Key influence of hydrogeological, geochemical, and geological structure factors on runoff characteristics in karst catchments

•Geological factors explain 27% to 56% of the variation in runoff characteristics.•Hydrogeological factors explain up to 30% of the variation in runoff characteristics.•Each geological factor not only directly but also indirectly affected the runoff characteristics. Lithology, dissolution degree, and other geological factors are essential factors affecting karst environments. However, the complex effects of multiple geologic factors on runoff characteristics have not been well quantified in karst catchments. Thus, 30 catchments and four runoff characteristics (runoff coefficient, runoff modulus, annual runoff extremes ratio, and annual runoff variation coefficient) were selected in this study to evaluate the influence of geological factors on runoff characteristics in karst catchments. The linear mixed effect model was used to quantitatively evaluate the contribution rate of each factor to the runoff characteristics, and the structural equation model was used to analyze the quantitative relationship between each factor and the runoff characteristics. The results show that among the three aspects of geological factors, hydrogeological factors have the greatest influence on runoff characteristic values. In turn, the density of sinkhole is the most influential factor among the hydrogeological factors. Geological structure factors had both direct and indirect effects on runoff characteristics (path coefficient is 0.27). Among them, the density of faults is the most influential factor. Geochemical factors affected runoff characteristics more by influencing hydrogeological factors (path coefficient −0.51) or geological structure factors (path coefficient −0.43). In conclusion, data from several watersheds directly confirm that in karst watersheds, these geological factors such as hydrogeology, geochemistry, and geological structure have a very fundamental influence on karst watershed runoff characteristics. Our results can help us further understand karst hydrological processes and improve the accuracy of karst hydrological modeling.