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IRRIGATION ENGINEERING
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- 2. IRRIGATION It may bedefined as the process of artificially supplying water to soil for raising crops.
- 3. NECESSITY OF IRRIGATION •Less rainfall • Non-uniform rainfall • Growing a number of crops during a year • Growing perennial crops • Commercial crops with additional water • Controlled water supply
- 4. Advantage of irrigation • Itcan significantly increase crop yields, improve crop quality, and enhance agricultural productivity. • It allows farmers to control the timing, frequency, and amount of water applied to crops, which can optimize plant growth and development. • It can support the cultivation of a wide range of crops, including those that require large amounts of water, such as rice and sugarcane. • It washes out or dilutes salts in the soil
- 5. ILL-EFFECTS OF IRRIGATION • Breedingplaces for mosquitoes • Water logging • Damp climate
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- 7. FLOW IRRIGATION • Wateris allowed to flow over the soil surface and soak into the ground by gravity. This type of irrigation is also known as surface irrigation.
- 8. PERENNIAL IRRIGATION • It isa type of irrigation system that provides a continuous and reliable water supply to crops throughout the year, regardless of the season or weather conditions. • In this system some storage head works, such as dams and storage weirs or barrages are required to store the excess water during floods and release it to crop as and when it is required
- 9. INUNDATION IRRIGATION • It iscarried out by deep flooding and thoroughsaturationof the land to be cultivatedwhich is then drained off prior to the planting of the crop
- 10. FLOW IRRIGATION • Dependingupon the source from which the water is drawn flow irrigation can be further subdivided into three types: • Direct irrigation (River canal irrigation) • Storage irrigation (storage scheme) • Combined storage and diversion scheme
- 11. DIRECT IRRIGATION • The wateris directly diverted to the canal without attempting to store the water. • For such a system, a low diversion weir or diversion barrage is constructed across the river • This raises the water level in the river and thus diverts the water to the canal taking off upstream of the weir • It is a smaller magnitude compared to other
- 13. STORAGE IRRIGATION • Asolid barrier such as a dam or a storage weir is constructedacross the river and water is stored in the reservoir or lake so formed. • Depending upon the following the storagevolume is decided • Water requirement of crops • Hydroelectricity power generation • Flow of water in the river • It is comparatively of a bigger magnitude and involves much more expenditure than a direct irrigation scheme
- 15. COMBINED SYSTEM • Inthis system a combined scheme is adopted in which the water is first stored in the reservoir formed at the upstream side of the dam and this water is used for water power generation • After that the water is flows in down-stream of the dam again the water is diverted by constructing a weir or barrage
- 17. LIFT IRRIGATION • Thewater supply is at too low a level to run by gravitation on to the land • In such circumstances water is lifted up by mechanical means • Irrigation from wells is an example of lift irrigation, in which sub-soil water is lifted up to the surface and is then conveyed to the agricultural fields
- 18. METHODS OF APPLICATIONOF IRRIGATIONWATER
- 19. WILD FLOODING • Wateris spread or flooded on a rather smooth flat land, without much control or prior preparation • This method is generally used in the inundation irrigation system in which water is forced to spread over vast tracts during the season of high stream flow • It is wasteful use of water • It is practiced largely where irrigation water is abundant and inexpensive
- 20. FREE FLOODING • Itis a controlled floodingirrigation method • Water is spread over the land,with proper methods to control the depth ofapplication • It consists of dividingthe entire land to be irrigated into small strips bya number of field channels known as laterals • It will construct right angles to the sides of the field or right angles to the contour lines • And provides supplychannel to supply water for irrigation and waste channels situated for collectingexcess waste from the laterals • Use for flat/steep lands.
