Unit 2 Irrigation Methods
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This document provides information on various irrigation methods including micro irrigation, sprinkler irrigation, and drip irrigation. Micro irrigation methods like drip irrigation and sprinkler irrigation are described as having high water use efficiency of 40-80% compared to conventional methods. The key components and advantages of drip irrigation systems are outlined, including precise water application and fertilizer use, water savings of 40-70%, and suitability for different soil types. Sprinkler irrigation is described as useful for irregular land, excessive slopes, or scarce water availability, and the main components of sprinkler systems are identified. Contour farming is also briefly introduced as a method used on steep slopes where land is divided into horizontal terraces.
Unit 2 Irrigation Methods
- 1. UNIT-2 IRRIGATION METHODS A.Leema Margret, Assistant Professor (Civil), Ramco Institute of Technology, Rajapalayam
- 2. 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.
- 24. Contour Farming • This method is adopted in hilly areas Where the land has steep slopes. • Land is divided into series of horizontal strips aligned along the contours of land known as terraces or benches. • Small bunds are provided at the end of each terrace to hold water upto the required depth.
- 27. 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.
- 28. 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.
- 29. 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.
- 32. This method is useful when, o Land topography is irregular o Land slopes are excessive o Land cannot be prepared for surface methods o Soil is erosive o Soil is excessively permeable or highly impermeable o Water is available with difficulty and scarce o Water table is high
- 34. Components of Sprinkler Irrigation System
- 35. Components of Sprinkler Irrigation System (a) A pump unit (b) Mainline and sometimes sub-mainlines (c) Laterals (d) Risers (e) Sprinklers (f) Fertilizer injector or Fertigator
- 36. • A pump unit usually a centrifugal pump which takes water from a well/water source and provides adequate pressure for delivery into the pipe system. • The mainlines and sub-mainlines are pipes which deliver water from the pump to the laterals. • The laterals delivers water from the mainlines usually movable. • The risers deliver water from lateral line to the sprinkler. The length of riser depends on the crop, although minimum value of 30cm is recommended to assume a good distribution pattern. Components of Sprinkler Irrigation System
- 37. • Sprinklers are used to spray the pressurized water through an orifice and rotates to distribute water onto the field. • Fertilizer injector is attached to the sprinkler system to inject chemicals or pesticides into irrigation mainline and applied to the land. • In addition to that valves are fixed to control the flow of water and flow meters, pressure gauges are provided to monitor system performance. Components of Sprinkler Irrigation System
- 38. Classification or types of Sprinkler Systems 1. Classification based on arrangement of spraying: (a) Perforated pipes sprinkler system. (b) Fixed Nozzle sprinkler system. (c) Rotating head or revolving sprinkler system. 2. Classification based on portability: (a) Permanent system. (b) Semi permanent system. (c) Fully Portable system.
- 39. (a) Perforated pipes sprinkler system
- 40. This method consists of drilled holes or nozzles along their length through which water is sprayed under pressure. This system is usually designed for relatively low pressure (1 kg/cm2)
- 41. (b) Fixed Nozzle sprinkler system
- 42. (c) Rotating head or revolving sprinkler system.
- 43. Small size nozzles are placed on riser pipes fixed at uniform intervals along the length of the lateral pipe and the lateral pipes are usually laid on the ground surface. They may also be mounted on posts above the crop height and rotated through 90degree , to irrigate a rectangular strip. In rotating type sprinklers, the most common device to rotate the sprinkler heads is with a small hammer activated by the thrust of water striking against a vane connected to it.
- 45. Formula to determine discharge, spread and capacity of sprinkler system 1. Sprinkler Discharge
- 47. 2. Spread of Sprinkler
- 48. 3. Capacity of Sprinkler System Where, Q = Discharge capacity of the pump, liter/sec, 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 of the pump per day, and E = Water Application Efficiency in %
- 49. Advantages of Sprinkler Irrigation
- 50. Disadvantages of Sprinkler Irrigation • High initial cost • Uneven water distribution due to high winds • Evaporation loss when operating under high temperatures • High water pressure required in sprinkler (>2.5kg/cm2 ) • Technical personnel for its operation and maintenance is required • Clean water is needed to avoid clogging of nozzles • It is not adopted in places where plenty of cheap water is available as surface methods are more useful and less costly • Pipe system laid on the soil surface may interfere with farm operations and movement of men and animals.
