In Carabell, the Sixth Circuit held that the nearby ditch constituted a “tributary” and thus a “water of the United States” under 33 CFR §328.3(a)(5) (2004). See 391 F. 3d, at 708–709. Likewise in Rapanos, the Sixth Circuit held that the nearby ditches were “tributaries” under §328(a)(5). 376 F. 3d, at 643. But Rapanos II also stated that, even if the ditches were not “waters of the United States,” the wetlands were “adjacent” to remote traditional navigable waters in virtue of the wetlands’ “hydrological connection” to them. See id., at 639–640. This statement reflects the practice of the Corps’ district offices, which may “assert jurisdiction over a wetland without regulating the ditch connecting it to a water of the United States.” GAO Report 23. We therefore address in this Part whether a wetland may be considered “adjacent to” remote “waters of the United States,” because of a mere hydrologic connection to them.

In Riverside Bayview, we noted the textual difficulty in including “wetlands” as a subset of “waters”: “On a purely linguistic level, it may appear unreasonable to classify ‘lands,’ wet or otherwise, as ‘waters.’” 474 U. S., at 132. We acknowledged, however, that there was an inherent ambiguity in drawing the boundaries of any “waters”:

“[T]he Corps must necessarily choose some point at which water ends and land begins. Our common experience tells us that this is often no easy task: the transition from water to solid ground is not necessarily or even typically an abrupt one. Rather, between open waters and dry land may lie shallows, marshes, mudflats, swamps, bogs—in short, a huge array of areas that are not wholly aquatic but nevertheless fall far short of being dry land. Where on this continuum to find the limit of ‘waters’ is far from obvious.” Ibid.

Because of this inherent ambiguity, we deferred to the agency’s inclusion of wetlands “actually abut[ting]” traditional navigable waters: “Faced with such a problem of defining the bounds of its regulatory authority,” we held, the agency could reasonably conclude that a wetland that “adjoin[ed]” waters of the United States is itself a part of those waters. Id., at 132, 135, and n. 9. The difficulty of delineating the boundary between water and land was central to our reasoning in the case: “In view of the breadth of federal regulatory authority contemplated by the Act itself and the inherent difficulties of defining precise bounds to regulable waters, the Corps’ ecological judgment about the relationship between waters and their adjacent wetlands provides an adequate basis for a legal judgment that adjacent wetlands may be defined as waters under the Act.” Id., at 134 (emphasis added).[10]

When we characterized the holding of Riverside Bayview in SWANCC, we referred to the close connection between waters and the wetlands that they gradually blend into: “It was the significant nexus between the wetlands and ‘navigable waters’ that informed our reading of the CWA in Riverside Bayview Homes .” 531 U. S., at 167 (emphasis added). In particular, SWANCC rejected the notion that the ecological considerations upon which the Corps relied in Riverside Bayview —and upon which the dissent repeatedly relies today, see post, at 10–11, 12, 13–14, 15, 18–19, 21–22, 24–25—provided an independent basis for including entities like “wetlands” (or “ephemeral streams”) within the phrase “the waters of the United States.” SWANCC found such ecological considerations irrelevant to the question whether physically isolated waters come within the Corps’ jurisdiction. It thus confirmed that Riverside Bayview rested upon the inherent ambiguity in defining where water ends and abutting (“adjacent”) wetlands begin, permitting the Corps’ reliance on ecological considerations only to resolve that ambiguity in favor of treating all abutting wetlands as waters. Isolated ponds were not “waters of the United States” in their own right, see 531 U. S., at 167, 171, and presented no boundary-drawing problem that would have justified the invocation of ecological factors to treat them as such.

Therefore, 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 “waters” and wetlands, are “adjacent to” such waters and covered by the Act. Wetlands with only an intermittent, physically remote hydrologic connection to “waters of the United States” do not implicate the boundary-drawing problem of Riverside Bayview, and thus lack the necessary connection to covered waters that we described as a “significant nexus” in SWANCC . 531 U. S., at 167. Thus, establishing that wetlands such as those at the Rapanos and Carabell sites are covered by the Act requires two findings: First, that the adjacent channel contains a “wate[r] of the United States,” (i.e., a relatively permanent body of water connected to traditional interstate navigable waters); and second, that the wetland has a continuous surface connection with that water, making it difficult to determine where the “water” ends and the “wetland” begins.

