For centuries drought has come and gone across northern sub-Saharan Africa. In recent years, water shortages have been most severe in the Sahel—a band of semi-arid land situated just south of the Sahara Desert and stretching coast-to-coast across the continent, from Senegal and Mauritania in the west to Sudan and Eritrea in the east. Drought struck the Sahel most recently in 2012, triggering food shortages for millions of people due to crop failure and soaring food prices.