​

UNIT-2�IRRIGATION METHODS

Syllabus

IRRIGATION METHODS

Tank irrigation – Well irrigation – Irrigation methods: Surface and Sub-Surface and Micro Irrigation – design of drip and sprinkler irrigation – ridge and furrow irrigation-Irrigation scheduling – Water distribution system- Irrigation efficiencies.

​

Tank irrigation

​

• A tank is a reservoir for irrigation, a small lake or pool made by damming the valley of a stream to retain the monsoon rain for later use.
• It accounts for approximately 3% of the net irrigated area in India. Tank Irrigation is popular in the peninsular plateau area where Andhra Pradesh and Tamil Nadu are the leading states.
• Andhra Pradesh has the largest area (29%) of tank irrigation in India followed by Tamil nadu (23%).
• Tanks are known as Ery in Tamil. The temple tanks of Tamil Nadu are known as Kulam.

Irrigation Tank

Kinds of Tanks

1. System Tanks and
2. Non-System Tanks.

​

System Tanks

• The canal fed tanks are known as System Tanks, which were exclusively under the management of the Public Works Department.
• The System Tanks are fed with water from rivers and run off through diversion weirs, feeder channels and surface flow.
• System Tanks are the minority of tanks that are supplied from major storage canal irrigation systems or from perennial rivers.

System Tanks

Non System Tanks

• The rain fed tanks are known as Non-System Tanks.
• NonSystem Tanks which command area below 40 hectares are coming under the control of Panchayat Unions.
• These Non-System Tanks have a small storage capacity.

Non System Tanks

Merits

• Most of the tanks are natural
• Do not involve cost for their construction
• Independent source for an individual farmer
• longer life span
• can be used for fishing also

​

• Demerits
• Depends on rain
• These tanks may dry up during the dry season
• Silting of their beds
• Require large areas
• Evaporation losses
• Need to lift the water to take it to the field

​

Wells (and Tube Wells)

​

• A well is a hole dug in the ground to obtain the subsoil water.
• An ordinary well is about 3-5 metres deep but deeper wells up to 15 metres are also dug.
• This method of irrigation has been used in India from time immemorial.
• Various methods are used to lift the ground water from the well.

Well Irrigation

• Well irrigation is gradually giving way to energized tube wells.
• But there are many wells still in use where electricity is not available or the farmers are too poor to afford diesel oil.
• This method of irrigation is popular in those areas where sufficient sweet ground water is available.
• It is particularly suitable in areas with permeable rock structure which allows accumulation of ground water through percolation.

Well Irrigation

Merits

• Simplest
• Cheapest
• Well is an independent source of irrigation and can be used as and when the necessity arises.
• Canal irrigation, on the other hand, is controlled by other agencies and cannot be used at will.
• Some ground water salts are useful for crops
• Does not lead to salinization and flooding problems
• There is a limit to the extent of canal irrigation beyond the tail end of the canal while a well can be dug at any convenient place.

Demerits

​

• Only limited area can be irrigated.
• Normally, a well can irrigate 1 to 8 hectares of land.
• Not suitable for dry regions
• Overuse may lead to lowering of water table

SURFACE IRRIGATION:

​

• Surface irrigation is defined as the group of application techniques where water is applied and distributed over the soil surface by gravity.
• It is by far the most common form of irrigation throughout the world and has been practiced in many areas virtually unchanged for thousands of years.

SURFACE IRRIGATION

SUB SURFACE IRRIGATION

Surface irrigation

​

There are four variations under this method viz.

1. Flooding,
2. Bed or border method (Saras and flat beds)
3. Basin method (ring and basin) and
4. Furrow method (rides and furrows, broad ridges or raised beds)

• Flooding

• Bed or Border

• Basin Method

• Furrow Method

• It consist of opening a water channel in a plot or field so that water can flow freely in all directions and cover the surface of the land in a continuous sheet.
• It is the most inefficient method of irrigation as only about 20 percent of the water is actually used by plants.
• The rest being lost as a runoff, seepage and evaporation.
• Water distribution is very uneven and crop growth is not uniform.

Flooding

• It is suitable for uneven land where the cost of leveling is high and where a cheap and abundant supply of water is available.
• It is unsuitable for crops that are sensitive to water logging the method suitable where broadcast crops, particularly pastures, alfalfa, peas and small grains are produced.

