From the Department of Water Resources:
Lake Oroville is expected to rise this morning to the level that allows water to flow down an emergency spillway and into the Feather River, according to the California Department of Water Resources (DWR). The volume of water is expected to pose no flood threat downstream and should remain well within the capacity of the Feather River and other channels to handle. Oroville Dam itself remains safe, and there is no imminent threat to the public.
The emergency spillway has not been used since the dam was finished in 1948, but DWR has anticipated and prepared for its use since Tuesday, when erosion opened a cavity on the concrete, gated spillway typically used in winter operations at Lake Oroville. DWR continues to use that damaged spillway to discharge 55,000 cubic feet per second, but the approximately 95,000 cfs inflow to the lake exceeds that discharge. As of 4 a.m., the lake level was .7 feet away from the 901 foot elevation at which water flows over a concrete weir and into the unlined emergency spillway. That event is expected to happen within hours.
DWR and CAL FIRE crews in past days have been clearing trees and brush from the path water is expected to take in the emergency spillway, which is an unlined hillside. The emergency spillway flows are expected to wash large amounts of soil and debris into the Feather River, and crews are positioned to remove as much debris as possible from the channel immediately downstream of the dam.
The total flow of water from the reservoir, including the emergency spillway, is expected to be on the order of half of downstream flood system capacity and consistent with releases made at this time of year in wet years such as this. While DWR does not expect flows to exceed downstream channel carrying capacity, the rate of flow into the ungated emergency spillway may change quickly.
DWR is coordinating closely with state and federal wildlife and dam safety officials at Oroville Dam. Those involved in contingency planning and response include the Federal Energy Regulatory Commission, the U.S. Army Corps of Engineers, Butte County Sheriff’s Office, Pacific Gas and Electric Company, the Governor’s Office of Emergency Services, the state’s Division of Safety of Dams, CAL FIRE and state and federal wildlife agencies.
Lake conditions, including lake levels, inflows, and outflows can be obtained via a recorded message at 530-534-2307. More information is available here at http://cdec.water.ca.gov/cdecapp/resapp/resDetailOrig.action?resid=ORO.
NOTE: I will be adding pictures to this post today as soon as I find some, so check back here for those later today. I will, of course, send out a breaking news alert if something significant happens.
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