Is that true? I thought the released water flows through a turbine and spins it and generates electricity?
Sounds like I have misunderstood hydroelectric? Can you point me towards resources to better understand that?
I can: https://pmm.nasa.gov/education/water-cycle
A hydroelectric plant consists of a generator connected to an energy storage device even though it may be called, for instance, “Lake Mead”. Without sufficient rain and snowmelt, there’s nothing to go through the turbines. Energy from the sun drives the water cycle.
Hydroelectric generation is actually a form of solar power attributed to the water cycle. Other than very minimal amounts of steam released into the atmosphere from geothermal and nuclear reaction, all rain that falls is due to the suns thermal effects.
You have to think further back in the cycle. The sun evaporates the ocean water forming the rain in the hills and mountains flowing to the rivers. The water behind the dams is the energy storage. So it is renewable in the long run.
The full hydro cycle....solar energy evaporates water from the ocean. Water condenses and falls as rain somewhere in the "watershed" that feeds the river that feeds the dam.
The sun is the energy source. The watershed and river are the collectors. The turbine is only what converts the weight of falling water into electricity.
Actually they do use Hydro as a storage device by pumping water into a storage basin usually called a pump back station. They pump into storage when demand is low and electric is cheap then release it back when the demand is high. Technically that makes it a storage device but it costs more to pump the basin full than it gains back when it is released. The only thing that makes it possible is the hydro damn produces power whether it is used or not.