Adaptations:

1. An abundant supply of water
2. Close growing crops
3. Soils that do not erode easily
4. Soils that is permeable
5. Irregular topography
6. Areas where water is cheap.

​

Advantages:

1. Can be used on shallow soils
2. Can be employed where expense of leveling is great
3. Installation and operation costs are low
4. System is not damaged by livestock and does not interfere with use of farm implements.

Disadvantages:

• Excessive loss of water by run of and deep percolation
• Excessive soil erosion on step land.
• Fertilizer and FYM are eroded from the soil.

Bed or border method (Sara and Flat beds or check basin):

• In this method the field is leveled and divided into small beds surrounded by bunds of 15 to 30 cm high.
• Small irrigation channels are provided between two adjacent rows of beds.
• The length of the bed varies from 30 meters for loamy soils to 90 meters for clayey soils.
• The width is so adjusted as to permit the water to flow evenly and wet the land uniformly.
• For high value crops, the beds may be still smaller especially where water is costly and not very abundant.

• It requires leveled land.It is more efficient in the use of water and ensures its uniform application.
• It is suitable for crops plant in lines or sown by broadcast.
• Through the initial cost is high requires less labour and low maintenance cost.

.

Types of Border Irrigation

1. Straight Border
2. Contour Border

Straight Border

• These are formed across the general slope of the field and are preferred when land slope exceeds the safe limits.
• As fields are undulating and require a lot of earth work to level, economical levelling is not possible. Design criteria for both are not different.

Straight Border

Contour Border

• These are formed across the general slope of the field and are preferred when land slope exceeds the safe limits.
• As fields are undulating and require a lot of earth work to level, economical levelling is not possible.
• Design criteria for both are not different.

Adaptations:

1. A large supply of water
2. Most soil textures including sandy Loam, loams and clays
3. Soil at least 90 cm deep
4. Suitable for close growing crops.

1. Advantages:
2. Fairly large supply of water is needed.
3. Land must be leveled
4. Suited only to soils that do not readily disperse.
5. Drainage must be provided

Basin irrigation

• This method is suitable for orchids and other high value crops where the size of the plot to be irrigated is very small.
• The basin may be square, rectangular or circular shape. A variation in this method viz. ring and basin is commonly used for irrigating fruit trees.
• A small bund of 15 to 22 cm high is formed around the stump of the tree at a distance of about 30 to 60 cm to keep soil dry.

• The height of the outer bund varies depending upon the depth of water proposed to retain.
• Basin irrigation also requires leveled land and not suitable for all types of soil.
• It is also efficient in the use of water but its initial cost is high.
• There are many variations in its use, but all involve dividing the field into smaller unit areas so that each has a nearly level surface.

Types of Check Basins

Rectangular

• The basins are rectangular in shape when the land can be graded economically into nearly level fields.

Contour

• The ridges follow the contours of the land surface and the contour ridges are connected by cross ridges at intervals when there is rolling topography.

Adaptations:

1. Most soil texture
2. High value crops
3. Smooth topography.
4. High water value/ha

Advantages:

• Varying supply of water
• No water loss by run off
• Rapid irrigation possible
• No loss of fertilizers and organic manures
• Satisfactory

Disadvantages:

1. If land is not leveled initial cost may be high
2. Suitable mainly for orchids, rice, jute, etc.
3. Except rice, not suitable for soils that disperse easily and readily from a crust.

Furrow Method

• In this method, irrigation water is useful for row crops. Narrow channels are dug at regular intervals.
• Water from the main supply is allowed to enter these small channels or furrows.
• Water from the furrows infiltrates into soil and spread laterally to saturate the root zone of the crops.
• It is suitable for row crops like potatoes, sugarcane, tobacco, maize, groundnut, cotton, jowar, etc.

Furrow Method

• It is suitable for sloppy lands where the furrows are made along contours.
• The length of furrow is determined mostly by soil permeability and it varies from 3 to 6 meters.
• In sandy and clay loams, the length is shorter than in clay and clay loams. Water does not come in contact with the plant stems.
• There is a great economy in use of water.

Types of Furrows

(a) straight furrows, and

(b) contour furrows.

Straight Furrows

• 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 per cent so as to minimise the erosion hazard.
• The range in furrow slopes for efficient irrigation in different soil types are the same as those recommended for borders.

Contour Furrows

• Contour furrows carry water across a slopping field rather than the slope. Contour furrows are curved to fitthe topography of the land.
• Contour furrow method can be successfully used in nearly all irrigable soils.
• The limitations of straight furrow are overcome by contouring to include slopping lands.
• Light soils can be irrigated successfully across slopes up to 5 per cent.

