Waters of the United States

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The U.S. Environmental Protection Agency announced the final rule repealing the 2015 definition of “waters of the United States” (WOTUS) under the Clean Water Act on Sept. 12. EPA said its next step after the repeal is to implement the proposed new definition, which the agency released in December 2018.


This  rule would redefine primary Waters of the United States (WOTUS) with the intention to increase predictability and stability in water pollution enforcement. The proposed rule would narrow the definition of primary WOTUS to include only waters within the standard meaning of the term (e.g. oceans, streams, rivers, lakes, ponds, and wetlands). The proposed rule clarifies that tributaries are only protected by the Clean Water Act if they flow directly (or indirectly through other tributaries) and perennially or intermittently downstream to primary WOTUS. The proposed rule also narrows protected adjacent wetlands to wetlands with a direct hydrological surface connection to other WOTUS. The proposed rule excludes groundwater, wastewater treatment systems, most artificially created waters and ditches, and waters that flow only in response to precipitation, among other provisions.

Since the Clean Water Act was originally enacted, there has been ambiguity as to what waters are in the federal government’s jurisdiction. A 2015 EPA rule change under the Clean Water Act significantly expanded the definition of WOTUS to include tributaries that flow directly or indirectly to a traditional navigable water; waters adjacent to primary waters or tributaries, including a wide range of waters within or near the ordinary high-water mark or floodplain or some jurisdictional waters, even if they are not directly connected to primary waters. The 2015 WOTUS definition also included waters that have significant chemical, physical, or biological effects on a primary water. The 2015 rule excluded certain ditches, some artificial bodies of water and groundwater.

After the publication of the 2015 rule, 31 states, including Wisconsin, challenged the EPA’s authority to enforce the broad rule. The U.S. Supreme Court ruled in early 2018 that the 2015 rule is subject to direct review in federal district courts. Since then, district courts have issued preliminary injunctions applying to 28 states overall, including Wisconsin.

In February 2017, President Donald Trump issued an Executive Order asking EPA to revise the 2015 rule so that the Clean Water Act promotes economic growth and minimizes regulatory uncertainty, while still reducing water pollution.



September 12, 2019 Final Rule Repealing 2015 Definition of “Waters of the United States”
Final Rule
February 27 & 28, 2019 Public Hearing
December 11, 2019 Proposed Rule on Revised Definition of “Waters of the United States”
Proposed Rule
February 28, 2017 Executive Order on Reviewing the WOTUS Rule
Executive Order
2015 EPA Rulemaking Expanding Definition of WOTUS
2015 Rule


Administration Documents

Docket # EPA-HQ-OW-2018-0149

EPA WOTUS Rulemaking Home

Proposed Rule


Hamilton Analysis

EPA to Revise Waters of the United States Rule


News Clips

High court to consider case about reach of clean-water law: Daily Reporter, February 19, 2019.

EPA announces new definition of waters protected under Clean Water Act: CNN, December 11, 2018.