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,"
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,"
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.
The Ojai Valley News
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LARGEMOUTH bass float at the Matilija Dam outlet.