` = "Hooghoudt's equation"`

Enter a value for all fields

The Hooghoudt's equation calculator computes a steady state drainage rate based on a number of factors as follows.

INSTRUCTIONS: Choose units and enter the following:

• (Kb) hydraulic conductivity of the soil above drain level
• (d) equivalent depth
• (Di) depth of the impermeable layer below drain level
• (Dd) depth of the drains
• (Dw) steady state depth of the waterable midway between the drains
• (Ka) hydraulic conductivity of the soil
• (L) spacing between the drains

Hooghoudt's equation (Q): The drainage rate is returned in meters per second (m/s).  However, these can be automatically converted to compatible units via the pull-down menu.

The Math / Science

Hooghoudt's equation is a drainage 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 Hooghoudt formula It is: 

`Q=(8*Kb*d(Di-Dd)(Dd-Dw)+4*Ka(Dd-Dw)^2)/L^2`,

where:

• `Q` = steady state drainage discharge rate
• `Ka` = hydraulic conductivity of the soil above the drain level
• `Kb` = hydraulic conductivity of the soil below the drain level
• `Di` = depth of the impermeable layer below drain level
• `Dd` = depth of the drains
• `Dw` = steady state depth of the watertable midway between the drains
• `L` = spacing between the drains
• `d` = equivalent depth

References

Wikipedia (https://en.wikipedia.org/wiki/Drainage_equation)