[Water_news] 3. DWR'S CALIFORNIA WATER NEWS: WATERSHEDS - 8/30/07

Department of Water Resources

California Water News

A daily compilation of significant news articles and comment

 

August 30, 2007

 

3. Watersheds

 

Controversial canal's impact on Delta remains largely unknown

Stockton Record – 8/30/07

By Alex Breitler, staff writer

 

It is well-known that the words "peripheral canal" are linked with one of the California water world's most passionate and enduring debates.

 

What is not known, scientists said last week, is what such a canal might actually do to the Delta - its water quality, farms and fish.

 

"Regardless of what plan is put out there, uncertainty rules in this case," said Bill Bennett, a fisheries ecologist with the University of California, Davis.

 

Rejected by voters 25 years ago, some kind of canal or pipeline is again being considered by state officials who warn that the Delta cannot provide for all the competing demands for its water.

 

But many variables make the ultimate impact of the canal unclear. A panel of scientists in Sacramento last week talked about these unknowns, saying they would present the results of their discussions to decision makers.

 

The basics

 

A canal would divert water from the Sacramento River, perhaps near Hood, about 15 miles south of Sacramento, and route it around the east side of the Delta toward export pumps near Tracy.

 

Sacramento River water likely would be of higher quality than the south Delta water that is currently exported to two-thirds of Californians. And, in theory at least, a canal would protect the water supply should an earthquake or flood cause Delta levees to crumble.

 

Critics argue that a canal is a means to increase water exports in the future and abandon the Delta and its myriad problems.

While these high-profile arguments continue, scientists scratch their heads.

 

There are so many questions: How big would the canal be? Where would it draw from the Sacramento River, and how would that opening be screened to protect fish? What guarantee is there that an open-ditch canal won't be subject to the same failure as the levees?

 

"It's not just a simple engineering problem," said Michael Healey, lead scientist of the CALFED Bay-Delta Program. It is also a social, an economic and an ecosystem problem, Healey said.

 

Uncertain science

 

A canal may allow natural flows to return to the Delta, aiding declining fish, such as striped bass. On the other hand, taking half of the Sacramento River's flows during drought years could cause that river to run backward - the same phenomenon that has imperiled Delta smelt in the southern estuary, said Bennett, the fisheries biologist.

 

"It's quite likely that if we're not really careful about how we operate this thing, then the impacts on Delta smelt, particularly in a drought year, could be larger than they are now," Bennett said.

 

Dennis Majors, an engineer with the Metropolitan Water District in Southern California, said parts of the canal may be below sea level and thus subject to floods. Pockets of peat would have to be removed to keep the canal safe from earthquakes.

 

There are water quality concerns, too. Taking Sacramento River water around the Delta means the more contaminated San Joaquin River would contribute much of the flow into the estuary.

 

That could harm Delta farms that draw their irrigation water from the Delta's many rivers and sloughs.

 

The peripheral canal, however, could include siphons that "leak" into waterways it crosses, such as the Mokelumne River, to flush out those contaminants.

 

"Every option we have for the Delta has risk, and every option has benefits," said U.S. Geological Survey hydrologist Samuel Luoma.

 

'Uncertain but promising'

 

If built, a peripheral canal could allow more than 6 million acre-feet of water to be exported each year, comparable to export levels last year. That is enough water to fill New Melones Lake 21/2 times.

 

The cost would likely be $2 billion to $3 billion, with an environmental performance that is "uncertain but promising," according to a Public Policy Institute of California report issued earlier this year.

 

The report's authors suggested studying other options, including beefing up levees on certain islands to create a kind of freshwater corridor through the Delta.

 

The final unknown in this canal conundrum is what Delta conditions might be like in the future, said William Kimmerer, a research professor from California State University, San Francisco.

 

"We need to be flexible and adaptive," he said. "The system we're working with 10 years from now may be different" than today's. #

http://www.recordnet.com/apps/pbcs.dll/article?AID=/20070830/A_NEWS/708300315

####