Drainage of Agricultural Lands - Practices of Irrigation and On-farm Water Management - page 332

WT

Fig. 9.2 Schematic of deep open drain

• where a suitable outlet is available to dispose of the quantity and quality of water

collected

• where it can be used as alone or with other system ( as outlet of normal surface

drain)

Deep open drain has the potential in turning salt-affected land into productive. It
directs surface and subsurface water away from the landscape, taking with it the salt
that has accumulated in the soil.

Buried Pipe Drain

A network of perforated tubes or pipes is installed 0.8-1.5 m below the soil sur-
face. The excess water from the root zone flows into the pipe through the openings
(Fig. 9.3 ) . The pipes convey the water to a collector drain. A gentle slope of the
pipe (0.5-1.0%) is provided toward the collector drain. The drain pipe may be made
of plastic, concrete, or clay. These tubes are commonly called “tiles” because they
were originally made from short lengths of clay pipes known as “tiles.” In clay and
concrete pipes, water enters the pipes through the small spaces between the tiles,
and drain away. In plastic pipes, water enters into the drain through perforation dis-
tributed over the entire length of the pipe. The buried pipe lowers the water table to
the depth of the pipe or tiles over the course of time (several days).

Typical Length of Different Pipe Drain

Plastic: 100-200 m long, 10-15 cm diameter
Clay and concrete: 25-30 m long, 5-10 cm diameter.

9.1.6 Merits and Demerits of Deep Open and Buried Pipe Drains

There are some merits and demerits of each of the drain systems - deep open and
buried pipe drain. They are summarized below: