Largely true, in many places. Hydro has a few problems though when scaling: It takes lots of land, and hydro reservoirs become massive sources of biogenic methane, in some cases to the tune that building them is worse than building coal plants (!). Also, hydro is statistically far more dangerous than things like wind, solar, and nuclear. When a big dam fails, lots of people die.
I dont think you can just say Hydro is far more dangerous than nuclear. When a nuclear accident happens not only a lot of people lose their lives but the effects are felt for centuries. Lands become inhabitable, generations of people carry the burden.
You might be surprised! Contrary to popular belief, nuclear energy is among the safest forms of energy production we know. Yes, this includes short and long-term deaths from Chernobyl (50/4000), Fukushima (0/<=1), and Three Mile Island (0/0).
The "Chernobyl" of hydro, of course, was the Banqiao Dam failure, which killed up to 230,000 people. For some reason, very few people know about it, and there are no HBO specials on it. Go figure.
Considering that fossil fuel kills about 4 million people per year via air pollution, year after year, both hydro and nuclear are really safe. Nuclear net saved 1.8 million lives by 2013 (and counting). Hydro probably has a good number like that too.