Abstract: A coupled slope surface-subsurface flow model which can be solved by finite difference method was constructed with saturated infiltration theory, SaintVenant equation, and Richards-equation, and a series of slope runoff generation experiments under conditions of different slope grades and rain intensities were conducted in laboratory. The results showed that the simulated and observed processes of surface-subsurface flow accorded well, with the relative errors of peak time, flow duration, peak flow, and gross flow being mostly less than 10%. This precise and practicable model could be used in further studying the mechanisms of subsurface flow and in providing theoretical basis for improving rainfall-runoff watershed models.

Key words: land use, soil organic carbon, active organic carbon, non-active organic carbon, Heihe River.