Hubert Reeves once wrote that “on the cosmic scale, liquid water is rarer than gold”. And what is true for the universe is even truer in the Sahel, the name given to the vast, arid belt that skirts the Sahara and stretches across Africa from east to west. Since 3,000 BCE, the peoples of this region have invested tremendous effort into coming up with myriad ways to capture and control this remarkably scarce resource. Faced with the poor distribution of water across space and time, they have had to resort to intelligent, thrifty methods to make the most of even the tiniest drop.