page_title: Drainage equation
section_title: Amplification
hierarchical_section_title: Drainage equation / Amplification
caption_attribution_description: Shape of the water table under subsurface drainage calculated with EnDrain model
context_page_description: 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.
  A well known steady-state drainage equation is the Hooghoudt drain spacing equation. Its original publication is in Dutch. The equation was introduced in the USA by van Schilfgaarde.
context_section_description: The drainage formula can be amplified  to account for (see  figure on the right):
  the additional energy associated with the incoming percolation water (recharge), see groundwater energy balance
  multiple soil layers
  anisotropric hydraulic conductivity, the vertical conductivity (Kv) being different from the horizontal (Kh)
  drains of different dimensions with any width (W)
caption: EnDrain: shape of the watertable with drainage
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