Estimation of baseflow recession constants and effective hydraulic parameters in the karst basins of southwest China

By analysing the hydrographs of karst basin outflow, it is possible to identify aquifer characteristics and, accordingly, the main features of a karst basin. In this study, 19 basins with daily observed flow discharges during drought periods between October and April 1973–1983 were selected to analyse the master recession curve (MRC). During a drought period, the MRCs were separated into segments of fast flow exponential recession and slow flow exponential recession. Break points of the fast and slow recession segments were identified and the recession constants α were determined. Relationships between α and basin area were identified. According to the estimated baseflow recession constants, hydraulic parameters including aquifer thickness and hydraulic conductivity were estimated. Hydraulic conductivities in the near-surface epikarst aquifer are of the order 10⁻³ m s⁻¹, much larger than 10⁻⁵ m s⁻¹ in the low-permeability aquifer.