Why in the world would you release water from a dam during a flood?

Gauges monitoring water flow in the Russian River show a sharp increase in the amount released from Lake Mendocino for three hours Sunday morning, drawing scrutiny from residents along the river who closely monitor flows during floods.

The figures make no sense, said Pam Jeane, assistant general manager at the Sonoma County Water Agency, which was in charge of releases at Coyote Dam on Sunday. The agency did not release any water from the dam Sunday, she said, leading Jeane and her staff to conclude the gauge malfunctioned.

"We are a little bit mystified," Jeane said Monday. "We are thinking those numbers are not real."

The gauge meant to measure the release through Coyote Dam to the east fork of the Russian River showed a jump from 49 cubic feet per second to 1,532 cfs at 8 a.m. Sunday, before going back down to 56 cfs by 11 a.m.

The east fork joins the Russian River's west fork, which was already running at 11,700 cfs.

The Water Agency was in charge of Lake Mendocino releases at that time, because the lake level was still below the flood pool, the area that is set aside to hold water to lessen the impact of storms. The reservoir did not reach that level until 8 p.m. Sunday, 12 hours after the gauge reported a spike.

Downstream, swollen by rains in its 100-square-mile watershed, the Russian River was overflowing its banks in Ukiah, making the Perkins Street and Talmage Road crossings impassable.

Cars that were trying to cross were being washed away.

"There was no way to get from the east side to the west side for a period of time," said Sean White, executive director of the Russian River Flood Control and Conservation District. "I was at Perkins; there were some floating cars. There is always someone who has to drive through the big stand of flood water and doesn't make it."

At Hopland, the river was raging at 15,000 cfs, which is below flood stage but still inundates some low-lying roads.

Jeane said the Water Agency didn't order any releases from the lake. The U.S. Army Corps of Engineers, which controlled the valves, said its operators made no releases.

Further downstream, gauges in the Russian River at Talmage and at Hopland did not register any spikes, Jeane said. Those gauges should have detected a similar spike in flows if water had been released from the dam, she said.

"I have never seen it before. It looks very much like a flood release to me, except for the fact that it is very steep," said Jeane, referring to a graph of the releases. "It doesn't make any sense to me."

The gauge used to measure the releases from Lake Mendocino lake is a pressure transducer, which calculates the release by sensing water depth and river flow.

White agreed that a malfunction would be the logical explanation.

"It looks like a gauge error," White said. "There are other errors on the gauges that day. If you look at the Hopland gauge, there are flat spots on it. The system is not perfect."

You can reach Staff Writer Bob Norberg at 521-5206 or bob.norberg@pressdemocrat.com.