Itaipu Closes Spillway After 10 Days of Discharge

The binational Itaipu plant closed the spillway gates on Tuesday, September 22, because of a reduction in the flow reaching the reservoir. The pause will be temporary: the plant expects to reopen the gates over the weekend, after several days of discharges that reached 6,000 cubic meters per second.

The closure occurred around 10:30 a.m., when technicians detected a progressive decrease in the inflow. The decision marked a change from the scheme implemented in recent days, when the spillway remained operational to control the reservoir level amid the strong water influx caused by rains recorded in the basin.

The spillway operation began at 1:50 a.m. on Sunday, September 13, when Itaipu opened the left spillway chute with an initial discharge of 1,735 cubic meters per second, due to increased water inflows. During the two weeks of operation, the volume of water released varied according to hydrological conditions and the power generation needs of the plant.

According to Itaipu, the chutes recorded discharges of up to 6,000 cubic meters per second. The spillway behavior was also conditioned by energy generation, as the Itaipu hydroelectric plant is a “run-of-river” type, with relatively limited storage capacity.

For the province of Misiones in Argentina, Itaipu’s behavior is closely monitored for its impact on the Paraná River. The water released by the spillway enters the bed below the plant and continues southward, also feeding the Yacyretá Hydroelectric System.

When the spillway was opened on September 13, it was warned that the increase in Itaipu’s flow did not, by itself, imply an extraordinary rise in Misiones territory, as the evolution of the Paraná depends on the flow already carried by the river, the inflows of its tributaries, and the basin’s rainfall.

Today’s temporary closure represents a reduction of one of the additional inflows that were incorporated into the Paraná in recent days. The situation will continue to depend on the evolution of water inflows in the basin and weather conditions.

The regional scenario remains linked not only to Itaipu’s operation but also to rainfall and the behavior of the basin’s tributaries.

— MisionesOnline