For want of water: Another dry winter could push Trinity River too far

April 12, 2009

 

California's drought may push the Trinity River close to crisis this year, and it will take a lot of rain next winter to prevent that plight from getting far worse.

 

When Trinity Lake falls below a certain level, it may no longer be able to provide the frigid water to the river that's needed to keep salmon and steelhead healthy during a hot summer. Depending on whether the region sees more rain this spring, the lake could be drained close to that critical point -- but probably not until, fall when temperatures drop.

 

It is this coming winter that may spell real trouble. Should the drought continue, Trinity Lake won't fill up enough to meet demands on the system: the diversion to the Sacramento River and the Central Valley, the electricity that diversion produces, and fish in the river. What water there is may be too warm to ensure that salmon are protected in the river, as well.

 

”It will be difficult to meet all the requirements next year throughout the system,” said Brian Person, area manager for the U.S. Bureau of Reclamation, which operates the project.

 

The Trinity River Division of the Central Valley Project was completed in the 1960s to ship water to the Sacramento River, which is tapped for farms in the San Joaquin Valley. Early on, the diversion was as much as 90 percent, leaving the Trinity's fisheries in jeopardy.

 

After years of deliberations and litigation, a federal record of decision was put in place in 2001 that mandated the diversion be no more than 52 percent in an effort to restore salmon and steelhead.

 

That decision calls for a yearly determination on how much water should be released down the river and when. Extremely wet years call for huge releases of water in the spring meant to reshape the river and improve fish habitat, while dry years are meant to provide enough cold water for spawning and rearing needs.

 

Last week, the Trinity Management Council, which makes that determination based on a series of forecasts on snow and rain figures, classified the year as a “dry year.” That means 453,000 acre feet -- or 147 billion gallons -- is scheduled to be sent down the river, most of it during the spring.

 

If there is no more rain this year, that and the diversion to the Sacramento River will draw Trinity Lake down to about 600,000 acre feet by late fall. That's not likely to trigger a problem this year. But with the lake that low, it will take millions of acre feet of water flowing into the lake over the winter to bring the lake up far enough to keep it from falling below that level in the summer of 2010.

 

It's happened twice before. In 1977, the lake was far below that 600,000-acre-foot level and thousands of fish at Trinity River Hatchery died from diseases. In 1991, it dipped just below that level. The wetter years that followed, however, replenished the reservoir.

 

”You have to tackle these things on a year-to-year basis,” said Mike Hamman, executive director of the Trinity River Restoration Program run by the Bureau of Reclamation.

 

Some familiar with the complex operation of the project, however, are concerned that there is no real contingency plan to deal with an extended drought in the face of possible climate change. There are so many operational and regulatory constraints on the project that balancing them could be increasingly challenging in the future.

 

Among them are that the bureau must make sure that the water released down the river from Lewiston Dam is cold -- about 48 to 50 degrees -- in order to protect fish. It also has temperature requirements on the Sacramento River, and Trinity River water is used to help keep that river cold, too.

 

The plumbing of the project creates problems for meeting those requirements. Because water released to the Trinity River must first move through shallow Lewiston Lake, where it warms up during hot weather, more cold water must be released to dampen that effect. So summer flows of about 450 cubic feet per second to the river require that 1,500 to 1,800 cfs be released into Lewiston Lake.

 

The warmer the water released from Trinity Lake, the more difficult it is to keep that water cool. It may be possible to take water from the bottom of Trinity Lake, where it's coldest, but that bypasses the power plant. Even that won't be effective if Trinity Lake gets too low and too warm.

 

Trinity River fisheries advocates say that the problem could be avoided by keeping more in the lake each year, something they say the bureau is reluctant to do.

 

”There is no plan for the future to avoid a crisis,” said Tom Weseloh with California Trout.

Weseloh said that the group of stakeholders that make recommendations on operations recently suggested that the Trinity Management Council ask the bureau how it intends to comply with a 1990 State Water Resources Control Board order intended to protect the river. It demands that temperature requirements must first be met on the Trinity River.

 

National Marine Fisheries Service Arcata Area Office Supervisor Irma Lagomarsino said that if the lake is drawn down to below that 600,000-acre-foot level, the Bureau of Reclamation must confer with her agency and the U.S. Fish and Wildlife Service. But there is no hard-wired process to follow beyond that, Lagomarsino said.

 

Lagomarsino said that long-term discussions are necessary to address how much water is flowing to the Sacramento River and the Central Valley, adding that the diversion and river flows have exceeded the amount of water flowing into Trinity Lake for the past two years, which may constrain the operation of the system in the future.

 

”All of this is risk management,” Lagomarsino said.

 

The current scenario is something that former Trinity County Senior Planner Tom Stokely was warning about several years ago. Stokely now works with the California Water Impact Network, and said that the bureau has a number of regulatory issues that need to be cleared up before there is assurance that the Trinity River is protected in dire circumstances. Included in those, he said, are that the releases called for in the 2001 record of decision have not been written into key water rights permits.

 

”Until that's done,” Stokely said, “the Trinity's cold water supply remains at great risk.”

 

 

John Driscoll can be reached at 441-0504 or jdriscoll@times-standard.com.

 

THE PROJECT:

Trinity Lake, behind Trinity Dam, stores water from the Trinity River for release through Trinity Powerplant. Downstream, Lewiston Dam diverts water from the Trinity River, through the Lewiston Powerplant, into Clear Creek Tunnel for the 11-mile trip through the Trinity Mountains. Water enters Whiskeytown Lake through Judge Francis Carr Powerhouse. Some of the water diverts from the lake into the Clear Creek Unit South Main Aqueduct to irrigate lands in the Clear Creek Unit. The rest flows through the Spring Creek Power Conduit and Powerplant into Keswick Reservoir in the Shasta Division. From there, it goes through Keswick Powerplant, then south in the Sacramento River. The Wintu Pumping Plant diverts irrigation water from the Sacramento River into the Cow Creek Aqueduct and Unit.

 

Source: U.S. Bureau of Reclamation