There's trouble all around the state, but this is massive:
- Inside the frantic fight to protect Oroville dam, nation's tallest, as spillway rapidly erodes
Officials have stressed that the dam itself suffered no damage and that the spillway problems don’t pose a imminent threat to the public. Still, they have been frantically working to reduce the amount of water in the Lake Oroville reservoir, which is near capacity. It’s now at about 96% of capacity, and more water has been flowing in than is draining out.
- Officials say Oroville Dam not compromised but are preparing for the worst
As the concrete from the spillway falls into the Diversion Pool and Lake Oroville continues to fill, the California Department of Water Resources is sending about 35,000 cfs of water continually down the broken spillway.
Some of the water in the Diversion Pool is routed through the Thermalito Forebay and Afterbay where it warms before being used for crops. The rest, about 40,000 cfs as of Thursday, goes directly into the Feather River.
The river flows parallel to Montgomery Street, one of downtown Oroville’s main streets. Right now, the only thing separating the 40,000 cfs of water in the Feather River from flooding the downtown part of the city is about a hundred yards and a levee that holds back the water.
Eric See, a public information officer with the Department of Water Resources, said 150,000 cfs went through the Feather River in Oroville during a storm in 1997.
- Use of untested emergency spillway yet again a possibility at crippled Oroville Dam
The Department of Water Resources announced it was dialing back water releases over the battered main spillway by about 15 percent to keep erosion along the side of the spillway from “compromising” the power line towers that fuel the dam’s power plant. That reduced releases to 55,000 cubic feet per second.
With that, the possibility that the reservoir would crest the lip of the emergency spillway was raised anew. The slower releases “may keep the lake level below 901 feet,” the point at which water would start topping the emergency structure, the department announced. However, “there are many variables involved, and the public should not be surprised if some water flows into the emergency spillway.”
- Damage to Oroville Dam spillway worsens — could cost $100 million
“We’re going to lose a lot of the spillway,” said Chris Orrock, a spokesman for the California Department of Water Resources, which manages the nation’s tallest dam, about 75 miles north of Sacramento. “The director has said we are willing to lose the bottom of that spillway to make sure we maintain flood control for the downstream communities.”
The good news, Orrock said, is that the larger spillway, made of reinforced concrete, was peeling downward and not threatening the integrity of the 770-foot-high dam itself. “If the erosion was moving up toward the dam, they would stop the flow,” he said.
The dam’s spillway — and valves in the Edward Hyatt Power Plant at the bottom of the reservoir — were releasing 79,000 cubic feet per second of water Friday, but the flow was reduced overnight. About 130,000 cubic feet per second was flowing into the dam from the surrounding mountains.
If it were not damaged, the spillway could usher out up to 200,000 cubic feet per second of water, though that flow would be too much for the Feather River, which can handle 150,000 cubic feet per second without flooding.
- At Oroville Dam, a break in the storms gives engineers hope
The break in storms and a drop in the volume of water pouring into the huge reservoir gave dam operators hope that they could keep lake levels from hitting an elevation of 901 feet — the point at which uncontrolled flows would start washing down an unpaved emergency spillway that has never been used in Oroville’s 48-year history.
“The sun is coming out. The rain has stopped. The inflow has peaked,” said Eric See, a spokesman for the state Department of Water Resources. “We still don’t expect to use the auxiliary spillway.”
Indeed, here in the Bay Area, 250 miles away, the sun is shining and it's a beautiful day, and there's no rain in the forecast.
Well, no rain in the forecast for the next 4 days.
Then the next storm is looming.
It's going to be a very, very, very busy spring for the entire state.
After so many years of below-average rainfall, it's a vivid reminder that California's enormous flood control projects were built for a reason: the peculiar geography of the state positions the entire Central Valley as a giant bathtub, 500 miles long and 60 miles wide, draining a region of over 60,000 square miles.
There's nowhere we can put all that water at this point; all the reservoirs are full.
And the enormous snowpack in the mountains hasn't even begun to melt yet; the real flooding season typically starts in mid-March and runs well through April. We're a full month ahead of schedule; the worst is DEFINITELY yet to come.
So, for the next 3 months at least, as all that snow melts, and runs down from the mountains, it's going to be one flood-control crisis after another.
Hold on for a wild ride.
And best of luck to the hard-working folk at the DWR; pack some extra thermoses of coffee: you're going to be booking a LOT of overtime between now and Memorial Day.