Wadis in the central part of Chad are dry nine months of the year. During that time, villagers must dig down to the water, shoring up the wells with millet stalks to keep them from collapsing. In the morning, the wadis are furiously active. One after another, teams of two or three girls fill the pools as wave after wave of animals come to drink. It's hard work: the water rapidly evaporates, sinks into the sand, and vanishes down the animals, and the girls have to keep refilling the pools. Hungry Planet: What the World Eats (p. 71).