Abstract
The discharge rate and electrical conductivity of seepage water into a mountain tunnel were monitored continuously for approximately five years in Yura, Wakayama.The chemical composition of that water was measured regularly. The mountain is composed of fractured sedimentary rocks. Based on the assumption about the presence of two infiltration components (fissure flow and matrix flow) in the rock base, variations in the water quality during heavy rainfall events and after an earthquake were analysed. Also, it was suggested that CO2-gas in the rock base plays an important role in the water quality.
