Heavy soils of low hydraulic conductivity often require very closely spaced drainage systems for satisfactory water control. With conventional pipes, the cost of such systems is usually uneconomic and hence alternative techniques are required. Surface drainage is one possibility; the other is mole drainage.

Mole drains are unlined circular soil channels which function like pipe drains. Mole drains are formed with a mole plough, which comprises a cylindrical foot attached to a narrow leg, followed by a slightly larger diameter cylindrical expander. The foot and expander form the drainage channel and the leg generates a slot with associated soil fissures which extend from the surface down into the channel.

The number and size of the leg fissures produced with a given mole plough are dependent upon soil conditions. The success of a mole drainage system is dependent upon satisfactory water entry into the mole channel and stability of mole channel for an acceptable period. Currently, mole drainage systems are most commonly used for surface water control in perched water table situations.Mole drains are also used in some groundwater problem areas and in paddy fields. Their use as a temporary subsurface drainage system for the reclamation of saline and saline sodic soils has been successful in field experiments

Their major advantage is low cost, and hence they can be installed economically at very close spacing. Their disadvantage is their restricted life, but, providing benefit-cost ratios are favourable, a short life can be acceptable.