ABSTRACT
Traditionally these systems consist of a network of deeply installed field drains (1-2 m below the land surface) establishing a deep drainage base in the soil, well below the main rootzone. In the drain the soil water potential is effectively zero so that all groundwater above the drainage base has a higher potential and is under gradient to flow towards and into these drains. Low watertable depths may be maintained by selecting a combination of suitable drain spacing and drain depth. Provided the downward movement of excess water is not impeded, the overlying soil profile will drain to field capacity.
