On a country level I would imagine there are not that big of spikes in demand. Maybe in winter you have 3 to 4 times more flow than without storage configurations. I have trouble imagining what kind of use case would call to throttle between no water level loss to thousandfold flow.
You can’t just release most of the water stored in a hydro dam whenever you want. If you would do that you would flood the land after the dam.
On a country level I would imagine there are not that big of spikes in demand. Maybe in winter you have 3 to 4 times more flow than without storage configurations. I have trouble imagining what kind of use case would call to throttle between no water level loss to thousandfold flow.