Here in Michigan a lot of the dams used to produce power for small local power companies. With the growth and monopolization of power companies (we’re down to 2) they decommissions nearly all of the small dams in favor of centrally produced coal electricity.
However with modern tech the electricity can be fed into the grid from multiple sources. Also modern retrofits can produce much more power than they once did. Locally we did some digging and found that our little 180 acre lake with 10 foot of head could produce as much electricity as 6 to 10 average wind generators. With basic maintenance a small hydro plant can produce for 70 to 100 years before needing a serious overhaul.
Sedimentation is an issue but that’s happening without generators in place. Laminar flow aeration looks like one good solution. Basically its a grid of small air lines that pump tiny bubbles into the sediment near the dam to promote bacterial growth and promote decay.