What is dam dead storage?
Dam dead storage is the volume of water which is below the level of the spillway or other outlet. In other words, the volume of water that cannot be released from a dam (unless the dam wall bursts). The capacity, volume or storage of a reservoir is usually divided into distinguishable areas.
Dead or inactive storage refers to water in a reservoir that cannot be drained by gravity through a dam’s outlet works, spillway or power plant intake and can only be pumped out. Most dams have multiple options for discharge. The lowest usually is a penstock. Lets say your lowest penstock opening is at 1770 feet above mean sea level. The lowest point of the riverbed upon which the dam is built is 1720′ msl. All the water from 1720′ to 1770′ msl is “dead storage” water because it can never be accessed.
It usually does not account for much on a percentage basis in the reservoir, but it must be accounted for in storage projections. -David Stevens, former Engineering Director
At the same, while doing these projections, it is important to make sure that all the regulations are taken into account to ensure the proper functioning of a dam.