Rainfall, evaporation and runoff responses to hillslope aspect in the Shenchong Basin

Daily rainfall measurements and microclimatological theory are employed to construct a model of net rainfall, evaporation and surface runoff from north- and south-facing hillslopes in a small basin where soil erosion research was conducted. Soil erosion studies in the area suggest a connection between slope aspect and land use which is simulated from the model. The forest is first changed to low vegetation, then bare ground. The greatest amounts of rainfall are received on the south-facing slope, but the proportion which is kept as net rainfall increases at each stage of the sequence. The change from forest to low vegetation increases evaporation, especially on the south-facing slope where winter soil moisture content is predicted to be lower than those of the north-facing slopes. The removal of vegetation to expose bare ground reduces the evaporation but increases surface runoff, particularly on the south-facing slope where severe soil erosion occurs most frequently. This suggests that effective land management requires land use practices which maintain a vegetation cover.