- 51. DRIP IRRIGATION
- 52. DRIP IRRIGATION Drip irrigation, also known as trickle irrigation is an irrigation method which minimizes the use of water and fertilizer by allowing water to drip slowly and directly applied to the root zone of the plants through a network of heads, mains, sub-mains, laterals and drip nozzles or 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. This method of drip irrigation was first introduced in Israel, but is now practised in many countries of the world.
- 54. Components of Drip Irrigation System • Pump Unit or Pressurised water source • Control Head (Gate valve, Pressure control valve, Filter, Fertilizer tank) • Mains and Submain Lines • Laterals or Trickle lines • Drippers or Emitters
- 55. DRIP IRRIGATION
- 57. • Pump Unit - A Pump to lift water so as to produce a desired pressure, for ensuring proper flow of water through the system. • Control Head - The lifted irrigation water through a fertilizer tank, so as to mix the fertilizer directly in the irrigation water, and then through a filter, so as to remove the suspended particles from the water, to avoid clogging of drip nozzles. • Mains and Submains – Specially designed small sized pipes, made of flexible material like black PVC. These are generally buried or laid on the ground. Components of Drip Irrigation System
- 58. • Laterals – very small sized (1 to 1.25 cm dia) and usually upto 50m long specially designed black PVC pipes, taking off from the mains or sub-mains. • Drippers – drippers or emitters are fixed on laterals, at regular interval of about 0.5 to 1 m and discharging water at very small rates of the order of 2 to 10 liters per hour.
- 59. Advantages 1. Less requirement of irrigation water (saves 40 to 70 % water compare to conventional methods) 2. Water logging avoided 3. High yield 4. Cultivation of cash crops 5. No over-irrigation 6. Weed control 7. Nutrients preservation 8. Effective pest control 9. Reduced labour cost 10. No soil Erosion 11. Suitability for saline soils 12.Suitable for any topography
- 60. Disadvantages 1. Initial setup cost of drip irrigation system is very high. 2. Danger of blockade of nozzles due to improper filtration. 3. Change in spacing of nozzles. 4. Requires high skill for installation and maintenance. 5. Flushing of tubes is required periodically. 6. Direct sunlight reduces the lifespan of the tubes used for supplying water. 7. Pipe network can be destroyed by pests.
- 61. Performance Indicator Conventional Irrigation Methods Drip Irrigation Water saving Waste lot of water. Losses occur due to percolation, runoff and evaporation 40-70% of water can be saved over conventional irrigation methods. Runoff and deep percolation losses are nil or negligible. Water use efficiency 30-50%, because losses are very high 80-95%
- 62. Saving in labour Labour engaged per irrigation is higher than drip Labour required only for operation and periodic maintenance of the system Weed infestation Weed infestation is very high Less wetting of soil, weed infestation is very less or almost nil. Use of saline water Concentration of salts increases and adversely affects the plant growth. Saline water cannot be used for irrigation Frequent irrigation keeps the salt concentration within root zone below harmful level Diseases and pest problems High Relatively less because of less atmospheric humidity
- 63. Suitability in different soil Type Deep percolation is more in light soil and with limited soil depths. Runoff loss is more in heavy soils Suitable for all soil types as flow rate can be controlled Water control Inadequate Very precise and easy Efficiency of fertilizer use Efficiency is low because of heavy losses due to leaching and runoff Very high due to reduced loss of nutrients through leaching and runoff water Soil erosion Soil erosion is high because of large stream sizes used for irrigation. Partial wetting of soil surface and slow application rates eliminate any possibility of soil erosion Increase in crop yield Non-uniformity in available moisture reducing the crop yield Frequent watering eliminates moisture stress and yield can be increased up to 15- 150% as compared to conventional methods of irrigation.
- 64. 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.
- 65. FERTIGATION
- 66. 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.
- 67. 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.
- 68. 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.
