Yacyretá-Apipé Falls

The Yacyretá-Apipé Falls (from the Guarani Jasy retã, "land of the Moon") were a region of rapids and small waterfalls that interrupted the navigability of the Paraná River at the height of the city of Ayolas in Paraguay and Ituzaingó in the province of Corrientes, Argentina. Today they are submerged in the 1600 km² artificial lake produced by the works of the Yacyretá hydroelectric dam, which was located precisely there due to the difference in river level that originated the rapids.

The Paraná river, after receiving the Iguazú on the border between Brazil, Paraguay and Argentina, modifies its north-south course to progressively orient itself towards the west; in this zone, its bed is excavated on a porous basalt substratum that presents important fractures in several points. The largest of these faults diagonally cuts the entire province of Corrientes; it intersects the bed of the Paraná some 90 kilometers downriver from the city of Posadas with a basaltic wall of considerable thickness.

It is speculated that the presence of this wall once diverted the course of the river, taking it in a southeasterly direction through the shallows that today make up the Iberá system. Erosion eventually opened a gap in the stone, however, giving rise to low jumps. The subsequent course of the river is regular, over a fundamentally sandy alluvial bed, and consequently wider. The last stone spurs formed the islands of Yacyretá, Apipé Grande and Talavera. The current dam facilities have completely submerged the latter, as well as 80% of the former.

The Yacyretá-Apipé waterfalls constituted the first major obstacle to the navigation of the Paraná upstream, since from its mouth to this point the whole of it is easily navigable. Sebastián Gaboto had to stop his exploratory journey in 1527 when he came across them, and it was not until Commodore Thomas Jefferson Page crossed them aboard the steamer Alpha in 1860 that it was verified that it was possible to cross them in the opposite direction. falling. With the construction of the dam, a lock was also designed that allows crossing the 24-meter drop between the upper and lower part of the river course.