The Environmental Protection Agency and the Army Corps of Engineers wrote the new guidelines after the Supreme Court split a year ago in a case about which waters fall under the Clean Water Act.

Because of the split decision, lower courts must decide on a case-by-case basis if the law applies to smaller water areas.

Four justices said the law was restricted to protecting navigable waters such as lakes and rivers, and bodies connected to them, while four argued the law had a broader reach.

The new guidelines were intended to help workers in the field determine if a waterway fell under the act, using the argument of Justice Anthony Kennedy, who did not join either side in the decision.

Benjamin Grumbles, EPA's assistant administrator for water, told reporters during a conference the new guidelines would provide greater consistency and predictability for the public.

Now his agency will regulate waters large enough to be used by boats that transport commerce, along with wetlands adjacent to them. It will decide on a case-by-case basis to regulate other tributaries that may affect main waterways.

"In effect, the EPA and the Corps are taking their field staff and the public out to the woods, blindfolding them, spinning them in circles, telling them to 'go west,' and calling that guidance," complained Jon Devine, a senior attorney at the Natural Resources Defense Council.

The EPA's new policy does not offer clear instructions to scientists in the field on how to protect surface waters, Devine said, and would eliminate protections for many streams. He also said the case-by-case decisions would inspire an onslaught of lawsuits and public confusion.

John Woodley, Assistant Secretary of the Army, said there would be no way to measure changes from the guidance.

But, he said, the waterways in the Supreme Court case would have been considered wetlands according to EPA's new guidance.

Angered by the Supreme Court's split, Democratic lawmakers last month introduced the "Clean Water Restoration Act" that would drop the word "navigable" from the original law.