Testing and Modification of Dalton's Evaporation Model

Abstract

Knowledge of the process of evaporation is a must for project planning for irrigated areas,
water requirement for basins, interstate and other litigations and international negotiations.
This study was undertaken mainly to examine the effects of different meteorological
parameters on pan evaporation and to develop suitable regression models to predict the rate
of evaporation for different periods within a particular year. The study was undertaken to test
the validity of Dalton's evaporation model for its use under the climatic condition of Udaipur
region in India. This paper summarises the test results of the study made on the basis of
regression model, original Dalton's model and the modified Dalton's model. It was fount that
the results obtained by use of the modified model were very close to the observed rate of
evaporation in the region. Variations between the estimated and observed evaporation were
found to be -26.95, -4.55, -22.22 and -23.28% for Rabi season, Summer season, Kharif
season and for the whole year respectively. As against this, when the modified model was
used, corresponding variations were found to be +1.02, +8.20, -7.93 and -4.83%
respectively. Further, the variation between the modified model predicted and observed rate
of evaporation for the Rabi season of the crop year 1992-93 was found to be +7.2%. The test
results indicated that the modified model could be used with a higher degree of accuracy in
the region.