## 3 Study Area and Data Used  
Taiwan's orogenic movement is developed due to the mutual extrusion of the Eurasian Plate and the Philippine Sea Plate, resulting in a large mountain area in Taiwan. The mountainous area accounts for about 70% of the total area of Taiwan. Complex fracture network systems can be found everywhere in the mountain's rock formations. In this study, the central and southern mountainous areas of Taiwan were selected as the area for data collection and testing of the proposed method. Figure 1 shows the locations of this study area and geologic boreholes that produced the raw data for this research. The lithology of each geological borehole is also presented in Figure 1 ([PERSON] et al., 2018). The geological environment of the study area is highly variable and covers a wide range of stratigraphic ages, from Eocene strata to modern alluvium. The stratigraphic age is gradually younger from east to west of Taiwan. According to the lithology data of the boreholes, the main lithology types include sandstone, mudstone, shale, volcanic agglomerate, sandstone interbedded with shale, quartzite, argillite, schist, marble, slate, gneiss, and schist. The prevalent lithologies from east to west are metamorphic rock, sedimentary rock, semi-consolidated rock, and alluvial deposits in the order. Most of the strata in the mountainous area are composed of regolith layers and underlying fractured rock masses. The upper regolith porous media and underlying bedrock fractures are mostly interconnected to create unconfined aquifer systems in the study area. Fracture network properties in the fractured bedrock layers dominate their groundwater flow behaviors. \begin{table}
\begin{tabular}{c c} \hline \hline
**Material** & **S\(\mathbf{s}\) (m\({}^{-1}\))** \\ \hline Plastic clay & \(2.56\times 10^{-3}\sim 2.03\times 10^{-2}\) \\ Stiff clay & \(1.28\times 10^{-3}\sim 2.56\times 10^{-3}\) \\ Medium hard clay & \(9.18\times 10^{-4}\sim 12.8\times 10^{-3}\) \\ Loose sand & \(4.92\times 10^{-4}\sim 1.02\times 10^{-3}\) \\ Dense sand & \(1.28\times 10^{-4}\sim 2.03\times 10^{-4}\) \\ Dense sandy gravel & \(4.92\times 10^{-5}\sim 1.02\times 10^{-4}\) \\
**Rock, fissured** & \(\mathbf{3.28\times 10^{-6}}\sim 6.90\times 10^{-5}\) \\ \hline Rock, sound & \(<\)**3.28\(\times\) 10\({}^{-6}\)** \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Specific storage for different materials ([PERSON] et al., 2018). \begin{table}
\begin{tabular}{c c} \hline \hline
**Material** & **Compressibility, \(\mathbf{\alpha}\) (m\({}^{2}\)/N or Pa\({}^{-1}\))** \\ \hline Clay & \(1.0\times 10^{-8}\) to \(1.0\times 10^{-6}\) \\ Sand & \(1.0\times 10^{-9}\) to \(1.0\times 10^{-7}\) \\ Gravel & \(1.0\times 10^{-10}\) to \(1.0\times 10^{-8}\) \\ Jointed rock & \(1.0\times 10^{-10}\) to \(1.0\times 10^{-8}\) \\
**Sound rock** & \(\mathbf{1.0\times 10^{-11}}\) to \(1.0\times 10^{-9}\) \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Compressibility for different aquifer materials ([PERSON] et al., 2018). Field investigation results of hydraulic conductivity from major geological formations indicated the hydraulic conductivity ranged from the magnitudes between \(10^{-4}\) and \(10^{-10}\) m/s. The variability of hydraulic conductivity is great, but the characteristics of fractures are the most critical factors in controlling the hydraulic conductivity of the formation. Borehole image data from borehole televiewers showed that the fracture network density  
Figure 1: Locations of the study area and geologic boreholes [30; 31; 53]. for some of the metamorphic rocks are denser than that for sedimentary rocks, and the hydraulic conductivity of the metamorphic rocks has a tendency to be higher. In addition, the proportion of highly permeable sections (hydraulic conductivity is greater than 1.0 \(\times\) 10\({}^{-5}\) m/s) in each river basin showed that the proportion ranged from 7% to 30%, with considerable variation.