Pumped-storage power plants play a crucial role in energy storage, power system stability, and overall system control. However, the presence of water poses significant challenges and financial risks in underground construction projects. Beyond the process of water seepage, the distribution of stresses and hydrostatic pressures on the cavern lining must be accurately assessed so that appropriate waterproofing or drainage systems can be implemented. Therefore, accounting for water infiltration into underground spaces is a fundamental consideration in the design process.Given the importance of this issue, the present study quantifies the seepage rate and evaluates the effects of water on the cavern lining of the Azad Kurdestan Dam power plant under dry, drained, and undrained conditions. This assessment was carried out using analytical, experimental, and numerical approaches, including UDEC software.The results indicate that seepage rates obtained from analytical methods (SGR and SGRM), the TIC experimental method, and numerical modeling ranged from 3.4– 22.1, 3.4– 13.6, 18.7– 102, and 16– 36 liters per second, respectively. Moreover, integrating the numerical findings with capacity diagrams reveals that the shotcrete lining remains stable under dry and drained conditions but becomes unstable in undrained conditions due to placement the axial force in the tensile state. Consequently, the cavern support system requires an effective drainage plan.