Variations in discharge processes and runoff components between small karst watersheds and non-karst watersheds in Southern China

The differences in the underlying surface conditions and the structure of aquifers in karst watersheds and non-karst watersheds in southern China lead to different runoff generation, which results in different development and utilization values of runoff components in different water discharge processes. In order to understand the runoff generation of karst watersheds and explore the water resources evaluation methods in karst watersheds, 31 flooding events in the Miaogou karst watershed and the Gaojiaping non-karst watershed in western Hubei Province were analyzed to propose two standard recession equations. This paper compares the standard attenuation equations of two watersheds, the discharge process of typical rainfalls, and the differences in runoff components under different flood peak flows. The results show that the water discharge process in the karst watershed is faster than that in the non-karst watershed, and its attenuation coefficient is 40% larger than that of the non-karst watershed. The base flow in the two watersheds is derived from the fissure medium that is the main groundwater storage space, but the proportion of the space occupied by the fracture media in the non-karst watershed is 8.8% greater than that of the karst watershed. With the increasing flood peaks, the proportions of surface runoff increase logarithmically, while the proportion of subsurface runoff decreases logarithmically. The runoff component of the karst watershed is more sensitive to the peak flow than that of the non-karst watershed, and its surface runoff ratio ranges from 4% to 40%, while the non-karst basin is always less than 10%. This paper quantitatively evaluates the water-conducting and water-storing functions of pipelines and fractured media in the watersheds, and the research results are beneficial for explorations in further describing runoff generation in karst watersheds. The results can provide a basis for water resources evaluation and improvement of hydrological models in karst mountainous areas.