Distinguishing the recharge source of karst flow by specific conductance frequency distributions (CFD): case study in Houzhai karst basin, Guizhou Province, China

The karst system is very complex because of the complicate dual processes of surface and subsurface flow in the system. Therefore, it is difficult to divide and quantify the recharge source of karst flow. Measurements of specific conductance are increasingly used for obtaining information on the structure and behavior of karst system. Decomposition of the specific conductance frequency distributions (CFD) is a quantitative method to identify recharge source types and their relative contribution to karst flow. Taken Houzhai karst water system as an example, the specific conductance frequency distributions (CFD) of three representative stations(from upstream to downstream) of the Houzhai karst system in three hydrological years was decomposed into several normally distributed populations by applying Mixture Analysis, each represents a recharge source type of karst water. The results show that the recharge types of Houzhai karst water system are slope flow, rapid crevice flow and slow crevice flow. Rapid crevice flow is the major recharge type of karst water in the Houzhai karst system. The contribution of slope flow to karst water in the upstream station is relative larger than the midstream and downstream station. Slow crevice flow contributes to the downstream karst flow more than midstream and upstream. Different hydrogeological unit shows different hydrodynamic functioning, such as the relative contribution of flow types, the flow velocity and the water storing capacity. The characteristic of groundwater flow of karst water system is affected both by hydrogeological condition and precipitation.