The Environmental Protection Agency and the Department of the Army opened a 30-day public comment window on a supplemental notice of proposed rulemaking that would tie federal Clean Water Act jurisdiction to a single physical test most landowners could apply by looking at a channel: does water stand or flow in it every day of the year?

Under the supplemental option, a stream is federally covered only if it is perennial. The agencies propose defining perennial as having standing or continuously flowing water every day of the year under ordinary conditions, with two carve-outs. A channel does not lose coverage if it dries because of an anomalous event such as drought. It also does not lose coverage if it dries for a single period of up to 30 consecutive days in a year because of a predictable, non-anomalous event such as a low tide or a regular seasonal dry spell.

The 30-day allowance is stricter than it first sounds. The agencies state the interruption may occur only once per year. By their own worked example, two separate 10-day dry periods in the same year would disqualify a channel even though the total is far under 30 days. A stream that reliably goes dry from June through August, roughly 90 days, would not qualify at all.

Perennial Flow with Two Narrow Exceptions

The document is candid about the scale of the change. The agencies write that they anticipate most intermittent streams would not satisfy the supplemental definition, while under current practice many intermittent streams are treated as relatively permanent. In their programmatic assessment, the agencies say the effect would be significant for Clean Water Act jurisdiction of streams and wetlands relative to the current baseline, and that the arid West in particular would see a significant reduction in federally jurisdictional waters.

For scale, the agencies point to the National Hydrography Dataset, which maps about 1.3 million miles of perennial streams and about 3.5 million miles of intermittent streams in the contiguous United States, roughly 21 percent and 55 percent of mapped stream miles. The agencies attach a caveat that should not be skipped: that dataset does not depict the scope of waters regulated under the Clean Water Act, does not cleanly separate intermittent from ephemeral channels in every region, and cannot be used to calculate how many miles would actually change status. The agencies say they cannot reliably quantify the current baseline, and therefore cannot put a number on the change.

The stated rationale is administrability, meaning clarity a landowner can act on without a consultant. The agencies argue the test would let members of the public determine coverage by observation, without further analysis or professional consultation, echoing the Supreme Court's concern in Sackett v. EPA about property owners needing an expensive expert consultant to understand their obligations.

Drought Category Would Decide Jurisdiction in the Southwest

The drought exception is where the proposal becomes concrete for Western landowners, and where it gets unusual. The agencies are considering counting only extreme (D3) and exceptional (D4) conditions on the U.S. Drought Monitor as the anomalous drought that preserves a channel's status. Moderate (D1) and severe (D2) drought would not qualify.

The agencies also propose a five-year ceiling. If qualifying drought runs continuously for more than five years, the agencies would treat the dry condition as the new normal; the interruption would stop being anomalous, and the channel would no longer be federally jurisdictional. The five-year figure is drawn from the expiration period for an approved Army Corps jurisdictional determination.

That mechanism lands on a region already deep in drought. A NOAA drought status update for the Intermountain West published in late August reported that nearly 95 percent of Arizona, Colorado, New Mexico, Utah, and Wyoming was in some level of drought on the Drought Monitor map valid August 18, with roughly 30 percent of the region in the D3 or D4 categories. For watersheds around Phoenix, Albuquerque, Las Vegas, and Salt Lake City, whether a wash counts as a federally protected water could turn on which category the map shows and for how many consecutive years.

Wetlands Face a Separate and Broader Change

A second supplemental option would redefine continuous surface connection to require perennial surface water in a wetland that stays continuously connected to surface water in the jurisdictional water, subject to the same drought and 30-day exceptions. Only the portion of the wetland that is indistinguishably part of the jurisdictional water would itself be covered.

The agencies state plainly that they anticipate the majority of wetlands currently jurisdictional as adjacent wetlands would not meet that test, because most wetlands do not contain perennial surface water. That is a larger practical shift than the stream definition, and it is the change most likely to affect Section 404 dredge and fill permitting, which the agencies expect would see the most programmatic change, with projected reductions in the number of permits and in required mitigation.

Cost effects run in both directions, and the agencies quantify neither. They describe cost savings from avoided Section 404 permits and the associated avoidance, minimization, and mitigation work, set against forgone benefits from that same compensatory mitigation. They conclude that in magnitude both the cost savings and the forgone benefits are larger under this supplemental package than under the original proposal. States and Tribes remain free to regulate waters that fall outside federal coverage, though the agencies concede some may need to spend considerable resources to build such programs and that other states have laws restricting them from being more stringent than federal rules.

Filing a Comment Before the Deadline

Comments must be received on or before October 9, 2026. Submissions go to docket EPA-HQ-OW-2025-0322 through the Federal eRulemaking Portal, and EPA publishes guidance on making effective comments. The agencies ask commenters not to resubmit points already filed during the earlier comment period, which drew roughly 220,000 comments between the November 2025 publication of the original proposed rule and the January 2026 close.

Several things remain unresolved. This is a proposal, not a final rule, and the agencies say they are still weighing the options in the original proposal alongside these supplements. No estimate of affected stream miles or wetland acres exists. The agencies are also soliciting comment on whether a threshold other than 30 days, or a drought window other than five years, would be more appropriate. Any final rule would be subject to litigation, as nearly every version of this definition has been over the past eleven years, a stretch the agencies themselves describe as containing five rule revisions, a major Supreme Court decision, and a steady run of lower court rulings.

Landowners, ranchers, farmers, and small operators in the West have the most at stake in the near term, because the option changes what can be done in a dry wash without a federal permit and what a state may still require regardless. The comment docket is the only formal channel to influence the outcome before a final rule is written.

What Readers Want to Know

What exactly did the agencies propose?

A supplemental notice seeking comment on defining relatively permanent waters as perennial only, defining perennial as flowing or standing every day of the year under ordinary conditions, and redefining continuous surface connection for wetlands to require perennial surface water.

Is this a final rule?

No. It is a supplemental notice of proposed rulemaking. It supplements an earlier proposal published in November 2025 and takes comment on additional regulatory options.

How long is the comment period?

Thirty days from publication in the Federal Register. Comments must be received on or before October 9, 2026, and go to docket EPA-HQ-OW-2025-0322.

Which regions would change the most?

The agencies expect the arid West to see the largest reduction in federally jurisdictional waters, because intermittent channels carry much of the hydrology there.

Would drought protect a stream from losing coverage?

Only under specific conditions. The agencies are considering counting only extreme and exceptional drought categories, and only for up to five continuous years, after which the dry condition would be treated as normal.

Do states still have authority over these waters?

Yes. States and Tribes may regulate waters that fall outside federal coverage under their own laws. Whether they do so varies, and some states have laws restricting them from being stricter than federal rules.

How many stream miles would lose protection?

No one has published that number, including the agencies. They state that data limitations prevent a reliable quantitative estimate.