1. NUST Institute of Civil Engineering/Engr Sajjad Ahmad 1

3. Direct measurement

4. Indirect or theoretical method

6. Characteristics of hydrograph

7. Components of a hydrograph

8. Hydrograph separation

9. Unit Hydrograph

11. Above ground or surface pans

12. Floating pans

14. Wall effects such as heat exchange and ration effects are neglected

15. More accurate results

17. Error due to leakage

18. Height of vegetation around pan is critical

19. Plant leaves, seeds and debris can enter easily

21. 1.80 m in diameter and 0.55m deep

22. Edges are 0.05m above ground

23. Total depth is 0.60m

25. Dimensions are 0.90m x 0.90m and 0.45m deep

26. Rim projection from ground is 5 cm

27. Water maintained 2 inch below rim

29. 0.6m diameter

30. 0.9m deep

31. Covered with 6mm wire mesh screen

33. Placed on wooden floor

34. Easy operation and maintenance

35. Correction factors are applied

37. Gives accurate reading which are free from atmospheric effects

38. Drawbacks

39. Difficulty in measurement

40. Leakage cannot be detected

42. Energy budget approach

43. Mass transfer approach

45. The coefficient multiplier of 0.6 or greater is used to get actual reading

46. This coefficient is termed as pan coefficient

48. Horizontal movement of absorbed water is called interflow

50. Presence of vegetation

51. Type of soil

52. Storm characteristics

53. Temperature

56. Φ index

58. By infiltration method

59. By rational method

61. Barlow’s coefficient

62. Inglis’s formula

63. Lacey’s formula

64. Khosla formula

66. For flat areas

68. Catchment area ‘A’ in hectares

69. Impermeability factor ‘I’ of the catchment area

71. It varies with respect to the type of surface