Use of hydrologic time-series data for identification of hydrodynamic function and behavior in a karstic water system in China

Karst aquifers are characterized by high heterogeneity and spatial variability of hydrogeological parameters. Time-series analysis of rainfall and discharge (as input and output functions), including correlation, cross-amplitude, phase and coherency, was applied to the Houzhai karstic water system in Guizhou Province, southwest China, in order to study the function, hydrodynamic behavior and hydraulic properties of the aquifer system. Autocorrelation and cross-correlation of the variables showed that the degree of sensitivity of the system to the rainfall input signal decreased gradually from the upstream to the downstream sections, but the memorizing action increased gradually. Analysis of the phase function showed that there is a lag in the discharge response to the rainfall input signal. The lag time increased gradually from the upstream to the downstream sections, and the degree of the linearity upstream is higher than downstream. The quick-flow and slow-flow components were also divided in the cross-amplitude analysis. The results showed that about 60% of spring discharge in the upstream section was quick flow. The quick-flow component downstream reduced to only 5%. The main control factors of the karst-system response are the karst geomorphology and the inner origination structure of the karstic multi-medium.