STORAGE COEFFICIENT

(1) For surface water, the relation of storage capacity in a reservoir to the mean annual flow of a stream above the dam forming the reservoir. (2) For ground water, primarily in a Confined Aquifer, it is a measure of the volume of water an aquifer releases from or takes into storage per unit surface area of the aquifer per unit change in head. This definition is similar to that of the Specific Yield for a water-table aquifer. However, confined aquifers remain saturated at all times and therefore water release in not met by drainage of the void spaces as is the case of an Unconfined Aquifer, but due to the change in pore pressure. Also referred to as the Storativity.