1. 1 Part B3: Irrigation B3.1 Irrigation techniques

2. 2 B3.2Irrigation techniques Topics Surface irrigation –Basin irrigation, border irrigation, furrow irrigation Rainwater harvesting –Bunds, microcatchments, “Modern” irrigation techniques –Spray irrigation, micro irrigation

3. 3 B3.2.1Irrigation techniques Surface irrigation: Flow

4. 4

5. 5 B3.2.1Irrigation techniques Surface irrigation: Inlet arrangements

6. 6

7. 7

8. 8 T f = Time to reach the opposite end of the field (hr) T a = Application time (hr) B3.1.4Fundamentals of irrigation Surface irrigation: The quarter time rule

9. 9 B3.2.1Irrigation techniques Surface irrigation: Basin irrigation

10. 10 B3.2.1Irrigation techniques Surface irrigation: Flow

11. 11 B3.2.1Irrigation techniques Surface irrigation: Basin irrigation

12. 12 B3.2.1Irrigation techniques Surface irrigation: Basin irrigation: Scaling

13. 13 B3.1.4Fundamentals of irrigation Surface irrigation: Basin irrigation: Scaling Stream size (l/s)SandSandy loam Clay loamClay 150.010.030.060.10 300.020.060.120.20 600.040.120.240.40 900.060.180.360.60 1200.080.240.480.80 1500.100.300.601.00 1800.120.360.721.20 2100.140.420.841.40 2400.160.480.961.60

14. 14 B3.2.1Irrigation techniques Surface irrigation: Basin irrigation: Problems

15. 15 B3.2.1Irrigation techniques Surface irrigation: Basin irrigation: Terracing

16. 16 B3.2.1Irrigation techniques Surface irrigation: Border irrigation

17. 17 B3.2.1Irrigation techniques Surface irrigation: Border irrigation

18. 18 B3.2.1Irrigation techniques Surface irrigation: Border irrigation

19. 19 B3.2.1Irrigation techniques Surface irrigation: Border irrigation: Scaling

20. 20 B3.2.1Irrigation techniques Surface irrigation: Border irrigation: Scaling Soil typeIrrigation depth (mm) Slope (%) Width (m) Length (m) Unit stream (l/s/m) Sand1000.212-3060-10010-15 0.410-1260-1008-10 0.85-10755-7 Sand1500.215-3090-3004-6 0.410-1290-1803-5 0.85-10902-4 Sand2000.215-30350+3-6 0.410-12180-3002-4

21. 21 Soil typeHumid areasArid areas Bare soilGood crop cover Bare soilGood crop cover Sand0.31.0 2.0 Clay0.52.0 5.0 B3.2.1Irrigation techniques Surface irrigation: Border irrigation: Scaling

22. 22 B3.2.1Irrigation techniques Surface irrigation: Border irrigation: Problems

23. 23 B3.2.1Irrigation techniques Surface irrigation: Border irrigation: Problems

24. 24 B3.2.1Irrigation techniques Surface irrigation: Furrow irrigation

25. 25 B3.2.1Irrigation techniques Surface irrigation: Furrow irrigation

26. 26 B3.2.1Irrigation techniques Surface irrigation: Furrow irrigation

27. 27 B3.2.1Irrigation techniques Surface irrigation: Furrow irrigation

28. 28 B3.2.1Irrigation techniques Surface irrigation: Furrow irrigation

29. 29 B3.2.1Irrigation techniques Surface irrigation: Furrow irrigation: Infiltration

30. 30 B3.2.1Irrigation techniques Surface irrigation: Furrow irrigation: Scaling

31. 31 B3.2.1Irrigation techniques Surface irrigation: Furrow irrigation: Scaling Slope (%) Max stream size (l/s) Average irrigation depth (mm) ClayLoamSand 75150501001505075100 0.053.03004001202704006090150 0.13.034044018034044090120190 0.22.5370470220370470120190250 0.32.0400500280400500150220280 0.51.2400500280370470120190250 1.00.628040025030037090150220 1.50.525034022028034080120190 2.00.32202701802503006090150

32. 32 B3.2.1Irrigation techniques Surface irrigation: Furrow irrigation

33. 33 B3.2.1Irrigation techniques Surface irrigation: Furrow irrigation: problems

34. 34 B3.2.2Irrigation techniques Rainwater harvesting The collection and concentration of runoff Sits between rain-fed agriculture and traditional irrigation –Can produce a crop where none is possible with simple rain catchment Usually in arid and semi-arid areas but also suited to semi tropical Rainwater is purer than ground or surface water – salinity

