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Water Resources Engineering (CVE 728)--Slide 7.pptx
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- 2. Irrigation Irrigation is theagricultural process of applying controlled amounts of water to land to assist in the production of crops, as well as to grow landscape plants and lawns.
- 3. Irrigation Systems The mostcommon irrigation systems are listed below. Surface irrigation Sprinkler irrigation Drip irrigation Subsurface drip Irrigation
- 4. 1. Surface irrigation Thethree most common methods of surface irrigation are: i. Basin irrigation ii. Border irrigation iii. Furrow irrigation
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- 8. Applicability, advantages anddisadvantages of surface irrigation Applicability This system depends on three factors: 1. type of soil 2. water quality and climate 3. plant and labours
- 9. Applicability, advantages anddisadvantages of surface irrigation Cont. Advantages • Because it is so widely utilized, local irrigators generally have at least minimal understanding of how to operate and maintain the system • Surface irrigation systems can be developed at the farm level with minimal capital investment • The essential structural elements are located at the edges of the fields, which facilitates operation and maintenance activities • If the topography is not too undulating, these costs are not great • Energy requirements for surface irrigation systems come from gravity • Surface irrigation systems are less affected by climatic and water quality characteristics • The gravity flow system is a highly flexible, relatively easily managed method of irrigation
- 10. Applicability, advantages anddisadvantages of surface irrigation Cont. Disadvantages • The soil, which must be used to convey the water over the field, has properties that are highly varied both spatially and temporally • Surface irrigation systems are typically less efficient in applying water than either sprinkler or trickle systems • The need to use the field surface as a conveyance and distribution facility requires that fields be well graded if possible • Surface systems tend to be labour-intensive
- 11. 2. SPRINKLER IRRIGATION Sprinklerirrigation method, is the type of irrigation in which water is sprayed into the air and allowed to fall on the ground surface somewhat resembling rainfall. The spray is generated by the pressured flow of water through small orifices or nozzles. The pressure is usually obtained by pumping.
- 12. 2. SPRINKLER IRRIGATIONCont. The most common sprinkler irrigation methods are: i. Centre pivot ii. Linear move iii. Travelling big gun iv. Side roll
- 13. SPRINKLER IRRIGATION Cont. Whenselecting a sprinkler system, the most important physical parameters to consider are: • The shape and size of the field. • The topography of the field. • The amount of time and labor required to operate the system.
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- 18. Applicability, advantages anddisadvantages of Sprinkler irrigation Applicability This system depends on three factors: 1. type of soil 2. water quality and climate 3. plant and labours
- 19. Applicability, advantages anddisadvantages of Sprinkler irrigation Cont. Advantage • No terracing required • Suitable to all types of soil except heavy clay • Suitable for irrigating crops where the plant population per unit area is very high • Influences greater conducive micro-climate • Areas located at a higher elevation than the source can be irrigated • Possibility of using soluble fertilizers and chemicals
- 20. Applicability, advantages anddisadvantages of sprinkler irrigation Cont. Disadvantages • Incurs high operation expenses due to the energy needed for pumping, labour and relatively large investment in equipment: sprinklers and pipes • Sensitivity to wind, causing evaporation losses • The unavoidable wetting of foliage in field crops results in increased sensitivity to diseases • Debris and sediments can cause clogging • Capital cost is high with greater operational costs due to higher energy requirements
- 21. 3. DRIP IRRIGATION Dripirrigation is a technique in which water flows through a filter into special drip pipes, with emitters located at different spacing. Water is distributed through the emitters directly into the soil near the roots through a special slow-release device (dripper).
- 22. 3. DRIP IRRIGATIONCont.
- 23. Applicability, advantages anddisadvantages of Drip irrigation Applicability • Generally, drip irrigation is especially good for arid and drought prone areas. Drip and subsurface drip irrigation is used almost exclusively when using recycled municipal wastewater.
- 24. Applicability, advantages anddisadvantages of Drip irrigation Cont. Advantages • High water application efficiency and lower labor costs • Minimized fertilizer/nutrient loss due to localized application and reduced leaching • Ability to irrigate irregular shaped fields. Leveling of the field is not necessary • Allows safe use of recycled (waste-) water • Moisture within the root zone can be maintained at field capacity and minimized soil erosion • Soil type plays less important role in frequency of irrigation • Highly uniform distribution of water i.e., controlled by output of each nozzle • Usually operated at lower pressure than other types of pressurized irrigation, reducing energy costs
- 25. Applicability, advantages anddisadvantages of Drip irrigation Cont. Disadvantages • Expensive initial cost • The sun can affect the tubes used for drip irrigation, shortening their usable life • If the water is not properly filtered and the equipment not properly maintained, it can result in clogging • Drip irrigation might be unsatisfactory if herbicides or top dressed fertilizers need sprinkler irrigation for activation • Waste of water, time & harvest, if not installed properly • Systems require careful study of all the relevant factors like land topography, soil, water, crop and agro-climatic conditions, and suitability of drip irrigation system and its components • Salts applied with the irrigation water may build up in the root zone.
- 26. 4. SUBSURFACE DRIPIRRIGATION Subsurface drip irrigation is a highly efficient, low-pressure irrigation system that uses buried drip tubes or drip tape to meet crop water needs.
- 27. 4. SUBSURFACE DRIPIRRIGATION Cont.
- 28. Applicability, advantages anddisadvantages of Subsurface Drip irrigation Applicability • Subsurface drip irrigation systems are highly efficient irrigation systems that apply accurate amounts of water directly to the root zone, preventing water loss through evaporation and other negative effects of surface irrigation. • This is especially suitable for arid, semi-arid, hot, and windy areas with limited water supply.
- 29. Applicability, advantages anddisadvantages of Subsurface Drip irrigation Cont. Advantages • High degree of control over water application with the potential for high uniformity of application • Evaporation is reduced • The amount of water can be fine-tuned. This avoids water loss caused by run off or evaporation • Frequent irrigation allows for optimum soil moisture content in the root zone • Great performance in windy and arid locations • If pre-treated wastewater is used for irrigation, the risk of direct contact with crops and laborers is reduced
- 30. Applicability, advantages anddisadvantages of Subsurface Drip irrigation Cont. Disadvantages • Risk of clogging • When saline water is used, salts accumulate at the wetting front • Emitter can be damaged or blocked by root hairs • Bacterial slimes and algae growing on the interior walls of the laterals and emitters combined with clay particles in the water can block the emitters • Suspended organic matter and clay particles can damage the system • A lot of repair work is caused by rodents chewing the tubes • Heavy machinery can damage the laterals