Itaipu opened the left channel of its spillway at 1:50 a.m. on Sunday the 13th to control the reservoir level after increased rainfall in the incremental basin—the group of rivers that flow directly into the plant’s lake. The operation began with a discharge of about 1,700 cubic meters per second (m³/s).
The flow was increased to 3,100 m³/s at 2:43 a.m. and could reach 3,800 m³/s during the afternoon before declining. Another measurement released during the day indicated 1,735 m³/s, showing that the flow varied as the operation progressed. The opening will remain in place as long as hydrological conditions require it.
The aim is to release excess water and keep the reservoir at a safe level. Itaipu is a “run-of-river” power plant, with relatively limited storage capacity compared with the scale of its generation. As a result, when rainfall-driven inflows exceed the volume that can be used to generate electricity or kept in the reservoir, the water is routed through the spillway.
The operation is part of the structure’s normal functioning and does not interrupt electricity supplies to Paraguay and Brazil. The spillway has three channels, 14 gates and a maximum discharge capacity of 62,200 m³/s. The reservoir extends for approximately 170 kilometers along the Paraná River and stores nearly 29 billion cubic meters of water.
The increased flow also requires monitoring water levels in the Paraná River downstream from the plant. Developments can be checked in the Itaipu Hydrological Bulletin, published on the entity’s official website. The gates will be closed depending on the reduction in inflows and the recovery of favorable hydrological conditions.