## 4 Results and Discussion
### Operation Stage  
The Lowari Tunnel's natural water discharge during its operation stage occurs due to gravity at both the north and south portals. Water discharge measurements were recorded during two different periods, specifically, on 30 July 2021, in the summer, and on 1 January 2023, in the winter. During the summer period, the total water discharge rate was 10.08 L/s, with 9.3 L/s in the north portal and 0.78 L/s in the south portal. In contrast, during the winter season, the total water discharge was lower, at 6.96 L/s, with 6.20 L/s in the north portal and 0.77 L/s in the south portal. The observed seasonal variation in water discharge is due to the snow melting process. During the construction stage, shotcrete was applied to cover water seepage originating from joints and fractures in the tunnel walls, resulting in a significant reduction in water discharge. Table 3 depicts the hydrochemical analysis of the water samples collected from both the north and south portals, with measured parameters compared to the 2017 World Health Organization (WHO) standards. \begin{table}
\begin{tabular}{l l l l l} \hline \hline \multirow{2}{*}{\#} & \multirow{2}{*}{**Parameter**} & \multirow{2}{*}{**Unit**} & \multirow{2}{*}{**Concentration**} & \multicolumn{2}{l}{**Max. Permisible Limits for**} \\  & & & & **Drinking Water (WHO 2017)** \\ \hline
1 & pH & – & 5.21 & 6.5–8.5 \\
2 & EC & \(\mu\)S/cm & 100 & 1400 \\
3 & TDS & mg/L & 120 & 1000 \\
4 & Turbidity & NTU & 3 & 5 \\
5 & Ca & mg/L & 63 & 200 \\
6 & Mg & mg/L & 14 & 50 \\
7 & Na & mg/L & 3 & 200 \\
8 & K & mg/L & 1.7 & 12 \\
9 & TH & mg/L & 78 & 500 \\
10 & TA & mg/L & 30 & 500 \\
11 & NO3\({}^{-2}\) & mg/L & Nil & 10 \\
12 & SO4\({}^{-1}\) & mg/L & 4 & 250 \\
13 & Cl\({}^{-}\) & mg/L & 23 & 250 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Lowari Tunnel water chemistry during construction stage. Figure 5: Lowari Tunnel hydrological status during the construction stage: (**a**) Ground water condition; (**b**) 3 years monthly comparison of dewatering. The results of the water analysis indicate that most of the parameters examined in the south and north portals fall within the permissible ranges for drinking water according to WHO 2017 standards, except for the pH level. The pH of the water samples collected from the south portal during summer and winter was 5.22 and 5.83, respectively, indicating an acidic nature. Similarly, at the north portal, the pH of the water was measured to be 5.83 during winter, while, in summer, the pH showed a higher value of 7.51. The acidic pH of the water in the south portal may be due to the presence of dissolved carbon dioxide that can make the water taste sour. The electric conductivity, total dissolved solids, total hardness, calcium, magnesium, total alkalinity, chlorine, sodium, potassium, and sulfate concentrations are significantly higher in the north portal as compared to the south portal. This difference is attributed to the longer drainage stretch of the north portal, which is responsible for the relatively high concentration of these parameters. Figure 6a,b presents the results of the Piper diagram and the Wilcox plot, respectively, which provide a comprehensive assessment of the physicochemical characteristics of water extracted from the Lowari Tunnel. The Piper diagram is commonly used to identify water facies, which are a combination of lithology, chemical kinematics, and flow patterns [49]. The hydrochemistry of the samples showed significant variation in both seasons, with Mg being the dominant cation in the south portal during the summer season. In contrast, the north portal samples were plotted in the mixed zone, indicating a lack of dominance by any cation. For the winter season, Na + K showed dominance over other cations at the south portal, while Ca was the dominant ion at the north portal. Additionally, bicarbonate was the dominant anion in both seasons and portals. The diamond plot in the Piper diagram was used to assess the hydrochemical facies of water [50; 51].