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Concept
Watertable control
Résumé
In geotechnical engineering, watertable control is the practice of controlling the height of the water table by drainage. Its main applications are in agricultural land (to improve the crop yield using agricultural drainage systems) and in cities to manage the extensive underground infrastructure that includes the foundations of large buildings, underground transit systems, and extensive utilities (water supply networks, sewerage, storm drains, and underground electrical grids).
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: segmented regression).
In addition, land drainage can help with soil salinity control.
The soil's hydraulic conductivity plays an important role in drainage design.
The development of agricultural drainage criteria is required to give the designer and manager of the drainage system a target to achieve in terms of maintenance of an optimum depth of the water table.
Optimization of the depth of the water table is related to the benefits and costs of the drainage system (Figure 3). 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.
The optimization of drainage design and the development of drainage criteria are discussed in the article on drainage research.
Figure 4 shows an example of the effect of drain depth on soil salinity and various irrigation/drainage parameters as simulated by the SaltMod program.
Source officielle
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