Everybody's talking about carbon footprints. And how fossil fuels spew carbon into places where it probably should not be spewed. O.K.: We get it.

But despite all the attention directed at carbon, more and more scientists are starting to figure out that it takes so much water to create energy, and so much energy to move water, that whenever we talk about the carbon footprint of energy, we really should be talking about its water footprint as well.

That is because water and energy are linked, as the Bard said, “As two spent swimmers, that do cling together and choke their art.” And until we recognize that connection, we will not be able to figure out how to get the most from our energy and our water.

The connection between most energy and water starts with one simple fact: Except for wind and photovoltaic solar found on rooftops, most power plants big or small do one basic thing: They boil water.

That's it.

The water then makes steam, which spins a turbine, which runs a generator, which creates electricity in a way that is almost miraculous. But with that miracle comes a price: Water. Lots and lots of it.