At issue is which types of waterways — wetlands, rivers, lakes, etc.
The act regulates water pollutants and empowers the EPA and the Army Corps of Engineers to define which particular bodies of water are protected by law.
Protected bodies of water qualify for federal programs pertaining to oil spill prevention, water quality regulation and more.
The new definition announced this week instates similar protections to those that were in place before 2015, while also clarifying certain qualifications for protected waters.
"This comes at a time when we’re seeing unprecedented attacks on federal clean water protections by polluters and their allies," said Jon Devine, director of federal water policy for the Natural Resources Defense Council.