35. 35 B3.2.2Irrigation techniques Rainwater harvesting:

36. 36 B3.2.2Irrigation techniques Rainwater harvesting Production costs Cash crops/income Yields Salinity hazard Reliability Rain fed agriculture Rainwater harvesting Irrigated agriculture

37. 37 B3.2.2Irrigation techniques Rainwater harvesting: limitations Climatic fluctuations –Yields cannot be guaranteed Potential up and downstream conflict (but less than “traditional” irrigation Some scientific uncertainty Large schemes difficult to implement

38. 38 B3.2.2Irrigation techniques Rainwater harvesting

39. 39 C = Catchment Ca = Cultivated area ET cr = Crop evapotranspiration P = Design rainfall k = Runoff coefficient  = Efficiency B3.2.2Irrigation techniques Rainwater harvesting: Catchment – cultivated area ratio (C:Ca)

40. 40 B3.2.2Irrigation techniques Rainwater harvesting: Efficiency

41. 41 B3.2.2Irrigation techniques Rainwater harvesting: Design Rainfall: curve

42. 42 B3.2.2Irrigation techniques Rainwater harvesting: Design Rainfall: Exceedance table JanFeb.MarAprMayJunJulAugSepOctNovDec 10%20060150250 240200 170370390300 20%1704075220200 170160150340 240 30%1601865210190 160150145310 190 40%1551160200140 120140300 160 50%12075519085110120110120290 110 60%9054717080105 96100270 105 70%6014015074100 90 250 90 80%180 1406595908055200 55 90%1604906090407240190 40 99%1200600 0 501814018

43. 43 B3.2.2Irrigation techniques Rainwater harvesting: Microcatchments Small (thus the name) 1-1000m 2 Catchment and cropping areas adjacent Crops are usually a single tree/catchment or small annual crop No overflow Small area ratio (1:1 – 10:1) Tend to be in series of units Efficiency 0.5-0.6

44. 44 B3.2.2Irrigation techniques Rainwater harvesting: Microcatchments

45. 45 B3.2.2Irrigation techniques Rainwater harvesting: Microcatchments: Negarims

46. 46 B3.2.2Irrigation techniques Rainwater harvesting: Microcatchments: Negarims

47. 47 B3.2.2Irrigation techniques Rainwater harvesting: Microcatchments: Negarims

48. 48 B3.2.2Irrigation techniques Rainwater harvesting: Microcatchments: Semi circular bunds

49. 49 B3.2.2Irrigation techniques Rainwater harvesting: Microcatchments: Semi circular bunds

50. 50 B3.2.2Irrigation techniques Rainwater harvesting: Microcatchments: Semi circular bunds

51. 51 B3.2.2Irrigation techniques Rainwater harvesting: Microcatchments: Semi circular bunds

52. 52 B3.2.2Irrigation techniques Rainwater harvesting: Microcatchments: Contour bunds

53. 53 B3.2.2Irrigation techniques Rainwater harvesting: Microcatchments: Contour bunds

54. 54 B3.2.2Irrigation techniques Rainwater harvesting: Macrocatchments Big 750-10,000m 2 Used for all types of crops Often includes overflow structures larger area ratio (10:1– 100:1) Efficiency 0.2-0.4

55. 55 B3.2.2Irrigation techniques Rainwater harvesting: Macrocatchments Stone bunds

56. 56 B3.2.2Irrigation techniques Rainwater harvesting: Macrocatchments Stone bunds

57. 57 B3.2.2Irrigation techniques Rainwater harvesting: Macrocatchments Stone bunds

58. 58 B3.2.2Irrigation techniques Rainwater harvesting: Macrocatchments: Hillside conduits

59. 59 B3.2.2Irrigation techniques Rainwater harvesting: Macrocatchments: Hillside conduits

60. 60 B3.2.2Irrigation techniques Rainwater harvesting: Macrocatchments: Hillside conduits

61. 61 B3.2.2Irrigation techniques Rainwater harvesting: Macrocatchments: Hillside conduits

62. 62 B3.2.2Irrigation techniques Rainwater harvesting: Floodwater harvesting Can be diverted to conventional-style irrigation or microcatchments Variable size Ha – km 2 Used for all types of crops Variable area ratio (1:1– 10,000:1)

63. 63 B3.2.2Irrigation techniques Rainwater harvesting: Floodwater harvesting (water spreading)

64. 64 B3.2.2Irrigation techniques Rainwater harvesting: Floodwater harvesting (water spreading)