1. Factors affecting Duty and Improvement Measures
L.D. College of Engineering, Ahmedabad-15

2. Group members: Sr. No. Name Enrollment No. 1. Patel Pranjal 2.
Patel Vaibhav 3.
Patel Vedant 4.
Patel Vishesh 5.
Patni Mo.Aamir

3. Content Introduction Factors affecting duty Measures to improve duty
References

4. Introduction
The term “Duty” means the area of land that can be irrigated with unit volume of irrigation water.
Quantitatively, duty is defined as the area of land expressed in hectares that can be irrigated with unit discharge, that is, 1 cumec flowing throughout the base period, expressed in days.
Imagine a field growing a single crop having a base period B days and a delta ∆ mm which is being supplied by a source located at the head (uppermost point) of the field, as shown in next slide.

5. Introduction (cont..) [Furrow Irrigation method of applying water]
[Water applied to field by pumping ground water]
[Border Irrigation method of applying water]

6. Introduction (cont..)
If the water supplied is just enough to raise the crop within D hectares of the field, then a relationship may be found out amongst all the variables as:
Volume of water supplied = B*60*60*24 cum
Area of crop irrigated = D*10000 sqm
Volume of water supplied per unit area = =
86400B
10000D
8.64B D
Hence, knowing two of the three variables B, D and ∆ the third party may be found out.

7. Factors affecting Duty
Type of soil
Coarse grained soil
Percolation losses are high
Low duty
Fine grained soil
Percolation losses are less
High duty

8. Factors affecting Duty (cont..)
Type of crop
Crop A
Large quantity of water
Low duty
Crop B
Less quantity of water
High duty

9. Factors affecting Duty (cont..)
Structure of Soil
Good structure is called Good Tilth of Soil
Good structure
Evaporation losses are less
High duty
Good structure
Properly aerated because of large voids
Yield of crop increases

10. Factors affecting Duty (cont..)
Steep slope
d/s portion get more water
u/s portion remain drier
Low duty
Slope of Ground
Flat slope
u/s portion remain drier
d/s portion get more water
Low duty
Properly prepared field
Equal distribution of water
High duty

11. Factors affecting Duty (cont..)
Climatic Conditions
Temperature and wind velocity are high
more evaporation losses
Low duty
Rainfall during base period
Less irrigation requirement
High duty

12. Factors affecting Duty (cont..)
Not properly ploughed & method of cultivation is faulty & less efficient
Low duty
Method of Cultivation
Properly ploughed & made quite loose
water retention capacity increase
number of watering reduced
High duty

13. Factors affecting Duty (cont..)
System of Irrigation
Non-perennial
Only during flood season
wasteful use of water
Low duty
Perennial
Water application throughout the growth period
soil remains continuously wet
less quantity of water
High duty

14. Factors affecting Duty (cont..)
Canal Irrigation
Command area far from source
Transmission losses are more
Low duty
System of Irrigation
Tank Irrigation
Command area closed to tank
Transmission losses are less
High duty

15. Factors affecting Duty (cont..)
Flow Irrigation
Command area far from source
Less expensive
Low duty
System of Irrigation
Lift Irrigation
Command area close to well
More expensive
High duty

16. Factors affecting Duty (cont..)
Drip Irrigation
Most efficient
Very high duty
Application of Water
Sprinkler Irrigation
Seepage losses are reduced
High duty
Surface irrigation
More waste of water
Low duty
Duty of subsurface methods > Duty of surface methods

17. Factors affecting Duty (cont..)
Initial stages of cultivation
land not properly levelled
Low duty
Age and frequency of cultivation
Age of cultivation increases
Slope and condition of land improve with age
High duty
Frequent cultivation
Reduces loss of moisture
High duty
Cultivation after long interval
More loss of moisture
Low duty

18. Factors affecting Duty (cont..)
Canal A
In good condition & properly maintained
High duty
Condition, type and location of Canal
Canal B
In unconcerned condition & not maintained
Low duty
Canal A
Located in middle of command area
Losses are small
High duty
Canal B
Located away from command area
Losses are more
Low duty
Duty of Lined canal > duty of unlined canal
Duty of canal in alluvial soil > duty of canal in non-alluvial soil

19. Factors affecting Duty (cont..)
Flat rate based assessment
Wastage is more
Low duty
Method of assessment of Water
Volumetric assessment
Cultivators use water carefully
Less wastage
High duty
Cultivators
Skilled & properly trained
Make judicious use of water
High duty
Skill of Cultivators

20. Factors affecting Duty (cont..)
Long base period
More water required
Low duty
Base period
However it is not always proportional
Soil
Contains harmful salts and alkalis
More water required for leaching of salts
Low duty
Soil Content

21. Measures for Improvement of Duty
Land should be properly ploughed
Land should be regularly cultivated
Canal alignment in sandy soils or in fissured rocks should be avoided
Canal should be located in the middle of command area
Canal should be lined
Canal should be properly maintained
Efficient methods of irrigation should be adopted

22. Measures for Improvement of Duty (cont..)
Volumetric assessment of water should be adopted
Cultivators should be trained
System of rotation of crops should be adopted
Canal alignment through soil containing harmful salts should be avoided
Instead of a single big canal, two or more parallel canals of small size should be preferred
Adopt modern methods of irrigation instead of conventional methods
Cultivators at all levels of canal should get the sufficient quantity of water when needed

23. References
Dr. K. R. Arora (Reprint 2013) Irrigation, Water Power and Water Resource Engineering, Standard Publishers Distributers, Delhi
Internet content

24. Thank you