The winter rains that ended Tucson's short-term drought haven't helped the river that provides most of the city's drinking water.
The Colorado River that feeds the Central Arizona Project depends on heavy spring flows into Lake Powell at the Arizona-Utah border. But the spring runoff into the lake is now expected to be even less than predicted two months ago.
WHAT'S HAPPENING TO RUNOFF
The federal Colorado River Basin Forecast Center predicted Wednesday that flows into Lake Powell for April through June will be about 5.4 million acre-feet, or about 68 percent of normal. The forecast was 78 percent of normal on Jan. 1 and dropped to 71 percent in mid-February.
Spring runoff into Powell has been below normal all but two of the past 11 years. An acre-foot is 326,851 gallons of water, or enough to supply water to three typical families for a year.
THE EFFECT ON CAP
If current runoff trends continue, the CAP could run short of water by 2012 for the first time in its 25-year history, said Tom McAnn, the CAP's assistant general manager for operations, planning and engineering.
Such a shortage would cut supplies to farmers, mining companies, some private water companies and other users in Central and Southern Arizona.
THE EFFECT ON TUCSON
There's none in the short term. Tucson is one of the project's highest-priority customers.
But continued dry weather could bring shortages to Tucson after 2025.
Tucson Water delivered about 120,000 acre-feet of CAP water in 2009 to its customers, or about 80 percent of its drinking supply.
WHY RUNOFF IS SO POOR
Snowpack is well below normal in the upper basin of the Colorado, which includes Colorado, Utah, Wyoming and northwest New Mexico.
Plus, areas such as the Green River Basin in Wyoming that supply a large percentage of Colorado River water are particularly low in snowpack right now, said Brenda Alcorn, a senior hydrologist for the river forecast center.
On StarNet: For more articles on our environment, visit: azstarnet.com/news/science/environment
DID YOU KNOW
The Central Arizona Project is a 336-mile network of pipelines and canals pumping Colorado River water uphill from Lake Havasu, in Western Arizona, south and east to Tucson. Its supply is dependent in part on the storage levels in Lake Powell.
The CAP is expected to run short at times, in part because the Colorado River is overallocated among seven states: Arizona, California, Colorado, Nevada, New Mexico, Wyoming and Utah.
A 1968 law authorized construction of the $3.6 billion project.
Contact Tony Davis at 806-7746 or tdavis@azstarnet.com
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