Abstract: To explore the mechanism underlying soil erosion control and crop yield increase in ridge-furrow rainwater harvesting production on sloping land in the hilly areas of the Loess Plateau, China, we modified Soil Conservation Service Curve Number (SCS-CN) model to estimate the runoff for different slopes (0°, 5°, and 10°) of micro-rainwater-harvesting-ridges. The curve number (CN) and the initial abstraction coefficient (λ) in the SCS-CN model were calibrated according to 19 rainfall-runoff events of micro-rainwater-harvesting-ridges on slopping land during April 1 to October 20 in 2019. The applicability of the SCS-CN model was evaluated using five rainfall-runoff events of micro-rainwater-harvesting-ridges on sloping land. The results showed that runoff increased and λ decreased with increasing slope. Effects of slope gradient on the parameters of CN were not obvious under natural rainfall conditions. The mean Nash-Sutcliffe efficiency was 0.83, 0.96, and 0.98 for the William Slope Correction Formula, Huang Slope Correction Formula, and optimized Huang Slope Correction Formula, while the mean relative error was 17.67%, 8.51%, and 5.84%, respectively. The optimized Huang approach calibrated the curve number (CN) and λ by considering slope gradient factor. Therefore, the simulation accuracy of the SCS-CN model for the optimized Huang approach was significantly higher than that for theapproaches of William and Huang. The performance of the SCS-CN model modified by the optimized Huang approach was acceptable for runoff estimation of micro-rainwater-harvesting ridges. Our results provide valuable information on soil erosion control and grain yield increase in the hilly areas of the Loess Plateau.

Key words: micro-rainwater-harvesting-ridge on sloping land, SCS-CN model, slope-modified approach, runoff estimation.