The U.S. Army Corps Of Engineers announced on Thursday it’s making a surcharge spillway release from Norfork Dam to prevent an overtopping as water levels continue to rise from recent heavy rainfall.
Nine spillway gates will be open half a foot releasing approximately of 4,972 cubic feet per second.
The total release from the spillway and hydropower units will be around 10,500 c.f.s.
The spillway release will end after the flood pool crests and recedes to elevation 579’ per the water control plan.
The top of the flood pool on Norfork Lake is elevation 580. The flood pool is currently at elevation 579.59 and rising.
HISTORIC DATA: The pool of record at Norfork was set on April 11, 2008, at elevation 581.01. The next highest level was recorded on May 2, 2008, at elevation 580.9.
Surcharge storage is extra storage created by operation of an overflow spillway. On a lake with a gated spillway, as the gates open the top of gate rises giving a bit more storage space for the flood – this operation maximizes the storage while optimizing the release. On a lake with an ungated spillway, the spillway only flows if the lake rises above the spillway. Surcharge storage is the extra volume stored in the lake due to the rise above the spillway.