Irrigation Engineering for B.tech Civil

1. INTRODUCTION TO IRRIGATION
ENGINEERING

7. INTRODUCTION
 At present the country’s food grain availability: 523 grams
per capita per day
 China : 980 grams and USA :2850 grams
 Projected population in 2050 AD: 164 crores
 the annual requirement would be around 430 million tonnes.
 Present productivity : 2.5 tonnes/hectare and les than 0.5
tonnes/hectare for rainfed lands.
 Assuming that these levels can go up to 3.5 and 1.0 T/hr
respectively by 2050 AD, it is imperative that the irrigation
potential of at least 130 million hectare is created for food crop
alone and 160 million hectare for all crops
Are land and water resources going to increase?
 cautious decisions on optimizing the available resources for
maximum benefit.
 urgent need to implement and plan irrigation strategies
 But sustainable development in Irrigation !

8. FUTURE DIRECTIONS
“Are we capable of producing the
required amount of food grain for the
country?
 Spreading the network of irrigation system further
 Urgent need on research- for better seeds, better water
management and distribution practices, low cost fertilizer etc
 Evaporation control
 Reduction in losses during conveyance
 Recycling of water,
 Inter basin transfer,
 Desalination of sea-water in coastal areas,
 Rainfall by cloud seeding,
 Improved technology,

10. BENEFITS OF IRRIGATION
………….. COMPARED TO COMPLETE DEPENDENCE ON RAINFALL
1. Increase in crop yield:
 by providing the right amount of water at the right time
2. Protection from famine:
 drought risk
3. Cultivation of superior crops:
 yield high return.
 in rain-fed areas is not possible because even with the slight
unavailability of timely water, these crops would die
4. Elimination of mixed cropping:
 in rain-fed areas, farmers have a tendency to cultivate
more than one type of crop in the same field such that even
if one dies without the required amount of water, at least he
would get the yield of the other. However, this reduces the
overall production of the field.

11. 5. Economic development:
6. Hydro power generation:
 using bulb-turbines on canal drops ( like Ganga canal,
Sarada canal, Yamuna canal)
7. Domestic and industrial water supply:
8. Improved in the Ground Water storage

13. SOME IMPORTANT TERMS
Culturable Command Area (CCA):
 The gross command area contains unfertile barren land, alkaline soil, local
ponds, villages and other areas as habitation. These areas are called
unculturable areas. The remaining area on which crops can be grown
satisfactorily is known as cultivable command area (CCA).
Gross command area (GCA): The total area lying between drainage
boundaries which can be commanded or irrigated by a canal system.
G.C.A = C.C.A + UNCULTURABLE AREA
Outlet: This is a small structure which admits water from the distributing
channel to a water course of field channel. Thus an outlet is a sort of head
regulator for the field channel delivering water to the irrigation fields.
Water logged area: An agricultural land is said to be waterlogged when its
productivity
 or fertility is affected by high water table.

14. FOUR SUBSYSTEMS OF IRRIGATION
 (i) The water supply subsystem
 diversion from rivers or surface ponds or pumped flow of
ground water.
 (ii) The water delivery subsystem
 canals, branches, and hydraulic structures on these.
 (iii) The water use subsystems,
 (a) surface irrigation, (b) subsurface irrigation, (c) sprinkler
irrigation, and (d) trickle irrigation.
 (iv) The water removal system i.e., the drainage
system.

15. MANAGEMENT OF WATER FOR IRRIGATION
Water resources engineer to decide the following:
 How much water is available at a point of a surface water
source, like a river (based on hydrological studies)
 How much ground water is available for utilization in
irrigation system without adversely lowering the ground
water table?
 For the surface water source, is there a need for
construction of a reservoir for storing the monsoon runoff to
be used in the lean seasons?
 What kind of diversion system can be constructed across
the river for diverting part of the river flow into a system of
canal network for irrigating the fields?

16.  How efficient a canal network system may be designed
such that there is minimum loss of water and maximum
agricultural production?
 How can excess water of an irrigated agricultural fields be
removed which would otherwise cause water logging of the
fields?

