Considering the differences in regional climate and geography, scholars have successively proposed various empirical formulas based on Budyko's theory. Previous studies have shown that the hydrothermal coupling balance equation considering the characteristic parameters of the underlying surface can simulate the annual runoff in various catchments in China (Xing et al. 2018) (Table 2). In this study, the Fu Baopu formula (Table 2) was used for analysis and calculation (Fu 1981).
Table 2
Hydrothermal coupled equilibrium equation based on Budyko hypothesis
| Method | Formula |
|---|---|
| Choudhury-Yang |  |
| Fu |  |
| Zhang |  |
| Wang-Tang |  |
| Method | Formula |
|---|---|
| Choudhury-Yang | |
| Fu | |
| Zhang | |
| Wang-Tang | |
Note: The underlying surface parameter (n) reflects the watershed characteristics and is a function of vegetation type, soil properties, and topographical characteristics.