In intake mode, the primary concerns are preventing sediment ingress into the waterways and mitigating vortex formation. Sediment intrusion can lead to erosion, blockage, and reduced turbine efficiency, while vortex formation can lead to entrainment of air, ice, or debris, pressure fluctuations, and potential risk of cavitation. • In outlet mode, key challenges include managing high velocities at the rack section, minimizing head losses, and ensuring proper jet diffusion to avoid local erosion and slope stability. 1 | Introduction Inlet and outlet structures in pumped-storage hydroelectric systems (PSH) serve a dual function, alternately acting for the lower reservoir as an inlet during pumping and an outlet during generation and conversely for the upper reservoir. In some particular configurations, two neighbouring structures can even work in opposite flow directions. This bidirectional flow condition presents several hydraulic challenges that can impact efficiency and structural integrity. Optimizing the design is critical to ensure smooth transitions between functions, minimize energy losses, and prevent problems such as cavitation, vibration, debris entrainment, abrasion of hydraulic machinery, sediment intrusion, and localized erosion in the vicinity of the structures. Guidelines published by relevant industry associations provide recommendations for the design of hydropower intakes, focusing on both hydraulic and structural considerations 1. Recent regulations have expanded to include environmental design principles, emphasizing the protection of fish, wildlife, recreational opportunities, and overall environmental quality. Despite these additional measures, maintaining maximum PSH efficiency and security remains a priority.