Watertable control
From WaterWiki
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Controlling the water table | |
 Subsurface land drainage aims at controlling the water table 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 drainage. In agricultural land drainage, the purpose of water table control is to establish a depth of the water table that does no longer interfere negatively with the necessary farm operations and crop yield yields (Figure, made with SegReg program, see segmented regression]. Optimization of the depth of the water table is related the benefits and costs of the drainage system. The shallower the permissible depth of the water table, the lower the cost of the drainage system to be installed to achieve this depth. However, the lowering of the originally too shallow depth by land drainage entails side effects. These have also to be taken into account, including the costs of mitigation of negative side effects. An overview of the effects (both positive and negative) of water table control can be found in Chapter 17: "Agricultural Drainage Criteria" of ILRI publication 16: "Drainage Principles and Applications" that can be viewed and downloaded from the ILRI-Alterra website or from : [1] . | |
 Historically, agricultural land drainage started with the digging of relatively shallow open ditches that that received both runoff from the land surface and outflow of groundwater. Hence the ditches had a surface as well as a subsurface drainage function. By the end of the 19th century and early in the 20th century it was felt that the ditches were a hindrance for the farm operations and the ditches were replaced by buried lines of clay pipes (tiles), each tile a about 30 cm long. Hence the term "tile drainage". Later, land drainage became a powerful industry. At the same time agriculture was steering towards maximum productivity. As a result, many modern drainage projects were over-designed while the negative environmental side effects were ignored. In circles with environmental concern, the profession of land drainage got a poor reputation, sometimes justly so, sometimes unjustified, notably when land drainage was confused with the more encompassing activity of "wetland reclamation". Nowadays, in some countries (not in all), the hardliner trend is reversed. An article on "Agricultural land drainage: a wider application through caution and restraint" can be viewed and downloaded from : [2]. | |
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Chapters of ILRI publication 16 on "Drainage Principles and Applications" can be viewed in: Various articles and softwares on Waterlogging and Land drainage can be freely downloaded from:
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