Updated Definition of “Waters of the United States” by EPA & DoA - Nov. 2025

Or, “Why I’m Sad About Marshes/What To Do About It/Why We Got Here”

Call of the Wild Classmate’s Feet Hanging Off a Storm Drain
Somewhere on Bear Mountain
2017

Call of the Wild Classmate’s Feet Hanging Off a Storm Drain, Somewhere on Bear Mountain, 2017

Last Updated: 12.03.2025

My Thoughts:

On November 20, 2025, the proposed rule Updated Definition of "Waters of the United States" was published in the Federal Register (FR). The 45-day comment period will close on January 5, 2026. From today, we have 33 days to make some noise to Federal government to secure the protection of ephemeral waterways of the United States.

This most recent EPA/Army Corps interpretation of the Clean Water Act (CWA) proposed the “WOTUS Rule,” that would lock in a much narrower, more Sackett-style definition of “waters of the United States” (or, WOTUS) than most prior eras of CWA interpretation, especially compared to the 2015 Clean Water Rule and the 2023 Biden rule. It does this by fully embracing “relatively permanent” and “continuous surface connection” wetland litmus tests, dropping “significant nexus,” and explicitly cutting out certain ecosystem categories (e.g., waters that are jurisdictional only because they cross state lines).

The WOTUS ruling has been advertised by the EPA to citizens as an America-first legislative interpretation to strengthen “cooperative federalism” and bring back “American industry, energy producers, the technology sector, farmers, ranchers, developers, businesses, and landowners,” or the main sources of wetland pollution.

This interpretation is also explicitly under the jurisdiction of the Department of Defense (DoD) as they partners with the EPA to implement the CWA particularly through the U.S. Army Corps of Engineers. The Corps issues permits and makes jurisdictional determinations for projects affecting waters of the United States, a function directly tied to the definition of WOTUS established by the rule. While the EPA sets the overall definition, the DoD, via the Corps, is responsible for its practical implementation and enforcement, making their roles a shared responsibility.

The implications for the new WOTUS Rule have the potential to cause drastic negative ripple effects for the health of American land, water, and both animal and human communities amidst an already crucial time for preserving the delicate web of ecosystems that are US wetlands.

What You Can Do:

Further Education:

Harvard Environmental & Energy Law Program

Union of Concerned Scientists (UCS)

Waterkeeper Alliance

“Defining Waters of the United States (WOTUS)” tracker page

“EPA Proposes Striking Wetlands Protections, Risking Water Quality Across U.S.”

“EPA’s Narrowed Definition of WOTUS Threatens Water Quality”

A legal-analysis hub that tracks changes to WOTUS over time; summary of the 2025 proposed rule, breakdown of key definitions (e.g. “relatively permanent,” “continuous surface connection,” tributary, exclusions), and links to underlying documents.

A science- and conservation-oriented critique of the 2025 proposal, highlighting potential environmental and water-quality impacts of narrowing protections; good for understanding ecological risks and climate-resilience implications.

Provides a civil-society / grassroots — rather than purely academic or legal — perspective; clear explanations of how the proposed changes could affect wetlands, streams, drinking water, and habitat, especially in vulnerable or flood-prone areas.

Scratchpad Notes (Not for Public Use)

Evolution of WOTUS Definitions (2015-2025)
In the last decade, the US interpretation of WOTUS has changed significantly between administrations. Here’s a simple timeline of key changes:
2015 Clean Water Rule (Obama)

2020 Navigable Waters Protection Rule (Trump)

2023 Conforming Rule (Biden, post-Sackett)

2025 Proposed Rule (Trump) – narrow, explicitly Sackett-centric, with new exclusions and tight definitions

More on Sackett v. EPA (2023)
Basics of the Case:

Michael and Chantell Sackett owned a small residential lot near Priest Lake, Idaho.
They began backfilling their land with dirt and rock to build a home.
EPA said their lot contained federally protected wetlands hydrologically connected to the lake.
EPA ordered them to stop and restore the property.
The Sacketts challenged EPA’s jurisdiction, arguing the wetlands weren’t WOTUS.

The Question At Hand:
When do wetlands count as “waters of the United States” (WOtUS) under the Clean Water Act?

The Ruling:

The Supereme Court ruled 5-4 that only wetlands with a “continuous surface connection” to a “relatively permanent: body of water are federally protected.
The Court also threw out the “significant nexus” test that had been used for almost two decades to consider wetlands protected if they significantly affect downstream navigable waters (even if not directly touching).

What Does it Mean:
The outcomes of the case massively narrowed federal water protection - including the following ecosystems:

Wetlands separated from a river by a berm, levee, or road
Many seasonal or intermittent wetlands
Ephemeral streams in arid states
Isolated wetlands that still play ecological roles but lack a visible surface connection.

States can still regulate the above ecosystems, but the EPA cannot.

Why it Matters:
Sackett is now the controlling legal standard for wetlands under the Clean Water Act. It’s precedence has had ripple effects throughout the US including:

This is the narrowest interpretation in the CWA’s 50-year history
EPA updated it’s regulations in 2023 and has now proposed a further narrowing under WOTUS rule to comply.
Thousands of wetlands and ephemeral streams lost federal protection unless states choose to regulate them.

Crazy Facts That Made Me Sad About This Case:

It is plausible that more than half — and possibly over 80% — of formerly federally protected wetlands are no longer protected under a strict reading of Sackett.
Millions of acres of wetlands — likely 17 million to 90 million acres — are at risk of losing federal protections.
For many states, such as Illinois, the share of wetlands losing protection may be 70%+.
A large portion of non-perennial streams, headwaters, ephemeral channels, and isolated wetlands — previously regulated — may now be excluded, potentially stripping protections from up to 80% of stream miles.

This means wetlands are covered only if they are essentially indistinguishable from the adjacent lake/stream/river—the water must literally touch.

The Court threw out the “significant nexus” test, which had been used for nearly two decades.
That test said wetlands are protected if they significantly affect downstream navigable waters (even if not directly touching).

The decision massively narrowed federal water protections. Examples of waters no longer covered:

Wetlands separated from a river by a berm, levee, or road
Many seasonal or intermittent wetlands
Ephemeral streams in arid states
Isolated wetlands that still play ecological roles but lack a visible surface connection

States can still regulate these—but EPA cannot.

Glossary of Terms:

*WOTUS: an acronym for Waters of the United States
**Sackett-style: The 2023 Sacket vs. EPA trial concluded that only wetlands with a continuous surface connection to a “relatively permanent” body of water are federally protected.

Sources Considered:

U.S. Environmental Protection Agency. Updated Definition of "Waters of the United States" (Nov. 20, 2025), https://www.epa.gov/wotus/updated-definition-waters-united-states

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