Unsaturated hydraulic conductivity. The energy equation for flow through a single pore or a series of pores can be written in terms of pressure only.
Velocity head is negligible and elevation change within a single pore is negligible.
The term, k, is a shape factor and was shown to vary between 2 and 3 for different shapes of cross-sections. The equation can be rewritten in the format shown in the conservation of energy lectures. Darcy's law for flow through soils, and Mannings equation for flow in channels because the length of the flow path and the flow rate are in the numerator and the diameter of the tube is in the denominator. In addition, the length of the flow path should be multiplied by the ratio of the average flow path length to the tortuous flow path length. The greater the eccentricity of the pore space, the greater will be the value of .