Inter-comparison of temperature-based reference crop evapotranspiration methods

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Inter-comparison of temperature-based reference crop evapotranspiration methods

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Title: Inter-comparison of temperature-based reference crop evapotranspiration methods
Author: Jothiprakash, V; Devamane, M.G.; Sasireka, K
Abstract: This paper investigates the evaluation and possibility of recalibrating temperature-based methods for estimating reference crop evapotranspiration (ETr) at a station in Tamil Nadu. Seven temperature-based evapotranspiration methods namely Thronthwaite, Blaney-Criddle, Romanenko, Hamon, Hargreaves, Linacre, and Kharrufa methods were evaluated and compared with each other and with a standard method in estimating ETr in the selected region. All the seven methods were developed in countries other than India and hence, the empirical coefficients in the equations in each method need to be recalibrated to make them applicable to climatic conditions of the study area in India. In the present study, FAO Modified Penman method was used as the standard method for evaluation and altering the coefficients in the above temperature-based ETr methods, such that these seven methods can then be used to determine the ETr in the selected region. The evaluation was first made using the original values of the coefficients involved in each equation. All the equations were recalibrated and the coefficients in each method were calculated afresh to be appropriate to the climatic data of the study area in India. The results show that, large bias existed when the original coefficients were used for the determination of ETr. Regression equations were developed to correct the differences in magnitude of evapotranspiration. When recalibrated coefficients were substituted, all the seven methods improved the estimation of the ETr for the region. With properly recalibrated values of the coefficients, Blaney-Criddle, Thronthwaite, and Hamon methods can be recommended for estimating ETr in the study region, as far as temperature-based methods are concerned.
URI: http://dspace.library.iitb.ac.in/jspui/handle/100/14415
Date: 2007


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