## 5 Conclusions  
This study assessed the water quality in the Lowari Tunnel during its construction stage (2006-2009) and operation stage (2021 and 2023). The study is consistent with the current trend of using a combination of qualitative and quantitative methods to assess water ingress in tunnels. The findings have important implications for the safe and effective operation of mountain tunnels and on the use of tunnel water for domestic and agricultural purposes. The important conclusions of this study are summarized below:  
* During the construction stage, the dewatering process carried out from the Lowari Tunnel (from April 2007 to February 2009), successfully managed water ingress with average discharge of 20 L/s. Seasonal water ingress was observed, primarily during snowmelt or heavy rainfall periods. During tunnel excavation, the successful grouting of water leakage points, such as joints and fractures, with shotcrete significantly reduced water infiltration. For the recorded period, during its operation stage, the Lowari Tunnel experienced natural water discharge at both the north and south portals. The measured water discharge rates vared between summer and winter, with higher rates observed during summer (10.08 L/s) compared to winter (6.96 L/s). This seasonal variation in water discharge is attributed to the snow melting process;
* During the construction stage, all measured hydrochemical parameters were within the normal range except for a low pH value (5.21), attributed to a high concentration of CO\({}_{2}\) (14,000 ppm) inside the tunnel. In the operation stage, water analysis showed that most parameters in the south and north portals complied with WHO 2017 standards for drinking water. However, the pH levels deviated from the permissible range. The water in the south portal had acidic pH values of 5.22 (summer) and 5.83 (winter), while the north portal showed a pH of 5.83 (winter) and 7.51 (summer). The higher concentration of electric conductivity, total dissolved solids, total hardness, calcium, magnesium, total alkalinity, chlorine, sodium, potassium, and sulfate in the north portal can be attributed to its longer drainage stretch;
* Piper diagram revealed significant variation in hydrochemistry between seasons and portals. Mg was the dominant cation in the south portal during summer, while the north portal samples showed a lack of dominance by any cation. Na + K dominated in the south portal during winter, while Ca was the dominant ion in the north portal. Bicarbonate was the dominant anion in both seasons and portals. The majority of samples exhibited the Ca-Mg-HCO\({}_{3}\) hydrochemical facies, indicating the influence of rock weathering. The Wilcox plot classified all samples as \"excellent\" for agricultural purposes, ensuring the suitability of the water for irrigation without adverse effects on soil properties or plant nutrient uptake;
* These results align with previous research indicating that tunnel water is suitable for various applications, including tunnel support systems, drinking, and irrigation [60; 61];
* The difference in water quality parameters between the north and south portals is attributed to the geological and hydrological factors such as surrounding rock types and groundwater conditions [62; 63; 64; 65; 66; 67]. Thus, understanding local geological and hydrological conditions is essential for effective tunnel water resource management. **Author Contributions:** Conceptualization, J.K. and W.A. ([PERSON]); methodology, J.K.; software, J.K. and W.A. ([PERSON]); validation, J.K., W.A. ([PERSON]), IL, M.W., W.A. ([PERSON]), H.T.J. and G.K.; formal analysis, J.K. and I.u.R. ; investigation, J.K., W.A. ([PERSON]), IL, M.W., G.K. and W.A. ([PERSON]); resources, J.K., W.A. ([PERSON]) and M.W. ; data curation, J.K. and I.u.R. ; writing--original draft preparation, J.K. and W.A. ([PERSON]); writing--review and editing, J.K., W.A. ([PERSON]), M.W., [PERSON] ([PERSON]), II., G.K., G.D.B. and H.D.S. ; visualization, J.K., [PERSON] ([PERSON]), M.W., I.I. and H.T.J.