As of 4pm the lake level continues to rise, now at 663.79. Discharge has increased to over 103,000 cfs. Subtracting 35,000 cfs for flow available through the turbines, means 68,000 cfs is passing through the flood gates. The 12 flood gates are each capable of releasing 13,503 cfs for a total of 162,036 cfs.
By these numbers we can estimate that all 12 flood gates are open approximately 42%.