2. Irrigation engineering
Necessity of irrigation
Scope of irrigation engineering
Benefits of irrigation engineering
Ill-effect of irrigation
Irrigation development in india
Types of irrigation system
Soil-water plant relationship
Classification of soil water
Soil-moisture content
Depth of soil water available to plants
3.
4. IRRIGATION:-Irrigation is defined as the process of artificially
supplying water to soil for raising crops.
IRRIGATION ENGINEERING:- It is the science dealing
with planning, designing, construction, operation and maintenance
of various irrigation works
5. Inadequate rainfall
Non-uniform rainfall
Growing number of crops during year
Growing perennial crops
Growing superior crops
Increasing the yield of crops
Insurance against crops
7. It involves the development of source of water for irrigation
and arrangement for the conveyance of water from the source
right up to agricultural fields.
a) Storage ,diversion or lifting of water.
b) Conveyance of water to the agricultural fields.
c) Application of water to agricultural fields.
d) Drainage and reliving water – logging.
e) Development of hydropower.
8. It involves the timely and systematic application of irrigation
water to the agricultural fields. It deals with following points:
1) Proper leveling and shaping of the agricultural fields.
2) Soil investigation and classification of the agriculural land.
3) Provision of field channel.
4) Distribution of water uniformly and periodically.
5) Capacities of different soil.
6) Conservation of soil against erosion.
7) Choosing proper crop pattern.
8) Reclamation of waste and alkaline ands.
9. It deals with the successful implementation and efficient
management of both the engineering as well as the agricultural
aspects of the project.
Following points are considered in this aspect:-
1) The farmers should be trained and educated.
2) The cultivation should be carried out in a scientific manner with
due control on all the inputs so as to obtain the maximum yield.
3) The distribution of water to the farmers should be managed
properly.
4) The agricultural land holding of the small farmers should be
consolidated to increase the efficiency of irrigation.
5) Suitable measures are to be adopted to eliminate the ill effect of
irrigation.
10. 1) Increase in crop yield
2) Protection from famine
3) Cultivation of crash crops
4) Elimination of mixed cropping
5) Increase in the wealth of country
6) Increase in prosperity of people
7) Generation of hydro-electric power
8) Domestic and industrial water suplly
9) Inland navigation
10) Communication facility
11) Canal plantation
12) Increase in ground water storage
13) Overall development of the country
14) Aid in civilization
11. It is due to the excess irrigation and unscientific use of
irrigation water may give rise to the ill-effects. some of the
common ill-effect of irrigation are:
1) Water logging
2) Mosquitoes nuisance
3) Damp climate
4) Pollution of ground water
12. Classification based on availability of water
Irrigation
system
Flow
irrigation
Lift
irrigation
Perennial
irrigation
As per
source
Inundation
irrigation
Well
irrigation
Lift canal
irrigation
Direct
irrigation
Storage
irrigation
Combined
irrigation
13. The flow irrigation system can be further classified based on
duration into two classes:
1) Perennial irrigation system
2) Inundation irrigation system
PERENNIAL IRRIGATION SYSTEM:-
In this system water is supplied as per the crop
requirements at regular intervals, through the crop period.
INUNDATION IRRIGATION SYSTEM:-
In this system large quantity of water flowing in a
river during flood is allowed to flood or inundated the land
to be cultivated.
19. The water added to a soil mass during irrigation ,is held in the
pores of the soil mass, which is termed as soil water. It is
classified as following:-
1) Gravitational water
2) Capillary water
3) Hygroscopic water
20.
21. SOIL MOISTURE CONTENTT:-The amount of water present in soil is
termed as soil moisture content.
SATURATION CAPACITY:-It is the amount of water required to fill all
the pore spaces between soil particles by replacing all air held in pore
spaces.
FIELD CAPACITY:-The field capacity is the moisture content of the soil
after free drainage has removed most of the gravity water.
PERMANENT WILTING POINT:-Permanent wilting point or the
wilting coefficient is that water content at which plants can no longer
extract sufficient water from the soil for its growth.
