In Arizona, for instance, home of the threatened Apache trout, almost all streams are dry except during and after rainstorms. As a result, 83 percent of Arizona streams will lose protection under the E.P.A.’s new policy, according to state officials, along with 99 percent of lakes. Because the state does not have its own regulations, 98 percent of the permits that limit pollution discharges into waterways will simply no longer be in force.

The situation is similar in New Mexico, where the new rule will effectively invalidate permits controlling the levels of mercury and PCBs running off the heavily contaminated grounds of Los Alamos National Laboratory and into the Rio Grande, Santa Fe’s main drinking water supply.

In West Virginia and Virginia, there will no longer be federal protections for some 82 small streams that are to be excavated if the 600-mile Atlantic Coast Pipeline is built, based on surveys by Dominion, the pipeline’s developer.

In the Great Plains, the E.P.A. will no longer conserve freshwater marshes known as prairie potholes that fill with water in the spring and provide critical, timely habitat for more than half of North America’s migratory waterfowl. In the flood-prone Houston area, federal permits will not be required to develop coastal and prairie wetlands that absorb excess rainwater and provide habitat for migrating songbirds and waterfowl.

The E.P.A.’s new policy comes with a price tag. It’s not just that it threatens an $887 billion American outdoor recreation economy powered in part by anglers, duck hunters and wildlife watchers.

When the E.P.A. stops protecting these streams and wetlands, states will have to foot the bill for regulatory oversight; many states may decide not to step in at all. When developers fill in wetlands, local communities will be on the hook for cleaning up more frequent flood damage. When headwaters are polluted, cities downstream will pay to treat their drinking water.

You need only consider the name to recognize what’s happening here. What was the Waters of the United States Rule is now the Navigable Waters Protection Rule. This signals a narrow concern only for commerce but not, illogically, for the network of tributaries and wetlands that keep navigable waters healthy.