Where does transmissivity collide?

In hydrogeology, transmissivity is the rate at which water moves horizontally through the entire saturated thickness of an aquifer under a unit hydraulic gradient; it equals the hydraulic conductivity multiplied by the aquifer thickness and sets how much water a well can yield. Theis's 1935 The relation between the lowering of the piezometric surface and the rate and duration of discharge of a well using ground-water storage introduced the non-equilibrium analysis of well flow in which this aquifer property (originally called transmissibility) governs how the cone of depression spreads around a pumping well. The referent is a bulk conductance property of a water-bearing formation, measured in area per time, and it has nothing to do with how much light a filter or an atmosphere lets through beyond the shared root meaning of letting something pass.[1]

Unit

The volume of water transmitted through the aquifer's full thickness per unit width per unit hydraulic gradient (area per time, e.g. m²/day)

Recovery means

Not applicable

Measured by

Estimated from aquifer pumping (aquifer) tests by fitting time-drawdown data to the Theis or Cooper-Jacob solution

In optics and radiative transfer, transmissivity (often called transmittance) is the fraction of incident radiant energy that passes through a medium or surface rather than being absorbed or reflected, a dimensionless ratio between zero and one that follows from the attenuation of a beam along its path. Chandrasekhar's Radiative Transfer develops the theory of how radiation is attenuated, scattered, and transmitted through an absorbing medium, from which a layer's transmissivity is derived. The referent is a light- or radiation-throughput property of a material, filter, or atmospheric layer, obtained by comparing transmitted to incident flux, and it is entirely distinct from an aquifer's capacity to convey groundwater.[2]

Unit

Dimensionless fraction of incident radiant flux transmitted (0 to 1)

Recovery means

Not applicable

Measured by

Measured as the ratio of transmitted to incident radiant flux (e.g. spectrophotometrically), or modelled from the optical depth via Beer's law