THIRD YEAR DIPLOMA IN CIVIL ENGINEERING SUB- W.R.E

1. CROP WATER REQUIREMENT
Prof.M.B Chougule,
DKTE’S YCP Ichalkaranji
• Crop water requirement is the water required by
the plants for its survival, growth, development and
to produce economic parts.
• This requirement is applied either naturally by
precipitation or artificially by irrigation.

2. Functions of Irrigation Water
• Soil furnishes the following for the plant life:
• 1. To supply water partially or totally for crop need
2. To cool both the soil and the plant
• 3. Provides water for its transpiration.
• 4. Dissolves minerals for its nutrition.
• 5. Provides Oxygen for its metabolism.
• 6. Serves as anchor for its roots.
• 7. To enhance fertilizer application- fertigation
• 8. To Leach Excess Salts
• 9. To improve Groundwater storage
• 10. To Facilitate continuous cropping

3. CROPING SEASONS AND CROPS IN MAHARASHTRA

5. IMPORTANT DEFINATIONS
• 1) Crop period : It is the period in number of days that
crop takes from the instant of its sowing to that of its
harvesting.
• 2) Base period : It is the period in days from first
watering at the time of sowing to the last watering
before harvesting.
• 3) Duty (D): Duty is the area in hectares (ha) irrigated
by one cubic per meter per second of water flowing
continuously for the base period for a particular crop
(Ha/cumec)
• 4) Delta (Δ ): Delta is total depth of water required by a
crop during the entire period of the crop from first to
last watering for complete maturity of the crop.

6. Average duty/tank duty
• It is flow duty calculated at the head (beginning) of
distribution (a type of canal ) or main canal for small
irrigation
• It is always less than duty as it takes all types of
losses in account.
• GROSS DUTY/TANK DUTY:
• Gross duty is the area under different crops
irrigated by one million cubic meters of stored
in tank in one year
• CROP ROTATION:- it has been observed that if
same crop is sowing again and again the yield
gets decreased.

7. .• The main advantage of crop rotation is it helps in
proper use of land resources and it also increases
fertility of soil.
THE USUAL CROP ROTATION IS
• Jawar-gram-fallow
• Wheat-jawar- gram
• Cotton-jawar-groundnut
• Cotton-wheat-gram
• Rice-gram

8. Paleo irrigation:
• Some times it is observed that in the initial stages
before the crop is sown the land is very dry. In such
case the soil is moistened with water so as to help
in sowing. This is known as paleo irrigation.
• CASH CROPS: a cash crop which can not Be
consumed directly by cultivators but has to
encashed in market for processing.
Eg-Tea, cotton, tobacco, sugercane
Intensity of Irrigation (I.I): Percentage of CCA that
is cultivated in a particular season.
Area irrigated per season/total irrigable area

9. Kor depth and kor period
• The distribution of water during the base period is not
uniform, since crops require maximum water during
first watering after the crops have grown a few
centimeters.
• During the subsequent watering the quantity of water
needed by crops gradually decreases and is least when
crop gains maturity.
• The first watering is known as kor watering, and the
depth applied is known as kor depth.
• The portion of the base period in which kor watering
is needed is known as kor period.
• While designing the capacity of a channel, kor water
must be taken into account since discharge in the canal
has to be maximum during this time.

10. SEASONAL DUTY:
• It is the average duty for all crops usually sown
during crop season. In this type of duty all the
losses are taken into consideration and are mainly
used for water planning
• Crop ratio: The ratio of area irrigated in Rabi
season to that irrigated in Kharif season is known
as crop ratio.
• The crop ratio is so selected that the discharge in
the canal during both the seasons may be uniform.

11. Time factor
• The time factor of a canal is the ratio of the number
of days the canal has actually run to the number of
days of irrigation period.
• For example, if the number of days of irrigation
period = 12, and the canal has actually run for 5
days, the time factor will be 5/12.
• (Note: A day has a period of 24 hours (i.e. it
includes the night also).
• Capacity factor: This is the ratio of the mean
supply discharge to the full supply discharge of a
canal.

12. COMMAND AREA:
• It is the area on the downstream side of a project to
which water can reach by gravity
• Gross Commanded Area (GCA): The total area lying
between drainage boundaries which can be
commanded or irrigated by a canal system or water
course is known as gross commanded area.
• Culturable Commanded Area (CCA):
• Gross commanded area contains some unfertile barren
land, local ponds, villages, graveyards etc which are
actually unculturable areas.
• The gross commanded area minus these unculturable
area on which crops can be grown satisfactorily is
known as Culturable Commanded Area.
• CCA = GCA – Unculturable Area

13. Culturable Cultivated Area:
• The area on which crop is grown at a particular
time or crop season.
• Culturable Uncultivated Area:
• The area on which no crop is grown at a particular
time or crop season
• Irrigable command area (ICA):
• It is that area of culturable command area
which can be actually irrigated.

15. .
• 1acre=0.404T hectares
• 1hectare=10⁴ sq. meters
• 1 cusec=0.0283 cumec
• 1 cumec/day=8.64 hectare-meeter

16. Following are the different factors affecting on duty :-
• 1) Method & system of irrigation
• 2) Mode of applying water
• 3) Method of cultivation
• 4) Time & frequency of tilling
• 5) Type of crop
• 6) Base period of crop
• 7) Climatic condition of area
• 8) Quality of water
• 9) Method of assessment
• 10) Canal condition
• 11) Character of soil & sub-soil of the canal
• 12) Character of soil & sub-soil of the irrigation field

17. METHODS OF IMPROVING DUTY
• 1. Suitable method of applying water to the crops should be used.
• 2. The land should be properly ploughed and leveled before
sowing the crop. It should be given good tilth.
• 3. The land should be cultivated frequently, since frequent
cultivation reduces loss of moisture specially when the ground
water is within capillary reach of ground surface.
• 4. The canals should be lined. This reduces seepage and
percolation losses. Also, water can be conveyed quickly, thus
reducing, evaporation losses.
• 5. Parallel canals should be constructed. If there are two canals
running side by side, the F.S.L. will be lowered, and the losses will
thus be reduced.
• 6. The idle length of the canal should be reduced.
• 7. The alignment of the canal either in sandy soil or in fissured rock
should be avoided.
• 8. The canal should be so aligned that the areas to be cultivated
are concentrated along it. W

18. .• 9. The source of supply should be such that it gives good
quality of water.
• 10. The rotation of crops must be practiced.
• 11. Volumetric method of assessment should be used.
• 12. The farmers must be trained in the proper use of water, so
that they apply correct quantity of water at correct timing.
13. The land should be redistributed to the farmers so that
they get only as much land as they are capable of managing
it.
• 14. Research stations should be established in various
localities to study the soil, the seed and conservation of
moisture. The problems concerning the economical use of
water should be studied at research stations.
• 15. The canal administrative staff should be efficient,
responsible and honest. The operation of the canal system
should be such that the farmers both at the head of the canal
as well as at the tail end get water as and when they need it.

19. Consumptive Use of Water (CU)
• Water requirement of crop is the total
quantity of water from the time the crop is
sown to the time it is harvested. This water
requirement may vary from crop to crop, from
soil to soil and period to period.
• Water required to meet the demand of
evapotranspiration and metabolic activities
of the crop togeather is known as
consumptive use (CU) of water

20. Factors Affecting Consumptive Use (CU)
• Evaporation which is dependent on humidity
• Mean monthly temperature
• Monthly precipitation
• Wind velocity in the locality which affects
evaporation
• Soil type and its topography
• Cropping pattern, growth stage and type of crop
• Growing season of the crop
• Method of applying irrigation
• Irrigation water depth
• Day light hours

22. assessment of irrigation water
• Methods of assessment:
• 1) Volumetric assessment
• 2) Assessment on area basis
• 3) Assessment on seasonal basis
• 4) Composite rate
• 5) Permanent assessment

23. 1. Volumetric assessment:
• In this method charges are levied on actual volume of
water supplied
• to the cultivators. This is ideal system under which
cultivators has
• incentive for using water economically. However this
method has no
• practical value induce up till now. This method is
necessary to install
• numerous water meter on irrigation outlets, scattered
all over the
• canal system. It is very costly process and difficult to
maintain also.

24. 2. Assessment on area basis:
• In India this type of assessment is generally
adopted, the charges are levied on the actual
area which is under irrigation. The charges are
• fixed crop wise. This method has a few
disadvantages as the charges
• are levied on area basis and not on the actual
quantity of water used.
• It leads to wasteful use of water. This type of
irrigation encourages intensive irrigation rather
than extensive irrigation.

25. 3. Assessment on seasonal basis:
• In this type of assessment the assessment is based
on the kind of crop grown in that area in crop
season.
4. Composite rate basis:
• In this type of assessment the combined land
revenue and tax are levied on cultivators. It is not
normally in practice.

26. 5. Permanent Assessment or
Betterment Levy.
• In area where canals are provided as
insurance against drought, the farmers are
levied at a fixed rate every year irrespective of
the fact whether or not they use the canal
water. In drought year, the farmers are
allowed to draw canal supplies without paying
charges extra to normal betterment levy.

27. SR.
NO
AREA BASIS VOLUMETRIC BASIS
01 The charges are laid on the
area actually irrigated
The charges are laid on the
measurement of discharge
entering to field.
02 Discharge measuring devices
are not required
Discharge measuring devices are
required.
03 It may lead to excess use and
wastage of water.
As former know the charges are
on actual volume of water use
no such wastage is made.
04 Skilled staff is not required. Qualified skilled staff is required.
05 Initial cost is very less . Cost is high due to installation of
water measuring instruments.
06 Maintenance is not required. Frequent maintenance is

28. .
• Duty varies at varies points of measurement from
head of water course to head of canal. Explain.
• 1.In canal irrigation system, the water flows from head
of water course to head of canal.
• 2. During the passage of water from these irrigation
channels, water is lost due to evaporation and
percolation .
• 3. Duty of water for crop , is the number of hectares of
land which the water can irrigate. Therefore, If the
water requirement of crop is more , less number of
hectares of land it will irrigate
• 4. If water consumed is more , duty will be less. It
becomes clear that duty of water at the head of the
water course wiil be less than the duty of water on the
field . because when water flows from the head of
water course and reaches the field , some water is lost
as transit losses.