Human requirement for water

The human body is 60% water. The required daily intake to maintain life and health is about 2.25litres, or 1 litre per day just to stay alive. Household use, which includes washing, food preparation and cooking, waste disposal and sewage, but not garden use, varies greatly according to availability and cultural expectation. In Karachi it is around 90litres per day, in London 435litres, 635litres in the USA and 170litres in Adelaide (or 62,000litres per year).

Crop production opportunities increase dramatically as access to water improves. For instance it takes nearly 500litres of water to produce 1 kg of dry, non-irrigated wheat, 16000- 2,200litres to produce 1 kg of rice and 4,000litres to produce 1 litre of milk.

A pig with a body weight of 60 kg requires 25 litres of water per day and a lactating Jersey cow requires 45 litres per day to produce 3-12 kg of milk. A sheep on very good pasture needs hardly any water, but on dry range needs between 3 and 6 litres per day, or 8 litres if it is eating salty browse.

A large paper mill uses as much water as a city of 50,000 people and a power station uses 600 tonnes of water for every tonne of coal burnt.