Perhaps a decade from now, if all goes smoothly, large underground pipes will connect this lake to a new reservoir, a much smaller one, built in a nearby canyon about 1100 feet higher in elevation.When the sun is high in the sky, California's abundant solar power will pump water into that upper reservoir."We have a problem if we're going to have these continuous heat waves," Kuzmich says.Kelly Catlett, director of hydropower reform at American Rivers, an environmental advocacy organization which has highlighted the environmental harm caused by dams, says that "there are good pumped storage projects, and there are not-so-good pumped storage projects."But San Diego's plan, she says, "looks like something that we could potentially support" because it uses an existing reservoir and doesn't disturb any flowing streams."