17. COMPONENTS ESSENTIAL FOR PROPER
MANAGEMENT OF WATER IN AN IRRIGATION
SYSTEM.
1. Watershed development:
 Movement of water over ground has to be delayed.
 recharges the ground water, which in turn replenishes the
water inflow to the reservoir even during the lean season.
 Small check dams
 Aforestation
 Regrassing and grass land cultivation process,
 Gulley plugging,
 Nallah bunding, contour bunding
2. Water management at head works:
 surface water reservoirs
 reduce
 Evaporation from the water surface
 Seepage from the base
 Reduction of storage capacity due to sedimentation

18. 3. Water management in conveyance system:
 In India the water loss due to evaporation, seepage and
mismanagement in the conveyance channels (for canals and its
distributaries) is exceptionally high-nearly 60%.
 Some countries like Israel have reduced this loss
tremendously by taking several measures like lining etc.
 Canal Automation
Scheduling of irrigation water:
 knowledge is based mostly on intuition and traditional wisdom
 Modern scientific study on crop growth has shown that a
correlation can be established between the climatic
parameters, crop water requirement and the moisture stored
in the soil
 application of irrigation should be such that the available
water in the soil above the permanent wilting point is
fully utilized

19. 4. On farm water management:
 is tackled by agricultural engineers,
 Head reach farmers excessively fetch
 Education of farmers
 Formation of WUAs
Choice of irrigation method:
 It is important to select the right kind of irrigation method to suit
the crop and soil.
Choice of cropping pattern:
 Scientific choice on the basis of water availability, soil type, and
regional agro-climate conditions.
 Crop varieties which give equivalent yield with less water
requirement and take less time to mature should be popularized.

20. 5. Development of land drainage:
 water logging and excess salt concentration in soils.
 Adequate drainage measures like surface and subsurface
drainage systems, vertical drainage, bio-drainage etc.
 an integral part of the irrigation system.

21. METHODS OF IRRIGATION

22. WATER USE SUBSYSTEMS
…………..SELF STUDY
Irrigation water can be applied to croplands by…..
(i) Surface irrigation
(a) Uncontrolled (or wild or free) flooding method,
(b) Border strip method,
(c) Check method,
(d) Basin method, and
(e) Furrow method.
(ii) Subsurface irrigation
(iii) Sprinkler irrigation
(iv) Trickle irrigation

23. CLASSIFICATION OF IRRIGATION SCHEMES
…BASED UPON CCA
1) Major irrigation projects:
 culturable command area(CCA) > 10,000 ha but more
than 2,000 ha utilize mostly surface water resources.
2) Medium irrigation projects:
 CCA < 10,000 ha. But more than 2,000 ha utilizes mostly
surface water resources.
3) Minor irrigation projects:
 CCA <= 2,000 ha. utilizes both ground water and local
surface water resources.

24. CLASSIFICATION OF IRRIGATION SCHEMES
…..BASED ON WATER CONVEYANCE SYSTEM
1. Flow irrigation system:
 where the irrigation water is conveyed under gravity
􀂃 Direct irrigation:
 irrigation water is obtained directly from the river, without any
intermediate storage.
 Constructing a weir or a barrage across a river to raise the level
of the river water and thus divert some portion of the river flow
through an adjacent canal,
 Practiced on perennial river in plains ( North India)
􀂃 Reservoir/tank/storage irrigation:
 where storage has been created by construction an obstruction
across the river, like a dam.
 Non Perennial river in Ghats/ platue

25. 2. Lift irrigation system:
 irrigation water is available at a level lower than that of
the land to be irrigated
 and hence the water is lifted up by pumps or by other
mechanical devices for lifting water and conveyed to the
agricultural land through channels flowing under gravity

33. SELF STUDY………….
HISTORY OF IRRIGATION DEVELOPMENT
Source: Ministry of Water Resources, Government of India web-site:
http://wrmin.nic.in/
Sources of water
Irrigation methods

34. WATER REQUIREMENT OF CROPS AND
SOIL-WATER RELATIONSHIP
The irrigation engineer should be acquainted with :
• the type of soil,
• soil moisture,
• quality of irrigation water,
•frequency of irrigation