V

Respondents and their amici urge that such restrictions on the scope of “navigable waters” will frustrate enforcement against traditional water polluters under 33 U. S. C. §§1311 and 1342. Because the same definition of “navigable waters” applies to the entire statute, respondents contend that water polluters will be able to evade the permitting requirement of §1342(a) simply by discharging their pollutants into noncovered intermittent watercourses that lie upstream of covered waters. See Tr. of Oral Arg. 74–75.

That is not so. Though we do not decide this issue, there is no reason to suppose that our construction today significantly affects the enforcement of §1342, inasmuch as lower courts applying §1342 have not characterized intermittent channels as “waters of the United States.” The Act does not forbid the “addition of any pollutant directly to navigable waters from any point source,” but rather the “addition of any pollutant to navigable waters.” §1362(12)(A) (emphasis added); §1311(a). Thus, from the time of the CWA’s enactment, lower courts have held that the discharge into intermittent channels of any pollutant that naturally washes downstream likely violates §1311(a), even if the pollutants discharged from a point source do not emit “directly into” covered waters, but pass “through conveyances” in between. United States v. Velsicol Chemical Corp., 438 F. Supp. 945, 946–947 (WD Tenn. 1976) (a municipal sewer system separated the “point source” and covered navigable waters). See also Sierra Club v. El Paso Gold Mines, Inc., 421 F. 3d 1133, 1137, 1141 (CA10 2005) (2.5 miles of tunnel separated the “point source” and “navigable waters”).

In fact, many courts have held that such upstream, intermittently flowing channels themselves constitute “point sources” under the Act. The definition of “point source” includes “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). We have held that the Act “makes plain that a point source need not be the original source of the pollutant; it need only convey the pollutant to ‘navigable waters.’” South Fla. Water Management Dist. v. Miccosukee Tribe, 541 U. S. 95, 105 (2004). Cases holding the intervening channel to be a point source include United States v. Ortiz, 427 F. 3d 1278, 1281 (CA10 2005) (a storm drain that carried flushed chemicals from a toilet to the Colorado River was a “point source”), and Dague v. Burlington, 935 F. 2d 1343, 1354–1355 (CA2 1991) (a culvert connecting two bodies of navigable water was a “point source”), rev’d on other grounds, 505 U. S. 557 (1992). Some courts have even adopted both the “indirect discharge” rationale and the “point source” rationale in the alternative, applied to the same facts. See, e.g., Concerned Area Residents for Environment v. Southview Farm, 34 F. 3d 114, 118–119 (CA2 1994). On either view, however, the lower courts have seen no need to classify the intervening conduits as “waters of the United States.”

In contrast to the pollutants normally covered by the permitting requirement of §1342(a), “dredged or fill material,” which is typically deposited for the sole purpose of staying put, does not normally wash downstream,[11] and thus does not normally constitute an “addition . . . to navigable waters” when deposited in upstream isolated wetlands. §§1344(a), 1362(12). The Act recognizes this distinction by providing a separate permitting program for such discharges in §1344(a). It does not appear, therefore, that the interpretation we adopt today significantly reduces the scope of §1342 of the Act.

Respondents also urge that the narrower interpretation of “waters” will impose a more difficult burden of proof in enforcement proceedings under §§1311(a) and 1342(a), by requiring the agency to demonstrate the downstream flow of the pollutant along the intermittent channel to traditional “waters.” See Tr. of Oral Arg. 57. But, as noted above, the lower courts do not generally rely on characterization of intervening channels as “waters of the United States” in applying §1311 to the traditional pollutants subject to §1342. Moreover, the proof of downstream flow of pollutants required under §1342 appears substantially similar, if not identical, to the proof of a hydrologic connection that would be required, on the Sixth Circuit’s theory of jurisdiction, to prove that an upstream channel or wetland is a “wate[r] of the United States.” See Rapanos II, 376 F. 3d, at 639. Compare, e.g., App. to Pet. for Cert. in No. 04–1034, at B11, B20, B26 (testimony of hydrologic connections based on observation of surface water connections), with Southview Farm, supra, at 118–121 (testimony of discharges based on observation of the flow of polluted water). In either case, the agency must prove that the contaminant-laden waters ultimately reach covered waters.

