At the end of our visit to Foz do Iguacu we went to visit the Itaipu Dam on the Parana River between Brazil and Paraguay. The dam was built in the late ‘70s, filled in the early ‘80s, and since then has produced more power than any other plant in the world. I have been to Hoover Dam and several dams in Europe, but they are tiny compared to Itaipu. Up until the building of the Three Gorges Dam, Itaipu was the biggest dam in the world, and the Brazilians and Paraguayans are justifiably proud of it.
They offer several tours of the dam: panoramic around and over the dam, an engineering tour in which you get to go in the dam, an eco-tour of the surrounding wild lands, and a night tour, which I think is just the panoramic tour but in the dark with the dam illuminated. Unfortunately the engineering tour is limited to people 14 and older for safety reasons. I didn’t think the kids would be too thrilled to wait two hours while I toured a dam, so that one will have to wait for next time. Panoramic it was for us.
The tour started with a stop at an overlook above the spillways. It was like standing in a steady drizzle despite the fact that the spillways were about 500 meters away. It turns out that when you let water through a spillway, you have all the potential energy of the water (by definition you’re spilling water from the top of the dam) being converted into kinetic energy. If you let all that water just go into the river downstream, you’ll erode the riverbed and eventually undercut the dam. That qualifies as a Bad Thing. To avoid this they design spillways with baffles or redirection or stilling pools to remove that energy. At Itaupi this is done by something like a ski jump at the bottom of the spillway, so all those tens of thousands of liters per second drop down a 100 meter chute and then get directed up into the air. On closer inspection it turned out that all the spillways weren’t active: only the five closest of fifteen chutes were open so we only saw a third of the spillway capacity in operation.
We hopped back on the bus for a trip over the dam, which took us over the power station, up the Paraguayan side, through a tunnel under the spillways, and then back to Brazil over the top of the dam. I hadn’t fully internalized being in a double-decker bus over a dam; I’m not a huge fan of heights if I’m not in control, and that dam is tall.
Multinational projects are always fascinating because they do all sorts of weird things to get the parties to agree. To make things fair, at Itaupi, the electricity production is split 50/50 between the two countries: there are 10 generators on the Paraguayan side and 10 in Brazil. Since Paraguay is so much smaller than Brazil the Paraguaians sell most of their generated power back to Brazil. Makes sense. The interesting part is that the Paraguayan power is generated at 50 Hz but Brazil uses 60 Hz, so the Paraguayan power is generated at 50 Hz, converted to HVDC, conducted to Brazil, then converted back to 60Hz AC.
Another example: as we were driving over the dam I was wondering where the Brazilian/Paraguayan border was, and it was only when I was looking at the dam that it occurred to me that the big building at the base of the dam was probably the headquarters of the dam and that it was probably bisected by the border. Sure enough, that seems to be the case; binational projects, like siblings, require that everything is split exactly in half.
It was a good visit, and an awe-inspring visit. We had visited Igaucu Falls two days prior; the water flowing through the dam is about nine times greater that what normally goes over the falls. The only sad thing is that the creation of the dam flooded an even bigger set of waterfalls than Igaucu: up until 1982, Guaria Falls was the one of the largest sets of waterfalls by volume in the world. From the wikipedia article:
“We’re not destroying Seven Falls. We’re just going to transfer it to Itaipu Dam, whose spillway will be a substitute for [the falls’] beauty”.
The spillway was impressive, but probably not a great substitute.