The spillway at the Itaipu Hydroelectric Power Plant will remain open this weekend and could continue operating next week, depending on hydrological and power-generation forecasts. The Operations Superintendency, which is part of Itaipu Binacional’s Technical Directorate, said the situation could change according to rainfall in the relevant hydrological area.
The planned opening began at 1:50 a.m. on September 13, after the reservoir level rose because of rainfall at plants upstream and conditions affecting demand from interconnected power systems. Discharge increased from 1,735 m³/s, at the start of operations through the left channel, to about 2,800 m³/s by Thursday—an increase of 61%.
The maneuver is intended to keep the reservoir close to the normal maximum operating limit of 220.50 meters above sea level while inflows are monitored daily. The initial expectation was that the gates would remain open for approximately 10 days, Silver Guerrero, Itaipu’s superintendent of operations, said in an interview with Radio Nacional on September 14.
Guerrero said the wet season, normally expected between October and November, began earlier than forecast, with water volumes above usual levels since the end of August. He also pointed to a possible influence from the El Niño phenomenon and said inflows had already exceeded the reservoir’s generation and storage capacity.
Operations alternated between the left and right channels to regulate flow. According to the System Operations Division, the change to the right channel on September 14 and 16 took place because it was necessary to reduce spillage, and the minimum flow possible through the left channel was higher than the volume that needed to be released at that time. Technicians described the procedure as routine. When generation can be increased, excess water can be used and the volume discharged through the spillway reduced.
Itaipu said the operation poses no risk to riverside populations downstream. Guerrero, however, said the impact was minimal “for now.” He also said generation remained normal, without affecting supply to the Paraguayan state-owned National Electricity Administration (ANDE) or Brazil’s power system. The released water flows along the Paraná River to Yacyretá.
Because it is a run-of-river plant with limited storage capacity, Itaipu must manage its spillway more frequently when flows increase. The spillway can be viewed from the Right Bank Lookout, included in tours operated by the Itaipu Tourist Complex. Visits take place daily by appointment at 8 a.m., 9 a.m., 10 a.m., 10:30 a.m., 1:10 p.m., 2 p.m. and 2:30 p.m.
Reservations can be made by calling 061-5998040 or 061-5998094 or by emailing [email protected]. Visitors must report to the Visitor Reception Center in Hernandarias, where buses depart for the plant. Downstream river levels are published in Itaipu’s Hydrological Bulletin.