Obtaining Recharge Coefficient Using Flow Data of Karst Spring

The recharge coefficient of karst spring system in Baziling tunnel region of Yiwan railway was studied in this paper, using groundwater regime and daily precipitation data. Tracer test were conducted to confirm the boundary of the S1 karst spring. Attenuation curve of spring was used to calculate the water changes in karst aquifer. The results show that recharge coefficient of one karst spring system is not a constant value, but a variety that influenced by the precipitation intensity and distribution. Thus when water balance model was used, the annual recharge coefficient can only be applied to access normal flow into the tunnel. But if used to access the Maximum flow into the tunnel, the flow will be much less than measured flow into the tunnel, which is a great threat to the tunnel engineering.