- 69. 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
- 70. 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
- 71. •Well and Tank Irrigation
- 72. Well Irrigation
- 75. Well Irrigation • It is a type of lift irrigation extracting water from the open well and tube well. OPEN WELL • An open well is a vertical hole dug in the ground to obtain the subsoil water • The diameter of open well vary from 2 to 9m and depth less than 20m. • It has small discharge capacity, usually 3 to 6 litres/sec • It draws water from one pervious stratum only. • The contribution of water is from the bottom and sides in the case of an unlined well and from the bottom only in the case of a lined well. • The open well may be classified into two types 1. Shallow open well 2. Deep open well
- 76. Well Irrigation Shallow and Deep open well • Shallow well rests in a pervious stratum and draws in supply from the surrounding materials • Deep open well rests on a impervious clay layer, through a bore hole made into it. • Pervious formation below the clay layer contain greater quantities of ground water and greater discharge can be obtained from deep open well.
- 77. Well Irrigation • A tube well is a deeper well over 15m deep and water is lifted with the help of pump set operated by electric motor or diesel engine. • It is a smaller diameter, large discharging well, usually 40-45litres/sec. • Shallow tube wells having 20 to 70m depth and tapping only one aquifer gives a yield of 15-20 litres/sec. • Deep tube wells having 70 – 300m depth • The main factors for tube well constructions 1. Extensive water bearing formation of adequate depth because a tube well can irrigate 2 hectares per day and 0.2 hectares per day by an open well 2. If the water table is more than 50 m deep, the cost of pumping unit for tube well becomes uneconomic 3. There should be electric supply to run the tube well TUBE WELL
- 78. Well Irrigation • Tube wells are classified into three types based on the entry of water through a cavity or a screen such as 1. Cavity type tube well 2. Strainer type tube well 3. Slotted type tube well 1. Cavity Type tube well
- 79. Well Irrigation 1. Cavity Type tube well • Cavity type tube well draws water from the bottom of the well and not from the sides. • The flow in a cavity well is spherical. • It consists of a pipe bored through the soil and resting on the bottom of a strong clay layer (i.e.) The impervious layer is punctured and a cavity is developed by pumping. • In the initial stage of pumping, fine sand comes out with water and consequently a cavity is formed. • After cavity gets formed at the bottom and the water from the aquifer enters the well pipe through this cavity. • Cavity type tube wells can be used for small supplies particularly for domestic purpose.
- 80. Well Irrigation 2. Strainer Type tube well
- 81. Well Irrigation 2. Strainer Type tube well • It is the most commonly used type of tube well in our country. • This tube well consists of plain or blind pipes and strainer pipes or screen pipes • Strainer type well uses strainer lengths lowered into the bore hole and located opposite the water bearing formation where as the plain pipe lengths are located opposite the non-water bearing formation. • Water enters into the well through these strainers from the sides and the flow is radial. • Strainer consists of perforations with a wire mesh wrapped around the pipe. • Wire screen prevents the sand particles from entering the well. • The well is generally plugged at bottom by cement concrete.
- 83. Well Irrigation 3. Slotted Type tube well
- 84. Well Irrigation 3. Slotted Type tube well • A slotted pipe tube well uses a slotted pipe without being covered by any wire mesh. • Such slotted pipe length are located opposite the water bearing formation as it is done with the strainers in a strainer type tube well. • Gravel packing is required around the screen pipes in the entire depth of well.
- 85. Three types of pumps are generally used to lift water from tube well. 1. Centrifugal pump. 2. Bore hole type pumps (Submersible pump and turbine type) 3. Jet pumps Centrifugal pump can be used when the maximum suction head is upto 8m. Bore hole type consists of centrifugal pump with impellers connected in series, mounted on vertical shaft and driven by motor. In a submersible pumps, the motor and the pump are both attached together and lowered inside the bore whereas in a turbine type, the pump is driven by a direct coupled electric motor. Shaft is placed at the top of line shaft at the ground level. Jet pump consists of a combination of centrifugal pump and a jet mechanism or ejector to increase the velocity of flow which creates pressure area to draw more water from well.
- 86. Well Irrigation Methods of lifting water from wells 1. Lifting of water from open well 2. Lifting of water from shallow tube well 3. Lifting of water from deep tube well 1. Lifting of water from open well • The pump set (Pump and Motor) is installed at the ground level and the strainer is provided sufficiently below the static water level of the open well.
- 87. Well Irrigation 2. Lifting of water from shallow tube well • The pump set is installed at the ground level and a cap is provided on the the well Top. • A check valve is provided just below the pipe connecting the pump with a tube well As shown in fig. • The supply of the water may be stopped If the static water level goes below the such As head.
