Method for identifying and estimating karst groundwater runoff components based on the frequency distributions of conductivity and discharge

Abstract

Identification and estimation of groundwater runoff components in karst groundwater systems to improve understanding of karst water circulation and water-rock interactions is essential for water resources assessment and development. A Gaussian mixture model is presented for identifying and estimating karst groundwater runoff components based on the frequency distributions of conductivity and discharge. Successful application of this method in the Heilongquan karst spring in South China showed that groundwater runoff components can be divided into 6-8 grades, corresponding to the grades of groundwater in karst fissures. The conductivity and discharge thresholds dividing fast and slow flow were determined to be approximately 300 μS cm-1 and 0.3 m3 s-1, respectively, with fast flow exhibiting lower conductivity and larger discharge. On an annual basis, fast flow occurred 9% of the time and accounted for 35% of total water volume. The results of the method compared favorably to that of hydrograph recession analysis. Estimation of groundwater runoff components based on frequency distributions of conductivity and discharge provides a novel alternative method for the quantitative evaluation of karst water resources.