Rock mass permeability classification schemes to facilitate groundwater availability assessment in mountainous areas: a case study in Jhuoshuei river basin of Taiwan

This study proposes an application of the classical rock mass classification concept on the estimation of in situ hydraulic conductivity of regolith and fractured bedrock which can be utilized to evaluate groundwater potential in mountainous areas. On the basis of boring logs, borehole televiewer image data, and double packer hydraulic test data conducted in the Basin of Jhuoshuei River of central Taiwan with the aid of bivariate analysis, two rock mass permeability classification systems (Hydro-Potential value for Regolith (HPR) and Hydro-Potential value for Bedrock (HPB) System) were developed. By regression analysis, the dependence of HPB/HPR on in situ hydraulic conductivity was performed, and two empirical models for estimating in situ hydraulic conductivity were derived. Meanwhile, two derived models were validated through the comparison against results from other types of hydraulic test data (pumping and single packer tests). Therefore, the development of the empirical models for a groundwater-related project enables to help the planning of detailed investigations for the determination of hydraulic conductivity with cost-effectiveness.