I have to call bs on this one. If there are really 1 million dams in the world as the article claims, that would mean on average over 50,000 dams per each of 196 counties. Consider that Wikipedia says the USA has over 75,000 dams. Considering how large and advanced the USA is, I have hard time believig a 50k average for the rest of the world. Further, the implication is that every dam has a meaningfully-sized reservoir, which cannot be the case. I imagine for the 1m dam figure, they must be counting every irrigation berm on every farm. Sounds silly to me.
Maybe they’re counting beaver dams too :)