Adaptations:

Medium and fine textured soils.

Variable water supply

Farms with only small amount of equipment.

Advantages:

High water efficiency

Can be used in any row crop

Relatively easy in stall

Not expensive to maintain

Adapted to most soils.

Disadvantages:

Requirement of skilled labour is more

A hazard to operation of machinery

Drainage must be provided.

Furrow Method

Contour farming

• Contour farming involves ploughing, planting and weeding along the contour, i.e, across the slope rather than up and down.
• Contour lines are lines that run across a (hill) slope such that the line stays at the same height and does not run uphill or downhill.
• As contour lines travel across a hillside, they will be close together on the steeper parts of the hill and further apart on the gentle parts of the slope.

Benefits

1. Contouring can reduce soil erosion by as much as 50% from up and down hill farming.
2. By reducing sediment and run off and increasing water infiltration.
3. Contouring promotes better water quality.
4. It gives 10-15% additional yield.

Criteria for Surface Irrigation Method Selection

• The deciding factors for the suitability of any surface irrigation method are natural conditions (slope, soil type), type of crop, required depth of application, level of technology, previous experiences with irrigation, required labour input.
• Moreover the irrigation system for a field must be compatible with the existing farming operations, such as land preparation, cultivation, and harvesting practices.

Physical Factors

• Crops and cultural practices are of prime importance while selecting an irrigation system.
• Hence, proper knowledge of agronomic practices and irrigation intervals is necessary for proper use of irrigation water and to increase water use efficiency.

​

Crop Parameters

• Tolerance of the crop to soil salinity during development and maturation.
• Magnitude and temporal distribution of water necessary for maximum production.
• Economic value of crop.

Soils Parameters

• Texture and structure;infiltration rate and erosion potential;salinity and internal drainage, bearing strength.
• Sandy soils have a low water storage capacity and a high infiltration rate.
• High intake characteristicrequire higher flow rate to achieve the same uniformity and efficiency.
• Crusting of soil and its effects on infiltration
• Reclamation and salt leaching- basin irrigation
• Spatial variability

Field Topography

• Uniform, mild slopes facilitate surface irrigation.
• Location and relative elevation of water source – water diversion, pumping
• Acreage in each field
• Location of roads, natural gas lines, electricity lines, water lines and other obstructions.
• Shape of field – non rectangular shapes are more difficult to design for Field slope – steepness & regularity

Climate and Weather Conditions

• Under very windy conditions, drip or surface irrigation methods are preferred.
• Scalding (the disruption of oxygen-carbon dioxide exchange between the atmosphere and the root) & the effect of water temperature on the crop at different stages of growth -risk in basin irrigation.
• Irrigation with cold water early in the spring can delay growth, whereas in the hot periods of the summer, it can cool the environment— both of which can be beneficial or detrimental in somecases.

Water Supply

• Source and delivery schedule
• Water quantity available and its reliability
• Water quality
• Water table in case of ground water source.
• Availability and Reliability of Electricity
• Availability and reliability of energy for pumping of water is of muchimportance.

Economic Considerations

1. Capital investment required and recurring cost.
2. Credit availability and interest rate.
3. Life of irrigation system, efficiency and cost economics.

Social Considerations

1. The education and skill of common farmers and labours available for handling the irrigation system
2. Social understanding of handling of cooperative activities and sharing of water resources
3. Legal and political considerations, local cooperation and support, availability and skill of labour and level of automatic control

Suitability and Limitations of Surface Irrigation Methods

• Some form of surface irrigation is adaptable to almost any vegetable crop.
• Basin and border strip irrigation have been successfully used on a wide variety of crops.
• Furrow irrigation is less well adapted to field crops if cultural practices require travel across the furrows. However, it is widely used in vegetables like potato.
• Basin and border strip irrigations flood the soil surface, and will cause some soils to form a crust, which may inhibit the sprouting of seeds.

Surface irrigation systems perform better when soils are uniform, since the soil controls the intake of water.

For basin irrigation, basin size should be appropriate for soil texture and infiltration rate.

Basin lengths should be limited to 100 m on very coarse textured soils, but may reach 400 m on other soils.

Furrow irrigation is possible with all types of soils, but extremely high or low intake rate soils require excessive labor or capital cost adjustments that are seldom economical.

