6. What are main uses that humans have for water?

Water resources are sources of water that are useful or potentially useful to humans.
Uses of water include

· agricultural,
· industrial,
· household,
· recreational and
· environmental activities.
But only some of these take the water out of the system, in other words they are consumptive For example, irrigating plants that absorb the water in order to make new plant material does, as do certain manufacturing processes. However, using the movement of water to produce electricity (hydroelectric power) and recreational fishing and sailing on a lake both need the water, but leave the water unaffected by the activity. So this is water utilization.
So it is those activities and processes that remove or change the nature of the water that need to be monitored, because, as you will see, we only have a very limited amount of the type of water we need.
This is because virtually all of these human uses require fresh water. But 97% of water on the Earth is salt water, leaving only 3% as fresh water of which slightly over two thirds is frozen in glaciers and polar ice caps.
The remaining unfrozen freshwater is mainly found as groundwater, with only a small fraction present above ground or in the air.

Fresh water is a renewable resource, yet the world's supply of clean, fresh water is steadily decreasing. Water demand already exceeds supply in many parts of the world and as the world population continues to rise, so too does the water demand.

Agricultural use
You might have been surprised that the agricultural sector is by far the biggest user of freshwater. 1.6C_Water_use_by_sector.png
However, when you seen the world map of agricultural usage, it makes a lot more sense. 1.6D_Agriculture.png
Low usage for agriculture:
· Northern and Western Europe, Canada – enough rain and/or little evaporation as it is temperate
· Gabon and DR Congo – this is rainforest, so there is not much farming and little need for irrigation
High usage for agriculture
· Southern and South-east Asia – monsoon rainfall (wet season, dry season) with a lot of rice grown – rice starts life in a flooded paddy filed
· Along the edges of Saharan Africa – need irrigation to grow anything – also most of these areas have sparse population, so the domestic need would be low and it is unlikely that there is much industry.

Industrial Use
It is estimated that 15% of worldwide water use is industrial. Major industrial users include power plants, which use water for cooling or as a power source (i.e. hydroelectric plants), ore and oil refineries, which use water in chemical processes, and manufacturing plants, which use water as a solvent.

The portion of industrial water usage that is consumptive varies widely, but as a whole is lower than agricultural use.

Water is used in power generation. Hydroelectricity is electricity obtained from hydropower. Hydroelectric power comes from water driving a water turbine connected to a generator. Hydroelectricity is a low-cost, non-polluting, renewable energy source. The energy is supplied by the sun. Heat from the sun evaporates water, which condenses as rain in higher altitudes, from where it flows down.

Water is also used in many industrial processes and machines, such as the steam turbine and heat exchanger, in addition to its use as a chemical solvent. Discharge of untreated water from industrial uses is pollution. Pollution includes discharged solutes (chemical pollution) and discharged coolant water (thermal pollution). Industry requires pure water for many applications and undertakes a variety of purification techniques both in water supply and discharge

Environmental use of water:
Explicit environmental water use is also a very small but growing percentage of total water use. Environmental water usage includes artificial wetlands, artificial lakes intended to create wildlife habitat, fish ladders around dams, and water releases from reservoirs timed to help fish spawn.

Like recreational usage, environmental usage is non-consumptive but may reduce the availability of water for other users at specific times and places. For example, water release from a reservoir to help fish spawn may not be available to farms upstream .

Household Drinking water

It is estimated that 15% of worldwide water use is for household purposes. These include drinking water, bathing, cooking, sanitation, and gardening. Basic household water requirements have been estimated at around 50 litres per person per day, excluding water for gardens. Drinking water is water that is of sufficiently high quality so that it can be consumed or used without risk of immediate or long term harm. Such water is commonly called potable water. In most developed countries, the water supplied to households, commerce and industry is all of drinking water standard even though only a very small proportion is actually consumed or used in food preparation.
However in LICs , many households do not have a water supply in their houses, and those that do often have an inadequate supply of potable water.
Where the water has to be collected from a point away from the houses, also usually have issues with sanitation, as the drinking water can easily become polluted.

Here is how most of the water is used in different parts of the world