Land Reclamation, Irrigation and Power Research Institute, Punjab, Amritsar.
Potential evapo-transpiration by Penman method has been worked out for Amritsar, utilising the climatological data observed in the past eleven years at the Meteorological Observatory, Amritsar (Raja Sansi). This has indicated that the monthly potential evapo-transpiration for this location on the average varies between 0.89 in. to 7.32 in. (2.2 cm. to 18-6 cm.). Total average potential evapo-transpiration has also been worked out for kharif and rabi and have been found to be of the order of 35.84 in. (91.1 cm.) and 12.23 in. (31.3 cm.) respectively.
Limitations in the wider application of Penman method on account of non-availability of the essential climatological data have been discussed. Two approaches have been made with a view to develop some empirical relations from which the estimation of evapo-transpiration closely agrees with that worked out by Penman method. In the first approach, potential evapo-transpiration by Penman method has been correlated with consumptive use factor whereas in the second approach, a relationship connecting potential evapo-transpiration with temperature, extra-terrestrial radiation rate and mean monthly relative humidity has been investigated. Both the relations have been found to fit the data reasonably well and as such can be employed for predicting potential evapo-transpiration.
