ESTIMATION%20OF%20EVAPOTRANSPIRATION%20OF%20KUMULUR%20BY%20PAN%20EVAPORATION%20METHOD

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ESTIMATION OF EVAPOTRANSPIRATION OF KUMULUR BY
PAN EVAPORATION METHOD

• BY,
• M.MANIVANNAN
• BTE-06-017

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EVAPORATION PAN

• CLASS A EVAPORATION PAN

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• SUNKEN COLORADO PAN

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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.

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FORMULA

• ETo KC E pan
• ETo reference crop evapotranspiration
  KC crop coefficient E pan pan
  evaporation

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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 4.94516
August 4.0129
September 4.2733
October 2.7581
November 1.7133
December 1.8097
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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) 1.15
May Ground nut (Late-Season) 0.6
June Sugarcane 0.75
July Sugarcane 0.80
August Sugarcane 0.85
September Sugarcane 0.85
October Sugarcane 0.90
November Sugarcane 0.95
December Sugarcane 1.00
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Calculation Table
Month Mean Monthly Pan Evaporation (in mm/day) Epan Kc Mean Monthly Crop Evaporation (in mm/day) Ec Evapotranspiration for month ( in mm)
January 2.8258 0.60 1.69548 52.56
February 3.5821 0.5 1.79105 50.15
March 4.5968 1.15 5.28632 163.86
April 5.1933 1.15 5.972295 179.168
May 5.3613 0.6 3.21678 99.72
June 6.74 0.75 5.055 151.65
July 4.94516 0.80 3.956128 122.64
August 4.0129 0.85 3.410965 105.74
September 4.2733 0.85 3.632305 108.97
October 2.7581 0.90 2.48229 76.95
November 1.7133 0.95 1.627635 48.83
December 1.8097 1.00 1.8097 51.10
? 1216.34
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Results

• Total Evapotranspiration in 1998 1216.34 mm

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