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.