Three Chesapeake Bay tributaries, variously threatened by dam construction, animals wastes and development, were listed among the most "endangered" waterways named this year by a national river conservation group.

The group, American Rivers, named the Pocomoke River - site of last year's fish killing pfiesteria outbreak - as the nation's third most endangered river.

The Potomac, which the group said was threatened by factory poultry farms, cattle feedlots in upstream rural areas and development in the Washington area, was ranked 12th.

And the Mattaponi River in Virginia, which could have as much as 75 million gallons a day pumped from it to supply a proposed reservoir, was ranked 17th.

Last year, only a single river within the Bay watershed - the Potomac - was on the list.

Nationwide, a 51-mile stretch of the Columbia River in Washington state known as the Hanford Reach was named the most endangered river in America.

It is the last free-flowing, undeveloped stretch of the Columbia in the United States and it continues to produce the region's strongest chinook salmon runs while fish populations crash in other dammed stretches of the Snake and Columbia river system.

The Hanford Reach had been preserved for years because of the presence of the Hanford Nuclear Reservation, but is now facing threats from proposed land development around the river.

The threats facing the three Bay tributaries, according to the group's annual report, are similar to those which face other rivers nationwide: animal wastes that contaminate water; urban sprawl that chews up land, dams and population growth.

"We continue to abuse our rivers - by damming, draining, straightening and polluting them - all the while weakening their ability to sustain fish and wildlife," said Rebecca Wodder, president of American Rivers. "Freshwater species are disappearing at alarming rates - three to seven times faster than any other species. These creatures are the miner's canary - warning us that our rivers are in trouble. Protecting our freshwater resources must be a national priority."

In its 13th annual ranking of imperiled rivers, the group said the fastest growing threat to waterways was the waste produced by large-scale animal agriculture operations, which result in huge accumulations of manure and nutrients in localized areas which can contaminate waterways.

"Factory hog and chicken farms are a growing national blight on our nation's rivers," Wodder said. "In the last two decades, we have made significant progress in cleaning up waterways and putting a stop to major industrial sources of pollution. Now we are faced with a threat so pervasive it could send us back to the days when rivers, in many cases, were nothing more than cesspools."

The group called for stronger federal action to control animal wastes. The EPA recently proposed a new program that would phase in regulations for thousands of large livestock operations by 2005, but American Rivers called that timetable "unacceptably slow."

Animal wastes figured into the groups' selection of two Bay tributaries to the list.

The Pocomoke, a Maryland state scenic river which also includes parts of Virginia and Delaware on the Delmarva peninsula, was selected because of last year's highly publicized outbreak of the toxic microbe, pfiesteria.

The tiny organism killed about 20,000 fish and was blamed for sickening dozens of people.

Nutrients are thought to help create conditions that cause pfiesteria - which is normally a harmless organism - to turn toxic. The majority of nutrients in the Pocomoke originate from agriculture, and poultry farming, in particular, has been expanding rapidly in the region. The problem spurred intense legislative debate in Maryland over legislation aimed at regulating animal waste.

In the Potomac, the group blamed cattle feedlots and the 95 million chickens produced in factory poultry farms for excessive nutrients and bacteria levels observed in the river's South Branch in West Virginia.

In addition, it said that large-scale developments in the basin pose a threat to the Potomac. It singled out the proposed 2,250-acre development at Chapman's Landing along more than two miles of riverfront in Maryland's Prince George's County as a serious threat. It also said development threatened Mattawoman Creek, a Potomac tributary. Maryland has recently proposed purchasing the site from the developer.

The Mattaponi, which meets the Pamunkey River to form the York River, made the list because of a proposal by the Newport News Waterworks to withdraw up to 75 million gallons per day to maintain a planned reservoir.

The Mattaponi has been called "the heart of the most pristine freshwater complex on the Atlantic Coast" by The Nature Conservancy. But the river group said the water diversion could increase salinity levels, water temperatures and reduce oxygen levels in the river. It also said the project would flood more than 437 acres of wetlands and destroy nearly 1,400 acres of upland habitat.

Proponents say the water is needed for the rapidly growing Newport News-Hampton-Williamsburg areas, and contend that providing water to an area with existing infrastructure could help curb sprawl development in the future.

The State Water Control Board approved a permit for the project last December, with several conditions. The project still requires a permit from the Army Corps of Engineers, which could make a decision this summer.

Billy Mills, executive director of the Mattaponi & Pamunkey Rivers Association, hailed the listing. "There should be no question after today, specifically in reference to the criteria American Rivers employs in its annual list, that the Mattaponi River is under a grave threat, and that the threat is real and immediate," he said.

But not everyone agreed with the group's list.

U.S. Rep. Wayne Gilchrest, who represents the district that includes the Pocomoke, said he doubted that waterway was the nation's third most endangered river. "I will say the Pocomoke is not as bad as hundreds of rivers that are dead or dying," Gilchrest said.

A senior West Virginia agricultural official labeled the group "headline hunters."

According to American Rivers, selections were based on the seriousness and imminence of the threat; the likelihood that major action during the coming year could intensify or lessen the threat; the regional and national significance of the river; geographical diversity; and the range of threats representative of problems facing rivers nationwide.

20 Most Endangered Rivers in the United States

The conservation group American Rivers released its annual list of the 20 most endangered rivers in North America. Here is the list of rivers, the states and other localities in which they are found and the threats they face:

  1. Hanford Reach of the Columbia River in Washington; agricultural development, nuclear waste contamination.
  2. Missouri River in Montana, North Dakota, South Dakota, Nebraska, Iowa, Kansas and Missouri; dams, channelization.
  3. Pocomoke River in Maryland; factory poultry farms.
  4. Kern River in California; small hydropower dams.
  5. Blackfoot River in Montana; gold mine.
  6. Colorado River Delta in Baja California, Mexico; overuse of water.
  7. Chattahoochee River in Georgia, Alabama and Florida; development, polluted runoff, sewage overflows.
  8. Lower Snake River in Washington; dams.
  9. Apple River in Wisconsin and Illinois; factory hog farms.
  10. Pinto Creek in Arizona; copper mine.
  11. Wolf River in Wisconsin; zinc, copper sulfide mine.
  12. Potomac River in West Virginia, Virginia, Maryland, District of Columbia and Pennsylvania; factory poultry farms, cattle feedlots and development
  13. Rogue-Illinois River System (including Elk Creek and Rough & Ready Creek) in Oregon; dams, nickel laterite mine.
  14. Taku River in Alaska and British Columbia; copper, gold mine.
  15. Crooked Creek in Arkansas; in-stream gravel mining.
  16. Passaic River in New Jersey; contaminated sediments.
  17. Mattaponi River in Virginia; dam and reservoir.
  18. Walla Walla River in Oregon and Washington; agricultural pollution, low flows, channelization.
  19. Uinta River in Utah; dam.
  20. Kansas River in Kansas; agricultural and municipal pollution.