- 22. FLOODING BY CONTOURLATERALS • This is a special case of free flooding in which the field channels or laterals are aligned approximately along the contour lines • It is applicable for steeper terrain
- 24. BORDER STRIPS FLOODING • Thefarm is divided into a series of strips 10 to 20m wide and 100 to 300m long • These strips are separated by low levees or borders and run down the predominant or any other desired slope
- 26. CHECK FLOODING • Itsimilar to free flooding except that the water is controlled by surrounding the check area with low, flat levees surrounding each check while in free flooding no such levees are provided and strips are divided by field channels • It is the mostcommon method used in India • The method is also known as irrigation by plots since the entire area is divided into several plots obtained by subdividing the entire area by levees
- 28. ZIG-ZAG METHOD OF FLOODING •It is special method of flooding where water takes circuitous route before reaching the dead end of each plot • The whole area is divided into a number of square or rectangular plots; each plot is then subdivided with the help of low bunds or levees • It is suitablefor level plots • It is highly unsuitable for farming operations with modern farm machinery
- 30. FURROW METHOD • It isused for row crops like maize, jowar, sugarcane, cotton, tobacco, groundnut, potatoes etc. • A furrow consists of a narrow ditch between rows of plants • Commonly the length of furrow is adopt 100 to 200 m
- 32. CONTOUR FARMING • Contour farmingis a soil conservation technique that involves cultivating crops along the contours of the land. • The primary objective of contour farming is to reduce soil erosion by slowing down the flow of water across the land. • Contour farming helps in conserving soil fertility, retaining moisture, and minimizing water runoff.
- 33. SUB-SURFACE IRRIGATION • Itconsists of supplying water directly to the root zone of the crop. • Following are the favorable conditions for the sub-surface irrigation • Existence of high water table • Permeable soil such as loam or sandy loam in the root zone of the soil • Uniform topographic conditions • Moderate slopes • Good quality irrigation water • It may be of two classes: • Natural sub-irrigation • Artificial sub-irrigation
- 34. NATURAL SUB-IRRIGATION • Wateris suppliedto the root zone of the plantsby controllingthe level of localwater table • Such a high level of water table in the area may be available due to water seeping from earthen canals, drains, rivers etc. • In order to maintain the ensure the requisite supply of water to the root zone it is essential to maintain the desired water level by artificial means.
- 35. ARTIFICIAL SUB- IRRIGATION • Supplyingwater directly to the root zone of crops through a network of buried perforated pipes • Water is made to pass under pressure, through these underground perforated pipes • It suitable only for the conditions of high horizontal permeability and low vertical permeability so that percolation losses are minimized • The pipes are buried 0.3 to 0.4 m deep and spaced 0.4 to 0.5 m horizontally for uniform distribution of water
- 36. SPRINKLER IRRIGATION • Itconsists ofapplying the water in the formof a spray • This method is moreusefulwhere: • The land cannotbe prepared for surfacemethods • Slopes are excessive • Topography is irregular • Soil is erosive • Soil is excessively permeable or impermeable • The cost of land preparation is less but initial investmentis high in the purchase of the appurtenances
- 37. TYPES OF SPRINKLERS • Fixednozzle pipe system • Perforated pipe system • Rotating sprinklers system
- 38. DRIP IRRIGATION • Itis also known as trickle irrigation, water is applied in the form of drops directly near the base of the plant • This technique also known as feeding bottle technique where by the soil is maintained in the most congenital form by keeping the soil water air proportions in the optimum range • It is firstly introduced by Israel • This type of irrigation is suitable for vegetable crops such as tomatoes, peppers, cucumbers, lettuce, and carrots, field crops like corn, soybeans, wheat, and cotton.
- 39. Arrangement for Dripirrigationsystem
- 40. Advantages of drip irrigation •Less requirement of irrigation water • Water supply at optimum level • Water logging avoided • High yield • Cultivation of cash crops • No soil erosion • Suitable for any topography
- 41. QUALITY OF IRRIGATIONWATER • pH Level: Impact on nutrient availability and plant growth • Salinity: Effects on water uptake and crop yield • Total Dissolved Solids (TDS): Influence on crop growth and quality • Specific Ion Concentrations: Impact on soil and plant health • Toxic Elements: Risks to plant growth and human health • Organic Contaminants:Effects and safety compliance • Microbial Contamination: Risks, testing, and mitigation • Water Availability: Impact on salt concentration and contaminants • Water Sources: Evaluation of water quality based on source • Water Treatment and Management: Techniques for improving water quality
- 42. CLASSIFICATION OF IRRIGATIONWATER • Classification based on total concentration of soluble salts • Classification based on sodium concentration • Classification based on electrical conductivity (EC), total salt content (TDS), sodium concentration (ESP), boron concentration etc.
