Rogun Hydropower

Two Diversion Tunnels, named DT1 and DT2, developed in parallel with their intakes were placed shortly upstream of the pre-cofferdam on the left bank, while a third tunnel at the right bank, named DT3, is foreseen at higher elevation to complement the discharge capacity of the above-mentioned tunnels.
Two Middle Level Outlet are foreseen: MLO1 and MLO2.
MLO1 will operate during construction and is divided into two stretches. The first one is a single 15 m diameter conduit, with reinforced concrete lining, and a gates chamber. When the reservoir will reach the final operation level, the gates will definitely be closed and this portion of the tunnel will be abandoned. The second stretch includes a bifurcation that splits the tunnel into two steel lined tunnels (Left and Right) of a smaller diameter (9 m). This second portion will be used during plant operation, fed by two upper shafts, S1 and S2.
The MLO2 engages on the DT3 after the gates chamber, from a higher elevation.
There are also two further tunnels on the right bank, acting as High-Level Tunnel Spillways. They were conceived to replace the high-level orifice and surface spillways of the original project. The two tunnels with an internal diameter of 9 m, are entirely steel lined and equipped with an inlet shaft structure (named respectively S3 and S4). These spillways will discharge an exceptional flow of about Q_PMF = 9’000 m³/s. Their exceptional size and the need to cross important faults along their path make the design of these tunnels also very delicate and stimulating.