters” as “the waters of the United States, including the territorial seas.” §1362(7).

The Act also provides certain exceptions to its prohibition of “the discharge of any pollutant by any person.” §1311(a). Section 1342(a) authorizes the Administrator of the EPA to “issue a permit for the discharge of any pollutant, . . . notwithstanding section 1311(a) of this title.” Section 1344 authorizes the Secretary of the Army, acting through the Corps, to “issue permits . . . for the discharge of dredged or fill material into the navigable waters at specified disposal sites.” §1344(a), (d). It is the discharge of “dredged or fill material”—which, unlike traditional water pollutants, are solids that do not readily wash downstream—that we consider today.

For a century prior to the CWA, we had interpreted the phrase “navigable waters of the United States” in the Act’s predecessor statutes to refer to interstate waters that are “navigable in fact” or readily susceptible of being rendered so. The Daniel Ball, 10 Wall. 557, 563 (1871); see also United States v. Appalachian Elec. Power Co., 311 U. S. 377, 406 (1940). After passage of the CWA, the Corps initially adopted this traditional judicial definition for the Act’s term “navigable waters.” See 39 Fed. Reg. 12119, codified at 33 CFR §209.120(d)(1) (1974); see also Solid Waste Agency of Northern Cook Cty. v. Army Corps of Engineers, 531 U. S. 159, 168 (2001) (SWANCC). After a District Court enjoined these regulations as too narrow, Natural Resources Defense Council, Inc. v. Callaway, 392 F. Supp. 685, 686 (DC 1975), the Corps adopted a far broader definition. See 40 Fed. Reg. 31324–31325 (1975); 42 Fed. Reg. 37144 (1977). The Corps’ new regulations deliberately sought to extend the definition of “the waters of the United States” to the outer limits of Congress’s commerce power. See id., at 37144, n. 2.

The Corps’ current regulations interpret “the waters of the United States” to include, in addition to traditional interstate navigable waters, 33 CFR §328.3(a)(1) (2004), “[a]ll interstate waters including interstate wetlands,” §328.3(a)(2); “[a]ll other waters such as intrastate lakes, rivers, streams (including intermittent streams), mudflats, sandflats, wetlands, sloughs, prairie potholes, wet meadows, playa lakes, or natural ponds, the use, degradation or destruction of which could affect interstate or foreign commerce,” §328.3(a)(3); “[t]ributaries of [such] waters,” §328.3(a)(5); and “[w]etlands adjacent to [such] waters [and tributaries] (other than waters that are themselves wetlands),” §328.3(a)(7). The regulation defines “adjacent” wetlands as those “bordering, contiguous [to], or neighboring” waters of the United States. §328.3(c). It specifically provides that “[w]etlands separated from other waters of the United States by man-made dikes or barriers, natural river berms, beach dunes and the like are ‘adjacent wetlands.’” Ibid.

We first addressed the proper interpretation of 33 U. S. C. §1362(7)’s phrase “the waters of the United States” in United States v. Riverside Bayview Homes, Inc., 474 U. S. 121 (1985). That case concerned a wetland that “was adjacent to a body of navigable water,” because “the area characterized by saturated soil conditions and wetland vegetation extended beyond the boundary of respondent’s property to . . . a navigable waterway.” Id., at 131; see also 33 CFR §328.3(b) (2004). Noting that “the transition from water to solid ground is not necessarily or even typically an abrupt one,” and that “the Corps must necessarily choose some point at which water ends and land begins,” 474 U. S., at 132, we upheld the Corps’ interpretation of “the waters of the United States” to include wetlands that “actually abut[ted] on” traditional navigable waters. Id., at 135.

