Looking for the most cost-effective path provides one set of answers; including the need to curtail greenhouse-gas emissions gives a different picture. Adding the need to address looming shortages of fresh water, it turns out, leads to a very different set of choices. That’s one conclusion of a new study led by Mort Webster, an associate professor of engineering systems at MIT, published in the journal Nature Climate Change ("Water–CO2 trade-offs in electricity generation planning"). The study, he says, makes clear that it is crucial to examine these needs together before making decisions about investments in new energy infrastructure, where choices made today could continue to affect the water and energy landscape for decades to come.