California has a lot of wind and solar power generation, but also has hydroelectric power generation from the colossal Hoover Dam. If operated at the same time there might be too much power during the day, when wind and solar contribute, and not enough power at night, when wind and solar do not generate electricity. Excess generated electricity cannot be stored.
The proposal is that during the day, to reduce the water level at the Hoover Dam by pumping water further upstream. This would reduce hydro-based electricity generation. At night you increase the water level, and therefore water flow, thereby increasing the hydro-based electricity generation. The net effect is to balance out the overall electricity generation capacity, using the Hoover Dam as a huge battery.
- Reduced excess electricity generation: no need to store electricity, no need to give away for free or pay others to take your excess electricity
- lake water levels upstream of the Dam would be higher during the day and lower during the night
- All equipment would be hidden from view
- lake water levels downstream would be lower during the day and higher during the night. This might affect tourism on the downstream lakes
- animals downstream may not adapt to the change in water level