Finally, respondents and many amici admonish that narrowing the definition of “the waters of the United States” will hamper federal efforts to preserve the Nation’s wetlands. It is not clear that the state and local conservation efforts that the CWA explicitly calls for, see 33 U. S. C. §1251(b), are in any way inadequate for the goal of preservation. In any event, a Comprehensive National Wetlands Protection Act is not before us, and the “wis[dom]” of such a statute, post, at 19 (opinion of Stevens, J.), is beyond our ken. What is clear, however, is that Congress did not enact one when it granted the Corps jurisdiction over only “the waters of the United States.”

VI

In an opinion long on praise of environmental protection and notably short on analysis of the statutory text and structure, the dissent would hold that “the waters of the United States” include any wetlands “adjacent” (no matter how broadly defined) to “tributaries” (again, no matter how broadly defined) of traditional navigable waters. For legal support of its policy-laden conclusion, the dissent relies exclusively on two sources: “[o]ur unanimous opinion in Riverside Bayview,” post, at 6; and “Congress’ deliberate acquiescence in the Corps’ regulations in 1977,” post, at 11. Each of these is demonstrably inadequate to support the apparently limitless scope that the dissent would permit the Corps to give to the Act.

A

The dissent’s assertion that Riverside Bayview “squarely controls these cases,” post, at 6, is wholly implausible. First, Riverside Bayview could not possibly support the dissent’s acceptance of the Corps’ inclusion of dry beds as “tributaries,” post, at 19, because the definition of tributaries was not at issue in that case. Riverside Bayview addressed only the Act’s inclusion of wetlands abutting navigable-in-fact waters, and said nothing at all about what non-navigable tributaries the Act might also cover.

Riverside Bayview likewise provides no support for the dissent’s complacent acceptance of the Corps’ definition of “adjacent,” which (as noted above) has been extended beyond reason to include, inter alia, the 100-year flood-plain of covered waters. See supra, at 9. The dissent notes that Riverside Bayview quoted without comment the Corps’ description of “adjacent” wetlands as those “that form the border of or are in reasonable proximity to other waters of the United States.” Post, at 8 (citing 474 U. S., at 134 (quoting 42 Fed. Reg. 37128)). As we have already discussed, this quotation provides no support for the inclusion of physically unconnected wetlands as covered “waters.” See supra, at 22–23, n. 10. The dissent relies principally on a footnote in Riverside Bayview recognizing that “‘not every adjacent wetland is of great importance to the environment of adjoining bodies of water,’” and that all “‘adjacent’” wetlands are nevertheless covered by the Act, post, at 8 (quoting 474 U. S., at 135, n. 9). Of course, this footnote says nothing to support the dissent’s broad definition of “adjacent”—quite the contrary, the quoted sentence uses “adjacent” and “adjoining” interchangeably, and the footnote qualifies a sentence holding that the wetland was covered “ [b]ecause ” it “actually abut[ted] on a navigable waterway.” Id., at 135 (emphasis added). Moreover, that footnote’s assertion that the Act may be interpreted to include even those adjoining wetlands that are “lacking in importance to the aquatic environment,” id., at 135, n. 9, confirms that the scope of ambiguity of “the waters of the United States” is determined by a wetland’s physical connection to covered waters, not its ecological relationship thereto.

The dissent reasons (1) that Riverside Bayview held that “the waters of the United States” include “adjacent wetlands,” and (2) we must defer to the Corps’ interpretation of the ambiguous word “adjacent.” Post, at 20–21. But this is mere legerdemain. The phrase “adjacent wetlands” is not part of the statutory definition that the Corps is authorized to interpret, which refers only to “the waters of the United States,” 33 U. S. C. §1362(7).[12] In expounding the term “adjacent” as used in Riverside Bayview, we are explaining our own prior use of that word to interpret the definitional phrase “the waters of the United States.” However ambiguous the term may be in the abstract, as we have explained earlier, “adjacent” as used in Riverside Bayview is not ambiguous between “physically abutting” and merely “nearby.” See supra, at 21–23.

