Adaptivity of Budyko Hypothesis in Evaluating Interannual Variability of Watershed Water Balance in Northern China: Fid-Bau Portal

Adaptivity of Budyko Hypothesis in Evaluating Interannual Variability of Watershed Water Balance in Northern China

Yu, Zhongbo / Cai, Huiyi / Yang, Chuanguo / Ju, Qin / Liu, Di / Sun, Aili

This study evaluates the performance of three Budyko-type equations (Fu’s equation, Turc-Pike’s equation, and Milly’s equation) in modeling annual evapotranspiration in 32 watersheds covering both humid and arid regions in Northern China. Daily meteorological data and monthly runoff data are used to calculate potential and actual evapotranspirations in the 32 watersheds. The results show that the Budyko-type equations are adaptive in predicting annual evapotranspiration over most of the watersheds, and Fu’s and Turc-Pike’s equations perform better than Milly’s. In addition, the validity of the framework by Koster and Suarez in predicting the evapotranspiration deviation ratio (EDR) (i.e., the ratio of the standard deviation of evapotranspiration to the standard deviation of rainfall) based on Fu’s and Ture-Pike’s equations is also examined. Given the unexpected Nash–Sutcliffe efficiency values ( $- 0.915$ and $- 1.026$ in Fu’s and Ture-Pike’s, respectively), a linear one-variable model is employed to improve the accuracy of the EDR estimation. Two revised EDR estimation equations are developed in two cases: one includes and the other excludes the three humid watersheds on the basis of the original framework. The results show that the first revised equation may be applied to both humid and arid watersheds, whereas the second revised equation is more appropriate in calculating the EDR for arid watersheds.