My parents had a cottage on Lake Agnew in Ontario which was formed by the building of the Big Eddy dam in 1929. There are 5 other smaller dams within a short distance and I know that they are all still operating and producing significant value for their owners. Several are more than 100 years old and will not be decommissioned in the foreseeable future.

http://www.renewableenergyworld.com/ugc/articles/2017/05/02/lcoe-for-hydro-projects--pick-a-number-any-number.html