Methods of Irrigation and its subsystems
Any irrigation system or Methods of Irrigation and its subsystems would consist of the following four subsystems :

  • (i) The water supply subsystem which may include diversion from rivers or surface
    ponds or pumped flow of ground water.
    (ii) The water delivery subsystem which will include canals, branches, and hydraulic
    structures on these.
    (iii) The water use subsystems, which can be one of the four main types, namely, (a)
    surface irrigation, (b) subsurface irrigation, (c) sprinkler irrigation, and (d) trickle
    (iv) The water removal system i.e., the drainage system. In this section, the water use subsystems have been described.

Water Use Subsystems
Irrigation water can be applied to croplands using one of the following irrigation methods :

Each of the above methods has some advantages and disadvantages, and the choice of
the method depends on the following factors :

  • (i) Size, shape, and slope of the field,
    (ii) Soil characteristics,
    (iii) Nature and availability of the water supply subsystem,
    (iv) Types of crops being grown,
    (v) Initial development costs and availability of funds, and
    (vi) Preferences and past experience of the farmer.

The design of an irrigation system for applying water to croplands is quite complex and not amenable to quantitative analysis. Principal criteria for the design of a suitable irrigation method are as follows :

  • (i) Store the required water in the root-zone of the soil,
    (ii) Obtain reasonably uniform application of water,
    (iii) Minimise soil erosion,
    (iv) Minimise run-off of irrigation water from the field,
    (v) Provide for beneficial use of the runoff water,
    (vi) Minimise labour requirement for irrigation,
    (vii) Minimise land use for ditches and other controls to distribute water,
    (viii) Fit irrigation system to field boundaries,
    (ix) Adopt the system to soil and topographic changes, and
    (x) Facilitate use of machinery for land preparation, cultivating, furrowing, harvesting,and so on.