Following our decision in Riverside Bayview, the Corps adopted increasingly broad interpretations of its own regulations under the Act. For example, in 1986, to “clarify” the reach of its jurisdiction, the Corps announced the so-called “Migratory Bird Rule,” which purported to extend its jurisdiction to any intrastate waters “[w]hich are or would be used as habitat” by migratory birds. 51 Fed. Reg. 41217; see also SWANCC, supra, at 163–164. In addition, the Corps interpreted its own regulations to include “ephemeral streams” and “drainage ditches” as “tributaries” that are part of the “waters of the United States,” see 33 CFR §328.3(a)(5), provided that they have a perceptible “ordinary high water mark” as defined in §328.3(e). 65 Fed. Reg. 12823 (2000). This interpretation extended “the waters of the United States” to virtually any land feature over which rainwater or drainage passes and leaves a visible mark—even if only “the presence of litter and debris.” 33 CFR §328.3(e). See also U. S. General Accounting Office, Report to the Chairman, Subcommittee on Energy Policy, Natural Resources and Regulating Affairs, Committee on Government Reform, House of Representatives, Waters and Wetlands: Corps of Engineers Needs to Evaluate Its District Office Practices in Determining Jurisdiction, GAO–04–297, pp. 20–22 (Feb. 2004) (hereinafter GAO Report), http://www.gao.gov/new.items/d04297.pdf (all Internet materials as visited June 9, 2006, and available in Clerk of Court’s case file). Prior to our decision in SWANCC, lower courts upheld the application of this expansive definition of “tributaries” to such entities as storm sewers that contained flow to covered waters during heavy rainfall, United States v. Eidson, 108 F. 3d 1336, 1340–1342 (CA111997), and dry arroyos connected to remote waters through the flow of groundwater over “centuries,” Quivira Mining Co. v. EPA, 765 F. 2d 126, 129 (CA10 1985).

In SWANCC, we considered the application of the Corps’ “Migratory Bird Rule” to “an abandoned sand and gravel pit in northern Illinois.” 531 U. S., at 162. Observing that “[i]t was the significant nexus between the wetlands and ‘navigable waters’ that informed our reading of the CWA in Riverside Bayview,” id., at 167 (emphasis added), we held that Riverside Bayview did not establish “that the jurisdiction of the Corps extends to ponds that are not adjacent to open water.” 531 U. S., at 168 (emphasis deleted). On the contrary, we held that “nonnavigable, isolated, intrastate waters,” id., at 171—which, unlike the wetlands at issue in Riverside Bayview, did not “actually abu[t] on a navigable waterway,” 531 U. S., at 167—were not included as “waters of the United States.”

Following our decision in SWANCC, the Corps did not significantly revise its theory of federal jurisdiction under §1344(a). The Corps provided notice of a proposed rule-making in light of SWANCC, 68 Fed. Reg. 1991 (2003), but ultimately did not amend its published regulations. Because SWANCC did not directly address tributaries, the Corps notified its field staff that they “should continue to assert jurisdiction over traditional navigable waters . . . and, generally speaking, their tributary systems (and adjacent wetlands).” 68 Fed. Reg. 1998. In addition, because SWANCC did not overrule Riverside Bayview, the Corps continues to assert jurisdiction over waters “‘neighboring’” traditional navigable waters and their tributaries. 68 Fed. Reg. 1997 (quoting 33 CFR §328.3(c) (2003)).

Even after SWANCC, the lower courts have continued to uphold the Corps’ sweeping assertions of jurisdiction over ephemeral channels and drains as “tributaries.” For example, courts have held that jurisdictional “tributaries” include the “intermittent flow of surface water through approximately 2.4 miles of natural streams and manmade ditches (paralleling and crossing under I–64),” Treacy v. Newdunn Assoc., 344 F. 3d 407, 410 (CA4 2003); a “roadside ditch” whose water took “a winding, thirty-two-mile path to the Chesapeake Bay,” United States v. Deaton, 332 F. 3d 698, 702 (CA4 2003); irrigation ditches and drains that intermittently connect to covered waters, Community Assn. for Restoration of Environment v. Henry Bosma Dairy, 305 F. 3d 943, 954–955 (CA9 2002); Headwaters, Inc. v. Talent Irrigation Dist., 243 F. 3d 526, 534 (CA9 2001); and (most implausibly of all) the “washes and arroyos” of an “arid development site,” located in the middle of the desert, through which “water courses . . . during periods of heavy rain,” Save Our Sonoran, Inc. v. Flowers, 408 F. 3d 1113, 1118 (CA9 2005).[2]

These judicial constructions of “tributaries” are not outliers. Rather, they reflect the breadth of the Corps’ determinations in the field. The Corps’ enforcement practices vary somewhat from district to district because “the definitions used to make jurisdictional determinations” are deliberately left “vague.” GAO Report 26; see also id., at 22. But district offices of the Corps have treated, as “waters of the United States,” such typically dry land features as “arroyos, coulees, and washes,” as well as other “channels that might have little water flow in a given year.” Id., at 20–21. They have also applied that definition to such manmade, intermittently flowing features as “drain tiles, storm drains systems, and culverts.” Id., at 24 (footnote omitted).

In addition to “tributaries,” the Corps and the lower courts have also continued to define “adjacent” wetlands broadly after SWANCC . For example, some of the Corps’ district offices have concluded that wetlands are “adjacent” to covered waters if they are hydrologically connected “through directional sheet flow during storm events,” GAO Report 18, or if they lie within the “100-year floodplain” of a body of water—that is, they are connected to the navigable water by flooding, on average, once every 100 years, id., at 17, and n. 16. Others have concluded that presence within 200 feet of a tributary automatically renders a wetland “adjacent” and jurisdictional. Id., at 19. And the Corps has successfully defended such theories of “adjacency” in the courts, even after SWANCC ’s excision of “isolated” waters and wetlands from the Act’s coverage. One court has held since SWANCC that wetlands separated from flood control channels by 70-foot-wide berms, atop which ran maintenance roads, had a “significant nexus” to covered waters because, inter alia, they lay “within the 100 year floodplain of tidal waters.” Baccarat Fremont Developers, LLC v. Army Corps of Engineers, 425 F. 3d 1150, 1152, 1157 (CA9 2005). In one of the cases before us today, the Sixth Circuit held, in agreement with “[t]he majority of courts,” that “while a hydrological connection between the non-navigable and navigable waters is required, there is no ‘direct abutment’ requirement” under SWANCC for “‘adjacency.’” 376 F. 3d 629, 639 (2004) (Rapanos II) . And even the most insubstantial hydrologic connection may be held to constitute a “signifi- cant nexus.” One court distinguished SWANCC on the ground that “a molecule of water residing in one of these pits or ponds [in SWANCC ] could not mix with molecules from other bodies of water”—whereas, in the case before it, “water molecules currently present in the wetlands will inevitably flow towards and mix with water from connecting bodies,” and “[a] drop of rainwater landing in the Site is certain to intermingle with water from the [nearby river].” United States v. Rueth Development Co., 189 F. Supp. 2d 874, 877–878 (ND Ind. 2002).

II

In these consolidated cases, we consider whether four Michigan wetlands, which lie near ditches or man-made drains that eventually empty into traditional navigable waters, constitute “waters of the United States” within the meaning of the Act. Petitioners in No. 04–1034, the Ra-panos and their affiliated businesses, deposited fill material without a permit into wetlands on three sites near Midland, Michigan: the “Salzburg site,” the “Hines Road site,” and the “Pine River site.” The wetlands at the Salzburg site are connected to a man-made drain, which drains into Hoppler Creek, which flows into the Kawkawlin River, which empties into Saginaw Bay and Lake Huron. See Brief for United States in No. 04–1034, p. 11; 339 F. 3d, at 449. The wetlands at the Hines Road site are connected to something called the “Rose Drain,” which has a surface connection to the Tittabawassee River. App. to Pet. for Cert. in No. 04–1034, pp. A23, B20. And the wetlands at the Pine River site have a surface connection to the Pine River, which flows into Lake Huron. Id., at A23–A24, B26. It is not clear whether the connections between these wetlands and the nearby drains and ditches are continuous or intermittent, or whether the nearby drains and ditches contain continuous or merely occasional flows of water.