35. FACTORS AFFECTING THE WATER
REQUIREMENT
(a) Water Table
(b) Climate :
temperature, humidity, wind velocity etc.
(c) Ground Slope
for steeper slopes : water requirement will be
more.
(d) Intensity of Irrigation
( = particular crop area % in CCA)
(e) Type of Soil
(f) Method of Application of water
 surface method: more water
 Sprinkler , Drip Vs flood
(g) Method of Ploughing
 In deep ploughing (by tractor) less water is required(lesser
evaporation)

37. FEW MORE TERMINOLOGIES
Crop Seasons
(a) Kharif Season (June to October)
The major kharif crops are—Rice. Maize, Jute,
Groundnut, etc.
(b) Rabi Season (October to March.)
The major Rabi crops are—wheat, Gram, Mustard,
Rapeseed, Linseed, Pulses. Onion, etc.
 Several crops are not included in Kharif and Rabi as
they require more time and they cover both the main
seasons.
(i) Cotton—eight month's crop.
(ii) Sugarcane—perennial crop.

38.  Crop Period
period from the time of sowing a crop to the time or
harvesting in. (period in which the crop remains in the
field)
 Base (Base period) B days
period from the first to the last watering of the crop
just before its maturity.

39.  Delta cm
 Each crop requires certain amount of water per hectare for its
maturity.
 If the total amount of water supplied to the crop (from first to last
watering) is stored on the land without any loss, then there will be
a thick layer of water standing on that land.

40.  Duty (D) hectares/cumec.
 “number of hectares that can be irrigated by constant supply
of water at the rate of one cumec throughout the base
period”
 Represents irrigation capacity of unit water
 The duty of water is not constant, but it varies with various factors
like soil condition, method of ploughing, method of application of
water, etc.

41.  it is necessary to state the following along with the duty
(a) the base period, and
(b) the place of measurement of duty
 duty varies with the place of its measurement!!
Duty reduces as u go
u/s

42. RELATIONSHIP BETWEEN DUTY & DELTA
Example
Find the delta for a crop if the duty for a base period of 110
days is 1400 hectares/cumec

43.  Ans: 68 cm
Example.2.
A crop requires a total depth of 9.2 cm of water for
a base period of 120 days. Find the duty of water.
……1130 Ha/ cumecs

44. FACTORS AFFECTING DUTY

45. METHODS OF IMPROVING DUTY
 1. Suitable method of applying water.
2. Properly ploughing and levelling
3. Frequent cultivation
4. Canal lining
5. Parallel canals. :
F.S.L will be lowered and the losses will reduce
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.

46. 10. rotation of crops
11. volumetric method of assessment
12. Farmer’s training
13. Research stations
14. Canal administrative staff should be efficient,
responsible and honest.

47. FEW MORE TERMINOLOGIES……
1. Kor depth and Kor Period
 Crops require maximum water during first watering
after the crops have grown few centimeters.
 During the subsequent watering the quantity of water
needed gradually
 The first watering is known as kor watering, and
 the depth applied is known as kor depth.
 The portion or the base period in which kor watering is
needed is known as kor period.
 while designing the capacity or a channel, kor water
must be taken into account since discharge in the canal
has to be maximum during this time.

48. 2. Time Factor
 ―ratio of the number of days the canal has actually run to the
number of days of irrigation period‖
3. Capacity Factor
 This is the ratio of the mean supply (discharge) to the full supply of
a canal.
4. Paleo
 first watering before sowing

50. Which value to take for
design?

51.  Problem
Find out the capacity of a reservoir from the following
data. The culturable command area is 8000O hectares.
Assume the canal and reservoir losses as 5% and 10%
respectively.

52. Calculate the delta values & CCA for each crop

53. Problem
Determine the discharge rate of the pump required
to irrigate an area of 50 ha in a region having no
effective rainfall and the peak ET rate of 6
mm/day.
Assume the pump will be operated 12 h per day (24
h), and the field irrigation efficiency is 80%.

