Hydrologic response in a typical karst desertification catchment

Karst desertification areas exhibit high spatial heterogeneity, extensive rock exposure and systems with a complex hydrological structure. Understanding runoff generation mechanisms is important for the interpretation of hydrological processes in karst critical zones. A typical karst desertification catchment in Southwest China was selected for a 2-year hydrological observation study of rainfall events, and rainfall–runoff characteristics and hydrological responses were studied. The results showed that very high rainfall infiltration occurs in the catchment, with an average runoff coefficient of 3.6%, and the runoff coefficient during most rainfall events ranges from 0.01 to 0.05%. The rainfall–runoff process is comprehensively affected by the landform characteristics, rocky desertification environment and epikarst infiltration system in the catchment. The rocky desertification hillslopes in the upper and middle reaches of the catchment are characterized by high permeability and low water-holding capacity because of the large areas of exposed rocks and fissures, which amplify the epikarst precipitation infiltration rate. Depressions in the lower reaches result in an increase in the retention time of water in the epikarst, which exhibits low permeability and high water-holding capacity. In this study, it was revealed that antecedent hydrological conditions significantly impact runoff generation processes in catchments. Runoff in the catchment mainly comprises old water (> 50%), and continuous rainfall events lead to a gradual increase in the proportion of new water.