Wetlands on your land, in plain language

What counts as a wetland

The regulatory definition under the Clean Water Act, used by the EPA and the Army Corps since the 1970s, is that wetlands are "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" (EPA, CWA Section 404).

To identify a wetland on the ground, agencies use the three-factor test from the 1987 Corps of Engineers Wetlands Delineation Manual. An area is a wetland when all three are present (EPA):

• Hydric soils: soils that formed under saturation and carry the low-oxygen traits that leaves. See our guide to hydric soils.
• Hydrophytic vegetation: plants adapted to life in saturated ground, such as marsh grasses.
• Wetland hydrology: water present by ponding, flooding, or saturation at a wetland frequency and duration.

All three must be present. A patch of cattails on otherwise well-drained ground, or a wet spring in a normal field, does not by itself make a wetland.

What a wetland map shows, and its limits

The most common wetland map is the USFWS National Wetlands Inventory (NWI). It is a genuinely useful screening layer: it shows where mapped wetlands are likely, using a biological definition of wetlands. But the U.S. Fish and Wildlife Service is explicit about its limits. NWI data are "developed using a biological definition of wetlands and may not be consistent with wetland boundaries established according to the federal regulatory definition," and the data "should not be interpreted as representing the presence, absence, or extent of wetlands that may be covered under one or more federal, state, Tribal, or local laws" (USFWS, wetlands data limitations).

In plain terms: a wetland map tells you where to look, not what is legally regulated. It can miss small or altered wetlands and can map areas that a field delineation would not confirm.

A mapped wetland is not a jurisdictional determination

This is the single most important point on the page. Only the U.S. Army Corps of Engineers can issue a jurisdictional determination, the official finding of whether a specific wetland is regulated under Clean Water Act Section 404 (EPA). A map layer, including the one AgriTerra shows, is a screening tool. The regulatory answer comes from a field delineation and the Corps, not from any desktop map.

The post-Sackett picture

The scope of which wetlands are federally regulated narrowed after the Supreme Court's 2023 decision in Sackett v. EPA. The Court held that the Clean Water Act reaches wetlands with a "continuous surface connection" to a traditional navigable water, replacing the older "significant nexus" test. The EPA and the Army have since issued implementation guidance and a proposed rule to conform the regulatory definition of "waters of the United States" to that ruling (EPA, current implementation of WOTUS). The practical upshot, stated neutrally: federal jurisdiction is narrower than it was, the definition is still being finalized through rulemaking, and state and local wetland rules can apply regardless of federal scope. Because this area is actively changing, treat any general statement, including this one, as a starting point and confirm current status for your situation.

What wetlands mean for farming and USDA programs

Beyond the Clean Water Act, wetlands matter for farm programs. Under the wetland conservation provisions, commonly called Swampbuster, producers agree not to plant an agricultural commodity on a converted wetland or to convert a wetland to make crop production possible, as a condition of eligibility for most USDA programs (USDA NRCS). USDA NRCS makes the wetland determinations for that purpose. So converting wet ground can put farm program benefits at risk even where no Clean Water Act permit is triggered. The safe sequence before any drainage, fill, or clearing is a USDA NRCS wetland determination and, where a jurisdictional wetland may be involved, a check with the Army Corps.

How to screen your parcel

AgriTerra shows the USFWS National Wetlands Inventory layer for a parcel alongside soil, drainage, flood, and every revenue option, free, so you can see quickly whether wetlands are a question worth pursuing. Read it as a screen, exactly as USFWS intends, and use it to decide whether you need a professional delineation and a determination, not as a substitute for one. For the soil side of the wetland picture, see hydric soils; for how every figure on this site is sourced, see how we get our numbers.