ALBUQUERQUE, N.M. — Townspeople affected by the millions of gallons of waste spilled from an abandoned gold mine and now flowing through their communities demanded clarity Tuesday about any long-term threats to their water supply.

Colorado and New Mexico made disaster declarations for stretches of the Animas and San Juan rivers and the Navajo Nation declared an emergency as the waste spread more than 100 miles downstream, where it will reach Lake Powell in Utah sometime this week.

EPA workers accidentally unleashed an estimated 3 million gallons of orange-yellow waste, including high concentrations of arsenic, lead and other potentially toxic heavy metals, while inspecting the long-abandoned Gold King mine near Silverton, Colorado, on Aug. 5.

EPA Administrator Gina McCarthy, who plans to tour the damage personally, said Tuesday in Washington, D.C., that she takes full responsibility for the spill. She said the agency is working around the clock to assess the environmental impact.

EPA officials said the bright plume has already dissipated and that the leading edge of the contamination cannot be seen in the downstream stretches of the San Juan River or Lake Powell.

So far, the Bureau of Reclamation has no plans to slow flows on the lower Colorado River, below Lake Powell, where the water is a vital resource for parts of California, Arizona, Nevada, New Mexico and Utah.

None of this has eased concerns among people in the arid Southwest who depend on this water for their survival.

The Navajos, whose sovereign nation covers parts of New Mexico, Utah and Arizona, shut down water intake systems and stopped diverting water from the San Juan River. Navajo Nation President Russell Begaye told The Associated Press that regional EPA officials told him the cleanup could take decades.

“This river, the San Juan, is our lifeline, not only in a spiritual sense but also it’s an economic base that sustains the people that live along the river,” Begaye said. “You’re taking away the livelihood and maybe taking it away from them for decades. … And we have yet to hear from the Obama administration.”

Heavy metals from Gold King and other defunct mines in Colorado have been leaching out and killing fish and other species for decades. The EPA has considered making part of the Animas River in Colorado a Superfund site for a quarter-century.

It would have provided more resources for a cleanup, but some in Colorado opposed Superfund status, fearing the stigma and the federal strings attached, so the EPA agreed to allow local officials to lead cleanup efforts instead.

Now the attorneys general of Utah, New Mexico and Colorado are coordinating a response to ensure “whatever remediation is necessary occurs as quickly as possible,” Utah Attorney General Sean Reyes said.

Utah Gov. Gary Herbert expressed disappointment with the EPA’s initial handling of the spill, but said the state has no plans for legal action. New Mexico Gov. Susana Martinez, however, said she would not take anything off the table and that the EPA should be held to the same standards as industry.

Colorado Gov. John Hickenlooper, himself a former geologist, hopes a “silver lining” to the disaster will be a more aggressive state and federal effort to deal with mining’s “legacy of pollution” across the West.

The EPA has said the current flows too fast for the contaminants to pose an immediate health threat, and that the heavy metals will likely be diluted over time.