The dam is completed, and it's already filled for production levels, the flooding of the basin has started in 2020:
https://eros.usgs.gov/earthshots/grand-ethiopian-renaissance-dam-ethiopiaIt does have only 700MW out of 5GW installed, but the trick is that the powerplant would have never produced that much, it has a capacity power below 30% so 2 turbines running full time will have the same effect as 6 installed over the year with the current debit being released.
Eventually, the dam will be completely filled with water, but for now they have to do it slowly to prevent water shortages, according to that report.
Which I can't wait for, I am sick of these thunderstorm-induced outages 
I am starting to wonder why we don't use solar power as much. Because now the weather is getting Sahara-like hot these days.