Waters of the United States (WOTUS)

"Waters of the United States" — universally abbreviated WOTUS — is the regulatory definition that determines which bodies of water the federal government can regulate under the Clean Water Act. If a water is WOTUS, you need a federal permit before discharging pollutants into it (an NPDES permit) or placing dredged or fill material in it (a Section 404 permit). If it isn't, those federal requirements don't apply, and only state law governs. That single definitional question controls jurisdiction over hundreds of millions of acres of wetlands, streams, ponds, and ditches — making WOTUS one of the most litigated regulatory definitions in American environmental law.

Current Rule (2026)

Legal Authority

• 33 U.S.C. § 1251 et seq. (Clean Water Act) — Prohibits the discharge of pollutants to "navigable waters" without a permit; authorizes EPA and Army Corps of Engineers to define the geographic scope of federal jurisdiction through regulation
• 33 U.S.C. § 1362(7) — Defines "navigable waters" as "waters of the United States, including the territorial seas"; the definitional gap between "navigable waters" and "waters of the United States" is the source of 50 years of regulatory and litigation controversy
• 40 CFR Part 120 — Current EPA/Army Corps WOTUS definition, revised post-Sackett to comply with the Supreme Court's unitary definition test
• Sackett v. EPA, 598 U.S. 651 (2023) — Held that "adjacent" wetlands are only covered by the Clean Water Act if they have a "continuous surface connection" to a jurisdictional water body; rejected EPA's "significant nexus" test established in Rapanos (2006); substantially narrowed WOTUS coverage

Key Mechanics

Waters of the United States (WOTUS) is the threshold concept determining which water bodies fall under Clean Water Act jurisdiction — including Section 402 NPDES discharge permits, Section 404 dredge-and-fill permits, and water quality standards. The definition matters enormously: filling or discharging to a WOTUS without a permit is a federal Clean Water Act violation; the same activity in a non-jurisdictional water is entirely unregulated under federal law. The statutory term "navigable waters" has never been interpreted literally — EPA and the Army Corps have long claimed jurisdiction over streams, wetlands, and other waters that flow to and affect traditional navigable waters. Sackett v. EPA (2023) fundamentally narrowed jurisdiction: wetlands are only jurisdictional if they have a continuous surface connection to a covered water body, making them "indistinguishable" from the water itself — the "significant nexus" test of Rapanos (2006) (whether wetlands have substantial hydrological effects on navigable waters) was rejected. The post-Sackett rule (40 CFR Part 120, 2023 conforming amendment) implements the Sackett standard: covered waters include traditional navigable waters, tributaries with perennial or intermittent flow, and wetlands with continuous surface connection to jurisdictional waters. Isolated wetlands, ephemeral streams, and most prairie potholes are no longer federally jurisdictional. The rule is subject to ongoing litigation challenging both its breadth (industry argues it is too broad) and its narrowness (environmental groups argue it still exceeds Sackett's holding).

What This Rule Does

40 CFR Part 120 defines "waters of the United States" for purposes of all Clean Water Act regulations — the NPDES permitting program, Section 404 dredge-and-fill permitting, Section 401 state certification, water quality standards, and oil spill liability. The definition sets the geographic scope of federal CWA jurisdiction; it does not independently prohibit or require anything, but it is the threshold question for every Clean Water Act enforcement action and permit decision.

The current definition, conforming to the Supreme Court's Sackett v. EPA (2023) decision, identifies the following categories as WOTUS:

• Traditional navigable waters — waters currently used, historically used, or susceptible to use in interstate or foreign commerce, including territorial seas
• Tributaries — rivers, streams, and similar features that contribute flow to traditional navigable waters, including perennial and intermittent streams
• Lakes and ponds of jurisdictional significance — impoundments with a continuous surface connection to navigable waters or their tributaries
• Adjacent wetlands — wetlands that have a continuous surface connection to a covered water, such that the wetlands are distinguishable only by ordinary high-water marks; under Sackett, wetlands must be directly abutting (continuously connected) to a covered water to qualify — a hydrological connection alone is insufficient

What WOTUS does not include (post-Sackett): Prior versions of the rule included wetlands with a "significant nexus" to navigable waters — meaning wetlands that significantly affect the physical, chemical, or biological integrity of covered waters, even without a continuous surface connection. The Supreme Court eliminated the significant nexus test in Sackett v. EPA (2023), effectively removing federal jurisdiction over millions of acres of isolated wetlands, ephemeral streams, and wetlands separated from navigable waters by berms, dikes, or upland terrain.

