control drainage:

* Adding structures such as flashboard risers in outlet canals to control the residence time of irrigation water in the root zone: When these structures are removed, subsurface drainage takes place more rapidly and the amount of water in ditches decreases. This technique permits not only to manage the level of water in fields but also allows maximum storage of water within the field for utilization by the crop.
* A more advanced form of control drainage consists of underground drainpipes that are connected to