60. HOME WORK

61. SOIL–WATER RELATIONS
 Irrigation practices are greatly influenced by the soil
characteristics.

62. BASICS OF SOIL
―heterogeneous multi-phasic porous system, which, in
its general form, contains three natural phasic
components:
 (1) the solid phase of the soil matrix (formed by mineral
particles and solid organic materials),
 (2) the liquid phase, which is often represented by water
 (3) the gaseous phase, which contains air and other gases.‖
Agricultural Soil
 presence of nutrient and water, can facilitate plant growth.

63. SOIL PARTICLE
 must pass through a 2-mm sieve to be called soil
particle.
 either organic or inorganic.
Composition:
 aggregated by organic matter, mineral oxides,
and charged clay particles.
 The gaps between the particles link together into
a meandering network of pores of various sizes.
 Through these pore spaces, the soil exchanges
water and air with the environment.
 The movement of air and water also allows for
 heat and nutrient to flow.

64.  (a) Minerals
 (b) Water
 (c) Air
 (d) Organic matter: retaining water, retaining
nutrients, reducing the saturated hydraulic conductivity of
sandy soils, and acting as a binding agent between soil
particles to promote the formation of soil aggregates,
buffering pH, food source for soil microbes and helps to
maintain an adequate and healthy population of soil
microbes. Finally, it acts or serves as a source of plant
nutrients.

65. SOILS
―mainly consists of finely divided organic matter and
minerals‖
Functions:
 holds the plants, stores water ,supplies nutrients and
helps in aeration.
Classification:
 on the basis of size (gravel, sand, silt, clay, etc.),
 geological process of formation
 (i) Residual soils: Disintegration of natural rocks due to
the action of air, moisture, frost, and vegetation
 (ii) Alluvial soils: Sediment material deposited in bodies
of water, deltas, and along the banks of the overflowing
streams
 (iii) Aeolian soils: deposited by wind action.
 (iv) Glacial soils: products of glacial erosion.
 (v) Colluvial soils: deposition at foothills due to rain
wash.
 (vi) Volcanic soil: These are formed due to volcanic
eruptions and are commonly called as volcanic wash.

66. SOILS COMMONLY FOUND IN INDIA
(i) Alluvial Soils:
 include the deltaic alluvium, calcareous alluvial
soils, coastal alluvium, and coastal sands.
 largest and most important soil group of India.
 By rivers of the Indus, the Ganges, and the
Brahmaputra systems.
 These soils vary from drift sand to loams and
from fine silts to stiff clays.
 Very fertile and, hence, large irrigation schemes
 Strong foundation problem.

67. (ii) Black Soils:
 Vary in depth from a thin layer to a thick
stratum.
 Deccan trap black cotton soil. It is common in
Maharashtra, western parts of MP, parts of AP,
parts of Gujarat, and some parts of TN
 vary from clay to loam and are also called heavy
soils.
 Many black soil areas have a high degree of
fertility but some, especially in the uplands, are
rather poor.
 rice and sugarcane, cotton, banana etc.
 Drainage is poor

68. (iii) Red Soils:
 These are crystalline soils formed due to meteoric
weathering of the ancient crystalline rocks.
 TN, Karnataka, Goa, south-eastern Maharashtra, eastern
Andhra Pradesh, Madhya Pradesh, Orissa, Bihar, and some
districts of WB and UP.
 Many of the so-called red soils of south India are not red.
(iv) Lateritic Soils:
 Laterite rock is composed of a mixture of the hydrated oxides
of aluminium and iron with small amounts of manganese
oxides.
(v) Desert Soils:
From agricultural considerations, the following soil
characteristics are of particular significance.
 (i) Physical properties of soil,
 (ii) Chemical properties of soil

69. PHYSICAL PROPERTIES OF SOIL
Permeability :w.r.t. air, water, and roots
 depends on the porosity and the distribution of pore
spaces which, in turn, are decided by the texture and
structure
1. Soil Texture
 determined by the size of soil particles.
 ( sand/silt/clay/loam etc.)
 affects the flow of water, aeration of soil, and the
rate of chemical transformation
 determines the water holding capacity of the soil.
of the soil.

