The problem is, with just one hydroelectric dam, others will want it. Thus others will fight you for it, and in the process, it will be destroyed or the people that know how to maintain it will be killed.
1800s-era Hydroelectric Dams are buildable with basically nothing but very basic technology and alot of manpower.
No one would kill for them in the general case simply because other people could build it.
This isn't some SUPERMODERNTECH but a very basic one we've been exploiting for thousands of years, just the ability to convert it to electricity wasn't really possible until the 1800s.
