In a confined aquifer (or aquitard), storativity is defined as the volume of water released from storage per unit surface area of the aquifer or aquitard per unit decline in hydraulic head.

In a confined aquifer (or aquitard), storativity is defined as the volume of water released from storage per unit surface area of the aquifer or aquitard per unit decline in hydraulic head.

• A. The water balance of the aquifer over a cycle
• B. The volume of water released from storage per unit surface area of the aquifer or aquitard per unit decline in hydraulic head
• C. The total porosity of the aquifer
• D. The rate of recharge required to maintain head

Answer: (B)

Storativity measures how much water a confined storage system can release for a given drop in hydraulic head. In a confined aquifer or aquitard, the water stored is under pressure, so when the head falls, water is released from storage mainly through the compressibility of the water and the aquifer material. The storativity per unit surface area is the volume of water released per unit area per unit decline in head, which makes it a dimensionless parameter equal to Ss times the aquifer thickness (S = Ss × b). Thus, the amount released for a head decrease Δh is S × Δh. This is the quantity described by the definition, unlike a general water balance over a cycle, the total porosity, or the recharge rate, which are different concepts.

Storativity measures how much water a confined storage system can release for a given drop in hydraulic head. In a confined aquifer or aquitard, the water stored is under pressure, so when the head falls, water is released from storage mainly through the compressibility of the water and the aquifer material. The storativity per unit surface area is the volume of water released per unit area per unit decline in head, which makes it a dimensionless parameter equal to Ss times the aquifer thickness (S = Ss × b). Thus, the amount released for a head decrease Δh is S × Δh. This is the quantity described by the definition, unlike a general water balance over a cycle, the total porosity, or the recharge rate, which are different concepts.