Aquitard

An aquitard is an underground geological formation which contains water but significant amount of water cannot be extracted using water wells. Aquitard comprises of generally layers of clay soil with low hydraulic conductivity.

Aquifuge

It is a geological formation which is incapable to absorb or transmit water through it. Thus it is an impermeable formation.

Homogeneous and isotropic medium

A porous medium is called homogeneous when aquifer parameters are constant throughout the medium, i.e. the properties of the medium are independent of space (Fig. 1.7(a)). The medium will be called non-homogeneous when aquifer properties are varying with space (Fig. 1.7(b)).

Fig. 1.7 (a) Homogeneous aquifer (b) Non-homogeneous aquifer

A porous medium will be called isotropic when medium parameters are constant in all the directions, i.e. the parameters are independent of direction (Fig. 1.8(a)). The medium will be called an anisotropic when the parameters are different in different directions (Fig. 1.8(b)).

Fig. 1.8 (a) Isotropic aquifer (b) Anisotropic aquifer