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A drainage equation is an equation describing the relation between depth and spacing of parallel subsurface drains, depth of the watertable, depth and hydraulic conductivity of the soils. It is used in drainage design.
The checked surface drainage systems consist of check gates placed in the embankments surrounding flat basins, such as those used for rice fields in flat lands. These fields are usually submerged and only need to be drained on certain occasions (e.g., at harvest time). Checked surface drainage systems are also found in terraced lands used for ...
Groundwater recharge or deep drainage or deep percolation is a hydrologic process, where water moves downward from surface water to groundwater. Recharge is the primary method through which water enters an aquifer. This process usually occurs in the vadose zone below plant roots and is often expressed as a flux to the water table surface.
An example of a criterion factor is the depth of the water table: A drainage system influences this depth; the relation between drainage system design and depth of water table is mainly physical and can be described by drainage equations, in which the drainage requirements are to be found from a water balance. [1]
Example of a surface water balance: An example is given of surface runoff according to the Curve number method. [3] The applicable equation is: Osu = (Rai – Ws) 2 / (Pp – Ws + Rm) where Rm is the maximum retention of the area for which the method is used Normally one finds that Ws = 0.2 Rm and the value of Rm depends on the soil ...
Drainage options for the construction industry include: Point drainage, which intercepts water at gullies (points). Gullies connect to drainage pipes beneath the ground surface, so deep excavation is required to facilitate this system. Support for deep trenches is required in the shape of planking, strutting or shoring.
Spacing equations of subsurface drains and the groundwater energy balance applied to drainage equations [5] are examples of two-dimensional groundwater models. Three-dimensional models like Modflow [6] require discretization of the entire flow domain. To that end the flow region must be subdivided into smaller elements (or cells), in both ...
The energy balance of groundwater flow can be applied to flow of groundwater to subsurface drains. [2] The computer program EnDrain [3] compares the outcome of the traditional drain spacing equation, based on Darcy's law together with the continuity equation (i.e. conservation of mass), with the solution obtained by the energy balance and it can be seen that drain spacings are wider in the ...