A Novel Approach for the Simulation of Reference Evapotranspiration and Its Partitioning

Abstract

To estimate the irrigation volume required for agriculture and improve water resources utilization efficiency, it is essential to obtain an estimate of reference evapotranspiration (ET0) and its components (e.g., reference transpiration, T0 and reference soil evaporation, E0). This study updated a soil-plant-atmosphere continuum (SPAC) evapotranspiration model and its associated components to obtain a reference-based SPAC model of reference evapotranspiration (R-SPAC), and it applied the model to an agricultural ecosystem. Model simulations of mean hourly ET0 were benchmarked against those of the Penman-Monteith method by the Food and Agriculture Organization (FAO-PM) throughout the growing season. The resulting good correlation obtained (R2 = 0.96, agreement index, I = 0.98, root-mean-square deviation (RMSD) = 0.05 mm h−1) validated the accuracy of the R-SPAC model. Sensitivity analysis was used to explore uncertainties and errors for ET0, T0, and E0 caused by input variables. The results showed that net radiation and shortwave radiation at the study site were the main drivers of ET0 for both the FAO-PM and R-SPAC models. The study showed that the proposed R-SPAC model can be used for predicting ET0 and for exploring interactions between climate, crop type, and soil in determining evapotranspiration under various future environment conditions.

Interannual dynamics and controlling factors of the ratio of actual to potential evapotranspiration across typical ecosystems within the Heihe River Basin

“…In addition, the SPAC model accounts for the stomatal control of transpiration as well as other ecophysiological processes; the model is robust. The SPAC model has been used to simulate the ET of moist grassland in Japan and typical ecosystems in the Heihe River Basin (Tong et al, 2019; Wang et al, 2021; Wang & Yamanaka, 2014), but it can also be applied to other types of ecosystems. Additional model principles and specifics can be found in Wang and Yamanaka (2014).…”

“…It solves the canopy and surface energy balance governing equations separately using the Newton–Raphson iteration scheme, which makes it more convenient for estimating AET and PET (Wang & Yamanaka, 2014). The SPAC model has been well‐validated in relevant studies (Tong et al, 2019; Wang et al, 2021).…”