Farm groups, led by the American Farm Bureau, are calling for the EPA and the U.S. Army Corps of Engineers to drop a rule defining the reach of federal oversight into the nation’s waterways.

The Waters of the U.S. rule, under the Clean Water Act (PL 95-217), attempts to clarify what constitutes waters under federal jurisdiction, adding tributaries and wetlands because they have a “significant nexus” to waters long considered the province of the law.

Farmers fear this could mean regulations now extend to ditches and ponds that are dry most of the year, and will add to the cost of doing business. The House has passed a bill (HR 5078) blocking the agencies from adopting the rule, and farm groups are keeping up the pressure on Congress.

But these upstream wetlands and waterways, clean water advocates say, are critical to drinking water supplies. Their position could get more traction as algal blooms continue to flourish downstream.

The EPA has said that streams and wetlands can remove as much as 40 percent of the nitrogen they carry before flowing downstream.

“Streams and wetlands are a vital part of our nation’s water infrastructure,” said Lynn Thorp, national campaigns director for Clean Water Action, “and their role in filtering pollutants including nitrogen before they make their way to large surface waters is critical in light of growing nutrient pollution.”