70. 2. Soil Structure
 Volume of space (i.e., the pores space) between the
soil particles (in irrigated soils 35 to 55%)
 Porosity (n)
 Soils of uniform particle size have large spaces
between the particles, whereas soils of varying
particle sizes are closely packed and the space
between the particles is less.
 Fine-textured soils offer a favorable soil structure
 Granules are broken due to excessive irrigation,
Such working affects the soil structure adversely.
 Adoption of ploughing, fertilizers , crop rotation
to maintain soil structure.

71. Depth of Soil
 for storing sufficient amount water and
 providing space for root penetration
 Shallow soils require more frequent irrigations
and cause excessive deep percolation losses when
shallow soils overlie a aquifer
 Deep soils
 permit the plant roots to penetrate deeper, and
provide for large storage of irrigation water.

72. CHEMICAL PROPERTIES OF SOIL
 For satisfactory crop yield, soils must have sufficient plant
nutrients, such as nitrogen, carbon, hydrogen, iron, oxygen,
potassium, phosphorus, sulphur, magnesium, and so on.
 Saline soils: excess (greater than 0.15 to 0.20 per cent)
 May delay or prevent crop germination ,reduce the rate of plant
growth because of the high osmotic pressures
 Osmotic pressures adversely affect the ability of the plant to
absorb water.
 Alkaline/sodic soils: excess of exchangeable sodium
(more than 15 per cent or pH greater than 8.5)
 tend to have inferior soil structure due to swelling of the soil
particles.
 This changes the permeability of the soil. Bacterial environment
is also an important
 Reclaimation of saline/alkaline soils requires good drainage
system or percolation.

73. ROOT-ZONE SOIL WATER
 ROOT ZONE
“the volume of soil or fractured rock occupied or occupiable
by roots from which plants can extract water ―
 Water logging and deficient water in the root-zone soil
retard crop growth
Functions of water in plant’s growth:
(i) Germination of seeds,
(ii) All chemical reactions,
(iii) All biological processes,
(iv) Absorption of plant nutrients through their aqueous
solution,
(v) Temperature control,
(vi) Tillage operations, and
(vii) Washing out or dilution of salts.

75. Soil water :
 (i) Gravity (or gravitational or free) water,
 (ii) Capillary water, and
 (iii) Hygroscopic water.
 When an oven-dry soil sample is exposed to
atmosphere, it takes up some hygroscopic
moisture
 If more water is made available, it can be
retained as capillary moisture due to surface
tension (intermolecular forces).
 Any water, in excess of maximum capillary
moisture(FC), flows down freely and is the
gravitational (or gravity) water.

77. • PET @ FC
&
AET @
FC> W >+ PWP

78. FIELD CAPACITY
 ―The water remaining in the soil after the removal of
gravitational water‖
 “The moisture content of a deep, permeable, and well-drained soil
several days after a thorough wetting.‖
Wfc = (Ww/Ws).

80. IRRIGATION WATER NEED

81. FIELD IRRIGATION REQUIREMENT(FIR)
 Plants growth stages:
 Vegetative, flowering( max consumptive use), and
fruiting.
 Note: harvested during different stages of crop
growth.
 For example, leafy vegetables are harvested during
the vegetative stage and flowers are harvested during
the flowering stage. Most crops (such as potatoes,
rice, corn, beans, bananas, etc.) are harvested during
the fruiting stage.
 Irrigation efficiency is the ratio of irrigation
water consumed by crops of an irrigated field to
the water diverted from the source of supply.

83. POTENTIAL EVAPOTRANSPIRATION(DET)
1) Method1: correlating with pan evaporation
K is the crop factor for that period
Assumption:
climatic conditions affecting crop water loss (Det) and evaporation from a
free surface of water (Ep) are the same.,
2) Method 2 : estimations based on various
climatic parameters.

85. Example:
 Using the data given for a given crop, determine
the field irrigation requirement for each month
assuming irrigation efficiency to be 60 per cent.

89. FREQUENCY OF IRRIGATION
primarily depends on:
(i) the water needs of the crop,
(ii) the availability of water, and
(iii) the capacity of the root-zone soil to store water.
 Shallow-rooted crops generally require more
frequent irrigation than deep-rooted crops.
 A moderate quantity of soil moisture is beneficial.
Both excessive and deficient amount of soil
moisture retard the crop growth
 .

