The change in the technical designation affects the water quality standards to be set for the rivers. Essentially, the government would be lowering the bar for what's considered a healthy level of oxygen in the water.

"To me, this is just like, 'Oh, this doesn't fit the old model. Let's give up and redesignate the criteria,' " said Diana Muller, the riverkeeper for the South River Federation.

Dissolved oxygen is vital for a healthy river. When there's not enough oxygen in the water, fish, crabs and shellfish can't survive.

Muller spotted the proposal on the Maryland Department of the Environment's website, and she has been rallying local environmental groups to fight the change. She said the South River Federation never got any notice of the proposal.

"They didn't give a lot of people a lot of notice," Muller said.

The U.S. Environmental Protection Agency is seeking the change based on a more in-depth review of water quality data from the rivers. The change must be adopted by the Maryland Department of the Environment.

Rich Batiuk, associate director of science for the EPA's Chesapeake Bay Program, said scientists were trying to figure out why pollution reductions weren't translating into more oxygen in the rivers, as would be expected.

They found that a natural phenomenon was making it difficult for the oxygen level to improve.

Sometimes cool, oxygen-rich freshwater from streams gets stuck on top of the river while saltwater from the bay is trapped on the bottom. This tends to happen in summer.

When the two types of water don't mix well, oxygen isn't spread out in the water. The technical term for this is a "pycnocline."

Batiuk said that when there's a pycnocline, it's not possible to get high levels of oxygen into the deep part of the rivers. The same thing also happens in the main stem of the Chesapeake Bay.

So the EPA proposed changing the technical classification for the rivers to reflect this phenomenon.

As a result, during the summer months, the standard for oxygen in the deep parts of the rivers will be lower - it will be 3 milligrams of oxygen per liter of water instead of 5 milligrams per liter.

Striped bass, white perch and yellow perch need 5 milligrams of oxygen per liter to survive, blue crabs need 3 milligrams per liter and worms need 1 milligram per liter.

Batiuk stressed that the lower standard will only be in place in the summertime, and even then, only if the lack of mixing takes place, as determined by monitoring.

"We're not downgrading the river. We're not saying these critters in here can stand more pollution," Batiuk said.

Batiuk said there still will be pollution reductions required for the rivers under the new federal "pollution diet" being unveiled today.

"We're not all of a sudden saying that we can accept a lower water quality condition for these three rivers," Batiuk said.

But that's exactly how the river advocates see it.

Fred Kelly, the Severn riverkeeper, was incensed.

"This is EPA's continuing paper-pushing, doublespeak, name-changing to obfuscate their failure to stop pollution from coming into the Severn River," he said. "It's classic bureaucratic stupidity."

Kelly accused the government of lowering the bar to make it look like the Chesapeake Bay cleanup effort is going better than it really is.

Muller, from the South River, said that under the new, relaxed standards, 58 percent of her weekly water quality measurements would be acceptable. Under the current, stricter standards, just 22 percent of the readings are in compliance.

Advocates for the South, Severn and Magothy have been preparing their official opposition to the redesignation. A public hearing is planned in Baltimore this afternoon, and a comment period extends through Oct. 12.

The Maryland Department of the Environment will have to respond to comments and get a final OK from the EPA before making the designation permanent.

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