For decades, hydropower has been most common source of renewable electricity in the world. (In the US, it was passed by wind a few years ago.) Pumped hydro — large hydropower facilities in which water is pumped up and run down hill to store energy — remains the most common form of energy storage, both in the US and in the world.Even as the vast majority of media attention in the clean-energy world goes to wind and solar power, hydropower continues churning away in the background, generating and storing vast amounts of renewable energy.Hydro has a long and storied past, but does it have a future? What's going on with hydropower these days? Is there any prospect of building new dams or of finding more power in existing dams? What's going on with small hydropower, on rivers, streams, and reservoirs? And is ocean energy ever going to be a real thing?I've taken hydropower for granted for a long time, so I decided it was finally time to dig into these questions. To do so, I contacted Jennifer Garson, head of the Department of Energy’s Water Power Technologies Office (WPTO). The WPTO oversees a sprawling network of prizes and grants meant to encourage hydro and marine energy projects. I talked with Garson about the future of large dams in the US, the promise of small-scale hydro for local communities, and the uncertain future of marine energy. Get full access to Volts at www.volts.wtf/subscribe