Key Provisions

• § 120.1 — Scope: establishes that Part 120 contains the definition of WOTUS for all CWA implementing regulations; cross-references CWA § 502(7) which defines "navigable waters" as "waters of the United States, including the territorial seas"
• § 120.2 — Definitions: the operative definition listing covered waters; identifies excluded features (prior converted cropland, waste treatment systems, certain groundwater, puddles, erosional features, ditches draining only non-adjacent uplands)

How It Affects You

Landowners and developers — if you want to fill a wetland, reroute a creek, or discharge into a stream on your property, the WOTUS determination is the first question. Non-WOTUS waters are outside federal jurisdiction; you may only need state permits. For covered waters, a Section 404 permit from the Army Corps of Engineers is required before any filling or discharge of dredged material. Unpermitted filling of WOTUS can trigger cleanup orders and civil penalties up to $64,618/day per violation.

Farmers — agricultural exemptions in the CWA (normal farming activities, irrigation return flows) are narrow; whether they apply depends partly on whether the affected water is WOTUS. Wetland-heavy farms in the Upper Midwest and Pacific Northwest were significantly affected by pre-Sackett WOTUS expansions. The post-Sackett rule narrows jurisdiction for isolated prairie potholes and similar features.

Industry and municipalities — any discharge of pollutants to a WOTUS requires an NPDES permit. Stormwater runoff systems, industrial outfalls, and sewage treatment plants all turn on WOTUS jurisdiction for their permit coverage.

Legal History

The WOTUS definition has been reshaped by Supreme Court decisions three times in 25 years:

• Solid Waste Agency of Northern Cook County v. Army Corps (SWANCC, 2001) — held that isolated, intrastate, non-navigable waters used by migratory birds alone do not constitute WOTUS; the Court declined to extend jurisdiction based solely on migratory bird use
• Rapanos v. United States (2006) — a fractured decision (no majority opinion) producing two competing tests: Justice Scalia's plurality required a continuous surface connection to navigable waters; Justice Kennedy's concurrence adopted the "significant nexus" test (substantial effect on integrity of navigable waters); lower courts applied Kennedy's nexus test as the controlling opinion for 17 years
• Sackett v. EPA (2023) — overruled Rapanos in a 5-4 decision; adopted Scalia's continuous surface connection test; held that WOTUS extends only to relatively permanent bodies of water and wetlands with a continuous surface connection to them; eliminated the significant nexus test entirely

Regulatory whiplash: The Obama administration's 2015 Clean Water Rule expanded WOTUS to include more tributaries and adjacent wetlands (struck down in multiple circuits). The Trump administration replaced it with the Navigable Waters Protection Rule (2020), which narrowed jurisdiction (vacated by district courts in multiple states). The Biden administration promulgated a new Revised Definition in January 2023 (88 FR 3143) — then Sackett was decided in May 2023, partially invalidating it. EPA issued a conforming amendment (88 FR 61969, Sept. 2023) to bring the regulation into compliance with Sackett.

Statutory Authority

This rule implements:

• 33 U.S.C. § 1251 — the Clean Water Act's declaration of goals and policy; the jurisdictional scope of "navigable waters" governs all CWA programs
• 33 U.S.C. § 1362(7) — defines "navigable waters" as "the waters of the United States, including the territorial seas"; WOTUS is EPA's regulatory definition implementing this statutory term

Recent Rulemakings

• 88 FR 3143 (Jan. 18, 2023) — Biden administration "Revised Definition of Waters of the United States" — expanded the significant nexus standard and tributary coverage; partially invalidated by Sackett v. EPA (May 2023)
• 88 FR 61969 (Sept. 8, 2023) — conforming amendment narrowing the definition to comply with Sackett; removed significant nexus standard; limited adjacent wetlands to those with continuous surface connection

Pending Action

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