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

3. Factors influencing precipitation formation

4. Precipitation classification based on lifting mechanism

5. Measurement of precipitation

11. X-axis ≈ Average accumulated precipitation of nearby stations

12. Y-axis ≈ Accumulated precipitation of the station under consideration

14. Determine cumulative rain fall of the subjected station and of the nearby stations

15. Draw double mass curve

16. Part of the curve which lies in straight line requires no correction

18. To determine correction factor calculate the slope of the curve before and after the point of deviation

20. Po =Observed precipitation

21. Sa =Slope prior to the break in the curve

22. So =Slope after the break in the curve

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27. Consistency of the record at station ‘A’

28. Indicate the year in which there is a regime changes

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32. Draw curve of cumulative rainfall

33. Determine point of deviation

34. Calculate slope before and after deviation

35. Apply correction to the points lying after the deviation

37. Thiessen Polygon Method

38. Distance weighting

39. Isohyetal Method

41. If P1, P2, P3, … Pn etc are the precipitation or rainfall values measured at ‘n’ gauge stations, then

43. Find average precipitation

45. It is also called Weighted Mean Method

47. Connect all gauging stations

50. Calculate average precipitation

53. An isohyetal map shows contours of equal rainfall on the ground

54. Gives more accurate picture of rainfall distribution

56. Indicate points of rain gauges

57. Write rainfall value at gauge points

58. Draw isohyets

59. Measure area enclosed or b/w every two isohyets