The Environmental Protection Agency and the U.S. Army Corps of Engineers released a final rule on May 27 to clarify authority under the Clean Water Act (CWA) for navigable waterways and their tributaries. The so-called "Waters of the US" or Clean Water Rule more clearly defines waters that are protected by the CWA including small tributaries, adjacent wetlands that impact downstream waters (like prairie potholes, vernal pools, or coastal wetlands), and other isolated waters that had lost protection after two rulings by the Supreme Court in 2001 and 2006. Under the new rule, tributaries will be protected under the CWA if they have physical features of flowing water including a bed, a bank, and an ordinary high water mark. Adjacent waters are covered if they are in the 100-year floodplain and less than 1,500 feet from a covered waterway. The new rule does not provide new protections for ditches unless they are constructed out of a stream or function like streams and can carry pollution downstream; it also does not regulate groundwater, shallow subsurface flows, gullies, irrigation or water transfers, or tile drains.

"For the water in the rivers and lakes in our communities that flow to our drinking water to be clean, the streams and wetlands that feed them need to be clean too," said EPA Administrator Gina McCarthy. "Protecting our water sources is a critical component of adapting to climate change impacts like drought, sea level rise, stronger storms, and warmer temperatures ? which is why EPA and the Army have finalized the Clean Water Rule to protect these important waters, so we can strengthen our economy and provide certainty to American businesses."

The rule was first proposed in April 2014 and the EPA and Corps spent the past year evaluating comments and hosting scoping sessions; there have been mixed reviews of the changes ever since. While many in the conservation community expressed their support of the new rule, groups like the American Farm Bureau Federation have continued to criticize the rule. Members of Congress have been actively seeking to halt the implementation of the rule, passing legislation in the U.S. House of Representatives on May 12 and attaching a rider to the Interior and Environment appropriations bill.