Aquifer properties include the porosity, permeability, specific yield, and storage coefficient of an aquifer. Porosity is the measure of the void spaces in a rock or sediment that can store water. Permeability is the measure of the ease of flow of water through the sediment or rock. Specific yield is the amount of water that will drain under the effect of gravity when an aquifer is completely saturated, and the storage coefficient is the amount of water that can be stored in an aquifer.