Methods of drainage :-

1. Open or surface drainage

• It refers to the removal of surface water by developing the slope of land
• It is most common where water table is high
• Here 0.5 m wide channels are dug at a distance of 10 m. water from these channels is collected in main channel and drained out
• Here, channel occupies more space and make difficult for cultivation

2. Sub surface /underground drainage

• This is accompanied by the construction of tiles and open ditches which interrupt ground water and carry it off

a. Tile drainage :

• In this method, tiles of 30-60 cm/ 1-2 ft length and 10- 30 cm/ 4-12 inch diameter are led down 45-60 cm below the soil surface at distance of 2-5 m. tiles are short sections of pipe made from fixed clay or concrete
• Excess water enters the system through the spaces and drained out
• The hole of first tile must be closed
• High investment but no loss of land and easier cultivation

b. Plastic tube drainage :

• It is less expensive than tile drainage
• These tubes are laid down below the soil surface and water is drained out
• They may be 30.5 ft long or more

c. Porous/Perforated pipe drainage :

• The perforated plastic or polythene pipes are laid down under the soil surface and water enters into pipe by pores then drained out in desired area