The United States brought civil enforcement proceedings against the Rapanos petitioners. The District Court found that the three described wetlands were “within federal jurisdiction” because they were “adjacent to other waters of the United States,” and held petitioners liable for violations of the CWA at those sites. Id., at B32–B35. On appeal, the United States Court of Appeals for the Sixth Circuit affirmed, holding that there was federal jurisdiction over the wetlands at all three sites because “there were hydrological connections between all three sites and corresponding adjacent tributaries of navigable waters.” 376 F. 3d, at 643.

Petitioners in No. 04–1384, the Carabells, were denied a permit to deposit fill material in a wetland located on a triangular parcel of land about one mile from Lake St. Clair. A man-made drainage ditch runs along one side of the wetland, separated from it by a 4-foot-wide man-made berm. The berm is largely or entirely impermeable to water and blocks drainage from the wetland, though it may permit occasional overflow to the ditch. The ditch empties into another ditch or a drain, which connects to Auvase Creek, which empties into Lake St. Clair. See App. to Pet. for Cert. in No. 04–1384, pp. 2a–3a.

After exhausting administrative appeals, the Carabell petitioners filed suit in the District Court, challenging the exercise of federal regulatory jurisdiction over their site. The District Court ruled that there was federal jurisdiction because the wetland “is adjacent to neighboring tributaries of navigable waters and has a significant nexus to ‘waters of the United States.’” Id., at 49a. Again the Sixth Circuit affirmed, holding that the Carabell wetland was “adjacent” to navigable waters. 391 F. 3d 704, 708 (2004) (Carabell).

We granted certiorari and consolidated the cases, 546 U. S. ___ (2005), to decide whether these wetlands constitute “waters of the United States” under the Act, and if so, whether the Act is constitutional.

III

The Rapanos petitioners contend that the terms “navigable waters” and “waters of the United States” in the Act must be limited to the traditional definition of The Daniel Ball, which required that the “waters” be navigable in fact, or susceptible of being rendered so. See 10 Wall., at 563. But this definition cannot be applied wholesale to the CWA. The Act uses the phrase “navigable waters” as a defined term, and the definition is simply “the waters of the United States.” 33 U. S. C. §1362(7). Moreover, the Act provides, in certain circumstances, for the substitution of state for federal jurisdiction over “navigable waters . . . other than those waters which are presently used, or are susceptible to use in their natural condition or by reasonable improvement as a means to transport interstate or foreign commerce . . . including wetlands adjacent thereto.” §1344(g)(1) (emphasis added). This provision shows that the Act’s term “navigable waters” includes something more than traditional navigable waters. We have twice stated that the meaning of “navigable waters” in the Act is broader than the traditional understanding of that term, SWANCC, 531 U. S., at 167; Riverside Bayview, 474 U. S., at 133.[3] We have also emphasized, however, that the qualifier “navigable” is not devoid of significance, SWANCC, supra, at 172.

We need not decide the precise extent to which the qualifiers “navigable” and “of the United States” restrict the coverage of the Act. Whatever the scope of these qualifiers, the CWA authorizes federal jurisdiction only over “waters.” 33 U. S. C. §1362(7). The only natural definition of the term “waters,” our prior and subsequent judicial constructions of it, clear evidence from other provisions of the statute, and this Court’s canons of construction all confirm that “the waters of the United States” in §1362(7) cannot bear the expansive meaning that the Corps would give it.