The dissent would distinguish SWANCC on the ground that it “had nothing to say about wetlands,” post, at 9— i.e., it concerned “isolated ponds ” rather than isolated wetlands . This is the ultimate distinction without a difference. If isolated “permanent and seasonal ponds of varying size . . . and depth,” 531 U. S., at 163—which, after all, might at least be described as “waters” in their own right—did not constitute “waters of the United States,” a fortiori, isolated swampy lands do not constitute “waters of the United States.” See also 474 U. S., at 132. As the author of today’s dissent has written, “[i]f, as I believe, actually navigable waters lie at the very heart of Congress’ commerce power and ‘isolated,’ nonnavigable waters lie closer to . . . the margin, ‘isolated wetlands,’ which are themselves only marginally ‘waters,’ are the most marginal category of ‘waters of the United States’ potentially covered by the statute.” 531 U. S., at 187, n. 13 (Stevens, J., dissenting).

The only other ground that the dissent offers to distinguish SWANCC is that, unlike the ponds in SWANCC, the wetlands in these cases are “adjacent to navigable bodies of water and their tributaries”—where “adjacent” may be interpreted whonows-how broadly. It is not clear why roughly defined physical proximity should make such a difference—without actual abutment, it raises no boundary-drawing ambiguity, and it is undoubtedly a poor proxy for ecological significance. In fact, though the dissent is careful to restrict its discussion to wetlands “adjacent” to tributaries, its reasons for including those wetlands are strictly ecological—such wetlands would be included because they “serve . . . important water quality roles,” post, at 11, and “play important roles in the watershed,” post, at 18–19. This reasoning would swiftly overwhelm SWANCC altogether; after all, the ponds at issue in SWANCC could, no less than the wetlands in these cases, “offer ‘nesting, spawning, rearing and resting sites for aquatic or land species,’” and “‘serve as valuable storage areas for storm and flood waters,’” post, at 9–10. The dissent’s exclusive focus on ecological factors, combined with its total deference to the Corps’ ecological judgments, would permit the Corps to regulate the entire country as “waters of the United States.”

B

Absent a plausible ground in our case law for its sweeping position, the dissent relies heavily on “Congress’ deliberate acquiescence in the Corps’ regulations in 1977,” post, at 11—noting that “[w]e found [this acquiescence] significant in Riverside Bayview,” and even “acknowledged in SWANCC ” that we had done so, post, at 12. SWANCC “acknowledged” that Riverside Bayview had relied on congressional acquiescence only to criticize that reliance. It reasserted in no uncertain terms our oft-expressed skepticism towards reading the tea leaves of congressional inaction:

“Although we have recognized congressional acquiescence to administrative interpretations of a statute in some situations, we have done so with extreme care. Failed legislative proposals are a particularly dangerous ground on which to rest an interpretation of a prior statute. . . . The relationship between the actions and inactions of the 95th Congress and the intent of the 92d Congress in passing [§1344(a)] is also considerably attenuated. Because subsequent history is less illuminating than the contemporaneous evidence, respondents face a difficult task in overcoming the plain text and import of [§1344(a)].” 531 U. S., at 169 (citations, internal quotation marks, and footnote omitted).

Congress takes no governmental action except by legislation. What the dissent refers to as “Congress’ deliberate acquiescence” should more appropriately be called Congress’s failure to express any opinion. We have no idea whether the Members’ failure to act in 1977 was attributable to their belief that the Corps’ regulations were correct, or rather to their belief that the courts would eliminate any excesses, or indeed simply to their unwillingness to confront the environmental lobby. To be sure, we have sometimes relied on congressional acquiescence when there is evidence that Congress considered and rejected the “ precise issue” presented before the Court, Bob Jones Univ. v. United States, 461 U. S. 574, 600 (1983) (emphasis added). However, “[a]bsent such overwhelming evidence of acquiescence, we are loath to replace the plain text and original understanding of a statute with an amended agency interpretation.” SWANCC, supra, at 169, n. 5 (emphasis added).

