Climate part of water worries

Monday, Dec. 18, 2000 | 12:34 p.m.

A warmer climate predicted for the 21st century could affect the Colorado River, making it harder to manage water delivery to states such as Nevada, California and Arizona, a report says.

The U.S. Geological Survey and the Pacific Institute of Oakland, Calif., released a report Friday that says climate change needs to be considered in water planning.

As the southern part of the United States heats up, species may move north, escaping the hot zone, according to the report, the result of two years of study.

A warmer climate also means less water available in the Colorado River and other resources, as smaller streams dry up and evaporation takes a toll, the report notes.

The warmer temperatures could bring more severe storms that could leave pools of water, where diseases such as cholera and cryptosporidium, a single-celled organism that killed 43 Las Vegas Valley residents in 1994, could thrive, the report says. Such bacteria could pose a threat to water supplies.

However, it notes, "No clear evidence is available yet to conclude how climate change will ultimately affect these factors or to suggest any climate-related change in the incidences of these kinds of diseases in the United States."

More research and careful monitoring of water was recommended.

Lead author Peter Gleick said in a telephone interview that there is no cause for alarm, although the Colorado River could be hard hit because it is used so extensively by seven Western states.

"The Colorado River is intensively used, and therefore very sensitive to climate changes," he said.

Since California has senior water rights on the river, smaller states such as Nevada and Arizona could end up with less water, he said. Lower flows on the river, which ends in Mexico, would also impact the border.

"What happens on the Colorado affects Las Vegas as well," Gleick said.

Rather than create panic, Gleick said the report urges water managers to consider hotter, drier weather and its effects on surface and ground waters.

"Water managers need to consider climate change," he said.

The U.S. Bureau of Reclamation manages the river year-to-year and on a long-term basis, but its long-range planning does not factor in climate changes, Jayne Harkins, Lower Colorado River operations manager, said.

Harkins said her department was aware of the study but had not had a chance to review it yet.

"We have done some analysis in the past," Harkins said, but the analyses only looked at past trends without trying to forecast future water levels.

That analyses show the river has experienced "significant" droughts in the past 50 years, she said. A 12-year period from 1953 to 1965 reduced flows and an eight-year dry spell lasted from 1988 to 1996, Harkins said.

"The river's level can vary a great deal," she said.

Built into the Colorado River system of dams, reservoirs and lakes is a four-year reserve in case of extended drought.

"We've slowly been dropping this year," Harkins said. "We are showing that Lake Mead will drop in time as the upper basin states take their full share."