Eastern Sierra Flooding Threatens Los Angeles Water Lifeline
For more than 100 years, the Los Angeles Aqueduct has endured earthquakes, flash floods and dozens of bombings as it winds and weaves through the canyons and deserts of the east of the Sierra Nevadas.
But earlier this month, record storms accomplished the unthinkable when floodwaters undermined a 120-foot-long section of aqueduct in the Owens Valley, causing its concrete walls to collapse.
“We have lost the aqueduct! a Los Angeles Department of Water and Power inspector told superiors by cellphone. As he spoke, runoff and chocolate-colored debris undermined the aqueduct just west of Highway 395 and the community of Olancha.
It was the first time in history that the 200-mile aqueduct was breached by extreme weather, threatening water deliveries to 4 million ratepayers in Los Angeles.
It also showed how difficult it would be to defend the waterway against the torrential runoff of a winter when snowfall is near record highs. For weeks, DWP crews used heavy equipment and other means to control the predicted spring runoff, but even longtime aqueduct workers were shocked by the suddenness of the rupture.
Among the first to arrive on the scene that morning of March 10 was a team led by Ben Butler, who was in charge of the aqueduct and the reservoir.
“The flood water was coming down hard, creating a large deep pool that leaned against the walls of the aqueduct,” he recalls. “We went as far as we could, then we put on waders and headed for the breach.”
For the next five days, rescuing the Los Angeles aquatic lifeline became the DWP’s highest priority as all hell broke loose in Owens Valley.
Traditionally dry rocky arroyos and ditches crowded their banks; irrigation diversions and culverts were buried in mud the consistency of peanut butter. At Pleasant Valley Dam, about 8 miles north of the town of Bishop, sediment-laden stormwater surged over its spillway and into the Owens River at a rate of 1,000 cubic feet per second.
“We were already in all-in-one mode when we learned that the aqueduct was having serious problems,” said Adam Perez, assistant manager of operations for the aqueduct. “At 3 p.m. that afternoon, we came up with a game plan to prevent further deterioration, repair the breach and maintain service.”
As an emergency action, the DWP opened aqueduct spill valves 25 miles to the north to drain the damaged section and make repairs.
These massive outings were not without consequence, however. The released water flooded ranches at the bottom of the valley, as well as a half-mile stretch of State Highway 136 just south of the community of Lone Pine, and surged toward expansion land of Owens Lake, where it caused more problems.
The lake, once navigated by steamboats, had evaporated into dusty salt pans after the aqueduct was completed in 1913. In recent years, the DWP has spent $2.5 billion on projects to to prevent particles harmful to the health of the bottom of the lake from spreading through the air.
But as aqueduct surges flowed down the playa, they were dissolving alkaline minerals there, creating a vast pool of corrosive brine that could ruin some dust control projects, officials said.
All in all, it took more than 100 DWP staff working non-stop for almost a week to repair the aqueduct. Their job was to replace the damaged concrete walls and coat them with a special mixture of cement, sand, fibrous materials and adhesives that dry faster and harder than conventional concrete.
“It was not easy to manage so many boots on the ground in a short time in adverse conditions,” Perez said. “Ultimately, the damage did not affect any communities in the area.”
Nodding appreciatively to the Sierra snowmelt cargo flowing high and fast through the repaired section of the channel on Thursday, he added: “Our crews did a great job.”
Looking ahead, he said, DWP inspectors will step up daily patrols of its waterworks and dam systems in the Owens Valley.
In the wake of the crisis however, critics point to the breach and subsequent flooding of the valley floor as signs that the DWP is losing control of its massive and complex aqueduct infrastructure amid the related extreme weather conditions. to the climate.
A singular feat of civil engineering and deception, the aqueduct both spurred the phenomenal growth of Los Angeles and inspired deep-seated suspicions about the city’s motives that persist in Owens Valley to this day.
Most of its water is diverted from the Owens River, which flowed through a valley inhabited for thousands of years by Paiute Indians before white settlers occupied their land.
In 1905, Los Angeles city agents posing as ranchers and farmers acquired most of the land and water rights in the Owens Valley and construction of the tunnel, conduit and reservoir system began in 1907.
By the early 1920s, tensions were rising in the area over the city’s continued acquisitions. In three years, the aqueduct has been blown up more than a dozen times.
On September 15, 1976, a dynamite explosion tore through one of the five gatehouse gates of the Alabama Hills Aqueduct, throwing 100 million gallons of water into the valley floor.
Today, the chatter in local cafes and watering holes revolves around whether the DWP will be up to the task of managing the flood levels expected this spring and summer.
Some residents are encouraged by the sight of DWP-owned earthmoving caravans and dump trucks loaded with rocks and mud rumbling to and from the floodplains.
“We’ve had a lot of rain, snow and temperature swings lately,” said Dan Siegel, owner of Merry-go-Round restaurant in Lone Pine. “I think the DWP has done a good job considering the number of places that need their equipment and manpower.”
Regarding forecasts of potentially massive flooding when temperatures climb into the 80s and 90s, “We won’t know how badly we’re in until we know how fast the snow is melting,” he said. Siegel.
The DWP system is beginning to show signs of age. In recent years, several sections of the aqueduct system have been drained to allow the replacement of cracked and bulging sections of concrete that are centuries old.
Since severe storms began battering the eastern Sierra region in January, the DWP has relied on tactical strategies developed during epic rains that ended a five-year drought in 2017.
DWP crews rush to clear clogged culverts, divert excess runoff to pastures and sage plains, and build berms to direct floodwaters from small towns straddling US Highway 395, including Olancha, Cartago, Lone Pine, Big Pine and Bishop.
Gazing out over the snow-capped Sierra peaks to the west, Perez said, “If all that snow is falling hot and heavy when the weather gets warmer, the challenge will be to protect communities in the Owens Valley from flooding.”
There is a bright side to the situation, however: For the first time in six years, Los Angeles can expect to receive the majority of its water from the aqueduct at least until late fall, said Perez.
Just a year ago, at the end of the worst drought in 1,200 years, the aqueduct supplied about 13% of the city’s water supply, with most of the rest purchased from the State Water Project and the river. Colorado.
Los Angeles Times