The dissent falls far short of producing “overwhelming evidence” that Congress considered and failed to act upon the “precise issue” before the Court today—namely, what constitutes an “adjacent” wetland covered by the Act. Citing Riverside Bayview ’s account of the 1977 debates, the dissent claims nothing more than that Congress “conducted extensive debates about the Corps’ regulatory jurisdiction over wetlands [and] rejected efforts to limit that jurisdiction . . . .” Post, at 11. In fact, even that vague description goes too far. As recounted in Riverside Bayview, the 1977 debates concerned a proposal to “limi[t] the Corps’ authority under [§1344] to waters navigable in fact and their adjacent wetlands (defined as wetlands periodically inundated by contiguous navigable waters),” 474 U. S., at 136. In rejecting this proposal, Congress merely failed to enact a limitation of “waters” to include only navigable-in-fact waters—an interpretation we affirmatively reject today, see supra, at 12—and a definition of wetlands based on “periodi[c] inundat[ion]” that appears almost nowhere in the briefs or opinions of these cases.[13]No plausible interpretation of this legislative inaction can construe it as an implied endorsement of every jot and tittle of the Corps’ 1977 regulations. In fact, Riverside Bayview itself relied on this legislative inaction only as “at least some evidence of the reasonableness” of the agency’s inclusion of adjacent wetlands under the Act, 474 U. S., at 137, and for the observation that “even those who would have restricted the reach of the Corps’ jurisdiction” would not have excised adjacent wetlands, ibid. Both of these conclusions are perfectly consistent with our interpretation, and neither illuminates the disputed question of what constitutes an “adjacent” wetland.

C

In a curious appeal to entrenched Executive error, the dissent contends that “the appropriateness of the Corps’ 30-year implementation of the Clean Water Act should be addressed to Congress or the Corps rather than to the Judiciary.” Post, at 14; see also post, at 2, 22. Surely this is a novel principle of administrative law—a sort of 30-year adverse possession that insulates disregard of statutory text from judicial review. It deservedly has no precedent in our jurisprudence. We did not invoke such a principle in SWANCC, when we invalidated one aspect of the Corps’ implementation.

The dissent contends that “[b]ecause there is ambiguity in the phrase ‘waters of the United States’ and because interpreting it broadly to cover such ditches and streams advances the purpose of the Act, the Corps’ approach should command our deference.” Post, at 19. Two defects in a single sentence: “[W]aters of the United States” is in some respects ambiguous. The scope of that ambiguity, however, does not conceivably extend to whether storm drains and dry ditches are “waters,” and hence does not support the Corps’ interpretation. And as for advancing “the purpose of the Act”: We have often criticized that last resort of extravagant interpretation, noting that no law pursues its purpose at all costs, and that the textual limitations upon a law’s scope are no less a part of its “purpose” than its substantive authorizations. See, e.g., Director, Office of Workers’ Compensation Programs v. Newport News Shipbuilding & Dry Dock Co., 514 U. S. 122, 135– 136 (1995).

Finally, we could not agree more with the dissent’s statement, post, at 14, that “[w]hether the benefits of particular conservation measures outweigh their costs is a classic question of public policy that should not be answered by appointed judges.” Neither, however, should it be answered by appointed officers of the Corps of Engineers in contradiction of congressional direction. It is the dissent’s opinion, and not ours, which appeals not to a reasonable interpretation of enacted text, but to the great environmental benefits that a patently unreasonable interpretation can achieve. We have begun our discussion by mentioning, to be sure, the high costs imposed by that interpretation—but they are in no way the basis for our decision, which rests, plainly and simply, upon the limited meaning that can be borne by the phrase “waters of the United States.”

VII

Justice KENNEDY’s opinion concludes that our reading of the Act “is inconsistent with its text, structure, and purpose.” Post, at 19. His own opinion, however, leaves the Act’s “text” and “structure” virtually unaddressed, and rests its case upon an interpretation of the phrase “significant nexus,” ibid., which appears in one of our opinions.

To begin with, Justice KENNEDY’s reading of “significant nexus” bears no easily recognizable relation to either the case that used it (SWANCC) or to the earlier case that that case purported to be interpreting (Riverside Bayview) . To establish a “significant nexus,” Justice Kennedy would require the Corps to “establish . . . on a case-by-case basis” that wetlands adjacent to nonnavigable tributaries “significantly affect the chemical, physical, and biological integrity of other covered waters more readily understood as ‘navigable.’” Post, at 25, 23. This standard certainly does not come from Riverside Bayview, which explicitly rejected such case-by-case determinations of ecological significance for the jurisdictional question whether a wetland is covered, holding instead that all physically connected wetlands are covered. 474 U. S., at 135, n. 9. It is true enough that one reason for accepting that physical-connection criterion was the likelihood that a physically connected wetland would have an ecological effect upon the adjacent waters. But case-by-case determination of ecological effect was not the test . Likewise, that test cannot be derived from SWANCC ’s characterization of Riverside Bayview, which emphasized that the wetlands which possessed a “significant nexus” in that earlier case “actually abutted on a navigable waterway,” 531 U. S., at 167, and which specifically rejected the argument that physically unconnected ponds could be included based on their ecological connection to covered waters. In fact, Justice Kennedy acknowledges that neither Riverside Bayview nor SWANCC required, for wetlands abutting navigable-in-fact waters, the case-by-case ecological determination that he proposes for wetlands that neighbor nonnavigable tributaries. See post, at 23. Thus, Justice Kennedy misreads SWANCC’s “significant nexus” statement as mischaracterizing Riverside Bayview to adopt a case-by-case test of ecological significance; and then transfers that standard to a context that Riverside Bayview expressly declined to address (namely, wetlands nearby non-navigable tributaries); while all the time conceding that this standard does not apply in the context that Riverside Bayview did address (wetlands abutting navigable waterways). Truly, this is “turtles all the way down.”[14]

