Fluid conductance

Fluid conductance is related to the rate at which a unit of material can transmit fluids, and is used mainly in hydrology in relation to river and lake bottoms. It is an application of intrinsic permeability to a unit of material with a defined area and thickness. In hydrology, the magnitude of conductance affects the rate of recharge or interaction with groundwater. This parameter is often used in such computer modelling codes as MODFLOW.

Example

For example, the conductance of water through a stream-bed is:

<math>C_b = K \frac{A}{b}</math>

where

<math>C_b</math> is the conductance of the stream-bed ([L²T^-1]; m²s⁻¹ or ft²day⁻¹)

<math>K</math> is the hydraulic conductivity of the stream-bed materials([LT^-1]; m·s⁻¹ or ft·day⁻¹];

<math>A</math> is the area of the stream-bed ([L²]; m² or ft²)

<math>b</math> is the thickness of the stream-bed sediments ([L]; m or ft)

The volumetric discharge through the stream-bed can be calculated if the difference in hydraulic head is known:

<math>Q_b = C_b (h_b - h)\,</math>

where

<math>Q_b</math> is the volumetric discharge through the stream-bed ([L³T^-1]; m³s⁻¹ or ft³day⁻¹)

<math>h_b</math> is the hydraulic head of the river (elevation stage)

<math>h</math> is the hydraulic head of the aquifer below the stream-bed ([L]; m or ft)