There is more work to be done in the next room. You can see that this horizontal wheel is not square on to its axis, so that will need sorting out. It also has no gear teeth, and it requires an especially hard wood; what the French call a Cormier; Surbus domestica, a rare tree in Europe. They were lucky - they found some at a furniture-maker's in the village, and he is making the gear teeth. Once they are in place, they will be able to turn the millstone that is upstairs.
The wooden teeth that are already in place on the vertical gearwheel are made from Robinia pseudoacacia, a hard wood that is strong enough for this application but not for the smaller wheel.
They reckon that the wheel will generate about 9 horespower, which is a bit less than 7 kilowatts. If it were up to me, I'd hook in an electric generator, back it up with solar panels in Summer in case the river gets low, and Bob's your uncle: free electricity for life.