## 4 Three-Dimensional Transient Seepage of the Hydrogeological Models
### Validation of the Inversion Model  
The natural seepage field and the simulated seepage field are shown in Figure 8. The numerical model was verified using ten identical monitoring points from Figure 8a,b that covered the water level values of features such as the engineering area, Wuyue Reservoir, and Laoshanzhai. The measured and calculated water levels of the monitoring points are shown in Figure 9a. The simulated water level was roughly consistent with the field-measured water level, and the average error of the simulated calculated water level was 1.98%. Based on the rationality of the model parameter inversion, two seepage control schemes, namely normal seepage conditions and limited seepage conditions, were designed. The normal seepage conditions included five different transient flows, with transient flows of (1) 0-200 m\({}^{3}\)/d, (2) 0-400 m\({}^{3}\)/d, (3) 0-600 m\({}^{3}\)/d, (4) 0-800 m\({}^{3}\)/d, and (5) 0-1000 m\({}^{3}\)/d. The limiting seepage conditions included three transient flows, with transient flows of (6) 0-2000 m\({}^{3}\)/d, (7) 0-4000 m\({}^{3}\)/d, and (8) 0-5000 m\({}^{3}\)/d. Three long observation holes, ZK01, ZK02, and ZK03, were set up on both sides of the tunnel axis in the project area to collect real-time, accurate information about the changes in the groundwater flow fields in the project area for a period of 2 years (Figure 4). Water level sensors (Figure 10) were installed to transmit the monitoring data in real-time and send out alarm information in time. The water levels of the natural flow fields of ZK01, ZK02, and ZK03 and the calculated water levels for the five seepage control design schemes are \begin{table}
\begin{tabular}{c c c c} \hline \hline \multirow{2}{*}{**Partition Number**} & \multicolumn{2}{c}{**The Permeability Coefficient of Principal Axis Direction (m/d)**} \\ \cline{2-4}  & \(k_{xx}\) & \(k_{yy}\) & \(k_{zz}\) \\ \hline
1 & 0.0232 & 0.0232 & 0.0232 \\
2 & 2.592 \(\times\) 10\({}^{-7}\) & 2.592 \(\times\) 10\({}^{-7}\) & 2.592 \(\times\) 10\({}^{-7}\) \\
3 & 72.0576 & 72.0576 & 72.0576 \\
4 & 8.64 \(\times\) 10\({}^{-6}\) & 8.64 \(\times\) 10\({}^{-6}\) & 8.64 \(\times\) 10\({}^{-6}\) \\
5 & 8.64 \(\times\) 10\({}^{-6}\) & 8.64 \(\times\) 10\({}^{-6}\) & 8.64 \(\times\) 10\({}^{-6}\) \\
6 & 0.0415 & 0.0415 & 0.0415 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Permeability coefficient of each layer. Figure 8: Comparison of (**a**) the natural seepage field and (**b**) the simulated seepage field. shown in Figure 10. This graph shows that the water level changes in the long observation holes fitted closely with seepage control design scheme 1. The variations in the water levels monitored in the long observation holes and calculated by the inversion model for seepage control design scheme 1 are shown in Figure 9b-d. Borehole ZK01 had a water level of 103.94 m and a simulated water level of 104.33 m, meaning a difference of 0.39 m. Borehole ZK02 had a water level of 105.88 m and a simulated water level of 106.22 m, meaning a difference of 0.34 m. Borehole ZK03 had a water level of 115.43 m and a simulated water level of 115.44 m, meaning a difference of 0.01 m. The average error between the simulated water level values and the sensor data was 0.16%, which shows that the model was satisfactory. The seepage parameters given by the inverted  
Figure 10: Water level changes in the long observation holes under different transient flows. Figure 9: Comparison of the measured water level and the calculated water level. (**(a)** is comparison of measured and calculated groundwater flow field values, (**b**) is comparison of measured and calculated water level in long-term observation hole). (**c**) is comparison of measured and calculated water level in long-term observation hole ZK02, (**d**) is comparison of measured and calculated water level in long—term observation hole ZK03.