The Corps’ expansive approach might be arguable if the CSA defined “navigable waters” as “water of the United States.” But “the waters of the United States” is something else. The use of the definite article (“the”) and the plural number (“waters”) show plainly that §1362(7) does not refer to water in general. In this form, “the waters” refers more narrowly to water “[a]s found in streams and bodies forming geographical features such as oceans, rivers, [and] lakes,” or “the flowing or moving masses, as of waves or floods, making up such streams or bodies.” Webster’s New International Dictionary 2882 (2d ed. 1954) (hereinafter Webster’s Second).[4] On this definition, “the waters of the United States” include only relatively permanent, standing or flowing bodies of water.[5] The definition refers to water as found in “streams,” “oceans,” “rivers,” “lakes,” and “bodies” of water “forming geographical features.” Ibid. All of these terms connote continuously present, fixed bodies of water, as opposed to ordinarily dry channels through which water occasionally or intermittently flows. Even the least substantial of the definition’s terms, namely “streams,” connotes a continuous flow of water in a permanent channel—especially when used in company with other terms such as “rivers,” “lakes,” and “oceans.”[6] None of these terms encompasses transitory puddles or ephemeral flows of water.

The restriction of “the waters of the United States” to exclude channels containing merely intermittent or ephemeral flow also accords with the commonsense understanding of the term. In applying the definition to “ephemeral streams,” “wet meadows,” storm sewers and culverts, “directional sheet flow during storm events,” drain tiles, man-made drainage ditches, and dry arroyos in the middle of the desert, the Corps has stretched the term “waters of the United States” beyond parody. The plain language of the statute simply does not authorize this “Land Is Waters” approach to federal jurisdiction.

In addition, the Act’s use of the traditional phrase “navigable waters” (the defined term) further confirms that it confers jurisdiction only over relatively permanent bodies of water. The Act adopted that traditional term from its predecessor statutes. See SWANCC, 531 U. S., at 180 (Stevens, J., dissenting). On the traditional understanding, “navigable waters” included only discrete bodies of water. For example, in The Daniel Ball, we used the terms “waters” and “rivers” interchangeably. 10 Wall., at 563. And in Appalachian Electric, we consistently referred to the “navigable waters” as “waterways.” 311 U. S., at 407– 409. Plainly, because such “waters” had to be navigable in fact or susceptible of being rendered so, the term did not include ephemeral flows. As we noted in SWANCC, the traditional term “navigable waters”—even though defined as “the waters of the United States”—carries some of its original substance: “[I]t is one thing to give a word limited effect and quite another to give it no effect whatever.” 531 U. S., at 172. That limited effect includes, at bare minimum, the ordinary presence of water.

Our subsequent interpretation of the phrase “the waters of the United States” in the CWA likewise confirms this limitation of its scope. In Riverside Bayview, we stated that the phrase in the Act referred primarily to “rivers, streams, and other hydrographic features more conventionally identifiable as ‘waters’” than the wetlands adjacent to such features. 474 U. S., at 131 (emphasis added). We thus echoed the dictionary definition of “waters” as referring to “streams and bodies forming geographical features such as oceans, rivers, [and] lakes.” Webster’s Second 2882 (emphasis added). Though we upheld in that case the inclusion of wetlands abutting such a “hydro-graphic featur[e]”—principally due to the difficulty of drawing any clear boundary between the two, see 474 U. S., at 132; Part IV, infra —nowhere did we suggest that “the waters of the United States” should be expanded to include, in their own right, entities other than “hydro-graphic features more conventionally identifiable as ‘waters.’” Likewise, in both Riverside Bayview and SWANCC, we repeatedly described the “navigable waters” covered by the Act as “open water” and “open waters.” See Riverside Bayview, supra, at 132, and n. 8, 134; SWANCC, supra, at 167, 172. Under no rational interpretation are typically dry channels described as “ open waters.”