22. TEMPORARY WILTING:- Temporary Wilting of plants usually occurs
on a hot day, but the plants recover - from wilting in the cooler portion of
the day or during the night without any addition of water to the soil. Thus,
temporary wilting of plants may occur even without much reduction in the
soil moisture content.
ULTIMATE WILTING:-Ultimate wilting of plants Occurs when they
become completely wilted and dead after ultimate wilting has occurred, the
plants do not recover from wilting even after the addition of water to the
soil.
The water content at which ultimate wilting occurs is termed
as ultimate wilting point.
MOISTURE EUIVALENT:- Moisture equivalent is Defined as the
percentage of moisture retained in an initially saturated sample of soil 10
mm thick after being subjected to a centrifugal force of 1000 times gravity
for a period of 30 minutes.
23. AVAILABLE MOISTURE:- The difference in Moisture content of soil
between the field capacity and the permanent wilting point is called the
available moisture.
READILY AVAILABLE MOISTURE :-It is that portion of the Available
moisture that is most easily extracted by plants. It is approximately 75% of
the available moisture.
SOIL MOISTURE TENSION:-The force per unit area that Must be
exerted in order to extract water from the soil is known as soil moisture
tension.
24.
25. In irrigation, it is essential to know the amount of water
needed by crops.
This determines the quantity of water to be added by
irrigation and rainfall and helps in day to day management
of irrigation systems.
26. DUTY:-
Duty represents the irrigating capacity of a unit water. It relation
between the area of a crop irrigated and the quantity of irrigation water
required during crop growth.
For example:
If 5 cumec of water is required for a crop sown in an area of 5000
hectares, The duty will be 5000/5=1000 hectares/cumec.
DELTA:-
It is total depth of water required for a crop during the entire
period the crop is in the field and is denoted by Δ. The unit of delta is days.
27. There are four types of duty:
1) GROSS DUTY:-It is the duty of water measured at The head of main
canal.
2) NOMINAL DUTY:-It is the duty sanctioned as per Schedule of an
irrigation department.
3) ECONOMIC WATER DUTY:-It is the duty of water Which results in
the maximum crop yield.
4) DESIGNATED DUTY:- It is the duty of water assumed in an irrigation
project for designing capacities of the channel.
28. Let,
D=duty in hectares
∆ = total depth of water supplied in meters
B = base period in days
1) If we take a field of area D hectares, water supplied to the field
corresponding to the water depth ∆ meters will be,
= D x ∆ hectares – meters
=D x ∆ x 104 cubic meters
2) For the same field of area D hectares , water is supplied at the rate of 1
cumec for the entire base period of B days , then the total quantity of
water supplied to the field,
=1 x b x 24 x 60 x 60 cubic meter
=8.64 x 104 B cubic meter
D = 8.64 B/ D meters
29. CROP PERIOD:-It is the time in days, that a crop takes from The instant
of its sowing to that of its harvesting.
BASE PERIOD:- The base period is the relation between he First
watering and the last watering supplied to the land.
PALEO:- It is defined as the first watering before sowing the Crop.
GROSS COMMAND AREA(G.C.A):-It is defined as the total Area lying
between drainage boundaries which can be commanded or irrigated by a
canal.
30. CUTURABLE COMMAND AREA(C.C.A):- It is that portion of G.C.A
which is cultivable or cultivable.
CROP RATIO:- It is defined as the ratio of the land irrigated During the
two main crop season rabi and kharif.
TIME FACTOR:- It is the ratio of number of days the canal has actually
run to the number of days of irrigation Period.
CAPACITY FACTOR:- It is the ratio of mean supply to the Full supply
of a canal.
31. 1) Method of irrigation
2) System of irrigation
3) Method of cultivation
4) Type of crop
5) Base period of crop
6) Climatic condition
7) Quality of water
8) Canal condition
9) Type of soil and sub soil
10) Time of irrigation
32. Composed of two sub processes:-
◦ Evaporation occurs on surfaces of open water or from vegetation and
ground surfaces.
