Washington - Water supplies for 33 million people could be endangered if millions of acres of beetle-ravaged forests in the Rocky Mountains catch fire, a U.S. Forest Service official said Tuesday.

Rick Cables, the chief forester for the Rocky Mountain region, told a House panel that the headwaters of the Colorado River, an important water source for residents of 13 states, are in the middle of 2.5 million acres of dead or dying forests in Colorado and southern Wyoming. Severe fires, fueled by these trees, could damage or destroy reservoirs, pipes and other infrastructure that supply water to millions of people in the Rocky Mountain region.

Moreover, wildfires can "literally bake the soil," leaving behind a water-repellent surface that sheds rain and leads to severe erosion and debris, he said. The loss of so many trees also will reduce shade in the region, which in turn could reduce water supplies in the hot, dry summer months and accelerate snowmelt in the spring, he said.

A Forest Service analysis indicates people in San Diego, Los Angeles, Phoenix, and Tucson, Ariz. who get their tap water from the Colorado River get one quart of every gallon from national forests in the Rocky Mountain region.

"The arid West absolutely depends on national forests as the source for their water," Cables said. "The reach of this watershed is unparalleled in the West."

While bark beetle outbreaks are naturally recurring events in the West, the current outbreak - which has killed nearly 8 million acres of trees - is the biggest in recorded history, Barbara Bentz, a research entomologist with the Forest Service, told the committee.

Besides Colorado and Wyoming, other states especially hard hit include Idaho, Montana, Oregon and eastern Washington. In Canada, more than 22 million acres have been affected and scientists suspect that the death of so many trees is altering local weather patterns and air quality.

Officials from affected states who testified said they need help to avoid a potential catastrophe. Local officials said they want more money to clear trees from buildings, transmissions lines and other facilities. They also are seeking government help for companies trying to turn dead trees into wood products, especially pellets that can be burned to produce energy. If a market can be created for the dead trees, it can help offset their costly removal, they said.

"We need resources on the ground," said Sloan Shoemaker, executive director of the Wilderness Workshop, a Colorado conservation group.

Protecting lives is the top concern. At least a dozen Colorado towns are surrounded by dead forests and another dozen towns border the forests. The region is also home to ski resorts like Vail, Breckenridge and Winter Park. Trees falling across roads, blocking potential evacuation routes in event of a fire are also a concern.

Another concern is the 13,000 miles of electricity transmission lines that run through the forests. There is a possibility that multiple fires at the same time could cause widespread regional power outages, Ron Turley, special projects manager for the Western Area Power Administration, told the committee.

"This could have significant regional and potentially national consequences," Turley said.

Of the $1.5 billion the Forest Service received in economic stimulus funds, about $26 million has so far been directed to the Rocky Mountain region to deal with beetle-related problems, chief forester Cables said.

Cables said that a year ago he also requested $213 million in emergency aid over three years to deal with safety threats. He said about $20 million has been received so far.

"We have a lot of work being done and a lot of work on the shelf," Cables said. "We're trying to be as effective with the money as we can."