The most important properties of the aquifer are porosity and specific yield which in turn give its capacity to release the water in the pores and its ability to transmit the flow with ease.
[1] The significance of the porosity is that it gives the idea of water storage capacity of the aquifer.
The pores in the soil hold back sufficient quantity of water on account of forces like surface tension and molecular attraction.
Hence the actual amount of water that can be extracted from the unit volume of aquifer by pumping or under the action of gravity is called as specific yield.
Coarse-grained soils or rocks such as coarse sandstone can have specific yields that are closer to their actual porosity in the range 20 to 35%.