• WOTUS was intended to define the scope of waters that are covered by the federal CWA.
• Intermittent features, unlike ephemeral features, may be considered waters of the United States.

The Clean Water Rule did not establish any regulatory requirements. Instead, it attempted to clarify the scope of “waters of the U.S.” consistent with the CWA, Supreme Court precedent, and science. This definition of WOTUS matters because many regulatory programs that fall under the scope of the federal Clean Water Act only apply when there is the possibility of impacting a water of the United States.

CWA programs that rely on the definition of waters of the U.S. include:

• The National Pollutant Discharge Elimination System (NPDES)
• Section 404 permit program for discharge of dredged materials (wetlands permitting)
• Oil spill prevention and response programs (Spill Prevention, Control, and Countermeasure (SPCC) and Facility Response Plans (FRPs))

The definition of “waters of the United States” (WOTUS) has had a rocky history, shaped over several decades by changing administrative priorities, executive actions, extensive litigation, and multiple Supreme Court decisions interpreting the scope of the Clean Water Act. After years of regulatory uncertainty following earlier court rulings, EPA and the ACOE finalized the Navigable Waters Protection Rule on January 23, 2020, adopting a narrower interpretation of federal jurisdiction. In August 2021, however, EPA and ACOE halted implementation of that rule following an Arizona District Court decision that vacated it, reverting temporarily to pre‑2015 regulations. Subsequent efforts to redefine WOTUS culminated in a revised rule issued in January 2023, which was then substantially constrained by the U.S. Supreme Court’s 2023 decision in Sackett v. EPA, rejecting the “significant nexus” test and significantly narrowing federal jurisdiction. As a result, EPA and ACOE amended the rule later in 2023 to conform with Sackett, and the current regulatory landscape reflects a more limited federal definition of WOTUS, with implementation varying by state while the agencies continue to pursue further rulemaking to establish a more uniform, durable standard.

Below is the current definition found in the code of federal regulations (40 CFR 120.2):

1. Waters which are:

(i) Currently used, or were used in the past, or may be susceptible to use in interstate or foreign commerce, including all waters which are subject to the ebb and flow of the tide;

(ii) The territorial seas; or

(iii) Interstate waters;

2. Impoundments of waters otherwise defined as waters of the United States under this definition, other than impoundments of waters identified under 40 CFR 120.2(a)(5);

(3) Tributaries of waters identified in 40 CFR 120.2(a)(1) and (a)(2) that are relatively permanent, standing or continuously flowing bodies of water;

(4) Wetlands adjacent to the following waters: (i) Waters identified in 40 CFR 120.2(a)(1); or (ii) Relatively permanent, standing or continuously flowing bodies of water identified in 40 CFR 120.2(a)(2) or (a)(3) and with a continuous surface connection to those waters;

(5) Intrastate lakes and ponds not identified in paragraphs 40 CFR 120.2(a)(1) through (a)(4) that are relatively permanent, standing or continuously flowing bodies of water with a continuous surface connection to the waters identified in 40 CFR 120.2(a)(2) or (a)(3)

Exclusions

The following are not “waters of the United States” even where they otherwise meet the terms of paragraphs 40 CFR 120.2 (a)(2) through (a)(5):

(1) Waste treatment systems, including treatment ponds or lagoons, designed to meet the requirements of the Clean Water Act;

(2) Prior converted cropland designated by the Secretary of Agriculture. The exclusion would cease upon a change of use, which means that the area is no longer available for the production of agricultural commodities. Notwithstanding the determination of an area's status as prior converted cropland by any other Federal agency, for the purposes of the Clean Water Act, the final authority regarding Clean Water Act jurisdiction remains with EPA;

(3) Ditches (including roadside ditches) excavated wholly in and draining only dry land and that do not carry a relatively permanent flow of water;

(4) Artificially irrigated areas that would revert to dry land if the irrigation ceased;

(5) Artificial lakes or ponds created by excavating or diking dry land to collect and retain water and which are used exclusively for such purposes as stock watering, irrigation, settling basins, or rice growing;

(6) Artificial reflecting or swimming pools or other small ornamental bodies of water created by excavating or diking dry land to retain water for primarily aesthetic reasons;

(7) Waterfilled depressions created in dry land incidental to construction activity and pits excavated in dry land for the purpose of obtaining fill, sand, or gravel unless and until the construction or excavation operation is abandoned and the resulting body of water meets the definition of waters of the United States; and

(8) Swales and erosional features (e.g., gullies, small washes) characterized by low volume, infrequent, or short duration flow.