Hopes for salmon spawn this season in Putah Creek dimming

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By Todd R. Hansen
McNaughton Media

The poor water quality that killed off dozens of Chinook salmon in the lower end of Putah Creek continues to persist, and hopes that salmon could still make their way up the creek in the latter weeks of the spawning season are souring fast.

Rich Marovich, the retiring streamkeeper for the Lower Putah Creek Coordinating Committee and the Solano County Water Agency, said in a phone interview Friday that the water in a 9-mile stretch of the east levee toe drain into the Yolo Bypass Wildlife Area remains high in organic material and low on oxygen.

The area of concern is from Interstate 80 to the stair-step area of the refuge.

Testing of the Prospect Slough area of the drain on the other side of the interstate and in the stair-step area is good, Marovich said.

Marovich, in an interview during the first week of November, had hoped the situation would be resolved by now, and had it been, it would have left plenty of time for at least a partial salmon run through December into January.

“We may get lucky. We could get a real cold snap, which would help, or we could get another rain event,” Marovich said.

He said the Solano County Water Agency, which actually has no authority over the affected area but has invested millions into creek restoration – in part – to improve salmon spawning habitat, is looking into other alternatives.

But just releasing more water to flush the system is not a “prudent option” for the district.

One option is to find a partner to trade water so more would be available to help flush out the system. Marovich said chaining open the flaps at the Lisbon Weir also could help the situation by allowing more tidal push into the area.

But ultimately, Marovich said, the issue is to find a way to manage agricultural water practices.

There are 23 entities that take water from the toe drain, but they are under no regulatory obligation to monitor how much organic material they are putting back into the drain – a fluid known as “black water.”

The microbes that eat the organic material also use up the oxygen in the water, creating a dissolved oxygen level that cannot support fish – especially salmon. But even the hardier carp and striped bass did not survive this event.

Just keeping the water on the fields for a while longer might be a solution, Marovich noted, adding the Suisun Marsh had a similar issue some years back and that was one of the solutions then.

The good news is that it has reached a point in the season that water diversion and release back into the drain is all but over, and that will help, too.

Marovich credits the water agency, and specifically Alex Rabidoux, the principal water resource engineer, for taking on the issue and investigating possible solutions when the agency is under no obligation to do so.

“This is all a discretionary effort by the agency,” Marovich said. “They do see some self-interest in this, but it was not inevitable or obvious that they would have to take the next step and investigate the water quality in the toe drain.”

In the meantime, it does not seem likely there will be a salmon spawn this winter.

Marovich said what that means for the years to come is uncertain, but he said there should be enough fish that were born in the creek in recent years that should be making their way back into the creek. Stray fish also could repopulate the creek, he said.

“But our goal is to have natal origin fish,” Marovich said.

Fish born in the creek that return four or five years later are specifically imprinted to Putah Creek, creating its own species of salmon and strengthening the line for years to come.

Seventy-six salmon were killed when the heavy Oct. 24 rains dislodged loads of organic material and caused an overflow from the east levee toe drain into the Yolo Bypass Wildlife Area. It is possible that as many as two dozen of the fish, however, perished because beavers had stopped the flow of water before their dams could be breached, Marovich said at the time.

When the refuge then used that water to flood rice fields for waterfowl habitat, some of that water spilled into Putah Creek. The extra organic material in the water does not affect waterfowl, but salmon are sensitive to oxygen levels.

Only four salmon are known to have traveled upstream to spawning areas since the boards at the Los Rios Check Dam were removed Nov. 2.

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