- 43. CLASSIFICATION BASED ONTOTAL CONCENTRATION OF SOLUBLE SALTS • Irrigation watermay containvarioustypes of salts such as sodium, calcium, magnesium and potassium etc. • Those salts may prove to be injuriousto the crops • Excess quantityof these salts reduce the osmotic activity of the plants, thus preventingthe absorptionof nutrientsfrom the soil • It is expressed in • parts per million (ppm) or milligram per liter (mg/l) • Milli equivalents per liter (meq/l) • Electrical conductivity (mS/cm or micro-mhos/cm) • The salinityconcentrationof soil solution(Cs) C = conc. of salts in irrigationwater Q = totalquantityof water appliedto the soil Cu = consumptive use of water Peff = useful rainfall
- 45. CLASSIFICATION BASED ONSODIUM CONCENTRATION • If the % of sodium is more, the aggregation of soil grains break down and the soil becomes less permeable • Even on sandy soils, water of 85% sodium or higher are likely to make soil impermeable after prolonged use • Constant irrigation with high sodium water, the soil becomes plastic and sticky when wet and forms clods and crust on drying • Irrigation water is classified on sodium concentration on the basis of a factor called sodium absorption ratio (SAR)
- 47. CLASSIFICATION BASED ONELECTRICAL CONDUCTIVITY (EC), TOTAL SALT CONTENT (TDS), SODIUM CONCENTRATION (ESP), BORON CONCENTRATION ETC. • Class 1 water are considered to be excellent for most of the plants. • Class 2 waters are considered as good to injurious, probably harmful to more sensitive crops • Class 3 waters are considered unsuitable under most conditions
- 48. BASE PERIOD • Itis the time elapsed between first watering and last watering to a given field of irrigation
- 49. Crop period • Itis the time elapsed between the instant of sowing and the instant of harvesting
- 50. DUTY • Duty ofwater is defined as area of land irrigated per unit discharge of water • For example: if 1000 ha of land can be irrigated for growing any crop by supplying 1 cumec of water continuously for the entire base period of the crop then duty of water for this crop is said to be 1000 ha/cumec A = area in ha Q = discharge in cumec D = duty in ha/cumec
- 51. DELTA • It isthe total depth of water required by a crop to be supplied during its base period to come to maturity. • This Δ water will be supplied with proper distribution over the base period of crop depending upon crop requirements.
- 52. DUTY AT VARIOUS PLACES •Duty of water varies from place to place, because of continuous conveyance losses as the water flow; it is minimum at source and maximum at the utilization point (field) • At the head of main canal --- known as Gross quantity • At the head of branch canal --- known as Lateral quantity • At the outlet of a canal --- known as outlet factor • At the head of land to be irrigated ---- known as Net quantity
- 54. UNITS OF VOLUMEOF IRRIGATION WATER • ha-m = 10,000 m2 x 1 m = 10,000 m3 • Cumec-day = 1m3/s x 1 day = 1m3/s x 86400 s = 86400 m3 1 Cumec-day = 8.64 ha-m
- 55. RELATION BETWEEN DUTYAND DELTA Consider an irrigation field of area D hectares, with water application for a depth of Δ meter volume of water delivered to the total field = DΔ ha-m = DΔ x 104 m3 ----(1) This water volume is nothing but supply of water to the field at the rate of 1 cumec for a period of B days. ie = 1 (B) cumec-days = 1 x B x 24 x 60 x 60 m3 ----- (2) From equation (1) and (2) D(Δ ) 104 = B x 24 x 60 x 60 D = duty in hectares/cumec Δ = total depth of water supplied (in m) B = baseperiod in days
- 56. FACTORS AFFECTING DUTY • Methodsofirrigation • Mode of applyingwater to the crops • Method of cultivation • Time and frequency of tilling • Type of the crop • Base period of the crop • Climaticconditionsof the area • Quality of water • Method of assessment of irrigationmethod • Canalconditions • Characterof soil and sub-soil of the canal • Characterof soil and sub-soil of the irrigationfields
- 57. METHODS OF IMPROVING DUTY •The land should be properly ploughed and levelled before sowing the crops • Suitablemethod of applicationof water to the crops • Lined canalsmust be used • Rotationof crops must be practiced • Volumetric method of assessment must be used • Farmers must be given proper training so that moisture contentof the field should not exceed field capacity • Canalalignment should be in sandy soil • Frequent cultivationof the land must be adopted
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