Yesterday there were some false-alarm rumors that there had been a catastrophic failure of the spillway at Oroville Dam, fed by some dramatic photos of a controlled release of water down the damaged spillway. While that erosion damage is going to require an expensive fix, we learn today that as the lake is reaching 98 percent capacity, per the Chronicle, and officials have been hoping not to have use a never-before-used, unpaved emergency spillway at the other end of Lake Oroville, which would lead to unknown and potentially catastrophic impacts for the salmon fishing industry because of the cloudy water that will be unleashed into the adjacent Feather River.
The dam and primary spillway, constructed in the 1960s, remain functional and there is no danger to the public from the damaged spillway, as officials from California's Department of Water Resources explained Thursday, though each release of water has caused further damage to the concrete waterway and sent water spilling down the adjacent hillside.
The emergency spillway is another story, however, and if put into use will lead to tons of trees and debris being swept down into the river and the Feather River Hatchery below, as the Chronicle reports, potentially killing off millions of unhatched steelhead salmon eggs that are vital to the fishing industry salmon hatched here end up being released and caught all along the Pacific coast. Already, four million baby salmon have been caught in nets and trucked downstream, but millions more remain vulnerable.
The hatchery, and potentially a year's worth of salmon fishing, appear to be the biggest potential casualties as officials try to keep Lake Oroville under control.
Per the Chronicle:
The open concrete pools outside the hatchery, where the millions of evacuated fish lived — and where millions more still were trapped — take in water right from the river and were swamped with filth. The delicate fish eggs, which must be incubated in cold, clear water, are kept farther inside the facility behind filter defenses.
But the filters proved feeble in the face of the turbidity, and scientists inside scrambled to figure out how to safely mix tap water, which contains enough chlorine to kill the fragile eggs, with the cloudy river water that wasn’t much safer.
KTLA has data as of midnight Thursday showing the current contents of Northern California's reservoirs, with Lake Oroville, second in size only to Lake Shasta, at 144 percent of its historical average, and Shasta at 133 percent of its average. Lake Oroville hit 98 percent of capacity due to all the rain and runoff from the Sierra, while Lake Shasta was at 92 percent as of last night.
The Sacramento Bee reports Friday that officials now "think they can avoid using the dam's emergency spillway, which they've been working feverishly to avoid." In addition to risks to fish in the Feather River, there are potential flood risks for communities downstream as well.
Perhaps catastrophe has been avoided, and now the Department of Water Resources just has to brace for the next storm and deal with repairing the damaged spillway down the line. According to the Sac Bee, "The dam was releasing about 40,000 cubic feet of water per second Thursday afternoon... including about 35,000 cfs from the damaged main spillway. But that was not enough to compensate for the 190,000 cfs pouring into the reservoir from continued storms in the vast Sierra Nevada watershed that feeds the Feather River and its tributaries."