International Commission on Irrigation & Drainage Commission Interationale des Irrigation et du Drainage



Subsurface Drainage

As the name suggests, subsurface drainage, either natural or artificial, is beneath the ground surface. Subsurface drainage systems are used when the drainage problem is mainly that of shallow water tables.The subsurface field drainage systems can also be differentiated asregularsystems andcontrolledsystems; andhorizontal or vertical systems.

 

The subsurface field drainage systems consist of horizontal or slightly slopingchannelsmade in the soil; they can be open ditches, trenches, filled with brushwood and a soil cap, filled with stones and a soil cap, buried pipe drains, tile drains, or mole drains, but they can also consist of a series ofwells.Thefield drains(orlaterals) discharge their water into the collector or main system either bygravityor bypumping.

 

Subsurface drainage by wells is often referred to asvertical drainage, and drainage by channels ashorizontal drainage, but it is more clear to speak of "field drainage by wells" and "field drainage by ditches or pipes" respectively.The open dug wells ortube wells have normally to be pumped, but sometimes they are connected to drains for discharge by gravity.

 

When the drain discharge takes place entirely by gravity, both regular and controlled types of subsurface systems have much in common, except that thecontrol systems have gates that can be opened and closed according to need. When the discharge takes place bypumping, the drainage can be checked simply by not operating the pumps or by reducing the pumping time. Acontrolled drainage system reduces the discharge through the main drainage system, thereby reducing construction costs.They can also save much irrigation water.

 

Modern buried pipe drains often consist of corrugated, flexible, and perforated plastic pipe lines wrapped with a envelope or filter material to improve the permeability around the pipes and to prevent entry of soil particles, which is especially important in fine sandy and salty soils. The surround may consist of geotextile.

Related items you may like

Irrigation

Dictionary - Subsurface Drainage Terms

Sign up for newsletter

Follow us