Fluid conductance
Encyclopedia
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 groundwater recharge or interaction with groundwater
. This parameter is often used in such computer modelling codes as MODFLOW
.
through a stream-bed is:
where
is the conductance of the stream-bed ([L2T-1]; m2s−1 or ft2day−1)
is the hydraulic conductivity
of the stream-bed materials([LT-1]; m·s−1 or ft·day−1];
is the area of the stream-bed ([L2]; m2 or ft2)
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:
where
is the volumetric discharge through the stream-bed ([L3T-1]; m3s−1 or ft3day−1)
is the hydraulic head of the river (elevation stage)
is the hydraulic head of the aquifer
below the stream-bed ([L]; m or ft)
See also: Vascular resistance
Hydrology
Hydrology is the study of the movement, distribution, and quality of water on Earth and other planets, including the hydrologic cycle, water resources and environmental watershed sustainability...
in relation to river
River
A river is a natural watercourse, usually freshwater, flowing towards an ocean, a lake, a sea, or another river. In a few cases, a river simply flows into the ground or dries up completely before reaching another body of water. Small rivers may also be called by several other names, including...
and lake
Lake
A lake is a body of relatively still fresh or salt water of considerable size, localized in a basin, that is surrounded by land. Lakes are inland and not part of the ocean and therefore are distinct from lagoons, and are larger and deeper than ponds. Lakes can be contrasted with rivers or streams,...
bottoms. It is an application of intrinsic permeability
Permeability (fluid)
Permeability in fluid mechanics and the earth sciences is a measure of the ability of a porous material to allow fluids to pass through it.- Units :...
to a unit of material with a defined area and thickness.
In hydrology, the magnitude of conductance affects the rate of groundwater recharge or interaction with groundwater
Groundwater
Groundwater is water located beneath the ground surface in soil pore spaces and in the fractures of rock formations. A unit of rock or an unconsolidated deposit is called an aquifer when it can yield a usable quantity of water. The depth at which soil pore spaces or fractures and voids in rock...
. This parameter is often used in such computer modelling codes as MODFLOW
MODFLOW
MODFLOW is the U.S. Geological Survey modular finite-difference flow model, which is a computer code that solves the groundwater flow equation. The program is used by hydrogeologists to simulate the flow of groundwater through aquifers...
.
Example
For example, the conductance of waterWater
Water is a chemical substance with the chemical formula H2O. A water molecule contains one oxygen and two hydrogen atoms connected by covalent bonds. Water is a liquid at ambient conditions, but it often co-exists on Earth with its solid state, ice, and gaseous state . Water also exists in a...
through a stream-bed is:
where
is the conductance of the stream-bed ([L2T-1]; m2s−1 or ft2day−1) is the hydraulic conductivityHydraulic conductivity
Hydraulic conductivity, symbolically represented as K, is a property of vascular plants, soil or rock, that describes the ease with which water can move through pore spaces or fractures. It depends on the intrinsic permeability of the material and on the degree of saturation...
of the stream-bed materials([LT-1]; m·s−1 or ft·day−1];
is the area of the stream-bed ([L2]; m2 or ft2) is the thickness of the stream-bed sediments ([L]; m or ft)The volumetric discharge
Discharge
Discharge in the context to expel or to "let go" may refer to:* A military discharge, issued when a member of the armed forces is released from service* Termination of employment, the end of an employee's duration with an employer...
through the stream-bed can be calculated if the difference in hydraulic head
Hydraulic head
Hydraulic head or piezometric head is a specific measurement of water pressure above a geodetic datum. It is usually measured as a water surface elevation, expressed in units of length, at the entrance of a piezometer...
is known:
where
is the volumetric discharge through the stream-bed ([L3T-1]; m3s−1 or ft3day−1) is the hydraulic head of the river (elevation stage) is the hydraulic head of the aquiferAquifer
An aquifer is a wet underground layer of water-bearing permeable rock or unconsolidated materials from which groundwater can be usefully extracted using a water well. The study of water flow in aquifers and the characterization of aquifers is called hydrogeology...
below the stream-bed ([L]; m or ft)
See also: Vascular resistance
Vascular resistance
Vascular resistance is a term used to define the resistance to flow that must be overcome to push blood through the circulatory system. The resistance offered by the peripheral circulation is known as the systemic vascular resistance , while the resistance offered by the vasculature of the lungs...