I’m assuming for a similar reason the thing in the video is impractical?
Otherwise would having either Bouys or maybe a boat with a bunch of weights on it add to the efficiency? The rising water will lift it. Move the boat/weights/bouy out of the water reservoir
Need energy? Drain the water. Water gone? Lower the weights.
More effort than it’s worth? Potential issue being the water reservoir not filling all the way, but perhaps there are ways to engineer around it.