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ESTIMATION OF EVAPOTRANSPIRATION OF KUMULUR BY PAN EVAPORATION METHOD

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Presentation on theme: "ESTIMATION OF EVAPOTRANSPIRATION OF KUMULUR BY PAN EVAPORATION METHOD"— Presentation transcript:

1 ESTIMATION OF EVAPOTRANSPIRATION OF KUMULUR BY PAN EVAPORATION METHOD
M.MANIVANNAN BTE

2 EVAPORATION PAN CLASS A EVAPORATION PAN

3 SUNKEN COLORADO PAN

4 PRINCIPLE : Installed in the field
Filled with a known quantity of water (the surface area of the pan is known and the water depth is measured) allowed to evaporate during a certain period of time (usually 24 hours). After 24 hours, the remaining quantity of water (i.e. water depth) is measured The amount of evaporation per time unit (the difference between the two measured water depths) is calculated; this is the pan evaporation: E pan (in mm/24 hours) The E pan is multiplied by a crop coefficient, Kc, to obtain the ETo.

5 FORMULA : ETo = KC × E pan ETo : reference crop evapotranspiration KC : crop coefficient E pan : pan evaporation

6 KUMULUR PAN-EVAPORIMETER DATA 1998
Month's Mean Monthly Pan Evaporation (in mm/day) January 2.8258 February 3.5821 March 4.5968 April 5.1933 May 5.3613 June 6.74 July August 4.0129 September 4.2733 October 2.7581 November 1.7133 December 1.8097

7 Table showing Kc value for cropc
Month Crop & Crop Stage Kc January Rice ( Harvest) 0.60 February Ground nut (Initial) 0.5 March Ground nut (Development) 1.15 April Ground nut (Mid –Season) May Ground nut (Late-Season) 0.6 June Sugarcane 0.75 July 0.80 August 0.85 September October 0.90 November 0.95 December 1.00

8 Calculation Table: Month Mean Monthly Pan Evaporation (in mm/day) Epan
Kc Mean Monthly Crop Evaporation Ec Evapotranspiration for month ( in mm) January 2.8258 0.60 52.56 February 3.5821 0.5 50.15 March 4.5968 1.15 163.86 April 5.1933 May 5.3613 0.6 99.72 June 6.74 0.75 5.055 151.65 July 0.80 122.64 August 4.0129 0.85 105.74 September 4.2733 108.97 October 2.7581 0.90 76.95 November 1.7133 0.95 48.83 December 1.8097 1.00 51.10 ∑ =

9 Results: Total Evapotranspiration in 1998= mm

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