But misreading our prior decisions is not the principal problem. The principal problem is reading them in utter isolation from the text of the Act. One would think, after reading Justice KENNEDY’s exegesis, that the crucial provision of the text of the CWA was a jurisdictional requirement of “significant nexus” between wetlands and navigable waters. In fact, however, that phrase appears nowhere in the Act, but is taken from SWANCC ’s cryptic characterization of the holding of Riverside Bayview . Our interpretation of the phrase is both consistent with those opinions and compatible with what the Act does establish as the jurisdictional criterion: “waters of the United States.” Wetlands are “waters of the United States” if they bear the “significant nexus” of physical connection, which makes them as a practical matter indistinguishable from waters of the United States. What other nexus could conceivably cause them to be “waters of the United States”? Justice KENNEDY’s test is that they, “either alone or in combination with similarly situated lands in the region, significantly affect the chemical, physical, and biological integrity of other covered waters more readily understood as ‘navigable,’” post, at 23 (emphasis added). But what possible linguistic usage would accept that whatever (alone or in combination) affects waters of the United States is waters of the United States?

Only by ignoring the text of the statute and by assuming that the phrase of SWANCC (“significant nexus”) can properly be interpreted in isolation from that text does Justice Kennedy reach the conclusion he has arrived at. Instead of limiting its meaning by reference to the text it was applying, he purports to do so by reference to what he calls the “purpose” of the statute. Its purpose is to clean up the waters of the United States, and therefore anything that might “significantly affect” the purity of those waters bears a “significant nexus” to those waters, and thus (he never says this, but the text of the statute demands that he mean it) is those waters. This is the familiar tactic of substituting the purpose of the statute for its text, freeing the Court to write a different statute that achieves the same purpose. To begin with, as we have discussed earlier, clean water is not the only purpose of the statute. So is the preservation of primary state responsibility for ordinary land-use decisions. 33 U. S. C. §1251(b). Justice KENNEDY’s test takes no account of this purpose. More fundamentally, however, the test simply rewrites the statute, using for that purpose the gimmick of “significant nexus.” It would have been an easy matter for Congress to give the Corps jurisdiction over all wetlands (or, for that matter, all dry lands) that “significantly affect the chemical, physical, and biological integrity of” waters of the United States. It did not do that, but instead explicitly limited jurisdiction to “waters of the United States.”

Justice KENNEDY’s disposition would disallow some of the Corps’ excesses, and in that respect is a more moderate flouting of statutory command than Justice Stevens’.[15] In another respect, however, it is more extreme. At least Justice Stevens can blame his implausible reading of the statute upon the Corps. His error con- sists of giving that agency more deference than reason permits. Justice Kennedy, however, has devised his new statute all on his own. It purports to be, not a grudging acceptance of an agency’s close-to-the-edge expansion of its own powers, but rather the most reasonable interpretation of the law. It is far from that, unless whatever affects waters is waters.

VIII

Because the Sixth Circuit applied the wrong standard to determine if these wetlands are covered “waters of the United States,” and because of the paucity of the record in both of these cases, the lower courts should determine, in the first instance, whether the ditches or drains near each wetland are “waters” in the ordinary sense of containing a relatively permanent flow; and (if they are) whether the wetlands in question are “adjacent” to these “waters” in the sense of possessing a continuous surface connection that creates the boundary-drawing problem we addressed in Riverside Bayview .

* * *

We vacate the judgments of the Sixth Circuit in both No. 04–1034 and No. 04–1384, and remand both cases for further proceedings.