92. DETERMINING FREQUENCY OF IRRIGATION
 the average moisture content is close to the
optimum and at each irrigation the soil moisture
content is brought to the field capacity.
 Alternatively, satisfy the daily consumptive use
requirement which varies with stage of growth.
 Thus, frequency of irrigation is calculated by
dividing the amount of soil moisture which may
be depleted (i.e., allowable depletion below field
capacity and well above permanent wilting point)
within the root-zone soil by the rate of
consumptive use. Thus,

93.  The depth of watering at each irrigation to bring
the moisture content w to the field capacity wfc in
a soil of depth d can be determined from the
following relation

94. EXAMPLE
 During a particular stage of the growth of a crop,
consumptive use of water is 2.8 mm/day.
 Determine the interval in days between
irrigations, and depth of water to be applied
when the amount of water available in the soil is:
(i) 25%, (ii) 50% (iii) 75%, and (iv) 0% of the
maximum depth of available water in the root
zone which is 80 mm.
 Assume irrigation efficiency to be 65%.

96. IRRIGATION EFFICIENCIES
1) Water conveyance efficiency ηc =
water delivered into fields from outlet point of the channel /
water entering into channel at its starting point
2) Water application efficiency ηa =
Quantity of water stored in root zone / water actually delivered
to fields
3)Water storage efficiency ηs =
Water stored in the root zone during irrigation / water needed in
the root zone prior to irrigation( wfc-w)
4) Water use efficiency ηu =
Water beneficially used including leaching water to the water
delivered.

97.  5) Uniformity coefficient(water distribution
efficiency)
ηd = (1-d/D)
 d= average of absolute value of deviations from the mean
 D = mean depth of water stored during irrigation

98. DELIVERY OF WATER TO FARMS
problem of its equitable distribution amongst the farms???
Two possible alternatives
(i) Restrict the canal irrigation to such limited areas as can be
fully supported with the lowest available supply.
 does not lead to the total utilization of available water.
 Agricultural production and protection against famine would also not
be optimum.
 The production would be maximum per unit of land covered though not per unit of
water available.
 not require a precise or sophisticated method for the distribution of
irrigation water.
 can be either continuous or demand-based,
 A continuous delivery system can be effectively used for large farms and
continuously terraced rice fields. Though ideal, a demand-based delivery system is
not practical on large irrigation systems.

99.  (ii) Extend irrigation to a much larger area than
could be supported by the lowest
 available supply. This creates perpetual scarcity
of irrigation water but ensures
 that a comparatively less quantity of water
remains unutilised. Agricultural

100. THANK YOU………

101. WATER POLICY
 set of guidelines and directives to the State for
harnessing water resources - to cater the sectoral
(agriculture, industrial and domestic) - need in
equitable way that leads to sustainable
development.

102. A POLICY STATEMENT DEFINES-
 – Ownership and related right with regard to its
use
 – Incentive and penalty awards towards
conservation and deterioration of water resources
 – Water allocation priorities to sectors
 – Water conservation
 – Institutional structure for executing planning
and implementation

103. WATER IN INDIAN CONSTITUTION
 – ―Water‖ in entry 56 of union list and entry 17 of
state list.
 – Article 246 and Art. 262, empowers parliament
to make law regarding development and
management of inter-state rivers.
 – ― Art 262, specifies that parliament may by law
provide that neither the supreme court or any
other court shall exercise jurisdiction with
respect of interstate river disputes .
Interpretation- arbitration

104. NATIONAL WATER POLICY IN INDIA
Needs:
 Availability of water is highly uneven in both space and time
 Precipitation is confined to only few months in a year
 Rainfall Varies spatially – eg. In India: from 100 mm in the western
parts of Rajasthan to over 10000 mm at Cherrapunji in Meghalaya
 On an average, floods affect around 7.5 milli. Hectare/ year
 Planning and implementation of water resources projects involve a
number of socio-economic aspects and issues