- 88. Well Irrigation 3. Lifting of water from Deep tube well • In this system, a submersible pumpset Consists of electric motor an d a centrifugal Turbine pump is lowered into the tube well by suspended cable. • It is placed sufficiently below the lowest static water level as shown in fig. • The water is available throughout the year at constant flow rate.
- 89. Well Irrigation Advantages of Well Irrigation • Well is simples and cheapest source of irrigation and the poor farmer can easily afford it. • Well is an independent source of irrigation and it can be used as and when the necessity rises. • Well can be dug at any convenient place according to their requirement. • The farmer need not pay anything to other agencies for doing well irrigation
- 90. Well Irrigation Disadvantages of Well Irrigation • Only limited area can be irrigated. Normally a well can irrigate 1 to 8 hectares of land • Well may dry up and may be rendered useless for irrigation when excessive water is taken out • When drought comes, the ground water level falls and enough water is not available in the well • Tube wells can draw a lot of ground water from its neighbouring areas and make the ground dry and unfit for agriculture • Well irrigation is not possible in areas of salty ground water.
- 91. Tank Irrigation • Tanks are small sized reservoirs(a small lake or pool )formed by small earthern embankments to store runoff for irrigation. • There is no technical difference between a reservoir and a tank except that a large sized tank will be termed as reservoir. • Reservoir generally will be formed by dams of any material (Masonry, Concrete or Earth) whereas a tank is formed by earth dams or earthern bunds only. • Most of the tanks having maximum depth of 4.5 m while few are as deep as 9 m. • When the tank depth exceeds 12m, then it is referred to as a reservoir.
- 92. 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.
- 93. Kinds of Tanks Based on nature of supply of water: 1)System Tanks 2)Non-System Tanks 3)Grouped Tank or Tank in series 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.
- 94. System Tanks
- 95. Non System Tanks or Isolated Tanks or Rainfed Tanks The rain fed tanks are known as Non-System Tanks. Non System Tanks which command area below 40 hectares are coming under the control of Panchayat Unions. These Non-System Tanks have a small storage capacity.
- 96. Non System Tanks
- 97. 3. Grouped Tank or Tank in series • These tanks consists of a series of tanks connected together such that out flow from the upper tank is stored in the lower tank for irrigation. • These tanks either receives the surplus water of the upper tank or send its own surplus into some lower tank or do both. • When a tank neither receives the water from the upper tank nor discharges its own surplus into a lower tank is called as isolated tank.
- 99. Tank Irrigation • Irrigation tanks are classified based on size 1. Small tank • 4.5 m height and 20 hectares area 2. Medium tank • 9m height and 21 to 500 hectares area 3. Large tank • 12 m height and more than 500 hectares area • A tank irrigation system consist of 1. Earthern or Tank Bund for water storage 2. A Surplus Weir to dispose off flood discharge 3. Tank Outlets or Supply Sluices to feed the channels 4. Channels from the sluices to feed the irrigation area.
- 100. It is a small sized earth dam and its design and construction should be carried out in accordance with principles applicable to earth dams. The tank bunds may be of three types: I. Earthern or Tank Bunds for Water Storage: 1. Homogeneous Embankment type 2. Zone embankment type 3. Diaphragm type
- 101. 1. Homogeneous Embankment type
- 102. 2. Zone embankment type
- 104. 3. Diaphragm type
- 106. • Structure constructed to provide passage to excess water is called escape weir. It is also called tank surplus weir. The water starts spilling over the weir as soon as tank is filled upto its crest. • However, temporarily due to rush of incoming water the level in the tank rises above F.T.L. • The new level reached is called Maximum Water Level (M.W.L). It depends on the extent of flood. For design purposes M.W.L is calculated taking into account maximum flood discharge likely to occur • It is therefore necessary to make suitable arrangement to pass down excess water beyond Full Tank level (F.T.L.) safely. II. Tank Weir or Surplus Weir
- 109. III. Tank Sluice or Tank Outlet: For releasing stored water into irrigation channel, opening is provided in a tank bund. It is constructed in the form of a culvert or a pipe line. Since the opening extends from upstream face of the bund to the downstream face, wing walls and other types of bank connections are necessary at the head as well as tail of the opening. In small tanks, pipe outlets are constructed. For medium sized tanks masonry culverts are adopted.
