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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. Parameters in Hooghoudt's drainage equation. A well known steady-state drainage
To get an IDF curves from a probability distribution, it is necessary to mathematically isolate the total amount or depth of the event , which is directly related to the average intensity and the duration , by the equation =, and since the return period is defined as the inverse of (), the function is found as the inverse of (), according to:
[2] [3] In hydrology, a water balance equation can be used to describe the flow of water in and out of a system. A system can be one of several hydrological or water domains, such as a column of soil, a drainage basin, an irrigation area or a city. The water balance is also referred to as a water budget. Developing water budgets is a ...
Due to the non-linearity of the equation, numerical techniques such as the non-linear least-squares method can be used to solve the van Genuchten parameters. [4] [5] The accuracy of the estimated parameters will depend on the quality of the acquired dataset (and ). Structural overestimation or underestimation can occur when water retention ...
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 ...
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. Channel drainage, which intercepts water along the entire run of the channel.
According to Montgomery and Dietrich’s equation, drainage density is a function of vertical hydraulic conductivity. Coarse-grained sediment like sand would have a higher hydraulic conductivity and are predicted by the equation to form a relatively higher drainage density system than a system formed by finer silt with a lower hydraulic ...
The drain discharge determines the drain spacing IEFF = 1 − (Osu + Dtr + Oaq − Rai − Lca − Iaq) / Irr Likewise the safe yield of wells , extracting water from the aquifer without overexploitation , can be determined using the geohydrologic water balance or the overall water balance , as defined in the section "Combined balances ...