Wondering about WOTUS? Here are some answers to basic questions

Defining waters of the U.S. has changed over the years through court decisions and policy updates under President Barack Obama and President Donald Trump. The EPA and U.S. Army Corps of Engineers are working on a new definition.

A stream and a barbed-wire fence along a farm field.
Farmers are concerned that the Waters of the U.S. definition could include any water on their farms, such as livestock ponds, that would be regulated by EPA.
Michelle Rook / Agweek

What is WOTUS? 

WOTUS stands for “waters of the U.S.” The term “waters of the U.S.” appears in the federal Clean Water Act of 1972 that empowers the Environmental Protection Agency and the Army Corps of Engineers with protecting those waters. But the act does not clearly define what is covered by WOTUS, it does mention both “navigable” and “interstate” waters.

So why is WOTUS a big deal? 

The Clean Water Act gives the federal government decision making power on changes to the environment that might affect those waters of the U.S. Those changes might include anything that discharges into those waters, filling in, draining or physically altering one of those waters. Building and road projects are two big areas affected by WOTUS.

Defining what waters are included under WOTUS helps determine the scope of federal authority. And that definition has changed in recent years. That leaves landowners, property developers and local governments unsure of what they can and can’t do with a piece of property.


Who decides how it is defined?

The EPA and Army Corps of Engineers, often referred to in WOTUS discussions as “the agencies,” are in charge of that definition. But there have been legal challenges forcing the agencies to make some changes.

Those agencies also report to the president, so who is president obviously influences the WOTUS rules a lot. In 2015, under President Barack Obama, the WOTUS definition was expanded under the Clean Water Rule, giving the federal government more authority. But court challenges, including one led by the North Dakota attorney general, kept the Obama rule from being enforced nationwide. The rule changed again under President Donald Trump, when what is called the Navigable Waters Protection Rule was put in place. But a court ruling in Arizona kept that rule from being used.

Now the agencies and administration of President Joe Biden are working on a new rule. On Dec 7, 2021, a proposal was posted on the Federal Register . They are taking comments on the proposed rule until Feb. 7.  To comment online, go here:

What is the Biden administration proposing?  

The Biden administration is proposing to go back to the definition used before the 2015 changes by the Obama administration, while making provisions for some Supreme Court rulings regarding WOTUS.

From the Federal Register on the proposed rule, the agencies interpret the term “waters of the United States” to include:

  • Traditional navigable waters, interstate waters, and the territorial seas, and their adjacent wetlands. 
  • Most impoundments (such as reservoirs) of the above “waters of the United States.” 
  • Tributaries to traditional navigable waters, interstate waters, the territorial seas, and impoundments that meet either the relatively permanent standard or the significant nexus standard.
  • Wetlands adjacent to impoundments and tributaries, that meet either the relatively permanent standard or the significant nexus standard.
  • “Other waters” that meet either the relatively permanent standard or the significant nexus standard. 

Two key terms are the “relatively permanent standard” and “significant nexus,” both originating from the Supreme Court opinions in the 2006 Rapanos case.
From the Federal Register:


  • The “relatively permanent standard” means waters that are relatively permanent, standing or continuously flowing and waters with a continuous surface connection to such waters. 
  • The “significant nexus standard” means waters that either alone or in combination with similarly situated waters in the region, significantly affect the chemical, physical, or biological integrity of traditional navigable waters, interstate waters, or the territorial seas (the “foundational waters”). 

Note that there are many more details to the proposed rule than just these bullet points.
To learn more about ag groups' stance on the proposed rule, click here.

How is the new proposal different from the Trump era rule?

One big difference is that the proposed rule includes the “significant nexus” test, mentioned above. A nexus basically means a connection.

Under the Navigable Waters Protection Rule enacted by the Trump administration, there was no “nexus” criteria for including a body of water under federal jurisdiction.

These nexus determinations will need to be on a case-by-case basis and could include waters such as prairie potholes and “ephemeral” or intermittent streams.

The Trump rule relied more heavily on the “relatively permanent” standard. Supporters of the Trump rule said it provided more clarity, but critics said it did not provide enough protection.

From the Arizona ruling that kept the Trump rule from being used:

“The (Navigable Waters Protection Rule) strictly defines “tributaries” and “adjacent wetlands,” and it categorically excludes certain features from the definition of “navigable waters,” including “ephemeral streams.”


How is the proposed rule different from the Obama era rule?

As you would expect, the Biden proposal is much closer to Obama-era rule than the Trump rule. Some critics say the Biden proposal relies even more heavily on the significant nexus test, providing less certainty on what is jurisdictional.

The Obama-era more clearly gave the EPA and Army Corps of Engineers broad jurisdiction over upstream waters and intermittent and ephemeral streams.

Some ag groups have expressed concern about a lack of specified “exemptions” from federal regulations that had been spelled out previously, including for ponds for livestock.

Another areas where the agencies are looking for comment is what “interstate” means. Some tribal governments want waters that border or flow through both tribal and non-tribal lands to be classified as interstate waters.

How is it different from the pre-Obama era rule? 

The pre-2015 guidelines outlined “significantly affects” means something that must alter chemical, physical and biological integrity of downstream foundational waters. The proposed rule changes it to alter the “chemical, physical or biological integrity of downstream foundational waters.” This change will only require that one of those be at risk for that water to be considered under federal jurisdiction.

Under the “other waters” section, the proposed rule amends the pre-2015 guidelines to delete provisions referring to authority over activities that “could affect interstate or foreign commerce” and replace them with the relatively permanent and significant nexus standards.


Who decides if a stream or pond is covered by WOTUS? 

Those determinations are made by the Army Corps of Engineers.

What is next in the WOTUS rule-making process? 

After the comment period closes, it is unclear how long the agencies will take to determine a final rule. And some groups have requested more time to review and comment on the proposal.

Of course, once a rule is in place, it may be challenged in the courts, just like previous definitions of WOTUS.

Sources: EPA, U.S. Army Corps of Engineers, National Association of Counties, American Farm Bureau Federation, court documents.

Reach Agweek reporter Jeff Beach at or call 701-451-5651.
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