Dam drains, fish killed
By Jesse Phelps

A hiker wandering through the backcountry behind Matilija Dam last week discovered a disturbing phenomenon. The water in the reservoir behind the dam seemed to be dramatically lower than she remembered. Then, taking her camera out, she found something else. There, next to the structure, floating in the water, were hundreds of dead fish.

The fish, mostly largemouth bass, died when a faulty valve allowed hundreds of acre-feet of water out of the reservoir and down the channel, according to Casitas Municipal Water District fish biologist Leo Lentsch.

"There was a faulty valve that caused some release of water from the reservoir," Lentsch said in a telephone interview on Monday. "That happened over a period in July. I can't pinpoint a date for you, probably right around the third of July, we had a faulty valve they worked on repairing. After that, we were still having some trouble with it."

He denied reports that human error was the cause of the loss of water and fish, instead blaming old equipment at the dam site.
"It's an old facility so from time to time they have trouble with different components up there," Lentsch said. The result, he said, was that the water "released a little quicker out than the volume that was coming in."

As the volume of water coming in is quite low during the hot Ojai summers, the reservoir has gone down dramatically over the weeks since the valve started leaking.

In fact, said Lentsch, the water levels are so low at this time of year that Casitas won't usually divert from the river at all during the summertime. Nothing has changed that, he said, even the excess water running down the channel due to the leak. "None of the water lost down the creek was diverted to the lake," he said.

The Robles diversion dam in the Ventura River channel - several miles below the dam near Meiners Oaks - is used to pipe river water to Lake Casitas during wetter periods each year.
The resulting effect of the extra runoff, said Lentsch, is that parts of the watershed usually dry have recovered some moisture. "I have some temperature gauges out a couple of places. By Willis Canyon, it had dried up but now it's wet again," said Lentsch.

Lentsch said the fish died because of a lack of oxygen. "The water's so warm up there it's dominated by green sunfish and largemouth bass. Probably what happened is they got crowded together and the large ones, because they consume more oxygen, they perished," he said, adding that the bass are "not native to the drainage and they do impact steelhead because they feed on them."

Until a fish passage is constructed, no steelhead can penetrate the canyon beyond Robles, so, at least for now, the bass are not a concern.

Meanwhile, according to Lentsch, the only fish affected are the ones dying in the reservoir. "I did a survey of the channel and pool down below Matilija and I didn't find any dead fish down there," he said. "Up above the dam there were some large largemouth bass that did perish. I estimate it around 50. There were still a lot of live fish up there as well."

Pictures taken by a hiker would seem to belie Lentsch's estimate but no firmer figure yet exists to tally the loss. "When we are diverting, we monitor everything as best we can. We don't check everything on a daily basis," said Lentsch.

Steve Wickstrom, chief engineer at the district, was putting a comprehensive report on the water loss together for board of directors. Lentsch said he would be able to provide technical details regarding the valve and why it was leaking but Wickstrom could not be reached for comment.

© 2003 The Ojai Valley News

Back to the news