The duty of water depends upon following factors.

1. Soil characteristics through which canal runs.

  • If canal is unlined and soil through which it flows is coarse grained.
  • Seepage and percolation losses will be too much and duty of water will be reduced.
  • If on the other hand canal is either lined or runs through fine grained soil.
  • The losses will be considerably small and duty of water will be more.

2. Soil characteristic of fields.

  • If soil of the field is deep coarse grained, percolation losses will be more.
  • If, however, a hard pan is present at a depth of 1 or 2 m.
  • The percolation losses will be less and duty will be more.

3. Undulated fields.

  • If fields which are to be irrigated are quite undulated, the duty of water will be less.
  • Lower portions are filled with more water whereas higher portions get less depth of water.

4. Climatic conditions.

  • Temperature, wind, rainfall and humidity are the climatic conditions which affect the duty of water.
  • High winds, high temperature, less rainfall and less humidity conditions.
  • Require more of irrigation water and duty is thus reduced.
  • If rainfall is taken into consideration while calculating duty figures.
  • It is known as Duty inclusive of rainfall.
  • If rainfall is not considered it is called Duty exclusive of rainfall.

5. Base period of the crop.

  • The crops having longer base period, require waterings for longer time and thus duty will be less and vice-versa.

Factors affecting duty

6. Depth of water or Delta.

  • The crops which require lesser overall depth (Delta) of water have more of duty.
  • Delta is different for different crops.
  • Hence duty of water depends upon type of crop.

7. Method of application of irrigation water.

  • Method of application of irrigation water affects duty figures.
  • Flood irrigation has lesser duty than Furrow irrigation.
  • Sub-irrigation methods give highest duty.

8. Preparation of fields.

  • If fields are prepared by deep ploughs, the water retention capacity of the unsaturated zone of soil gets increased.
  • When such soils are irrigated, although they require more of water for irrigation, but the number of waterings are reduced.
  • This also helps in increasing the duty, to some extent.

9. Position of fields in relation to canal.

  • If fields are situated very near to the canal supplying water for irrigation.
  • Conveyance losses beyond outlet will be small and duty of water will be more.

10. Method of assessment.

  • Assessment of irrigation if done on volumetric basis, the duty of water is bound to increase.
  • If assessment is done on irrigated area basis.
  • The farmers do not use water carefully and thus duty becomes low.

11. Longitudinal slope to fields.

If fields are given a little longitudinal downward slope towards the farther end, duty of water is increased.

12. Awareness of farmers.

  • If farmers are made to understand the importance of irrigation water.
  • They use it more judiciously in their fields without allowing water to go waste.
  • It helps in increasing the duty of water.
  • Farmers maintain their water courses free from grass and other weed growths and do not allow water to go waste anywhere.
  • If water courses are lined and levels of water courses for each field are kept as per requirements.
  • the duty of water increases considerably.
  • In lined water courses having regular longitudinal slope,
  • all the water coming out of outlet rushes to fields with more velocity