The world's lights would flicker without the massive amounts of power coming from 45,000 large hydroelectric dams. In fact, hydro generation produces 16% of the world's electricity, while Norway, Canada, and Brazil are examples of countries, where hydo generates more than 50% of their electricity . http://www.earth-policy.org/data_highlights/2012/highlights29.
Norway gets 95% of its power from hydro and enjoys some of the world's cheapest electricity. Perhaps you are not impressed by that one since Norway is small.
Would knowing that Brazil gets 82%, Canada 62%, and China 15% of their electricity from hydro impress you more? It does me.
As for Uncle Sam, 7% of his electricity comes from hydropower, still the single biggest source of renewable electric power in America. In this region, significant hydro projects at existing dams are under construction in both Ohio and Pennsylvania.
Hydro generation has increased globally at 3% per year for the last 40 years. As is often the case in the modern world, China has a disproportionate impact on the rate of growth, because China has tripled its hydro production in the last 10 years.