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The Clean Water Act (CWA) explicitly calls for the federal government to protect “navigable waters.” EPA regulations implementing the Clean Water Act use the term “navigable waters,” which is defined at section 502(7) of the Clean Water Act as “the waters of the United States, including the territorial seas,” or the term “waters of the United States.” The definition of “waters of the United States” has been subject to debate and litigation over the years. The latest regulatory definition (as revised in 2023) outlines the categories of waters that are currently considered “waters of the United States.”
Waters of the United States means:
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;
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);
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;
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;
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):
Waste treatment systems, including treatment ponds or lagoons, designed to meet the requirements of the Clean Water Act;
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;
Ditches (including roadside ditches) excavated wholly in and draining only dry land and that do not carry a relatively permanent flow of water;
Artificially irrigated areas that would revert to dry land if the irrigation ceased;
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;
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;
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
Swales and erosional features (e.g., gullies, small washes) characterized by low volume, infrequent, or short duration flow.
Scope
The definition of “navigable waters” and “waters of the United States” helps regulators, regulated entities, and the public understand where the CWA and its implementing regulations apply and where they do not. This EzExplanation reflects the current definitions found in the code of federal regulations (40 CFR 120.2)
Regulatory citations
33 CFR 328 — Definition of waters of the United States
Wetlands means those areas that are inundated or saturated by surface or ground water at a frequency and duration sufficient to support, and that under normal circumstances do support, a prevalence of vegetation typically adapted for life in saturated soil conditions. Wetlands generally include swamps, marshes, bogs, and similar areas.
Adjacent means having a continuous surface connection.
High tide line means the line of intersection of the land with the water's surface at the maximum height reached by a rising tide. The high tide line may be determined, in the absence of actual data, by a line of oil or scum along shore objects, a more or less continuous deposit of fine shell or debris on the foreshore or berm, other physical markings or characteristics, vegetation lines, tidal gages, or other suitable means that delineate the general height reached by a rising tide. The line encompasses spring high tides and other high tides that occur with periodic frequency but does not include storm surges in which there is a departure from the normal or predicted reach of the tide due to the piling up of water against a coast by strong winds such as those accompanying a hurricane or other intense storm.
Ordinary high water mark means that line on the shore established by the fluctuations of water and indicated by physical characteristics such as clear, natural line impressed on the bank, shelving, changes in the character of soil, destruction of terrestrial vegetation, the presence of litter and debris, or other appropriate means that consider the characteristics of the surrounding areas.
Tidal waters means those waters that rise and fall in a predictable and measurable rhythm or cycle due to the gravitational pulls of the moon and sun. Tidal waters end where the rise and fall of the water surface can no longer be practically measured in a predictable rhythm due to masking by hydrologic, wind, or other effects.
Summary of requirements
Use the current definitions of “navigable waters” and “waters of the United States” in 40 CFR 120.2 to determine which waters are regulated and protected under the Clean Water Act (CWA) and its implementing regulations.
Meet the CWA and its implementing regulations, as applicable.
Editor’s note: The latest CFRs define “waters of the United States” per the January 18, 2023, final rule, as amended by the September 8, 2023, conforming final rule. EPA and the Army Corp of Engineers refer to these regulations as the “Amended 2023 Rule.” However, due to preliminary injunctions of the Amended 2023 Rule in several states, the agencies are implementing two regulatory regimes across the country. Specifically, the agencies are implementing the Amended 2023 Rule in 24 States, the District of Columbia, and the U.S. Territories. In the other 26 States, the agencies are interpreting “waters of the United States” consistent with the “Pre-2015 Regulatory Regime and the Supreme Court’s Sackett v. EPA Decision.” The latest information on the status of this litigation can be found on the EPA’s Definition of “Waters of the United States": Rule Status and Litigation Update webpage at https://www.epa.gov/wotus/definition-waters-united-states-rule-status-and-litigation-update. On November 20, 2025, EPA published the Updated Definition of "Waters of the United States" proposed rule in the Federal Register. If finalized, the proposed revisions would limit those waters found to be jurisdictional compared to the Amended 2023 Rule.
