The volume of water an aquifer releases from or takes into storage per unit surface area of the aquifer per unit change in head.
It is a volume of water per volume of aquifer released as a result of a change in head. For a confined aquifer, the storage coefficient is equal to the product of the specific storage and aquifer thickness.
This is a measure of the volume of water stored and released in an aquifer and is used to quantify the safe yield of an aquifer system.