FACTORS AFFECTING DUTY
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.
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