MICRO IRRIGATION METHOD

MICRO IRRIGATION METHOD

• Micro irrigation methods are precision irrigation methods of irrigation with very high irrigation water efficiency.
• In many parts of the country there is decline of irrigation water and conventional methods are having low water use efficiency.
• To surmount the problem, micro irrigation methods has recently been introduced in Indian agriculture.

• These methods save a substantial amount of water and helps increasing crop productivity particularly valuable cash crops like vegetables.
• The research results have confirmed a substantial saving of water ranging between 40 to 80% and there are reports of two times yield increase for different crops by using micro irrigation.

Advantages of Micro Irrigation

(a) Water saving, possibility of using saline water.

(b) Efficient and economic use of fertilizers.

(c) Easy installation, flexibility in operation.

(d) Suitable to all types of land terrain also suitable to waste lands.

(e) Enhanced plant growth and yield and uniform and better quality of produce.

(f) Less weed growth.

(g) Labour saving.

(h) No soil erosion, saves land as no bunds, etc. are required.

(i) Minimum diseases and pest infestation.

SPRINKLER IRRIGATION

SPRINKLER IRRIGATION

• In sprinkler irrigation, water is delivered through a pressurized pipe network to sprinklers nozzles or jets which spray the water into the air.
• To fall to the soil in an artificial "rain". The basic components of any sprinkler systems are : a water source. a pump to pressurize the water.
• A pipe network to distribute the water throughout the field. sprinklers to spray the water over the ground, and valves to control the flow of water.
• The sprinklers when properly spaced give a relatively uniform application of water over the irrigated area.

Components of

Sprinkler Irrigation System

General Classification of Sprinkler Systems

(a) Rotating head or revolving sprinkler system.

(b) Perforated pipe system.

Components of Sprinkler Irrigation System

(a) A pump unit

(b) Tubings-main/sub-mains and laterals

(c) Couplers

(d) Sprinker head

(e) Other accessories such as valves, bends, plugs and risers.

Suitability and Limitations

​

• With regards to crops, soils, and topography nearly all crops can be irrigated with some type of sprinkler system though the characteristics of the crop especially the height, must be considered in system selection.
• Sprinklers are sometimes used to germinate seed and establish ground cover for crops like lettuce alfalfa and sod.
• The light frequent applications that are desirable for this purpose are easily achieved with some sprinkler systems.
• Sprinklers are applicable to soils that are too shallow to permit surface shaping or too variable for efficient surface irrigation.

• In general, sprinklers can be used on any topography that can be formed.
• Land leveling is not normally required.
• With regards to labour and energy considerations, it has been observed that labour requirements vary depending on the degree of automation and mechanization of the equipment used.
• Hand-move systems require the least degree of skill, but the greatest amount of labor.

Suitability and Limitations

Advantages of Sprinkler Irrigation

(a) Elimination of the channels for conveyance, therefore no conveyance loss.

(b) Suitable to all types of soil except heavy clay, suitable for irrigating crops where the plant population per unit area is very high. It is most suitable for oil seeds and other cereal and vegetable crops.

(c) Water saving, closer control of water application convenient for giving light and frequent irrigation and higher water application efficiency.

(d) Increase in yield.

Advantages of Sprinkler Irrigation

(e) Mobility of system.

(f) May also be used for undulating area, saves land as no bunds etc. are required, areas located at a higher elevation than the source can be irrigated.

(g) Influences greater conducive micro-climate.

(h) Possibility of using soluble fertilizers and chemicals.

(i) Less problem of clogging of sprinkler nozzles due to sediment laden water

Capacity of Sprinkler System

​

​

​

Where,

Q = Discharge capacity of the pump, liter/second,

A = Area to be irrigated, hectares,

d = Net depth of water application, cm,

F = Number of days allowed for the completion of

one irrigation,

H = Number of actual operation hours per day, and

E = Water Application Efficiency in %

​

​

​

​

​

​

​

​

​

​

​

​

​

​

​

​

​

​

​

​

​

​

​

DRIP IRRIGATION

​

​

DRIP IRFUGATION

• Drip irrigation, also known as trickle irrigation or microirrigation is an irrigation method which minimizes the use of water and fertilizer by allowing water to drip slowly to the roots of plants, either onto the soil surface or directly onto the root zone, through a network of valves, pipes, tubing, and emitters.
• It is becoming popular for row crop irrigation.
• This system is used in place of water scarcity as it minimizes conventional losses such as deep percolation, evaporation and run-off or recycled water is used for irrigation.

