Yuba OK, for most part
The Yuba River looks healthy overall, but has some trouble spots where water quality isn’t what it should be.
And scientists are still trying to understand what caused the high Enterococcus bacteria readings that prompted no-swim advisories last summer on the South Yuba.
That’s according to a two-hour presentation given Sunday at the Madelyn Helling Library about a citizens’ river-monitoring program.
Since October 2000, volunteers from the South Yuba River Citizens League have taken monthly water samples from the south, middle and north forks of the Yuba River and the main stem Yuba, which are tested for a number of things.
On Sunday, SYRCL ecologist Lynell Garfield and Fraser Shilling, a biologist from the University of California at Davis, talked about test results from the first year of the study.
“I’m not really surprised at any of the numbers we’ve seen,” Garfield told an audience of about 20 people.
Garfield and Shilling said testing was done at 21 sites; a few sites didn’t meet water quality standards.
One area of concern is the amount of oxygen in the river water, Shilling said.
“The reason we’re concerned about this is, aquatic organisms use oxygen to live, just like we do,” Shilling said. Water can hold a varying amount of oxygen, depending on temperature and altitude.
The state has set a goal for tributaries of the Sacramento River, such as the Yuba, of 85 percent dissolved oxygen – the amount of oxygen in the water – or higher. If river water falls below 75 percent dissolved oxygen, that’s cause for concern, Shilling said.
Only three sites tested low for dissolved oxygen: below Jackson Meadows Reservoir on the Middle Yuba, and above and below Spaulding Reservoir.
It’s “not a surprising thing” that dissolved oxygen tested low below the reservoirs, because there’s a lot of oxygen depletion at the bottom of a reservoir, Shilling said.
The state Water Resources Control Board has set a water temperature goal of 68 degrees Fahrenheit for the Yuba River. Temperatures exceeded that last summer on the lower South Yuba, the lower North Yuba and main stem Yuba.
Water is diverted out of the South Yuba at Spaulding Reservoir, which raises the river’s temperature, Shilling said. Higher temperatures “might be a natural condition for this watershed … but probably not,” he said.
The main stem Yuba below Englebright Dam can be much cooler than the South Yuba because cold water from Bullards Bar Reservoir passes through Englebright Reservoir.
When the Yuba County Water Agency released water from Englebright in July and August to sell to Southern California, the temperature dropped 10 to 13 degrees, instantly attracting salmon, Garfield said.
“Within one day, (temperatures) dropped and the fish moved up,” she said.
Other findings included high levels of suspended solids coming from Humbug Creek, which drains Malakoff Diggings and looks like “mocha” during storms, Shilling said.
And arsenic levels were high in Kanaka Creek, a Middle Yuba tributary.
Scientists are still working to figure out this summer’s high Enterococcus levels, Garfield said. SYRCL will release a 60-plus-page report in a week or two giving details about the Enterococcus situation.
The presentation was sponsored by the Sierra Nevada Deep Ecology Institute.
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