What is the Difference Between Permeability and Porosity?

Permeability and porosity are related properties of rocks or loose sediments, both of which are influenced by the number, size, and connections of openings in the material. However, they represent different aspects of the material's ability to hold and transmit fluids:

• Porosity is a measure of the void spaces in a material. It is calculated by dividing the open space in a rock by the total rock volume (solid and space). Porosity describes the soil or rock's capacity to hold water.
• Permeability is a measure of the ability of a material (such as rocks) to transmit fluids. It is related to the ease of flow of a fluid through a porous solid. Permeability refers to how connected pore spaces are to one another, and it is the rate of water movement through interconnected pores within soil.

The connection between porosity and permeability is that the more porous the soil is, the higher its permeability, provided the pores are interconnected. However, permeability is not solely determined by porosity; it also depends on the size and shape of soil particles and their packing or arrangement. For example, clay has a high porosity but low permeability because its pores are not connected, while gravel and sand have both high porosity and permeability, making them good aquifer materials.

Comparative Table: Permeability vs Porosity

Here is a table comparing the differences between porosity and permeability:

In summary, porosity refers to the percentage of open spaces or voids within a volume of soil or rock, while permeability is the rate of water movement through interconnected pores within soil. Both properties are related and affect the flow of water through soil or rock, but they are not inversely related.