It is so ordered.

Chief Justice Roberts, concurring.

Five years ago, this Court rejected the position of the Army Corps of Engineers on the scope of its authority to regulate wetlands under the Clean Water Act, 86 Stat. 816, as amended, 33 U. S. C. §1251 et seq . Solid Waste Agency of Northern Cook Cty. v. Army Corps of Engineers, 531 U. S. 159 (2001) (SWANCC) . The Corps had taken the view that its authority was essentially limitless; this Court explained that such a boundless view was inconsistent with the limiting terms Congress had used in the Act. Id., at 167–174.

In response to the SWANCC decision, the Corps and the Environmental Protection Agency (EPA) initiated a rule-making to consider “issues associated with the scope of waters that are subject to the Clean Water Act (CWA), in light of the U. S. Supreme Court decision in [SWANCC] .” 68 Fed. Reg. 1991 (2003). The “goal of the agencies” was “to develop proposed regulations that will further the public interest by clarifying what waters are subject to CWA jurisdiction and affording full protection to these waters through an appropriate focus of Federal and State resources consistent with the CWA.” Ibid.

Agencies delegated rulemaking authority under a statute such as the Clean Water Act are afforded generous leeway by the courts in interpreting the statute they are entrusted to administer. See Chevron U. S. A. Inc. v. Natural Resources Defense Council, Inc., 467 U. S. 837, 842–845 (1984). Given the broad, somewhat ambiguous, but nonetheless clearly limiting terms Congress employed in the Clean Water Act, the Corps and the EPA would have enjoyed plenty of room to operate in developing some notion of an outer bound to the reach of their authority.

The proposed rulemaking went nowhere. Rather than refining its view of its authority in light of our decision in SWANCC, and providing guidance meriting deference under our generous standards, the Corps chose to adhere to its essentially boundless view of the scope of its power. The upshot today is another defeat for the agency.

It is unfortunate that no opinion commands a majority of the Court on precisely how to read Congress’ limits on the reach of the Clean Water Act. Lower courts and regulated entities will now have to feel their way on a case-by-case basis. This situation is certainly not unprecedented. See Grutter v. Bollinger, 539 U. S. 306, 325 (2003) (discussing Marks v. United States, 430 U. S. 188 (1977)). What is unusual in this instance, perhaps, is how readily the situation could have been avoided.[*]

Justice Kennedy, concurring in the judgment.

These consolidated cases require the Court to decide whether the term “navigable waters” in the Clean Water Act extends to wetlands that do not contain and are not adjacent to waters that are navigable in fact. In Solid Waste Agency of Northern Cook Cty. v. Army Corps of Engineers, 531 U. S. 159 (2001) (SWANCC), the Court held, under the circumstances presented there, that to constitute “‘navigable waters’” under the Act, a water or wetland must possess a “significant nexus” to waters that are or were navigable in fact or that could reasonably be so made. Id., at 167, 172. In the instant cases neither the plurality opinion nor the dissent by Justice Stevens chooses to apply this test; and though the Court of Appeals recognized the test’s applicability, it did not consider all the factors necessary to determine whether the lands in question had, or did not have, the requisite nexus. In my view the cases ought to be remanded to the Court of Appeals for proper consideration of the nexus requirement.

I

Although both the plurality opinion and the dissent by Justice Stevens (hereinafter the dissent) discuss the background of these cases in some detail, a further discussion of the relevant statutes, regulations, and facts may clarify the analysis suggested here.

A

The “objective” of the Clean Water Act (Act), is “to restore and maintain the chemical, physical, and biological integrity of the Nation’s waters.” 33 U. S. C. §1251(a). To that end, the statute, among other things, prohibits “the discharge of any pollutant by any person” except as provided in the Act. §1311(a). As relevant here, the term “discharge of a pollutant” means “any addition of any pollutant to navigable waters from any point source.” §1362(12). The term “pollutant” is defined as “dredged spoil, solid waste, incinerator residue, sewage, garbage, sewage sludge, munitions, chemical wastes, biological materials, radioactive materials, heat, wrecked or discarded equipment, rock, sand, cellar dirt and industrial, municipal, and agricultural waste discharged into water.” §1362(6). The Secretary of the Army, acting through the Chief of Engineers of the Army Corps of Engineers, may issue permits for “discharge of dredged or fill material into the navigable waters at specified disposal sites.” §§1344(a), (c), (d); but see §1344(f) (categorically exempting certain forms of “discharge of dredged or fill material” from regulation under §1311(a)). Pursuant to §1344(g), States with qualifying programs may assume certain aspects of the Corps’ permitting responsibility. Apart from dredged or fill material, pollutant discharges require a permit from the Environmental Protection Agency (EPA), which also oversees the Corps’ (and qualifying States’) permitting decisions. See §§1311(a), 1342(a), 1344(c). Discharge of pollutants without an appropriate permit may result in civil or criminal liability. See §1319.

