When a child is born, its water needs for healthy growth and development are supplied initially by water in the milk it drinks and then by water intake itself. 
Children need more water than adults because they grow – Remember, each new cell that forms has to be filled up mainly with water.
The growth hormone and other water regulators drive the thirst mechanism and the body’s calls for water. Because of that children are constantly and naturally dehydrated. The process of cell expansion and division uses up a great deal of water. Read more
