Hydrochemical variations during flood pulses in the south-west China peak cluster karst: impacts of CaCO3-H2O-CO2 interactions

High-resolution measurements of rainfall, water level, pH, conductivity, temperature and carbonate chemistry parameters of groundwater at two adjacent locations within the peak cluster karst of the Guilin Karst Experimental Site in Guangxi Province, China, were made with different types of multiparameter sonde. The data were stored using data loggers recording with 2 min or 15 min resolution. Waters from a large, perennial spring represent the exit for the aquifer’s conduit flow, and a nearby well measures water in the conduit-adjacent, fractured media. During flood pulses, the pH of the conduit flow water rises as the conductivity falls. In contrast, and at the same time, the pH of groundwater in the fractures drops, as conductivity rises. As Ca 2C and HCO3 � were the dominant (>90%) ions, we developed linear relationships (both r 2 > 0Ð91) between conductivity and those ions, respectively, and in turn