# Characteristics of Deep Groundwater Flow and Temperature in the Tertiary Pohang Area, South Korea
## 4 Results
### Groundwater Flow Characteristics  
The groundwater flow based on the temperature log data was interpreted using the 1D steady-state heat transfer solution [11; 27] and by matching the observed temperature data with appropriate types of curves, considering the lithology log and anomalies of the caliper and EC logs in the process. By matching to the most appropriate type of curve, the corresponding \(\beta\) value, groundwater flow velocity, and upward/downward flow directions were determined with the residual sum of squares (RSS), 0.008-2.013 (Table 1). The thermal conductivity values of 2.16-3.95 W/mK (Table 1) and thermal diffusivity values of 0.71-1.60 mm\({}^{2}\)/s were determined from 42 samples. One sample was taken from the basic dyke, seven samples were taken from rhyolite, and thirty-four samples were taken from sandstone/mudstone layers. The unmeasured thermal conductivity values of the dacite and crystal tuff were based on representative values in South Korea (Table 1) [52]. The determined thermal diffusivity and thermal conductivity values seem reasonable by the comparison between the reference values [53; 54; 55] (Table 2). [PERSON] [56] reported that a harmonic mean of measured thermal conductivities could appropriately consider the anisotropy of stratified formations. In this study, the harmonic means of the thermal conductivity values were applied for three or more samples of the rocks. A specific heat of water in the range of 4.18-4.19 kJ/kgK and a density in the range of 980-998 kg/m\({}^{3}\) at 22-65 \({}^{\circ}\)C were applied for the 1D steady-state heat transfer. In BH-1, upward flows occurred along the fractures with dip angles of \(-60^{\circ}\) to \(70^{\circ}\) in four sections: 358-410 m along a fracture zone of 410.3-410.7 m in the dacite and tufaceous sediment section with a flow velocity of \(-2.27\times 10^{-5}\) m/s; 488-514 m along a fracture zone of 511-514.8 m in the sandstone/mudstone with a flow velocity of \(-5.93\times 10^{-5}\) m/s; 540-566 m along a fracture zone of 523.8-569.5 m in the rhyolite, with a flow velocity of \(-7.51\times 10^{-5}\) m/s; and 890-998 m along a fracture zone of 977.2-979.2 m in the sandstone/mudstone, with a flow velocity of \(-7.86\times 10^{-6}\) m/s. Alternatively, a downward flow occurred at 586-646 m along a fault zone of 572.6-572.9 m in the rhyolite, with a dip angle of \(-50^{\circ}\) and flow velocity of \(1.09\times 10^{-4}\) m/s. In BH-2, upward flows with dip angles of \(-10^{\circ}\)-\(60^{\circ}\) occurred in four sections: 618-652 m along a highly fractured zone of 525-900 m in the rhyolite with a flow velocity of \(-5.16\times 10^{-4}\) m/s, corresponding to the EC anomaly at 655 m; 736-757 m along a highly fractured zone of 525-900 m in the basic dyke with a flow velocity of \(-1.41\times 10^{-4}\) m/s, corresponding to the EC anomaly at 762 m; 1178-1189 m along a highly fractured zone of 1155-1165 m in the sandstone/mudstone with a flow velocity of \(-5.90\times 10^{-4}\) m/s, corresponding to the EC anomaly at 1181 m; and 1287-1356 m along the fault of 1310 m in the sandstone/mudstone with a flow velocity of \(-1.97\times 10^{-5}\) m/s, corresponding to the EC anomaly at 1360 m. Downward flows with dip angles of \(-17^{\circ}\) to \(28^{\circ}\) occurred in three sections: 580-610 m along the highly fractured zone of 525-900 m in the rhyolite with a flow velocity of \(3.16\times 10^{-4}\) m/s, corresponding to the EC anomaly at 578-581 m; 955-976 m along the bedding plane in the sandstone/mudstone with a flow velocity of \(2.39\times 10^{-4}\) m/s, corresponding to the EC anomaly at 943-955 m in the sandstone/mudstone; and 1257-1273 m along a fault of 1240 m in the sandstone/mudstone with a flow velocity of \(4.69\times 10^{-4}\) m/s, corresponding to the EC anomaly at 1251 m. Figure 9 shows downward flow in the zone of 1257-1273 m with \(\beta=3.90\) (RSS = 0.031).