- 110. i. Pipe Outlets: • Either cast iron pipes or cement or earthenware pipes are used to construct pipe outlets or pipe sluices. Since the size of pipes is small they are not open to inspection once they are put in place through the bund. • To avoid their bursting or leakage in pipes they are used in small tanks where depth of water stored in less than 2.5 metres approximately. • Any repair work in this type is possible only after bund is cut open.
- 116. ii. Culvert Type Sluice: In this type masonry culvert of minimum size 0.6 metres wide and 0.75 metres high is constructed either with or without arch roof. The size of the culvert depends upon the water to be conveyed. The minimum size of 0.6 × 0.75 m permits, manual inspection and repairs, and cleaning from inside.
- 118. Furrow method of irrigation is most suitable for a) potatoes b) rice c) wheat d) Cotton
- 119. The canal which is not supposed to do any irrigation is called a) main canal b) water course c) major distributary d) minor distributary
- 129. • Irrigation scheduling is the process used by irrigation system managers to determine the correct frequency and duration of watering. • Irrigation scheduling is the decision of when and how much water to apply to a field. • Its purpose is to maximize irrigation efficiencies by applying the exact amount of water needed to replenish the soil moisture to the desired level. • The importance of irrigation scheduling is that it enables the irrigator to apply the exact amount of water to achieve the goal. Irrigation scheduling
- 131. 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
- 132. The aim of irrigation scheduling is to apply the right amount of water, in the right place at the right time to achieve optimum yields.
- 133. Various methods and tools have been developed to determine when crops require water and how much irrigation water needs to be applied. Most commonly and currently use methods are (a) Water Balance Method (b) Soil Moisture measuring – Tensiometers and electrical resistance meters Irrigation Scheduling Methods
- 134. Swi + P + Irr = Swf + R + DP + ET Swi – Swf = R + DP + ET - P - Irr (a)Water Balance Method
- 135. (b) Soil Moisture measuring
- 137. (b) Soil Moisture measuring
- 142. Water distribution in irrigation systems The irrigation system consists of a (main) intake structure or (main) pumping station, a conveyance system, a distribution system, a field application system, and a drainage system.
- 144. Methods of Water distribution in canal irrigation systems • Rational water distribution system or Warabandi • Intermittent flow • Continuous flow • Demand based
- 151. BORDER IRRIGATION
- 152. 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.
- 153. 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
- 154. 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
- 155. Efficiency of Water-conveyance (ηc) 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 ηc. It takes the conveyance or transit losses into consideration. ηc = (Wf/Wr) X 100 Where ηc= Water conveyance efficiency, Wf = Water delivered to the irrigated plot at field supply Channel, Wr = Water diverted from the source ( river or reservoir )
- 156. Efficiency of Water Application (ηa) It is ratio of water stored into the root zone of the crop to the quantity of water delivered at the field (Farm). ηa =Ws/Wf X 100 Where, ηa = Water application efficiency, Ws = Water stored at the root zone during the irrigation Wf = Water delivered to the farm.
- 157. Efficiency of Water Use (ηu) It is the ratio of the water beneficially used including leaching water, to the Quantity of water delivered. It may be represented by ηu ηu = (Wu/Wd) X 100 Where, ηu = Water use efficiency, Wu = Beneficial use of water or consumptive. Wa = Water delivered to the field.
- 158. Efficiency of water storage: (ηs) The concept of water storage efficiency gives an insight to how completely the required water has been stored in the root zone during irrigation. ηs = (Ws/Wn )X 100 Where, ηs= Water storage efficiency, Ws = water stored in the root zone during irrigation. Wn = Water need in the root zone prior to irrigation.
- 159. Water Distribution Efficiency (ηd) 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. ηd =100 (1-y/d) Where, ηd= 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.
- 160. Consumptive use Efficiency (ηcu) It is the ratio of consumptive use of water to the water depleted from the root zone. ηcu = (Wcu/Wd)X 100 Where, ηcu= Consumptive use efficiency, Wcu= Nominal consumptive use of water Wd = Net amount of water depleted from the root zone soil.
- 161. Discussions ?