• Small diameter plastic pipes fitted with emitters or drippers at selected spacing to deliver the required quantity of water are used.
• Drip irrigation may also use devices called micro-spray heads, which spray water in a small area, instead of dripping emitters.
• Subsurface drip irrigation (SDI) uses permanently or temporarily buried drip per line or drip tape located at or below the plant roots.
• Pump and valves may be manually or automatically operated by a controller Drip irrigation is the slow, frequent application of water to the soil though emitters placed along a water delivery line.

• The term drip irrigation is general, and includes several more specific methods.
• Drip irrigation applies the water through small emitters to the soil surface, usually at or near the plant to be irrigated.
• Subsurface irrigation is the application of water below the soil surface.
• Emitter discharge rates for drip and subsurface irrigation are generally less than 12 liters per hour.

DRIP IRFUGATION

Components of Drip Irrigation System �(Listed in Order from Water Source)

​

(a) Pump or pressurised water source.

(b) Water Filter(s) - Filtration Systems : Sand Separator, Cyclone, Screen Filter, Media Filters.

(c) Fertigation Systems (Venturi injector).

(d) Backwash Controller.

(e) Main Line (larger diameter Pipe and Pipe Fittings).

(f) Hand-operated, electronic, or hydraulic Contvl Valves and Safety Valves.

(g) Smaller diameter polytube (often referred to as "laterals").

(h) Poly fittings and Accessories (to make connections).

(i) Emitting Devices at plants (Example : Emitter or Drippers, micro spray heads, inline drippers, trickle rings)

Components of Drip Irrigation System

Suitability and Limitation

(a) From stand point of crops, soil, and topography, drip irrigation is best suited for tree, vine, and row crops.

(b) With respect to water quantity and quality, drip irrigation uses a slower rate of water application over a longer period of time than other irrigation methods.

(c) Though a form of pressurized irrigation, drip is a low pressure, low flow rate method.

(d) High efficiencies are USP of drip irrigation system. Properly designed and maintained drip systems are capable of high efficiencies. Design efficiencies should be on the order of 90 to 95%.

(e) Labour and energy considerations are very important consideration in drip irrigation system.

(f) Drip irrigation systems generally use less energy than other forms of pressurized irrigation systems.

(g) Economic factors need special attention in case drip irrigation system as initial cost and operational cost is reasonably high.

(h) Drip systems costs can vary greatly. Depending on crop (plant. and therefore emitter and hose spacings) and type of hose employed (permanent or "disposable" thin-walled tubing).

Advantages

1. Minimised fertilizer nutrient loss due to localized application and reduced leaching, allows safe use of recycled water.
2. High water distribution efficiency. Moisture within the root zone can be maintained at field capacity.
3. Leveling of the field not necessary. Soil type plays less important role in frequency of irrigation, minimised soil erosion.
4. Highly uniform distribution of water, i.e. controlled by output of each nozzle.
5. Lower labour cost.
6. Early maturity and good harvest.
7. Foliage remains dry thus reducing the risk of disease.

FERTIGATION

• Fertigation is the process of application of water soluble solid fertilizer or liquid fertilizers through drip irrigation system.
• Through fertigation nutrients are applied directly into the wetted volume of soil immediately below the emitter where root activity is concentrated.
• Fertigation is practiced only in drip irrigation system. However, fertilizer solution can be added with sprinkler irrigation system also.

FERTIGATION

Components of Fertigation

The main component of a fertigation is drip irrigation system. The main components are :

(a) Venturi pump (injector)

(b) Fertilizer tank with flow bypass

(c) Pressure bypass tank

(d) Injection pump.

Advantages of Fertigation

1. The fertilizer solution is distributed evenly in the irrigation network with the same uniformity as the irrigation water.
2. The availability of nutrients including micro-nutrients is high, therefore the efficiency is very good.
3. The fertilizer system can also be used for other activities such as incorporating acid to flush the drip system.
4. It eliminates the work of spreading fertilizer. Manual spreading of fertilizer causes soil compaction and may damage the growing crop.

1. Fertilizer placement is exactly to the root zone of plant and can be uniformly applied through drip irrigation system.
2. All types of nutrients can be given simultaneously.
3. Lower doses of fertilizer could be applied daily or weekly (i.e. a large number of split application) to avoid leaching and fixation in soil.
4. Some liquid fertilizers are free of sodium and chloride salts, so these are not harmful to soil.
5. Optimum production in light soil is possible.

