# Darcy's law (simplified)

## Description

Darcy’s law states that the volume of flow of the pore fluid through a porous medium per unit time is proportional to the rate of change of excess fluid pressure with distance. The constant of proportionality includes the viscosity of the fluid and the intrinsic permeability of the soil.

Civil engineers predominantly work on problems that involve water and predominantly work on problems on earth (in earth’s gravity). For this class of problems, civil engineers will often write Darcy’s law in a much simpler form where k is the hydraulic conductivity, and i is the hydraulic gradient. The hydraulic gradient is the rate of change of total head with distance.

Related formulas## Variables

v | flow velocity (Darcy's law) (m/s) |

k | hydraulic conductivity (m/s) |

i | hydraulic gradient (dimensionless) (dimensionless) |