Study on soil moisture variation and runoff characteristics on typical karst slope under different rainfall intensities

Rainfall intensity is an important factor in hydrological process, in order to reveal its influence on soil moisture dynamics and runoff characteristics on karst slopes, four field rainfall simulation experiments were conducted with rainfall intensities ranging from 34.8 to 136.4 mm/h, on a typical karst slope of northwest Guangxi, in southwest China. The results showed that: 1) with the increase of soil depth, the response of soil moisture to rainfall was lagging by soil layers. At different depths and slope positions, the soil moisture changed rapidly, which rapid increase during the onset of rainfall and rapid decline quickly after the rain had stopped, and returned to the original levels prior to rainfall within 24 h, indicate a low soil water storage capacity and rapid hydrological processes on karst slopes. 2) The cumulative of surface, subsurface, and epikarst runoff showed increasing trend with the increasing of rain intensity, which means that water movement transform from vertical to lateral with the increasing of rain intensity. 3) There was a significant threshold relationship between soil moisture and runoff generation, and observed hysteresis phenomenon in the relationships between soil moisture and runoff. This study revealed that rainfall intensity significantly affects near-surface hydrological processes on karst slopes, our data contribute to a more comprehensive understanding of water cycle in karst critical zone.