 Subsurface land drainage  aims at controlling the water table of the groundwater in originally waterlogged land at a depth acceptable for the purpose for which the land is used.The depth of the water table with drainage is "greater" than without.In agricultural land drainage, the purpose of water table control is to establish a depth of the water table (Figure 1) that does no longer interfere negatively with the necessary farm operations and crop yields (Figure 2, made with the SegReg model, see the page