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TERM PAPER ON
APPLICATION OF WATER METHODS OF IRRIGATION
SUBMITTED TO:
Dr. Praveen Rao,
Professor&Head,
Dept. of Agronomy,
College of Agriculture, Rajendranagar.
SUBMITTED BY:
Pasunoori Prashanth,
PhD Scholar,
I.D.NO. RAD/11-10,
Dept. of Agricultural Extension
Methods of Irrigation
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Scientific irrigation aims at efficient use of irrigation water in conjunction with
other essential inputs to enhance and sustain crop production. The manner in which
irrigation water is applied to the land is commonly referred to as method of irrigation.
Several irrigation methods are adopted towards this end under different circumstances.
Selection of appropriate irrigation method for any given combination of physical and
socioeconomic conditions involves numerous complex and often conflicting
considerations. Since, the economic considerations along with physical conditions and
cropping pattern are necessarily specific to each location; an irrigation system optimal
in a particular region may not be so in another. Applicability of a particular irrigation
method depends on several physical, human and economic factors.
Physical factors: Important physical factors associated with selection of irrigation
method include soils, crops, climate, topography, water quality and availability, depth of
water table, field size, maintenance and repairs.
Human and economic factors: Major factors involved are labour and management
skills, availability and cost, capital and energy costs in relation to expected returns.
Surface irrigation methods
In the surface methods of irrigation, water is applied directly to the soil surface
from a channel located at the upper reach of the field. Water may be distributed to the
crops in border strips, check basins or furrows. Two general requirements of prime
importance to obtain high efficiency in surface methods of irrigation are properly
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constructed water distribution systems to provide adequate control of water to the fields
and proper land preparation to permit uniform distribution of water over the field
Surface irrigation (gravity irrigation) is the most ancient method of irrigation
and this method still holds good for more than 95 per cent of the irrigated area in theworld. It can be defined as the process of introducing a stream of water at the head of a
field and allowing gravity and hydrostatic pressure to spread the flow over the surface
throughout the field. To move forward, the flowing water must have a downward slope
in the direction of flow. This is, generally, provided by running water over a sloping
land surface. The soil surface thus serves the dual role of water conveyance and
distribution. Field area nearest to the water inlet receives the greatest opportunity time
and hence the greatest depth of infiltration, whereas the down field farthest from inlet
receives least. This non uniformity is most pronounced in coarse (sandy) soils, in which
the infiltration rate is so high that much of the water entering the field infiltrates near
the inlet and relatively little water remain for farther reaches of the field. On the other
hand, fine textured soils (clayey) exhibit low infiltrability leading to significant flow of
applied water to the lower sections of field, while higher section (near the inlet) remains
insufficiently watered. The distribution of water is obviously affected by the slope and
length of run.
Water application efficiency is usually higher on fine textured (clayey) soils than
on coarse textured (sandy) soils because of their lower infiltration rates and more water
retention per unit depth within the root zone. However, clayey soils are more prone to
excessive wetness, compaction and impeded aeration. Land levelling and smoothing are
essential operations for successful surface irrigation. On regularly sloping lands, graded
long furrows and borders can significantly reduce levelling cost. Surface systems have
both advantages and disadvantages over others.
Advantages
• Initial capital investment for a surface irrigation system is, usually, lower
than for sprinkler or drip systems
• Surface irrigation systems have relatively low energy requirements in
routine operations
• Certain fruits and vegetables which can be damaged by sprinkling
because of leaf scorch from salt residue of sprinkled water can 'be safely irrigated
by surface systems
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• Surface systems can avoid wind drift and canopy interception losses
common in sprinkler irrigation
• Allows use of machinery for different operations
• Most important advantage of surface irrigation is its mechanical
simplicity and easy adaptation to small land holdings.
Disadvantages
• Costly and time consuming land preparation
• Low application efficiencies due, to wastage of water
• Water table raise and water logging
• Salinisation
1. WILD FLOODING
This is the primitive and least controlled of all the surface irrigation systems.
Water from the ditch is diverted to the upper part of the plot and allowed to spread over
the land in accordance with the natural topography.
After the water leaves the ditches, no attempt is made to control the flow. Hence,
it is called as wild flooding. Distribution of water is highly uneven. Consequently, part
of the area becomes waterlogged, while other part remains dry leading to uneven pattern
of crop growth. This method is applicable to inundation irrigation system or for pastures
or forage crops where water is not limiting or high value crops do not justify adoption
of better methods.
