Chapter -4.1 surface Irrigation systems.pptx

surface irrigation systems and methods of irrigation inluding basine irrigation,border irrigartion,and furrow irrigation.there are alos presurizez irrigation systems such as drip irrigation and sprinler irrigation

1. CHAPTER Four : IRRIGATION APPLICATION METHODS Irrigation Application Methods Surface Irrigation Pressurized Irrigation Basin Irrigation Furrow Irrigation Border Irrigation Trickle Irrigation Sprinkler Irrigation

2. surface irrigation Definition Surface irrigation has evolved into an extensive array of configurations which can be broadly classified as: (1) basin irrigation; (2) border irrigation; (3) furrow irrigation; Introduction con

3. Introduction cont… There are two features that distinguish a surface irrigation system: (a) the flow has a free surface responding to the gravitational gradient ; (b) the on-field means of conveyance and distribution is the field surface itself.

4. General characteristics of Surface Irrigation: Old-age method the most extensively used method worldwide water application is directly on the soil surface Requires relatively minimal capital investment doesn’t require complicated and expensive equipment Energy costs are substantially lower

5. Labor requirements is relatively high Relatively inefficient method Limited to land already having small and even slopes entirely practiced where water is abundant. More affected by water logging and salinity problems Land leveling costs are high

6. Good Surface Irrigation practice: distribution of water evenly in the soil, adequate water supply for the crops and avoidance of undue water wastage Water movement problem in surface irrigation: Uneven water distribution (not uniform): due to contact time difference between the head and tail end of the field. Percolation loss : due to large contact time or greater infiltration near the head of the field. Runoff loss : due to continuous supply of water after the water has reached the tail end of the field.

7. Furrow Irrigation Definition: Furrow irrigation is the most widely used method worldwide for irrigating row crops. In furrow irrigation, water no longer flows over the entire soil surface but is confined to small channels (furrows) between the crop rows. It is then gradually absorbed into the bottom and sides of the furrow to wet the soil. Furrow irrigation avoids flooding the entire field surface by channelling the flow along the primary direction of the field Water infiltrates through the wetted perimeter and spreads vertically and horizontally to refill the soil reservoir.

8. Furrow Irrigation cont… Furrows provide better on-farm water management flexibility under many surface irrigation conditions. The discharge per unit width of the field is substantially reduced and topographical variations can be more severe. A smaller wetted area reduces evaporation losses. Furrows provide the irrigator more opportunity to manage irrigations toward higher efficiencies as field conditions change for each irrigation throughout a season. This is not to say, however, that furrow irrigation enjoys higher application efficiencies than borders and basins.

9. Furrow Irrigation cont… There are several disadvantages with furrow irrigation. These may include: an accumulation of salinity between furrows; the difficulty of moving farm equipment across the furrows; the added expense and time to make extra tillage practice (furrow construction); an increase in the erosive potential of the flow; a higher commitment of labor to operate efficiently; and generally furrow systems are more difficult to automate, particularly with regard to regulating an equal discharge in each furrow.

10. Furrow irrigation Shape of furrow: Furrows are usually V-shaped, parabolic etc. Width of furrow: 250-400mm Depth of furrow: 150 – 300mm.

11. Fig.1 Typical Furrow Irrigation System

12. Figure 7: Short and long furrow at farmer’s field

13. T here are different ways of applying water to the furrow from the head ditch. Using Siphons by cutting the ridge or levee separating the head ditch and the furrows Using spill (short pipes) buried in the ridge

14. Fig. 2 Furrow Irrigation by Cutting the Ridge

15. Fig.3 Furrow Irrigation by Siphons

16. Furrow Spacing : depends on Water movement in the soil E.g. close furrows on sandy soils Crop E.g. double rows for onions Cultivation Practice E.g. equipments used for cultivation and harvesting Furrow length: It depends on soil type, stream size, irrigation depth, field size and shape, slope, farming practice.

17. But generally, Furrows can usually be longer on clay soils than on sandy soils. Furrows can be longer when a larger stream size is used for irrigation. Furrows can be longer when a larger irrigation depth is applied. Furrows are usually shorter on steeper sloping land to prevent erosion. Furrow Slope: Ideally furrows should have a uniform slope. A minimum slope of 0.05% is needed to ensure that water will flow down the furrow and any excess water can be drained. The maximum slope depends on the risk of soil erosion.

18. Crops: Most row crops such as vegetables, cotton, sugar beet and potatoes The crops are usually planted on raised bed or ridges Irrigating furrows: When irrigating furrows, water is supplied to each furrow from the farm channel using siphons or spills. Several furrows can be irrigated at the same time depending up on the discharge available in the farm channel. The stream size must be large enough for the flow to advance quickly down the furrow. Runoff can be a major problem in furrow irrigation.

19. Common faults in furrow irrigation: a) Poor land preparation Uneven slope and low areas in a field can result in poor water distribution and water logging. b) Different soil types along furrow It is very similar to that for basins and borders. If the soil varies in texture along the furrow, water distribution will be very uneven. c) Advance time too long This is usually the result of using a stream size which is too small, long furrow, sandy soils. d) Stopping inflow too soon If the stream is cut off too soon, it results in a poor distribution of water, and plants at the end of furrows do not get enough water. Irrigation Efficiency On well managed furrows, the irrigation efficiency can be as high as 90%.

20. Border Irrigation Definition: Here, the land is divided into strips (border) by parallel small earth bunds called border ridges. In a border irrigation, each strip is irrigated separately by introducing water upstream and it progressively covers the entire strip. Water is applied to individual borders from small hand-dug checks from the field head ditch. When the water is shut off, it recedes from the upper end to the lower end.