◦ Transpiration is the removal of water from the soil by plant roots,
transported through the plant into the leaves and evaporated from the
leaf’s stomata.
Typically combined in mass balance equations because the components are
difficult to partition.
Evapotranspiration
Evaporation
Transpiration
Open
Water Soil Vegetation
Surfaces
Plants
33. Potential ET (PET) is the amount of evaporation that will occur if an
unlimited amount of water is available.
Actual ET (AET) is the actual amount of evaporation that occurs when
water is limited. For large areas can use a mass balance approach to
calculate (Eq. 4.5).
34. Transpiration is the loss of water in the
form of vapor from plants
Factors that affect transpiration rates
Type of plant
Wind
Plant Available Water: the portion of
water in a soil that can readily be
absorbed by plant roots. Amount of
water released between field capacity
(amount of water remaining in the soil
after gravitation flow has stopped) and
wilting point (amount of water in the
soil at 15 bars of suction).
35. Phase change of water from a liquid to a gas
o Rate of evaporation is driven by the vapor pressure deficit. Function of:
1. The ability of air to hold water based on air temperature and relative
humidity.
1. The energy in the water largely based on temperature.
o Net evaporation ceases when the air has reached the saturation vapor
pressure.
36. There are two method for the measurement :
DIRECT MEASUREMENT METHOD
1. Tank and lysimeter method
2. Field experiment method
3. Soil moisture study
4. Integration method
5. Inflow and outflow studies
USE OF EMPIRICAL FORMULA
1. Penman method
2. Jensen –Haise method
3. Blanley Criddle method
4. Hargreaves method
5. Thornthwait method
37. ET R G
K
BP
e e
r
n
z z
a
0
1
0
1
622
( )[(
*
)( ) (
*
)(. )
( )
]
•More reliable for any length period daily, monthly, or seasonal.
•If adequate data available.
38. AET0 = The evapotranspiration for grass
reference crop
= heat of vaporization
Rn = net radiation
G = soil heat flux
= slope of the vapor pressure curve
= psychrometric constant
= density of air
BP = mean barometric pressure
e0
z = average saturated vapor pressure
ez = actual vapor pressure
*
= (1+rc/ra)
rc = surface resistance to vapor transport
ra = aerodynamic resistance to sensible heat and
vapor transport
K1 = the dimension coefficient
39.
40. These irrigation efficiencies are brought about by the desire not to waste
irrigation water, no matter how cheap or abundant it is.
The objective of irrigation efficiency concept is to determine whether
improvements can be made in both the irrigation system and the
management of the operation programmes, which will lead to an efficient
irrigation water use.
41. APPLICATION EFFICIENCY
E
Water in root zone after irrigation
Total volume of water applied
a
Total vol of water applied Vol of Tailwater Vol of deep percolation
Total water applied
. ( . . )
Ea is inadequate in describing the overall quantity of water since it does not
indicate the actual uniformity of irrigation, the amount of deep percolation or
the magnitude of under-irrigation. See diagrams in text.
42. Water Conveyance Efficiency
E
Water delivered to the Farm W
Water of water diverted from a stream reservoir or well W
c
d
s
( )
, ( )
Farm
Water lost by evap
And seepage
Wd
Ws
43. E
Volume of water in the root zone after irrigation
Volume of water needed in root zone to avoid total water moisture depletion
s
=WS/WN X 100
44. Irrigation projects are planned, executed, owned, and operated by state
governments. Irrigation projects are financed by state governments out of
their own resources, market borrowing and loans and grants made available
by the central governments. the beneficiaries in commanded areas derive
considerable benefits from the project. It is , therefore, imperative that the
beneficiaries pay for it. The fixation of such charges is known as
assessment of irrigation water.
45. 1) Assessment on area basis or crop rate basis
2) Volumetric assessment
3) Assessment on seasonal basis
4) Composite rate basis
5) Permanent assessment