Advantages
Land not require precise land leveling and grading
Water application is quite easy and cheap
Skilled labour is not required
Disadvantages
Flooding is uncontrolled
Uniform wetting of land can not be achieved
Greater amount of water accumulates in lower spots
Excessive loss of water by percolation and run off may occur
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Sensitive crops may get damaged by excess water accumulation in lower parts
of the field.
2. Check basin irrigation
Check basin irrigation is the most common method of irrigation in India and in
many other countries. This is the simplest in principle of all methods of irrigation. There
are many systems in its use, but all involve dividing the field into smaller units so that
each has a nearly level surface. Ridges-are-constructed around the areas forming basins
within which the irrigation water can be controlled. The basins are filled to the desired
depth and the water is retained until it infiltrates into the soil. The depth of water may be
maintained for considerable periods of time by allowing the water to continue to flow
into the basins.
The distinguishing features of various uses of check basin method of irrigation
involve the size and shape of the basins and “whether irrigation is accomplished by
intermittent or continuous" collection of water in the basins. The ridges or bunds may be
temporary for a single irrigation as in the pre-sowing irrigation of seasonal crops. They
may be semi-permanently constructed for the repeated use in the case of paddy fields.
The size of ridge will depend on the depth of water to be impounded as well as on the
stability of the soil when wet.
Water is conveyed to the field by a system of supply channels and lateral field
channels. The supply channel is aligned on the upper side of the area and there is
usually one lateral channel for every two rows of check basins. Water from the laterals
is turned into the beds and is cut off when sufficient water has been administered into
the basin. Water is retained in the basin until it soaks into the soil. The size of the
irrigation stream is not critical as long as it is sufficient to provide coverage of the entire
strip in a relatively short time span required to apply the desired amount of water into
the soil. As the infiltration rate of soil increases, stream size must be increased or the
size of the basins reduced in order to cover the area within a short period of time. A
large size irrigation stream will permit a comparatively larger size of the basin.
The size of check basin may vary from one square metre, used for growing
vegetables and other intensive cultivation, to as large as two hectares or more, used for
growing rice under wet land conditions. When the land can be graded economically into
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nearly level fields, the basins are rectangular in shape. In rolling topography the ridges
follow the contours of the land surface. The contour ridges are connected by cross
ridges at intervals. The vertical interval between contour ridges usually varies from 6 to
12 cm. in case of upland irrigated crops like wheat and 15 to 30 cm in case of low land
irrigated crops .like rice.
Advantages
i.Since in this method the entire area is not flooded, it ensures -high water use
efficiency.
ii. Excessive seepage loss can be avoided by adopting this practice
iii. Damage to plants and loss of soil nutrients do not occur in this practice:..
Disadvantages
i. The major disadvantage of check basin method of irrigation is that the ridges interfere
with the movement of animal drawn or tractor drawn implements for inter culture
operations or harvesting of crops.
ii. Considerable land is occupied by ridges and lateral field channels and crop yields are
substantially reduced.
iii. The method impedes surface drainage.
iv. Precise land grading and shaping are required.
v. Labour requirement in land preparation and irrigation are much higher.
vi. Ridges interfere with the movement of animal-drawn or tractor-drawn implements
for interculture or harvesting of crops
vii. it is not suitable for irrigated crops which are sensitive to wet soil conditions around
the stems of' plants
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Soils, Land Topography: Check basin irrigation is suited to smooth gentle and uniform
land slopes and for soils havening moderate to slow infiltration rates. Steep slopes
require complex layouts and heavy land levelling.
Crops: Both row crops and close-growing crops are adapted to be used with basins as
long as the crop is not affected by temporary inundation or is planted in beds so that it
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will remain above the water level. The method is especially adapted to irrigation of
grain and fodder crops in heavy soils where water is absorbed very slowly and is
required to stand for a relatively long time to ensure adequate irrigation. It is also
suitable in very permeable soils which must be covered with water rapidly to prevent
excessive deep percolation losses at the upstream end.
Practically all irrigated paddy is grown in basins. Check basins are useful when
leaching is required to remove salts from the soil profile. The method enables the
conservation of rainfall and reduction in soil erosion by retaining a large part of the rain
in the basin to be infiltrated gradually, without loss due to surface runoff. The method
usually results in high water application and distribution efficiencies if the desired net
depth of irrigation can be estimated adequately and if the size of the irrigation stream is
measured properly. The low efficiencies obtained in check basin irrigation in India are
due to inadequate land levelling and uncontrolled water application.
In irrigating orchards, square to contour basins may be used as in other crops.
