I have been reading The Conquest of a Continent: Siberia and the Russians, a most interesting book. It has a couple of quirks that I have noticed. First, it is written in very short chapters, mostly of ten pages or fewer. Second, it has an uncritical love of numbers. The second may be hard to avoid when one is writing about Russia and comparably large places.
One can use numbers to inform or impress. This book tends use them to impress. The Bratsk dam held 200 billion cubic yards of water. Every year the Baikal-Amur Main line required four hundred tons of ballast for the roadbed, plus eleven million cubic feet of crushed rock, forty thousand tons of lime, and eighty million bricks for embankments, tunnels, and so on. This hydroelectric project was expected to provide so many kilowatts of power--how many Moscows or New Yorks is that?
The Bratsk hydroelectric station was built to produce 22 billion kilowatt hours per year, I read on page 380. On page 382, that project and several others produce 15 million kilowatt hours per day. At this point, I did a little arithmetic: 22 billion per year is about 60 million per day. How did the several dams produce a quarter of the output of one of them?
There is also no context given--what you you do with all those kilowatt hours? The UN says that household use accounts for 15 to 25 percent of energy consumption in developed countries. So taking the lower figure of 15 million per day for Bratsk, Ut-Ilinsk, and Krasnoiarsk, figure that about 3 million went to household use. At modern US levels of consumption (15 kWh per day) that would be about 200 thousand households (along with the industries and so on that employed their working members), but in the USSR at the beginning of the 1970s, presumably consumption was less--work out your factor and you can calculate on how large a population this supports.
And for the reader who wonders how much water 200 billion cubic yards is, other than "a lot", the cube root of one billion is one thousand; the cube root of 200 is a bit less than 6. So if we call it a cube six thousand yard on a side, we're in the ballpark. I haven't seen any such cubes, but I have a starting place to work with the figures--if I reduce the depth of the lake to a hundred yards, I have a factor of 60 to distribute to the other dimensions.