There are two ways in which we can classify our water use. One type is in-stream use; this includes hydroelectric power, boating and swimming, for example. While in-stream activities do not use up the water, they can degrade the water quality through pollution. The other type of water use is the withdrawal of water, and this classification includes household use, industry use, irrigation, livestock watering and thermal and nuclear power. Most withdrawals are consumptions, meaning that the activity uses the water and does not return it to the source.

The amount of water that is taken (or withdrawn) from the source is called the water intake, and the amount that is returned is called the water discharge. The difference between the water intake and the water discharge is the amount consumed.

Water intake – Water discharge = Consumption

The total amount of water that is used is called the gross water use. The difference between the gross water use and the water intake is equal to the amount of water that is recirculated. The recirculated amount is expressed as a recycling rate and is a good indicator of water efficiency.

Gross water use – Water intake = Amount recirculated (or recycling rate)
Water use can mean the amount of water used by a household or a country, or the amount used for a given task or for the production of a given quantity of some product or crop. The term "water footprint" is often used to refer to the amount of water used by an individual, community, business, or nation.

Chemical Composition of water is H2O (i.e. two hydrogen atoms + One Oxygen atom combine to form water)

Drinking water or potable water is water safe enough to be consumed by humans or used with low risk of immediate or long term harm. In most developed countries, the water supplied to households, commerce and industry meets drinking water standards, even though only a very small proportion is actually consumed or used in food preparation. Typical uses (for other than potable purposes) include toilet flushing, washing and landscape irrigation. The word potable came into English from the Late Latin potabilis meaning drinkable.