IMPORTANT TERMS WHICH ARE USED IN IRRIGATION

2. BasePeriodorBase(B)
 It is the whole period of cultivation from the time
when the irrigation water is first issued for
preparation of the ground for planning the crop, to
it’slastwateringbeforeharvesting
 It is the period in days during which flow is
continuedfor aparticularcrop.

3. Crop period:
 It is the time in days that a crop takes from
the instant of its sowing to that of its
harvesting.

4. Duty(D)
 It is the total area irrigated by a unit discharge running
continuously during the baseperiod and its unit is area/cumec.
 It isirrigating capacity of aunit of water.
 Thus, duty gives the relationship between the volume of water and
areaof the crop
E.g.3cumecsof waterisrequiredfor acropsownin anarea 5100
hectares.

5.  Duty of irrigation water will be 5100/3=1700
hectares /cu-mec,
 the discharge of3 cu-mecs is required
throughout thebaseperiod

6. Delta(∆)
It is total depth of water required by a crop during
the entire period the crop is in the field and is
denotedbysymbol∆

7. R
elation betw
een D
uty( D
) and Delta(∆)
Let D=duty in hectares/cumec
∆ =total depth of water supplied(in m)
B=baseperiod indays.
i) If we take a field of area D hectares, water supplied to the field
corresponding to the water depth ∆ meters will be =∆x Dhec-m
=D X ∆ X 104cubic-meters………..(1)

8. Ii) again the same field of D hectares, one cumec of
water is required to flow during the entire base
period. Hence, water supplied to the field
=(1)x(BX 24X60X 60)m3 …………………(2)

9. Equating (1)and(2)
DX ∆ X 104=BX 24X60X60
OR
∆ =BX 24X60X60/DX 104
= 8.64 B/Dmeters.

10. Gross CommandArea (GCA)
The whole area enclosed between an imaginary boundary line
which can be include in an irrigation project for supplying water to
agriculture land by the network of canal is known as Gross
Command Area.It includes both the culturable and unculturable
areas.

11. Culturable Commanded Area:
The total area within an irrigation
project where the cultivation can be
done and crops can be grown is
known as CCA.
Culturablecommandareacanbeclassified as
1.Culturablecultivated area
2.Culturable uncultivatedarea.

12. 1.Culturablecultivated area
ItistheareawithinCCAwherethecultivatonhasbeen
actuallydoneatpresent.
2.Culturable uncultivatedarea.
ItistheareawithinCCAwherethecultivatonispossible
butitisnotbeingcultivatedatpresentduetosome
reasons.

13. Intensity of irrigation
Intensity of irrigation is defined as the percentage of
culturable commanded area proposed to be irrigated during
either acropseasonor during ayear
Or,
Intensity of irrigation may be defined as a ratio of cultivated
land for a particular crop to the total culturable commmanded
area,it is expressed as a percentage of CCA.

14. Factors affecting duty
 Methods and system ofirrigation
 Modeof applyingwaterto thecrops
 Method ofcultivation
 Time and frequency of tilling
 Typeof thecrop
 Baseperiodof the crop
 Climaticconditionsof the area
 Quality ofwater
 Methodsof assessmentof irrigation method
 Canalconditions

15.  Characterof soilandsubsoilof the canal
 Characterof soilandsubsoilof irrigation
fields

16. Methods o f improving duty
1.Proper Ploughing:
Ploughing Should be done properly and deeply so that the moisture
retaining capacity of the soil is increased.
2.Methods of Supplying Water:
The method of supplying water to the agricultural land should be
decided according to the field and soil conditions,example
Furrow method-for crops sown in rows
Contour method-for hilly areas
Basin method-for orchards
Flooding:for plain lands

17. Methods of improving duty
3.Canal Lining:To reduce percolation loss the canals
should be lined according to site condition
4.Transmission Loss:To reduce transmission loss the
canals should be taken close to the irrigable lands as
far as possible.
5.Crop Rotation:The principle of crop rotation should
be adopted to increase the moisture capacity and
fertility of the soil.
6.Implementation of Tax:The water tax should be
imposed on the basis of volume of water consumption