main branch of the river was closed and on May 19, the other branch, Aña Kuá, was also closed. On June 1, 1993, the navigational ship lock was opened, and on September 2, 1994, the first hydroelectric Kaplan turbine began operation. The 20 programmed units functioned for the first time together on July 7, 1998. Construction In addition to the dam, a barrage of materials long closes both arms of the river divided by the island Jasyretâ; the hydroelectric dam is in part located over this. Both extremes are settled in the Argentine coast, in the locality of Rincón Santa María and in the Paraguayan coast, near the city of San Cosme y Damián. The artificial lake formed by the dam rises above the original level and covers . Each branch has a slope. The turbines are in the main branch, in a slope with eighteen gates that allow a maximum flow of 55,000 cubic meters per second. The other branch of the river has sixteen more gates with a capacity for another 40,000 cubic meters per second. A ship lock excavated in the basaltic layer allows passage of boats with draft up to 12 feet (3.6 m). A fish ladder, designed after the ecological studies proved that the presence of the dam inhibited the reproduction of certain migratory species of the Paraná River, especially the dorado and surubí, allows fish that swim upstream to cover the 25-meter difference to spawn in the Alto Paraná. The machine house is 70 meters high. The waterfall, currently 15 meters high, has an average volume of 8,000 cubic meters per second that pass through the turbines and produce energy continuously. For comparison, the falls of Iguazú are 70 meters high, with a volume of 1,750 cubic meters per second. Population and ecological impact The lake created by the dam displaced 40,000 people. The elevation of the water level also affected the road infrastructure and sewage of the region in a way that many studies undertaken prior to construction of the dam did not take into account ; independent research later confirmed that the census of INDEC in 1990 was altered to reduce the amount of money the Yacyreta Organization would have to pay to compensate the people displaced. Ecologically, the construction of the dam most greatly affected the environment of the region in three ways. Firstly, it altered aquatic habitats via the elevation