The floods, droughts, heatwaves, and fires that are devastating many parts of the world underscore two fundamental facts. First, damage to freshwater supplies is increasingly straining human societies, especially the poor, with far-reaching implications for economic, social, and political stability. Second, the combined impact of today’s extreme conditions are unprecedented in human history, and are overwhelming policymakers’ ability to respond. In East Africa, a devastating four-year drought has destroyed millions of livelihoods and left more than 20 million people at risk of starvation. In Pakistan, recent flooding has submerged one-third of the country, killing at least 1,500 people so far and wiping out 45% of this year’s crops. In China, an unprecedented heatwave has caused acute water shortages in regions that account for one-third of the country’s rice production. Moreover, droughts and fires in the United Stat