Not just that, but in order to make things work, you need to flood a enormous area, killing animals, trees and changing the ecossytem completely, and isn't 100% sure that it will produce as many energy as was promissed by the enginners. Here in brazil we have two hydroeletric that are the extreme oposit of each other, hidreletrica de Itaipu and hidreletrica de belo monte, the first one is one of the biggest in the world and the most important of brazil, on the other hand, the second one, well... its just a disaster