Storage coefficient or storativity in an unconfined aquifer is equal to which term?

Storage coefficient or storativity in an unconfined aquifer is equal to which term?

• A. Specific yield
• B. Porosity
• C. Hydraulic conductivity
• D. Permeability

Answer: (A)

In an unconfined aquifer, changes in storage are dominated by the drainage of water from the pore spaces as the water table falls. The portion of pore volume that can drain under gravity is called specific yield, so the storativity (storage coefficient) is essentially equal to the specific yield. Porosity is the total pore space, which includes water that may not drain; hydraulic conductivity and permeability describe how easily water can move, not how much water is stored. Thus storage in an unconfined aquifer is governed by the amount of water that can drain, i.e., the specific yield.

In an unconfined aquifer, changes in storage are dominated by the drainage of water from the pore spaces as the water table falls. The portion of pore volume that can drain under gravity is called specific yield, so the storativity (storage coefficient) is essentially equal to the specific yield. Porosity is the total pore space, which includes water that may not drain; hydraulic conductivity and permeability describe how easily water can move, not how much water is stored. Thus storage in an unconfined aquifer is governed by the amount of water that can drain, i.e., the specific yield.