Most significant of all, the CWA itself categorizes the channels and conduits that typically carry intermittent flows of water separately from “navigable waters,” by including them in the definition of “‘point source.’” The Act defines “‘point source’” as “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). It also defines “‘discharge of a pollutant’” as “any addition of any pollutant to navigable waters from any point source.” §1362(12)(A) (emphases added). The definitions thus conceive of “point sources” and “navigable waters” as separate and distinct categories. The definition of “discharge” would make little sense if the two categories were significantly overlapping. The separate classification of “ditch[es], channel[s], and conduit[s]”—which are terms ordinarily used to describe the watercourses through which intermittent waters typically flow—shows that these are, by and large, not “waters of the United States.”[7]

Moreover, only the foregoing definition of “waters” is consistent with the CWA’s stated “policy of Congress to recognize, preserve, and protect the primary responsibilities and rights of the States to prevent, reduce, and eliminate pollution, [and] to plan the development and use (including restoration, preservation, and enhancement) of land and water resources . . . .” §1251(b). This statement of policy was included in the Act as enacted in 1972, see 86 Stat. 816, prior to the addition of the optional state administration program in the 1977 amendments, see 91 Stat. 1601. Thus the policy plainly referred to something beyond the subsequently added state administration program of 33 U. S. C. §1344(g)–(l). But the expansive theory advanced by the Corps, rather than “preserv[ing] the primary rights and responsibilities of the States,” would have brought virtually all “plan[ning of] the development and use . . . of land and water resources” by the States under federal control. It is therefore an unlikely reading of the phrase “the waters of the United States.”[8]

Even if the phrase “the waters of the United States” were ambiguous as applied to intermittent flows, our own canons of construction would establish that the Corps’ interpretation of the statute is impermissible. As we noted in SWANCC, the Government’s expansive interpretation would “result in a significant impingement of the States’ traditional and primary power over land and water use.” 531 U. S., at 174. Regulation of land use, as through the issuance of the development permits sought by petitioners in both of these cases, is a quintessential state and local power. See FERC v. Mississippi, 456 U. S. 742, 768, n. 30 (1982); Hess v. Port Authority Trans-Hudson Corporation, 513 U. S. 30, 44 (1994). The extensive federal jurisdiction urged by the Government would authorize the Corps to function as a de facto regulator of immense stretches of intrastate land—an authority the agency has shown its willingness to exercise with the scope of discretion that would befit a local zoning board. See 33 CFR §320.4(a)(1) (2004). We ordinarily expect a “clear and manifest” statement from Congress to authorize an unprecedented intrusion into traditional state authority. See BFP v. Resolution Trust Corporation, 511 U. S. 531, 544 (1994). The phrase “the waters of the United States” hardly qualifies.

Likewise, just as we noted in SWANCC, the Corps’ interpretation stretches the outer limits of Congress’s commerce power and raises difficult questions about the ultimate scope of that power. See 531 U. S., at 173. (In developing the current regulations, the Corps consciously sought to extend its authority to the farthest reaches of the commerce power. See 42 Fed. Reg. 37127 (1977).) Even if the term “the waters of the United States” were ambiguous as applied to channels that sometimes host ephemeral flows of water (which it is not), we would expect a clearer statement from Congress to authorize an agency theory of jurisdiction that presses the envelope of constitutional validity. See Edward J. DeBartolo Corp. v. Florida Gulf Coast Building & Constr. Trades Council, 485 U. S. 568, 575 (1988).[9]

In sum, on its only plausible interpretation, the phrase “the waters of the United States” includes only those relatively permanent, standing or continuously flowing bodies of water “forming geographic features” that are described in ordinary parlance as “streams[,] . . . oceans, rivers, [and] lakes.” See Webster’s Second 2882. The phrase does not include channels through which water flows intermittently or ephemerally, or channels that periodically provide drainage for rainfall. The Corps’ expansive interpretation of the “the waters of the United States” is thus not “based on a permissible construction of the statute.” Chevron U. S. A. Inc. v. Natural Resources Defense Council, Inc., 467 U. S. 837, 843 (1984).