Comparison of Shuttleworth–Wallace and Dual Crop Coefficient Method for Estimating Evapotranspiration of a Tea Field in Southeast China

Abstract

Determination of evaporation (E) and transpiration (T) in tea fields separately is important in developing precise irrigation scheduling and enhancing water use efficiency. In this study, the Shuttleworth–Wallace (S-W) model was applied to simulate the variations of E and T based on the data from 2015 to 2018 in a tea field in southeast China. The dual crop coefficient (D-K) method recommended by FAO-56 was also applied to calculate E and T, using the same data set to compare with the S-W model. The measured crop coefficient (Kc) ranged from 0.43 to 1.44 with the average value was 0.90 during 1–150 DOY (days of year), and the measured Kc tended to be stable with the average value of 0.83 during 151–365 DOY in 2015. The S-W model estimated ETc with root mean square error (RMSE) and R2 of 0.45 mm d−1 and 0.97, while for the D-K method the values were 0.61 mm d−1 and 0.95. Therefore, both approaches could estimate the E and T separately in tea fields in southeast China, however, the D-K method had a slightly poorer accuracy compared to the S-W model in the estimation of ETc.