1. Spraying with liquid fertilizer is possible.
2. Liquid fertilizers are immediately available to plants.
3. Fertilizer use efficiency can be increased by 25 to 30% over the tradition method of fertilizer application.
4. It decreases labour and energy cost.
5. The quality and quantity of crop production can be improved

Limitations

• The main one is the danger of poisoning people who drink the irrigation water particularly laborers those work on the farm.
• It is therefore necessary to warn the people in the field about drinking water separately and put up warning signs.
• Toxicity and Contamination
• Fertilizer Suitability
• Corrosion

Irrigation scheduling

Irrigation scheduling is the process used by irrigation system managers to determine the correct frequency and duration of watering.

Advantages of Irrigation Scheduling

• It enables the farmer to schedule water rotation among the various fields to minimize crop water stress and maximize yields.
• It reduces the farmer’s cost of water and labour
• It lowers fertilizer costs by holding surface runoff
• It increases net returns by increasing crop yields and crop quality.
• It minimizes water-logging problems
• It assists in controlling root zone salinity problems
• It results in additional returns by using the “saved” water to irrigate non-cash crops

Water distribution system

Irrigation water inay be applied to crops either by flooding the field by applying water beneath the soil surface, by spraying it under pressure or by applying it in drops.

Selection of the suitable method, from among these methods, depends on topography, soil condition, land preparation, type of crop and its value, available water supply and other factors

Water distribution system

BORDER IRRIGATION

CHOICE OF METHOD OF IRRIGATION

• Natural conditions (slope & soil type).
• Type of crop,
• Level of technology that is available,
• Previous experience with the practice of irrigation and
• Required labour inputs.

Irrigation Efficiencies

• Efficiency is the ratio of the water output to the water input, and is usually expressed as percentage.
• Input minus output is nothing but losses, and hence, if Losses are more, output is less and, therefore, efficiency is less. Hence, efficiency is inversely proportional to the losses.
• Water is lost in irrigation during various processes and, therefore, there are different kinds of irrigation efficiencies

Kinds of irrigation efficiencies

1. Efficiency of Water-conveyance
2. Efficiency of Water Application
3. Efficiency of Water Use
4. Efficiency of water storage
5. Water Distribution Efficiency

Efficiency of Water-conveyance (η_c)

It is the ratio of the water delivered into the fields from the outlet point of the channel, to the water entering into the channel at its starting point. It may be represented by η_c. It takes the conveyance or transit losses into consideration.

η_c = (W_f/W_r) X 100

Where

η_c= Water conveyance efficiency,

W_f = Water delivered to the irrigated plot at field supply Channel,

W_r = Water diverted from the source ( river or reservoir )

Efficiency of Water Application (η_a)

It is ratio of water stored into the root zone of the crop to the quantity of water delivered at the field (Farm).

η_a =W_s/W_f X 100

Where,

η_a = Water application efficiency,

W_s = Water stored at the root zone during the irrigation

W_f = Water delivered to the farm.

Efficiency of Water Use (η_u)

It is the ratio of the water beneficially used including leaching water, to the Quantity of water delivered. It may be represented by η_u

η_u = (Wu/Wd) X 100

Where,

η_u = Water use efficiency,

Wu = Beneficial use of water or consumptive.

Wa = Water delivered to the field.

Efficiency of water storage: (η_s)

The concept of water storage efficiency gives an insight to how completely the required water has been stored in the root zone during irrigation.

η_s = (Ws/Wn )X 100

Where,

η_s= Water storage efficiency,

Ws = water stored in the root zone during irrigation.

Wn = Water need in the root zone prior to irrigation.

Water Distribution Efficiency (η_d)

Water distribution efficiency evaluates the degree to which water is uniformly distributed throughout the root zone.The more uniformly the water is distributed , the better will be crop response.

η_d =100 (1-y/d)

Where,

η_d= Water distribution efficiency,

y= avg numerical deviation in depth of water stored from avg depth stored in the root zone during irrigation

d = Avg depth of water stored during irrigation.

Consumptive use Efficiency (η_cu)

It is the ratio of consumptive use of water to the water depleted from the root zone.

η_cu = (W_cu/W_d)X 100

Where,

η_cu= Consumptive use efficiency,

W_cu= Nominal consumptive use of water

W_d = Net amount of water depleted from the root zone soil.

Discussions ?