Agriculture:- Model Bankable Projects in India | Minor Irrigation : Sprinkler Irrigation Systems Chapter 3 --- www.nabard.org
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Scheme Requirements
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3.0 Scheme formulation for adopting of sprinkler irrigation system with bank loans requires appropriate technical and financial details. Some of the most important points that should be included in a scheme are briefly given below:
3.1 TECHNICAL ASPECTS 3.1.1 Map of the area: It is important that a map/ sketch of the area is prepared with sufficient accuracy to show all dimensions and showing all relevant elevations with respect to water supply, pump location, and critical elevations in the field to be irrigated. 3.1.2 Type of crops: Type of crops to be grown in the field concerned must be indicated since consumptive use of water, effective root zone depth, evapo-transpiration, etc. differ from crop to crop. Other than Rice and Jute which require large amounts of water, sprinkler irrigation system is adaptable to all crops. It is ideally suited to crops with restricted root systems such as lettuce, sugar-beet, potato which require light and frequent application of water with close control over moisture level. Sprinklers are also successful in wheat, sugarcane, cotton, vegetables, citrus, lucerne and other fodder crops. Extremely heavy soils with low intake rates cannot be effectively irrigated through sprinklers, especially in hot and windy climates. The sprinkler system should be designed accordingly. 3.1.3 Soil: The water holding capacity of soils is different for different soils. Thus, type of soil determines the type of sprinkler, irrigation schedule, size and type of equipments, etc. The general nature of the soil and its characteristics should be given in the scheme. Design of Sprinkler system also depends upon the infiltration rate of soil. It is, therefore, essential to have a fair idea about the characteristics of various soils. Table -2: Infiltration Rate of Some soils | ||||||||||||||||||||||||
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3.1.4 Available water:
Soil moisture between field capacity and permanent wilting point is the available water. Different soils have different water holding capacities. Table -3 : Range of available water holding capacity of soils. | ||||||||||||||||||||||||
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3.1.5 Climate :
Climatic conditions like temperature, humidity, wind velocity of a place has great influence on the consumptive use of a crop. Sprinkler system should be designed for the peak rate of consumptive use of crops to be irrigated by it. In areas where wind velocities and temperatures are high, heavy evaporation losses from the sprinkler sprays significantly reduces the saving of water. The wind also influences the spacing of sprinklers. Therefore, it is essential to know the velocity of wind and its direction. For wind velocities over 16 km/hour, sprinkler system becomes unsuitable. Table-4 : Sprinkler overlap under different wind conditions | ||||||||||||||||||||||||
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3.1.6 Depth of irrigation:
On the basis of available moisture holding capacity of the soil in its different layers and soil moisture extraction pattern of the crop in its root zone depth, the depth of irrigation may be calculated. 3.1.7 Irrigation interval : It is the length of time allowed between successive irrigations during peak consumptive use of the crops. It can be calculated from the available moisture for the soil-crop system and the rate of consumptive use of the crop. 3.1.8 Well Capacity: The source of water should be indicated. If the source of water is a groundwater structure, the diameter, depth and well yield together with HP of the pump set already installed may be given. This is necessary to decide the discharge available from the well and its optimum utilisation.In case the existing pump is not sufficient, a booster pump may have to be provided to create adequate pressure for proper functioning of the sprinkler system. 3.1.9 Water quality: Surface irrigation methods are more suitable in the cases where irrigation water contains heavy silt concentration along with substantial salt solution. Otherwise, nozzle may be damaged by coarse silt. Presence of salt solution beyond a limit makes sprinkler unsuitable. 3.2 FINANCIAL ASPECTS 3.2.1 Unit Cost : The unit cost of sprinkler irrigation system includes the cost of all components required for the system and depends upon location of the well, type of sprinkler, discharge, land holding, cropping pattern, topography and the total head. Banks must finance considering the actual costs required for the sprinkler system. 3.2.2 Time and labour required to operate the system: The adoption of sprinkler irrigation system reduces the amount of time and labour required by manifolds. Unlike the conventional method of irrigation, it does not require continuous supervision during irrigating the field. 3.2.3 Costs and benefits: Sprinkler entails high initial cost in comparison to surface irrigation methods. However, factors such as optimum water use from a limited water supply source (leading to higher cropping intensity), achievement of significant saving of financial resources by obviating the necessity of land leveling and other labour costs, besides increased productivity /yield of crops - tend to tilt the case in favour of sprinkler system. These aspects may be quantified and indicated in the scheme. 3.2.4 Economics: The economics of investment should be given in detail. The scheme should also give details about repayment scheduling, rate of interest, subsidy available etc. |
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