 Example: environmental sustainability, rehabilitation of project-
affectedpeople and livestock
 Common approaches and guidelines are necessary on these matters
 Gross irrigation potential is estimated to have increased from 19.5
million about 95 million hectare by the end of the Year 1999-2000.
 Some other factors like degradation of water quality

105. SALIENT FEATURES
 – Policy promotes use of non-conventional
methods such as traditional water & rooftop
rainwater harvesting
 – Water transfer to water scarce region
 – People’s participation
 – Public Private Partnership
 – Water Resources planning at hydrologic unit
not on political unit
 Directed state to devise its own water policy –in
practice very few state has prepared it so far

106. ALLOCATION PRIORITY
 (national level, may differ at state level)
 1. Drinking Water
 2. Irrigation Hydropower
 3. Ecology
 4. Agro-industries
 5. Non-agricultural industries
 6. Navigation
 Same for all state, except Maharashtra where
water for industrial use is top than irrigation

107. NATIONAL WATER POLICY (2012)
Basic principles
 Access to safe and clean drinking water and
sanitation should be regarded as a right to life
should have a pre-emptive priority over all other
uses.
 Water, over and above the pre-emptive need
should be treated as an economic good so as to
promote its conservation and efficient use

108. STATE WATER POLICY

109. IRRIGATION WATER MANAGEMENT
ASSESSMENT OF CHARGES
 Irrigation projects : huge expenditure for their
construction.
 operation and maintenance
(i) Assessment on area basis,
(ii) Volumetric assessment,
(iii) Assessment based on outlet capacity,
(iv) Permanent assessment, and
(v) Consolidated assessment.

110. 1. Area basis method of assessment,
 water charges are fixed per unit area of land
irrigated for each of the crops grown.
 depend on the cash value of crop, water requirement
of crop, and the time of water demand
 No relevance to actual quantity of water used,
 the farmers (particularly those whose holdings are in the
head reaches of the canal) tend to over irrigate their land.
 uneconomical use of available irrigation water
 depriving the cultivators in the tail
 But , simple and convenient, is generally
 used for almost all irrigation projects in India.

111. 2. Volumetric assessment,
―charges are in proportion to the actual amount of
water‖
 requires installation of water meters at all the
outlets of the irrigation system.
 Alternatively, modular outlets may be provided to
supply a specified discharge of water.
 economical use of irrigation water
 therefore, an ideal method of assessment.
 Drawbacks.
 requires the installation and maintenance of suitable
devices for measurement of water supplied.
 devices require adequate head at the outlet.
 Further, there is a possibility of water theft by cutting
of banks or siphoning over the bank through a flexible hose
pipe. Also, the distribution of charges among the farmers,
whose holdings are served by a common outlet, may be
difficult.
 Because of these drawbacks, this method has not
been adopted extensively in India

112. 3. Based on outlet capacity:
 is a simple method and is workable if the outlets
are rigid or semi-modular and the channel may
run within their modular range.
4 Permanent assessment
 In some regions, artificial irrigation, though not essential,
has been provided to meet the water demand only in
drought years.
 Every farmer of such a region has to pay a fixed amount.
 The farmers have to pay these charges even for the years
for which they do not take any water.
 A farmer has also to pay a tax on the land owned by him
5. Consolidated assessment method,
 both the land revenue and the water charges are
combined.

113. BASICS OF IRRIGATION SCHEDULING
 decision of when and how much water to be applied in a
crop field
Indicators of Irrigation Need Assessment:
 Plant leaf appearance
 Soil moisture status (hand-feel or instrumental)
 Soil-water potential
 Leaf-water potential
 Leaf temperature.
plants themselves may be the best indicator
But the problem is that, the time when the crop shows
such symptom (wilting symptom), the yield reduction may
already have occurred.
Therefore focus on soil moisture

114. WARABANDI
is an integrated management system from source (river
or reservoir) down to the farm gate, i.e., nakka.
primary distribution system water from the source is carried
by the main canal which feeds two or more branch canals (which
operate by rotation) and may not carry the total required supply.
 runs throughout the irrigation season with varying supply.
secondary distribution system consists of a larger number of
distributaries which too run by rotation but carry full supply.
 The distributaries supply water to the watercourse through outlets.
 These watercourses run full supply when the supplying distributary is
running.
tertiary distribution system
 Water is then allocated to various fields (or farms) situated
along the watercourse by a time roster.

