the answer is fat,not water.The fat stored in the humps of camels is used as an energy reserve,Water is stored throughout their bodies,predominantly in their bloodstream,which makes them very good at avoiding dehydration,Camels can go sever days without drinking,but when they do drink,they really go for it,up to 225 liters at time! Enough to easily keep a family of four satisfied on the driest of summer afternoons.