One of the unwanted consequences of the line of winter storms that battered California for over two weeks was the flooding following in the wake of all the precipitation. Rivers and streams overflowed their banks, while the reservoirs filled up to capacity, and then some.
The Oroville Dam is the state’s second-largest reservoir, out of 1,300 named reservoirs in the state, and is a key part of the California State Water Project (SWP), one of two projects that set up the statewide water system. At 770 feet (230 meters) high, the earthfill embankment dam is the tallest dam in the United St}ates, ahead of the Hoover Dam, at 726 feet (221 meters) high.
Oroville Dam reaches full-capacity
The California State Department of Water Resources said in a statement that Lake Oroville reached full capacity at around 8:00 a.m. on Saturday morning. The dam’s 3,000-foot main spillway was being used for the controlled release of water, but on Tuesday this past week, the concrete spillway split open and is continuing to erode.
Water began flowing over the concrete lip of the adjacent emergency spillway shortly after, creating a steady, smooth spill across the 1,700-foot-wide lip of the emergency structure. Officials say that with dry weather expected over the next few days, the water level should fall below the emergency spillway by around 8:00 p.m. Monday night.
KCRA3.com reports that DWR Acting Director William Croyle said, “The flows we’re seeing are extremely low compared to the design of the structure. Based on our current situation, there is no threat.” The DWR is letting out 55,000 CFS on the damaged spillway to prevent further erosion.
They are also working to get the Hyatt Power Plant back in operation. Power generation was halted after water levels in the channel leading to the power plant became dangerously high and it was feared this would compromise operations at the power plant.
DWR reported that when the main spillway split open, debris and concrete chunks piled up in the channel going to the power plant. The debris also piled up against the towers holding the power lines, threatening to bring them down. DWR also says they expect to complete repairs on the eroded spillway by the start of the rainy season in October. It is estimated that repairs will run the state around $200 million.
Oroville crisis won’t be over anytime soon
The Sacramento Bee is reporting that Croyle says that California is on track to have the wettest winter ever, and there is an estimated 2.8 million acre-feet of snow blanketing the Sierras above the dam. Depending on when and how fast that snow melts is now a concern, especially with the repairs on the main spillway yet to be done.
“Our next 60 to 90 days will be critical, how we route this (snow) runoff through this reservoir,” Croyle said. “There’s a lot of snow up there.” But when all is said and done, Croyle feels the lower half of the main spillway will be ruined with the continued release of water needed to keep the reservoir from overflowing again. “In my opinion, it’s toast all the way to the bottom,” he said.
