… Pumped storage requires two water reservoirs, one above the other. At night, water is pumped uphill to the higher reservoir, then sent back down through electricity-generating turbines when energy demand peaks or renewable resources can’t generate electricity, helping to ensure grid stability during system-stressing events like record-hot summers. … Closed loop pumped storage projects need water to work, usually by pumping aquifers or by bringing in surface water from a nearby river or lake (pumped storage can be built along a river, called open-loop, but such projects have received less support because they require dams, which have drawn fierce pushback in recent years). Here in the drought-stricken Southwest, groundwater is in short supply.