The human body is made up of between 40 to 80 percent water, depending on age, sex and body type. Proper hydration is essential for vital bodily functions. How much water a person needs depends on a number of different factors, such as current temperature, overall health and amount of physical exercise. Relative to their body size, children require a significantly greater intake of liquids than adults. The German Nutrition Society recommends that 12 year olds consume 1.17 litres of water, as well as 710 ml of liquids from solid foods every day. If playing around or doing sports, particularly on hot days, a child’s hydration requirements could double.
Saskia Blank of the Ideas 2020 team answered this question.