Water may be crucial for life in the West, but Westerners in 11 states have manipulated and trashed rivers to such an extent that half are now impaired – an impact measured as especially severe in Colorado.

“Disappearing Rivers,” an analysis to be unveiled Wednesday in Washington, D.C., identifies the culprits as developers who build along waterways; utility operators who divert water to generate power; cities and irrigators who disrupt natural flows using dams; and industries, such as mining, that are allowed to pollute streams.

In Colorado, water flows in 63 percent of streams and rivers are restricted by dams or development in floodplains, the analysis by California-based Conservation Science Partners determined. In neighboring Utah, virtually no unaltered natural waterways exist.

“We think of rivers as natural and pure. We found there was a high degree of degradation,” said CSP senior scientist Dave Theobald, a geographer and conservation biologist who serves on the faculty and conducts research at Colorado State University.

Revitalization of rivers must become a top priority, because healthy, clean waterways are economically and ecologically essential, but the cost will be huge, Theobald said. “It is tremendously inefficient to clean up something. It is more efficient to leave it pure in the first place.”

The Center for American Progress, an environment-oriented think tank in Washington, commissioned the study.

The researchers used satellite imagery, water-flow data and location information from a federal Bureau of Land Management database to conduct what they billed as an unprecedented comprehensive snapshot of the health of Western rivers. As population growth has accelerated across the arid and semi-arid West, rivers from headwaters in the high Rocky Mountains to oceans have faced rising pressure as people demand more – water for cities, electricity and crops, land near water for development and commerce, and recreational solace.

Among the 11 Western states, Colorado had the third-most miles of waterways measured as altered, following Utah and New Mexico, the analysis found. The researchers determined that 97 percent of major rivers, 61 percent of smaller waterways and 51 percent of headwaters streams have been altered.

Environmentalists long have decried the ruinous harnessing of wild rivers to meet human needs. An increasingly powerful constituency for taking better care of waterways has gained momentum with the rise of a national outdoor industry that generates commerce worth $887 billion a year dependent on a relatively pristine natural environment.

Conservationists argue that the economic benefits of using waterways for human recreation won’t be possible in the future if rivers in their natural form collapse.

Some companies are providing funds for efforts to revitalize degraded floodplains and streams. Outdoor gearmaker Patagonia, for example, helps finance projects aimed at removing thousands of crumbling “deadbeat dams” around the West — aimed at bringing back natural flows that can benefit ecosystems.

“It is undeniable that our rivers are under threat, now more than ever. We are waking up to this after may years of overuse, of placing barriers on our rivers – an ancient technology that is outdated and should be replaced,” Patagonia environment campaigns director Hans Cole said. “When dams are removed, fish come back right away and rivers can restore themselves.

“We need more funding for programs that enable dam removal – government funding. We need more funding on a national level to go into these efforts. We need more of our decision makers to pay attention to waterways.”

Colorado Department of Natural Resources officials did not respond to repeated requests for comment on the findings. That agency was created in part to prevent degradation of water.

Northern Water, which provides water drawn from the Western Slope to communities on Colorado’s booming Front Range, said the analysis of rivers and streams sounds well done, but it called talk of widespread dam removal crazy.

“Yeah, we’ve altered the landscape. We are living in it,” Northern Water spokesman Brian Werner said. “We’ve got to realize we are living here because of those alterations. We’re living here because of those dams.”