116. main objective
 high efficiency of water use by imposing
water scarcity on every user.
 equitable distribution and safeguards the
interest of the farmer whose field is located
at the tail end of the conveyance system.
 joint state-farmer management

117. • water allowance(me/s) for each unit of CCA
(depends on demand and supply)……(not on cropping pattern)
• The carrying capacity of distributaries and watercourses is designed on
the basis of water allowance.
• Whenever distributaries run, they are expected to carry their full
supply.
• The outlets to watercourses are so planned and constructed that all the
watercourses on a distributary withdraw their authorized share of water
simultaneously.
• For the Bhakra project covering Punjab, Haryana, and Rajasthan, the
value of water allowance at the head of the watercourse is 0.017 m3/s
per 100 hectares of CCA

118. • To check the dangers of waterlogging and salinity, no distributary is
allowed to operate all the days during any crop season.
• capacity factor : The ratio of the operating period of a distributary
and the crop period is called the capacity factor of the distributary.
• For the Bhakra project, Kharif o.8 and Rabi 0.72
• means that each distributary would receive its full supply for a
period of about 144 and 129 days, respectively, in a crop season of
180 days.

119. MANAGEMENT OF WARABANDI SYSTEM
1st stage
• The state manages the supply in distributaries and watercourses
which, when running, always carry their full supply discharge.
• reduces their running time and, hence, the conveyance losses
• Generally eight-day periods.
• In a normal year, it is possible to run the distributaries of the
Bhakra project for 18 periods during Kharif and 16 periods during
Rabi.
2nd stage
• responsibility of the cultivators themselves(outlet onwards)
• distribution on seven-day rotation basis with the help of an
agreed roster (or roster of turns) which divides 168 hours of seven
days in the ratio of the holdings.
• Each cultivator’s right to share water in a watercourse is
guaranteed by law and the Canal Act empowers canal officers to
ensure this right for everyone.

120. Roster of Turn
• Whenever a distributary is running, watercourse receives its share of
water at a constant rate round the clock and water distribution
proceeds from head to tail.
• Each cultivator on the watercourse is entitled to receiving the entire
water in a watercourse only on a specific weekday and at a specific time
(during day and/or night).
• There is no provision in this system to compensate a defaulting farmer
who has failed to utilize his turn for any reason.
• bharai (i.e., filling time) Before a farmer receives his share of water,
some time is spent in filling up the empty watercourse between the
point of taking over and the beginning of his holding.
• which is debited to a common pool time of 168 hours and
credited to the account of the concerned farmer.

121. • The supply in the watercourse has to be stopped when the tail-end
farmer is having his turn.
• The water filled in the watercourse during the common pool time
(bharai) can be discharged only into the field of the tail-end farmer and,
hence, normally the total time spent on the filling of the watercourse
should be recovered from him in lieu of this.
• But he does not receive this water at a constant rate.
• Such a supply, beyond a limit, is not efficient from the point of view of
field application.
• The tail-end farmer is, therefore, compensated for it and is allowed a
certain discount on the recovery of the bharai time.
• This value of bharai is termed jharai (i.e., emptying time).
• Obviously, correct determination of jharai time is an unresolved
problem and its present values are favourable to the tail-end farmer.

122. After allowing for bharai and jharai, the flow time (FT) for a unit area
and for an individual farmer are given as follows

125. FARMER’S PARTICIPATION

126. Intensity of Irrigation(ICA)
• Because of the limits on the supply of irrigation water as well as
other factors, it is generally not possible to irrigate all culturable
command area.
• The ratio of the resultant irrigated area to the culturable
command area is termed intensity of irrigation.
• Its value is 62 per cent for the Bhakra project.
• The intensity of irrigation is an index of the actual performance of
the irrigation system.

127. DIFFERENCE BETWEEN CROP WATER
REQUIREMENT AND IRRIGATION
REQUIREMENT