Comparison study of pan coefficient models [electronic resource].

Includes references.

How much water should be applied is still the most important question to both farmers and engineers. Simple way to estimate water requirements is to predict crop evapotranspiration "ET". Thus, this study was conducted to help farmers in estimating water requirements according to reference evapotranspiration using simple measurement from pan. Reference evapotranspiration "ET 0" is often estimated from evaporation pan data as they recently are widely available than meteorologically-based "ET 0 "estimates. Evaporation pan estimation of ETo (= Kp.Epan) reliant on determination of the pan coefficient "Kp" that depends on upwind fetch distance, wind run and relative humidity at the pan site. "Kp" estimation equations have been developed using regression techniques applied to either the table presented in FAD-56, or from the original data. The relative performance of the FAD-56 table and six different "Kp" equations are evaluated with respect to reproducing the original data table using the F AD¬ 56 table as a standard. The study was conducted on Bostan region (West Nobaria sector, Egypt). In comparing the means, standard deviations, root mean squared errors and linear regression coefficients, four of the six equations reproduced the original data table with approximately the same accuracy as the FAD-56 table. A value of 0.679 could be used as pan coefficient for estimating of "ET 0" for Bostan area. As a conclusion, a map of "Kp" for different areas in Egypt could be created to help farmers in estimating the quantity of water that should be applied.

Summary in Arabic.

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