When the plants are widely spaced the ring method of basin irrigation is adopted. The
rings are circular basins formed around each tree. The ring basins are small when the
plant is young. The size is increased as the plant grows.
Check basin irrigation is suited to smooth, gentle and uniform land slopes and
for soils having moderate to slow infiltration rates. Steep slopes require complex layouts
and heavy land levelling. Both row crops as well as close growing crops are adapted to
basins as long as the crop is not affected by temporary inundation. The method is
especially adopted for, irrigation of grain and fodder crops in heavy, soils where water is
absorbed very slowly. It is also suitable in very permeable soils which must be covered
with water rapidly to prevent i excessive deep percolation loss of water at the upstream
end.
Ring basin irrigation: In irrigation orchards, square or contour basins may be used as in
other crops. When the plants are widely spaced the ring method of basin irrigation may
be adopted. The rings are circular basins formed around each tree. The ring basins are
small when the plant is young. The size is increased as the plant grows. An advantage of
the ring method is that the entire area is not flooded, thus obtaining high water use
efficiency. Usually there is one basin to a tree. In rectangular and contour basins,
however, however may be one basin to a single tree or two or more trees.
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Border strip method
The border method of irrigation makes use of parallel ridges to guide a sheet of
flowing water as it moves down the slope. The land is divided into a number of long
parallel strips called borders that are separated by low ridges. The border strip has little
or no cross slope but has a uniform gentle slope in the direction of irrigation. The
essential feature of border irrigation is to provide an even surface over which the water
can flow down the slope with a nearly uniform depth. Each strip is irrigated
independently by turning into a stream of water at the upper end. The water spreads andflows down the strip in a sheet confined by the border ridges. The irrigation stream must
be large enough to spread over the entire width between the border ridges without over
topping them. When the advancing water front either reaches the lower end, or a few
minutes before or after that, the stream is turned off. The water temporarily stored in the
border moves down the strip and infiltrates into the soil, thus completing the irrigation.
It is adapted to most soils where depth and topography permit, 1 the required land
leveling at a reasonable cost and without any permanent reduction in soil fertility. It is,
however, more suitable to soils having moderately low to moderately high infiltration
rates. It is generally not used in coarse sandy soils that have very high infiltration rates.
It is also not well suited to soils having a very low infiltration rate. This method is
suitable to irrigate all close growing crops like wheat, barley, fodder crops and legumes.
It is, however, not suitable for crops like rice which requires standing water during most
part of its growing season.
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Straight and contour borders
If the borders are constructed along the general slope of the field, they are
known as straight borders or slope borders, and if they are constructed across the
general slope of the field they are called contour borders. When fields can be levelled to
desirable land slopes economically and without affecting its productivity, graded
borders are easier to construct and operate. In case where land slope exceeds safe limit,
fields are undulating and levelling is not feasible, borders may be laid across the slope.
The design of a contour border is the same as that of a straight border. Each contour
border is level crosswise and has a uniform longitudinal gradient as in a straight border.
The width and length of a contour border are identical to that of a straight border for a
particular set of conditions.
In laying contour borders, the field is divided into a series of strips on the
approximate contour, and each strip is levelled as an independent area. Thus, a series of
strips are formed in successive elevations around the slope. The vertical interval
between the adjacent benches should, as far as possible, be limited to 30 cm, but should
not exceed 60 cm. The height of ridge should be sufficient to check both the normal
irrigation stream and run-off.
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Soils, Land Topography & wetting pattern: The border method of irrigation is
adapted to most soils where depth and topography permit the required land levelling at a
reasonable cost and without permanent reduction in soil productivity. It is, however,
more suitable to soils having moderately low to moderately high infiltration rates.
Usually it is not used in coarse sandy soils that have very high infiltration rates because
of the stringent limitations in design: It is also not well suited to soils having a very low
infiltration rate, since to provide adequate infiltration opportunity time, without surface
runoff at the lower end, the irrigation stream may be too small to completely over the
border strips.
The border method is suitable to irrigate all close growing crops like wheat,
barley, fodder crops and legumes. It is, however, not suitable for crops like rice which
requires standing water during most parts of its growing season.
Border Specifications and Stream Size
Successful operation of the border method requires that the system is designed
and operated properly. Proper design requires consideration of the hydraulics of flow in
borders which are described in the following article. However, some general
suggestions on width, length and slope of borders and size of irrigation streams are
presented in this article.
Width of border strip. The width of a border usually varies from 3 to 15 metres,
depending on the size of the irrigation stream available and the degree of land leveling
practicable. When the size of the irrigation stream available is small, the width is
reduced.' It is, however, not economical to keep the width less than about three metres;
as otherwise, too many ridges will have to be formed per unit area of the field surface.
