The risk of catastrophic flooding in the Lake Tulare basin has diminished as lower temperatures spread this spring, state officials said Monday, flattening the Sierra’s epic snowmelt curve.
“We’re not anticipating nearly as severe damage as we’ve been anticipating for several weeks,” Brian Ferguson, deputy director of crisis communications for the California governor’s office of emergency services, said at a news conference Monday. “However, we want to strongly emphasize that we are not out of the woods by any stretch of the imagination.”
Just a few weeks ago, officials worried that floodwaters from the melting glaciers of the Sierra Nevada would run down the Tully, Kings, Kaweh and Kern rivers, overturning berms, overflowing dams and inundating towns like Corcoran and Stratford.
They now say their most conservative models do not project the lake’s height to exceed 184.1 feet above sea level — well below the 192 feet of the newly reinforced dam to protect Corcoran, and about two feet lower than the forecast they gave on April 21.
In fact, Mehdi Mizani, principal engineer for the Tulare Lake Basin Water Resources Department, said the latest models indicate water levels will reach about 181.1 feet on May 31, flooding nearly 620,000 acres.
In 1983, one of the last few times the lake was flooded, nearly a million acres (approximately 85,000 acres) were flooded.
Mizani said the state’s models include the combined effects of weather, reservoir releases, agricultural requirements and evapotranspiration, though they don’t take into account the reliability or strength of dams — which can affect the extent of floods if they fail.
He said the modeling process is “iterative”. He and his team are “constantly working on improvements to the models, whether it’s just calibrating the models themselves or better understanding local processes to make sure we’re capturing those models correctly.”
The cool spring so far has helped ease flood fears, UCLA climatologist Daniel Swain agreed.
“We’ve been relatively lucky so far,” Swain said during a news briefing on Monday. “We threaded that needle—there was a lot of water coming down the slopes—but it didn’t come down all at once.”
However, the threat of a “Big Melt” remains a cause for concern as much of the deepest snowpack in the southern Sierra Nevada has not yet melted.
“There’s still a huge amount of water out there, and I think people have forgotten that because at low to mid elevations, the snow has pretty much melted away,” Swain said.
“But at higher elevations, where the vast majority of the actual snow water equivalent is, there are still huge snowpacks — they’re still clearing roads in the High Sierra right now that have 20 to 30 feet of snow on them” at 8,000 to 10,000 feet. .
He said temperatures are beginning to rise and some areas along the Merced River in Yosemite National Park are under flood watch and warnings as high flows are expected in the next few days.
The main area of concern, he said, remains the basin of Lake Tulare, which has no outlet and is still full of deep, stagnant waters from this year’s winter storms. Although an atmospheric warm river event or a prolonged heat wave could lead to major flooding in the area, the gradual melting of snow threatens to make the current flooding worse.
“There’s still a lot of concern about Corcoran and some of these towns that are literally within that basin,” Swain said. “Farmland in that area will be flooded for several months, and there remains a high risk to populated areas in parts of the San Joaquin Valley for at least the next few weeks, and possibly the next two months.”
Ferguson said the state is stocking up on sandbags and other emergency equipment in case the weather changes.
“While I think the most serious risks may have been averted, we don’t know what we don’t know,” Ferguson said, pointing to the many variables that can affect the speed, strength and amount of water flowing through rivers.
“So while you know I think the more serious danger may have been averted, we don’t know what we don’t know yet in terms of how fast the water can go down the mountain, what dams might have squirrels in them that I’m not aware of or a million other things we don’t control.” necessarily as human beings.
“And so as we look away, much better than we have been in the past, we just want to emphasize that the public in these communities should continue to be aware of the challenges that lie ahead and that we will continue to be in this situation for at least the month of July.”
2023 Los Angeles Times.
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