## 4 Results and Discussion
### Operation Stage
The majority of the samples showed Ca-Mg-HCO\({}_{3}\) as the dominant hydrochemical facies, with the only exception being a sample collected from the south portal during the winter season, which was plotted in the mixing zone. It could also be inferred from the Piper diagram that weak acids exceeded strong acids in all the samples, except for one sample collected from the south portal during the winter season, where alkaline-earths were dominant in comparison to alkalis. This may indicate the meteoric nature of waters with a low residence time, mainly dominated by rock weathering [52]. \begin{table}
\begin{tabular}{l l l l l l l l} \hline \hline \multirow{2}{*}{\#} & \multirow{2}{*}{**Parameter**} & \multirow{2}{*}{**Unit**} & \multicolumn{2}{c}{**Summer**} & \multicolumn{2}{c}{**Winter**} & \multicolumn{2}{c}{**Max. Permisible Limits**} \\ \cline{3-8}  & & & **South Portal** & **North Portal** & **South Portal** & **North Portal** & **for Drinking Water** \\ \hline
1 & pH & – & 5.22 & 7.51 & 5.83 & 5.83 & 6.5–8.5 \\
2 & EC & \(\mu\)S/cm & 56 & 359 & 120 & 100 & 1400 \\
3 & TDS & mg/L & 34 & 241 & 60 & 50 & 1000 \\
4 & Turbidity & NTU & 2 & 3 & 2.13 & 3.07 & 5 \\
5 & Ca & mg/L & 17 & 87.39 & 12.9 & 70.6 & 200 \\
6 & Mg & mg/L & 14 & 33.01 & 2.3 & 3.7 & 50 \\
7 & Na & mg/L & 3.40 & 37.4 & 34.8 & 49.3 & 200 \\
8 & K & mg/L & 1.30 & 2.3 & 3.237 & 3.641 & 12 \\
9 & TH & mg/L & 31 & 120.4 & 1.86 & 0.93 & 500 \\
10 & TA & mg/L & 31.25 & 136 & 300 & 250 & 500 \\
11 & NO\({}_{3}\)\({}^{-2}\) & mg/L & Nil & Nil & Nil & Nil & 10 \\
12 & SO\({}_{4}\)\({}^{-1}\) & mg/L & 3.8 & 10.9 & 3.33 & 1.33 & 250 \\
13 & Cl\({}^{-}\) & mg/L & 12 & 30 & 47.925 & 21.3 & 250 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Lowari Tunnel water chemistry during operation stage. The Wilcox plot, a well-established tool for assessing the suitability of water for agricultural purposes based on Na% and EC, was also utilized to classify the samples extracted from the Lowari Tunnel. Excessive amounts of Na in water may adversely affect soil properties and nutrient uptake by plants. EC is a good measure of the salinity hazards posed by irrigation waters. Notably, all the samples were rated \"excellent\" according to the Wilcox plot classification [53]. This is a positive indication for farmers who require high-quality water for their crops, as it ensures that the water is not only safe but also suitable for irrigation. The results of this study align with previous research on the physicochemical properties of groundwater in mountainous regions, which have been found to be rich in species such as calcium, magnesium, and bicarbonate [54, 55]. A comparison of water parameter values between the construction and operational stages of the Lowari Tunnel for the south drive reveals no significant difference in total hardness. The value is slightly higher during the construction stage due to increased Ca concentrations (total hardness is the sum of calcium and magnesium concentrations). Electric conductivity is higher in the Lowari Tunnel's water during the construction stage. In general, conductivity decreases with increased filtration, which reduces the number of dissolved solids. The alkalinity and magnesium concentrations of the Lowari Tunnel water show only slight variation between the construction and operational stages. The nitrates were found to have the same concentration in both stages, while the concentration of sulfates was slightly higher during the construction stage than in the operational stage. These findings demonstrate the importance of understanding the relationship between geology and hydrology in tunnel construction, as well as the influence of filtration on water quality. The observations in this study align with previous research [56, 57], emphasizing the significance of this study. Based on the water discharge rate of 803,520 L/day at the north portal of the Lowari Tunnel, this study proposes that the available water supply be used to address the water scarcity challenges faced by the nearby community of Baradam.