Border length. The length of the border strip depends upon how quickly it can be
wetted uniformly over its entire length. This in turn depends on the infiltration rate of the soil, the slope of the land, and the size of the irrigation stream available. For
moderate slopes and small to moderate size irrigation streams, the following border
lengths are suggested:
Sandy and sandy loam soils: 60to 120 metres
Medium loam soils : 100 to 180 metres
Clay loam and clay soils : 150 to 300 metres
Border slope. The borders should have a uniform longitudinal gradient. Excessive
slopes will make the water run to the lower and quickly, causing insufficient
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irrigation at the upstream end and deep percolation losses and breach the bund at the
downstream. They also cause soil erosion in borders. On the other hand, too flat
slopes will result in the very slow movement of the border stream, causing deep
percolation losses at the upper reaches and inadequate wetting downstream.
Recommended safe limits of land slopes in borders are given below:
Sandy loam to sandy soils : 0.25% to' 0.60%
Medium loam soils : 0.20% to 0.40%
Clay to clay loam soils : 0.05% to 0.20%
Size of irrigation stream. The size of the irrigation stream needed depends on the
infiltration rate of the soil and the width of the border strip. Coarse textured soils with
high infiltration rates require large streams to spread water over the entire strip
rapidly and avoid excessive losses due to deep percolation at the upper reaches. Fine
textured soils with low infiltration rates require smaller streams to avoid excessive
losses due to runoff at the downstream end and deep percolation at the lower reaches.
Advantages
i. It is easy to construct border ridges even with some simple farm implements like a
bullock drawn A-frame ridger or tractor-drawn disc ridger.
ii. Labour requirement in irrigation is greatly reduced as compared to the conventional
check basin method of irrigation.
iii. Uniform distribution and high water application efficiencies are possible if the
system is properly designed.
iv. Large irrigation streams can be efficiently used.
v. Operation of the system is simple and easy.
vi. Adequate surface drainage is provided if outlets are available
Disadvantages
i. It requires an extensive land grading which is too expensive.
ii. It is mainly suitable for deep soils with the availability of large flow of water.
iii. Drainage may be essential.
iv. Water wastage is frequently observed.
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Furrow irrigation
The furrow method of irrigation is used in irrigation of row crops with furrows
developed between the crop rows in the planting and cultivating processes. The size and
shape of the furrow depends on the crop grown, equipment used and spacing betweencrop rows. Water is applied by running small streams in furrows between the crop rows.
Water infiltrates into the soil and spreads laterally to , irrigate the areas between the
furrows. The length of time water takes to flow in the furrows depends on .the amount
of water required to replenish root zone and the infiltration rate of the soil. Both large
and small irrigation streams can be used by adjusting the number of furrows irrigated at
anyone time to suit the available flow. In areas where surface drainage is necessary, the
furrows can be used to dispose off the run-off from rainfall rapidly.
Irrigation furrows may be classified into two general types is based on their
alignment. They are (i) straight furrows, (ii) contour furrows. Based on their size and
spacing furrows, may be classified as deep furrows and corrugation.
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a. Deep furrows
As mentioned above, deep furrows are of two types i.e. straight furrows and
contour furrows.
i. Straight furrows
Straight furrows, like borders, are laid down across the prevailing land slope. They are
best suited to sites where the land slope does not exceed 0.75 per cent. In areas of
intense rainfall, however, the furrow grade should not exceed 0.5 % so as to
minimisethe erosion hazard.
Straight furrows, like borders, are laid down the prevailing land slope. They are
best suited to sites where the land slope does not exceed 0.75 per cent. In areas of
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intense rainfall, however, the furrow grade should not exceed 0.5 per cent so as to
minimise the erosion hazard. The ranges in furrow slopes for efficient irrigation in
different soil types are the same as those recommended for borders.
In fine textured soils having very low infiltration rates, the furrows usually levellengthwise. With level furrows, the same stream size is maintained until the required
amount of water is applied. The water is ponded in the furrows until it is absorbed by
the soil.
ii. Contour furrows
Contour furrow method is similar to the graded furrow method in that the
irrigation water is applied in furrows, but the furrows carry water across the sloping
field rather than down the slope. Contour furrows are curved to fit the topography of the
land. The furrows are given gentle slope along its length as in the case of graded
furrows. Field supply channels rundown the land slope to feed the individual furrows
and are provided with erosion control structures.
