- If excess water saturates the pore space of soil, the process of its removal by downward flow through the soil is known as sub surface drainage.
- Sub surface drains are underground artificial channels through which excess water may flow to a suitable outlet.
1) Unlike open drainage; land is not wasted and there is no interference to farming operations by subsurface drainage.
2) This system requires less maintenance.
1) Require high initial investment
2) Failure of the system is difficult to detect.
3) This system is ineffective in soils with low permeability.
4) Inlets and outlets should be maintained properly.