Yes, hydro energy is a safe and inexpensive way to make energy. I wish it was utilized more because of the enviromental issues we are faced with today. Energy can never be taken back, it just takes different forms and continues on and on whether good energy(hydro, solar, wind) or bad energy(nucluer, oil, and so on).
You don't have to worry about hydro energy depleting because this type of energy comes water being turned into energy and everything we use goes back into the air as water vapor and that will go back into the water cycle. that's why the hoover dam uses hydro electric energy because it is a reusable resource.