Suitability to crops, soils and Land Topography:
Furrow irrigation can be used to irrigate all cultivated crops planted in rows, including
orchards and vegetables. Amongst the common cultivated crops of India, the method issuitable for irrigating maize, sorghum, sugarcane, cotton, tobacco, groundnut, potatoes,
and other vegetables. Furrows are particularly well adapted to irrigating, crops which
are subject to injury from pounded surface water or susceptible to fungal root rot.
Furrow irrigation is suitable, to most soils except sands that have a very high infiltration
rate and provide poor lateral distribution of water between furrows.
The furrow method maybe adapted to use, without erosion, on a wide range of natural
slopes by carrying the furrows across a slopping field rather than down the slope. The
method reduces labour requirements in land preparation and irrigation. Compared to
check basin method, there is no wastage of land in field ditches.
Furrow irrigation requires proper land grading. The land must be graded so that
water can travel the entire length of the row without ponding. This means that the high
and low spots must be removed and the land given enough slope to let the water flow
down the furrows. Once level, care in tillage operations can keep the land levelled.
Furrows can be spaced to fit the crops grown and the standard machines used for
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planting and cultivating. Crops like potatoes, maize and cotton have furrows between all
rows. Vegetable crops such as lettuce, carrots, and onions often have two or more rows
between furrows. Wide spaced crops, like melons, fruits trees and berries generally
require more than one furrow between crop rows. Furrows should be spaced close,
enough to ensure that water spreads to the sides into the ridge and root zone of the crop
before it moves down below the root zone.
In heavy black soils a combination of border strip irrigation with furrows is
usually preferred. These soils crack badly, so it is desirable to have furrows within the
border strips, so cracking will not allow the water to escape from furrow to furrow. The
border ridges are sufficiently large to confine the flow within the strip and the furrows
distribute it uniformly. Another advantage is that the furrows provide uniform drainage
during heavy monsoon rains and erosion is kept at a minimum.
Contour furrow method can be successfully used in nearly all irrigable soils. The
limitations of straight furrow irrigation are overcome by contouring to include sloping
lands. Light soils can be irrigated successfully across slopes up to 5 per cent. Where the
soils are stable and will not be cultivated (as in orchards), slopes up to eight to ten per
cent can be irrigated by contour furrowing. All row crops·, including grains, vegetables
and various cash crops, are adapted to this method.
The topography must be uniform enough to permit a head ditch that can feed the
entire area of contour-furrow. It must also be regular enough to permit installing a waste
ditch to carry off surplus irrigation water and rain water. Fields should be smoothed as
much as possible by land grading and by using a float, or land plane, before contour
plantings are laid out.
Contour-furrows for row crops are installed annually. But in orchards and other
permanent contour plantings, the same furrows and ditches are used every year, and
they may be considered as a permanent part of the water handling system. Furrows and
waste ditches should be cleaned out and prepared for the rainy seasons immediately
after crops are harvested.
Contour furrows may be used on most soil types, except on light sandy soils and
soils that crack. The ridges between furrows in sandy soils may break and wash out,
overloading the furrow below, which also breaks. This may continue all the way down
the slope causing heavy erosion damage. Soils that crack provide channels for water,
causing similar down slope furrow breaks. Hence their use is limited on steep slopes in
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sandy soils and heavy black soils.
In heavy rainfall areas the length of furrows should be short enough to dispose
off the runoff safely without breaking the furrows. Erosion control structures are needed
to carry the surplus water down the slope. Contour furrow irrigation .used inconjunction with contour bunding and terracing provides an insurance against furrow
breaks. Land which is too steep for contour furrows may sometimes be graded to
levelled strips (bench terraces) across the slope on which the furrows can be
constructed. Land with slopes upto 25 per cent or more can be benched to permit the
production of irrigated crops.
Advantages
i. Water in the furrows contacts only one half to one fifth of the land surface, therebyreducing puddling and crusting of the soil, and evaporation losses.
ii. Early sowing is possible which is a distinct advantage in heavy soils.
iii. It can be safely adopted on the sloppy lands by opening the furrows across the slope.
iv. This .method reduces labour requirement in land preparation and Irrigation.
v. Compared to check basin method, there is no wastage of land in field ditches.
Disadvantages
i. It requires skilled labourers to operate. .
ii. It may cause serious erosion, if excess water flows over the ridges.
iii. Difficult to carry on mechanical operations.
iv. Water in the furrows contacts only one-half to one-fifth of the land surface, thereby
reducing puddling, and crusting of the soil, and evaporation losses
v. Earlier cultivation is possible which is distinct advantage in heavy soils.
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