According to this : Louisville District > Missions > Civil Works > Water Information > Updated Lake Temperatures and Dissolved Oxygen Lev > Barren Profile

... the greatest O2 drop occurs from 12ft to 14ft deep, and any depth below 14ft is a dead zone. The biggest temp drop occurs from 10-14ft ( a 5deg F. drop from 78 to 73deg F.)
Now, these reading ARE taken at the dam, so depths and readings may differ in other areas of the lake.