21. Border Irrigation cont… Borders are different from basins into two important differences: Borders slope uniformly away from the farm channel. A uniform distribution of water is obtained by using a small stream size. Size and shape of Borders: Borders are often long and narrow They are usually rectangular in shape varying in size from 100 – 800m long and 3 – 30m wide.

22. Border Irrigation System

23. Border Irrigation cont…

24. Border cont… Size and shape of borders depends on soil type, stream size, irrigation depth, slope, field size. Generally , Borders are much longer on clay soils than on sandy soils. Borders are longer when a larger unit stream size is available. Borders are longer when a larger irrigation depth is applied. Borders must be shorter on steeper sloping land to prevent erosion. Borders can be wider when larger stream sizes are available.

25. Crop: Sloping borders are suitable for nearly any crop except those that require prolonged ponding . Border irrigation is suited for crops that can withstand flooding for a short time e.g. wheat. It can be used for all crops provided that the system is designed to provide the needed water control for irrigation of crops. Soil : Soils can be efficiently irrigated which have moderately low to moderately high intake rates but, as with basins, should not form dense crusts unless provisions are made to furrow or construct raised borders for the crops.

26. Border Irrigation cont… It is suited to soils between extremely high and very low infiltration rates. Land Slope : Ideally, borders should have a uniform slope along the length and no cross slope. The precision of the field topography is also critical, but the extended lengths permit better leveling through the use of farm machinery.

27. The minimum slope along the length of border is usually 0.1% to ensure water flow down the border . The maximum slope depends on the risk of soil erosion Irrigating borders : When irrigating borders, it is important to use the right unit stream size for the soil and land slope, and to stop the flow at the right time . The stream size per unit width must be large, particularly following a major tillage operation, although not so large for basins owing to the effects of slope.

28. Common Faults in Border Irrigation Practice: i ) Poor land preparation When a border slopes unevenly, the flow down the border is also uneven. ii) Different soil types along border The effect is very similar to that in basins. Water distribution can be very uneven. iii) Using wrong stream size Too much water application usually means that the stream size is too small. And, it results in high percolation loss. Too little water application usually means that the stream size is too large. And, it results in high runoff loss.

29. iv) Fixed irrigation schedule Although the right stream size is used, some irrigators choose the irrigation time to fit with other farm work rather than on the irrigation needed. v) Irrigation Efficiency On well managed borders the irrigation efficiency can be as high as 80%.

30. Basin Irrigation Definition: It is the simplest of all methods of irrigation . It involves dividing the field into a number of small strips of land called basins. Each basin is a level area of land surrounded by earth bunds in which water can be pounded until it infiltrates in to the soil. If a field is level in all directions, is encompassed by a dyke to prevent runoff, and provides an undirected flow of water onto the field, it is herein called a basin. A basin is typically square in shape but exists in all sorts of irregular and rectangular configurations.

31. Basin Irrigation cont… Size of Basins: It depends on soil type, stream size, irrigation depth, field size, etc. But generally, Basins are much larger on clay soils than on sandy Basins can be larger when a large stream size is used. Basins can be larger when a larger irrigation depth is used,

32. Basin Irrigation cont… There are few crops and soils not amenable to basin irrigation, but it is generally favored by moderate to slow intake soils, deep-rooted and closely spaced crops. Crops which are sensitive to flooding and soils which form a hard crust following an irrigation can be basin irrigated by adding furrowing or using raised bed planting. Reclamation of salt-affected soils is easily accomplished with basin irrigation and provision for drainage of surface runoff is unnecessary. It is always possible to encounter a heavy rainfall or mistake the cut-off time thereby having too much water in the basin. Consequently, some means of emergency surface drainage is good design practice.

33. Basin Irrigation cont… Basins can be served with less command area and field watercourses than can border and furrow systems because their level nature allows water applications from anywhere along the basin perimeter. Automation is easily applied.

34. Figure 5: Basin method of irrigation

35. Land slope for basin : The soil surface within each basin must be level. On sloping and undulating ground the land surface must be re-shaped into level areas. Crops grown : Rice is the most common crop irrigated by basin. Other crops: alfalfa, maize, ground-nut, fruits Irrigating basins: When irrigating basins, the stream size must be large enough for the flow to advance rapidly across the basins. This will ensure a reasonably uniform irrigation. A practical guide line to irrigate basin is to use a stream size large enough for the flow to reach the far end in one quarter of the contact time. This is called the quarter time rule.

36. Common Faults in Basin Irrigation Practice: i ) Poor land preparation When a basin is constructed on sloping ground and the land is not leveled, too much water at the lower end. If a basin is constructed on reasonably level ground but the land has not been leveled properly, more water on the lower spots and less water at the higher. ii) Basins covering more than one soil type Variations in soil type within a basin can result in water infiltrating much faster in one place than in another. iii) Irrigation efficiency On well managed basins irrigation efficiency can be as high as 90%.

37. Limitations Soil crusting Not suited to crops that cannot accommodate inundation. Precision land leveling is very important to achieve high uniformities and efficiencies. Many basins are so small that precision equipment cannot work effectively. The perimeter dykes need to be well maintained to eliminate breaching and waste, and must be higher for basins than other surface irrigation methods.

38. Limitations cont… To reach maximum levels of efficiency, the flow per unit width must be as high as possible without causing erosion of the soil. When an irrigation project has been designed for either small basins or furrows and borders, the capacity of control and outlet structures may not be large enough to improve basins.

39. The three typical cases of surface irrigation practices are: A) the inflow is cutoff shortly after completion of the advance phase and application inadequate at some point in the field. B) the least watered area just receives the required depths C) the applied depths exceed the requirement at all locations (the usual case) Three typical cases of surface irrigation practice: