## Physical Properties Of Aquifers

As stated before, an aquifer serves as an underground storage reservoir for water. It also acts as a conduit through which water is transmitted and flows from a higher level to a lower level of energy. An aquifer is characterized by the three physical properties: hydraulic conductivity, trans-missivity, and storativity.

### Hydraulic Conductivity

Hydraulic conductivity, analogous to electric or thermal conductivity, is a physical measure of how readily an aquifer material (soil) transmits water through it. Mathematically, it is the proportionality between the rate of flow and the energy gradient causing that flow as expressed in the following equation. Therefore, it depends on the properties of the aquifer material (porous medium) and the fluid flowing through it.

Transmissivity

Transmissivity is the physical measure of the ability of an aquifer of a known dimension to transmit water through it. In an aquifer of uniform thickness d, the transmissivity T is expressed as

where K represents an average hydraulic conductivity. When the hydraulic conductivity is a continuous function of depth

d Jo

When a medium is stratified, either in horizontal (x) or vertical (y) direction with respect to hydraulic conductivity as shown in Figure 9.1.5, the average value K can be obtained by

Direction of flow

Direction of flow

Direction of flow

Direction of flow

FIG. 9.1.5 Permeability of layered soils.

FIG. 9.1.5 Permeability of layered soils.

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