California
Related: About this forumRain prompts reopening of fractured Oroville Dam spillway as state races to finish repair plan
Even as they finalize plans to repair Oroville Dams damaged spillway, state water managers say continued rain and snowmelt means the fractured structure will need to keep doing its job for now.
The California Department of Water Resources plans to reopen the spillway gates Friday morning for the first time since March 27. Acting DWR Director Bill Croyle, speaking to reporters Thursday, said dam operators expect to run the spillway for 10 to 14 days, shut it off for inspections, and then run it again one more time this spring.
In all likelihood, Croyle said repairs on the spillway are likely to start in late May or early June. Until then, he said DWR will focus on reducing lake levels to around 835 feet "to anticipate that snowmelt and the storms that keep coming." The latest storms have elevated lake levels to around 863 feet.
DWR is attempting to strike a balance between lowering the lake level as much as possible and shutting off the spillway for good in order to begin repairs. As it is, Croyle has acknowledged that spillway repairs won't be complete until sometime next year, and the 3,000-foot-long concrete chute will remain partially unfixed through the next rainy season. Still, he said the spillway, despite the enormous damage that's occurred since the initial fracture Feb. 7, will be functional next winter.
Read more here: http://www.fresnobee.com/latest-news/article144500114.html
Rollo
(2,559 posts)And there isn't much that can be done about that.
Oroville Dam's built-in design flaws will continue to bedevil the operators.
At least they made some progress and can run the generator turbines again, which can drain about 1/10th of the maximum that an intact spillway could. Better than nothing.
But the dam has been mis-managed.
Cracks that appeareed about 10 years ago were "repaired" without addressing the underlying cause(s).
A recommendation to revamp the emergency spillway was ignored.
I guess the management figured the drought would last forever.
Oroville is not secured at this point. More warm rain this weekend. More snow melt. The dam still might fail. Read up on "California Megaflood", which happened back in 1861, and innundated the entire Central Valley with up to 30 feet. Dams like Oroville might help to avert a repeat, but not if their spillways can't be used as needed.
DK504
(3,847 posts)Like reservoirs? Kinda lame idea, but damn.....
How is Mono, Shasta, LA reservoir...what else is the big lake?
Rollo
(2,559 posts)That would involve pumping the water out of the lake, since the spillways are both compromised. And I doubt there exist pumps big enough to make a dent in the lake level.
Lake Shasta, I believe, is full. As are many other California reservoirs at present. They are being managed to spill enough water to lower their levels now to avoid problems when the snow melt starts. If the spring brings warm rains, then it could be a big problem, esp at Oroville.
Some are actually proposing to let the Central Valley flood in order to recharge the depleted aquifer there. It was depleted over the past decade or more by excessive ground water pumping. That depletion has lowered the land level considerably in some places. But since the Central Valley has become far more populated than it was in 1861, when the main residents were cattle, flooding it on purpose would not only be politically unwise but also inhumane and very expensive. However there are flood plains around the Sacramento area which likely are vast ponds right now. That's what they are designed to do. I think they are also rice growing areas. The highways in those areas are quite elevated, probably at least 40 feet above ground level, for many miles.
In general big reservoirs are a good answer to flood control. Except when the design is bad, as wtih Oroville. Then they can cause a bigger disaster than no reservoir at all.