Have you actually calculated how many of those dams are needed and what the cost of building them is? On top of that you then need to build much more generating capacity as it has to provide all the power for daily usage plus additional power to pump massive amounts of water.
Great theory but at what total massive cost.
Those countries that totally rely on hydro have an abundance of natural water supply and don't pump it all uphill.
Remember a few years back when Tassie ran out of hydro capacity?
Please list each country that uses a large number of pumped hydro plants for baseload. There are none.