The statutory term to be interpreted and applied in the two instant cases is the term “navigable waters.” The outcome turns on whether that phrase reasonably describes certain Michigan wetlands the Corps seeks to regulate. Under the Act “[t]he term ‘navigable waters’ means the waters of the United States, including the territorial seas.” §1362(7). In a regulation the Corps has construed the term “waters of the United States” to include not only waters susceptible to use in interstate commerce—the traditional understanding of the term “navigable waters of the United States,” see, e.g., United States v. Appalachian Elec. Power Co., 311 U. S. 377, 406– 408 (1940); The Daniel Ball, 10 Wall. 557, 563–564 (1871)— but also tributaries of those waters and, of particular relevance here, wetlands adjacent to those waters or their tributaries. 33 CFR §§328.3(a)(1), (5), (7) (2005). The Corps views tributaries as within its jurisdiction if they carry a perceptible “ordinary high water mark.” §328.4(c); 65 Fed. Reg. 12823 (2000). An ordinary high-water mark is a “line on the shore established by the fluctuations of water and indicated by physical characteristics such as clear, natural line impressed on the bank, shelving, changes in the character of soil, destruction of terrestrial vegetation, the presence of litter and debris, or other appropriate means that consider the characteristics of the surrounding areas.” 33 CFR §328.3(e).

Contrary to the plurality’s description, ante, at 2–3, 15, wetlands are not simply moist patches of earth. They are defined as “those areas that are inundated or saturated by surface or ground water at a frequency and duration sufficient to support, and that under normal circumstances do support, a prevalence of vegetation typically adapted for life in saturated soil conditions. Wetlands generally include swamps, marshes, bogs, and similar areas.” §328.3(b). The Corps’ Wetlands Delineation Manual, including over 100 pages of technical guidance for Corps officers, interprets this definition of wetlands to require: (1) prevalence of plant species typically adapted to saturated soil conditions, determined in accordance with the United States Fish and Wildlife Service’s National List of Plant Species that Occur in Wetlands; (2) hydric soil, meaning soil that is saturated, flooded, or ponded for sufficient time during the growing season to become anaerobic, or lacking in oxygen, in the upper part; and (3) wetland hydrology, a term generally requiring continuous inundation or saturation to the surface during at least five percent of the growing season in most years. See Wetlands Research Program Technical Report Y–87–1 (on-line edition), pp. 12–34 (Jan. 1987), http://www.saj.usace.army.mil/permit/documents/87manual.pdf (all Internet material as visited June 16, 2006, and available in Clerk of Court’s case file). Under the Corps’ regulations, wetlands are adjacent to tributaries, and thus covered by the Act, even if they are “separated from other waters of the United States by man-made dikes or barriers, natural river berms, beach dunes and the like.” §328.3(c).

B

The first consolidated case before the Court, Rapanos v. United States, No. 04–1034, relates to a civil enforcement action initiated by the United States in the United States District Court for the Eastern District of Michigan against the owners of three land parcels near Midland, Michigan. The first parcel, known as the Salzburg site, consists of roughly 230 acres. The District Court, applying the Corps’ definition of wetlands, found based on expert testimony that the Salzburg site included 28 acres of wetlands. The District Court further found that “the Salzburg wetlands have a surface water connection to tributaries of the Kawkawlin River which, in turn, flows into the Saginaw River and ultimately into Lake Huron.” App. to Pet. for Cert. B11. Water from the site evidently spills into the Hoppler Drain, located just north of the property, which carries water into the Hoppler Creek and thence into the Kawkawlin River, which is navigable. A state official testified that he observed carp spawning in a ditch just north of the property, indicating a direct surface-water connection from the ditch to the Saginaw Bay of Lake Huron.