It just takes a lot of water and space to make any meaningful dent in the power supply. There are hydroelectric storage facilities near Niagara falls but they p

It just takes a lot of water and space to make any meaningful dent in the power supply. There are hydroelectric storage facilities near Niagara falls but they produce something like 50MW for a very limited time. If you take for instance an elevation of 100m, to produce 1000MW of electricity it would take about 1000m^3 of water per second (before losses). In other words a pipe of a diameter of 6ft would need to need to move 20.8ft of water through it per second, which would be enough water to fill an Olympic sized swimming pool in about 2.5sec. That's 5760 pools for 4hrs of 1000MWh of electricity, not an insignificant amount of space.